Morphology Dependence Degradation of Electro- and Magnetoactive Poly(3-hydroxybutyrate-co-hydroxyvalerate) for Tissue Engineering Applications

Abstract

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) is a piezoelectric biodegradable and biocompatible polymer suitable for tissue engineering applications. The incorporation of magnetostrictive cobalt ferrites (CFO) into PHBV matrix enables the production of magnetically responsive composites, which proved to be effective in the differentiation of a variety of cells and tissues. In this work, PHBV and PHBV with CFO nanoparticles were produced in the form of films, fibers and porous scaffolds and subjected to an experimental program allowing to evaluate the degradation process under biological conditions for a period up to 8 weeks. The morphology, physical, chemical and thermal properties were evaluated, together with the weight loss of the samples during the in vitro degradation assays. No major changes in the mentioned properties were found, thus proving its applicability for tissue engineering applications. Degradation was apparent from week 4 and onwards, leading to the conclusion that the degradation ratio of the material is suitable for a large range of tissue engineering applications. Further, it was found that the degradation of the samples maintain the biocompatibility of the materials for the pristine polymer, but can lead to cytotoxic effects when the magnetic CFO nanoparticles are exposed, being therefore needed, for magnetoactive applications, to substitute them by biocompatible ferrites, such as an iron oxide (Fe 3 O 4 ).Polymers 2020, 12, 953 2 of 15In particular, smart polymers are gaining increasing attention as substrates and scaffolds for tissue engineering applications mainly as electroactive substrates-mostly piezoelectric ones-such as poly(l-lactic acid) (PLLA) [5,6], poly(hydroxybutyrate) (PHB) [7], poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) [8,9] and poly(vinylidene fluoride) (PVDF) [10,11], among others. The ability of those materials to actively enhance and stimulate cellular differentiation processes has been already proven [12,13], based on their mechano-transduction characteristics, generating voltage upon mechanical stimulation and vice-versa [14]. Piezoelectricity is a property that appears in a diversity of human tissues, including DNA, bones or tendons, emphasizing the relevance of electrical and mechano-electrical stimulation in physiological processes [15,16]. In a different approach to apply mechanical and/or mechano-electrical signals, magnetoelectric materials have also proven their aptness for tissue engineering applications, with the particularity of allowing electrical stimulation of the materials and, therefore, on the cells cultured on them, through magnetic solicitation [17,18]. These materials can generate voltage upon magnetic stimulation through the coupling of the magnetostrictive effect (magnetic to mechanical) and piezoelectric effect (mechanical to electric) [19,20]. Magnetoelectric composites are thus achieved combining a piezoelectric polymer with magnetostrictive particles [21][22][23], and their potential for tissue engineering and enhancement of cellular di...

Accelerated Weathering Effects on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV/TiO2 Nanocomposites

“…When crystallization occurs over a broader temperature range, it means that the degradation process reduced the rate of crystallization of PHBV, affecting the morphologies of its crystals. The crystallization degree is higher for the weathered samples, which is the result of the easier re-organization of the shorter polymer chains after chain scission during degradation, as previously explained [ 15 , 25 , 26 , 55 , 58 , 94 , 96 , 97 , 98 ].…”

“…The most intense peak slightly increased from 93 to 96 °C, respectively, for PHBV/TiO 2 /0 h and PHBV/TiO 2 /2000 h. As observed for the neat PHBV, the PHBV/TiO 2 nanocomposites also show a third melting peak which is attributed to changes in the physical structure of the polymer chains during degradation, leading to the formation of crystal populations with different perfections and lamellar thicknesses generated by the re-organization of the heterogenous crystallinity in the presence of TiO 2 [ 15 , 25 , 26 , 55 , 58 , 96 , 97 , 98 ].…”

“…The broadness in the melting peak is related to the broadening in the distribution of the polymer chain lengths, i.e., having both long and short chains at the same time after degradation. In addition, a small shoulder at a lower temperature (around 65 °C) was formed in PHBV/500 h, which possibly reflects a small quantity of a very low M W polymer as a result of chain scission during degradation [ 15 , 58 , 96 , 97 , 98 ].…”

Composite P(3HB-3HV)-CS Spheres for Enhanced Antibiotic Efficiency

“…Given the excellent biological-related properties and effects of P(3HB-3HV) and CS, their composites are of great interest for biomedical application, particularly for tissue engineering and regenerative medicine uses. While P(3HB-3HV)-based complex architectures are thoroughly investigated for hard tissue restoration and regeneration [ 117 , 118 ], CS-based biomaterials possess an impressive and extensive potential to be used for both hard [ 119 , 120 ] and soft [ 121 , 122 ] tissue repair and healing.…”

A Brief Review on the Influence of Ionic Liquids on the Mechanical, Thermal, and Chemical Properties of Biodegradable Polymer Composites

“…There are many applications of biodegradable polymer composites; some of them have been employed in food packaging, textile, and tissue engineering applications [ 32 , 33 ]. Moreover, the incorporation of inorganic fillers into biodegradable polymers can influence the mechanical properties and hydrophobicity of the fabricated composites, which are very important for biomedical applications [ 34 ].…”