Abstract
For the first time, composite coatings based on poly(dimethylsiloxane-block-ε-caprolactone) copolymer and tricalcium phosphate were obtained on stainless steel plates by using the electrophoretic deposition technique. The effect of different deposition times on the final characteristics of the resulting coatings was also studied. Block copolymers were obtained through a combination of anionic and ring-opening polymerization, with good homogeneity and chemical composition (Ð < 1.3 and wPCL = 0.39). The composites obtained at different electrophoretic deposition times revealed a linear dependence between the deposited weight and time during assays. When immersing in simulated body fluid, a higher amount of residual solids ( ∼ 20 %) were observed by thermogravimetric analysis after 7 days of immersion. Scanning electron microscopy micrographs revealed a porous microstructure over the metallic substrate and the absence of micro-cracks, and X-ray diffraction patterns exhibited diffraction peaks associated with a hydroxyapatite layer. Finally, energy-dispersive X-ray analysis revealed values of the Ca/P ratio between 1.40 and 1.50 in samples, which are closer to the stoichiometric hydroxyapatite values reported in hard tissues. The results obtained in this article confirm the usefulness of poly(dimethylsiloxane-block-ε-caprolactone) copolymer and cheaper tricalcium phosphate as precursors of compact and homogenous coatings obtained by electrophoretic deposition, which yields useful substrates for hydroxyapatite growth.
Highlights
Biocompatible materials play an important role in the area of tissue engineering mainly because they give a new vision of the development materials destined to the repair and regeneration of tissues or the replacement of missing human bones and teeth, among other applications (Qu et al, 2019)
Hexamethyl monomer (D3, Sigma-Aldrich, %) for anionic polymerization and ε-caprolactone (ε-CL, SigmaAldrich, %) for block copolymer synthesis were purified by mixing with the calcium hydride powder (CaH2, Sigma-Aldrich, 95 %), followed by heating and distilling under vacuum according to conventional procedures
This value is similar to the values reported in the scientific literature for the synthesis of homopolymers and copolymers based of ε-CL using ring-opening polymerization (ROP) (Duruncan and Brown, 2001; Ma et al, 2001; Redondo, 2018; Wang et al, 2019)
Summary
Biocompatible materials play an important role in the area of tissue engineering mainly because they give a new vision of the development materials destined to the repair and regeneration of tissues or the replacement of missing human bones and teeth, among other applications (Qu et al, 2019). One of the main challenges for polymers researchers is to develop non-toxic, biodegradable, bioactive, and osteoconductive materials with good mechanical properties at the time of application. For such a purpose, composites formed from two or more materials with excellent properties (polymers, Bioactive Coatings Based on Copolymers ceramics, and bioglasses) are widely used in tissue engineering (Yeong et al, 2010; Qu et al, 2019; Bonetti et al, 2020; Ninago et al, 2020; Redondo et al, 2020). Various methodologies capable of developing these new materials have appeared, such as melt mixing (Pishbin et al, 2015), dissolution-leaching (Jordan et al, 2005), and electrophoretic deposition (EPD) technique (ElGhannam, 2005; Cabanas-Polo and Boccaccini, 2015; Redondo et al, 2020), among others
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