Antifouling Performance Of Nano-size Spherical Poly(N-hydroxyethyl Acrylamide) Brushes

The interest in the use of nanoparticles(NP)has increased significant in medical applications,such as biosensor and drug delivery carriers in the last decade.Nevertheless,their application is still impeded by the non-specific adsorption of proteins,cells,or other biological species in vivo and in vitro,which makes nanoparticles be easily detected and cleared by biological system.Typically,nonfouling polymers have been utilized to modify NP cores to solve this problem.In this work,poly(N-hydroxyethyl acrylamide)was hired to modify a solid polymer core,polystyrene(PS)nanoparticles,via surface-initiated photo-emulsion polymerization to form nano-sized spherical poly(N-hydroxyethyl acrylamide)brushes(PS@PHEAA).Its antifouling ability and stability in various pH and ionic strength were discussed,and the results demonstrate that PHEAA indeed provides a well antifouling coating to bare core.However,with the feature of spherical structure,stereo-hindrance is low at the top of brushes,which makes protein easily enter and be locked on polymer shell structure..Main work and conclusion as follow:PS@PHEAA was synthesized by surface initiated photo-emulsion polymerization.To confirm its chemical structure,Fourier transform infrared(FTIR)was used to characterize the composition of bare core and PS@PHEAA.Morphology of bare core and PS@PHEAA were observed by transmission electron microscopy(TEM)and scanning electron microscope(SEM).Dynamic light scattering(DLS)was used to characterize the size of nanoparticles before and after PHEAA modification.The weight-average molar mass of PHEAA was determined by GPC.With the molecular weight Mn obtained and the amount of PHEAA on the surface being know,the number of chains per particle and hence the grafting density ?may be calculated.The size and turbidity change of PS@PHEAA with a wide range of pH and ionic strength with and without protein were monitored to study their stability.The diameter slightly increases with the ionic strength increase especially in high ionic strength,and the sizes of PS@PHEAA in different pH are fluctuated at 210±5 nm and maintain for 120 h.The turbidity changes a little after subtracting PS@PHEAA-free blanks and protein-free blanks,which indicates that a weak interaction appeared.When the ionic strength increases above 150 mM,there are no obvious change in BSA system and a sharp decrease in Lyz system.The main reason is that pseudo-polyelectrolyte with positive charge is formed in solution with high ionic strength.Moreover,PHEAA also can provide a well protecting coating to bare core in complex protein solution.MTT Cell Proliferation Assay was hired to test the cell toxicity of PS@PHEAA and PS core.The results indicate that PHEAA layer did not enhance toxicity of PS to C2C12 cells.More accurate measuring instruments,the isothermal titration calorimetry(ITC)method,were employed to quantitatively study the thermodynamic parameters of the process of protein binding to PS@PHEAA.The data was gotten from two group samples which were prepared by different ways:dialysis and mixture.Dialysis group data were chosen to analyze.The results reveal that few positive proteins interact with core,while few negative proteins are locked in PHEAA chains.Thus,small angle X-ray scattering(SAXS)was used to confirm the protein location in PS@PHEAA.The results were agreed with ITC.