Phase transfer and characterization of poly(ε-caprolactone) and poly(L-lactide) microspheres

• Published in: Journal of biomaterials science. Polymer ed. Vol. 11; no. 5; pp. 459 - 480
• Main Authors: Gadzinowski, Mariusz, Slomkowski, Stanislaw, Elaïssari, Abdelhamid, Pichot, Christian
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis Group 01.01.2000; Taylor & Francis
• Subjects: Biocompatible Materials - chemistry; BIODEGRADABLE MICROSPHERES; Chemical Sciences; Hydrogen-Ion Concentration; Kinetics; Life Sciences; Material chemistry; Microscopy, Electron, Scanning; Microspheres; Particle Size; Pharmaceutical sciences; POLYCAPROLACTONE; Polyesters - chemistry; POLYLACTIDE; Polymers; Surface-Active Agents
• ISSN: 0920-5063; 1568-5624
• DOI: 10.1163/156856200743814

A method suitable for transfer of poly(ε-caprolactone) and poly(L-lactide) microspheres (synthesized by pseudoanionic dispersion polymerization of ε-caprolactone and L-lactide in heptane1,4-dioxane mixed solvent) from heptane to water was developed. This method consists of treating the microspheres with KOH-ethanol in the presence of surfactants (nonionic Triton X-405, anionic sodium dodecyl sulfate (SDS), and zwitterionic ammonium sulfobetaine-2 (ASB)). Partial hydrolysis of polyesters results in the formation of hydroxyl and carboxyl groups in the surface layer of microspheres and enhances their stability in water-based media. Minimal concentrations of surfactants, needed to obtain stable suspensions of particles, were equal to 3 × 10 -2 , and 6 × 10 -2 , and 3 × 10 -2 mol l -1 for Triton X-405, SDS, and ASB, respectively. In the case of poly(ε-caprolactone) microspheres, suspensions in water were stable for all three surfactants for pH values ranging from 3 to 11. Suspensions of poly(L-lactide) were stable in the same range of pH values only for ASB. Surface charge density determined by electrophoretic mobility varied for poly(ε-caprolactone) microspheres from 2.6 × 10 -7 to 8.9 × 10 -7 mol m -2 , for particles stabilized with Triton X-405 and ASB, respectively. In the case of poly(L-lactide) microspheres, surface charge density varied from 3.9 × 10-7 (stabilizer: Triton X-405) to 7.4 × 10 -7 mol m -2 (stabilizer: ASB). Carboxyl groups located in the surface layer of poly(L-lactide) microspheres were used for covalent immobilization of 6-aminoquinoline, a fluorophore with an amino group. Maximum surface concentration of immobilized 6-aminoquinoline was equal to 1.9 × 10 -6 mol m -2 . Poly(ε-caprolactone) microspheres transferred into water were loaded with ethyl salicylate. Loading up to 38% (w/w) was obtained.