Fabrication And Tuning Of The Nanoscale Bio-interfaces Based On The Highly-Dispersive LDHs And Helical Silica Nanomaterials

The main concern in the enzyme engineering has focused on the fabrication of the highly-efficient nano-biohybrid catalysts through the synergistic interfacial assembly of the nanomaterials with enzymes. However, the interfacial assembly often leads to the denaturation of the enzyme active sites or the inaccessibility for the substrate to the active sites, resulting in a remarkable decrease of the bio-activity. The main challenge is to well fabricate nanoscale bio-interfaces based on nanomaterials to achieve high bio-activity for bound enzymes. Therefore, this work focuses on the controllable electrostatic assembly of layered double hydroxide (LDH) nanosheets, ordered LDH arrays and helical silica with enzymes to optimize the bio-activity. The main innovative research findings and conclusions are listed as follows:1. Through the controllable electrostatic assembly of delaminated LDHs nanosheets with enzymes, the bio-activity for the enzymes has been optimized. The interfacial assembly could rationally control the orientation of the bound porcine pancreatic lipase (PPL) and the dispersity of the bound hemoglobin (Hb). It is found that a remarkable enhancement of the bio-activity in hydrolysis reaction (445%) and the product enantiomeric excess in the kinetic resolution (54.5%) has been observed when the PPL is in the flat orientation with active sites facing the LDH layer at PPL loading of 0.5. For Hb, the optimized bio-activity depends not only on the dispersity but also on the intercalated regularity in different reactions. In the surface-controlled electrocatalytic reduction of H2O2, intercalated Hb-LDHs has the superior bio-activity while in the diffusion-controlled catalytic oxidation tremella-like Hb-LDHs has the best bio-activity.2. Ordered LDH arrays are employed to enhance the electron transfer of enzymes at the micro-nano-biointerfaces. Using a self-assembled L-cysteine monolayer on Au electrode (L-Cys/Au SAM), ordered vertical arrays of LDH nanosheets have been built with the LDH layer perpendicular to the substrate. The arrayed density of the LDHs nanosheets has been effectively controlled and further enhanced the direct electron transfer for horseradish peroxidase (HRP) at the micro-nano-biointerface. Moreover, the micro-nano-structure of the LDHs array has been further modulated by controlling the particle size of the LDHs nanosheets. The direct bio-interfacial eT and the electrocatalytic activity were found to be significantly enhanced along with the increase of the particle size of the nanosheets. HRP adsorbed LDH array with the particle size of 250 nm (HRP/250-LDH array) has the maximum electron transfer rate for (ks) of 5.17s-1. A sensitivity of as high as 4.02 mA·mM-1·cm-2 and a Michaelis-Menten constant (Kmapp) as small as of 41.3μmol·L-1 have been obtained in the electro-catalytic reduction of H2O2. A hopping mechanism previously proposed has been employed to account for the electron transfer at micro-nano-biointerface. It is found that the surface free energy of the LDH array has played a crucial role in the bio-interfacial electron transfer.3. In order to supply a more biocompatible interfacial environments for the enzymes, chiral silica and metal oxides with bio-mimetic helical surface have been fabricated in this work. Single-axis helical silica with controlled pore size and length/diameter, and dual-axis helical silica with controlled helicity have been rationally fabricated. The fabricated mechanism has also been studied. Employing single-axis helical silica with controlled pore size as the hard template, scattered nanoparticles, incontinuous oxide nanowires and self-supported helical bundles for both In2O3 and Co3O4 have been observed. It is found that the dimension of chiral pores of mesoporous silica plays an important role in controlling the filling and the morphologies for the metal oxides. The obtained self-supported chiral architectures of In2O3 and Co3O4 have large BET surface areas of 95 and 151 m2·g-1 The optical properties of In2O3 have been further studied. It is found that the measured photoluminescence (PL) intensity increases progressively from nanodots to nanowires and helical arrays, apparently implying the fact that the better ordered In2O3 nanostructure presents higher PL emission intensity. Furthermore, based on the biomimic chiral silica nanomaterials, the nano-biomimic bio-interface has been fabricated. Confocal Laser Scanning Microscope (CLSM) and fluorescence spectrum characterizations reveal that the dual-axis helical silica can effectively recognize the a-helix structure.