Abstract
The objective of this study was the preparation and physico-chemical, mechanical, biological, and functional characterization of a multifunctional coating for an innovative, fully implantable device. The multifunctional coating was designed to have three fundamental properties: adhesion to device, close mechanical resemblance to human soft tissues, and control of the inflammatory response and tissue repair process. This aim was fulfilled by preparing a multilayered coating based on three components: a hydrophilic primer to allow device adhesion, a poly(vinyl alcohol) hydrogel layer to provide good mechanical compliance with the human tissue, and a layer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers. The use of biopolymer fibers offered the potential for a long-term interface able to modulate the release of an anti-inflammatory drug (dexamethasone), thus contrasting acute and chronic inflammation response following device implantation. Two copolymers, poly(vinyl acetate-acrylic acid) and poly(vinyl alcohol-acrylic acid), were synthetized and characterized using thermal analysis (DSC, TGA), Fourier transform infrared spectroscopy (FT-IR chemical imaging), in vitro cell viability, and an adhesion test. The resulting hydrogels were biocompatible, biostable, mechanically compatible with soft tissues, and able to incorporate and release the drug. Finally, the multifunctional coating showed a good adhesion to titanium substrate, no in vitro cytotoxicity, and a prolonged and controlled drug release.
Highlights
Notable progress in recent years has been made in biopolymers, synthetic polymers, and advanced composite materials
Chemical structure of the copolymers was confirmed by FT-IR spectroscopy, the correlation of spectra with corresponding homopolymers allowed us to obtain a chemical composition of vinyl acetate (VAc) and acrylic acid (AA) of 70:30 wt.%, according a method reported in our previous work [9]
The thermogram of P(VAc-co-AA) shows, in the first scan, the event corresponding to the glass transition (Tg) of PAA segment, while any signal was detected for the PVAc component, as confirmed
Summary
Notable progress in recent years has been made in biopolymers, synthetic polymers, and advanced composite materials. An interesting new development considers the modification of polymer surfaces and interfaces, generating, for example, hybrid coatings using organic or inorganic nanostructures to improve the surface properties of traditional polymeric materials [2,3]. Research in biopolymers and synthetic polymers has developed in the biomedical field, contributing to the production of new biocompatible materials. In this general context, there is a large interest in the development of implantable robotic devices to allow patients with severe hormonal alterations or chronic pain to benefit from an automatic and effective administration of specific drugs [4]. To allow a better interaction of the medical device with the biological system surrounding it, often, polymeric coatings are applied [6]
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