No abstract

A random terpolymer of L‐lactide (LL), ϵ‐caprolactone (CL) and glycolide (G) has been synthesized in bulk at 130 °C using stannous octoate as the coordination–insertion initiator. The terpolymer, poly(LL‐ran‐CL‐ran‐G), has been characterized by a combination of analytical techniques: GPC, 1H NMR, 13C NMR, DSC and TG. Molecular weight characterization by GPC shows a unimodal molecular weight distribution with values of M n = 1.01 × 105 g mol−1 and M w / M n = 2.17. Compositional and microstructural analysis by 1H NMR and 13C NMR, respectively, reveal a terpolymer composition of LL:CL:G = 74:15:11 (mol%) with a chain microstructure consistent with random monomer sequencing. This latter view is supported by the terpolymer temperature transitions (Tg and Tm) from DSC and the thermal decomposition profile from TG. The results and, in particular, the conclusion that it is a random rather than a statistical terpolymer are discussed in the light of current theories regarding the mechanism of this type of polymerization.© 2001 Society of Chemical Industry

Abstract. In the present study biodegradable microparticles of silk fibroin (SF)/starch blends were prepared by a simple water-in-oil emulsion solvent diffusion technique. SF/starch blended solution and ethyl acetate were used as water and oil phases, respectively. The influence of SF/starch ratios on characteristics of the blended microparticles was investigated. The SF conformation of microparticle matrices from FTIR analysis was changed from random coil to β-sheet form by blending with starch. The blended microparticles had lower dissolution in water than those of SF and starch microparticles. The 1/3 (w/w) SF/starch blended microparticles exhibited the lowest dissolution. The SF and starch microparticles showed irregular and deflated shapes, respectively. The blended microparticles were nearly spherical in shapes and smaller sizes. Thermal stability of the blended microparticles slightly increased with the starch blended ratio. The results suggested that SF conformational transition, thermal stability, morphology and dissolution of the blended microparticles can be adjusted by varying the blended ratio.

Linear (1-arm) and star-shaped (4-, 6-, and 16-arm) poly(D,L-lactide)s (PDLLs) were synthesized by ring-opening polymerization in bulk of D,L-lactide monomer. Hydroxyl end-group compounds and stannous octoate were used as the initiator and catalyst, respectively. The intrinsic viscosity and glass transition temperature (T g ) of the PDLLs decreased steadily as the branch arm number increased for similar molecular weights. However, the intrinsic viscosity and T g values of the linear PDLL were less than the star-shaped PDLL for similar each PDLL arm lengths. Ibuprofen, a poorly water soluble model drug was entrapped in the PDLL microspheres. All drug-loaded PDLL microspheres were prepared by the oil-in-water emulsion solvent evaporation method, were spherical in shape, and had a smooth surface with fine dispersibility. In vitro drug release behaviors indicated that the drug release from the microspheres with higher branch arm number was faster than from those with lower branch arm number. Moreover, the drug release from the star-shaped PDLL microspheres was slower than that of the linear PDLL microspheres for similar PDLL arm lengths. The drug release behavior could be adjusted through both the branch arm number and arm length of PDLL.

No abstract

No abstract

No abstract

Silk fibroin (SF) microspheres containing a model drug were prepared by a simple water-in-oil emulsification-diffusion method. Aqueous SF solution and ethyl acetate were used as water and oil phases, respectively. Methylene Blue was used as a water-soluble model drug. Effect of drug content on microsphere characteristics, drug loading efficiency and drug release behavior was determined. Scanning electron microscopy revealed that drug-loaded SF microspheres were spherical in shape with a smooth surface. The SF microspheres showed predominant random coil SF conformation. All drug loading efficiencies were approximately 50%. An increase in drug/SF ratio could lead to an increase in %drug release and surface erosion after the drug release test. Drug release from SF microspheres is due to SF matrix swelling and surface erosion processes.