Adhesion in the biologic environment

There are good reasons to believe that adhesion of particulate matter in all wet, salty, biochemically active circumstances follows a common pattern, and that such adhesion can be effectively controlled by adjusting the surface properties - especially surface energy--of the substrate involved. One of the most compelling proofs of, at least, the bioengineering utility of surface energy modification to maximize or minimize biological adhesion is the successful, now long-term, implantation of total artificial hearts. These pumps, and the related intra-aortic balloons and left ventricular assist devices, do not accumulate blood clots or thrombotic masses during their contact with natural blood. Since surfaces contacting blood have received most careful scrutiny for more than a decade, the instruction gained from examining the usual and unusual sequelae of blood cell adhesion to nonphysiologic surfaces has been most valuable in revealing the general features of biological adhesion in other, less well-studied, circumstances. The initial events of blood contact with foreign solid surfaces are briefly reviewed, and the impressive similarities of these events to sequences in oceanic fouling of heat exchangers, cell culture experiments and dental plaque formation are highlighted. A unifying concept, based on control of the surface free energy through an empirical correlate called the "critical surface tension," is presented as an explanation for the common features of biological adhesion in all of Nature's domains.