Biomimetic Synthesis Of Silica Hollow Sphere Using Polypeptide And Mechanism Research

Biomineralization is, under certain physical and chemical conditions, the inorganic ions in solution are transformed to solid minerals under the specific control of the organic species. Inspired by the biomineralization, this paper aimed to synthesize silica hollow spheres under mild conditions using synthetic poly-L-lysine. We characterized the products by Scanning Electron Microscopy (SEM) to study the important physical and chemical factors that impacted the morphologies of silica, as well as the conditions of preparing silica hollow spheres. Laser Scanning Confocal Microscope (LSCM) and SEM were used to observe the growth process of silica hollow spheres. Moreover, Atomic Force Microscope (AFM) was applied to in situ observe the process of mineralization of silica. We studied the role of polypeptide and proposed a mechanism model of silica hollow spheres mediated by polypeptide.Main contents and conclusions are as follows:⑴Biomimetic synthesis of silica hollow spheres and researching the influence of factorsWe used synthetic poly-L-lysine as template, TEOS as silicon precursor to prepare silica hollow spheres in vitro under extreme mild condition. We characterized the products by SEM to research the influences of physical and chemical factors on silica morphologies. It was found that the morphologies of silica were tuned by molecular weight of poly-L-lysine, the molar mass ratio of reactants, pH and types of buffer solution. We prepared silica hollow spheres in PBS buffer solution at pH 7.6 at room temperature when the molar ration of poly-L-lysine (molecular weight 4-15 KDa) and silicon precursor was 3.15 * 10-4:1. This method is convenient, efficient and with good replications.⑵Investigating the formation mechanism of silica hollow spheres mediated by poly-L-lysineFourier Transform Infra Red Spectroscopy (FTIR), Energy Dispersive Spectroscopy (EDS) and Thermogravimetric analysis (TGA) showed the products were PLL/SiO2 compounds. We observed the growth process of silica hollow spheres by Scanning Electron Microscopy (SEM) and Laser Scanning Confocal Microscope (LSCM). We found that biomimetic synthesis of is a step-step process. Silica nanoparticles, which were induced by polypeptide, as fundamental particles assembled leading to the formation silica hollow spheres. The role of polypeptide is as template and catalyst. Especially, we in situ observed the nucleation, growth process of silica with Atomic Force Microscope (AFM) in liquid phase. It provided more direct evidence for mechanism of poly-L-lysine directed silica biomineralization. Moreover, AFM images in solid phase of PLL and products under extra force field further indicated polypeptide was as template in biomimetic synthesis. According to above-mentioned experimental data, we reasonably proposed a mechanism model for the formation of silica hollow spheres directed by poly-L-lysine.