Degree Of Enzymatic Degradation Research Articles

Macromolecular effects upon enzymatic degradation of chitosan in solution

Macromolecular effects were revealed in the course of enzymatic degradation of chitosan in an acetic acid solution under the action of hyaluronidase, a nonspecific enzyme. It was shown that the concentration of chitosan in the initial solution determines its supramolecular organization and, hence, the degree of enzymatic degradation.

Biodegradable Network Polyesters from Gluconolactone and Citric Acid

This paper presents biodegradable polyesters prepared from gluconolactone (G) and citric acid (C) with various molar ratios of G to C, 1/4, 1/3, 1/2, 1/1, 2/1, 3/1, and 4/1. Corresponding polyesters were named as GC14, GC13, GC12, GC11, GC21, GC31, and GC41, respectively. Prepolymers, prepared at 165 °C by a melt polycondensation, were cast from tetrahydrofuran solution and postpolymerized at 180 °C for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The polyesters obtained were characterized by infrared spectroscopy, wide-angle X-ray diffraction analysis, density measurement, differential scanning calorimetry (DSC), dynamic mechanical analysis, thermomechanical analysis (TMA), and tensile test. The degree of reaction was estimated from the ratio between absorbance due to the stretching vibration of the hydroxyl group and that of the methylene group. Enzymatic degradability was performed at 37 °C in a buffer solution with Rhizopus delemar lipase. The degree of enzymatic degradation was decreased with decreasing C content in the polymers as follows: GC14 > GC13 > GC12 > GC11 > GC21 ≈ GC31 ≈ GC41 ≈ 0, which corresponded to the decrease of the average molecular weight between cross-linked sites. Two transition temperatures were measured on thermograms in DSC and TMA curves. The higher transition temperature was ascribed to the release of restricted motion in the molecule pinned by the cross-linked sites. The lower transition temperature was attributed to the transition due to the segmental molecular motion of the ester linkage. Large Young's modulus and tensile strength were obtained in the dried state of GC31 and GC21, respectively. Water absorbed in the polymer matrix was worked as a plasticizer, and largely depressed Young's modulus and tensile strength were measured for the sample in water.

In vitro and in vivo degradation study on novel blends composed of polyphosphazene and polyester or polyanhydride

AbstractPoly[bis(glycine ethyl ester)phosphazene] (PGP) was blended with poly(D,L‐lactide‐co‐glycolide) (80:20 by mole) (PLGA) and poly[sebacic anhydride‐co‐trimellitylimidoglycine)‐block‐poly(ethylene glycol)] (30:50:20 by mole) (PSTP) in various ratios using a solvent‐mixing technique. The in vitro degradation of polymer blends was examined by treatment in distilled water with or without lipase at 37 °C; the degradation rate of the blends could be regulated by adjusting the composition. PGP/PLGA (70:30 by wt) slabs took 120 days to disappear completely, while PGP/PSTP (70:30 by wt) needed only 20 days. Furthermore, Rhizopus delemer lipase showed the strongest acceleration activity on PGP/PLGA blends. The degree of enzymatic degradation was proportional to the percentage of PLGA in the blend. For comparison, the in vivo degradation of polymer blends was investigated by implanting them subcutaneously in the back of mice, some difference in degradation being observed.© 2002 Society of Chemical Industry

Synthesis of low-molecular-weight copoly( l-lactic acid/ɛ-caprolactone) by direct copolycondensation in the absence of catalysts, and enzymatic degradation of the polymers

Low-molecular weight copolymers ofl-lactic acid (LA) and ɛ-caprolactone (CL) were synthesized by direct copolycondensation without catalysts at 200°C under a nitrogen atmosphere. The reaction proceeds by direct condensation between linear LA and linear 6-hydroxycaproic acid produced by hydrolysis of the cyclic CL. These copolymers were characterized with respect to molecular weight by gel permeation chromatography, composition by1H nuclear magnetic resonance (n.m.r.) spectroscopy, sequence by13C n.m.r. spectroscopy, and crystallinities by both differential scanning calorimetry and X-ray measurement. The morphology of copoly (LA/CL) can be subdivided into three states as a function of monomer composition according to the differences inTg and crystallinity, e.g. solid (0–15 mol% CL composition ranges), paste (30–70 mol% CL composition ranges) and wax (85–100 mol% CL composition ranges). Thein vitro degradation of the copolymer was examined by treatment in buffer solutions with and without enzymes and, as a result,Rhizopus delemer lipase showed the strongest degradation activity. In this case, the degree of enzymatic degradation is strongly dependent on the morphology of copoly(LA/CL), in which the pasty copolymer is much more subject to hydrolysis than the solid and waxy copolymers. For comparison thein vivo degradation of the copolymer was investigated by implanting it subcutaneously in the back of rats.