Utility of transporter/receptor(s) in drug delivery to the eye

Table 1 List of transporter/receptor(s) present in the eye

Tissue	Transporter/receptor	Subtypes	Ref.
Cornea	Amino acid	LAT1, LAT2, Phenylalanine, tyrosine	[213,214]
	Glucose	GLUT1	[215]
	Nucleoside		[216]
	Peptide	hPEPT1	[90]
	Folate		[180]
	Biotin		[175]
Conjunctiva	Acid-base	NKCC, HE1	[217]
	Amino acid	Bo,+	[218]
	Glucose	GLUT1	[157,219]
	Peptide	Dipeptide	[220]
	Monocarboxylate		[221]
	Nucleoside		[113]
Lens	Amino acid	System A, L, Gly, Ly+, β, ASC	[222]
	Ascorbic acid	SVCT2	[223]
	Glucose	GLUT1, GLUT3	[224]
	Glutathione	R-GSHT	[225]
Iris-ciliary body	Glucose	GLUT1, GLUT4	[226]
	Nucleoside		[227]
Retina	Amino acid	Glycine, glutamine, arginie, proline, taurine	[99,228,229]
	Glucose	GLUT1, GLUT3	[230]
	Monocarboxylic acid	MCT1, MCT3	[231,232]
	Nucleoside		[121,233]
	Peptide	PEPT1, PEPT2, PHT1, PHT2	[92,93,95,96]
	Vitamins(ascorbic acid, biotin, folic acid, riboflavin)	SVCT2, RFT, FR-α, SMVT	[85,183]

Table 2 Vitreous pharmacokinetic parameters of ganciclovir and biotin-ganciclovir following intravitreal administration (mean ± SD)

Parameters	GCV	(Biotin-GCV)
		Biotin-GCV	Regenerated GCV
AUC (mg/mL per minute)	10.6 ± 1.27	17.5 ± 1.38a	1.85 ± 0.744
λz (× 10-3/min)	2.58 ± 0.124	3.19 ± 0.536
T1/2 (min)	270 ± 15.7	222 ± 40.5
Vss (mL)	1.56 ± 0.100	1.47 ± 0.106
Cl (μL/min)	4.39 ± 0.603	5.45 ± 0.673
MRT last (min)	197 ± 22.2	175 ± 17.6	264 ± 9.26
Clast (μg/mL)	7.06 ± 1.38	8.28 ± 2.27
Cmax (μg/mL)			5.37 ± 0.435
Tmax (min)			66.7 ± 23.1

^aP<0.05 vs the control. GCV: Ganciclovir; AUC: Area under the vitreous time concentration curve; λ_z: Elimination rate constant; T_1/2: Vitreal elimination half-life; V_ss: Volume of distribution at steady; Cl: Clearance state; MRT: Mean residence time. Reproduced with permission from[176].