Surface modification of biomaterials with proteins
Currently, there are various methods of characterization and surface modification of biomaterials and useful applications of fundamental concepts in several biomedical solutions.
In various biomedical applications of developing implantable medical devices (such as pacemakers and stents), surface properties/interactions of proteins with a specific material must be evaluated with regards to biocompatibility as it plays a major role in determining a biological response.
Surface modification can be done through various methods, which can be classified through three main groups: physical (physical adsorption, Langmuir blodgett film), chemical (oxidation by strong acids, ozone treatment, chemisorption, and flame treatment) and radiation (glow discharge, corona discharge, photo activation (UV), laser, ion beam, plasma immersion ion implantation, electron beam lithography, and γ-irradiation).
[1] In a biomedical perspective, biocompatibility is the ability of a material to perform with an appropriate host response in a specific application.
It is described to be non-toxic, no induced adverse reactions such as chronic inflammatory response with unusual tissue formation, and designed to function properly for a reasonable lifetime.
Although most synthetic biomaterials have the physical properties that meet or even exceed those of natural tissue, they often result in an unfavorable physiological reaction such as thrombosis formation, inflammation and infection.
Furthermore, although some of the biomaterials have good biocompatibility, it may possess poor mechanical or physical properties such as wear resistance, anti-corrosion, or wettability or lubricity.
Thus, attachment of molecules with different protein for example, those containing Arginine-Glycine-Aspartate (RGD) sequences are expected to modify the surface of tissue scaffolds and result in improvement of cell adhesion when placed into its physiological environment.
[2][11][12][13] The unique advantage of plasma modification is that the surface properties and biocompatibility can be enhanced selectively while the favorable bulk attributes of the materials such as strength remain unchanged.
Plasma immersion implantation is a technique suitable for low melting point materials such as polymers, and widely accepted to improve adhesion between pinhole free layers and substrates.
The ultimate goal is to enhance the properties of biomaterials such as biocompatibility, corrosion resistance and functionality with the fabrication of different types of biomedical thin films with various biologically important elements such as nitrogen,[14] calcium,[15][16] and sodium[17] implanted with them.
To prevent such a negative immune reaction, immunosuppressive drugs may be prescribed, or autologous tissue may produce the protein coating.
Macrophages that fail to destroy pathogens will merge to form a foreign-body giant cell which quarantines the implant.
High levels of oxidants cause fibroblasts to secrete collagen, forming a layer of fibrous tissue around the implant.
Chemical species are dissolved in an organic solution where reactions take place to reduce the hydrophobic nature of the polymer.
These techniques employ high energy photons (typically UV) to break chemical bonds and release free radicals.
Ma et al. compared cell adhesion for various surface groups and found that OH and CONH2 improved PLLA wettability more than COOH.
[24] After the changes occur, the ionized plasma gas is able to react with the surface to make it ready for protein adhesion.
Several plasma-based technologies have been developed to contently immobilize proteins depending on the final application of the resulting biomaterial.
It is also possible to covalently and directionally immobilize osteoinductive peptides in the surface of the ceramic materials such as hydroxyapatite/β-tricalcium phosphate to stimulate osteoblast differentiation and better bone regeneration [27] RGD peptides have been shown to increase the attachment and migration of osteoblasts on titanium implants, polymeric materials, and glass.
Peripheral nervous system damage is typically treated by an autograft of nerve tissue to bridge a severed gap.
In order to reduce thrombogenicity, surfaces can be coated with fibronectin and RGD containing peptides, which encourages attachment of endothelial cells.
The peptides YIGSR and REDV have also been shown to enhance attachment and spreading of endothelial cells and ultimately reduce the thrombogenicity of the implant.
