Applications of nanozymes in the diagnosis and treatment of gastrointestinal malignancies

Abstract

The incidence rate and mortality of gastrointestinal (GI) malignancies such as gastric cancer and colorectal cancer continue to rise, which has become one of the important causes of cancer related deaths worldwide. Most patients are diagnosed at an advanced stage and have limited follow-up treatment options, resulting in a poor prognosis. Therefore, early diagnosis and intervention are crucial for controlling the development of diseases. Nanozymes have become a promising diagnostic and therapeutic tool due to their multi enzyme catalytic properties, showing broad application prospects in the field of GI malignancies. This article systematically reviews the mechanisms, functions, and application progress of various nanozymes in the diagnosis and treatment of this type of tumor, aiming to promote their translation from experimental research to clinical practice and provide new strategies for the diagnosis and treatment of GI malignancies.

Key Words: Nanozymes; Diagnosis; Treatment; Gastric cancer; Colorectal cancer

Core Tip: Nanozymes, with their enzyme-mimicking catalytic activity, have demonstrated high sensitivity and stability in tumor marker detection, molecular imaging diagnosis, and pathological staining. Additionally, they achieve synergistic therapy for gastrointestinal (GI) malignancies through the generation of reactive oxygen species, regulation of the immune microenvironment, and as multifunctional drug carriers. Despite challenges remaining in biosafety, targeting, and clinical translation, they offer a new strategy for the early diagnosis and precise treatment of GI malignancies.

INTRODUCTION

Gastrointestinal (GI) malignant tumors refer to various types of cancer that occur in the human digestive tract, with malignant biological behavior, and are one of the main types of cancer that threaten human health worldwide[1,2]. Due to the atypical early symptoms, which are easily overlooked, most patients often progress to the middle and late stages when obvious clinical symptoms appear[3,4]. Therefore, early screening, diagnosis, and treatment are crucial for improving cure and survival rates.

At present, GI endoscopy biopsy is considered the gold standard for diagnosing GI malignancies[5,6], but its strong invasiveness and high cost, it is difficult to use as a routine screening method for large-scale populations. Non-invasive methods such as urea breath test and imaging examination face limitations in sensitivity[7,8]. Therefore, there is an urgent need to develop non-invasive, low-cost, highly sensitive, highly specific, and dynamically monitored detection methods to achieve efficient screening and identification of the risk of GI malignancies in large-scale populations.

A promising frontier addressing these clinical bottlenecks lies at the intersection of nanotechnology and oncology. The field of nanozymology was inaugurated in 2007 when Yan et al identified the intrinsic peroxidase (POD)-like activity of magnetite (Fe₃O₄) nanoparticles[9], effectively bridging the gap between nanotechnology and enzymology. Nanozymes are defined as nanomaterials with biomimetic catalytic activities that follow Michaelis-Menten kinetics[10,11].

Over the past two decades, the repertoire of nanozymes has expanded significantly, encompassing noble metals and alloys (e.g., Au, Pt, Pd, and Ru)[12], transition metal oxides (e.g., Fe₃O₄, CeO₂, MnO₂)[13], carbon-based nanomaterials (e.g., graphene, carbon dots), and metal-organic frameworks (MOFs)[13,14]. These nanomaterials can mimic the activities of various natural enzymes, including POD, oxidase (OXD), catalase (CAT), and superoxide dismutase (SOD)[10,15].

To fully recognize the transformation potential of these nanomaterials, we conducted a comparison between natural enzymes and nanozymes (Table 1). While natural enzymes remain the evolutionary gold standard for biological catalysis owing to their exquisite substrate specificity and high turnover rates, their clinical utility in oncology is severely restricted. They are highly susceptible to denaturation under temperature fluctuations, proteolytic degradation, and the extreme pH gradients characteristic of the GI tract[16]. In contrast, nanozymes offer a highly robust alternative characterized by superior structural stability, facile large-scale synthesis, and highly tunable, microenvironment-responsive catalytic activities[16-18]. Although nanozymes generally exhibit lower substrate specificity than their natural counterparts, this broad-spectrum catalytic nature is frequently a therapeutic advantage in oncology[19]. This multi-catalytic capability enables them to simultaneously modulate multiple pathological driving forces - such as mitigating tumor hypoxia, neutralizing excess reactive oxygen species (ROS), and reversing immunosuppression - within the heterogeneous tumor microenvironment (TME) of GI malignancies[20,21]. Consequently, the clinical value of nanozymes lies not in replacing natural enzymes, but in providing a durable, multifunctional catalytic platform that operates efficiently in hostile physiological and pathological microenvironments where natural enzymes would rapidly fail.

Table 1 Comparative analysis of natural enzymes and nanozymes.

Feature	Natural enzymes	Nanozymes	GI oncology relevance	Ref.
Composition	Proteins or RNA	Metals, metal oxides, carbon, etc	Nanozymes possess a high density of active sites	[22]
Selectivity	High substrate specificity	Broad-spectrum/low specificity	Beneficial for multi-target TME modulation	[19]
Stability	Low (susceptible to protease, heat)	Extremely high (chemically robust)	Resists gastric acid and proteolytic enzymes in GI tract	[19]
Catalytic activity	High turnover rate (Kcat)	Tunable, pH/light/H2O2 responsive	Allows selective activation in acidic TME	[23]
Production cost	High (complex preparation/purification)	Low (facile chemical synthesis)	Enables large-scale clinical translate/screening	[24]
Multifunctionality	Single catalytic function	Integration with imaging/therapy	Facilitates theranostics (diagnosis + therapy)	[25]

TME: Tumor microenvironment; GI: Gastrointestinal.

To provide a holistic conceptual framework of these advanced catalytic platforms, Figure 1 systematically illustrates the classification[10,11], biomimetic activities[22], and theranostic applications of nanozymes specifically tailored for GI oncology. Structurally, nanozymes are broadly classified into metallic and non-metallic systems[12-14], each offering unique customizable surfaces and electronic configurations (Figure 1A). Upon encountering the heterogeneous TME, these nanomaterials mimic key antioxidant and oxidative enzymes - predominantly POD, OXD, CAT, and SOD[10,15] - to orchestrate localized biochemical cascades (Figure 1B). By leveraging these catalytic mechanisms, nanozymes function as versatile agents that bridge the diagnostic-therapeutic divide. They enable high-sensitivity biosensing and contrast-enhanced multimodal imaging, alongside driving tumor-targeted ROS generation, alleviating hypoxia, and synergizing with conventional and emerging oncotherapy modalities[23-25] (Figure 1C).

Figure 1 Schematic illustration of the classification, biomimetic catalytic activities, and theranostic applications of nanozymes in gastrointestinal malignancies. A: Classification: Nanozymes are categorized into metallic (e.g., iron-, manganese-, and noble metal-based systems) and non-metallic (e.g., carbon quantum dots, black phosphorus, and graphdiyne) classes; B: Catalytic pathways: The four primary biomimetic activities - peroxidase, oxidase, catalase, and superoxide dismutase - mediate key biochemical cascades within the tumor microenvironment to modulate intracellular oxidative stress; C: Theranostic applications: In cancer diagnostics, nanozymes power surface-enhanced Raman scattering/colorimetric biosensing assays and serve as contrast agents for multimodal imaging (magnetic resonance imaging, photoacoustic imaging, and fluorescence imaging). In therapeutics, they mediate tumor cell death pathways (apoptosis, ferroptosis) via toxic reactive oxygen species generation, alleviate hypoxia through in situ oxygenation, and synergize with photothermal therapy, photodynamic therapy, starvation therapy, and immune checkpoint blockade therapies. CQDs: Carbon quantum dots; CNTs: Carbon nanotubes; BP: Black phosphorus; BN-GDY: Boron graphdiyne; ROS: Reactive oxygen species; SERS: Surface-enhanced Raman scattering; MRI: Magnetic resonance imaging; CDT: Chemodynamic therapy; PTT: Photothermal therapy; PDT: Photodynamic therapy; NIR: Near-infrared; TME: Tumor microenvironment; ICD: Immunogenic cell death.

DISCUSSION

Application of nanozymes in the diagnosis of GI malignant tumors

Detection of GI malignant tumor markers based on Nanozymes: Tumor markers frequently exhibit abnormal expression during carcinogenesis; consequently, nanozymes have shown distinct advantages in their detection due to their high catalytic activity and robust stability. However, translating these nanosensors into routine clinical diagnostics demands rigorous evaluation of their analytical validation, reproducibility, and matrix compatibility. Zhuang et al[26] reported a catalytic hairpin assembly (CHA)-driven, nanozyme-based surface-enhanced Raman scattering (SERS) bifunctional sensing system. This platform utilizes the POD-like activity of platinum-coated gold nanorods (Au@Pt NRs) to catalyze the reaction between 3,3’,5,5’-tetramethylbenzidine (TMB) and H₂O₂, thereby generating oxTMB with strong SERS signals. The generated oxTMB serves as an endogenous signaling molecule to realize a triple signal amplification strategy (nanozyme catalysis, Au NP enhancement, and CHA target amplification). This approach facilitates the ultrasensitive, synchronous, dual-target detection of the gastric cancer-related markers miR-196b and miR-221, demonstrating high clinical accuracy in serum samples. Although this triple-amplification design enables ultra-sensitive detection, the intricate, multi-step preparation of SERS probes presents hurdles in batch-to-batch reproducibility. Similarly, Ma et al[27] constructed an electrochemical biosensor by integrating a molybdenum disulfide nanozyme, a hybridization chain reaction, and enzyme-catalyzed amplification technologies. This biosensor efficiently detected miR-19b-3p in clinical samples from both healthy individuals and patients with stage I and III gastric cancer, achieving a limit of detection (LOD) as low as 0.7 aM. Despite its outstanding sensitivity, the electrochemical sensor is highly susceptible to biofouling in raw serum specimens, necessitating rigorous sample pretreatment to maintain reliability. To expand the diagnostic range, Peng et al[28] developed a photoelectrochemical immunosensor employing a Z-scheme Mn-doped BiVO₄/Au/Bi₂S₃ heterojunction synergized with Fe₃O₄@Pt nanozymes. This system achieves signal amplification by integrating transition metal doping, noble metal loading, and nanozyme-mediated catalytic cascades, yielding a wide linear detection range (0.001-100 U/mL) and an ultra-low LOD (0.0004 U/mL) for the gastric cancer biomarker CA72-4. Nevertheless, the intricate chemical synthesis of such multi-component heterointerfaces complicates standardized clinical manufacturing.

To facilitate non-invasive screening, saliva-based assays have been actively explored[29]. Specifically, Yao et al[30] developed a bimetallic heterostructured nanozyme (3-MPBA: Co-TA@Ag NPs) for the SERS-based, high-sensitivity detection of significantly elevated D-alanine and D-proline in saliva specimens from gastric cancer patients. The sensor accomplishes quantification by measuring Raman peak intensity, yielding LODs of 2.37 μM and 2.15 μM for D-proline and D-alanine, respectively, with high specificity and diagnostic efficiency. Furthermore, the salivary D-proline/D-alanine ratio can be utilized for differential screening. While clinically accurate, this method’s reliance on benchtop SERS spectrometers hinders its translation to point-of-care settings. Alternatively, Cheng et al[31] demonstrated that polyethyleneimine-functionalized copper-iron Prussian blue analog (PEI-CuFc) nanozymes can serve as efficient POD mimics for the sensitive colorimetric detection of D-amino acids and urease, two gastric cancer-related biomarkers. This system provides a low-cost, visual readout; however, its narrow linear range limits the detection of trace target fluctuations in early-stage gastric cancer. To address this limitation, Deng et al[32] demonstrated a non-invasive diagnostic method for gastric cancer based on a plasmonic Pt/Ti3C2Tx MXene nanozyme designed to detect salivary D-amino acids. This nanozyme exhibits enhanced POD activity and photothermal performance under near-infrared (NIR) light excitation, promoting the oxidation of D-amino acids to generate H₂O₂, which subsequently oxidizes the chromogenic substrate. The intensity of the resulting color change is linearly proportional to the concentration of D-amino acids. This colorimetric-photothermal dual-mode detection platform exhibits high sensitivity and specificity, and was successfully applied to the analysis of 45 clinical saliva samples, confirming its feasibility and accuracy for early gastric cancer screening. However, the long-term structural stability of MXene sheets in aqueous salivary environments remains a critical concern.

Beyond liquid biopsies, stool testing is vital for colorectal cancer (CRC) screening. Liu et al[33] developed a pump-free microfluidic chip (referred to as the LP chip) for the automated detection of circulating cancer stem cells (CCSCs) in blood and fecal samples to assist in the clinical diagnosis and prognostic prediction of CRC. The system primarily utilizes hyaluronic acid-functionalized CoPt₃ nanoparticles (CoPt₃@HA) as nanoprobes to target CCSCs via magnetic separation and catalyze colorimetric reactions through their POD-like activity. The chromogenic signaling outputs can be read with the naked eye or quantitatively analyzed via a smartphone on the test and control lines of the chip, demonstrating excellent linearity within the range of 0 to 10⁵ cells/mL and a detection limit as low as 3 cells/mL. Preliminary clinical validation shows that the LP chip holds great potential for timely diagnosis, treatment monitoring, and recurrence prediction of CRC. Although smartphone-based analysis provides outstanding clinical accessibility, the biochemical heterogeneity and high viscosity of fecal samples present significant challenges for automated cell separation, highlighting the need for standardized sample homogenization protocols. In summary, as summarized in Table 2, nanozymes can detect relevant tumor markers by specifically recognizing trace substances secreted by tumors or endogenous biomolecules generated through specific catalytic reactions, thereby providing strong support for the early screening and diagnosis of GI malignancies.

Table 2 Applications of nanozymes in non-invasive diagnosis of gastrointestinal malignancies.

Types of tumors	Nanozyme	Mimic activity	Mechanism and Function	Detecting substances	Sample	Ref.
Gastric cancer	Au@Pt NRs	Peroxidase	Integration of nanozyme catalysis, gold nanoparticle amplification, and catalytic hairpin amplification	miR-196b and miR-221	Serum	[15]
	Co-TA@Ag NPs(3-MPBA)	Peroxidase	Hydroxyl esterification reaction of D-alanine, D-proline, and 3-MPBA	D-alanine and D-proline	Stomach fluid and saliva	[18-20]
	MoS2	Horseradish peroxidase	Utilizing nanozymes, hybridization chain reaction, and enzyme-catalyzed amplification technology	miR-19b-3p	Healthy individuals and stage I & III gastric cancer patients	[16]
	PEI-CuFc	Peroxidase	Sensitivity in colorimetric detection; high-efficiency peroxidase-mimicking catalyst	D-amino acids and urease	Saliva	[21]
	Pt/Ti3C2Tx Mxene	Peroxidase and thermal performance	Colorimetric-photothermal dual-mode detection and oxidation of chromogenic substrates	D-amino acids	Saliva	[22]
	Fe3O4@Pt	Peroxidase	Integration of transition metal doping, noble metal loading, and nano-peroxidase-mediated signal amplification strategies	CA72-4	Serum	[17]
Colorectal cancer	CoPt3@HA	Peroxidase	Peroxidase activity catalyzed colorimetric reaction	Circulating cancer stem cells	Blood and stool	[23]

Molecular imaging diagnosis of GI malignant tumors mediated by nanozymes: The application of nanozymes in molecular imaging provides a novel approach for the precise localization and visual diagnosis of GI malignancies[34]. Nanozymes with POD or OXD activity can catalyze endogenous or exogenous substrates to generate imaging signals under TME stimulation (such as elevated H₂O₂ levels and low pH)[24]. For example, MnO₂-based nanozymes[35] can respond to the H₂O₂-rich and acidic TME by decomposing to release Mn²⁺, which significantly enhances the signal in the tumor area as a positive magnetic resonance imaging (MRI) contrast agent[36-38]; Kim et al[39] designed a hydrophobically modified manganese oxide (Mn₃O₄) (HMO) nanoparticle-loaded nanoassembly (MTS@HMO). After intravenous injection, these nanocomponents are degraded by the abundant ROS in the hypoxic TME, releasing HMO particles that break down into Mn²⁺ ions, facilitating real-time monitoring of colon tumors via T1-weighted MRI. Although this responsive imaging mechanism provides high-resolution anatomical detail, the potential translocation and cumulative neurotoxicity of free Mn²⁺ ions pose significant biosafety concerns, requiring exhaustive longitudinal clearance profiling prior to clinical implementation. Chen et al[40] reported a nanozyme-based photothermal agent (CeO₂-Fe₃O₄) that combines POD activity, prodrug carrier function, and MRI contrast properties. Although hybrid nanozymes like CeO₂-Fe₃O₄ synergize MRI contrast enhancement with therapeutic cargo delivery, the structural complexity of these multi-component hybrids compromises synthetic reproducibility - a major hurdle for regulatory standardization. In contrast to in vivo imaging, ex vivo diagnostic platforms offer high sensitivity but lack spatial orientation. For example, Cabrero-Martín et al[41] reported an electrochemical sandwich immune platform based on CeO₂ nanoparticles (CeO₂NPs) for highly sensitive detection of T cell immunoglobulin mucin domain 1, a biomarker associated with cancer angiogenesis. The platform exhibits excellent pseudo-POD activity and outperforms traditional enzyme labeling methods in terms of sensitivity, linear range, and anti-interference ability. It can directly analyze diluted plasma samples, facilitating the accurate diagnosis and stratification of CRC patients, and the establishment of corresponding clinical thresholds. While this assay outperforms traditional enzyme-linked assays in clinical plasma stratification, its ex vivo nature cannot assist clinicians in identifying real-time tumor borders during surgical or endoscopic resections. To bridge this gap, some nanozymes can catalyze substrates to generate fluorescence or photoacoustic signals for imaging[42,43], which can further improve diagnostic sensitivity and spatial resolution, and achieve real-time monitoring of tumor dynamic changes. For example, Zhang et al[44] developed a carbon-gold hybrid nanoprobe (OMCAPs@rBSA-FA@IR780), which demonstrated excellent NIR fluorescence imaging performance in MGC803 tumor-bearing mice, successfully delineating gastric tumors. Despite their high signal-to-noise ratios, the fundamental limitation of optical imaging lies in the restricted penetration depth (generally < 1 cm) of excitation and emission wavelengths through dense fibrotic GI tissues. Consequently, the clinical translation of these optical and photoacoustic nanozymes depends heavily on their integration with fiber-optic endoscopes orintra operative navigation devices to guide mucosal resection boundaries.

In summary, nanozymes can be used to diagnose and stratify GI malignancies based on their enzymatic catalytic activity, combined with imaging techniques such as fluorescence, immunology, photoacoustic, and MRI. This assists clinicians in accurately assessing tumor size, location, and infiltration range. When combined with endoscopic technology, it provides an important basis for defining surgical or endoscopic resection margins and developing personalized treatment plans.

Application of nanozymes in staining and DNA detection identification of pathological tissue slices of GI malignant tumors: Nanozymes also demonstrate significant value in the staining of pathological sections and the epigenetic profiling of GI malignant tumors. Traditional immunohistochemical screening relies heavily on natural enzymes like horseradish POD (HRP), which are susceptible to thermal denaturation, demand cold-chain logistics, and incur high costs. Nanozymes, with their robust structural stability, excellent biocompatibility, and catalytic activity, have the potential to replace traditional biological enzymes as a new generation of staining agents[24]. Zhang et al[45] synthesized cobalt-doped magnetite-core ferritin (M-HFn) nanoparticles (M-HFn-Co_xFe_3-xO₄) to enhance POD-like activity and tumor tissue visualization. Compared with undoped samples, the cobalt-doped nanoparticles exhibited a 1.7-fold increase in POD-like activity. Upon staining, tumor tissues from breast, colorectal, gastric, and pancreatic cancers displayed a deeper brown color, with clear boundaries distinguishing cancer cells from healthy counterparts. While this biomimetic protein-shell design dramatically improves biocompatibility and targeting specificity, the complicated synthesis of recombinant human heavy-chain ferritin shells and potential batch-to-batch variations in cobalt-doping stoichiometry pose challenges for standardized clinical mass production. To simplify probe fabrication, Wu et al[46] reported ultrafine iron oxide particles (USPIO) modified with dimercaptosuccinic acid (DMSA). These low-cost DMSA-USPIO particles can replace expensive HRP. By conjugating nimotuzumab to the nanoparticle surface, the authors constructed an ultrafine nanoprobe capable of detecting epidermal growth factor receptor overexpression on the membrane of esophageal cancer cells. Although this inorganic probe circumvents the degradation risks associated with natural HRP, controlling the orientation of conjugated antibodies to maximize binding affinity remains difficult. Furthermore, steric hindrance introduced by nanoparticle conjugation might reduce staining sensitivity compared to modern polymer-amplified clinical detection systems.

Beyond anatomical pathology, nanozymes facilitate epigenetic profiling of GI tract cancers. Bhattacharjee et al[47] developed a mesoporous iron oxide (MIO)-based assay for detecting global DNA methylation in CRC cell lines. Target DNA was isolated, denatured into single-stranded DNA (ssDNA), and directly adsorbed onto the surface of screen-printed gold electrodes (SPGEs). Subsequently, 5-methylcytosine antibody (5mC)-functionalized nanomaterials (MIO-5mC) were employed to recognize the methylcytosine groups on the SPGEs. The MIO-5mC conjugates catalyzed the oxidation of TMB in the presence of hydrogen peroxide, enabling both colorimetric visualization and electrochemical detection of DNA methylation. This detection method reliably identifies differences in global DNA methylation levels as low as 10% in synthetic samples and cell lines, demonstrating high reproducibility and specificity. Furthermore, it avoids the use of HRP and eliminates traditional PCR-based amplification and bisulfite treatment steps, positioning it as a low-cost and highly promising platform for whole-genome DNA methylation analysis, potentially opening new prospects for detecting human cancers or chronic diseases. While this amplification-free approach significantly shortens processing times, the direct adsorption of raw genomic ssDNA onto SPGEs remains highly susceptible to interference from non-target biomolecules and cellular fragments in clinical biopsy lysates. Such matrix effects can compromise analytical specificity and reproducibility.

Other relevant studies have demonstrated that certain nanozymes, such as iron oxide nanoparticles, exhibit POD-like activity. This allows them to catalyze the color change of staining substrates at specific sites in tissue sections, thereby clearly revealing the morphology and structure of tumor cells[48]. Based on existing research, nanozymes hold promise for the quantitative analysis of GI pathological diseases through dye-based diagnostics by combining unique optical properties and enzyme-mimetic catalytic activity. These methods are user-friendly, cost-effective, and provide stable staining effects, enabling more accurate labeling of tumor cells and tissues[49]. This aids pathologists in achieving rapid and accurate diagnoses, enhancing diagnostic reliability and accuracy in tumor staging, and providing critical basis for the formulation of personalized treatment regimens.

Ultimately, while nanozyme-mediated histological staining offers superior chemical stability and cost benefits, the standardization of incubation protocols, the elimination of endogenous POD activity, and the minimization of non-specific background staining remain critical bottlenecks that must be addressed before these systems can be clinically validated and integrated into digital pathology workflows.

Application of nanozymes in the treatment of GI malignant tumors

The synergistic effect of direct catalytic killing and physical therapy of nanozymes in GI malignant tumors: Nanocatalytic therapy (NCT) mainly utilizes nanozymes to catalyze the excessive production of hydrogen peroxide (H₂O₂) within the TME to generate highly toxic ROS, thereby killing tumor cells[50]. The therapeutic efficacy of nanozymes in GI malignancies primarily depends on their ability to catalyze the generation of ROS through Fenton-like reactions within the TME[51,52]. This localized oxidative stress triggers tumor cell death through distinct molecular pathways. First, excessive ROS accumulation disrupts mitochondrial membrane potential, leading to the release of cytochrome c and the subsequent activation of the caspase-dependent apoptotic cascade[53]. Second, ROS-induced lipid peroxidation – the accumulation of lipid peroxides in the cell membrane - serves as a critical driver of ferroptosis, a non-apoptotic form of cell death that is particularly effective against drug-resistant tumor cells[51,54]. Beyond direct cytotoxicity, ROS-mediated oxidative stress plays a pivotal role in modulating the tumor immune microenvironment. Specifically, it promotes immunogenic cell death (ICD), characterized by the translocation of calreticulin to the cell surface and the release of damage-associated molecular patterns such as HMGB1 and ATP[55,56]. These signals facilitate the maturation of dendritic cells (DCs) and the subsequent priming of cytotoxic T lymphocytes (CTLs)[24], thereby transforming the “cold” TME into an “immunologically hot” one, which synergistically enhances the efficacy of immune checkpoint blockade therapies.

To enhance NCT, researchers have integrated nanozymes with physical therapies such as photothermal therapy (PTT) and photodynamic therapy (PDT)[36]. PDT utilizes photosensitizers to generate ROS upon irradiation at specific wavelengths, while PTT employs nanozymes with high photothermal conversion efficiency to induce local hyperthermia, thereby promoting targeted tumor ablation[57,58]. However, traditional PDT has limitations such as limited tissue penetration depth and tumor hypoxic microenvironment[59,60]. Combining nanozymes with physical therapies such as PTT and PDT[36] can enhance the physical ablation of tumors through photothermal conversion or the generation of ROS[61], and overcome the limitations of traditional phototherapies in terms of tissue penetration depth and tumor hypoxia.

To overcome the main limitations of traditional phototherapy, Zhang et al[25] fabricated DNA-templated Ag@Pd alloy nanoclusters (DNA-Ag@Pd NCs) that combine POD-like activity with NIR-II photothermal conversion to inhibit MKN-45 gastric cancer growth. While NIR-II photoacoustic imaging offers exceptional spatial resolution, the potential leakage of toxic Ag⁺ and Pd²⁺ ions under gastric acid conditions poses a long-term biosafety risk. Moreover, scaling up DNA-templated synthesis while maintaining consistent catalytic yields remains a significant manufacturing hurdle. Duo et al[62] developed a photosensitizer (AIEgen) composite material that mimics platelet-derived MnO₂ nanozymes with aggregation-induced emission properties. These biomimetic nanoparticles exhibit robust stability and tumor-targeting ability, alleviating hypoxia through CAT-like activity in the TME. Combined with intraperitoneal intervention via fiber-optic direct irradiation of deep tumors, they significantly improve the photodynamic efficacy for in situ colon cancer. Despite this elegant design, the isolation and purification of natural platelet membranes suffer from low batch-to-batch reproducibility. Furthermore, the clinical necessity for invasive intraperitoneal fiber-optic insertion limits patient compliance and elevates infection risks.

Additionally, transition metal vacancy engineering has been leveraged to construct multifunctional agents. Wang et al[63] reported an ultra-thin trimetallic nanosheet (TMNS, Ru₃₈Pd₃₄Ni₂₈) capable of efficiently scavenging reactive oxygen/nitrogen species and exhibiting excellent photothermal conversion performance by introducing Ru and Ni atoms and designing surface atomic vacancies. It can ablate CT-26 colon tumors under NIR-II laser irradiation without recurrence. Its antioxidant activity can significantly alleviate colitis induced by dextran sulfate sodium, demonstrating its potential in the treatment of colitis-associated CRC. Nonetheless, the clinical safety profile of this platform is constrained by the biological retention of nickel (Ni)[64], a known allergen and potential carcinogen. Similarly, Miao et al[65] investigated the preparation of polyethylene glycol (PEG)-coated ultra-small rhodium nanodots (Rh NDs). This material exhibits multi-enzyme-like activity and high photothermal conversion efficiency. Its POD-like activity can scavenge ROS, and its photothermal performance enables PTT guided by photoacoustic imaging, providing a multifunctional nanozyme platform for the anti-inflammatory and anti-tumor treatment of colon diseases. While therapeutically potent, the translation of rhodium-based nanozymes is hindered by the prohibitive cost of platinum-group metals. Additionally, the therapeutic window between their anti-inflammatory ROS-scavenging activity and their photothermal pro-oxidant tumor-killing efficacy must be precisely defined to avoid secondary damage to the adjacent healthy GI mucosa.

Nanozymes indirectly combat GI malignancies by regulating the tumor immune microenvironment: Nanozymes have also shown promising potential in modulating the tumor immunemicroenvironment (TIME) and enhancing anti-tumor immune responses. The imbalance of ROS and the presence of immunosuppressive factors within the TME often lead to suppressed immune responses. Nanozymes with antioxidant enzyme-like activities can scavenge excess ROS at the tumor site, thereby alleviating oxidative stress on infiltrating immune cells and ameliorating the immunosuppressive microenvironment[66]. Specifically, these nanozymes can activate DCs and promote the infiltration and proliferation of CTLs, thereby enhancing systemic anti-tumor immunity[23,67]. However, the clinical translation of these nanoplatforms requires a nuanced understanding of their long-term immunomodulatory mechanisms and biocompatibility profiles.

Antioxidant nanozymes, such as CeO₂ nanozymes[68], exhibit SOD- and CAT-like activities. These catalysts can effectively scavenge ROS in the CRC TME, ameliorate the immunosuppressive microenvironment, and enhance the efficacy of immune checkpoint inhibitors, achieving a synergistic immunotherapeutic outcome. While this alleviates oxidative stress, the precise regulation of ROS levels is critical; excessive scavenging may inadvertently impair the ROS-dependent activation of CTLs, necessitating a balanced dosage strategy for optimal immunomodulation.

To achieve active tumor targeting, She et al[69] developed a biomimetic nanomotor system designated as M@MnO₂-Au-mSiO₂@CDDP. This platform utilizes MnO₂ to catalyze endogenous H₂O₂ decomposition, generating oxygen bubbles that drive self-propulsion, while promoting tumor apoptosis through Fenton-like reactions resulting in ROS generation. The released Mn²⁺ ions activate the cyclic GMP-AMP synthase-stimulator of interferon genes pathway to amplify the anti-tumor immune response. Additionally, the vehicle is coated with M1-type macrophage membranes and loaded with cisplatin, enabling precise targeting and deep penetration via intraperitoneal perfusion, which holds significant promise for the treatment of gastric cancer peritoneal metastasis. While active self-propulsion and immune priming are innovative, the multi-component synthesis - involving membrane coating, inorganic core fabrication, and drug loading - presents significant challenges in batch-to-batch reproducibility and regulatory standardization for clinical translation.

Metabolic reprogramming represents another promising strategy. Jiang et al[70] developed a zinc-quercetin (Zn-Quer) coordination nanozyme synthesized from quercetin and zinc ions. These nanoparticles exploit the anti-inflammatory and antioxidant properties of quercetin, enhancing its bioavailability and therapeutic efficacy. In vitro assays and in vivo xenograft models demonstrated that this nanozyme exhibits direct cytotoxicity and inhibits the angiogenic signaling pathways driving pathological neovascularization. By disrupting molecular pathways governing proliferation and invasiveness, Zn-Quer nanozymes effectively inhibit gastric cancer cell growth, induce apoptosis, and reprogram the malignant phenotype. Although this metal-organic self-assembly strategy exhibits chemical elegance, the primary translational challenge lies in the high sensitivity of metal-phenolate coordination networks to acidic environments. Such structures are prone to premature protonation and dissociation in the highly acidic gastric lumen (pH = 1.5-3.5), thereby limiting oral delivery options and requiring systemic administration. Furthermore, while in vitro experiments and subcutaneous xenograft models demonstrate potent tumor cytotoxicity and anti-angiogenic efficacy, these simplified systems fail to recapitulate the complex, highly acidic in situ gastric microenvironment. Moreover, the absence of active targeting ligands on the Zn-Quer nanozyme platform raises biological concerns regarding non-specific accumulation and off-target toxicity in healthy organs.

Targeting tumor microecology represents a parallel path. Wang et al[71] developed a copper single-atom nanozyme (BSA-CuSAN). In vitro and in vivo studies demonstrated that BSA-Cu SAN passively targets tumor sites, generating ROS and depleting glutathione (GSH). This process efficiently clears the pathogen Fusobacterium nucleatum in situ, thereby disrupting the tumor-promoting bacterial symbiosis and synergistically eradicating CRC cells. Additionally, BSA-CuSAN is cleared via the renal pathway, minimizing long-term systemic toxicity. However, the long-term impact of heavy metal accumulation on renal tubular function requires further longitudinal toxicological evaluation. Similarly, Sun et al[72] constructed a layered double hydroxide/MgO₂(BM) nanoplatform stabilized by BSA and conjugated partially cross-linked CAT (pcCAT) and lactate OXD (pcLOX) onto its surface (BMCL). This drug-free nanoplatform effectively inhibited tumor growth, promoted anti-tumor immunity, and suppressed abscopal tumor growth in CT26 CRC mouse models at extremely low doses of the conjugated enzymes. Mechanistically, the BMCL nanozyme modulates the TME by reprogramming macrophages to achieve self-sustained oxygenation and lactate consumption-guided local immune activation. While this metabolic regulation is conceptually elegant, the stability of the conjugated enzymes (pcCAT and pcLOX) in the acidic and protease-rich TME remains a critical concern, potentially limiting their sustained therapeutic efficacy in vivo.

Finally, the synergy between nanozymes and chemotherapy represents a rapidly evolving field. Guo et al[73] employed nanoprecipitation to develop polymeric nanoformulations based on the FOLFOX regimen, incorporating oxaliplatin derivatives functionalized with folic acid (Nano-Flox) and the active 5-fluorouracil (5-FU) metabolite, FdUMP (Nano-FdUMP). The Nano-FdUMP formulation generates ROS, thereby augmenting ICD-mediated anti-tumor immunity induced by Nano-Flox and suppressing colorectal tumor growth. Furthermore, the combination of Nano-Flox/Nano-FdUMP and an anti-programmed death ligand-1 antibody significantly suppresses colorectal liver metastases in CRC mouse models. In such combinatorial studies, it is imperative to clearly delineate the nanozyme-mediated catalytic contribution from the direct cytotoxic effects of the chemotherapeutic payload to avoid overstating the nanozyme’s distinct immunomodulatory role. Ultimately, while these platforms demonstrate promising preclinical efficacy, future research must prioritize the standardization of synthetic protocols, the long-term biosafety of metallic components, and the validation of these systems in immunocompetent, orthotopic tumor models to ensure clinical translatability.

Nanozymes as multifunctional carriers for synergistic treatment of GI malignancies: Nanozymes, with their high specific surface area and good biocompatibility, can be used as drug carriers to achieve targeted delivery and synergistic therapy of chemotherapy drugs[74]. Their catalytic activity can cascade with the loaded drugs or other therapies, forming efficient treatment strategies with multiple synergistic mechanisms. Nonetheless, translating these benchtop designs into clinical applications demands a rigorous assessment of their structural complexity, manufacturing reproducibility, and long-term systemic safety.

To enhance the tumor targeting and tissue penetration of drugs, researchers are actively developing bionic nanomotors with nanozymes as the core carrier cores have been actively developed, enabling self-propelled motion to efficiently cross biological physiological barriers and deliver therapeutic payloads directly to tumor sites[75,76]. Such systems also improve intraperitoneal drug penetration and prolong local tumor retention time within the peritoneal cavity[77,78]. Simultaneously, the intrinsic enzymatic activity of the nanozymes can synergize with co-delivered chemotherapeutics to maximize antitumor efficacy.

Specifically, Luo et al[79] developed a biomimetic cascade nanozyme system (designated as PSC) that utilizes P-selectin-expressing platelet membranes to encapsulate single-atom copper nanozymes and cisplatin. This platform selectively targets CD44-overexpressing gastric cancer cells, wherein cisplatin activates nicotinamide adenine dinucleotide phosphate OXD to elevate intratumoral H₂O₂ levels. This elevation boosts the POD-like activity of the copper nanozymes, generating abundant ROS that drive tumor cell apoptosis in concert with photothermal ablation. In vitro and in vivo investigations demonstrated that the PSC system efficiently eradicates primary gastric tumors and associated lymph node metastases. Although this platform achieves superior CD44-mediated targeting, the utilization of natural cell membranes introduces biochemical heterogeneity in surface marker expression, potentially compromising therapeutic consistency. Moreover, the complex, multi-step fabrication of these membrane-encapsulated nanomotors[75-78] often suffers from low batch-to-batch reproducibility, posing a substantial hurdle for industrial scaling and regulatory approval.

Furthermore, the stability of “smart” release mechanisms remains a critical concern. Hao et al[80] combined ROS-responsive prodrugs with platinum nanozymes to construct a novel nanoparticle system (CPT-TK-Pa/Pt NPs). This platform utilizes platinum nanozymes to catalyze oxygen (O₂) generation from endogenous H₂O₂ within the tumor, thereby alleviating hypoxia and enhancing PDT. Under laser irradiation, the photosensitizer protoporphyrin A (Pa) generates local ROS, triggering the cleavage of the thioketal linkers in the prodrug to achieve controlled release of camptothecin, forming a self-enhancing therapeutic feedback loop that effectively inhibits colon cancer growth. Although theoretically robust, the “leaky” nature of ROS-responsive bonds in the complex, heterogeneous TME often leads to premature drug leakage, potentially reducing the therapeutic index and increasing off-target systemic toxicity. In more complex architectures, Zhu et al[81] utilized in vitro and in vivo models to evaluate a Ru@CeO₂ yolk-shell nanozyme platform. This system co-loaded the chemotherapeutic ruthenium complex (RBT) and resveratrol (Res), employing a PEG coating to construct an on-demand dual-drug delivery system (Ru@CeO₂-RBT/Res@PEG) designed to eradicate tumors and inhibit the metastasis and recurrence of CRC. The multi-drug loading capacity is impressive, yet the structural integrity of such bilayer systems during systemic circulation requires further validation. Additionally, Zhou et al[82] developed a nanoreactor comprising CAT nanocrystals and silver nanoparticles (AgNPs) as a carrier for the targeted delivery of doxorubicin (DOX) to colon tumors. Upon homing, endogenous hydrogen sulfide (H₂S) within the tumor converts the AgNPs into Ag₂S nanoparticles, which induce photothermal effects and NIR-II emission under 808 nm laser irradiation while triggering DOX release. This process achieves a synergistic combination of PTT and chemotherapy, resulting in complete tumor eradication with minimal side effects. However, the long-term systemic toxicity and potential accumulation of silver ions in the liver and spleen remain critical safety concerns that must be addressed before clinical trials.

Finally, nanozyme-mediated “starvation therapy” represents a paradigm shift in metabolic intervention. Mei et al[83] engineered aphytic acid (IP6)-modified ceria-gold nanocomposite (CeAIP NPs), in which the gold nanoparticles exhibit glucose OXD (GOx)-like activity to deplete glucose and generate H₂O₂. Subsequently, the cerium dioxide component displays POD-like activity, utilizing the generated H₂O₂ to produce hydroxylradicals (∙OH) for chemodynamic therapy. This cascade catalytic process (glucose depletion → H₂O₂ production → ∙OH-mediated cytotoxicity) simultaneously starves and eradicates tumor cells with high therapeutic efficiency. While highly effective in preclinical models, the systemic administration of GOx-mimicking nanozymes carries a non-negligible risk of inducing systemic hypoglycemia. Therefore, future clinical translation of these metabolic-interfering nanozymes must prioritize precise dosage control and the development of tumor-specific activation triggers to avoid adverse metabolic events in healthy tissues.

Application of non-metallic nanozymes in GI malignant tumors: Non-metallic nanozymes are nanomaterials composed of non-metallic elements such as carbon, nitrogen, boron, phosphorus, and sulfur, or their hybrid materials, exhibiting enzyme-like catalytic activity. Compared with their metal-based counterparts, they usually exhibit superior biocompatibility, tunable electronic structures, and adaptable catalytic activities, mitigating the risk of long-term toxicity associated with transition metal bioaccumulation (e.g., Fe-, Mn-, or Cu-based systems), thereby offering a safer profile for clinical translation. However, translating these metal-free platforms from bench to bedside requires a critical evaluation of their structural stability and synthetic reproducibility.

To target early-stage gastric lesions and prevent oncogenesis, Zhang et al[84] developed an in vivo-activatable, pH-responsive graphene nanozyme comprising PtCo nanoparticles anchored on graphene (denoted as PtCo@G). This platform exhibits OXD-like activity and potent antibacterial efficacy against Helicobacter pylori in a mouse model. The adverse effects on adjacent tissues and symbiotic microbiota were negligible, facilitating early intervention for gastric lesions to achieve primary prevention of GI malignancies. However, classifying PtCo@G as a strictly “non-metallic” nanozyme is conceptually inaccurate due to the reliance on platinum (Pt) and cobalt (Co) active centers. The potential leaching of these transition metals under highly acidic gastric conditions raises critical mucosal irritation and systemic bioaccumulation concerns, necessitating rigorous longitudinal clearance assays. Similarly, Zhang et al[85] reported aboron/nitrogen co-doped graphdiyne nanozyme for the treatment of colon cancer that exhibits efficient POD-like activity and GSH depletion capabilities, thereby inducing ferroptosis and apoptosis. While heteroatom doping successfully optimizes the surface charge density, the synthesis of graphdiyne remains complex. Low reaction yields and batch-to-batch variation in the doping stoichiometry present significant reproducibility challenges for clinical standardization.

Hybrid systems integrating non-metallic nanozymes with natural biomolecules also present unique challenges. Du et al[86] developed an amorphous, honeycomb-structured, nitrogen-doped carbon nanozyme (N/C) exhibiting NADH OXD- and CAT-like activities, which was conjugated with natural glucose dehydrogenase (GDH) to form an N/C-GDH system. Combined with 5-FU, this platform significantly inhibits the proliferation of HCT-116 colon cancer cells, reduces blood glucose levels, and induces apoptosis, extending the potential application of non-metallic nanozymes to glycemic regulation and synergistic oncotherapy. While this cascade effectively inhibits tumor proliferation when combined with 5-FU, the inclusion of the natural GDH component acts as a physiological bottleneck. Natural enzymes remain highly susceptible to proteolytic degradation and thermal denaturation within the hostile, enzyme-rich environment of the human GI tract, potentially compromising the overall catalytic efficiency of the hybrid platform.

Additionally, other phosphorus- and carbon-based allotropes are under active evaluation. Black phosphorus nanosheets (BP NSs) are promising two-dimensional allotropes widely studied in optoelectronics, transistors, and photocatalysis[87]. Recently, increasing attention has been focused on the biomedical applications of BP in cancer therapy owing to its unique physiochemical properties. BP NSs possess a high specific surface area and a negative surface charge, enabling efficient loading of chemotherapeutics, targeting ligands, photosensitizers, and magnetic nanoparticles. They also exhibit broad NIR absorption[88], making them potential candidates for cancer phototherapies, such as PTT and PDT[89]. Geng et al[90] designed iRGD-modified zein nanoparticlesco-loaded with BPQDs and gemcitabine (GEM) as a targeted nanoplatform (BP-GEM@NPs). The primary mechanism involves the synergistic induction of pancreatic cancer cell death by BPQDs and GEM via cell cycle arrest at the G2/Mand G0/G1 phases, respectively, with a combination index (CI) < 1. Following intravenous injection, in vivo biodistribution and pharmacokinetic profiles demonstrated that the BP-GEM@NPs exhibit excellent tumor-targeting capability and a significantly prolonged circulation half-life. The targeted co-delivery of BPQDs and GEM induced enhanced apoptosis of pancreatic tumor cells, resulting in synergistic tumor growth inhibition in both subcutaneous xenograft and orthotopic models, accompanied by satisfactory systemic biocompatibility. Although the rapid biodegradation of BPQDs into non-toxic phosphates prevents long-term bioaccumulation, the intrinsic structural instability of BP - owing to its hypersensitivity to ambient moisture and dissolved oxygen - remains a major barrier to shelf-life preservation and reproducible in vivo pharmacokinetics[91].

Carbon quantum dots (CQDs) are an emerging class of quasi-zero-dimensional photoluminescent nanomaterials with a particle size typically less than 10 nm. Due to their excellent aqueous dispersibility, high chemical inertness, stable optical properties, and outstanding biocompatibility, CQDs have gained significant prominence in oncological research[92,93]. Existing studies have demonstrated that quantum dots can be utilized as probes for the detection of GI malignancies by leveraging their intrinsic POD-mimicking properties and photoluminescent characteristics[94-96]. Nevertheless, CQDs synthesized via traditional hydrothermal carbonization often exhibit high polydispersity and heterogeneous surface chemistries. These factors lead to fluctuating quantum yields and variable targeting affinities, limiting their imaging reliability and impeding the implementation of standardized dosing schedules. Future research must prioritize surface passivation strategies and uniform synthesis methodologies to enhance the clinical translatability of these non-metallic platforms.

Remaining challenges and controversies in the clinical translation of nanocatalysts: Based on existing research, we can recognize that nanozymes hold promising prospects in the field of GI oncology; however, it must be acknowledged that this field remains in its early developmental stage. Although nanozymes have demonstrated significant potential in preclinical models, all reported applications are currently in the exploratory phase, and no nanozyme-based diagnostic or therapeutic agents have received clinical approval for GI malignancies. The frequently emphasized “excellent biocompatibility” and “high stability” in the current literature are heavily reliant on data obtained from immunodeficient mouse models and simplified in vitro conditions. Consequently, these findings cannot be directly extrapolated to human physiological environments. Furthermore, in human physiological environments, more complex immune responses, heterogeneous TMEs, and intricate physiological barriers are likely to significantly impact therapeutic efficacy.

Based on existing research, the primary focus of current clinical translation is the long-term biosafety of metal-based nanozymes[23,97]. In contrast to biodegradable organic materials, inorganic nanoparticles exhibit persistent bioaccumulation in organs such as the liver, spleen, and intestine[98], and their chronic toxicity remains poorly characterized[99]. Most existing studies focus predominantly on acute toxicity profiles, failing to address the potential for long-term organ damage or chronic systemic inflammation[100]. Furthermore, the pharmacokinetics and metabolic pathways - encompassing absorption, distribution, metabolism, and excretion (ADME) characteristics - of these materials remain highly elusive. Without comprehensive, longitudinal studies that rigorously evaluate the clearance kinetics, biodistribution, and potential immunogenicity of these nanomaterials, their clinical safety profiles remain speculative. Future research must shift from merely demonstrating catalytic efficacy to establishing standardized regulatory protocols, focusing on the long-term fate of these materials in vivo to bridge the significant translational gap between bench side innovation and bedside clinical translation.

While the catalytic potential of nanozymes is well-documented, their clinical viability depends strictly on overcoming the hurdles of systemic toxicity and targeting precision. Specifically, their clinical translation is currently hindered by a limited understanding of their in vivo pharmacokinetics and hemocompatibility. Recent studies indicate that upon entering the bloodstream, nanozymes are rapidly coated by a “protein corona[101]”, which significantly alters their surface-physicochemical properties, biodistribution, and cellular uptake, frequently leading to premature clearance by the mononuclear phagocyte system. To address these biocompatibility and metabolic challenges, future research must prioritize the following three core development strategies: First, enhancing targeting precision is paramount. Beyond passive accumulation via the enhanced permeability and retention effect, it is highly recommended to employ biomimetic strategies, such as cell-membrane camouflaging (e.g., utilizing erythrocyte or tumor cell membranes), to evade immune surveillance and improve tumor-specific homing. Furthermore, surface functionalization with tumor-specific ligands, such as aptamers or monoclonal antibodies, can significantly reduce off-target toxicity in healthy surrounding GI tissues.

Second, improving biosafety requires the development of “smart” nanozymes engineered to respond to the unique TME. For instance, constructing nanozymes that are selectively activated by the acidic pH or high H₂O₂ levels characteristic of GI tumors can minimize systemic side effects. Additionally, shifting toward biodegradable materials, such as MOFs or carbon-based nanostructures, is essential to facilitate renal clearance and prevent long-term tissue bioaccumulation.

Finally, optimizing the preparation process is crucial for ensuring the reproducibility of nanozymes. It is recommended to adopt a microfluidic synthesis platform to achieve precise control over nanoparticle size, morphology, and surface chemistry, thereby guaranteeing batch-to-batch consistency - a prerequisite for obtaining regulatory approval and clinical translation.

CONCLUSION

Patients with GI malignant tumors are often diagnosed late due to hidden early symptoms, and due to the significant side effects of radiotherapy and chemotherapy, immune targeted therapy is limited by the complexity of the TME, resulting in limited efficacy and low survival rates. Nanozymes, with their stable and adjustable catalytic activity, diverse design, synthesis, and functionalization methods, good tissue penetration and cell accumulation abilities, as well as targeted delivery and catalytic drug release characteristics, can provide more possibilities for the development of new GI malignancies for diagnosis and treatment, as shown in Tables 3 and 4.

Table 3 Applications of nanozymes in the treatment of gastric malignancies.

Type pathway	Nanozyme	Mimic activity	Function	Tumor model	Ref.
DNA-templated Ag@Pd alloy nanoclusters	Ag@Pd	Peroxidase	Exhibit high photothermal conversion efficiency, enhanced reactive oxygen species generation, improved permeability, and enhance nanocatalytic therapy	MKN-45 cells and mouse model	[42]
Drug delivery system based on nanomotors	MnO2-Au-mSiO2	Peroxidase	Effectively link nanomotors, enhance reactive oxygen species production, and activate the stimulator of interferon genes pathway	MFC cells and mouse models; gastric cancer organoid models	[54]
Nanocoordination polymers	Zn-Quer	Anti-inflammatory and antioxidant properties	Induce cytotoxicity, inhibit angiogenesis, and disrupt molecular pathways related to cell proliferation and invasiveness	MKN-45 cells and mouse model	[55]
P-selectin protein platelet membrane encapsulates SAZ and cisplatin	Cu	Peroxidase	Specifically target cancer cells within aggressive primary tumors and metastatic lymph nodes	MFC cells and mouse models	[64]

Zn-Quer: Zinc-quercetin.

Table 4 Applications of nanozymes in the treatment of colorectal malignancies.

Nanozyme	Type pathway	Mimic activity	Function	Tumor model	Ref.
MnO2	Platelet-mimetic MnO2 nanozyme/AIEgen composite	Catalase	Relieve hypoxia in the tumor microenvironment and perform photodynamic therapy	CT-26 cells and mouse models	[48]
Ru38Pd34Ni28	Ru38Pd34Ni28 ultra-thin ternary metal nanosheets	Catalase and multi-enzyme-like anti-inflammatory activity	Clear reactive oxygen species and reactive nitrogen species; enhance photothermal conversion efficiency and antioxidant activity	CT-26 cells and mouse models	[49]
Rh-PEG NDs	Polyethylene glycol-coated ultrasmall rhodium nanodots metal nanocatalyst	Catalase	Clear reactive oxygen and nitrogen species; enhance photothermal performance	CT-26 cells and mouse models	[50]
BSA-Cu SAN	Proteins support copper single-atom nanozymes	Peroxidase	Eliminate the pathogen F. nucleatum within tumors to disrupt the pathogenic symbiosis in the tumor microenvironment	HCT116 cells and mouse models	[56]
LDH/MgO2 (BM)	Acid-hydrolyzed LDH-/MgO2-based pcCAT/pcLOX nanozymes	Catalase and lactate oxidase	Induce self-oxygenation and enhanced lactic acid consumption, as well as local immune activation and anti-angiogenesis through tumor microenvironment regulation	CT-26 cells and mouse models	[57]
Nano-Folox/Nano-FdUMP	Nanoprecipitation technology based on FOLFOX	Peroxidase	Mediates the formation of ROS and promotes immunogenic cell death-related anti-tumor immunity	CT26 and Hepa1-6 cells and mouse models	[58]
Pt-NP	ROS response to nano-prodrug (CPT-TK-Pa/Pt NP)	Peroxidase	Utilizes platinum nanozymes to catalyze the production of oxygen from hydrogen peroxide within tumors to alleviate hypoxia and enhance the efficacy of photodynamic therapy	CT-26 cells and mouse models	[65]
Ru@CeO2-RBT/ResDPEG	On-demand released dual-drug delivery system (Ru@CeO2-RBT/ResDPEG)	Peroxidase	Provide oxygen supply, deliver anti-cancer drugs, and enhance photothermal therapy	CT-26 cells and mouse models	[66]
AgNP; CatCry	Protein crystal base nanoparticles (CatCry-AgNP-DOX)	Catalase	Provide oxygen supply and facilitate the delivery of anti-cancer drugs	HCT116 cells and mouse models	[67]
BN-GDY	Non-metallic ferroptosis and apoptosis inducers based on boron and nitrogen co-doped graphdiyne (BN-GDY)	Peroxidase	Provide oxygen supply and induce ferroptosis and apoptosis	CT26 and HCT-116 cells and mouse models	[70]
N/C	Amorphous honeycomb nitrogen-doped carbon (N/C) nanozyme	NADH oxidase and catalase	Provide oxygen supply, facilitate the delivery of anti-cancer drugs, and induce cell apoptosis	HCT-116 cells and mouse models	[71]

F. nucleatum: Fusobacterium nucleatum; pcCAT: Partially cross-linked catalase; pcLOX: Partially cross-lactate oxidase.

Although nanozymes have demonstrated significant preclinical progress, they confront several translational bottlenecks. First, their long-term biosafety, in vivo metabolic pathways, and potential chronic toxicities require more rigorous characterization. Second, their catalytic efficiency and tumor-targeting specificity must be optimized to meet clinical standards. Finally, substantial hurdles remain regarding the large-scale, reproducible preparation of clinical-grade nanozyme diagnostic and therapeutic systems. Nevertheless, continuous advancements in nanomaterial modification and biomedical engineering are projected to yield nanozymes with improved catalytic activity, targetability, and biocompatibility. When integrated with multimodal imaging and combination therapy strategies, these platforms are poised to play a pivotal role in early diagnosis, precise treatment, and prognosis evaluation of GI malignancies. Concurrently, expanding mechanistic investigations of nano-bio interface interactions and establishing standardized quality control protocols will accelerate clinical translation, ultimately maximizing therapeutic benefits for gastric and CRC patients.

In summary, nanozymes represent a transformative paradigm for the theranostics of GI malignancies, offering a unique combination of catalytic efficiency and multifunctional potential. Nonetheless, the bench-to-bedside transition remains a formidable challenge. To bridge this translational gap, the field must transcend simple efficacy demonstrations and focus on rigorous, longitudinal evaluations of in vivo ADME profiles and chronic toxicity. Consequently, the strategic roadmap for future development must emphasize: (1) The engineering of biomimetic, TME-responsive nanozymes to enhance targeting efficiency and biocompatibility; (2) The standardization of synthesis protocols via microfluidic technologies to ensure clinical-grade reproducibility; and (3) The integration of multi-omics and longitudinal imaging to fully elucidate the metabolic fate of these materials. By addressing these critical bottlenecks through a collaborative multidisciplinary framework - integrating materials science, immunology, and clinical oncology - nanozymes are poised to become a cornerstone of personalized medicine for colorectal and gastric cancer patients.

ACKNOWLEDGEMENTS

We would like to express our sincere gratitude to everyone who supported us throughout the preparation of this review.