Polymers and Fiber Surfaces

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The starting point for the preparation of graded implants are fiber mats prepared by electrospinning of polycaprolacton (PCL). Aim of this project is, to modify the fiber mats in a way that they will be suited for the functionalization with drug release systems. To do so, the fiber mats are treated by plasma, coated with polydopamin (pDA) or with chitosan-graft-polycaprolacton (Chi-g-PCL). In the last grant period these three methods have been proven to be suitable to functionalize fiber mats with drug release systeme and to create spatial gradients. However, the different modifications differ in the results obtained. It was found that more nanoporous silica nanoparticles as drug release system could be adsorbed by the pDA modified fiber mats compared to those modified with Chi-g-PCL. However, less signaling protein was released from polymeric drug delivery systems on fiber mats modified with pDA compared to fiber mats modified with Chi-g-PCL. These differences and with that the advantages and disadvantages of the modification methods shall be investigated systematically. In addition they shall be ascribed to chemical and physical surface properties. To do so the differently modified fiber mats will be functionalized with the same drug release system (supplied by subproject TP5) and the release kinetics will be investigated (together with subproject TP6). The results will be correlated with the surface potential (zeta-Potential) of the modified fiber mats, which can be determined by electro-kinetic measurements. Besides the electrostatic interactions which can be quantified using the zeta potentials of the fiber surfaces, the drug release system and the proteins, also hydrophobic interactions will be taken into account. For this, protein adsorption measurements with model proteins will be carried out. A thorough understanding auf the electrostatic and hydrophobic interactions will enable a knowledge-based design of an optimal modification of the fiber mats. This will also will allow a transfer of the method to other biomedical applications. First tests to transfer the coating methods to other substrates will be carried out. Blending of PCL with different PCL-block- and graft-copolymers will be prepared and electro spun as blend. In this way, further methods to introduce further chemical functionalities at the surface which can be used to improve cell adhesion if necessary. Blending with photo-reactive copolymers shall be used to adjust the properties of the fibers (together with subproject TP3).