Immobilized polymeric microspheres: Polyacrolein microspheres covalently bound in a monolayer structure onto glass surfaces

Novel materials composed of an unpacked monolayer of polyacrolein microspheres covalently bonded onto glass surfaces have been prepared and characterized. These surfaces were synthesized by the covalent binding of long- and short-chain length ω-cyano-alkylsilane compounds (SiCl₃(CH₂)_nCN and Si(OMe)₃(CH₂)_nCN, where n = 3 and 16) onto glass substrates. The nitrile groups at the ω position were then reduced to primary amino groups. Polyacrolein microspheres of 0.7 μm average diameter were then bonded to the modified surfaces. This binding of the microspheres to the derivatized surfaces is achieved via polyvalent Schiff-base bonds formed by the interaction between aldehyde groups of the microspheres and ω-primary amino groups of the derivatized glass surfaces. The percent coverage of the glass surfaces by the microspheres was higher for surfaces coated with the trichloroalkylsilane compounds compared to trimethoxyalkylsilane compounds, and higher also for surfaces coated with the short-chain length alkylsilane compounds compared to surfaces coated with the long ones. The residual aldehyde groups of the immobilized microspheres can then be used for the covalent binding of amino ligands, e.g. proteins, in a single step and at physiological pH (or any other desired pH). The binding kinetics of bungarotoxin to the immobilized microspheres has been investigated. Fourier transform-infrared/attenuated total reflection, electron spectroscopy for chemical analysis, contact angle measurements and scanning electron microscopy have been used for the characterization of the alkylsilane coatings and the binding of the microspheres to these coatings.