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 di- mensions 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 de- scribed 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 （a--t） kinetics curves and surface pressure vs. area （a--A） isotherms. The factors that in- fluence protein adsorption on the clay layer, such as surfactants, the concentration of clay, equilibrium time, categories of pro- tein, and injection methods, were investigated. The parameters such as protein amount （nS）, packing density （O）, and average surface area per molecule （.（2） 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 pro- liferation of WDL7-GFP is greatly suppressed by lysozyme, which demonstrates that lysozyme still retains its bioactivity after it is immobilized in the CPUFs.

Fundamentals and applications of enzyme powered micro/nano-motors

Micro/nanomotors(MNMs)are miniaturized machines that can convert many kinds of energy into mechanical motion.Over the past decades,a variety of driving mechanisms have been developed,which have greatly extended the application scenarios of MNMs.Enzymes exist in natural organisms which can convert chemical energy into mechanical force.It is an innovative attempt to utilize enzymes as biocatalyst providing driving force for MNMs.The fuels for enzymatic reactions are biofriendly as compared to traditional counterparts,which makes enzyme-powered micro/nanomotors(EMNMs)of great value in biomedical field for their nature of biocompatibility.Until now,EMNMs with various shapes can be propelled by catalase,urease and many others.Also,they can be endowed with multiple functionalities to accomplish on-demand tasks.Herein,combined with the development process of EMNMs,we are committed to present a comprehensive understanding of EMNMs,including their types,propelling principles,and potential applications.In this review,we will introduce single enzyme that can be used as motor,enzyme powered molecule motors and other micro/nano-architectures.The fundamental mechanism of energy conversion process of EMNMs and crucial factors that affect their movement behavior will be discussed.The current progress of proof-of-concept applications of EMNMs will also be elaborated in detail.At last,we will summarize and prospect the opportunities and challenges that EMNMs will face in their future development.