Designing bioinspired multifunctional nanoplatforms to support wound healing and skin regeneration: Mg-hydroxyapatite meets melanins.

Melanin is a multifunctional biological pigment that recently emerged as endowed with anti-inflammatory, antioxidant, and antimicrobial properties and with high potentialities in skin protection and regenerative medicine. Here, a biomimetic magnesium-doped nano-hydroxyapatite (MgHA) was synthesized and decorated with melanin molecules starting from two different monomeric precursors, i.e. 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and dopamine (DA), demonstrating to be able to polymerize on the surface of MgHA nanostructures, thus leading to a melanin coating. This functionalization was realized by a simple and green preparation method requiring mild conditions in an aqueous medium and room temperature. Complementary spectroscopy and electron imaging analyses were carried out to define the effective formation of a stable coating, the percentage of the organic compounds, and the structural properties of resulting melanin-coated nanostructures, which showed good antioxidant activity. The in vitro interaction with a cell model, i.e. mouse fibroblasts, was investigated. The excellent biocompatibility of all bioinspired nanostructures was confirmed from a suitable cell proliferation. Finally, the enhanced biological performances of the nanostructures coated with melanin from DHICA were confirmed by scratch assays. Jointly our findings indicated that low crystalline MgHA and melanin pigments can be efficiently combined, and the resulting nanostructures are promising candidates as multifunctional platforms for a more efficient approach for skin regeneration and protection.

The effect of supplementing the calcium phosphate cement containing poloxamer 407 on cellular activities.

Calcium phosphate cement (CPC) is generally used for bone repair and augmentation. Poloxamers are tri-block copolymers that are used as surfactants but have applications in drug and antibiotic delivery. However, their biological effects on bone regeneration systems remain unelucidated. Here, we aimed to understand how supplementing the prototype CPC with poloxamer would impact cellular activity and its function as a bone-grafting material. A novel CPC, modified beta-tricalcium phosphate (mß-TCP) powder, was developed through a planetary ball-milling process using a beta-tricalcium phosphate (ß-TCP). The mß-TCP dissolves rapidly and accelerates hydroxyapatite precipitation; successfully shortening the cement setting time and enhancing the strength. Furthermore, the addition of poloxamer 407 to mß-TCP could reduce the risk of leakage from bone defects and improve fracture toughness while maintaining mechanical properties. In this study, the poloxamer addition effects (0.05 and 0.1 g/mL) on the cellular activities of MC3T3-E1 cells cultured in vitro were investigated. The cell viability of mß-TCP containing poloxamer 407 was similar to that of mß-TCP. All specimens showed effective cell attachment and healthy polygonal extension of the cytoplasm firmly attached to hydroxyapatite (HA) crystals. Therefore, even with the addition of poloxamer to mß-TCP, it does not have a negative effect to osteoblast growth. These data demonstrated that the addition of poloxamer 407 to mß-TCP might be considered a potential therapeutic application for the repair and regeneration of bone defects.

Mn-Doped Nano-Hydroxyapatites as Theranostic Agents with Tumor pH-Amplified MRI-Signal Capabilities for Guiding Photothermal Therapy.

Background: The integration of diagnostic and therapeutic functions into a biosafe nanoplatform with intelligent response functions at the tumor microenvironment (TME) is a promising strategy for cancer therapy. Methods: Mn-doped nano-hydroxyapatite (nHAPMn) nanoparticles were successfully prepared via a simple coprecipitation method for magnetic resonance imaging (MRI)-guided photothermal therapy. This study is the first to report on the use of Mn to render biodegradable hydroxyapatite suitable for MRI and effective photothermal therapy (PTT) simultaneously by regulating the pH of nHAPMn during the preparation process. Results: Combined with near-infrared (NIR) laser irradiation, a photothermal conversion efficiency of 26% and effective photothermal lethality in vitro were achieved. Moreover, the degradation of nHAPMn led to the release of Mn ions and amplified the MRI signals in an acidic TME, which confirmed that nHAPMn had a good pH-responsive MRI capacity in solid tumors. In animal experiments, tumors in the nHAPMn5+NIR group completely abated after 14 days of treatment, with no significant recurrence during the experiment. Conclusion: Therefore, nHAPMn is promising as a nanotheranostic agent and can be effective in clinical diagnosis and therapy for treating cancer.

Comparative Analysis of Alternative Calcium Chelators for the Treatment of Calcific Band Keratopathy.

PURPOSE: In this study, we compared clinically relevant biochemical properties of each chelator for pH, osmolarity, and calcium chelation potential. METHODS: In total, 0.2 M K 2 EDTA and K 3 EDTA (BD vacutainer tubes by Becton, Dickinson and Company) and Na 2 EDTA (Sigma Aldrich) solutions were made. The pH of each solution was measured (Mettler Toledo pH meter), and the theoretical osmolarity was calculated. Next, we determined the calcium chelation potential of each EDTA salt by titrating it with 10 µmol of calcium hydroxyapatite or CaCl 2 containing Patton-Reeder colorimetric indicator. Statistical significance was analyzed using analysis of variance. RESULTS: The 0.2 M solutions of Na 2 EDTA, K 2 EDTA, and K 3 EDTA have pH values of 4.43, 5.71, and 9.191 and theoretical osmolarities of 600, 600, and 800 mOsm/L, respectively. Calcium chelation ability was similar among all 3 solutions: 0.94 to 0.98 mol of EDTA was needed to fully chelate 1 mol calcium ions of CaCl 2 ( P = 0.296), 0.100 to 0.108 mol of EDTA for 1 mol calcium ions of the hydroxyapatite aqueous suspension ( P = 0.296), and 0.992 to 0.996 mol for 1 mol calcium ions of hydroxyapatite in acidic solution ( P = 0.178). Compared with the clinical standard of 3% (30 mg/mL) Na 2 EDTA, approximately 3.3% (33 mg/mL) K 2 EDTA and 3.6% (36 mg/mL) K 3 EDTA are needed to chelate an equivalent amount of calcium. CONCLUSIONS: In this article, we provide clinically relevant biochemical properties of 2 alternatives to Na 2 EDTA and demonstrate comparable calcium chelation ability among all 3 solutions. In situations where sterile sources of Na 2 EDTA are unavailable, potassium EDTA may provide a convenient and equally effective method of treatment for band keratopathy.

Hydroxyapatite Use in Repair of Lateral Skull Base CSF Leaks Via Transmastoid Approach: When Does It Work?

OBJECTIVE: The objective of this study is to evaluate the efficacy and outcomes of using a transmastoid approach with hydroxyapatite cement to repair lateral skull base cerebrospinal fluid (CSF) leaks. STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary-level care hospital. PATIENTS: Surgical patients 18 years or older between 2013 and 2022 with spontaneous CSF leak. INTERVENTIONS: Trans-mastoid approach for skull base repair using hydroxyapatite cement. MAIN OUTCOME MEASURES: Failure rate of repair; location and size of defect, patient demographic factors. RESULTS: Of the 60 total defects (55 patients, 5 bilateral repairs) that underwent CSF leak repair using hydroxyapatite cement, the success rate was 91.66% (55 successful repairs). The average defect size in unsuccessful repairs was 1.15 cm compared with 0.71 cm for successful repairs. In addition, 80% (4/5) of the failed repairs were in the tegmen tympani region. Higher failure rate was noted in women (3/5) and in former smokers (4/5). Average time to recurrent symptoms was 1.75 years in the failed repair cohort. Of the patients with failed repairs, 4/5 were prescribed acetazolamide before their second procedure with successful second repair. In addition, five patients experienced postoperative headaches, three (5.4%) of whom required placement of VP shunts to relieve increased intracranial pressure. Two patients (3.6%) had complications of either infection or hearing loss. CONCLUSIONS: Transmastoid approach utilizing hydroxyapatite is a successful approach for CSF leak repair, with a low complication and failure rate. Women, prior smoking history, and larger defects in the tegmen tympani region may need alternative materials or approach for repair. Long follow-up is warranted as recurrence of symptoms might be delayed. In cases of benign intracranial hypertension, adjuvant treatment with either acetazolamide or VP shunt placement may prevent failures.

BMP-2 (and partially GDF-5) coating significantly accelerates and augments bone formation close to hydroxyapatite/tricalcium-phosphate/brushite implant cylinders for tibial bone defects in senile, osteopenic sheep.

Bilateral defects (diameter 8 mm) in the medial tibial head of senile, osteopenic female sheep (n = 48; 9.63 ± 0.10 years; mean ± SEM) were treated with hydroxyapatite (HA)/beta-tricalcium phosphate (ß-TCP)/dicalcium phosphate dihydrate (DCPD; brushite) cylinders coated with BMP-2 (25 or 250 micrograms) or growth differentiation factor (GDF)-5 (125 or 1250 micrograms; left side); cylinders without BMP served as controls (right side). Three, 6, and 9 months post-operation (n = 6 each group), bone structure and formation were analyzed in vivo by X-ray and ex vivo by osteodensitometry, histomorphometry, and micro-computed tomography (micro-CT) at 3 and 9 months. Semi-quantitative X-ray evaluation showed significantly increasing bone densities around all implant cylinders over time. High-dose BMP-2-coated cylinders (3 and 9 months) and low-dose GDF-5-coated cylinders (3 and 6 months) demonstrated significantly higher densities than controls (dose-dependent for BMP-2 at 3 months). This was confirmed by osteodensitometry at 9 months for high-dose BMP-2-coated cylinders (and selected GDF-5 groups), and was again dose-dependent for BMP-2. Osteoinduction by BMP-2 was most pronounced in the adjacent bone marrow (dynamic histomorphometry/micro-CT). BMP-2 (and partially GDF-5) significantly increased the bone formation in the vicinity of HA/TCP/DCPD cylinders used to fill tibial bone defects in senile osteopenic sheep and may be suitable for surgical therapy of critical size, non-load-bearing bone defects in cases of failed tibial head fracture or defect healing.

Improved Properties and Enhancement Strategies of Hydroxyapatite-Based Functional Granular Sludge for a High-Rate Partial Nitritation/Anammox System.

Retaining sufficient anammox bacteria (AnAOB) while keeping the anammox-based process stable is the focus of the study of anammox technology, especially in a one-stage partial nitritation/anammox (PNA) process. The use of hydroxyapatite (HAP) granules in an anammox-based process is innovative for its potential to improve the nitrogen removal rate and achieve simultaneous removal of phosphorus. In this study, the HAP-based granular sludge was employed using enhancement strategies for an excellent nitrogen removal performance in a one-stage PNA process. Compared to those of other granular sludge PNA systems, a remarkable sludge volume index of 7.8 mL/g and an extremely high mixed liquor volatile suspended solids of 15 g/L were achieved under a low hydraulic retention time of 2 h. Consequently, an unprecedented nitrogen removal rate as high as 4.8 kg N/m3/d at 25 °C was obtained under a nitrogen loading rate of 6 kg N/m3/d. After a long-term operation of 870 days, the enhancement strategies underlying the superior performance of the granular sludge were identified. These findings clearly demonstrate that the enhancement strategies are crucial for the superior operating performance of the PNA process, and they can promote the application of the anammox-based process.

Value-added application of cattle manure bottom ash for phosphorus recovery from water and replenishment in soil.

This study addresses ways to circulate the flow of phosphorus (P) from water to soil to improve water quality and provide a sustainable supply of P into soil. Here, bottom ash (BA_CCM), the byproduct of the combustion of cattle manure, which is performed for obtaining energy, was used to remove P in wastewater. Next, the P-captured BA_CCM was used as P fertilizer for rice growth. BA_CCM was primarily composed of Ca (49.4%), C (24.0%), and P (9.9%), and the crystalline phases of Ca were calcium carbonate (CaCO3) and hydroxyapatite (Ca5(PO4)3OH). The mechanism of P removal by BA_CCM involves the formation of hydroxyapatite by reacting Ca2+ with PO43-. A reaction time of 3 h was required to achieve P adsorption to BA_CCM, and the maximum P adsorption capacity of BA_CCM was 45.46 mg/g. The increase in solution pH reduced P adsorption. However, at pH > 5, the P adsorption amount was maintained regardless of the pH increase. The presence of 10 mM SO42- and CO32- reduced P adsorption by 28.4% and 21.5%, respectively, and the impact of the presence of Cl- and NO3- was less than 10%. The feasibility of BA_CCM was tested using real wastewater, and 3.33 g/L of BA_CCM dose achieved a P removal ratio of 99.8% and a residual concentration of <0.02 mg/L. The toxicity unit of BA_CCM determined for Daphnia magna (D. magna) was 5.1; however, the BA_CCM after P adsorption (P-BA_CCM) did not show any toxicity to D. magna. BA_CCM after P adsorption was used as an alternative to commercial P fertilizer. Rice fertilized with a medium level of P-BA_CCM showed better agronomic values for most agronomic traits, except root length, than that seen with the commercial P fertilizer. This study suggests that BA_CCM can be used as a value-added product to address environmental issues.

Morphology-Tailored Hydroxyapatite Nanocarrier for Rhizosphere-Targeted Phosphorus Delivery.

High hydrophilicity and soil fixation collectively hamper the delivery of phosphorus (P) released from conventional chemical phosphorus fertilizers (CPFs) to plant rhizosphere for efficient uptake. Here, a phosphorus nutrient nanocarrier (PNC) based on morphology-tailored nanohydroxyapatite (HAP) is constructed. By virtue of kinetic control of building blocks with designed calcium phosphate intermediates, rod-like and hexagonal prism-like PNCs are synthesized, both having satisfactory hydrophobicity (water contact angle of 105.4- 132.9°) and zeta potential (-17.43 to -58.4 mV at pH range from 3 to 13). Greenhouse experiments demonstrate that the P contents increase by up to 183% in maize rhizosphere and up to 16% in maize biomass when compared to the CPF. Due to the water potential gradient driven by photosynthesis and transpiration, both PNCs are stably transported to maize rhizosphere, and they are capable to counteract soil fixation prior to uptake by plant roots. Within the synergies of the HAP morphological characteristics and triggered phosphate starvation response, root anatomy confirms that two pathways are elucidated to enhance plant P replenishment from the PNCs. Together with structure tunability and facile synthesis, our results offer a new nanodelivery prototype to accommodate plant physiological traits by tailoring the morphology of HAP.

Nanoparticulate cell-free DNA scavenger for treating inflammatory bone loss in periodontitis.

Periodontitis is a common type of inflammatory bone loss and a risk factor for systemic diseases. The pathogenesis of periodontitis involves inflammatory dysregulation, which represents a target for new therapeutic strategies to treat periodontitis. After establishing the correlation of cell-free DNA (cfDNA) level with periodontitis in patient samples, we test the hypothesis that the cfDNA-scavenging approach will benefit periodontitis treatment. We create a nanoparticulate cfDNA scavenger specific for periodontitis by coating selenium-doped hydroxyapatite nanoparticles (SeHANs) with cationic polyamidoamine dendrimers (PAMAM-G3), namely G3@SeHANs, and compare the activities of G3@SeHANs with those of soluble PAMAM-G3 polymer. Both G3@SeHANs and PAMAM-G3 inhibit periodontitis-related proinflammation in vitro by scavenging cfDNA and alleviate inflammatory bone loss in a mouse model of ligature-induced periodontitis. G3@SeHANs also regulate the mononuclear phagocyte system in a periodontitis environment, promoting the M2 over the M1 macrophage phenotype. G3@SeHANs show greater therapeutic effects than PAMAM-G3 in reducing proinflammation and alveolar bone loss in vivo. Our findings demonstrate the importance of cfDNA in periodontitis and the potential for using hydroxyapatite-based nanoparticulate cfDNA scavengers to ameliorate periodontitis.

Osteocytes and the pathogenesis of hypophosphatemic rickets.

Since phosphorus is a component of hydroxyapatite, its prolonged deprivation affects bone mineralization. Fibroblast growth factor 23 (FGF23) is essential for maintaining phosphate homeostasis and is mainly produced by osteocytes. FGF23 increases the excretion of inorganic phosphate (Pi) and decreases the production of 1,25-dihydroxyvitamin D in the kidneys. Osteocytes are cells of osteoblastic lineage that have undergone terminal differentiation and become embedded in mineralized bone matrix. Osteocytes express FGF23 and other multiple genes responsible for hereditary hypophosphatemic rickets, which include phosphate-regulating gene homologous to endopeptidase on X chromosome (PHEX), dentin matrix protein 1 (DMP1), and family with sequence similarity 20, member C (FAM20C). Since inactivating mutations in PHEX, DMP1, and FAM20C boost the production of FGF23, these molecules might be considered as local negative regulators of FGF23. Mouse studies have suggested that enhanced FGF receptor (FGFR) signaling is involved in the overproduction of FGF23 in PHEX-deficient X-linked hypophosphatemic rickets (XLH) and DMP1-deficient autosomal recessive hypophosphatemic rickets type 1. Since FGFR is involved in the transduction of signals evoked by extracellular Pi, Pi sensing in osteocytes may be abnormal in these diseases. Serum levels of sclerostin, an inhibitor Wnt/ß-catenin signaling secreted by osteocytes, are increased in XLH patients, and mouse studies have suggested the potential of inhibiting sclerostin as a new therapeutic option for the disease. The elucidation of complex abnormalities in the osteocytes of FGF23-related hypophosphatemic diseases will provide a more detailed understanding of their pathogenesis and more effective treatments.

Remediation of chromium, zinc, arsenic, lead and antimony contaminated acidic mine soil based on Phanerochaete chrysosporium induced phosphate precipitation.

Microbial induced phosphate precipitation (MIPP) is an advanced bioremediation technology to reduce the mobility and bioavailability of heavy metals (HMs), but the high level of HMs would inhibit the growth of phosphate solubilizing microbes. This study proposed a new combination system for the remediation of multiple HMs contaminated acidic mine soil, which included hydroxyapatite (HAP) and Phanerochaete chrysosporium (P. chrysosporium, PC) that had high phosphate solubilizing ability and HMs tolerance. Experimental data suggested that in HAP/PC treatment after 35 d of remediation, labile Cr, Zn and As could be transformed into the stable fraction with the maximum immobilization efficiencies increased by 53.01 %, 22.43 %, and 35.65 %, respectively. The secretion of organic acids by P. chrysosporium was proved to promote the dissolution of HAP. Besides, the pH value, available phosphorus (AP) and organic matter (OM) increased in treated soil than in original soil, which also indicated the related dissolution-precipitation mechanism of HMs immobilization. Additionally, characterization results revealed that adsorption and ion exchange also played an important role in the remediation process. The overall results suggested that applying P. chrysosporium coupled with HAP could be considered as an efficient strategy for the remediation of multiple HMs contaminated mine soil and laid a foundation for the future exploration of soil microenvironment response during the remediation process.

Grafting biomaterials associated to topical glucocorticoid: effects on pre-osteoblastic cells (MC3T3-E1).

The topical glucocorticoid budesonide has been prescribed before and after sinus lift surgery as adjuvant drug treatment for maxillary sinus membrane inflammation. However, there is no study on the effects of budesonide on the regenerative process of bone grafting biomaterials. We investigated the effect of the association of budesonide with some biomaterials on the growth and differentiation capacity of pre-osteoblastic cells (MC3T3-E1 subclone 4). Xenogeneic (Bio-Oss and Bio-Gen) and synthetic hydroxyapatites (Osteogen, Bonesynth, and HAP-91) were tested in conditioned medium (1% w/v). The conditioned medium was then supplemented with budesonide (0.5% v/v). Cell viability was assessed using the MTT assay (48, 96, and 144 h), and mineralized nodules were quantified after 14 days of culture using the Alizarin Red Staining. Alkaline phosphatase activity was assessed through the release of thymolphthalein at day seven. All biomaterials showed little or no cytotoxicity. The Bio-Gen allowed significantly less growth than the control group regardless of the experimental time. Regarding differentiation potential of MC3T3-E1, the HAP-91-conditioned medium showed remarkable osteoinductive properties. In osteodifferentiation, the addition of budesonide favored the formation of mineral nodules when cells were cultured in medium conditioned with synthetic materials, whereas it weakened the mineralization potential of cells cultured in xenogeneic medium. Regardless of whether budesonide was added or not, Osteogen and Bio-Oss showed higher alkaline phosphatase activity than the other groups. Budesonide may improve bone formation when associated with synthetic biomaterials. Conversely, the presence of this glucocorticoid weakens the mineralization potential of pre-osteoblastic cells cultured with xenogeneic hydroxyapatites.

Effects of rhBMP-2-loaded hydroxyapatite granules/beta-tricalcium phosphate hydrogel (HA/ß-TCP/hydrogel) composite on a rat model of caudal intervertebral fusion.

The effects and inflammation-related side effects of bone morphogenetic protein (BMP)-2 on posterior lumbar interbody fusion are controversial. One of the potential causes for the inconsistent results is the uncontrolled release of BMP-2 from the collagen carrier. Therefore, BMP delivery systems that support effective bone regeneration while attenuating the side effects are strongly sought for. We developed NOVOSIS putty (NP), a novel composite material of hydroxyapatite (HA), beta-tricalcium phosphate (ß-TCP)/hydrogel, and BMP-2, which can sustainably release BMP-2 over 2 weeks. This study was aimed at comparing the effects and side effects of NP and collagen sponge (CS) containing BMP-2 using a rat caudal intervertebral fusion model. The fusion rates of NP with low and high doses of BMP-2 were significantly higher than those of an iliac bone (IB) graft, but those of CS with low and high doses of BMP-2 were not different from those of the IB graft. Furthermore, the incidences of ectopic bone formation and soft tissue swelling were significantly lower in the NP group than in the CS group. The HA/ß-TCP/hydrogel carrier enabled superior bone induction with low-dose BMP-2 and decreased the incidence of side effects caused by high-dose BMP-2 vis-à-vis the collagen carrier.

Functional role of inorganic trace elements in dentin apatite tissue-part III: Se, F, Ag, and B.

Dentin hydroxyapatite possesses a unique versatile structure which allows it to undergo ionic substitutions. Trace elements play pivotal roles within the oral cavity, especially in dentin apatite tissue. Therefore, it is critical to explore the role of these elements in dentin apatite structure. The roles of other inorganic elements in dentin apatite were discussed in part I (Mg, Sr, Zn, and Fe) and part II (Cu, Mn, Si, and Li) of these series. In the last part of the review series, the role of selenium, fluorine, silver, and boron in the regulation of dentin apatite structure and function was discussed. We evaluated how these elements affect the overall size, morphology, and crystallinity of dentin apatite crystals. Moreover, we investigated the importance of these elements in regulating the solubility of dentin apatite. An electronic search was performed on the role of these trace elements in dentin apatite from January 2010 to January 2022. The concentration of selenium in teeth has been explored only recently, particularly its incorporation into dentin apatite. Silver nanomaterials inhibit the growth of cariogenic microorganisms as well as arrest the degradation of collagen. Fluorine was found to have important roles in dentin remineralization and dentinal tubule occlusion, making it widely used for hydroxyapatite doping. Boron is critical for mineralized tissues like bone, dentin, and enamel, but its exact role in dentin apatite is unknown. Therefore, understanding the impact of these elements on dentin apatite is potentially transformative, as it may help to fill a significant knowledge gap in teeth mechanics.

Atom Probe Tomography of Encapsulated Hydroxyapatite Nanoparticles.

Hydroxyapatite nanoparticles (HAP NPs) are important for medicine, bioengineering, catalysis, and water treatment. However, current understanding of the nanoscale phenomena that confer HAP NPs their many useful properties is limited by a lack of information about the distribution of the atoms within the particles. Atom probe tomography (APT) has the spatial resolution and chemical sensitivity for HAP NP characterization, but difficulties in preparing the required needle-shaped samples make the design of these experiments challenging. Herein, two techniques are developed to encapsulate HAP NPs and prepare them into APT tips. By sputter-coating gold or the atomic layer deposition of alumina for encapsulation, partially fluoridated HAP NPs are successfully characterized by voltage- or laser-pulsing APT, respectively. Analyses reveal that significant tradeoffs exist between encapsulant methods/materials for HAP characterization and that selection of a more robust approach will require additional technique development. This work serves as an essential starting point for advancing knowledge about the nanoscale spatiochemistry of HAP NPs.

Porous Biphasic Calcium Phosphate Granules from Oyster Shell Promote the Differentiation of Induced Pluripotent Stem Cells.

Oyster shells are rich in calcium, and thus, the potential use of waste shells is in the production of calcium phosphate (CaP) minerals for osteopathic biomedical applications, such as scaffolds for bone regeneration. Implanted scaffolds should stimulate the differentiation of induced pluripotent stem cells (iPSCs) into osteoblasts. In this study, oyster shells were used to produce nano-grade hydroxyapatite (HA) powder by the liquid-phase precipitation. Then, biphasic CaP (BCP) bioceramics with two different phase ratios were obtained by the foaming of HA nanopowders and sintering by two different two-stage heat treatment processes. The different sintering conditions yielded differences in structure and morphology of the BCPs, as determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis. We then set out to determine which of these materials were most biocompatible, by co-culturing with iPSCs and examining the gene expression in molecular pathways involved in self-renewal and differentiation of iPSCs. We found that sintering for a shorter time at higher temperatures gave higher expression levels of markers for proliferation and (early) differentiation of the osteoblast. The differences in biocompatibility may be related to a more hierarchical pore structure (micropores within macropores) obtained with briefer, high-temperature sintering.

Synthesis, Characterization, Antibacterial Properties, and In Vitro Studies of Selenium and Strontium Co-Substituted Hydroxyapatite.

In this study, as a measure to enhance the antimicrobial activity of biomaterials, the selenium ions have been substituted into hydroxyapatite (HA) at different concentration levels. To balance the potential cytotoxic effects of selenite ions (SeO32-) in HA, strontium (Sr2+) was co-substituted at the same concentration. Selenium and strontium-substituted hydroxyapatites (Se-Sr-HA) at equal molar ratios of x Se/(Se + P) and x Sr/(Sr + Ca) at (x = 0, 0.01, 0.03, 0.05, 0.1, and 0.2) were synthesized via the wet precipitation route and sintered at 900 °C. The effect of the two-ion concentration on morphology, surface charge, composition, antibacterial ability, and cell viability were studied. X-ray diffraction verified the phase purity and confirmed the substitution of selenium and strontium ions. Acellular in vitro bioactivity tests revealed that Se-Sr-HA was highly bioactive compared to pure HA. Se-Sr-HA samples showed excellent antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus carnosus) bacterial strains. In vitro cell-material interaction, using human osteosarcoma cells MG-63 studied by WST-8 assay, showed that Se-HA has a cytotoxic effect; however, the co-substitution of strontium in Se-HA offsets the negative impact of selenium and enhanced the biological properties of HA. Hence, the prepared samples are a suitable choice for antibacterial coatings and bone filler applications.

Chondrogenic and BMP-4 primings confer osteogenesis potential to human cord blood mesenchymal stromal cells delivered with biphasic calcium phosphate ceramics.

Bone marrow mesenchymal stem/stromal cells (BMSCs) show great promise for bone repair, however they are isolated by an invasive bone marrow harvest and their regenerative potential decreases with age. Conversely, cord blood can be collected non-invasively after birth and contains MSCs (CBMSCs) that can be stored for future use. However, whether CBMSCs can replace BMSCs targeting bone repair is unknown. This study evaluates the in vitro osteogenic potential of unprimed, osteogenically primed, or chondrogenically primed CBMSCs and BMSCs and their in vivo bone forming capacity following ectopic implantation on biphasic calcium phosphate ceramics in nude mice. In vitro, alkaline phosphatase (intracellular, extracellular, and gene expression), and secretion of osteogenic cytokines (osteoprotegerin and osteocalcin) was significantly higher in BMSCs compared with CBMSCs, while CBMSCs demonstrated superior chondrogenic differentiation and secretion of interleukins IL-6 and IL-8. BMSCs yielded significantly more cell engraftment and ectopic bone formation compared to CBMSCs. However, priming of CBMSCs with either chondrogenic or BMP-4 supplements led to bone formation by CBMSCs. This study is the first direct quantification of the bone forming abilities of BMSCs and CBMSCs in vivo and, while revealing the innate superiority of BMSCs for bone repair, it provides avenues to induce osteogenesis by CBMSCs.

Phosphorus recovery via the formation of hydroxyapatite crystals at various nitrogen loading rate in an anammox-based UAFB.

A strategy that integrates the anammox and hydroxyapatite crystallization in an up-flow anaerobic fixed-bed reactor (UAFB) was investigated to simultaneously remove nitrogen and recover phosphorus. During the 430 days of operation, 73.1 ±â€¯6.6% of influent phosphorus was removed with an efficient nitrogen removal efficiency of 87.8 ±â€¯1.7%. After long-term operation, numerous acicular and micron-sized crystals were observed on the matured biofilm, of which the phosphorus content was around 10.21% (wt%) and hydroxyapatite was the main form of crystals through SEM-EDS, FT-IR and XRD analysis. The variation of substrates along the axial length of UAFB showed that phosphate removal was positively correlated with anammox and pH. Moreover, three anammox bacteria including Candidatus Brocadia (19.73%), Candidatus Jettenia (0.49%) and Candidatus Kuenenia (0.85%) were detected at the bottom of UAFB, while Candidatus Jettenia (4.67%) was dominant at the top. Hence, the anammox-based biofilm system could be alternative for the recovery of phosphorus from nutrient-rich wastewater.