Surface modification with polyallylamines for adhesion of biopolymers and cells

Cationic polymers with NH2-groups were used for modification of charged and uncharged surfaces of planar slides, wells of plates, and spherical nanoparticles. Our study was aimed at development of a simple functionalization method of plain surfaces and colloids of different chemical compositions for adhesion of native biopolymers, including proteins, and viable bacterial and eukaryotic cells. Poly(allylamine)s (pAA) and polylysines (pLys) of different molecular weights spontaneously formed interfaces convenient for adhesion of biopolymers and cells. Thickness of the pAA 65 kDa layer ∼1.5–2 nm was measured by two methods: 1) atomic force microscopy (AFM) on mica slides and 2) registration of the long range surface optical waves excitation angle and the critical angle of total internal reflection from the liquid on a photonic crystal surface by using the biosensor. The sorption capacity of 0.1 mg/ml pAA 65 kDa exceeded the values of other polyamines at different concentrations. Physisorption of proteins on pAA layer was reversible and up to 70% of attached proteins could be removed by subsequent washes. Additional treatment with glutaraldehyde (GA) provided stable chemical cross-linking of the compounds containing primary NH2-groups with aminated surfaces. The proteins immobilized on the pAA-covered surface retained their ability to bind with specific monoclonal and polyclonal antibodies. Bacterial cells after adhesion on pAA65-covered surfaces maintained their morphology, could reproduce and express the green fluorescent protein (gfp) gene under control of the inducible lac promoter. Eukaryotic cells of human and mammalian origin also remained viable on pAA-treated slides as proven by their staining with fluorescent dyes and cell divisions until confluent monolayers. Mammalian cells could not attach onto silicon wafers but grew on pAA interface of the silicon slides until confluent monolayers. Thus, surface modification with polyallylamines provides adhesion of native biopolymers and living cells.