Adsorption Law Of Protein On Nano-ZnO Surface With Adjustable Wettability And Its Application In Protein Separation

As an attractive semiconductor nanomaterial with good biocompatibility and excellent optoelectronic properties,nanostructured ZnO has shown great promise in various biomedical applications including fluorescence imaging and biological detection.It is important to research the interfacial interaction between ZnO and biological substances in the process of promoting the biological application of ZnO nanomaterials.Lots of researches have shown that wettability of the solid surface is one of the important factors affecting the biological properties of nano-bio interface.Although the wettability of ZnO has been studied,few reports have examined its influence on modulating protein adsorption.Protein absorbed onto a solid surface will further impact cell adhesion.Therefore a systematic investigation into the effects of the wettability of ZnO on protein adsorption and the establishment of the adsorption model will shed light on the understanding of the relevant interaction mechanisms,and provide theoretical and technical basis for the development of efficient nano-biomedical platform.In this paper,nano-ZnO with regulatable wettability was used to study the law of protein adsorption and cell adhesion on the surface.Based on this,superhydrophobic nano-ZnO was introduced into the traditional protein magnetic separation technique to improve separation efficiency of trace protein.The specific research contents are as follows:1.A series of ZnO surfaces spanning a range of water wettability from superhydrophilicity to superhydrophobicity were obtained via UV irradiation and dark storage.The effect of nano-ZnO surface wettability on the adsorption behavior of protein was studied systematically by using bovine serum albumin(BSA)as model protein.The results showed thatthe adsorption amount of BSA increased with increase of hydrophilicity because of increased adsorption sites on the hydrophilic surface.BSA adsorption kinetics and theinfrared spectrum characterization confirm the simultaneous occurrence of the protein adsorption,desorption and conformational changes.The rates of adsorption and desorption increased with the hydrophobicity of the ZnO surfaces.It might be related with the energy barrier caused by the water bound to the ZnO surfaces via hydrogen bonding.The rate of conformational changeincreased as hydrophobicity increased from superhydrophilicity to hydrophobicity,while decreased slightly when further increasing hydrophobicity to superhydrophobicity.It might be influenced mainly by the hydrophobic interaction and the amount of adsorption sites.And the adsorption rule of BSA,a “soft” protein,on the ZnO surfaces with different wettability could be extended to other “hard” protein(lysozyme)adsorption and 4T1 cells adhesion.This study has deepen the understanding of the mechanism of biological interface and provided an important theoretical and experimental reference for the selection,design and application of nano biological interface materials.2.The superhydrophobic nano-ZnO was used as the container material of trace protein magnetic separator to study the effect of surface wettability on the separation efficiency.The results showed that the protein separation efficiency decreased with the decrease of protein concentration.The separation efficiency on superhydrophobic nano-ZnO surface showed obvious advantages comparing to commercial plastics and glassespecially at low concentration(? 200 ?g/mL).However,the separation efficiency on the ZnO seed layer was lower than that of the common commercial materials,which indicated that the surface wettability instead of chemical composition was the main reason accounts foranti-fouling performanceof the nano-ZnO surface.The protein separation efficiency of superhydrophobic nano-ZnO was also related to the type of protein.And the recovery efficiency of “hard” protein was higher than that of “soft” protein.The superhydrophobic ZnO surface is suitable for the protein separation system with pH of 6 ~ 8 and ionic strength of 0 ~ 1mol/mL.The results provide a new way to improve the magnetic separation technology of trace proteins.