Biomaterial molecular adsorption

Self-assembled monolayers (SAMs) of alkanethiolates on metal surfaces constitute a class of molecular assemblies formed by the spontaneous chemisorption of long-chain functionalized molecules on the surface of solid substrates. Due to their ease of preparation, long-term stability, controllable surface chemical functionality, and high, crystal-like, two-dimensional order, SAMs represent suitable model surfaces to study molecular adsorption, adhesion, wetting, lubrication, and the interaction of proteins and cells with artificial organic surfaces. The latter phenomena are of crucial importance to the fields of biomaterials, biosensors, and medical devices. 

Early attempts to functionalize biomaterial surfaces with biological molecules were focused on improving blood compatibility of cardiovascular devices, such as the artificial heart and synthetic blood vessels, by immobilizing heparin or albumin on polyurethane or Dacron . To enhance cell adhesion to biomaterial surfaces, entire extracellular matrix (ECM) proteins, such as fibronectin and laminin, have been used directly as coatings. However, because of the nonspecific manner of whole protein adsorption, most of the cell binding capability is often lost. Using a molecular templating technique, it may be possible to select which protein(s) to absorb on biomaterial surfaces. ... 

Biomaterials. Adsorbed polymers find many apphcations as surface modifiers in biomedical apphcations. By choosing a combination of hydrophobic and hydrophilic copolsrmers, surfaces can be modified to make them biocompatible (65) (see Biomolecules at Interfaces). In the area of tissue engineering (qv), adsorbed layers with specihc amino acid sequences can be used to promote cell adhesion and proliferation. The recent developments in the design of biochips to analyze specihc DNA molecules also take advantage of this technology. Polymer adsorption on patterned surfaces can be used to mimic pattern recognition. This effect can be used to develop sensors and molecular-scale separation processes (66). 

Considering the peptides and proteins adsorption on solid surfaces we must remark that this is a quite complex route influenced by several factors as for instance the state of hydratation of both biomolecule and surface, the molecular structure, the intermolecular interaction and the ambient conditions [54]. In several biomaterials using a key attempt is taking place to organize protein adsorption, by structuring and/or chemical patterning the surface at a sub-micrometer scale [55-57]. 

Protein adsorption is crucial to numerous industrial processes. Examples are biomaterial fouling and barnacle attachment. Barnacles absorb after receiving chemical cues from the surface (2). Bacterial adhesion has also been attributed to protein absorption and is known to take place in two stages. These have been described as adhesion of the extracellular membrane proteins in the primary and secondary minimum (2). The primary minimum involves molecular recognition. The secondary minimum is governed mainly by non-specific van der Waals forces. 

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