类弹性蛋白多肽介导的二氧化硅仿生矿化

Elastase-like polypeptides mediated biomineralization of silica

仿生矿化是目前先进无机材料制备的重要手段之一,经仿生硅化所制备的二氧化硅具有更优越的性能.因此,开发能介导仿生硅化制备新型二氧化硅材料的多肽具有重要理论和应用价值.本文报道了一种具有仿生硅化能力的新型多肽——类弹性蛋白多肽(ELPs120).经化学测定、红外分析、元素分析及电子显微镜等表征手段证实ELPs120具有独特的仿生硅化性能:ELPs120能在pH2.2~9.6的缓冲液中介导硅酸仿生硅化;且在浓度更低的条件下,其仿生硅化所需时间更短(约100 s),仅为其他多肽所需时间的1/6.此外,它能在盐酸-巴比妥钠(无磷酸根离子)缓冲液中形成浓度为1472.60μg/mL的二氧化硅,表明其仿生硅化不依赖于磷酸根.上述特性暗示ELPs120可能存在介导硅酸仿生硅化的新机制.由ELPs120特殊的自分离特性,其制备更为简单,在二氧化硅仿生制备领域应用潜力巨大.

Biomineralization is the process by which organisms prepare complex structural biominerals under physiological condi- tions. 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 environ- mentally 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 pep- tides. Here, we reported a novel elastin-like polypeptide （ELPs 120） with the function of biosilicification for the first time. The products of biosilicification mediated by ELPs 120 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 ELPsl20 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 gg/mL in the sodium chloride-barbiturate （no phosphate anion） buffer, suggesting that the bio- mimetic silicification of ELPsl20 was not dependent on the phosphate anion. Due to the special self-purification charac- teristics of ELPsl20, it is simpler to separate, purify and prepare. ELPsl20 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 mecha- nism for ELPsl20 when mediating the biosilicification of silicic acid to form silica. Specifically, ELPsl20 showed the silica precipitation activity when added to silicic acid solution under ambient conditions. It differs from the reported pep- tides （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 ELPs 120. More in-depth studies are needed to confirm these possible molecular mechanisms. In addition, the silicon dioxide formed by ELPsl20 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.