An Overview of Serum Albumin Interactions with Biomedical Alloys

Understanding the interactions between biomedical alloys and body fluids is of importance for the successful and safe performance of implanted devices. Albumin, as the first protein that comes in contact with an implant surface, can determine the biocompatibility of biomedical alloys. The interaction of albumin with biomedical alloys is a complex process influenced by numerous factors. This literature overview aims at presenting the current understanding of the mechanisms of serum albumin (both Bovine Serum Albumin, BSA, and Human Serum Albumin, HSA) interactions with biomedical alloys, considering only those research works that present a mechanistic description of the involved phenomena. Widely used biomedical alloys, such as 316L steel, CoCrMo and Titanium alloys are specifically addressed in this overview. Considering the literature analysis, four albumin-related phenomena can be distinguished: adsorption, reduction, precipitation, and protein-metal binding. The experimental techniques used to understand and quantify those phenomena are described together with the studied parameters influencing them. The crucial effect of the electrochemical potential on those phenomena is highlighted. The effect of the albumin-related phenomena on corrosion behavior of biomedical materials also is discussed.

Electrophoretic deposition of multi-scale structured TiO2 surfaces

The long term fixation of biomedical implants constitutes an issue in the clinical praxis. Implant fixation can be improved by functionalizing its surface. In fact, the tissue response around an implant is conditioned by its surface morphological and chemical properties. Coatings for implants (orthopedic and dental) function at the bone-implant fixation interface. As proved by research activities in the biomedical field, coatings with topographic features in the nano- and micro-range are promising in terms of enhanced osteointegration, thus improved implant fixation. As for surface chemistry, titanium dioxide (TiO2) is an estabilished material for biomedical implants thanks to its outstanding physical and chemical properties such as high corrosion resistance and good biocompatibility. Electrophoretic deposition (EPD) is a simple and versatile coating technique. According to literature, EPD is an emerging potential coating technique for biomedical implants. In this work, the use of EPD in the preparation of TiO2 coatings characterized by a controlled multi-scale structured surface was addressed. For this aim, EPD was combined with a new procedure of particle functionalization and with the use of a fugitive spacer (polystyrene, PS) for the sintering treatment. A control and better understanding of the EPD process were achieved through a preliminary parametric study on EPD of TiO2 nanoparticles and PS microbeads. Particle concentration was found to play a key role in the EPD deposit formation of TiO2 nanoparticles (cathodic) and PS microbeads (anodic). A threshold value of particle concentration was identified, below which no deposit growth occurred. An interpretation of this finding was provided on the base of a new formulation of the EPD deposition mechanism. The results of the particle concentration study contributed to the preparation of suspensions with TiO2-PS composite particles, which could be used for cathodic EPD. Composite TiO2-PS particles with TiO2 nanoparticles covering PS microbeads were obtained in a newly developed wet colloidal process based on heterocoagulation and the use of polyelectrolytes. The resulting TiO2-PS particles were cathodically deposited on Ti6Al4V substrates. A sintering post-treatment caused the burning out of the PS beads and the densification of the TiO2 nanoparticles. The desired coatings with controlled micro- and nano-topography were achieved. The investigation on the role of particle concentration in EPD and the new interpretation of the deposition mechanism bring a deeper understanding of the EPD process. The achievement of TiO2 coatings with controlled morphology in the micro- and nano-range prepared by cathodic EPD on Ti6Al4V substrates is a contribution to the ongoing research on biomedical implants. Mechanical tests and surface analysis evaluating wettability and in vitro cell behavior with the achieved coatings are relevant topics for further research.

EPFL2009

Electrophoretic deposition of multi-scale structured TiO2 surfaces

EPFL2009