Construction And Characterization Of Controllable Surface Density Gradients On Silicon Materials

Gradient materials with progressively changing surface properties can achieve a variety of biological functions.Therefore,the preparation and application of surface gradient materials have been extensively studied.Among them,the gradient construction on the surface of silicon or glass materials develops rapidly,but the activation method of the silane coupling agent brings about problems such as poor surface controllability,lack of regular guidance,and difficulty in forming quantitative mathematical expressions.Based on the previous researches of the vinyl sulfone surface chemistry,we prepared a silicon material substrate containing active double bonds for the construction of surface chemical gradients in this paper.The surface reaction kinetics are controlled by adjusting the reaction conditions,and thus the slope of the surface gradient.We also preliminary studied the coupling of active biomolecules on the surface to prepare a gradient surface that can regulate protein adsorption or cell behavior.Firstly,the active double bond substrate was prepared by Michael addition reaction of bis(vinylsulfonyl)methane(BVS)on the surface of silicon or glass.A single factor experiment was used to screen the catalyst to determine 1-methylimidazole(1-MIM)as a mild and controllable catalyst.Then we designed orthogonal experiments to screen the BVS concentration,catalyst equivalent and reaction temperature.As a result,100 mmol/L BVS,5 mmol/L 1-MIM,25? were selected as substrate modification conditions,with a reaction half-life of 1.59 hours.X-ray photoelectron spectroscopy(XPS)was used to further verify the successful modification of BVS on the surface of silicon and glass.Finally,we verified that surface-active double bonds can couple molecules and maintain their biological activities.Then,the fluorescent molecule Sulfo-Cyanine 3 amine(Sulfo-Cy3-NH2)was selected for surface gradient model construction.The amino group of Sulfo-Cy3-NH2 can be added to the double bond of the substrate,and the surface can be characterized by scanning the fluorescence intensity.By adjusting the surface double bond density,Sulfo-Cy3-NH2 concentration,reaction temperature,p H and other conditions to adjust the surface reaction rate,the reaction rate can be increased 1.4~4.6 times and then the slope of the fluorescence gradient can be adjusted.Mathematical expressions were used to quantify the fluorescence curves.We finally proved that on the active double-bond surface,the surface chemical gradient can be constructed by injection method,and the gradient slope can be adjusted by adjusting the reaction conditions.Finally,peptide(GGGRGDS)and 2-lactobionamidoethyl methacrylate(LAMA)were selected to construct the bioactive surface.The reaction kinetic process of GGGRGDS on the surface are characterized by the static water contact angle.On the uniform GGGRGDS surfaces with reaction time of 0 hours,0.5 hours,1 hour and 2 hours,significant differences can be observed in the number of adhered mesenchymal stem cells,proving that the GGGRGDS density on the surface can effectively regulate cell adhesion.Subsequently,we successfully synthesized LAMA monomers,characterizing by nuclear magnetic resonance(NMR)spectroscopy and Fourier transform infrared(FT-IR)spectroscopy.We proved the polymerization of LAMA on the active double bond substrate by the reduction of contact angle and attenuated total reflection-Fourier transform infrared(ATR-FTIR)spectroscopy.The dissociation constant of surface polymerized LAMA and ricinus communis agglutinin I(RCA120)was fitted to 2.40 × 10-7 mol/L on the BLItz probe,indicating the “glycoside cluster effect” on the polymerization surface.