Continuous Hydrothermal Flow Synthesis and Characterisation of Nano-Bioceramics and their Rapid Consolidation Using Spark Plasma Sintering

PhDAccidents, surgery and disease often result in the use of biomimetic materials that can replace human hard tissue and calcium phosphate bioceramics are ideally suited for this purpose. Indeed, biological apatite is a poorly crystalline, non-stoichiometric carbonated hydroxyapatite. The composition, crystallinity and particle size of synthetic calcium phosphate bioceramics directly affect their biological, mechanical and thermal performance. Hence control over these properties in synthetic bioceramics is essential in order to mimic human hard tissue in functionality. The existing methods of synthesis of calcium phosphate bioceramics are multi-step, time consuming and require strict control over synthesis conditions. Therefore, there is a requirement of a one-step, rapid synthesis technology which allows control over particle properties. The continuous hydrothermal flow synthesis (CHFS) technique addresses all such issues but it has not been used to synthesise calcium phosphate based nano-bioceramics. The work in this thesis involves the use of CHFS technology to synthesise calcium phosphate bioceramics. It was demonstrated that the rapid crystallising environment in a CHFS system resulted in phase-pure crystalline hydroxyapatite (HA). Traditionally required long ageing times and heat-treatment were avoided. Furthermore, variations in the CHFS system parameters were correlated with properties of the synthesised nanobioceramics. The CHFS system was also used to substitute biologically beneficial ions (C03'-, Si044-, Mg2+ and Zn2) into HA. Some ionic substitutions affected thermal stability and phase composition. For example, increase in magnesium contents in solution resulted in precipitation of a phase pure Mg-Whitlockite phase. Conventional consolidation methods of HA powders require several hours of exposure to elevated temperatures which results in large grains, phase decomposition and poor mechanical properties. Spark Plasma Sintering on the other hand is capable of very high heating and cooling rates. Phase-pure and ion-substituted calcium phosphates and zirconia-hydroxyapatite phase mixtures were spark plasma sintered to high densities with these materials displaying good mechanical properties

Synthesis of cerium, zirconium, and copper doped zinc oxide nanoparticles as potential biomaterials for tissue engineering applications

A novel eco-friendly high throughput continuous hydrothermal flow system was used to synthesise phase pure ZnO and doped ZnO in order to explore their properties for tissue engineering applications. Cerium, zirconium, and copper were introduced as dopants during flow synthesis of ZnO nanoparticles, Zirconium doped ZnO were successfully synthesised, however secondary phases of CeO and CuO were detected in X-ray diffraction (XRD). The nanoparticles were characterised using X-ray diffraction, Brunauer-Emmett-Teller (BET), Dynamic Light scattering Measurements, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and RAMAN spectroscopy was used to evaluate physical, chemical, and structural properties. The change in BET surface area was also significant, the surface area increased from 11.35 (ZnO_2) to 26.18 (ZrZnO_5). However. In case of CeZnO_5 and CuZnO_5 was not significant 13.68 (CeZnO_5) and 12.16 (CuZnO_5) respectively. Cell metabolic activity analysis using osteoblast-like cells (MG63) and human embryonic derived mesenchymal stem cells (hES-MP) demonstrated that doped ZnO nanoparticles supported higher cell metabolic activity compared to cells grown in standard media with no nanoparticles added, or pure zinc oxide nanoparticles. The ZrZnO_5 demonstrated the highest cell metabolic activity and non-cytotoxicity over the duration of 28 days as compared to un doped or Ce or Cu incorporated nanoparticles. The current data suggests that Zirconium doping positively enhances the properties of ZnO nanoparticles by increasing the surface area and cell proliferation. Therefore, are potential additives within biomaterials or for tissue engineering applications

Synthesis and in-vitro cytotoxicity analysis of microwave irradiated nano-apatites

NOTICE: this is the author’s version of a work that was accepted for publication in Ceramics International. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in CERAMICS INTERNATIONAL, [VOL 39, ISSUE 4, (2013)] DOI 10.1016/j.ceramint.2012.11.017Nano-sized calcium deficient apatite (CDA) micelles were synthesized through microwave assisted the wet precipitation technique. Cetyltrimethylammonium bromide (CTAB) was employed as surface template to furnish the CDA particles with tailored size and shape. As-precipitated CDA was heat treated to observe the effect of heat treatment temperature on the interatomic rearrangement of entities within the apatite lattice. This transformation is responsible for conversion of CDA to β-tricalcium phosphate (β-TCP) at specific temperature. The phase purity, particles size, morphology and transformation kinetics were analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). In-vitro studies were performed on β-TCP with three cell lines: osteoblasts, HeLa, and SF 767. The results showed that nano-sized particles were successfully synthesized in short time. The cells had appreciable proliferation/attachment on the surface of these nano-particles. It is concluded that the microwave irradiated synthesized β-TCP has good capacity in terms of biocompatibility and has the potential to be used in hard tissue regeneration applications.Nano-sized calcium deficient apatite (CDA) micelles were synthesized through microwave assisted the wet precipitation technique. Cetyltrimethylammonium bromide (CTAB) was employed as surface template to furnish the CDA particles with tailored size and shape. As-precipitated CDA was heat treated to observe the effect of heat treatment temperature on the interatomic rearrangement of entities within the apatite lattice. This transformation is responsible for conversion of CDA to β-tricalcium phosphate (β-TCP) at specific temperature. The phase purity, particles size, morphology and transformation kinetics were analyzed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). In-vitro studies were performed on β-TCP with three cell lines: osteoblasts, HeLa, and SF 767. The results showed that nano-sized particles were successfully synthesized in short time. The cells had appreciable proliferation/attachment on the surface of these nano-particles. It is concluded that the microwave irradiated synthesized β-TCP has good capacity in terms of biocompatibility and has the potential to be used in hard tissue regeneration applications

Handbook of ionic substituted hydroxyapatites

Elsevie

Hydrothermal deposition of high strength calcium phosphate coatings on magnesium alloy for biomedical applications

Magnesium and Mg-alloys are suitable replacement to metallic implants (Titanium, stainless steel, Co-Cr alloys) in terms of stress shielding effect and repeated surgery requirement. However, the only hindrance in their successful use as biodegradable orthopedic implants is their high corrosion rates in physiological environment. Thus, in present study, we developed the single step hydrothermal process to deposit bioactive coatings that may lower the corrosion rate. Highly crystalline, cytocompatible, bioresorbable and high strength monetite (CaHPO4) coating successfully produced on Ca-containing Mg-alloy via hydrothermal process. Deposition parameters have significant influence on coatings morphology and degree of crystallinity. XRD pattern indicates sharp, intense and well-defined peaks of monetite along with minor peaks of brucite and spinel phases. SEM study reveals that compact and defects free coatings were deposited at 100 °C. FTIR analysis showed all characteristic peaks that confirms the presence of monetite. Corrosion behavior of coated and uncoated specimen were analyzed using potentiodynamic polarization scan in simulated body fluid (SBF) at 37 °C. Calcium phosphate (CaP) coating significantly improve the degradation rate of Mg-alloy. Corrosion rate was 80% lower in CaP coated Mg-alloy specimens than bare Mg-alloy. Adhesion strength of coatings was determined using lap shear test demonstrating a cohesive failure at 21.89 MPa stress. Furthermore, cytotoxicity of coated and uncoated alloy was assessed by using Alamar Blue (AB) assay on NIH3T3 mouse fibroblast cell line for 9 days indicate no significant difference in proliferation of cells for CaP coated Mg-alloy and positive control. These results suggest that hydrothermal method reported here can potentially be used to deposit compact, highly crystalline, bioresorbable, cytocompatible and protective coatings with high adhesion strength on intricate geometries for degradable implant applications

Bioactive Nano Hydroxyapatites for Orbital Floor Repair and Regeneration

Bioactive nano-hydroxyapatites have been synthesised for orbital floor repair and regeneration. Hydroxyapatite (HA) is widely used for bone repair and regeneration. It is composed of multiple anionic and cationic species, such as carbonate, fluoride, phosphate, sodium, magnesium, silicon and citrate. However, the development of bioactive materials that can repair and regenerate bone is crucial for orbital floor fracture repair. Different ionic-substituted hydroxyapatites that included carbonate, fluoride and citrate were prepared by using a low-temperature hydrothermal flow process and their chemical and physical properties evaluated. Biological properties were evaluated by analysing cell viability of these synthesised materials by Alamar Blue cell metabolic activity assay with two different cell lines (MG63 and HTERT-BMSC’s). Results confirmed that ionic substitution with fluoride and citrate improved biocompatibility and cell viability of synthesised hydroxyapatites

In situ reaction kinetic analysis of dental restorative materials

The objective of this study was to evaluate in situ structural and thermal changes of dental restorative materials at periodical time intervals. The commercial materials included zinc oxide eugenol (ZOE), zinc phosphate type I (ZnPO4), glass ionomer cement type II (GIC) and resin-based nano-omposite (Filtek Z350 XT). These materials were processed according to manufacturer’s instructions. For the structural analysis Fourier transform infrared spectroscopy (FTIR) was used at high resolution. TGA was used to evaluate thermal weight-loss. The FTIR spectra were collected at periodic time intervals. FTIR spectra showed that with time passing all materials exhibited an increase in peak intensities and a new appearance of shoulders and shifting of peaks for example, ZnPO4 (P-O), ZOE (C═O, C═N, C-O-C), GIC (COO–, C-H, Si-OH), composites (C═O, C═C, C═N, C-N-H). The peaks were replaced by bands and these bands became broader with time interval. Composites showed a degree of conversion and new peaks corresponded to the cross-linking of polymer composites. TGA analysis showed that significant changes in weight loss of set materials were observed after 24 h, where ZOE showed continuous changes in thermal degradation. The spectral changes and thermal degradation with time interval elucidated in situ setting behaviour and understanding of their bonding compatibility with tooth structure and change in relation to time

Identification of anti-cancer potential of doxazocin:Loading into chitosan based biodegradable hydrogels for on-site delivery to treat cervical cancer

In this study, an effective, biocompatible and biodegradable co-polymer comprising of chitosan (CS) and polyvinyl alcohol (PVA) hydrogels, chemically crosslinked and impregnated with doxazocin, is reported. The chemical structural properties of the hydrogels were evaluated by Fourier Transform Infrared spectroscopy (FTIR) and physical properties were analysed by scanning electron microscopy (SEM). The swelling behaviour is an important parameter for drug release mechanism and was investigated to find out the solution absorption capacity of the synthesized hydrogels. MTT assay revealed that doxazocin loaded hydrogels significantly hindered the cell viability. Flow cytometry analysis was performed to analyse the effect of 8CLH and 4CLH on regulation of cell cycle. Moreover, in vivo anti-cancer potential of synthesized hydrogels was assessed by CAM Assay. Results displayed that 8CLH with 1 mg/ml of doxazocin had prominently decreased the angiogenesis and significantly increased the number of cells in G1 phase of cell cycle. These results declared that 8CLH will be a good addition among hydrogels used for treatment of cancer by onsite delivery of drug

Osteogenic Induction with Silicon Hydroxyapatite Using Modified Autologous Adipose Tissue-Derived Stromal Vascular Fraction: In Vitro and Qualitative Histomorphometric Analysis

Large bone defects requiring invasive surgical procedures have long been a problem for orthopedic surgeons. Despite the use of autologous bone grafting, satisfactory results are often not achieved due to associated limitations. Biomaterials are viable alternatives and have lately been used in association with Stromal Vascular Fraction (SVF), stem cells, and signaling factors for bone tissue engineering (BTE). The objective of the current study was to assess the biocompatibility of Silicon Hydroxyapatite (Si-HA) and to improve osteogenic potential by using autologous adipose-derived SVF with Si-HA in a rabbit bone defect model. Si-HA granules synthesized using a wet precipitation method were used. They were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). A hemolysis assay was used to assess the hemolytic effects of Si-HA, while cell viability was assessed through Alamar Blue assay using MC3T3 mouse osteoblasts. The osteogenic potential of Si-HA both alone and with enzymatically/non-enzymatically-derived SVF (modified) was performed by implantation in a rabbit tibia model followed by histomorphometric analysis and SEM of dissected bone after six weeks. The results showed that Si-HA granules were microporous and phase pure and that the addition of Silicon did not influence Si-HA phase composition. Si-HA granules were found to be non-hemolytic on the hemolysis assay and non-toxic to MC3T3 mouse osteoblasts on the Alamar Blue assay. Six weeks following implantation Si-HA showed high biocompatibility, with increased bone formation in all groups compared to control. Histologically more mature bone was formed in the Si-HA implanted along with non-enzymatically-derived modified SVF. Bone formation was observed on and around Si-HA, reflecting osseointegration. In conclusion, Si-HA is osteoconductive and promotes osteogenesis, and its use with SVF enhances osteogenesis

Thyroxin releasing chitosan/collagen based smart hydrogels to stimulate neovascularization

The development of new biomaterials with tailored properties is highly desired in tissue engineering field. The neovascularization is essential part of tissue regeneration which provides food and nutrients to cells. There is a real need for proangiogenic biomaterials to assist wound healing. The ideal dressing should be inexpensive and achieve rapid healing with minimal inconvenience to the patient. In this paper, new porous thyroxin containing pro-angiogenic hydrogels were generated via freeze gelation protocol. The chemical structural analysis of the synthesized hydrogels was investigated by Fourier Transform Infrared (FTIR) spectroscopy. The morphology and pore dimensions were studied by scanning electron microscopy (SEM). In swelling studies, 10 μg thyroxine loaded hydrogel (TLH-10) showed greater degree of swelling as compared to 1 μg loaded thyroxine material (TLH-1) and control. The degradation studies were tested in three different media, i.e. phosphate buffer saline (PBS), lysozyme and hydrogen peroxide and relatively higher degradation was seen in hydrogen peroxide. The synthesized materials were implanted on the chick chorioallantoic membrane to investigate their angiogenic potential. The TLH-1 hydrogel stimulated angiogenesis greater than the TLH-10; in this case blood vessels were attached and very much grown into the scaffold