Controlled Drug Release from Laser Treated Polymeric Carrier.

In this study, we present the effect of laser treatment on polymeric poly(lactic acid) drug carrier films. Our goal was to demonstrate the control of the drug-release kinetics of a polymeric carrier as a function of total absorbed laser energy. The controlled drug release kinetic was achieved by modifying the amorphous polymeric carrier's molecular weight via low energy density laser-exposure. According to gel permeation chromatography results, the decrease of molecular weight correlates with an increasing laser-shot number and shows a distinct saturation-like behavior. The dissolution test also suggests the presence of such dependency, as the rate and amount of caffeine released from the sample shows an increasing tendency up to 2000 laser shots. This fact proves that the laser treatment modifies the drug release. The approach presented here may complement other methods used for controlled drug release in various medical and pharmacological applications.

Development of Poly (Lactide Acid) Foams with Thermally Expandable Microspheres.

This study presents the investigation of different content of thermally expandable microsphere (EMS) type of a physical blowing agent added to polylactic acid (PLA). The effects of the different doses of EMS, processing temperatures, and d-lactide content of the polylactic acid were analyzed for foam properties and structures. We characterized the different PLAs and the physical blowing agent with different testing methods (gel permeation chromatography, rotational rheometry, isothermal thermogravimetric analysis, and thermomechanical analysis). The amounts of the foaming agent were 0.5, 1, 2, 4, 8 wt%, and processing temperatures were 190 °C, 210 °C, and 230 °C. The foam structures were produced by twin-screw extrusion. We used scanning electron microscopy to examine the cell structure of the foams produced, and carried out morphological and mechanical tests as well. The result of extrusion foaming of PLA using different amounts of EMS shows that an exponentially decreasing tendency of density reduction can be achieved, described by the following equation, ρ(x)=1.062∙e-x7.038+0.03 (R2 = 0.947) at 190 °C. With increasing processing temperature, density decreases at a lower rate, due to the effect that the microspheres are unable to hold the pentane gas within the polymer shell structure. The d-lactide content of the PLAs does not have a significant effect on the density of the produced foam structures.

Water-Assisted Production of Thermoplastic Nanocomposites: A Review.

Water-assisted, or more generally liquid-mediated, melt compounding of nanocomposites is basically a combination of solution-assisted and traditional melt mixing methods. It is an emerging technique to overcome several disadvantages of the above two. Water or aqueous liquids with additives, do not work merely as temporary carrier materials of suitable nanofillers. During batchwise and continuous compounding, these liquids are fully or partly evaporated. In the latter case, the residual liquid is working as a plasticizer. This processing technique contributes to a better dispersion of the nanofillers and affects markedly the morphology and properties of the resulting nanocomposites. A survey is given below on the present praxis and possible future developments of water-assisted melt mixing techniques for the production of thermoplastic nanocomposites.