Biodegradable polymer nanoparticles (NPs) are of great interest for drug delivery systems due to their outstanding biocompatibility and easy preparation. The major challenge for these systems is to tailor their degradation and drug release to the application they are aimed for. It is reported that tuning the thermal properties (TPs) of polyesters via changing their crystallinity affects those properties but is also mostly accompanied by a variation of the hydrophilic / hydrophobic balance (HHB). This causes a knowledge gap on how the TPs of polymers affect their degradation and drug release without the influence of the HHB as third variable. To tackle that issue, we created polyester-based NPs with different TPs, where the HHB is kept constant. This presentation portrays our efforts to fill this lack of understanding on the example of stereocomplex based nanoparticles with tunable properties.

We generated different copolyesters with the same HHB as poly l- and d-lactic acid, as was proven via pyrene fluorescence. By blending we induced stereocomplexation of the bulk material of which the crystallinity and the TPs depended on the copolymer composition. This was shown by DSC and WAXS measurements. Consecutive NP formulation via nanoprecipitation led to the formation of spherical nanoparticles. AFM investigations of these nanoparticles revealed that the mechanical properties of the NPs depended on the copolymer composition which pointed towards varying degrees of crystallinity within the particles. This was further confirmed by in-dispersion Raman measurements. These measurements also revealed that the assembly time of the stereocomplexes prior to nanoprecipitation impacts crystallinity of the resulting NPs.

Our results, supported by various techniques, demonstrate clearly that it is possible to tune the TPs of polyesters and polyester based NPs while maintaining a constant HHB. Based on these findings we will perform experiments upon the degradation behavior, the drug uptake and the drug release of those polymer systems.

These polymeric NPs will lay the foundation for a new type of polymeric drug delivery systems, which allows tailoring the degradation and release kinetics.

This work is part of the Collaborative Research Center 1278: “Polytarget: Polymer-based nanoparticle libraries for targeted anti-inflammatory strategies” – project A06 which is funded by the Deutsche Forschungsgemeinschaft (DFG).