Structure and reactivity of water at biomaterial surfaces

Contact angle measurement and contact angle interpretation

In this review, initial microbial adhesive interactions are divided into adhesion to substratum surfaces, coaggregation between microbial pairs and co-adhesion between sessile and planktonic microorganisms of different strains or species. The physico-chemical mechanisms underlying the adhesive interactions are described and a critical review is given of currently employed methods to study microbial adhesive interactions, with an emphasis on the use of the parallel plate flow chamber. Subsequently, for each of the three microbial adhesive interactions distinguished, the role of Lifshitz-van der Waals, acid-base and electrostatic interactions is described based on existing literature.

Physico-chemistry of initial microbial adhesive interactions – its mechanisms and methods for study

In this study, the adhesion of bacteria differing in surface hydrophobicity was investigated. Cell wall hydrophobicity was measured as the contact angle of water on a bacterial layer collected on a microfilter. The contact angles ranged from 15 to 70 degrees. This method was compared with procedures based upon adhesion to hexadecane and with the partition of cells in a polyethylene glycol-dextran two-phase system. The results obtained with these three methods agreed reasonably well. The adhesion of 16 bacterial strains was measured on sulfated polystyrene as the solid phase. These experiments showed that hydrophobic cells adhered to a greater extent than hydrophilic cells. The extent of adhesion correlated well with the measured contact angles (linear regression coefficient, 0.8).

The role of bacterial cell wall hydrophobicity in adhesion.

The role of van der Waals forces and hydrogen bonds in “hydrophobic interactions” between biopolymers and low energy surfaces

From the contact angle θ determined with one liquid (of known surface tension) only, it is possible to obtain the values of the surface tensions γSV and γSL, via the equation of state (1): where the subscripts S and L stand for the solid S and the liquid L, whilst the subscript V stands for vapor. In conjunction with Young's equation (2): relation [l] yields: With the help of a computer program values for γsv (1) and for γSl (3) can be derived for different values of the contact angle 8 obtained with a liquid of given γLV

D. R. Absolom

Papers

Conversion Tables of Contact Angles to Surface Tensions