Poly(3-hydroxybutyrate) (PHB) is a biodegradable and thermoprocessable biopolymer, making it a promising candidate for applications in tissue engineering. In the present study a structural characterization and in vitro evaluation were performed on PHB scaffolds produced by additive manufacturing via selective laser sintering (SLS), followed by post-printing functionalization with osteogenic growth peptide (OGP) and its C-terminal sequence OGP(10-14). The PHB scaffolds were characterized, including their morphology, porosity, thermal and mechanical properties, moreover OGP release. The results showed that SLS technology allowed the sintering of the PHB scaffolds with a hierarchical structure with interconnected pores and intrinsic porosity (porosity of 55.8 ± 0.7% and pore size in the 500-700 μm range), and good mechanical properties. Furthermore, the SLS technology did not change thermal properties of PHB polymer. The OGP release profile showed that PHB scaffold promoted a controlled release above 72 h. In vitro assays using rat bone marrow stem cells showed good cell viability/proliferation in all the PHB scaffolds. Additionally, SEM images suggested advanced morphological differentiation in the groups containing osteogenic growth peptide. The overall results demonstrated that PHB biopolymer is potential candidate for 3D printing via SLS technology, moreover the OGP-containing PHB scaffolds showed ability to sustain cell growth to support tissue formation thereby might be considered for tissue-engineering applications.

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Although bone autografts have been routinely used as "gold standard" for reconstruction/ replacement bone defects, because they have osteogenic, osteoinductive, osteoconductive properties, they have a high number of viable cells and are rich in growth factors. However, the use of autograft is limited by several factors, being one of them the insufficient amount of donor tissue. Therefore, bone substitute materials have been extensively studied in order to develop an ideal material for substitution of bone grafts, due to some disadvantages presented by autografts, allografts and xenografts, such as poor bone quality, an inadequate amount of bone and possible immunogenicity for allografts and xenografts, which limit the use of these grafts in specific surgical protocols. These disadvantages have led tissue engineering and biotechnology to develop new materials and promising methods for tissue repair, especially for bone tissue. Thus, bone substitutes, synthetic and/or biotechnologically processed have become potential materials for clinical applications in different areas of health. An ideal bone substitute (BS) material should provide a variety of shapes and sizes with suitable mechanical properties to be used in sites where there are impact loading; moreover, these materials should be biocompatible, osteoconductive, preferably being resorbable and replaced by new bone formation. In general, resorbable BS materials are preferred, since these materials are expected to preserve the increased bone volume during the reconstruction and simultaneously are gradually replaced by newly formed bone. Synthetic materials, denominated as alloplastics, may act as scaffolds for bone cells providing tissue growth inside the respective material.

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Calcium phosphate cement has been widely investigated as a bone graft substitute due to its excellent self-setting ability, biocompatibility, osteoconductivity and moldability. In addition, mesoporous materials have been studied as potential materials for application in medical devices due to their large surface area, which is capable of loading numerous biological molecules, besides being bioactive. In this study, bone β-TCP-MCPM-based injectable cement with mesoporous silica particles was synthesized and characterized in terms of its mechanical properties, microstructure, porosity, injectability, in vitro bioactivity and degradability; together with toxicity effects in CHO-K1 cell culture. The results showed that the β-TCP-MCPM cement is bioactive after soaking in simulated body fluid solution, and mesoporous silica particles provided better physicochemical properties compared with silica-free cement. Toxicity assays showed low CHO-K1 cell viability after treatment with more concentrated extracts (200 mg ml). However, this behavior did not compromise the reproductive capacity and did not promote significant DNA damage in those cells. In conclusion, the β-TCP-MCPM cement associated with mesoporous silica might be considered as a potential bone substitute for the repair and regeneration of bone defects.

Guided bone regeneration (GBR) technique helps to restore bone tissue through cellular selectivity principle. Currently no osteoinductive membrane exists on the market. Osteogenic growth peptide (OGP) acts as a hematopoietic stimulator. This association could improve the quality of bone formation, benefiting more than 2.2 million patients annually. The objective of this work was to develop membranes from ureasil‐polyether materials containing OGP. The membranes were characterized by differential scanning calorimetry (DSC) and small angle X‐ray scattering (SAXS). OGP was synthesized by the solid phase method. Sterilization results using gamma radiation at 24 kGy did not change the structure of the material, as confirmed by DSC. The SAXS technique revealed the structural homogeneity of the matrix. OGP was incorporated in 66.25 × 10−10 mol and release results showed that the ureasil‐PPO400/PEO500 and ureasil‐PPO400/PEO1900 membranes released 7% and 21%, respectively, after 48 h. In vivo results demonstrated that the amount and quality of bone tissue formed in the bone defects in the presence of ureasil‐polyether membranes with OGP were similar to commercial collagen material with BMP. The results allow us to conclude that membranes with OGP have characteristics that make them potential candidates for the GBR.

Synthetic nanohydroxyapatite (nHA) is a prominent material to be applied in bone tissue engineering devices, due to nHA similarity with the main component of the bone inorganic phase, biocompatibility, biodegradability, and bioactivity. The specific characteristics of the nHA crystals are dependent on the synthesis method. Therefore, the aim of this work was to evaluate the structure of the nHA obtained through chemical precipitation, for the understanding of nHA physico-chemical and biological properties. nHA was produced by dropwise addition of 1600 mL of 0.7 M aqueous Ca(NO 3) 2 .4H 2 O (pH 5.5) on 1100 mL of 0.5 M (NH 4) 2 HPO 4 (pH 10.4, adjusted with concentrated NH 3) under stirring at 80°C. The reaction mixture was aged 24 h then vacuum filtered and washed with water and ethanol. The precipitated nHA was dried at 80 °C for 24 h. The structure obtained nHA was characterized by X-Ray Diffraction and the Rietveld refinement method, Transmission Electron Microscopy and Fourier Transform Infrared Spectroscopy. Preliminary results indicate that the material consisted of calcium deficient hydroxyapatite nanocrystals with lattice parameters a=b=9.43019 Å and c=6.88162 Å, and c-axis preferentially oriented. Nanoparticles, shaped as rods, presented mean crystallite size of ~21 nm (~47 nm length and ~8 nm width) and specific surface area of 90.1 m 2 /g. According to the obtained results the method of synthesis of nHA seems to be reproducible and effective to prepare large quantities of nHA to be evaluated as biomaterials.