Biomedical subjects

S Ponsart

Publications and source records attributed to S Ponsart.

3 recordsLinked to original sources

PubMed2001

Biodegradation of [(3)H]poly(epsilon-caprolactone) in the presence of active sludge extracts.

Poly(epsilon-caprolactone), PCL, is a commercial biodegradable and biocompatible polyester that can be bioassimilated by outdoor microorganisms. For biomedical and environmental applications, monitoring the fate of degradation products in vivo or under environmental conditions is one of the critical steps to evaluate degradation characteristics. [(3)H] radiolabeling is the best method to monitor the fate of degradable polymer chains in contact with complex living systems and to show bioassimilation. Therefore, tritiated PCL was synthesized by chemical modification using anionic activation by reaction with lithium diisopropylamide. The resulting radioactive polymer was characterized and allowed to degrade at 37 degrees C under aerobic conditions in the presence of active sludge. Comparison was made with abiotic hydrolytic degradation in pH = 7.4, 0.13 M phosphate buffer at 37 degrees C. Water-soluble degradation products were assessed by measuring radioactivity in the solution phase. It was shown that biodegradation of PCL started after a few hours and proceeded up to the ultimate stage over ca. 72 days, giving tritiated water (80-90%) and biomass. Radioactivity detection appeared much more sensitive than measurement of CO(2) production or consumption to monitor degradation phenomena. In particular, it showed that the onset of biodegradation occurs earlier than that reported using respirometry.

Bacteria, Aerobic↗

PubMed2000

A novel route to poly(epsilon-caprolactone)-based copolymers via anionic derivatization.

Poly(epsilon-caprolactone) (PCL) is known to biodegrade under composting or water sewage plant conditions. However, as compared with poly(alpha-hydroxy acids) derived from lactic and glycolic acids, PCL is much more resistant to chemical hydrolysis and is achiral, a feature that limits very much the possibility of property modulation through the configurational structure of polymer chains. For the sake of enlarging the family of PCL-type polymers, a novel method is proposed which is based on the anionic activation of PCL chain by the removal of a proton from the methylene group in alpha-position of the ester carbonyl present in the main chain, using a nonnucleophilic base such as lithium diisopropyl amide (LDA). This activation leads to a polycarbanion onto which various electrophile groups can be attached. The feasibility of the process was first shown on poly(methyl acrylate), (PMA), whose polyacrylic main chain is resistant to strong bases. The PMA polycarbanion was modified by various electrophiles, namely benzaldehyde, naphthoyl chloride, benzyl chloroformate, and iodomethane. In a second stage, the same reactions were performed successfully on PCL. The degree of substitution depended on the experimental conditions. PCL underwent main chain degradation during the formation of the polycarbanion whereas the reaction with the electrophiles did not cause any further main chain cleavages. The degradation of PCL chains can be limited enough to give access to novel functional PCL polymers.

Algorithms↗

PubMedDate not supplied

beta-Glucuronidase activity following complex coacervation and spray drying microencapsulation.

The objective was to develop a microencapsulation process suitable for the controlled release of an active protein drug. beta-glucuronidase was selected as a model protein and a combination of complex coacervation (gelatin/sodium alginate, gelatin/acacia and albumin/acacia) and spray drying was investigated. Coacervates were either spray dried or glutaraldehyde crosslinked to form microcapsules. Polyvinylpyrrolidone (PVP) and polyethylene glycol were investigated as potential coacervate enhancers and stabilizers. beta-glucuronidase/polymer mixtures were spray dried to determine any polymer protective effects on protein activity. A BUCHI 190 Spray Drier was used, beta-glucuronidase activity was determined using a Sigma Kit and microcapsule particle size was measured by Accusizer analysis (light blockage). All non-crosslinked coacervates investigated, with the exceptions of albumin/acacia and albumin/acacia/beta-glucuronidase/PVP, were unsuitable for spray drying as they rapidly phase separated and blocked the spray drier nozzle. beta-glucuronidase activity in the albumin/acacia coacervates approximated to 99% prior to and 80% following spray drying. This can be compared to activities of approximately 30% and 68% when spray dried alone and with albumin, respectively, and of 18% in albumin/acacia microcapsules crosslinked with glutaraldehyde. Microcapsule particle size was affected by coacervation pH, additives and spray drying. In vitro beta-glucuronidase release was biphasic, with an initial burst release followed by a zero order release phase and continued over the 12 day study period. In conclusion, the spray drying albumin/acacia/PVP method described is useful for the preparation and collection of controlled release microcapsules with minimal loss of beta-glucuronidase activity.

Acacia↗