Poly(vinyl alcohol) (PVA) of various molecular weight (MW=10,560-116,600) was successfully labeled with fluorescein isothiocyanate isomer I (FITC) according to the method of de Belder and Granath. A high-performance size-exclusion chromatographic procedure was developed for the quantitative analysis of FITC-labeled poly(vinyl alcohol) (F-PVA) in biological samples. F-PVA (80 K) disappeared slowly from the blood circulation according to the first-order kinetics (t1/2=7 h) after intravenous injection to rats. A dose-independent behavior of F-PVA (80 K) was observed in the blood circulation, in the tissue distribution and in the urinary and fecal excretions. This suggested that PVAs are eliminated exclusively by the mechanisms that do not involve saturable transport processes. Furthermore, it was found that PVAs are very stable in the body because no degradation product was detected in the urine and feces. 125I-labeled poly(vinyl alcohol) (125I-PVA) was prepared by introducing tyramine residues to the hydroxyl groups of PVA molecules by the 1,1'-cabonyldiimidazole (CDI) activation method. 125I-PVA (80 K) was retained in the blood circulation for several days after intravenous injection to mice. Although the tissue distribution of PVAs was small, a significant accumulation into the liver and the spleen was observed. Fluorescence microscopic examination of paraffin section of the liver revealed that F-PVA (80 K) was endocytosed by the liver parenchymal cells. 125I-PVA (80 K) captured by liver was slowly transported via the bile canaliculi and gall bladder to the intestine and excreted in the feces. It was suggested, therefore, a long time is necessary for 125I-PVA (80 K) to be excreted perfectly from the body.

Aconityl-doxorubicin (ADOX) was synthesized by the modified method of Shen and Ryser. Two isomers of cis-ADOX (cis-configuration) and trans-ADOX (trans-configuration) were generated in the reaction of DOX and cis-aconitic anhydride. These products were separated completely by using HPLC and analyzed by TOF-MS spectroscopy and 1 H-and 13 C-NMR experiments. The yields of cis-ADOX and trans-ADOX were 36.3 and 44.8%, respectively. The free g g-carboxylic group of ADOX molecule was coupled to poly(vinyl alcohol) (PVA) via ethylenediamine spacer, resulting the macromolecular conjugates of PVA-cis-ADOX and PVA-trans-ADOX, respectively. The DOX content of the conjugates estimated by the hydrolysis method detected the aglycone of DOX which can be estimated as the PVA-bound DOX selectively was 4.4 w/w% which was similar to 4.6 w/w% by the ordinary UV method. Both PVA-cis-ADOX and PVA-trans-ADOX were very stable at neutral pH, but the release of DOX was increased markedly under acidic conditions. Half-life of the release of DOX from PVA-cis-ADOX at pH 5.0 was 3 h which was 4.7-fold shorter than that from PVA-trans-ADOX (14 h). The cytotoxicities of PVA-cis-ADOX and PVA-trans-ADOX were evaluated by using J774.1 cells employing a [ 3 H]uridine incorporation assay as a measure of RNA synthesis. A significant difference in antitumor activity between PVA-cis-ADOX and PVA-trans-ADOX was observed where the former was much active than the later. It was suggested that the conjugate enters the cells and reaches the lysosomal/endosomal compartment, and that the aconityl spacer releases DOX from the conjugate in the acidic compartment of lysosomes/endosomes due to the participation of a free carboxylic group.

Paclitaxel (PTX) is an anti-microtubule agent isolated from the trunk bark of the Pacific Yew tree, Taxus brevifolia.1) It has been widely used as an anti-neoplastic agent for a variety of human cancers including breast, ovarian, nonsmall cell lung, head and neck cancers, leukemia, and melanoma. [2][3][4][5][6] PTX is a highly hydrophobic drug and is hardly soluble in water (water solubility Ͻ0.3 mg/ml).7) Because of its poor solubility in water and many other acceptable pharmaceutical solvents, specific emulsionizers, such as Cremophor EL ® , are used to formulate PTX in commercial injection solutions. However, serious hypersensitivity reactions have been reported in some individuals since the content of Cremophor EL ® used in the PTX formulation is significantly higher than in any other marketed drug. 8,9) Side effects of PTX formulation include nausea and vomiting, diarrhea, mucositis, myelosuppression, cardiotoxicity and neurotoxicity. 10,11) In addition, Cremophor EL ® is known to leach phthalate plasticizers from polyvinylchloride bags and intravenous tubing.12) Therefore, alternative dosage forms for the PTX administration need to be developed to reduce the undesirable side effects induced by using Cremophor EL ® . In recent years the use of water-soluble polymers as drug delivery systems has been received increasing attention. Li et al. 13) and Greenwald et al. 14) reported the conjugation of polyethylene glycol (PEG) to the 2Ј-position of PTX through a spacer succinyl group. They demonstrated that PEG may be used as an effective solubilizing carrier for PTX. Poly-Lglutamic acid was also used to make a water-soluble PTX conjugate. [15][16][17] It was demonstrated that the poly-(L-glutamic acid)-paclitaxel conjugate was more effective than standard PTX. On the other hand, Sugahara et al. constructed the PTX delivery system using amino acid linkers in the conjugation of PTX with carboxymethyldextran. 18)The consequence of attachment of low molecular weight drugs to macromolecular carriers alters their rate of excretion from the body, changes their toxicity and immunogenicity, and limits their uptake by cells via endocytosis, thus providing the opportunity to direct the drug to the particular cell type where its activity is needed. 19) In addition, these macromolecular conjugates can accumulate in solid tumors due to the enhanced microvasculature of tumor tissue. 20,21) This phenomenon has been termed enhanced permeability and retention in relation to tumor targeting (EPR-phenomenon). [22][23][24] Poly(vinyl alcohol) (PVA) is a polymer which is synthesized by polymerizing not a vinyl alcohol monomer but a vinyl acetate monomer. This monomer is polymerized in to poly(vinyl acetate) and then hydrolyzed to produce PVA. PVA's biocompatibility makes it an excellent material for use in medical applications such as soft contact lenses. Recently, PVA has been used for long-term implants, including a bioartificial pancreas, artificial cartilage, nonadhesive film, and esophagus or scleral buckling material. 25) Fur...