Journal of Bioactive and Compatible Polymers

A relatively low-molecular weight sample of hyaluronic acid (HA) was chemically modified by means of a cross-linking reaction with water-soluble carbodiimide and L-lysine methyl ester to form a chemical hydrogel. FT-IR analysis performed on the precursors and on the cross-linked hydrogel indicated the formation of ester bonds between different HA molecules that led to an intermolecular cross-linking. Hydrogel swelling kinetics as well as equilibrium sorption properties were evaluated. A swelling ratio of 250 was observed after immersion in distilled water for 7 h. Rheological measurements by means of a plate–plate rheometer of the cross-linked sample showed non-Newtonian and pseudoplastic behavior, while the uncross-linked HA showed Newtonian behavior and a viscous characteristic. Morphological analysis of these microstructures by scanning electron microscopy indicated that the freeze-dried crosslinked hydrogel presents a more closed-pore structure and higher density of pores than the freeze-dried original HA.

Porous scaffolds that mimic both the structure and composition of natural bone were prepared. Nano-hydroxyapatite particles were first synthesized through deposition of minerals on self-assembled collagen fibrils. The porous scaffolds were then fabricated by loading the self-assembled nanohydroxyapatite–collagen composite powder into a cross-linked collagen–chitosan matrix. Porosity, mechanical properties, and composition of the scaffolds were studied. Biocompatibility was demonstrated by comparing in vitro osteoblastscultures, MTT assays, and alkaline phosphatase activity between the synthesized scaffolds and the control sample.

In this study Mitomycin-C-loaded alginate carriers were prepared as an alternative system in the postoperative chemotherapy in bladder cancer. Alginate was preferred because of its constructive properties and it was prepared in a cylindrical shape to facilitate the insertion of the carrier for in vivo studies. The alginate carriers were prepared as calcium alginate gel as well as crosslinking agents. In the preparation of the alginate carriers, precipitation medium concentration, cross-linker concentration, and Mitomycin-C/alginate ratio were changed to obtain drug attachment to the inner wall of bladder and/or optimum release rate of the agent. Due to the hydrogel structure of the alginate, the swelling behavior of the polymer was evaluated by gravimetric determinations in aqueous media periodically. Swelling ratios of the alginate carriers were changed from 30 to 65% based on precipitation medium, cross-linker concentration, and swelling medium pH. For prediction of the bioadhesion of the alginate carriers to the inner surface of bladder, in vitro bioadhesion tests were performed by using fresh bladders which were taken from New Zealand rabbits. It was observed that the in vitro Mitomycin-C release and bioadhesion values were significantly changed with changing swelling ratios.

New biodegradable polyurethanes containing azo-linked polymeric prodrugs of 5-aminosalicylic acid (5-ASA) in the main chain were prepared by reacting 1,6-Hexamethylenediisocyanate (HDI) with 3,30-azobis(6-hydroxy benzoic acid) (ABHB) and 5-[4-(hydroxyl phenyl) azo] salicylic acid (HPAS) as azo derivatives of 5-ASA. The polymers were characterized by FTIR and 1H-NMR spectroscopy. The hydrolysis of polyurethane containing azoderivatives of 5-ASA was carried out in cellophane membrane dialysis bags containing aqueous buffer solution (pH 1/4 8.5 and pH 1/4 1) at 37 C. Detection of the hydrolysis product by UV spectroscopy showed that ABHB and HPAS were released by the hydrolysis of the urethane bond in the polymer chain.