Rheological and Morphological Investigation of Renaturated Collagen Nanogels in Physiological-like Solution Conditions1

Collagen is the most abundant protein in mammals comprising 70% of skin, tendons and bones. Denaturated (or renaturated) collagen is also referred to as gelatin. Gelatin gels are made up of a 3D network of renaturated collagen nanofibres and are one of the most frequently used protein-based materials in a wide range of industrial applications; for this reason they attract a strong interest from the international scientific and industrial communities. Applications of gelatin gels in biomedical engineering, although widely spread, are still hampered by the apparent instability of the gelatin network under physiological conditions. This matter gets further complicated by the confusion surrounding the usage of different types of gelatin as well as the, usually overseen, potential effects of a variety of different experimental parameters on the final gel properties. Here we present the first of a series of detailed studies in which we begin to investigate the rheological and structural properties of gelatin type B in an increasingly more biologically relevant and complex solution-environment. Protein concentration, pH, ionic strength and environmental temperature can strongly affect the gel formation capacity of collagen. Here we begin to investigate the effects of the above mentioned parameters on nanogels of gelatin type B. Biomechanical temperature ramp step tests were carried out in order to determine the melting (or formation) temperatures of the gels whilst electron microscopy probed the structural properties of the underlying nanostructures. We believe that systematic investigations can lead us to gain a deeper insight into these popular biomaterials with the view of widening and further facilitating their applications in biomedical engineering.