This chapter aims to establish the key factors for technological optimization of biogenic calcium phosphate synthesis from marine and land resources. Three natural calcium sources-marble, seashell and bovine bone-were considered as raw materials. The proposed materials are suitable candidates for the synthesis of bone substitutes similar to the inorganic bone component. The synthesis processes were developed based on the investigations of thermal phenomena (TGA-DSC analysis) that can occur during thermal treatments. By this method, we were able to determine the optimum routes and temperatures for the complete dissociation of calcium carbonate as well as risk-free deproteinization of bovine bone. An exhaustive characterization, performed with modern and complementary techniques such as morphology (SEM), composition (EDS, XRF) and structure (FT-IR, XRD), is presented for each precursor. The final chemical composition of ceramic products can be modulated through a careful control of the key parameters involved in the conversion, in order to create long-term performant biphasic apatite biomaterials, with broad medical applicability. Identifying the suitable strategies for this modulation contributes to an appreciable advance in orthopedic tissue engineering.
The intersection of the bone tissue reconstruction and additive manufacturing fields promoted the advancement to a prerequisite and new feedstock resource for high-performance bone-like-scaffolds manufacturing. In this paper, the proposed strategy was directed toward the use of bovine-bone-derived hydroxyapatite (HA) for surface properties enhancement and mechanical features reinforcement of the poly(lactic acid) matrix for composite filaments extrusion. The involvement of completely naturally derived materials in the technological process was based on factors such as sustainability, low cost, and a facile and green synthesis route. After the HA isolation and extraction from bovine bones by thermal processing, milling, and sorting, two dependent parameters—the HA particles size (<40 μm, <100 μm, and >125 μm) and ratio (0–50% with increments of 10%)—were simultaneously modulated for the first time during the incorporation into the polymeric matrix. The resulting melt mixtures were divided for cast pellets and extruded filaments development. Based on the obtained samples, the study was further designed to examine several key features by complementary surface–volume characterization techniques. Hence, the scanning electron microscopy and micro-CT results for all specimens revealed a uniform and homogenous dispersion of HA particles and an adequate adhesion at the ceramic/polymer interface, without outline pores, sustained by the shape and surface features of the synthesized ceramic particles. Moreover, an enhanced wettability (contact angle in the ~70−21° range) and gradual mechanical takeover were indicated once the HA ratio increased, independent of the particles size, which confirmed the benefits and feasibility of evenly blending the natural ceramic/polymeric components. The results correlation led to the selection of optimal technological parameters for the synthesis of adequate composite filaments destined for future additive manufacturing and biomedical applications.
Bone tissue engineering is constantly in need of new material development with improved biocompatibility or mechanical features closer to those of natural bone. Other important factors are the sustainability, cost, and origin of the natural precursors involved in the technological process. This study focused on two widely used polymers in tissue engineering, namely polylactic acid (PLA) and thermoplastic polyurethane (TPU), as well as bovine-bone-derived hydroxyapatite (HA) for the manufacturing of core-shell structures. In order to embed the ceramic particles on the polymeric filaments surface, the materials were introduced in an electrical oven at various temperatures and exposure times and under various pressing forces. The obtained core-shell structures were characterized in terms of morphology and composition, and a pull-out test was used to demonstrate the particles adhesion on the polymeric filaments structure. Thermal properties (modulated temperature and exposure time) and the pressing force's influence upon HA particles' insertion degree were evaluated. More to the point, the form variation factor and the mass variation led to the optimal technological parameters for the synthesis of core-shell materials for prospect additive manufacturing and regenerative medicine applications.Coatings 2020, 10, 283 2 of 18 importance. Among these, PLA was widely used, mainly due to its biocompatibility with the human organism and the advantageous synthesis alternative from sustainable natural resources (e.g., beet or maize) [14]. Along with PLA, TPU was remarked in the additive manufacturing technology [15]. The TPU applications in the medical field spread from blood vessels, implants, and prosthetics, to scaffolding in tissue engineering, dialysis membranes, or breast implants [16].Furthermore, naturally derived hydroxyapatite (HA) is a bioactive ceramic, with similar chemical and structural properties to the mineral component of the natural bone tissue, and exceptional biocompatibility and osteoconductivity. HA can be synthesized from various renewable resources (e.g. fish, sheep, cattle or bovine bones [17,18] or marine shells [19,20]).Along with the development of new biomaterials, the cost-efficient and highly performant processing techniques for final products manufacturing are also in need of improvement. Additive manufacturing (AM) or 3D printing can be considered 21st century technology due to the possibility to attain patient-customized and adapted products [14]. However, the most widely and accessible used technique in orthopedics is fused deposition modeling (FDM) or fused filler fabrication (FFF) [8,14,21,22], which provide 3D scaffolds with a well-defined design by extruding a digital 3D model from thermoplastic polymeric materials heated to their melting point [22].This study aims to provide a new core-shell material that can be used in the FDM technique, targeted due to its rigorous control of parameters (temperature, bed temperature, feed rate, printing speed, etc.) [23][24][25][26][27].Therefore, thi...
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