Elastase-like polypeptides mediated biomineralization of silica

Biomineralization is the process by which organisms prepare complex structural biominerals under physiological conditions. Biomimetic mineralization refers to the mineral manufacturing technology that simulates biominerals synthesis in vitro . It is one of the most important methods for the preparation of advanced inorganic materials, and the silica prepared by biosilicification has superior performance. Such biomimetic approaches allow silica to be synthesized under environmentally sustainable conditions at near-neutral pH and room temperature, and may ultimately be scalable for industrial use. The use of organic macromolecules for the controlled precipitation and deposition of inorganic materials is now an established area of modern chemistry. Such researches are generally inspired by the composite biominerals found in the natural world. The synthetic peptides known as R5, EctP1 and so on have been used widely in studies of peptide-driven silica condensation. Therefore, it is of great theoretical and practical significance to develop novel silica-forming peptides. Here, we reported a novel elastin-like polypeptide (ELPs120) with the function of biosilicification for the first time. The products of biosilicification mediated by ELPs120 were verified by the chemical analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The results confirmed ELPs120 had unique properties of silica precipitation activity when added to silicic acid. At the same time, the biomimetic biosilicification could occur in the buffers with pH ranging from 2.2 to 9.6, which was much wider than the peptides presently reported. Besides, even with lower concentrations, the time needed for the completion of biomimetic silicification was about 100 s, which was only 1/6 of that for other reported peptides. In addition, it can form silica in a concentration of 1472.60 μg/mL in the sodium chloride-barbiturate (no phosphate anion) buffer, suggesting that the biomimetic silicification of ELPs120 was not dependent on the phosphate anion. Due to the special self-purification characteristics of ELPs120, it is simpler to separate, purify and prepare. ELPs120 should have great potentials in the field of biomimetic silica preparation and other related fields. These unique properties suggest that there may exist a new mechanism for ELPs120 when mediating the biosilicification of silicic acid to form silica. Specifically, ELPs120 showed the silica precipitation activity when added to silicic acid solution under ambient conditions. It differs from the reported peptides (such as R5 and EctP1) with similar functions. Therefore, we speculated ELPs120 might have new mechanisms of biosilicification. It may be related to the existence of Lysine in its sequence, or to the unique intrinsically disordered structure of ELPs120. More in-depth studies are needed to confirm these possible molecular mechanisms. In addition, the silicon dioxide formed by ELPs120 and silicic acid is mainly spherical. The spherical sizes of the silica were regulated by the buffer type and pH. Perhaps the future works will focus on designing ELPs with different sequences to explore whether the silicon dioxide nanomaterials could form different morphology, such as tubular, rod or hollow spheres. As silica nanomaterilas with different morphology have great application potentials in sensing, enzyme immobilization, drug delivery and controlled release and other related fields.