The development of systems for targeted drug delivery has been a field of growing interest. Among several advantages of this technique, particular attention should be paid to the possibility of reducing the necessary amount of active components due to the controllable release at targeted locations inside the human body. Therefore, unwanted side effects occurring with commercial medication may be prevented.

To control the drug release mode, knowledge about the degradation behavior of the delivery system is essential since the degradation mode mainly regulates the drug release of the whole system. For this purpose, many parameters such as thermal properties, crystallinity and hydrophilicity of the used polymers must be taken into consideration. However, one major issue in designing proper delivery systems is the tight connection of physical and chemical properties that make isolating specific parameter influences on the degradation behavior almost impossible.

The aim of this study is to investigate the degradation behavior of polymeric nanoparticles made of polylactic acid (PLA) under enzymatic degradation via hydrolysis using Proteinase K. Since there are two chirality forms of PLA that are able to form stereo complexes, we investigate the degradation behavior of nanoparticles assembled by these stereo complexes respectively. From previous work we know that the crystallinity can be altered by copolymerization with the isomer poly(3-ethylglycolide) (PEtGly) without changing the thermal properties or hydrophilicity in comparison to PLA, which we use here.

Investigated stereo complex nanoparticles produced by nanoprecipitation have a diameter of about 100 nm and are copolymerised with either 0, 5, 10 or 20 mol% EtGly content. Our first results showed their higher than expected resistance to enzymatic hydrolysis, irrespective to the amount of EtGly. Nevertheless, we observed the trend that particles with a higher EtGly content, and therefore a lower crystallinity, apparently degrade faster.

Jenny Hemstedt