Application of silica nanoparticles as fillers in the preparation of nanocomposite of polymers has drawn much attention, due to the increased demand for new materials with improved thermal, ...mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nanocomposites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nanocomposites, generally by sol-gel technique. The effect of nanosilica on the properties of various types of silica-polymer composites is also summarized.
The odontogenic and osteogenic potential of dental pulp stem cells (DPSCs) and stem cells from human exfoliated deciduous tooth (SHED) have been shown clearly by various in vitro and in vivo studies. ...The findings are promising and demonstrated that dental tissue engineering can give a new hope to the individuals suffering from tooth loss and dental diseases. The evaluation of odontogenic and osteogenic differentiation of DPSCs and SHED is commonly carried out by an illustration of the expression of varied related markers. In this review, few commonly used markers such as alkaline phosphatase (ALP), collagen type 1 (Col I), dentin matrix acid phosphoprotein 1 (DMP1), dentin sialophosphoprotein (DSPP), matrix extracellular phosphoglycoprotein (MEPE), osteocalcin (OCN), and osteopontin (OPN). DSPP, DMP1, and MEPE (odontogenic markers), which play an important role during early odontoblastic differentiation and late dentin mineralization, have been highlighted. Osteoblastic proliferation and early/late osteoblastic differentiation can be assessed by estimating the expression of Col I, ALP, OCN and OPN. Despite that, till date, there is no marker which could demonstrate for certain, the differentiation of human DPSCs and SHED towards the odontogenic and osteogenic lineage. This review suggests that SHED are noticeably different from DPSCs and exhibited higher capacity for osteogenic differentiation compared to DPSCs. On the other hand, different expression levels are shown by SHED and DPSCs with regards to the osteoblast markers for osteoblastic differentiation, where, SHED expressed higher levels of ALP, Col I and OCN compared to DPSCs.
Cockle shells are a natural reservoir of calcium carbonate (CaCO3), which is widely used in bone repair, tissue scaffolds, and the development of advanced drug delivery systems. Although many studies ...report on the preparation of CaCO3, the development of a nanosized spherical CaCO3 precursor for calcium oxide (CaO) that is suitable to be incorporated in dental material was scarce. Therefore, this study aimed to synthesize a nanosized spherical CaCO3 precursor for CaO derived from cockle shells using a sol–gel method. Cockle shells were crushed to powder form and mixed with hydrochloric acid, forming calcium chloride (CaCl2). Potassium carbonate (K2CO3) was then fed to the diluted CaCl2 to obtain CaCO3. The effect of experimental parameters on the morphology of CaCO3, such as volume of water, type of solvents, feeding rate of K2CO3, and drying method, were investigated using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry (XRD), Brunauer–Emmett–Teller surface area analysis, and thermogravimetric analysis. Optimized CaCO3 was then calcined to form CaO. XRD analysis of CaCO3 nanoparticles was indicative of the formation of a calcite phase. The well-structured spherical shape of CaCO3 was obtained by the optimum condition of the addition of 50 mL of water into CaCl2 in ethanolic solution with a 1 h feeding rate of K2CO3. Less agglomeration of CaCO3 was obtained using a freeze-drying technique with the surface area of 26 m2/g and average particle size of 39 nm. Spherical shaped nanosized CaO (22–70 nm) was also synthesized. The reproducibility, low cost, and simplicity of the method suggest its potential applications in the large-scale synthesis of the nanoparticles, with spherical morphology in an industrial setting.
Various oxides are used to stabilize zirconium oxide (ZrO2), but their superior hardness causes wear of the machining tool. Calcia-doped zirconia has been studied but reports on properties suitable ...for dental application are lacking. Therefore, this study aimed to fabricate and characterize zirconia stabilized by calcium oxide (CaO) derived from cockle shells and compare it with zirconia stabilized by commercial CaO, sintered at different temperatures. In this study, 176 pressed pellets of zirconia mixed with CaO either derived from cockle shells or commercial CaO were sintered between 1200 and 1500 °C to produce calcia-doped zirconia. Characterizations were made with SEM and XRD. Specimens were subjected to density, compressive and flexural strength, and Vickers hardness testing. Data were analyzed using the independent t-test and one-way ANOVA. XRD revealed the zirconia was stabilized into tetragonal and cubic phases (Ca-SZ). Ca-SZ cockle shells (CS) and Ca-SZ commercial (CC) have average particle sizes of 267 nm and 272 nm, respectively, with similar surface roughness. At 1400 °C sintering temperature, flexural strengths were 1165 and 1152 MPa, compressive strengths were 4914 and 4913 MPa, and Vickers hardness were 977 and 960 MPa for Ca-SZ(CS) and Ca-SZ(CC), respectively. Both Ca-SZ materials showed no significant difference in most properties (p < 0.05) when sintered at different temperatures. The fully sintered Ca-SZ is less hard compared to the ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP) available on the market. Thus, Ca-SZ may be used as an alternative to the current zirconia available on the market for dental application.
A series of iron silica catalyst with (5–20)
wt.% Fe
3+ were prepared by means of a simple solvent extraction and sol–gel technique. These catalysts were probed for the oxidation of phenol employing ...hydrogen peroxide. Catalytic performance increased up to 10
wt.% Fe
3+ loading. Further increase in the iron content was found to reduce the phenol conversion rate. Higher Fe
3+ loading (>10% Fe
3+) resulted in smaller pore size and exhibited extra framework Fe
3+ in the catalyst, which lead to catalytic deficiency in phenol oxidation. Phenol oxidation by RH-10Fe gave 95.2% conversion at 343
K with selective formation of 61.3% catechol (CAT) and 38.7% hydroquinone (HQ). Reusability studies with RH-10Fe resulted in only 16% loss in catalytic activity. However, no leaching of iron was detected. The CAT/HQ ratio was found to be constant during the reaction which suggested a non-free radical catalytic mechanism to be operative.
Nanotechnology is gaining momentum due to its ability to transform metals into nanoparticles. The synthesis, characterization, and applications of biologically synthesized nanomaterials have become ...an important branch of nanotechnology. Plant extracts are a cost-effective, ecologically friendly, and efficient alternative for the large-scale synthesis of nanoparticles. In this study, silver nanoparticles (AgNps) were synthesized using Rhinacanthus nasutus leaf extract. After exposing the silver ions to the leaf extract, the rapid reduction of silver ions led to the formation of AgNps in solution. The synthesis was confirmed by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. The in vitro antimicrobial activity of the AgNps synthesized using R. nasutus leaf extract was investigated against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia, Escherichia coli, Aspergillus niger, and Aspergillus flavus using a disc diffusion method. The AgNps showed potential activity against all of the bacterial strains and fungal colonies, indicating that R. nasutus has the potential to be used in the development of value-added products in the biomedical and nanotechnology-based industries.
Glass Ionomer Cements (GIC) are among the most popular restorative materials, but their use in dentistry is limited due to their physical properties. The hardness of GIC was improved by incorporation ...of nano-hydroxyapatite-silica into GIC, to expand its applicability.
To evaluate the cytotoxic effects of nano-hydroxyapatite-silica incorporated glass ionomer cement (HA-SiO
-GIC) on human Dental Pulp Stem Cells (DPSC) and compare it with conventional GIC and resin modified GIC.
Material extracts of Fuji IX, Fuji II LC and HA-SiO
-GIC were prepared into seven serial concentrations and applied to 96-well-plates seeded with DPSC. The 96-well-plates were incubated for 24 and 72 hours. The morphology of DPSC was observed under the inverted phase contrast microscope, and the cell viability was determined using MTT assay at both time intervals. Kruskal-Wallis test was performed for statistical analysis.
At maximum concentration, DPSC appeared fewer in number, but the normal spindle morphology was maintained in all groups except for Fuji II LC. At lower concentrations, DPSC appeared normal and more confluent in all groups. The cytotoxic effects of all groups were dose dependent. Fuji IX demonstrated the lowest cytotoxicity, followed by HA-SiO
-GIC. Fuji II LC demonstrated the highest cytotoxicity. The difference was significant between all groups at 200 mg/ml concentration (p<0.05). At concentration <100 mg/ml, cytotoxicity of HA-SiO
-GIC was comparable to that of Fuji IX and lower than that of Fuji II LC.
HA-SiO
-GIC showed a favourable cytotoxicity response and thus holds promise as a future potential restorative material in clinical dentistry.
Highly active copper supported rice husk silica catalyst gave an excellent activity in the conversion of toxic pollutant, phenol into benign products (CAT and HQ).
•Eco-friendly copper catalysts were ...synthesized from rice husk silica as support.•Showed superior performance in the oxidation of phenol by H2O2 in water medium.•Introduction of copper into silica matrix accelerates the catalytic activity.•RH-10Cu was the best catalyst for phenol conversion into catechol and hydroquinone.•FT-IR showed catalyst deactivation during the third regeneration activity.
A series of highly mesoporous copper catalysts (5–20wt.%) supported on silica rice husk were synthesized via sol–gel route at room temperature. The FT-IR and 29Si MAS NMR spectroscopic studies revealed the successful substitution of copper into the silica matrix. Copper in the +2 oxidation state was evidenced from the DR/UV–vis and XPS analyses. Introduction of copper up to 10wt.% (RH-10Cu) results in a progressive enhancement in the BET surface area. The activity of the copper catalysts was studied in the liquid-phase oxidation of phenol with H2O2 yielding catechol (CAT) and hydroquinone (HQ). Phenol conversion was influenced by various experimental conditions such as temperature, catalyst dosage, molar ratio of reactants, nature of solvent and percentage metal loading. Excellent activity was achieved when 10wt.% copper was used and decreased with further increase in the copper loading. RH-10Cu could be regenerated several times without significant loss in the catalytic activity.
•Heterogeneous cobalt catalysts were synthesized from agricultural biomass.•Cobalt catalysts were highly dispersed and exhibited good textural properties.•The catalysts were active in the oxidation ...of phenol at ambient condition.•The catalysis of cobalt catalysts was truly driven by its heterogeneous nature.•RH-10Co was stable even after five consecutive catalytic runs.
Highly mesoporous cobalt silica rice husk catalysts with (5–15wt.%) Co2+ loading were prepared via a simple sol–gel technique at room temperature. The successful insertion of cobalt ions into silica matrix was evidenced from FT-IR, NMR, XPS and AAS analyses. Preservation of the mesoporosity nature of silica upon incorporating Co2+ was confirmed from the N2-sorption studies. The topography and morphology viewed by TEM analysis differs as the cobalt concentration varies from 5 to 15wt.%. Parallel pore channels and spherical nanoparticles of 9.44nm were achieved for cobalt silica catalysts with 10 and 15wt.% respectively. Cobalt catalysts were active in the liquid-phase oxidation of phenol with H2O2 as an oxygen source. The performances of the catalysts were greatly influenced by various parameters such as reaction temperature, catalyst amount, molar ratio of substrate to oxidant, nature of solvent, metal loading and homogeneous precursor salt. Water served as the best reaction medium for this oxidation system. The regeneration studies confirmed cobalt catalyst could be reused for five cycles without experiencing large loss in the conversion. Both leaching and reusability studies testified that the catalysts were truly heterogeneous.
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