Surface modification of activated carbon cloth with calcium silicate and hydroxyapatite: bioactive composite material.

In this study new compounds consisting of activated carbon cloths (ACC) modified with calcium silicate (CaSiO3) were prepared for hydroxyapatite (HAP) generation. ACC samples were oxidized with 8 M HNO3 at different times (15 min and 2 h), to increase oxygenated functional groups. The CaSiO3 fine powders were prepared by chemical coprecipitation using Ca(NO3)2∙4H2O and Si(OC2H5)4, and 5 M NaOH was used as precipitant. The resulting powders were mixed with ethanol by ultrasound stirring and the previously oxidized activated carbon fibers were placed leaving under stirring for 30 min to allow particle dispersion. Once the formed compounds were dried, the samples were immersed in a simulated body fluid (SBF) solution for 21 days in conical tubes at 36.5 °C to allow the HAP formation on the ACC/CaSiO3 composite surface. The results indicated that the increase in oxidation time improves HAP formation on the surface from ACC/CaSiO3 compounds and this bioactive composite may be a potential material for bone regeneration.

O-carboxymethyl chitosan/gelatin/silver-copper hydroxyapatite composite films with enhanced antibacterial and wound healing properties.

Wound dressing composite films of O-carboxymethyl chitosan (OCMC) and gelatin were prepared and mixed with hydroxyapatite (HA) composited with Silver (Ag) and Copper (Cu) at different concentrations. The chemical, thermal, morphological, and biological properties of the composite films were studied. The analysis by FTIR confirmed the presence of interactions between gelatin and OCMC, and at the same time, the polymer matrix interactions with Ag-Cu/HA complex. The inclusion of nanoparticle to the composite was associated with an improvement of the thermal stability, morphological roughness, a 9-12% more hydrophobic behavior (composite C1, C5, and C8), increase in antibacterial activity from 23.2 to 33.1% for gram negative bacteria and from 37.28 to 40.59% for gram positive bacteria, and with a cell viability greater than 100% for 24 and 72 h. The films obtained can serve as a wound healing dressing and regenerating biomaterial.

Goethite-titania composite: disinfection mechanism under UV and visible light.

Goethite-titania (α-FeOOH-TiO2) composites were prepared by co-precipitation and mechanical milling. The structural, morphological and optical properties of as-synthesized composites were characterized by X-ray powder diffraction, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy, respectively. α-FeOOH-TiO2 composites and TiO2-P25, as reference, were evaluated as photocatalysts for the disinfection of Escherichia coli under UV or visible light in a stirred tank reactor. α-FeOOH-TiO2 exhibited better photocatalytic activity in the visible region than TiO2-P25. The mechanical activation increased the absorption in the visible range of TiO2-P25 and the photocatalytic activity of α-FeOOH-TiO2. In the experiments with UV light and α-FeOOH-TiO2, mechanically activated, a 5.4 log-reduction of bacteria was achieved after 240 min of treatment. Using visible light the α-FeOOH-TiO2 and the TiO2-P25 showed a 3.1 and a 0.7 log-reductions at 240 min, respectively. The disinfection mechanism was studied by ROS detection and scavenger experiments, demonstrating that the main ROS produced in the disinfection process were superoxide radical anion, singlet oxygen and hydroxyl radical.