Analytical investigations of poly(acrylic acid) coatings electrodeposited on titanium-based implants: a versatile approach to biocompatibility enhancement
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A polyacrylic acid film was synthesized on titanium substrates from aqueous solutions via an electroreductive process for the first time. This work was done in order to develop a versatile coating for titanium-based orthopaedic implants that acts as both an effective bioactive surface and an effective anti-corrosion barrier. The chemical structure of the PAA coating was investigated by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was employed to evaluate the effect of annealing treatment on the morphology of the coatings in terms of their uniformity and porosity. Inductively coupled plasma mass spectrometry was used to measure ion concentrations in ion release tests performed on Ti-6Al-4V sheets modified with PAA coatings (annealed and unannealed). Results indicate that the annealing process produces coatings that possess considerable anti-corrosion performance. Moreover, the availability and the reactivity of the surface carboxylic groups were exploited in order to graft biological molecules onto the PAA-modified titanium implants. The feasibility of the grafting reaction was tested using a single aminoacid residue. A fluorinated aminoacid was selected, and the grafting reaction was monitored both by XPS, using fluorine as a marker element, and via quartz crystal microbalance (QCM) measurements. The success of the grafting reaction opens the door to the synthesis of a wide variety of PAA-based coatings that are functionalized with selected bioactive molecules and promote positive reactions with the biological system interfacing the implant while considerably reducing ion release into surrounding tissues.
KeywordsTitanium PAA Electrosynthesis Corrosion protection Biomaterial Surface modification
The authors wish to dedicate this paper to the 72nd birthday of Professor Pier Giorgio Zambonin. They would like to thank him warmly for the continuous critical guidance that he has given them throughout their academic careers. They have greatly benefited from his valuable suggestions about how to approach research work, such as to always follow a rigorous approach and clearly define the scientific objectives.
The financial support of University of Bari is greatly appreciated.
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