The impact of Cu(II) ions doping in nanostructured hydroxyapatite powder: A finite element modelling study for physico-mechanical and biological property evaluation

The synthesis of doped nanostructured materials with multifunctional properties and improved biocompatibility have immense potential for biomedical applications. In this present study, a facile wet chemical precipitation method was employed to synthesize hydroxyapatite (HAp) and different concentrations copper doped HAp, and Cu_x-HAp (x = 1, 2, and 4 mol%) nano materials. Sophisticated analytical and spectroscopic techniques were employed to confirm its physico-chemical properties, and morphological features. The synthesized HAp, Cu_x-HAp were further studied as a drug nanocarrier using doxorubicin hydrochloride (DOX) as a model drug, which results a maximum drug release of ～34.3% (at pH 4.5) for 1 mol% of Cu-HAp. The nanostructured materials were further used to fabricate scaffolds by employing gel-casting method. The finite element modeling theoretical approach was adopted, to correlate the force distribution over the developed scaffold during mechanical characterization. The in vitro study confirmed the nontoxic behavior of the HAp and Cu_x-HAp scaffolds using MG-63 cell line. The developed scaffold effectively facilitates and simulates the new cell attachment, growth, and proliferation on its surface with adequate (～7.87 MPa) compressive strength properties. The enhanced biocompatibility with improved mechanical stability of Cu_x-HAp nanomaterials could address some of the critical challenges in biomedical applications.     

生物陶粒反应器中硝化自养菌与异养菌生长关系的研究

研究了生物陶粒反应器微污染源水时，反应器内异养菌对有机物降解与硝化自养菌对氮氧化作用之间相互关系。得出下列结论：①低有机物浓度（ＣＯＤ〈４０ｍｇ／Ｌ）时，进水有机物浓度变化对硝化自养菌去除氨氮的影响不大；高有机物浓度（ＣＯＤ〉４ｍｇ／Ｌ）时，进水有机物浓度上升对氨氮的去除有抑制作用。②氨氮浓度上升将引起异养菌对有机物去除效率的上升，上升到一定程度后趋于稳定。     

Synthesis and Characterization of Bioceramic Calcium Phosphates by Rapid Combustion Synthesis

Calcium hydroxyapatite(Ca10(PO4)6(OH)2) has been synthesized in short duration by rapid solution combustion by employing different fuels.Calcium nitrate was taken as source of calcium and diammonium hydrogen phosphate served as the source of phosphate ions.Citric acid,tartaric acid,sucrose,glycine and urea were used as the fuels and nitrate ions and nitric acid were used as oxidizers.The influence of fuels on the morphology of the phase formed was studied.Results of the studies by powder X-ray diffraction a...     

Soluble phosphate salts as setting aids for premixed calcium phosphate bone cement pastes

Recently, premixed calcium phosphate cement pastes have been proposed as biomaterials for bone tissue repair and regeneration. Use of premixed pastes saves the time and removes an extra step during a medical operation. α-Tricalcium phosphate (α-TCP) based cements set to form calcium deficient hydroxyapatite which has a moderate bioresorbtion speed. α-TCP cements require a setting aid, usually a sodium or potassium phosphate salt, to speed up the setting process. Within the current research we investigated which setting aid has significant advantage, if α-TCP is used in form of non-aqueous premixed paste. This approach offers the application of simple ingredients to produce a premixed calcium phosphate cement. The following properties of cement formulations were evaluated: cohesion, phase composition, microstructure, pH value of the liquid surrounding the cement, and compressive strength.Compositions using mixture of basic and acidic potassium phosphate salts (KH₂PO₄ and K₂HPO₄) in sufficient amounts give the best overall results (adequate cohesion and pH of the surrounding liquid, hydrolysis of starting materials within 48 h, and compressive strength of 12 ± 3 MPa). Cement prepared with basic sodium phosphate salt (Na₂HPO₄) as setting aid had considerably higher compressive strength 22 ± 1 MPa, but the pH of the surrounding liquid was basic (9.0).     

A review of bioceramic porous scaffolds for hard tissue applications: Effects of structural features

Tissue engineering has acquired remarkable attention as an alternative strategy to treat and restore bone defects during recent years. A scaffold is a fundamental component for tissue engineering, on which cells attach, proliferate and differentiate to form new desirable functional tissue. The composition, and structural features of scaffolds, including porosity and pore size, play a fundamental role in the success of tissue-engineered construct. This review summarizes the effect of porosity and pore size of bioceramic-based scaffolds on their mechanical properties and biological performances. The focus of this review is on scaffolds with porosities 40% and above. From the mechanical point of view, the degree of porosity is a more important factor than pore size and scaffolds with porosities greater than 40% were more likely to substitute trabecular bones. While for in vitro and in vivo performances, pore size appeared more influential feature and co-existence of macropores and micropores led to better bone formation.     

A critical review on the cellular and molecular interactions at the interface of zirconia-based biomaterials

In the past few years, zirconia has gained a great attention among biomedical scientists due to its extraordinary strength and fracture toughness, negligible thermal conductivity, good biocompatibility and chemical inertness. In this regard, there is still room for the manipulation of zirconia-based biomaterials regarding the protein adsorption and subsequently cell responses to the surface. Protein adsorption on biomaterials surfaces start interpreting the construction and also arranging the surface characteristics into a biological language. In this review, the role of adsorbed proteins as key players in starting interactions between cells and zirconia-based biomaterials will be discussed in detail. The discussion will then highlight discussions on the implementation of innovative strategies to engineer the physiochemical properties of this class of biomaterials. It is expected that these promising solutions can better control proteins adsorption and cellular functions after implantation in the body.     

Incorporation of inorganic bioceramics into electrospun scaffolds for tissue engineering applications: A review

Today, the integration of medical and engineering principles for producing biological replacements has attracted much attention. Tissue engineering is an interdisciplinary field introduced for recovery, preservation, and improvement of tissues' function. During the process of reproduction, scaffolds with the support of cells and biological materials and growth factors underlie the effective regeneration of the target tissue. Among the numerous methods, the electrospinning method has the great ability to mimic the extracellular matrix by creating a network of polymer fibers with a high surface area at the nanoscale in order to provide more binding sites for cells. Considering the capabilities and limitations of different polymers, the use of ceramics as a reinforcement phase is a promising approach. Over the past few decades, electrospun scaffolds have been developed by adding different ceramics in terms of their nature, bioinert, bioactive, and biodegradable properties. The main results are related to enhancing the mechanical properties and biological behavior of the polymeric scaffolds after the incorporation of ceramics. Enhanced hydrophilicity, antibacterial and antioxidant properties are other aspects caused by chemical interactions of ceramics and polymers. In this review, the effect of adding inorganic ceramic structures incorporated into polymeric electrospun scaffolds is discussed by highlighting the most recent studies in tissue engineering applications.     

Preparation and morphological investigation on bioactive ion-modified carbonated hydroxyapatite-biopolymer composite ceramics as coatings for orthopaedic implants

Bioactive ions (Mg, Sr, Zn) doped carbonated hydroxyapatite powders (dHAp) and pure carbonated hydroxyapatite (HAp) powders were prepared by wet chemical precipitation method. The bioactive ions were incorporated into the HAp matrix by co-precipitation from solution containing the appropriate amount of chloride salt of different ions. The morphology of pure HAp was mainly needle-like in nanometre size and the particles were disordered showing quasi-amorphous structure. The ion doping changed the morphology of particles, the dHAp particles had distorted spheroid shapes. Owing to the ion addition, the crystallinity of particles decreased. Particle aggregations can also be observed in both types of samples. HAp and dHAp loaded biopolymer polyvinylpyrrolidone (PVP) composite materials have also been developed by novel electrospinning technique. It has been shown that both the HAp and dHAp particles can be successfully incorporated into the PVP fibre web matrix and simultaneously the bioceramic powders were attached to the surface of polymer fibres. The surface of fibres was not fully covered with the particles. The ceramic powder addition to the polymer solution caused the polymer fibres to become more entangled and the diameters of fibres varied over a wider range compared to the base polymer fibres without bioceramic powder addition.     

ZrO2-phosphates porous ceramic obtained via SPS-RS “in situ” technique: Bacteria test assessment

The work presents an original way to obtain porous and mechanically strong (to 560 MPa) ZrO₂ ceramics containing calcium phosphates, HAP (Ca₁₀(PO₄)₆(OH)₂) and TCP (Ca₃(PO₄)₂), using SPS-RS technique. “In situ” formation of calcium phosphate phases (15 and 50 wt%) has been observed in the bulk of ZrO₂ arising from solid-phase interaction of CaO and CaHPO4 mixture at SPS conditions (900–1300 °C). Temperature regime for “in situ” interaction was optimized in accordance with HAP and TCP stability investigations under conditions of oxidative annealing and SPS heating without ZrO₂. Addition of a poreforming agent (carbon template) has been demonstrated to enhance the porosity of the ZrO₂-phosphate ceramics. Effect of the poreformer amount (2, 5, 10 and 15 wt%) on the structural and mechanical properties of ceramics has been studied by the means of mercury porosimetry, low-temperature nitrogen sorption, microscopy, and other analytical techniques. Microbiological tests were performed to assess the efficiency of bacterial film formation on the samples of composite ceramics depending on the calcium phosphate content. Morphology of the biofilms and the relative surface they occupied on the ceramics were investigated using electron microscopy and image processing method based on local binary pattern (LBP) classifier. Suggested SPS-RS method provides porous and mechanically strong ZrO₂-phosphate composite ceramics containing biocompatible components HAP and TCP, which can be prospective for bone-ceramic implants for bone tissue recovery.