A Protein Resistant Surface Using Self-Assembly of a Natural Osmolyte with Non-Covalent Forces

Preparing protein-resistant surfaces in aqueous solution is challenging, complex and expensive and usually requires surface modification using multi-step wet chemical methods, phase separation hydrophilic from hydrophobic polymers or some form of surface grafting (i.e. photo-induced graft polymerization). We have discovered a simple adsorption and coating process with excellent protein resistance that is fast, relatively stable and inexpensive. It is based on the self-assembly of a natural osmolyte, trimethyl ammonium oxide (TMAO), with non-covalent forces on a hydrophobic support in aqueous solution. The asymmetric character or Janus-like property of TMAO with apolar and polar ends, presents, on adsorption, a mostly oriented self-assembled and stable exposed hydrophilic layer that self-heals. The resultant TMAO coat exhibited similar protein-resistance to a PEG terminated self-assembled monolayer (PEG-SAM). Adhesion measurements using multi molecular force spectroscopy confirm that the TMAO+CH3-SAM surfaces behave like strongly hydrophilic surfaces. The TMAO layer was stable up to 40ºC via washing, remained adsorbed even after 600 min of washing at 24ºC, and can easily be regenerated simply by adding additional TMAO to the solution. The process is simple, self-forming and self-healing in aqueous solution and can be used after device assembly with complex geometries and narrow channels that are normally inaccessible to other covalent surface modification methods. It could also be useful for medical applications since TMAO is naturally present in living cells.