Atsushi Maeda

Lactose-carrying polystyrene as a drug carrier: investigation of body distributions to parenchymal liver cells using 125I-labelled lactose-carrying polystyrene

Directed toward pharmacological applications of lactose-carrying polystyrene, (poly (N-p-vinylbenzyl-O-β-D-galactopyranosyl-(l→4)-D-gluconamide), PVLA), its body distribution, clearance from blood and specific binding to receptors have been investigated using radiolabelled PVLA. 125I-Labelled PVLA was prepared via copolymerization of N-p-vinylbenzyl-O-β-D-galactopyranosyl-(l→4)-D-gluconamide (VLA) with 10 mol% of 4-(2-propenyl)phenyl acetate followed by radiolabelling of the latter component. When 125I-labelled PVLA was injected into rats through their tail veins, the radioactivity was distributed highly to liver, less to thyroid gland, cecum-large intestine, urine, feces and blood, and much less to lung, heart, kidney, spleen, pancreas, small intestine and urinary bladder. Its concentration to liver was visible by whole-body autoradiography. It was clarified that about 97% of PVLA was distributed to parenchymal liver cells and only 3% to nonparenchymal liver cells. The radioactivity in blood was decreased with time according to a biexponential curve. A two open compartment model is proposed on the basis of the pharmacokinetic analysis of the equation, which elucidated that PVLA migrated rapidly from blood to parenchymal liver cells. Specific binding between 125I-labelled PVLA and asialoglycoprotein receptors on parenchymal liver cells was demonstrated by its inhibition with asialofetuin. The bond dissociation constant estimated by Scatchard analysis was Kd=1.4x10-9 M. The binding was as strong as those of several naturally occurring asialoglycoproteins. These properties of PVLA, as liver-specific targeting materials using galactose ligands as recognition signals to asialoglycoprotein receptors, are discussed with the conformational structures of PVLA which can carry drugs in their hydrophobic regions.

Sugar-Branched-Cyclodextrins as Injectable Drug Carriers in Mice

The purpose of this study was to investigate stable complexation of drug in blood by sugar-branched-beta-cyclodextrins (beta-CDs) such as glucose (glu)- or galactose (gal)-branched-beta-CDs and the pharmacokinetic disposition of drug in sugar-branched-beta-CD complex. Complexation of steroidal drugs in sugar-branched-beta-CDs and their replacement by cholesterol were measured. The complexes of dexamethasone/glucosyl-beta-CDs (dexamethasone/glu-beta-CD or dexamethasone/glu-glu-beta-CD) were not replaced by cholesterol, which is a representative endogenous compound, whereas the complex of dexamethasone/beta-CD was replaced by cholesterol. The same results were obtained in steroidal drugs such as hydrocortisone, triamcinolone, and prednisolone. Thus, the use of glu-beta-CD and glu-glu-beta-CD permitted the stable complexation of the drug in water. Stability constants of dexamethasone/glu-glu-beta-CD and dexamethasone/gal-glu-beta-CD complexes are the same, which means that the sugar moiety of the side chain in beta-CD has little effect on stability constants. After the dexamethasone/gal-glu-beta-CD complex or the dexamethasone/glu-glu-beta-CD complex (dexamethasone: 1 mg/body) was administered intravenously to mice, dexamethasone concentrations in liver tissue and blood were measured. The dexamethasone/gal-glu-beta-CD complex (66.1 +/- 1.7 micrograms as dexamethasone/gram of liver tissue) was distributed to liver tissue significantly more than the dexamethasone/glu-glu-beta-CD (beta-CD) complex (59.9 +/- 1.0 micrograms as dexamethasone/gram of liver) at 30 min after administration (p < .05). Sugar-branched-beta-CD gave a water-soluble and stable complex for dexamethasone and changed the disposition of dexamethasone. Sugar-branched-beta-CDs are potentially excellent carriers for a steroidal injectable formulation.

Specific interaction between galactose branched-cyclodextrins and hepatocytes in vitro

Abstract The purpose of this experiment was to investigate specific interaction between galactose branched-cyclodextrins (gal-CyDs) and hepatocytes in vitro. Gal-CyDs were synthesized by an enzymatic method by using β -galactosidase. Gal-CyDs, galactose, glucose branched-CyDs (glu-CyDs) or glucose were incubated with hepatocytes on lactosyl polystyrene polymer (PVLA, high binding to hepatocytes) coated dish. It was found that adherence of hepatocytes to PVLA was inhibited by incorporation of gal-CyDs or galactose in the incubation medium at a concentration of 10 mM, but was not inhibited by incorporation of glu-CyDs or glucose at 20 mM. Further, after incubation of hepatocyte suspension with both fluorescein isothiocyanate-PVLA (FITC-PVLA) and gal-CyDs, gal-CyDs at 10 mM did inhibit the binding of FITC-PVLA to hepatocytes. In conclusion, it was suggested that enzymatically synthesized gal-CyDs have specific interaction with hepatocytes and may be useful as a drug targeting carrier to hepatocytes.

Investigation of Dynamic Behaviors of Asialoglycoprotein Receptors of Hepatocytes Using a Latex Probe Whose Surface Was Coated with Lactose-Carrying Polystyrene

Characteristic properties of oligosaccharide-substituted poly styrenes as a hepatocyte-specific culture substratum were investigated from the viewpoint of adsorption and recognition. X-ray photoelectron spectra sug gest that the adsorption of the polymer onto a polystyrene film occurred in near mono-molecular layer thickness of 10-25 Å in globular conformations. Distri bution and migration of asialoglycoprotein receptors on the surface of a hepato cyte was followed under a scanning electron microscope using a latex probe whose surface was coated with lactose-substituted polystyrene.

Nanosphere Coated with Lactosyl-Polystyrene Polymer as a Targeting Carrier to Hepatocytes

Polystyrene-latex nanosphere (PSL-NS, mean diameter: 85 nm) was coated with lactosyl-polystyrene polymer (PVLA, high affinity to hepatocytes) to evaluate its targeting characteristics to hepatocytes and PSL-NS surface hydrophilicity. Hepatocytes were adhered specifically with PVLA-coated dishes made of the same material as PSL-NS. Flow-cytometry investigation showed that PVLA-coated fluorescein-isothiocyanate (FITC)-PSL-NS was taken up by hepatocytes compared with noncoated FITC-PSL-NS as a control. These findings indicated PVLA-PSL-NS could target to hepatocytes. The surface of PVLA on PSL-NS had a higher hydrophilicity than polyethyleneglycol 6,000, Tween 80, poloxamer 407, and poloxamer 908, which indicated that PVLA-PSL-NS may avoid the reticuloendothelial system capture and have a long plasma duration after intravenous administration in vivo. Plasma coagulation can be prevented by the addition of polyvinylalcohol (0.1%) in PVLAPSL-NS solution when PVLA-PSL-NS was injected. We concluded that PVLA-PSL-...

Specific Interaction with Hepatocytes and Acute Toxicity of New Carrier Molecule Galactosyl-Polylysine

The new carrier molecules galactopyranosyl-glucuronyl-polylysines [Plys-Gal; molecular weights (MWs) of polylysine (Plys): 2,000, 10,000, and 25,000] were synthesized and their targeting characteristics to rats hepatocytes were evaluated. The maximum galactose substitution on Plys 2,000-Gal was found to be 8% of available sites. Adhesion of hepatocytes to Plys-Gal-coated dishes was inhibited by a lactosyl-polystyrene polymer (PVLA), which has been reported to be taken up via asialoglycoprotein receptors on hepatocytes. Plys 2,000-Gal had selective interaction with hepatocytes. After Plys-Gal was intravenously administered to mice (5, 10, and 20 mg/kg as Plys MW of 10,000 and 25,000), body weights were not different between mice administered Plys 10,000 or 25,000-Gal and saline as a control. It was suggested that the new carrier molecules Plys-Gals are very promising carriers for targeting drug to hepatocytes.