(381b) Nacre-Inspired Composite Gels for Biomedical Applications

Nacre (or mother of pearl) is found in the inner shell layer of certain molluscs & has a complex hierarchical structure made of hard (CaCO₃) and soft (proteins) components. Layers of hexagonal plates of aragonite, which is a crystalline form of CaCO₃ are held together by a matrix of proteins, in a manner that resembles a “brick and mortar” structure. Incorporation of the soft protein in between the hard aragonite plates imparts superior mechanical strength to nacre, which is three to nine time higher than that of pure aragonite. This ingenious combination of materials result in remarkable properties, such as, resistance against fracture, high pressure absorption, prevention of crack propagation, and being incredibly light weight.

Inspired by these features, we have developed robust, flexible materials with self-adaptive and self-healing properties. Polymer hydrogels were incorporated with functional nanoparticles to produce composites with unique physicochemical and mechanical properties. 3D printing was utilized as an effective technique to combine the nanoparticles with polymer gels, with greater dimension control. Moulds with hexagonal wells were printed and filled with a “hard” component comprising of the nanoparticles in the polymer gel. The compressibility of these composites was customized using a crosslinking agent. These hexagonal templated materials were then arranged into layered structures, which were held together by a “soft”, flexible polymer matrix. The physical and mechanical properties of these composites could be greatly varied by changing the polymer concentration of the soft matrix. Due to 3D printing, a wide range of dimensions could be achieved for making such composites. Techniques were also developed that allowed 3D printing of the nanoparticles directly onto polymer gels, according to desired patterns. These novel composites were extensively characterized (TEM, SEM/EDX, FTIR, tensile strength, compressibility, and other techniques to be discussed in the presentation) and displayed enhanced capabilities in mechanical strength, self-adaptation to environmental stresses and in self-healing ability. These features, together with biocompatibility, allow for a myriad of biomedical applications.