Release kinetics of gold nanoparticles from collagen microcapsules by total reflection X-ray fluorescence

One of the main challenges in nanotechnology based drug delivery systems is the design of novel materials for patient specific therapeutic efficacy. This can be achieved taking into account changes in the expression profiles of related proteins. Here, we focus on collagen type I micro-capsules for releasing molecules using a biological stimulus elicited by over-expressed collagenolytic matrix metalloproteinase I (MMPI). We have carried out label-free real time monitoring of the release kinetics of gold nanoparticles induced by MMPI in order to define the pore opening process by synchrotron radiation based total reflection X-ray fluorescence. Scanning electron and confocal laser scanning microcopy investigations have been carried out in order to further characterize the interaction between collagen micro-capsules and MMP1. The results enable to predict and to engineer the release time for drug molecules of different sizes. Moreover, the proposed label-free approach can be adopted for the visualization of pore formation and of release kinetics for nano-engineered polymeric capsules.