Effects of nanoparticle size and charge on interactions with self-assembled collagen

Hypothesis Insights into bone formation have suggested that the critical first step in the biomineralization process is the integration of small (nanometer dimension) mineral clusters into collagen fibers. Not only is such behavior of interest for understanding biomineralization but also should be important to nanotoxicology because collagen is a major component of structural tissues in the human body and accounts for more than 25% of the whole body protein content. Here, utilizing the current insights from biomineralization, we hypothesize that the binding affinity of nanoparticles to self-assembled collagen fibers is size and surface charge dependent. Experiments We developed a self-assembled collagen substrate compatible with Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), which is very sensitive to mechanical changes of the substrate as a consequence of nanoparticle binding. QCM-D experiments were conducted with both positively and negatively charged gold nanoparticles between 2 and 10 nm in size. Complementary ex situ imaging Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were used to confirm the QCM-D results. Findings We find that both positively and negatively charged nanoparticles of all sizes exhibited binding affinity for self-assembled collagen fibers. Furthermore, the smallest particles (2 nm) mechanically integrated with collagen fibers.