Water-immiscible bio-inert coatings and film formation from aqueous dispersions of poly (2-methoxyethyl acrylate) microspheres

In recent years, advances in biomedical research require that novel biomaterials and their coatings should exhibit biocompatibility without interaction with biological components. A wide variety of synthetic polymers that meet this criterion is available for the formation of bio-inert surfaces. However, a great deal of these polymers is soluble in water and possess the local structure of water at a polymer interface, which is crucial for the sought after bio-inertness, since water adsorption influences protein adsorption/cell adhesion when a polymer make contact with blood. This drawback has led to the fabrication of a novel bio-inert polymer that exhibits poor water solubility: the poly (2-methoxyethyl acrylate). This novel polymer has a low glass transition temperature that yield a rubber-like state under body environment. More so, poly (2-methoxyethyl acrylate)-based microspheres have been synthesized as they are considered promising colloidal carriers. Conversely, little has been done on the rubber properties of the poly (2-methoxyethyl acrylate)-based microspheres with respect to film formation despite the fact that the polymer microspheres are suitable for the formation of tailorable films.

Researchers led by Professor Daisuke Suzuki at Shinshu University in Japan developed an adhesive, flexible, and transferable free-standing film composed of soft poly (2-methoxyethyl acrylate) microspheres formed and characterized under mild and biocompatible conditions for applications in biomedical engineering. They aimed at clarifying the properties of pure poly (2-methoxyethyl acrylate) microspheres in terms of protein adsorption resistance and film formation. Their work is now published in the research journal, Colloids and Surfaces B: Bio-interfaces.

Briefly, the empirical procedure commenced with the synthesis of monodisperse poly (2-methoxyethyl acrylate) microspheres via aqueous free-radical, soap-free precipitation/soap-free emulsion polymerization techniques. The team opted for these techniques since they result in uniformly sized microspheres that are obtained without the use of any dispersion stabilizers, such as surfactants and other polymers. The research team then characterized the plasma protein adsorption behavior of the poly (2-methoxyethyl acrylate) and other typical polymer microspheres in terms of the amounts of plasma proteins adsorbed by the dispersed poly (2-methoxyethyl acrylate) microspheres in a bulk solution.

The researchers were able to observe that non-functionalized and non-cross-linking poly (2-methoxyethyl acrylate) microspheres could be obtained by aqueous soap-free precipitation and emulsion polymerization in water. These poly (2-methoxyethyl acrylate) microspheres showed a suppression of non-specific protein adsorption, which was confirmed through a plasma protein adsorption experiment; the adsorption amounts of the human serum albumin, fibrinogen from human plasma, and immunoglobulin G were much lower than those on other surfaces of the polymer microspheres in bulk solution, regardless of the charged state of the poly (2-methoxyethyl acrylate) microspheres.

Daisuke Suzuki and co-workers also observed that the injectable poly (2-methoxyethyl acrylate) dispersion can be applied to form the poly (2-methoxyethyl acrylate) coated substrate, the adhesive and transferable free-standing film. Such diversity in applicability can be attributed to the rubber property of the poly (2-methoxyethyl acrylate) microspheres without any impurities and organic solvents, which are usually used to form the poly (2-methoxyethyl acrylate) chains and their applications. The clean and pure poly (2-methoxyethyl acrylate) microsphere system described within offers new perspectives for applications in biomedical engineering.