Impact of Chemical Heterogeneities of Surfaces on Colonization by Bacteria

An essential yet never addressed parameter for the control of bacteria on functionalized biomaterial is surely the accessibility and heterogeneity of the functional groups immobilized on the surface. In this context, we investigated the colonization (Escherichia coli K12, Staphylococcus epidermidis RP62A) of precisely engineered surfaces revealing various densities of NH₂ and CH₃ functional groups. We demonstrated for the first time nonlinear relationships between the NH₂/CH₃ surface fraction and the quantity of adhered, adhering or detaching bacteria. Plateaus and transition zones were related to the range of NH₂/CH₃ surface fraction offering stability or sharp variation in bacterium/surface interactions. The nonlinear behavior was attributed to the discrete distribution of positive charges revealed by the bacterial membrane in the continuum of negative charges resulting from the phospholipids, which may correlate with one single specific distribution of positive NH₃⁺ charges on the material surface, because of electrostatic, repulsive interactions occurring at the local, molecular scale.