Regression Analysis of the Dielectric and Morphological Properties for Porous Nanohydroxyapatite/Starch Composites: A Correlative Study.

This paper aims to investigate the dielectric properties, i.e., dielectric constant (ε'), dielectric loss factor (ε″), dielectric tangent loss (tan δ), electrical conductivity (σ), and penetration depth (Dp), of the porous nanohydroxyapatite/starch composites in the function of starch proportion, pore size, and porosity over a broad band frequency range of 5 MHz−12 GHz. The porous nanohydroxyapatite/starch composites were fabricated using different starch proportions ranging from 30 to 90 wt%. The results reveal that the dielectric properties and the microstructural features of the porous nanohydroxyapatite/starch composites can be enhanced by the increment in the starch proportion. Nevertheless, the composite with 80 wt% of starch proportion exhibit low dielectric properties (ε', ε″, tan δ, and σ) and a high penetration depth because of its highly interconnected porous microstructures. The dielectric properties of the porous nanohydroxyapatite/starch composites are highly dependent on starch proportion, average pore size, and porosity. The regression models are developed to express the dielectric properties of the porous nanohydroxyapatite/starch composites (R2 > 0.96) in the function of starch proportion, pore size, and porosity from 1 to 11 GHz. This dielectric study can facilitate the assessment of bone scaffold design in bone tissue engineering applications.

In vitro/In vivo Evaluations of Hydroxyapatite Nanoparticles with Different Geometry.

Purpose: Hydroxyapatite-based nanoparticles have found diverse applications in drug delivery, gene carriers, diagnostics, bioimaging and tissue engineering, owing to their ability to easily enter the bloodstream and target specific sites. However, there is limited understanding of the potential adverse effects and molecular mechanisms of these nanoparticles with varying geometries upon their entry into the bloodstream. Here, we used two commercially available hydroxyapatite nanoparticles (HANPs) with different geometries (less than 100 nm in size each) to investigate this issue. Methods: First, the particle size, Zeta potential, and surface morphology of nano-hydroxyapatite were characterized. Subsequently, the effects of 2~2000 µM nano-hydroxyapatite on the proliferation, migration, cell cycle distribution, and apoptosis levels of umbilical vein endothelial cells were evaluated. Additionally, the impact of nanoparticles of various shapes on the differential expression of genes was investigated using transcriptome sequencing. Additionally, we investigated the in vivo biocompatibility of HANPs through gavage administration of nanohydroxyapatite in mice. Results: Our results demonstrate that while rod-shaped HANPs promote proliferation in Human Umbilical Vein Endothelial Cell (HUVEC) monolayers at 200 µM, sphere-shaped HANPs exhibit significant toxicity to these monolayers at the same concentration, inducing apoptosis/necrosis and S-phase cell cycle arrest through inflammation. Additionally, sphere-shaped HANPs enhance SULT1A3 levels relative to rod-shaped HANPs, facilitating chemical carcinogenesis-DNA adduct signaling pathways in HUVEC monolayers. In vivo experiments have shown that while HANPs can influence the number of blood cells and comprehensive metabolic indicators in blood, they do not exhibit significant toxicity. Conclusion: In conclusion, this study has demonstrated that the geometry and surface area of HANPs significantly affect VEC survival status and proliferation. These findings hold significant implications for the optimization of biomaterials in cell engineering applications.

Green Synthesis, Characterization, and Evaluation of the Antimicrobial Properties and Compressive Strength of Hydroxyapatite Nanoparticle-Incorporated Glass Ionomer Cement.

Background Glass ionomer cement (GIC) plays a vital role in dental restorative procedures, serving purposes such as filling, luting, and adhesion. However, its inadequate mechanical properties pose challenges, especially in areas experiencing significant stress. To overcome this limitation, nanohydroxyapatite (nHA), known for its bioactive phosphate content, is added to the GIC at specific concentrations to improve its properties. Aim  We aim to evaluate the antimicrobial property and compressive strength of green-mediated nHA-incorporated GIC. Material and methods Green synthesis of hydroxyapatite nanoparticles was prepared using Moringa oleifera extract in a solvent form and eggshell waste served as the calcium source. These nHA powders were then integrated into the GIC at varying concentrations (3%, 5%, and 10%) designated as Group I, Group II, and Group III, respectively, while Group IV (control) consisted of conventional GIC. Specimens were fabricated and subjected to chemical structure analysis through Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). The antimicrobial activity and compressive strength of all groups were investigated. The antimicrobial activity against Streptococcus mutans and Lactobacillus was evaluated through the minimum inhibitory concentration (MIC) test, while compressive strength was evaluated by measuring the maximum force endured by the specimen before fracturing. Data analysis utilized IBM SPSS Statistics software, employing repeated measures ANOVA to determine mean MIC values and compressive strength, with Tukey's posthoc test for pairwise comparisons. Results The results of the study showed that the antimicrobial efficacy of nHA GIC improved with increasing weight percent (% wt) of the additive, exhibiting significantly enhanced activity against Streptococcus mutans and Lactobacillus compared to the control group (Group IV) with statistical significance (p < 0.05). Moreover, the compressive strength exhibited notable enhancements in the modified groups, including Group I (172.55 ± 0.76), Group II (178.16 ± 0.760), and Group III (182.45 ± 0.950), when compared to the control (162.46 ± 1.606), with statistically significant differences (p < 0.05). Conclusion The study demonstrates that the incorporation of green-mediated nHA-containing GIC results in superior antimicrobial efficacy and compressive strength compared to the control group (Group IV). In particular, the highest concentration of nHA-modified GIC (10%) exhibited the most favorable antimicrobial properties along with increased strength. Therefore, utilizing green-mediated nHA in the GIC shows promise as an effective restorative material. Future investigations should delve into the molecular chemistry and bonding mechanisms to further explore its potential.

Hydroxyapatite Nanoparticles Promote the Development of Bone Microtissues for Accelerated Bone Regeneration by Activating the FAK/Akt Pathway.

Scaffold-free bone microtissues differentiated from mesenchymal stem cell (MSC) spheroids offer great potential for bottom-up bone tissue engineering as a direct supply of cells and osteogenic signals. Many biomaterials or biomolecules have been incorporated into bone microtissues to enhance their osteogenic abilities, but these materials are far from clinical approval. Here, we aimed to incorporate hydroxyapatite (HAP) nanoparticles, an essential component of bone matrix, into MSC spheroids to instruct their osteogenic differentiation into bone microtissues and further self-organization into bone organoids with a trabecular structure. Furthermore, the biological interaction between HAP nanoparticles and MSCs and the potential molecular mechanisms in the bone development of MSC spheroids were investigated by both in vitro and in vivo studies. As a result, improved cell viability and osteogenic abilities were observed for the MSC spheroids incorporated with HAP nanoparticles at a concentration of 30 µg/mL. HAP nanoparticles could promote the sequential expression of osteogenic markers (Runx2, Osterix, Sclerostin), promote the expression of bone matrix proteins (OPN, OCN, and Collagen I), promote the mineralization of the bone matrix, and thus promote the bone development of MSC spheroids. The differentiated bone microtissues could further self-organize into linear, lamellar, and spatial bone organoids with trabecular structures. More importantly, adding FAK or Akt inhibitors could decrease the level of HAP-induced osteogenic differentiation of bone microtissues. Finally, excellent new bone regeneration was achieved after injecting bone microtissues into cranial bone defect models, which could also be eliminated by the Akt inhibitor. In conclusion, HAP nanoparticles could promote the development of bone microtissues by promoting the osteogenic differentiation of MSCs and the formation and mineralization of the bone matrix via the FAK/Akt pathway. The bone microtissues could act as individual ossification centers and self-organize into macroscale bone organoids, and in this meaning, the bone microtissues could be called microscale bone organoids. Furthermore, the bone microtissues revealed excellent clinical perspectives for injectable cellular therapies for bone defects.

Green synthesis of nanohydroxyapatite trough Elaeagnus angustifolia L. extract and evaluating its anti-tumor properties in MCF7 breast cancer cell line.

BACKGROUND: One of the most common types of cancer in women is breast cancer. There are numerous natural plant-based products, which exert anti-tumoral effects including Elaeagnus Angustifolia (EA). It modulates cell-cycle process, heat-shock proteins expression, anti-proliferative properties, apoptosis induction, blocking of angiogenesis, and cell invasion inhibition. The current study aimed to synthesize and evaluate the anticancer effects of hydroalcoholic EA extract (HEAE), Nanohydroxyapatite (nHAp) and nHAp synthesized trough EA (nHA-EA) in MCF-7 breast cancer cell line. METHODS: In the present study, HEAE preparation and green synthesis of nHA-EA was done and phase composition, functional groups, and crystallin phase of nHA-EA and nHAp were determined using Fourier-transform infrared (FTIR) and X-ray diffraction (XRD). The characteristics of synthesized nanoparticles including structural and morphological parameters were investigated using scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) techniques. Then, by using MTT-assay (Dimethylthiazoldiphenyltetrazolium), the in vitro cytotoxic and half maximal inhibitory concentration (IC50) of EA extract, nHAp, and nHA-EA in the MCF-7 breast cancer cell line was evaluated. Next, we assessed the expression of apoptosis-related genes Bax, Bcl2 and p53 using quantitative reverse-transcriptase polymerase-chain-reaction (qRT-PCR) and migration of MCF-7 cells by scratch assay. RESULTS: The FTIR results demonstrated formation of nHAp and its interaction with HEAE during synthesis process. The XRD results of the synthesized nanoparticles showed similar XRD pattern of nHA-EA and nHAp and purity of synthesized nanomaterials. The average IC50 of HEAE, nHAp, and nHA-EA extract after treatment of cancer cells for 24 h was 400 µg/mL, 200 µg/mL, and 100 µg/mL, respectively. Our results revealed that nHA-EA significantly reduced the migration and invasion of the MCF-7 cells, in comparison to the nHAp and EA extract. Moreover, level of Bax/Bcl2 and p53 was significantly higher in the nHA-EA extract group in comparison to the EA extract and nHAp group. CONCLUSION: Taken together, our results demonstrated that bioactive constituents of EA medicinal plant in form of nHA-EA particles, can effectively exerts potential anticancer and chemo preventive effect against breast cancer growth and can be proposed as a promising beneficial candidate for BC therapy. However, further investigations are required to discover what bioactive compounds are responsible for the chemo preventive effect of this extract.

Multifunctional electrospun nanofibrous scaffold enriched with alendronate and hydroxyapatite for balancing osteogenic and osteoclast activity to promote bone regeneration.

Electrospun composite nanofiber scaffolds are well known for their bone and tissue regeneration applications. This research is focused on the development of PVP and PVA nanofiber composite scaffolds enriched with hydroxyapatite (HA) nanoparticles and alendronate (ALN) using the electrospinning technique. The developed nanofiber scaffolds were investigated for their physicochemical as well as bone regeneration potential. The results obtained from particle size, zeta potential, SEM and EDX analysis of HA nanoparticles confirmed their successful fabrication. Further, SEM analysis verified nanofiber's diameters within 200-250 nm, while EDX analysis confirmed the successful incorporation of HA and ALN into the scaffolds. XRD and TGA analysis revealed the amorphous and thermally stable nature of the nanofiber composite scaffolds. Contact angle, FTIR analysis, Swelling and biodegradability studies revealed the hydrophilicity, chemical compatibility, suitable water uptake capacity and increased in-vitro degradation making it appropriate for tissue regeneration. The addition of HA into nanofiber scaffolds enhanced the physiochemical properties. Additionally, hemolysis cell viability, cell adhesion and proliferation by SEM as well as confocal microscopy and live/dead assay results demonstrated the non-toxic and biocompatibility behavior of nanofiber scaffolds. Alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) assays demonstrated osteoblast promotion and osteoclast inhibition, respectively. These findings suggest that developed HA and ALN-loaded PVP/PVA-ALN-HA nanofiber composite scaffolds hold significant promise for bone regeneration applications.

Enhanced wound-healing efficacy of electrospun mesoporous hydroxyapatite nanoparticle-loaded chitosan nanofiber developed using pluronic F127.

One of the goals of wound repairing is to mimic the function and architecture of the native extracellular matrix (ECM). To this end, for the first time, we used pluronic F127 and mesoporous rod-like hydroxyapatite nanoparticles (mr-HAP NPs) simultaneously to prepare a novel low-diameter electrospun ECM-mimicking wound dressing based on a mixture of chitosan and polyethylene oxide. F127 is used as a surface tension regulator of the polymer solution. In addition, F127 has the special ability to reduce the size of nanofibers. mr-HAP NPs are used as cell proliferation accelerators which also improve the mechanical properties and water uptake capacity of the as-prepared dressing. The average size of nanofibers in the presence of F127 was about 110 nm which was more than 2.5 times lower than nanofibers prepared without F127. The water uptake capacity was evaluated to investigate the wound exudate absorption capacity of the wound dressing. It was observed that the incorporation of mr-HAP NPs into wound dressing structure increases the water uptake capacity by more than 2.5 times. Alongside the evaluation of cytocompatibility through in vitro cell viability assay, the wound healing efficacy was also determined in full-thickness skin wounds in a rat model for 15 days. The cytocompatible wound dressing showed significantly higher wound closure efficacy than the control group so the wounds healed entirely on the last day of the treatment period. As well, the pathology analysis proved better granulation tissue development and greater re-epithelialization. These findings are by virtue of the improved mechanical properties, accelerated cell migration and proliferation, proper environment for oxygen exchange, and enhanced exudate uptake of the wound dressing. These all are due to the presence of F127 and mr-HAP.

Evaluation the properties of orthodontic adhesive incorporated with nano-hydroxyapatite particles.

OBJECTIVE: This research was designed to study the effects of calcium hydroxyapatite nanoparticle incorporation on polymerization as well as the shear bond strength for Heliosit adhesive. MATERIALS AND METHODS: Calcium hydroxyapatite nanoparticles were prepared from natural products using the sol-gel method, and were inspected using a transmission electron microscope. The nanoparticles were added to the conventional orthodontic adhesive at 2% wt and 4% wt concentrations. The degree of conversion for each test group was measured using a Fourier transform infrared spectroscopy device. Each adhesive group was used for bonding metal brackets to the premolar buccal enamel surface. The shear bond strength of all samples was measured. RESULTS: A significant difference was found among all the study groups (p ≤ 0.05) in terms of the degree of conversion and shear bond strength. The 2% wt nanoparticle group showed the highest values for both variables. The lowest value was recorded within the 4% wt nanoparticle group in comparison to the control group. CONCLUSIONS: Calcium hydroxyapatite nanoparticle incorporation with a conventional Heliosit adhesive resin to a limited concentration has improved the mechanical properties of orthodontic adhesive.

Preparation and biodegradable properties of hydroxyapatite nanoparticle composite coated with poly lactic-co-glycolic acid/polyvinyl alcohol for bone regeneration.

BACKGROUND: Bone loss rapidly increases 6 months post tooth extraction, which causes the atrophy of the alveolar bone. Two kinds of biomaterials which can stimulate bone regeneration are bioceramics and polymers. Making a composite of biomaterials results in better physical and biomolecular characteristics in comparison with a bioceramic or a polymer alone. Hydroxyapatite nanoparticles (HANPs) are one of the bioceramics commonly used for bone regeneration; they can degrade faster than hydroxyapatite (HA) microparticles, but have an insufficient pore size. Polyvinyl alcohol (PVA) and poly lactic-co-glycolic acid (PLGA) are polymers which have been used for biomedical applications. However, PLGA alone has insufficient cell attachment and PVA alone slowly degrades in the bone tissue. OBJECTIVES: The aim of the present study was to analyze the biodegradation properties of the HANP/PLGA/PVA composites and investigate the pore size. MATERIAL AND METHODS: The HANP/PLGA/PVA composites were prepared using the freeze-drying method, with 20% (w/w) of HANP and 20% (w/w) of PLGA. Morphology and the pore size were determined by means of the field emission scanning electron microscopy (FE-SEM) analysis. Biodegradation properties were determined by calculating water uptake and water loss for 1, 3 and 6 weeks. Statistical analysis was performed based on the one-way analysis of variance (ANOVA) at p < 0.05. RESULTS: The HANP/PLGA/PVA composites had the greatest mean pore size and a rougher surface than others (176.00 ±61.93 µm; p < 0.05). Moreover, the HANP/PLGA/PVA composites had the greatest water uptake, significantly in the 3rd (730.46%; p < 0.05) and 6th weeks (731.07%; p < 0.05), and water loss in the 6th week (67.69%; p < 0.05). CONCLUSIONS: The HANP/PLGA/PVA composites have optimal pore size, morphology and degradability, which shows their high potential as an effective bone scaffold to repair the alveolar defect post tooth extraction.

Vanadium: Risks and possible benefits in the light of a comprehensive overview of its pharmacotoxicological mechanisms and multi-applications with a summary of further research trends.

BACKGROUND: Vanadium (V) is an element with a wide range of effects on the mammalian organism. The ability of this metal to form organometallic compounds has contributed to the increase in the number of studies on the multidirectional biological activity of its various organic complexes in view of their application in medicine. OBJECTIVE: This review aims at summarizing the current state of knowledge of the pharmacological potential of V and the mechanisms underlying its anti-viral, anti-bacterial, anti-parasitic, anti-fungal, anti-cancer, anti-diabetic, anti-hypercholesterolemic, cardioprotective, and neuroprotective activity as well as the mechanisms of appetite regulation related to the possibility of using this element in the treatment of obesity. The toxicological potential of V and the mechanisms of its toxic action, which have not been sufficiently recognized yet, as well as key information about the essentiality of this metal, its physiological role, and metabolism with certain aspects on the timeline is collected as well. The report also aims to review the use of V in the implantology and industrial sectors emphasizing the human health hazard as well as collect data on the directions of further research on V and its interactions with Mg along with their character. RESULTS AND CONCLUSIONS: Multidirectional studies on V have shown that further analyses are still required for this element to be used as a metallodrug in the fight against certain life-threatening diseases. Studies on interactions of V with Mg, which showed that both elements are able to modulate the response in an interactive manner are needed as well, as the results of such investigations may help not only in recognizing new markers of V toxicity and clarify the underlying interactive mechanism between them, thus improving the medical application of the metals against modern-age diseases, but also they may help in development of principles of effective protection of humans against environmental/occupational V exposure.

In Situ In Vivo radiolabeling of polymer-coated hydroxyapatite nanoparticles to track their biodistribution in mice.

The imaging of healthy tissues and solid tumors benefits from the application of nanoparticle probes with altered pharmacokinetics, not available to low molecular weight compounds. However, the distribution and accumulation of nanoprobes in vivo typically take at least tens of hours to be efficient. For nanoprobes bearing a radioactive label, this is contradictory to the requirement of minimizing the radiation dose for patients by using as-short-as-feasible half-life radionuclides in diagnostics. Thus, we developed a two-stage diagnostic concept for monitoring long-lasting targeting effects with short-lived radioactive labels using bone-mimicking biocompatible polymer-coated and colloidally fully stabilized hydroxyapatite nanoparticles (HAP NPs) and bone-seeking radiopharmaceuticals. Within the pretargeting stage, the nonlabeled nanoparticles are allowed to circulate in the blood. Afterward, 99mTc-1-hydroxyethylidene-1.1-diphosphonate (99mTc-HEDP) is administered intravenously for in situ labeling of the nanoparticles and subsequent single-photon emission computed tomography/computed tomography (SPECT/CT) visualization. The HAP NPs, stabilized with tailored hydrophilic polymers, are not cytotoxic in vitro, as shown by several cell lines. The polymer coating prolongs the circulation of HAP NPs in the blood. The nanoparticles were successfully labeled in vivo with 99mTc-HEDP, 1 and 24 h after injection, and they were visualized by SPECT/CT over time in healthy mice.

Generation of a Hydroxyapatite Nanocarrier through Biomineralization Using Cell-Free Extract of Lactic Acid Bacteria for Antibiofilm Application.

Nanoscale materials hold considerable promise in the mitigation of bacterial infections. In order to exploit nanomaterials as delivery systems in an antibacterial therapeutic paradigm, it is critical to ensure that the generated material is nontoxic. Based on the fundamental principle of biomineralization, we herein report the generation of biocompatible hydroxyapatite nanoparticles (HANPs) in the presence of proteins secreted by the lactic acid bacteria (LAB) Lactobacillus plantarum MTCC 1325, Lactobacillus plantarum CRA52, and Pediococcus pentosaceus CRA51. The biogenic HANPs were characterized by AFM, FETEM, powder XRD, DLS, and FTIR analysis. Interestingly, HANPs could also be synthesized using an ∼20 kDa protein purified from the secreted protein extract obtained from L. plantarum MTCC 1325, which suggested that this lower molecular weight protein fraction was perhaps significantly involved in biomineralization-based generation of HANPs. In order to develop a therapeutic bactericidal nanocomposite, HANPs were loaded with the antibiotic polymyxin B (PB). A Langmuir isotherm model was evident in the studies that measured adsorption of PB onto HANPs. A sustained release profile of PB from the nanocomposite was observed in buffers having varying pH and in simulated body fluid. The nanocomposite (PB-HNC) exhibited bactericidal as well as antibiofilm activity against Pseudomonas aeruginosa MTCC 2488 and was nontoxic to cultured human embryonic kidney cells.

Evaluation of a New Hydroxyapatite Nanoparticle as a Drug Delivery System to Oral Squamous Cell Carcinoma Cells.

BACKGROUND/AIM: Due to its abilities of substance adsorption and intracellular transportation, hydroxyapatite is a potential carrier in drug delivery systems (DDS). This in vitro study investigated whether newly-developed, highly-dispersive calcined hydroxyapatite nanoparticles with an average grain diameter of 20 nm (nano-SHAP) were suitable as a DDS for the drugs zoledronic acid (ZA), cisplatin, and carboplatin. MATERIAL AND METHODS: The effects of drug-bearing nano-SHAP on cell proliferation were assessed using three human oral squamous cell carcinoma cell lines (HSC-4, KOSC, and SAS) and one human breast cancer cell line (MCF-7). RESULTS: Nano-SHAP alone did not affect proliferation of any cell line until a concentration of 1 µg/ml was reached. Although the effective concentration of ZA in ZA-bearing nano-SHAP differed, it inhibited cell proliferation better than ZA alone. Cisplatin and carboplatin-bearing nano-SHAP had the same effect as these drugs alone. CONCLUSION: The nano-SHAP system is of potential use as a drug delivery system.

Effect of Citric Acid Surface Modification on Solubility of Hydroxyapatite Nanoparticles.

Worldwide, there is an amplified interest in nanotechnology-based approaches to develop efficient nitrogen, phosphorus, and potassium fertilizers to address major challenges pertaining to food security. However, there are significant challenges associated with fertilizer manufacture and supply as well as cost in both economic and environmental terms. The main issues relating to nitrogen fertilizer surround the use of fossil fuels in its production and the emission of greenhouse gases resulting from its use in agriculture; phosphorus being a mineral source makes it nonrenewable and casts a shadow on its sustainable use in agriculture. This study focuses on development of an efficient P nutrient system that could overcome the inherent problems arising from current P fertilizers. Attempts are made to synthesize citric acid surface-modified hydroxyapatite nanoparticles using wet chemical precipitation. The resulting nanohybrids were characterized using powder X-ray diffraction to extract the crystallographic data, while functional group analysis was done by Fourier transform infrared spectroscopy. Morphology and particle size were studied using scanning electron microscopy along with elemental analysis using energy-dispersive X-ray diffraction spectroscopy. Its effectiveness as a source of P was investigated using water release studies and bioavailability studies using Zea mays as the model crop. Both tests demonstrated the increased availability of P from nanohybrids in the presence of an organic acid compared with pure hydroxyapatite nanoparticles and rock phosphate.

Raman scattering studies on PEG functionalized hydroxyapatite nanoparticles.

The pure hydroxyapatite (HAP) nanoparticles (NPs) have been synthesized by wet chemical precipitation method. Raman spectral measurements have been made for pure HAP, pure Polyethylene glycol (PEG) 6000 and PEG coated HAP in different mass ratios (sample 1, sample 2 and sample 3). The peaks observed in Raman spectrum of pure HAP and the XRD pattern have confirmed the formation of HAP NPs. Vibrational modes have been assigned for pure HAP and pure PEG 6000. The observed variation in peak position of Raman active vibrational modes of PEG in PEG coated HAP has been elucidated in this work, in terms of intermolecular interactions between PEG and HAP. Further these results suggest that the functionalization of nanoparticles may be independent of PEG mass.

Surface-modified silk hydrogel containing hydroxyapatite nanoparticle with hyaluronic acid-dopamine conjugate.

Silk fibroin/hydroxyapatite (SF/HAp) composite hydrogels were fabricated in this study, having different HAp contents (0-33 wt%) in SF matrix hydrogel. Surface modification of HAp nanoparticle with hyaluronic acid (HA)-dopamine (DA) conjugate improved a dispersibility of HAp in aqueous SF solution due to its negatively charged surface and therefore, fabrication of the SF composite hydrogel having HAp nanoparticles inside could be possible. Zeta potential of surface-modified HAP was examined by ELS. It demonstrates that surface of HAp was well modified to a negative charge with HA-DA. Morphological structure of SF hydrogel containing surface-modified HAp was examined by FE-SEM for analyzing pore structure of hydrogel and deposition of HAp nanoparticle in SF hydrogel. It was found that HAp nanoparticles were uniformly deposited on the pore wall of SF hydrogel. Structural characteristics of SF/HAp composite hydrogel was performed using X-ray diffraction and FT-IR analysis. It was found that ß-sheet crystal conformation of SF was significantly influenced by the HAp content during gelation of a mixture of SF and HAp. As a result of MTT assay, the SF/HAp composite hydrogel showed excellent cell proliferation ability. Therefore, it is expected that SF hydrogel containing HAp nanoparticles has a high potential as bone regeneration scaffold.

Improved production of reducing sugars from rice husk and rice straw using bacterial cellulase and xylanase activated with hydroxyapatite nanoparticles.

Purified bacterial cellulase and xylanase were activated in the presence of calcium hydroxyapatite nanoparticles (NP) with concomitant increase in thermostability about 35% increment in production of d-xylose and reducing sugars from rice husk and rice straw was obtained at 80°C by the sequential treatment of xylanase and cellulase enzymes in the presence of NP compared to the untreated enzyme sets. Our findings suggested that if the rice husk and the rice straw samples were pre-treated with xylanase prior to treatment with cellulase, the percentage increase of reducing sugar per 100g of substrate (starting material) was enhanced by about 29% and 41%, respectively. These findings can be utilized for the extraction of reducing sugars from cellulose and xylan containing waste material. The purely enzymatic extraction procedure can be substituted for the harsh and bio-adverse chemical methods.

Facile preparation of Artemisia argyi oil-loaded antibacterial microcapsules by hydroxyapatite-stabilized Pickering emulsion templating.

Artemisia argyi oil (AAO)-loaded antibacterial microcapsules with hydroxyapatite (HAp)/poly(melamine formaldehyde) (PMF) hybrid shells were facilely prepared by oil-in-water (O/W) Pickering emulsion templating. AAO-in-water emulsions were stabilized using HAp nanoparticles as the particulate emulsifier. The hybrid shells were fabricated by in situ polymerization of melamine formaldehyde pre-polymer (pre-MF) at the interface of the O/W Pickering emulsions. The prepared microcapsules were characterized in terms of size, morphology, component and thermal stability using scanning electronic microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), respectively. Moreover, both in vitro release and antimicrobial activity of the microcapsules were also evaluated. The results showed that the AAO-loaded microcapsules with HAp/PMF shells had a spherical shape and a rough surface. The microcapsules maintained excellent performances in the thermal stability, controlled release activity, antimicrobial effect and long-term antimicrobial activity. The release curves of AAO from the microcapsules could be well described by Higuchi kinetic model. The microcapsules may find applications as antibacterial agents in the areas of textiles, leather, rubber and coatings. In situ polymerization based on Pickering emulsion droplets opens up a new route to prepare a variety of hybrid microcapsules with a core-shell structure.

Application of hydroxyapatite nanoparticles in development of an enhanced formulation for delivering sustained release of triamcinolone acetonide.

We report an analysis of in vitro and in vivo drug release from an in situ formulation consisting of triamcinolone acetonide (TR) and poly(D,L-lactide-co-glycolide) (PLGA) and the additives glycofurol (GL) and hydroxyapatite nanoparticles (HA). We found that these additives enhanced drug release rate. We used the Taguchi method to predict optimum formulation variables to minimize the initial burst. This method decreased the burst rate from 8% to 1.3%. PLGA-HA acted as a strong buffer, thereby preventing tissue inflammation at the injection site caused by the acidic degradation products of PLGA. Characterization of the optimized formulation by a variety of techniques, including scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and Fourier transform near infrared spectroscopy, revealed that the crystalline structure of TR was converted to an amorphous form. Therefore, this hydrophobic agent can serve as an additive to modify drug release rates. Data generated by in vitro and in vivo experiments were in good agreement.