Biomimetic Silicification of Fibrous Chitin from Diatoms

Poly-N-acetyl-d-glucosamine (p-GlcNAc, chitin) is a biopolymer found in various organisms and in forms such as sheets, membranes, and fibers. Its presence in numerous calcium-based biominerals is well-known. Recently, chitin was even found in silica-based biominerals. While it is well-established that various proteins and even long-chain polyamines are involved in silica biomineralization events, the role of polysaccharides is rather poorly understood. Furthermore, silica-chitin nanocomposites and silica-coated chitin constructs are increasingly important, e.g., in materials science and for biomedical applications. Therefore, we have investigated the interaction between p-GlcNAc in fibers and silicic acid/silica species in vitro, using 13C and 29Si NMR as well as Raman spectroscopy, in combination with microscopic techniques. Furthermore, the kinetics of silica condensation in the presence/absence of p-GlcNAc fibers could be analyzed using the molybdenum blue test.