Quantitative Imaging of Protein Adsorption on Patterned Organic Thin-Film Arrays Using Secondary Electron Emission

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• 作者：Nathan H. Mack ; Rui Dong ; and Ralph G. Nuzzo
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：June 21, 2006
• 年：2006
• 卷：128
• 期：24
• 页码：7871 - 7881
• 全文大小：398K
• 年卷期：v.128,no.24(June 21, 2006)
• ISSN：1520-5126

文摘

Secondary electron emission is developed as a means to quantify and image protein binding toAu surfaces modified with patterned organic thin-film arrays. Alkane thiols were patterned via microcontactprinting on gold, and their effects on the secondary electron (SE) yield of the surface, systematicallyquantified. We show that a self-assembled monolayer (SAM) of hexadecane thiol significantly increasesthe SE yield over the native gold surface, a yield that increases as a function of alkane chain length (C₈-C₁₆). This effect is linearly correlated with the surface potentials and wetting properties of these SAMs.Surface layers comprised of poly(ethylene glycol) (PEG) grafted polyacrylamide polymers behave differently,affecting the SE yield by attenuation according to the polymer thickness. These results demonstrate therelative contributions of factors related to the adsorbate molecular structures that serve to strongly mediatethe SE yield, providing a foundation for exploiting them as a quantitative electron imaging probe. The lattercapability is demonstrated using a model microfluidic assay in which a series of proteins was spatiallyaddressed to a SAM-based pixel array. The gray scale contrasts seen with protein adsorption are directlycorrelated with both protein molecular weight and mass coverage. These methods are used in two modelprotein assay experiments: (1) the measurement of the concentration dependent adsorption isotherm fora model protein (fibrinogen); and (2) the selective recognition of a biotinylated protein layer by avidin. Theseresults demonstrate a unique approach to imaging protein binding processes on surfaces with both highanalytical and spatial sensitivity.