Protein Interactions with Polylactide-Polyglycolide Particles and Scaffolds

Cytotoxicity of poly(96L/4D-lactide): the influence of degradation and sterilization

The cytotoxicity of poly(96L/4D-lactide) (PLA96), and of its accumulated degradation products, was investigated following different sterilization methods and pre-determined heat-accelerated degradation intervals. PLA96 samples sterilized by either steam, ethylene oxide, or gamma irradiation were left untreated (S0 samples), or were degraded for 30 h or 60 h (S30 and S60 samples) at 90 degrees C in water. Extracts of the samples and of the remaining degradation fluids (F30 and F60) were prepared. The toxicity of both unfiltered and filtered extracts was analyzed in a cell growth inhibition (CGI) assay and a lactate dehydrogenase (LDH) leakage assay. Physical analysis of the extracted samples and of the degradation fluids also was performed. The S0 extracts demonstrated no significant CGI. The CGI of the S30 extracts ranged from 37 to 78%, whereas the CGI of the S60 extracts ranged from 6 to 33%. The CGI of the F30 extracts ranged from 19 to 38% and the CGI of the F60 extracts was 98 to 123%. The LDH leakage assay only showed a high response to the unfiltered F60 extracts. Neither sterilization nor filtration appeared to influence the cytotoxicity of the extracts. Particle accumulation, however, might affect cell membrane permeability resulting in LDH leakage. The results of this study suggest that the cytotoxicity of PLA96 is related to the pH and possibly the osmolarity of the tested extracts. The pH and osmolarity, in turn, may depend on variations in the amounts of solubilized lactic acid and oligomers. These variations appear to result from degradation stage-dependent differences in crystallinity, molecular weight and molecular weight distribution of the PLA96 samples.

The future of biodegradable osteosyntheses

In the last 3 decades, much progress has been made in the development of biodegradable osteosyntheses. Despite this progress, these materials are still only used in small numbers, and the scope of their application has been limited. The limitations of biodegradable osteosyntheses mainly are related to problems with their mechanical properties and, in particular, biocompatibility. These problems need to be solved so that biodegradable osteosyntheses can perform up to their full potential and thus, eventually, make their general clinical application routine. This paper presents a historical perspective on the development of biodegradable osteosyntheses, discusses the successful developmental achievements and the still-existing problems, and gives a perspective on their future development.

Porous biodegradable polymeric scaffolds prepared by thermally induced phase separation

Poly(L-lactic acid) and its copolymers with D-lactic and glycolic acid were used to fabricate various porous biodegradable scaffolds suitable for tissue engineering and drug delivery based on a thermally induced phase separation (TIPS) technique. A variety of parameters involved in TIPS process, such as types of polymers, polymer concentration, solvent/nonsolvent ratio, and quenching temperature, were examined in detail to produce a wide array of micro- and macroporous structures. A mixture of dioxane and water was used for a binary composition of solvent and nonsolvent, respectively. In particular, the coarsening effect of pore enlargement affected by controlling the quenching temperature was used for the generation of a macroporous open cellular structure with pore diameters above 100 microm. The use of amorphous polymers with a slow cooling rate resulted in a macroporous open cellular structure, whereas that of semicrystalline polymers with a fast cooling rate generated a microporous closed cellular structure. The fabricated porous devices loaded with recombinant human growth hormone (rhGH) were tested for the controlled delivery of rhGH, as a potential additional means to cell delivery.