Optimization of Metal Ion/Fuel Ratio for an Effective Combustion of Monticellite and Investigation of Its Microbial and Hemolytic Activity for Biomedical Applications.

Bioactive silicates have gained popularity as bone graft substitutes in recent years due to their exceptional ability to bind to host tissues. The current study investigates the effect of changing the metal ion-to-fuel ratio on the properties and biological activity of monticellite prepared via the sol-gel connived combustion technique. Single-phasic monticellite was obtained at 900 °C, without any secondary-phase contaminants for the fuel-lean, stoichiometric, and fuel-rich conditions. SEM and TEM micrographs revealed the porous, spongy morphology of the materials. Because of the reduced crystallite size and higher surface area, the biomineralization of monticellite prepared under fuel-lean conditions resulted in more apatite deposition than those of the other two samples. The results show that the material has a good compressive strength comparable to natural bone, while its brittleness is equivalent to the lower moduli of bone. In terms of antibacterial and antifungal activities, the monticellite bioceramics outperformed the clinical pathogens. It can be used for bone tissue engineering and other biological applications due to its excellent anti-inflammatory and hemolysis inhibitory properties.

Synthesis and characterization of calcium and magnesium based oxides and titanates for photocatalytic degradation of rhodamine B: a comparative study.

The current investigation deals with the simple and ecological synthesis of CaO, MgO, CaTiO3, and MgTiO3 for the photocatalytic dilapidation of rhodamine B dye. CaO was procured from chicken eggshell waste by calcination process, while MgO was produced by solution combustion method using urea as a fuel source. Furthermore, CaTiO3 and MgTiO3 were synthesized through an easy and simple solid-state method by mixing thoroughly the synthesized CaO or MgO with TiO2 before calcination at 900 °C. XRD and EDX investigations confirmed the phase formation of the materials. Moreover, FTIR spectra revealed the existence of Ca-Ti-O, Mg-Ti-O, and Ti-O which resembles the chemical composition of the proposed materials. SEM micrographs revealed that the surface of CaTiO3 is rougher with relatively dispersed particles compared to MgTiO3, reflecting a higher surface area of CaTiO3. Diffuse reflectance spectroscopy investigations indicated that the synthesized materials can act as photocatalysts under UV illumination. Accordingly, CaO and CaTiO3 effectively degraded rhodamine B dye within 120 min with a photodegradation activity of 63% and 72%, respectively. In contrast, the photocatalytic degradation activity of MgO and MgTiO3 was much lower, since only 21.39 and 29.44% of the dye were degraded, respectively after 120 min of irradiation. Furtheremore, the photocatalytic activity of the mixture from both Ca and Mg titanates was 64.63%. These findings might be valuable for designing potential and affordable photocatalysts for wastewater purification.

Biomineralization, dissolution and cellular studies of silicate bioceramics prepared from eggshell and rice husk.

The current investigation aims to replace the synthetic starting materials with biowaste to synthesize and explore three different silicate bioceramics. Pure silica from rice husk was extracted by decomposition of rice husk in muffle furnace followed by alkali treatment and acid precipitation. Raw eggshell and extracted silica were utilized for the preparation of wollastonite, diopside and forsterite by the solid-state method. The TG-DSC analysis shows that the crystallization temperature of wollastonite, diopside and forsterite was found to be 883 °C, 870 °C and 980 °C, respectively. The phase purity of wollastonite was attained at 1100 °C whereas diopside and forsterite were composed of secondary phases even after calcination at 1250 °C and 1300 °C respectively. All three materials behaved differently when exposed to the physiological environment, as wollastonite exhibited remarkable apatite deposition within 3 days whereas a distinct apatite phase was noticed on the surface of diopside after 2 weeks and forsterite shows the formation of apatite phase after five weeks of immersion. The rapid dissolution of Mg2+ ion from forsterite lowered the leaching of silicate ions into the simulated body fluid leading to poor apatite deposition over its surface. Chemical composition was found to plays a key role in the biomineralization ability of these bioceramics. Hemolysis and Lactate Dehydrogenase (LDH) release assays were performed to evaluate the hemocompatibility of silicate ceramics cultured at different concentrations (62.5, 125, and 250 µg/mL) with red blood cells and mononuclear leucocytes (MLs) of mice. The hemolytic activity of all the tested bioceramics was insignificant (less than 1%). The interaction between diopside and mouse multipotent mesenchymal stromal cells (MMSCs) caused a negligible increase in the number of apoptosis-associated Annexin V-binding cells whereas forsterite and wollastonite induced an increase in the number of the apoptotic cells only at the concentration of 250 µg/mL. The LDH assay did not show statistically significant changes in the proliferation of MMSCs after treatment with the bioceramics at the tested concentrations when compared to control (p > 0.05). This finding showed that the death of a part of cells during the first 24 h of incubation did not prevent the proliferation of MMSCs incubated with diopside, forsterite and wollastonite for 72 h.

Biomineralization, mechanical, antibacterial and biological investigation of larnite and rankinite bioceramics.

This work is aimed to develop a biocompatible, bactericidal and mechanically stable biomaterial to overcome the challenges associated with calcium phosphate bioceramics. The influence of chemical composition on synthesis temperature, bioactivity, antibacterial activity and mechanical stability of least explored calcium silicate bioceramics was studied. The current study also investigates the biomedical applications of rankinite (Ca3Si2O7) for the first time. Sol-gel combustion method was employed for their preparation using citric acid as a fuel. Differential thermal analysis indicated that the crystallization of larnite and rankinite occurred at 795 °C and 1000 °C respectively. The transformation of secondary phases into the desired product was confirmed by XRD and FT-IR. TEM micrographs showed the particle size of larnite in the range of 100-200 nm. The surface of the samples was entirely covered by the dominant apatite phase within one week of immersion. Moreover, the compressive strength of larnite and rankinite was found to be 143 MPa and 233 MPa even after 28 days of soaking in SBF. Both samples prevented the growth of clinical pathogens at a concentration of 2 mg/mL. Larnite and rankinite supported the adhesion, proliferation and osteogenic differentiation of hBMSCs. The variation in chemical composition was found to influence the properties of larnite and rankinite. The results observed in this work signify that these materials not only exhibit faster biomineralization ability, excellent cytocompatibility but also enhanced mechanical stability and antibacterial properties.

Review on calcium- and magnesium-based silicates for bone tissue engineering applications.

Bone is a self-engineered structural component of the human body with multifaceted mechanical strength, which provides indomitable support to the effective functioning of the human body. It is indispensable to find a suitable biomaterial for substituting the bone as the bone substitute material requirement is very high due to the rate of bone fracture and infection lead to osteoporosis in human beings increases rapidly. It is not an easy task to design a material with good apatite deposition ability, a faster rate of dissolution, superior resorbability, high mechanical strength, and significant bactericidal activity. Since the synthetic hydroxyapatite was not able to achieve the dahlite phase of hydroxyapatite (natural bone mineral phase), silicates emerged as an alternate biomaterial to meet the need for bone graft substitutes. All silicates do not exhibit the properties required for bone graft substitutes, as their composition and methodology adopted for the synthesis are different. Calcium, magnesium, and silicon play a major role in the formation of bone mineral and their metabolism during bone formation. In this review, the relationship between composition and activity of calcium, magnesium-based silicates have been discussed along with the future scope of these materials for hard tissue engineering applications.

Antibacterial forsterite (Mg2SiO4) scaffold: A promising bioceramic for load bearing applications.

In the current work, forsterite samples with different surface area were investigated for its antibacterial activity. Dissolution studies show that the lower degradation of forsterite compared to other silicate bioceramics, which is a desirable property for repairing bone defects. Forsterite scaffold shows superior compressive strength than the cortical bone after immersion in simulated body fluid. Bactericidal tests indicate that the forsterite had inhibition effect on the growth of clinical bacterial isolates. Forsterite may be a suitable candidate material for load bearing applications with enhanced mechanical properties and lower degradation rate.