Nucleation and growth of biomimetic apatite layers on 3D plotted biodegradable polymeric scaffolds : effect of static and dynamic coating conditions

Apatite layers were grown on the surface of newly developed starch/polycaprolactone (SPCL)-based scaffolds by a 3D plotting technology. To produce the biomimetic coatings, a sodium silicate gel was used as nucleating agent, followed by immersion in a simulated body fluid (SBF) solution. After growing a stable apatite layer for 7 days, the scaffolds were placed in SBF under static, agitated (80 strokes min!1) and circulating flow perfusion (Q = 4 ml min!1; tR = 15 s) for up to 14 days. The materials were characterized by scanning electron microscopy/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and thin-film X-ray diffraction. Cross-sections were obtained and the coating thickness was measured. The elemental composition of solution and coatings was monitored by inductively coupled plasma spectroscopy. After only 6 h of immersion in SBF it was possible to observe the formation of small nuclei of an amorphous calcium phosphate (ACP) layer. After subsequent SBF immersion from 7 to 14 days under static, agitated and circulating flow perfusion conditions, these layers grew into bone-like nanocrystalline carbonated apatites covering each scaffold fiber without compromising its initial morphology. No differences in the apatite composition/chemical structure were detectable between the coating conditions. In case of flow perfusion, the coating thickness was significantly higher. This condition, besides mimicking better the biological milieu, allowed for the coating of complex architectures at higher rates, which can greatly reduce the coating step.The authors acknowledge the Portuguese Foundation for Science and Technology (PhD grant to A.L.O., SFRH/BD/10956/2002 and post-doctoral Grant to R.A.S., SFRH/BPD/17151/2004, under the POCTI Program). This work was partially supported by FCT through POCTI and/or FEDER programmes and also partially supported by the EU Project HIPPOCRATES (NMP3-CT-2003-505758) and EXPERTISSUES (NMP-CT-2004-500283)

Apatite Glass-Ceramics: A Review

The authors would like to thank Cera Dynamics Limited, part of the James Kent Group and the Institute of Dentistry (Queen Mary University of London) for jointly funding TD

Micro-computed tomography (μ-CT) as a potential tool to assess the effect of dynamic coating routes on the formation of biomimetic apatite layers on 3D-plotted biodegradable polymeric scaffolds

This work studies the influence of dynamic biomimetic coating procedures on the growth of bonelike apatite layers at the surface of starch/polycaprolactone (SPCL) scaffolds produced by a 3D-plotting technology. These systems are newly proposed for bone Tissue Engineering applications. After generating stable apatite layers through a sodium silicate-based biomimetic methodology the scaffolds were immersed in Simulated Body Fluid solutions (SBF) under static, agitation and circulating flow perfusion conditions, for different time periods. Besides the typical characterization techniques, Micro-Computed Tomography analysis (μ-CT) was used to assess scaffold porosity and as a new tool for mapping apatite content. 2D histomorphometric analysis was performed and 3D virtual models were created using specific softwares for CT reconstruction. By the proposed biomimetic routes apatite layers were produced covering the interior of the scaffolds, without compromising their overall morphology and interconnectivity. Dynamic conditions allowed for the production of thicker apatite layers as consequence of higher mineralizing rates, when comparing with static conditions. μ-CT analysis clearly demonstrated that flow perfusion was the most effective condition in order to obtain well-defined apatite layers in the inner parts of the scaffolds. Together with SEM, this technique was a useful complementary tool for assessing the apatite content in a non-destructive way

Sodium polystyrene sulfonate template assisted hydrothermal synthesis of hydroxyapatite nanorods

1084-1089Hydroxyapatite nanoparticles (nHAp) have been synthesized by benign hydrothermal reaction from the aqueous mixture of Ca(NO3)2·4H2O and (NH4)2HPO4 solutions in the presence of non-toxic sodium polystyrene sulfonate (PSS) template. The pH of starting precursors has been adjusted to 10.5 before hydrothermal treatment at 100°C for 1, 2 and 3 h. The added PSS template generates the largely negative surface of dicalcium phosphate dihydrate (DCPD) precursor, resulting in minimization of precursor agglomeration and promoting the hydrothermal growth of nHAp along preferential c-axis as rod-shaped crystals. The crystallite sizes along 002-plane of nHAp synthesized with and without PSS template are 47.1 and 29.5 nm, respectively. With longer hydrothermal treatment time, larger crystallite size of nHAp is obtained. In vitro cytotoxicity of the synthesized nHAp has been evaluated by MTT assay using African green monkey kidney fibroblast cells, in which the nHAp exhibits low cytotoxicity. Antibacterial activities of the synthesized nHAp against S.aureus and E.coli have been tested. Due to the presence of largely negative surface, the nHAp could inhibit only the gram-positive S.aureus, creating a clear zone of about 9.5 mm

Facile preparation of copper impregnated aluminum pillared montmorillonite: nanoclays for wastewater treatment

Copper impregnated aluminum pillared montmorillonites (Cu-iAlpill-MMTs) were prepared by adding Cu2+ solution into dried aluminum polyohydroxy cation intercalated montmorillonite using various Cu2+ concentrations, i.e. 4, 7, 10 and 13 wt% and then calcining at 500°C. The Cu-iAlpill-MMTs possessed slit-liked mesopores with pore diameters of 3.3–3.8 nm and ~6–35 nm as observed from the nitrogen adsorption isotherms. The mesopore quantities of Cu-iAlpill-MMTs gradually decreased with the increase of impregnated Cu2+ concentrations. The impregnated CuO occupied not only the interior interlayers, but also the exterior surfaces of Cu-iAlpill-MMTs. The Cu-iAlpill-MMTs with 10 and 13 wt% of impregnated Cu2+ could inhibit the growth of Escherichia coli. The Cu-iAlpill-MMTs effectively acted as the heterogeneous catalyst for removal reactive orange 16 (RO16) in Fenton or photo-Fenton oxidation treatments. The higher impregnated Cu2+ and/or the longer treatment time brought about the higher percentage of RO16 removal

Facile synthesis of chitosan/CuO nanocomposites for potential use as biocontrol agents

Chitosan/CuO nanocomposites (Chi/CuO) were prepared by facile and eco-friendly technique. The 2%w/v chitosan solution was mixed with 0.5 %w/w sodium tripolyphosphate (STPP), resulting in the formation of ionically crosslinked chitosan. The crosslinked chitosan was soaked in an aqueous solution containing 0.001, 0.01 or 0.1 mol/L CuSO4·5H2O for 24 hrs, in which the Cu2+ ions were absorbed into the chitosan network, forming as the chitosan/Cu2+ precursors. The chitosan/Cu2+ precursors were hydrothermally reacted in two different basic media, i.e. NaOH and NH4OH, at 100°C for 24 hrs, resulting in the nano-sized CuO crystals hydrothermally grew and embedded in the crosslinked chitosan matrix. The CuO grown in the NaOH possessed larger crystallite size and higher crystallinity than that in the NH4OH. In addition, the CuO crystallite size in the nanocomposites increased with the increase of initial concentration of Cu2+ starting agent due to the increase of Cu2+ quantity in the chitosan/Cu2+ precursors. The chitosan/CuO nanocomposites prepared by using 0.01 and 0.1 mol/L Cu2+ could exhibit the antibacterial activities after intimate contact with Staphylococcus aureus and Escherichia coli under JIS L 1902:1998 (Qualitative) test method, indicating their potential use as biocontrol agents