Low molecular weight poly(lactic acid) microparticles for controlled release of the herbicide metazachlor: Preparation, morphology, and release kinetics

The preemergence chloroacetamide herbicide metazachlor was encapsulated in biodegradable low molecular weight poly(lactic acid) micro- and submicroparticles, and its release to the water environment was investigated. Three series of particles, S, M, and L, varying in their size (from 0.6 to 8 μm) and with various initial amounts of the active agent (5%, 10%, 20%, 30% w/w) were prepared by the oil-in-water solvent evaporation technique with gelatin as biodegradable surfactant. The encapsulation efficiencies reached were about 60% and appeared to be lower for smaller particles. Generally, it was found that the rate of herbicide release decreased with increasing size of particles. After 30 days the portions of the herbicide released for its highest loading (30% w/w) were 92%, 56%, and 34% for about 0.6, 0.8, and 8 μm particles, respectively. The release rates were also lower for lower herbicide loadings. Metazachlor release from larger particles tended to be a diffusion-controlled process, while for smaller particles the kinetics was strongly influenced by an initial burst release. © 2012 American Chemical Society

Preparation and characterisation of a new double-sided bio-artificial material prepared by casting of poly(vinyl alcohol) on collagen

A new double-sided bio-artificial polymer material prepared by casting of poly(vinyl alcohol) (PVA) on collagen (COLL) was obtained. The single components were blended with lactic acid and glutaraldehyde as plasticiser and crosslinker agents, respectively, to change and characterise structure of both the polymers. Differential scanning calorimetry, dynamic mechanical analysis, tensile test, tear resistance test, scratch test and Fourier transform infrared spectroscopy were chosen to characterise all the prepared materials. The results showed that the additives led to the decrease of glass transition temperature, melting temperature and crystallinity with respect to raw materials. The new bio-artificial material revealed tough behaviour with yield stress, with less by half tensile strength compared to neat materials and with the strain of PVA (> 100 %). Both PVA and COLL blends and the new bio-artificial material exhibited viscoelastic features useful for being used in contact with living organism