Clay-protein ultrathin films:Design and bio-catalytic performance study

In recent years,immense interest has been paid to the biomolecular architecture with the aim of protein assembly in two dimensions on solid substrates,and the constructions of clay-protein ultrathin films(CPUFs) are particularly concerned.This paper gives an overview of the recent research concerning the protein molecules(lysozyme,papain,protamine,bovine serum albumin) immobilized on clay mineral(Na-saponite) platelets and assembled in monolayered or multilayered hybrid ultrafilms or nanofilms.Two techniques including alternate layer-by-layer(LbL) assembly and the Langmuir-Blodgett(LB) are described in detail.A variety of means,including UV-vis absorption,attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy,XRD,AFM and surface chemistry techniques,have been described for characterization of the films in terms of quantification of protein and clay.The result reveals that electrostatic interaction is a prominent but not the only driving force in CPUF construction.In the case of LB technique,we managed to manipulate the elementary clay mineral platelets(1.3 nm in thickness) and assemble proteins into CPUFs with the aid of surfactants,and the formation of CPUFs was monitored via surface pressure vs.time(π-t) kinetics curves and surface pressure vs.area(π-A) isotherms.The factors that influence protein adsorption on the clay layer,such as surfactants,the concentration of clay,equilibrium time,categories of protein,and injection methods,were investigated.The parameters such as protein amount(nS),packing density(■),and average surface area per molecule(Ω) of deposited CPUFs were measured via method of surface chemistry and spectroscopy.By comparing the results of surface chemistry with those of adsorption experiments,we demonstrate that the surface chemistry method is a useful tool in investigating CPUFs.We also found that the water soluble protein molecules could form protein-clay hybrid monolayer over the dilute clay dispersions without addition of surfactants,and CPUFs containing elementary clay sheets and protein with great homogeneity were easily prepared by controlling certain surface pressure.To investigate the bio-catalytic performance of the immobilized lysozyme in CPUFs,we deposited CPUFs onto a cover glass,and installed the cover glass in a flow cell-grown reactor for Comamonas testosteroni(WDL7-GFP) incubation.The results show that the proliferation of WDL7-GFP is greatly suppressed by lysozyme,which demonstrates that lysozyme still retains its bioactivity after it is immobilized in the CPUFs.