Bioceramics are used to repair, rebuild, and replace parts of the human body, e.g., bones, joints and teeth, in the form of powder, coatings or prostheses. The synthetic hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂ (HAP)] based on calcium phosphate has been widely used in the medical and dental areas due to the chemical similarity with the inorganic component of human bone tissue. In this work, hydroxyapatite nanocrystalline powders were synthesized by the solid-state reaction method and sintered with a galactomannan and chitosan blend. The bioceramics studied were prepared from 70%, 80% and 90% of hydroxyapatite with 30%, 20% and 10% of galactomannan and chitosan blends, respectively. The influence of the blend content on the bioceramics was investigated through structural, vibrational, thermal, morphological and dielectric characterizations. It was observed that the increase in the blend percentage promoted an increase in the grain size, which was followed by a decrease in the density and hardness of the samples. The sample with a higher amount of polymeric blend also presented a higher dielectric constant and higher losses.

Human hair, composed primarily of keratin, represents a sustainable waste material suitable for various applications. Synthesizing keratin nanoparticles (KNPs) from human hair for biomedical uses is particularly attractive due to their biocompatibility. In this study, keratin was extracted from human hair using concentrated sulfuric acid as the hydrolysis agent for the first time. This process yielded KNPs in both the supernatant (KNPs-S) and precipitate (KNPs-P) phases. Characterization involved scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Zeta potential analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TG). KNPs-S and KNPs-P exhibited average diameters of 72 ± 5 nm and 27 ± 5 nm, respectively. The hydrolysis process induced a structural rearrangement favoring β-sheet structures over α-helices in the KNPs. These nanoparticles demonstrated negative Zeta potentials across the pH spectrum. KNPs-S showed higher cytotoxicity (CC₅₀ = 176.67 µg/mL) and hemolytic activity, likely due to their smaller size compared to KNPs-P (CC₅₀ = 246.21 µg/mL), particularly at concentrations of 500 and 1000 µg/mL. In contrast, KNPs-P did not exhibit hemolytic activity within the tested concentration range of 32.5 to 1000 µg/mL. Both KNPs demonstrated cytocompatibility with fibroblast cells in a dose-dependent manner. Compared to other methods reported in the literature and despite requiring careful washing and neutralization steps, sulfuric acid hydrolysis proved effective, rapid, and feasible for producing cytocompatible KNPs (biomaterials) in single-step synthesis.

This work reports the reuse of waste glass as a sustainable silica source for the synthesis of mesoporous silica, as an alternative to conventional silica precursors. Silica gel was produced through alkaline dissolution of glass powder using sodium hydroxide and subsequently employed as a precursor for the synthesis of porous silica. The waste-derived glass powder and the synthesized silica-based materials were characterized to assess their structural, morphological, surface, and textural properties. XRD analysis confirmed the amorphous nature of all samples, while FTIR spectra indicated successful silica network formation with modifications in bond connectivity. SEM imaging revealed spherical particles with average diameters of approximately 0.19 ± 0.02 µm for silica gel and 0.15 ± 0.03 µm for the mesoporous silica. Zeta potential measurements indicated a negative surface charge and good colloidal stability in aqueous media. Nitrogen sorption analysis revealed that the specific surface area was limited by the low solubility of silica gel in acidic media, which prevents ideal condensation on the surface of surfactant micelles. The results demonstrate that waste glass-derived silica gel is a promising precursor, although the synthesis conditions did not yield a highly ordered mesostructure, highlighting the need for further control of precursor solubility and pH.