Construction of multiple generation nitriloacetates from poly(PEGMA) brushes on planar silicon surface for enhancement of protein loading

We constructed multiple generation nitriloacetates from poly(poly(ethylene glycol)monomethacrylate) brushes on a planar silicon surface (Si‐ g ‐P(PEGMA)) to improve the capacity of binding proteins and the biofouling repellence. Firstly the freshly etched Si(111)H reacted with 10‐undecen‐1‐ol under an optimized microwave irradiation condition to produce hydroxyl‐terminated substrates. Secondly surface initiators for atom transfer radical polymerization were introduced by means of esterification between 2‐bromo‐2‐methylpropionyl bromide and surface hydroxyl groups. Thirdly polymer brushes of Si‐ g ‐P(PEGMA) were grown from surface initiators; then their side chain hydroxyls were carboxylated with succinic anhydride to become polymer brushes of Si‐ g ‐P(PEGMA‐COOH). Finally multiple generation nitriloacetates were obtained by iterative esterification of carboxylic acids with N‐hydroxysuccinimide (NHS)/N,N′‐dicyclohexylcarbodiimide, yielding amino‐reactive NHS esters, and successive amidation with aminobutyl nitrilotriacetic acid. After coordinated with Ni(II), the first to third generation nitriloacetates were applied to bind histidine‐tagged thioredoxin‐urodilatin. All stepwise conversions were monitored with multiple transmission‐reflection infrared spectroscopy (MTR‐IR). The highly sensitive MTR‐IR spectra provide clear stretching bands of amide v (NH) at 3441 and 3345 cm −1 , whose integrated peak areas were used to estimate the enhancement ratios of protein loading by multiple generation nitriloacetates as first generation:second generation:third generation = 1:1.7:2.3.