Enhancement of mechanical and barrier properties of chitosan-based bionanocomposites films reinforced with eggshell-derived hydroxyapatite nanoparticles

In this study, Hydroxyapatite nanoparticles (HANPs), derived from eggshell waste, were employed to reinforce chitosan biopolymer-based films through the solvent-casting method. The impact of varying HANPs content (1%, 3%, 5%, and 10 wt %) in bionanocomposites was investigated. The influence of HANPs addition on the final film properties was comprehensively analyzed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), mechanical (tensile) testing, and Water Vapor Permeability (WVP). The morphological aspects of bionanocomposites and the dispersion of nanoparticles within the matrix were studied using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). The structural changes in the films were probed using Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) techniques. Results indicated that the addition of 1% and 3% of HANPs exhibited a higher glass transition temperature and improved thermal stability in bionanocomposites. Films with 3% HANPs content exhibited a notable increase in tensile strength, showing a 61.54% increase, while films with 1% HANPs content displayed a 52% reduction in WVP compared to pristine chitosan films. These findings underscore the significant potential of chitosan-hydroxyapatite bionanocomposite films for applications in food packaging applications.

A Comparative Study on Physicochemical Properties and In Vitro Biocompatibility of Sr-Substituted and Sr Ranelate-Loaded Hydroxyapatite Nanoparticles

Synthetic hydroxyapatite nanoparticles (nHAp) possess compositional and structural similarities to those of bone minerals and play a key role in bone regenerative medicine. Functionalization of calcium phosphate biomaterials with Sr, i.e., bone extracellular matrix trace element, has been proven to be an effective biomaterial-based strategy for promoting osteogenesis in vitro and in vivo. Functionalizing nHAp with Sr2+ ions or strontium ranelate (SrRAN) can provide favorable bone tissue regeneration by locally delivering bioactive molecules to the bone defect microenvironment. Moreover, administering an antiosteoporotic drug, SrRAN, directly into site-specific bone defects could significantly reduce the necessary drug dosage and the risk of possible side effects. Our study evaluated the impact of the Sr source (Sr2+ ions and SrRAN) used to functionalize nHAp by wet precipitation on its in vitro cellular activities. The systematic comparison of physicochemical properties, in vitro Sr2+ and Ca2+ ion release, and their effect on in vitro cellular activities of the developed Sr-functionalized nHAp was performed. The ion release tests in TRIS-HCl demonstrated a 21-day slow and continuous release of the Sr2+ and Ca2+ ions from both Sr-substituted nHAp and SrRAN-loaded HAp. Also, SrRAN and Sr2+ ion release kinetics were evaluated in DMEM to understand their correlation with in vitro cellular effects in the same time frame. Relatively low concentration (up to 2 wt %) of Sr in the nHAp led to an increase in the alkaline phosphatase activity in preosteoblasts and expression of collagen I and osteocalcin in osteoblasts, demonstrating their ability to boost bone formation.

Synthesis and characterization of hydroxyapatite nanoparticles and their effects on remineralization of demineralized enamel in the presence of Er,Cr: YSGG laser irradiation

BACKGROUND

This study aims to synthesize and characterize hydroxyapatite nanoparticles (nano-HA) and evaluate their effects on the remineralization of demineralized enamel in the presence to Er,CR: YSGG laser irradiation.

MATERIALS AND METHODS

Enamel specimens from 44 human molars were divided into four groups: control, demineralized enamel, demineralized enamel treated with nano-HA, and demineralized enamel treated with nano-HA followed by Er,Cr:YSGG laser irradiation (0.5, 20 Hz, 60 µs, 20 s). Vickers microhardness test was used to evaluate the enamel surface hardness. The morphology and chemistry of enamel surfaces were assessed using scanning electron microscopy (SEM) and Raman spectroscopy, respectively.

RESULT

The result of this study showed that the application of Er,CR: YSGG laser irradiation to demineralized enamel treated with nano-HA had the highest impact on its microhardness.

CONCLUSION

ER,CR: YSGG laser irradiation promotes enamel remineralization after treatment with nano HA.

Aspect ratio-dependent dual-regulation of the tumor immune microenvironment against osteosarcoma by hydroxyapatite nanoparticles

Accumulating studies demonstrated that hydroxyapatite nanoparticles (HANPs) showed a selective anti-tumor effect, making them a good candidate for osteosarcoma (OS) treatment. However, the capacity of HANPs with different aspect ratios to regulate tumor immune microenvironment (TIM) was scarcely reported before. To explore it, the three HANPs with aspect ratios from 1.86 to 6.25 were prepared by wet chemical method. After a 24 or 72 h-exposure of OS UMR106 cells or macrophages to the nanoparticles, the tumor cells exhibited immunogenic cell death (ICD) indicated by the increased production of calreticulin (CRT), adenosine triphosphate (ATP) and high mobility group box 1 (HMGB1), and macrophages were activated with the release of pro-inflammatory cytokines. Next, the beneficial crosstalk between tumor cells and macrophages generated in the presence of HANPs for improved anti-tumor immunity activation. In the OS-bearing cognate rat model, HANPs inhibited OS growth, which was positively correlated with CRT and HMGB1 expression, and macrophage polarization in the tumor tissues. Additionally, HANPs promoted CD8+ T cell infiltration into the tumor and systemic dendritic cell maturation. Particularly, HANPs bearing the highest aspect ratio exhibited the strongest immunomodulatory and anti-tumor function. This study suggested the potential of HANPs to be a safe and effective drug-free nanomaterial to control the TIM for OS therapy. STATEMENT OF SIGNIFICANCE: Emerging studies demonstrated that hydroxyapatite nanoparticles (HANPs) inhibited tumor cell proliferation and tumor growth. However, the underlying anti-tumor mechanism still remains unclear, and the capacity of HANPs without any other additive to regulate tumor immune microenvironment (TIM) was scarcely reported before. Herein, we demonstrated that HANPs, in an aspect ratio-dependent manner, showed the potential to delay the growth of osteosarcoma (OS) and to regulate TIM by promoting the invasion of CD8+ T cells and F4/80+ macrophages, and inducing immunogenic cell death (ICD) in tumors. This work revealed the new molecular mechanism for HANPs against OS, and suggested HANPs might be a novel ICD inducer for OS treatment.

Hydroxyapatite nanoparticles promote TLR4 agonist-mediated anti-tumor immunity through synergically enhanced macrophage polarization

Macrophages represent the most prevalent immune cells in the tumor micro-environment, making them an appealing target for tumor immunotherapy. One of our previous studies showed that hydroxyapatite nanoparticles (HANPs) enhanced Toll-like receptor 4 (TLR4) signal transduction in macrophages. This study was proposed to investigate how HANPs manipulated the phenotype and function of macrophage against 4T1 tumors in the presence or absence of MPLA, a low toxic Toll-like receptor 4 (TLR4) agonist. The results demonstrated that the addition of HANPs to MPLA significantly promoted cytokine secretion and macrophage polarization toward a tumoricidal M1 phenotype. Further, the resulting supernatant from HANPs/MPLA co-stimulated macrophages enhanced 4T1 tumor cells apoptosis compared to that from macrophages treated with a single component or PBS control. In particular, we found HANPs elicited immunogenic cell death (ICD) indicated by the increased expression of "danger signals", including HMGB1, CRT and ATP in 4T1 cells. Subsequently, the ICD derivatives-containing supernatant from HANPs-treated 4T1 cells activated macrophage and shifted the phenotype of the cells toward M1 type. Moreover, in a tumor-bearing mice model, HANPs and MPLA synergistically delayed tumor growth compared to PBS control, which was positively associated with the promoted macrophage polarization and ICD induction. Therefore, our findings demonstrated a potential platform to modulate the function of macrophages, and shed a new insight into the mechanism involving the immunomodulatory effect of HANPs for tumor therapy. STATEMENT OF SIGNIFICANCE: Polarizing macrophage toward tumoricidal phenotype by harnessing Toll-like receptor (TLR) agonists has been proven effective for tumor immunotherapy. However, the immunomodulatory potency of TLR agonists is limited due to immune suppression or tolerance associated with TLR activation in immune cells. Herein, we introduced hydroxyapatite nanoparticles (HANPs) to MPLA, a TLR4 agonist. The results demonstrated that the addition of HANPs to MPLA promoted macrophage shift toward tumoricidal M1 phenotype, supported a "hot" tumor transformation, and delayed 4T1 tumor growth. Moreover, we found that HANPs elicited immunogenic cell death that produced "danger" signals from cancer cells thereby further facilitated macrophage polarization. This work is significant to direct the rational design of HANPs coupled with or without TLR agonists for tumor immunotherapy.

Fabrication and characterization of gelatin-based nanocomposite edible film prepared from eggshell with anthocyanin as pH indicator to assure quality of food

Intelligent packaging with a pH indicator is a protective measure that can assure the food quality at the point of delivery or usage. This research targets to develop eggshell membrane gelatin-based hydroxyapatite (HAP) nanocomposite edible film incorporated with anthocyanin extracted from Jambolão (Syzygium cumini). The HAP nanoparticles were synthesized from eggshells, the size (< 100 nm) and morphology were confirmed by Dynamic light scattering (DLS), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). Eggshell gelatin film, eggshell gelatin film reinforced with HAP (Gel-HAP), and anthocyanin incorporated eggshell gelatin film reinforced with HAP (Gel-HAP-ACN) were prepared. The physicochemical, optical, and surface properties of the nanocomposite films were evaluated. Gel-HAP-ACN film had excellent light barrier characteristics than Gel-HAP and Gel films. The Gel-HAP-ACN film had enhanced antioxidant (57.71%) property than the gelatin film and also had antibacterial action against Salmonella typhi, Escherichia coli and Staphylococcus aureus. Hence, this report suggests Gel-HAP-ACN film for food packaging to assure the safety of the food.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05685-4.

Tailoring of hydroxyapatite nanoparticle surfaces of varying morphologies to facilitate counterion diffusion and subsequent protein denaturation

Rapid advances in nanotechnology have led to the synthesis and development of various nanomaterials with complex structures and appropriate surface functionalization in recent years. Specifically designed and functionalized nanoparticles (NPs) are increasingly researched and hold great potential in biomedical applications (for example, imaging, diagnostics and therapeutics). Yet, the surface functionalization and biodegradability of NPs play a significant role in their application. Understanding the interactions occurring at the interface between the NPs and the biological components is thus crucial for predicting the fate of the NPs. In this work we study the effect of trilithium citrate functionalization of the hydroxyapatite NPs (HAp NPs) with and without cysteamine modification and their subsequent interaction with hen egg white lysozyme and corroborate the conformational changes of the protein with effective diffusion of the lithium (Li⁺) counter ion.

Protective effects of resveratrol against genotoxicity induced by nano and bulk hydroxyapatite in Drosophila melanogaster

Hydroxyapatite (HAp) is a naturally occurring calcium phosphate mineral predominantly used for its biocompatibility in a number of areas such as bone grafting, prosthesis coating in dentistry, and targeted drug delivery. Since the nano form of HAp (nHAp) has gained popularity attributed to a re-mineralizing effect in dental repair procedures, concerns have been raised over safety and biocompatibility of these nanoparticles (NP). This study, therefore, aimed to (1) investigate mechanisms of potential genotoxicity and enhanced generation of reactive oxygen species (ROS) initiated by bulk and nano forms of HAp and (2) test in vivo whether resveratrol, a type of natural phenol, might mitigate the extent of potential DNA damage. The size of nHAp was determined to be 192.13 ± 9.91 nm after dispersion using transmission electron microscopy (TEM). Drosophila melanogaster was employed as a model organism to determine the genotoxic potential and adverse effects of HAp by use of (comet assay), mutagenic and recombinogenic activity (wing spot test), and ROS-mediated damage. Drosophila wing-spot tests demonstrated that exposure to nontoxic bulk and nHAp concentrations (1, 2.5, 5 or 10 mM) produced no significant recombination effects or mutagenicity. However, bulk and nHAp at certain doses (2.5, 5 or 10 mM) induced genotoxicity in hemocytes and enhanced ROS production. Resveratrol was found to ameliorate the genotoxic effects induced by bulk HAp and nHAp in comet assay. Data demonstrate that treatment with nano and bulk Hap-induced DNA damage and increased ROS generation D. melanogaster which was alleviated by treatment with resveratrol.

A novel route to enhance the dissolution of apatite: Structural incorporation of hydrogen phosphate

Potential use of hydroxyapatite nanoparticles (HANPs) [Ca₁₀(PO₄)₆(OH)₂] as slow P-release fertilizer (SRF) has recently attracted wider attention. However, commercially available HANP (with Ca/P ratio = 1.667) is the least soluble calcium phosphate and thus limits its full potential as an SRF in agronomic applications. In this research, we sought to enhance the dissolution rate of HANPs by enriching hydrogen phosphate (HPO₄^2-) species in the phosphate (PO₄^3-) structural sites. Seven different types of pure crystalline HANPs were synthesized at a range of Ca/P ratio from 1.46 (at pH 6.0) to 2.10 (at pH 12.0). Complementary results from FTIR and solid-state ³¹P MAS NMR spectroscopies showed that HPO₄^2- species is most abundant in HANPs crystallized at pH 6.0 and gradually depleted at higher pH products. The rate of depletion of HPO₄^2- species is proportional to the increase in carbonate incorporation into the HANP lattice, which preferentially forms B-type carbonated HANPs. The enhanced dissolution rate of HANPs due to hydrogen phosphate incorporation was tested using a flow-through macro-dialysis system that limits the partial transition of HANPs to other solid phases, which otherwise interfere with dissolution. The results show that the dissolution rate of HANPs increased with decreasing pH of synthesis and was highest in HANPs at pH 6.0. The dissolution rate differed by ten times between HANPs synthesized at pH 7.0 and 10.0. Overall, the atom-efficient synthetic route developed and the ability to tune the dissolution rate of HANPs are significant steps forward in improving the P-release efficiency of a potent SRF and is expected to contribute to efforts toward enhancing agricultural sustainability.

Recent Progress of Rare Earth Doped Hydroxyapatite Nanoparticles: Luminescence Properties, Synthesis and Biomedical Applications

Hydroxyapatite nanoparticles (HAP NPs) are host materials and can be modified with various substrates and dopants. Among them, rare earth (RE) ions doped HAP NPs have gathered attention due to their unique physicochemical and imaging properties. Compared to other fluorescence probes, RE-doped HAP NPs display advantages in high brightness, high contrast, photostability, nonblinking, and narrow emission bands. Meanwhile, their intrinsic features (composition, morphology, size, crystallinity, and luminescence intensity) can be adjusted by changing the dopant ratio, synthesizing temperature, reaction time, and techniques. And they have been used in various biomedical applications, including imaging probe, drug delivery, bone tissue engineering, and antibacterial studies. This review surveys the luminescent properties, fluorescence enhancement, synthetic methods, and biocompatibility of various RE-doped HAP NPs consolidated from different research works, for their employments in biomedical applications. For this literature review, an electronic search was conducted in the Pubmed, Web of Science, Google Scholar, Scopus and SciFinder databases, using the keywords: hydroxyapatite, rare earth, lanthanide, fluorescence, and imaging. Literature searches of English-language publications from 1979 with updates through April, 2022, and a total of 472 potential papers were identified. In addition, a few references were located by noting their citation in other studies reviewed. STATEMENT OF SIGNIFICANCE: Hydroxyapatite nanoparticles (HAP NPs) have a broad range of promising biological applications. Although prospective biomedical applications are not limited to rare earth-doped hydroxyapatite nanoparticles (RE-doped HAP NPs), some cases do make use of the distinctive features of RE-elements to achieve the expected functions for HAP families. This review surveys the luminescent properties, synthetic methods, and biocompatibility of various RE-doped HAP NPs consolidated from different research works, for their employments in biomedical applications, including imaging probe, drug delivery, bone tissue repair and tracking, and anti-bacteria. Overall, we expect to shed some light on broadening the research and application of RE-doped HAP NPs in biomedical field.

Exposure to hydroxyapatite nanoparticles enhances Toll-like receptor 4 signal transduction and overcomes endotoxin tolerance in vitro and in vivo

Emerging studies indicate hydroxyapatite nanoparticles (HANPs) exhibit modest immunogenicity to elicit innate immune response which might involve Toll-like receptor 4 (TLR4) activation. This study was proposed to elucidate how HANPs direct over TLR4 signal activity in macrophage in response to TLR4 ligand, lipopolysaccharide (LPS). The present study for the first time reveals that HANPs themselves can induce TLR4 endocytosis and activate pathways both of nuclear factor-kappa B (NF-κB) and interferon regulatory factor 3 (IRF3), which potentially trigger the production of inflammatory cytokine by macrophage. Further, HANPs dose-dependently reprogram over LPS driven TLR4 signaling transduction in macrophage, leading to synergistically augmented innate immune response. In particular, HANPs synergize with LPS to promote macrophage polarization toward M1 phenotype. Moreover, HANPs abrogate the endotoxin tolerance in macrophages by restoring the production of inflammatory cytokines from macrophage in response to secondary LPS stimulation, and enhance the responsiveness of the body to LPS re-challenge in the endotoxin tolerance mice model. Therefore, this study sheds a new light on the mechanism by which HANPs drive the innate immune response, and offers a powerful strategy to potentiate LPS mediated TLR4 signaling activation in macrophage. STATEMENT OF SIGNIFICANCE: In recent years, increasing attention has been given to hydroxyapatite nanoparticles (HANPs) on how they interact with immune cells for achieving appropriate biological effect such as bone tissue repair, soft tissue filler, tumor treatment, vaccine delivery, et al. This study indicated HANPs can induce TLR4 signaling activation. In the further, HANPs dose-dependently synergize with LPS to program over LPS induced TLR4 signaling transduction in macrophage, to favor macrophage polarizing toward M1 phenotype, as well as to abrogate immune tolerance in macrophage in response to repeated LPS stimulation. This work opens a window for the intrinsic mechanism of HANPs to drive immune response and facilitate to direct the rational use or design of HANPs for their better biomedical application.

Chemical and computational strategy for design of "switchable" sorbent based on hydroxyapatite nanoparticles for dispersive micro-solid phase extraction of tetracyclines

A challenging task in analytical chemistry is an application of renewable and natural materials for isolation of hazardous substances such as antimicrobial drugs from environmental samples. The energy-efficient scalable hydrothermal procedure to fabricate the eco-friendly "switchable" sorbent based on hydroxyapatite nanoparticles with in situ modified surface using a small amount of capping agents was developed. Sorbents characterization including the surface composition investigation via quantum-chemical calculation based on the original approach was provided. The sorbents demonstrated well expressed controllable surface switching and high values of the sorption and elution efficiency for tetracycline, oxytetracycline, and chlortetracycline achieved by simple change of the medium pH. These processes were thoroughly discussed based on the results of chemical and computational experiments. A simple and universal strategy for choosing a suitable sorbent for solid phase extraction of target analytes was proposed for the first time. It was shown that the developed eco-friendly sample preparation procedure with use of biocompatible sorbents could be applied both for removal of target analytes from sample matrix (water samples) as well as for the quantitative analytes determination after elution step. It is believed that the presented research is significant for the determination of different amphoteric analytes in wide variety of samples.

Structure and properties of cellulose/HAP nanocomposite hydrogels

The exploiting of abundant natural polymers as potential absorbents for heavy metal ions is attracting. Cellulose is the most abundant natural polymer and exhibits amazing properties such as high chemical stability, hydrophilicity and biodegradability. However, some properties of pure cellulose-based materials including adsorbability are usually not enough, so it is important to improve their properties to broaden their applications. In the present work, hydroxyapitite (HAP) nanoparticles were prepared and introduced to improve the cellulose hydrogel (CG) properties. The structure and properties of the resultant cellulose/HAP nanocomposite hydrogels (CHG) were characterized and studied systematically. The results indicated that HAP nanoparticles was fixed and distributed evenly in CG. The maximum decomposition temperature increased gradually from 334.6 °C for CG to 346.7 °C for CHG, and the compressive strength increased gradually from 100 kPa for CG to 570 kPa for CHG with the increase of HAP content, respectively. Moreover, the adsorption capacity (q_e) value of CHG towards Cu²⁺ could reach more than 300% higher than that of CG. As a potential absorbent, CHG exhibited relatively good recyclability of more than 78% after 10 cycles. Therefore, the introduction of HAP improved the properties of CG greatly, showing wide potential applications.

Potential Osteoinductive Effects of Hydroxyapatite Nanoparticles on Mesenchymal Stem Cells by Endothelial Cell Interaction

Nano-hydroxyapatite (nano-HA) has attracted substantial attention in the field of regenerative medicine. Endothelial cell (EC)-mesenchymal stem cell (MSC) interactions are necessary for bone reconstruction, but the manner in which nano-HA interacts in this process remains unknown. Herein, we investigated the cytotoxicity and osteoinductive effects of HA nanoparticles (HANPs) on MSCs using an indirect co-culture model mediated by ECs and highlighted the underlying mechanisms. It was found that at a subcytotoxic dose, HANPs increased the viability and expression of osteoblast genes, as well as mineralized nodules and alkaline phosphatase production of MSCs. These phenomena relied on HIF-1α secreted by ECs, which triggered the ERK1/2 signaling cascade. In addition, a two-stage cell-lineage mathematical model was established to quantitatively analyze the impact of HIF-1α on the osteogenic differentiation of MSCs. It demonstrated that HIF-1α exerted a dose-dependent stimulatory effect on the osteogenic differentiation rate of MSCs up to 1500 pg/mL, which was in agreement with the above results. Our data implied that cooperative interactions between HANPs, ECs, and MSCs likely serve to stimulate bone regeneration. Furthermore, the two-stage cell-lineage model is helpful in vitro system for assessing the potential influence of effector molecules in bone tissue engineering.

Hydroxyapatite Nanoparticles as Injectable Bone Substitute Material in a Vertical Bone Augmentation Model

AIM

The aim of this in vivo study was to evaluate the utility of bone graft gel containing hydroxyapatite nanoparticles in promoting bone regeneration in a mouse model of vertical bone augmentation.

MATERIALS AND METHODS

Gel implants with high and low viscosity were compared for their bone regenerating ability. Bone formation at 12 weeks and material reactions were observed radiographically and histologically.

RESULTS

Radiological analysis showed that most bone augmentation area in the graft material occurred in the fourth week after surgery regardless of the viscosity of the gel, and then gradually decreased. The volume of bone augmentation area was greater in the high-viscosity implant group than in the low-viscosity implant group at all time points, the difference was statistically significant at 8 and 12 weeks. Histological evaluation indicated that the new bone area was significantly smaller in the high-viscosity implant group.

CONCLUSION

Gelatinous graft materials containing hydroxyapatite nanoparticles were confirmed to be useful in vertical bone augmentation.

Synergistic effect of curcumin and chitosan nanoparticles on nano-hydroxyapatite-induced reproductive toxicity in rats

Although the toxicity/biocompatibility of hydroxyapatite nanoparticles (HAPNPs), a prospective nano-biomaterial, is extensively studied, its interaction on the reproductive system following exposure is less exploited. In the present study, male rats were exposed to HAPNPs (300 mg/kg BW) to determine its possible reproductive toxicity. Also, the protective effects of chitosan (CSNPs, 280 mg/kg BW) and/or curcumin (CurNPs, 15 mg/kg BW) nanoparticles against HAPNPs-induced reproductive toxicity were studied. Animals were orally gavage daily with respective doses for 45 consecutive days. The obtained results indicated that HAPNPs caused a significant decrease in sperm count, sperm motility, testosterone hormone, steroidogenic enzymes (17-ketosteroid reductase and 17β-hydroxysteroid dehydrogenase), and antioxidant enzymes (glutathione peroxidase, glutathione S-transferase, catalase, and superoxide dismutase) in addition to total antioxidant capacity and reduced glutathione. LH and FSH, abnormal sperm, oxidative stress parameters (thiobarbituric acid-reactive substances (TBARS), nitric oxide (NO), and 8-hydroxy-deoxyguanosine (8-OHdG)), p53, TNFα, and interleukin-6 were significantly increased. The DNA damage was also analyzed by assaying 8-OHdG level which is considered as an indicator of genotoxicity and also suppression of the gene expression of mtTFA, induction of UCP2. Similarly, the histopathological evaluation was also changed following exposure to HAPNPs. The antioxidant activity of CSNPs and CurNPs showed mitigating effect against reproductive deterioration induced by HAPNPs throughout improvements in semen characteristics, sex hormones, inflammatory factors, and antioxidant status. The present study concluded that HAPNPs induced reproductive toxicity and it is important to use nano-antioxidants CSNPs and CurNPs as protective agents.

Response surface methodology optimized electrochemical DNA biosensor based on HAPNPTs/PPY/MWCNTs nanocomposite for detecting Mycobacterium tuberculosis

An important issue in the prognosis of tuberculosis (TB) is a short period between correct diagnosis and start the suitable antibiotic therapy. So, a rapid and valid method for detection of Mycobacterium tuberculosis (M. tb) complex is considered as a necessity. Herein, a rapid, low-cost, and PCR-free DNA biosensor was developed based on multi-walled carbon nanotubes (MWCNTs), polypyrrole (PPy), and hydroxyapatite nanoparticles (HAPNPs) for highly sensitive and specific recognition of M.tb. The biosensor consisted of M.tb ssDNA probe covalently attached to the HANPs/PPy/MWCNTs/GCE surface that hybridized to a complementary target sequence to form a duplex DNA. The M.tb target recognition was based on the oxidation signal of the electroactive Methylene Blue (MB) on the surface of the modified GCE using differential pulse voltammetry (DPV) method. It is worth to mention that for the first time Plackett-Burman (PB) screening design and response surface method (RSM) based on central composite design (CCD) was applied as a powerful and an efficient approach to find optimal conditions for maximum M.tb biosensor performance leading to simplicity and rapidity of operation. The proposed DNA biosensor exhibits a wide detection range from 0.25 to 200.0 nM with a low detection limit of 0.141 nM. The performance of designed biosensor for clinical diagnosis and practical applications was revealed through hybridization between DNA probe-modified GCE and extracted DNA from sputum clinical samples.

Selenium-doped hydroxyapatite nanoparticles for potential application in bone tumor therapy

In the present study we have studied the incorporation and release of selenite ions (SeO₃^2-) in hydroxyapatite nanoparticles for the treatment of bone tumors. Two types of selenium-doped hydroxyapatite (HASe) nanoparticles (NPs) with a nominal Se/(P + Se) molar ratio ranging from 0.01 up to 0.40 have been synthesized by a new and mild wet method. The two series of samples were thoroughly characterized and resulted to be slightly different in chemical composition, but they had similar properties in terms of morphology and degree of crystallinity. Selenium release from HASe was investigated under neutral and acidic conditions to simulate both healthy tissues and the low-pH environment surrounding a tumor mass, respectively. The comparison of the release profiles at two pH values clearly showed the possibility of modulating the Se release by simply changing the amount of Se in the HASe particles. The correlation between the physicochemical properties of HASe and their dissolution as a function of pH has been also investigated to facilitate future application of the NPs as chemotherapeutic adjuvant agents. Finally, the cytotoxic activity of HASe was evaluated using prostate (PC3) and breast (MDA-MB-231) cancer cells as well as healthy human bone marrow stem cells (hBMSc). HASe NPs exerted a good cytocompatibility at low concentration of Se but, with high Se doping concentration, they displayed strong cytotoxicity.

Cobalt-doped hydroxyapatite nanoparticles as a new eco-friendly catalyst of luminol-H2O2 based chemiluminescence reaction: Study of key factors, improvement the activity and analytical application

In this study, a novel catalyst based on hydroxyapatite doped by cobalt for chemiluminescence reaction of luminol oxidation by H₂O₂ was suggested for the first time. The catalyst nanoparticles were synthesized by a hydrothermal method and characterized by various methods including density functional theory calculations. The impact of nanoparticles sizes, surface composition, contact efficiency and crystallinity on chemiluminescence intensity were investigated. The maximum chemiluminescence intensity was obtained for polycrystalline nanoparticles. This phenomenon was studied in detail and applied for chemiluminescence analysis for the first time. The chemiluminescence determination of sulfonamides as model analytes was considered. The sensing was based on sulfonamides-dependent quenching of the chemiluminescence intensity in the presence of novel catalyst existed as an aqueous suspension.

Electrochemical sensing of L-ascorbic acid by using a glassy carbon electrode modified with a molybdophosphate film

Electrochemical sensing of L-ascorbic acid (AA) is reported based on the use of a redox-active molybdophosphate film on a glassy carbon electrode (GCE). Molybdophosphate is formed by reacting hydroxyapatite nanoparticles with sodium molybdate. The modified GCE can be utilized for detection of AA, typically at a working potential of 0.4 V (vs. Ag/AgCl). The GCE has a decreased overpotential and enhanced sensitivity (219 μA·mM^-1·cm^-2). Response is linear in the 1 μM to 1.5 mM AA concentration range, and the limit of detection is 4 nM. The selectivity of this sensor makes it a useful tool for accurate determination of AA in practical samples as shown for a vitamin C tablet and for spiked beverages. Graphical abstract An electrochemical sensing platform is reported that is based on the use of a redox-active molybdophosphate film that was formed via reacting hydroxyapatite nanoparticles (HAP-NPs) with sodium molybdate. Graphical abstract contains poor quality of text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.We have uploaded the graphical abstract as PDF format.

Adsorption/desorption study of antibiotic and anti-inflammatory drugs onto bioactive hydroxyapatite nano-rods

The use of high doses of antibacterial and anti-inflammatory drugs for patients with bone diseases, associated to implants or bone filling, can develop adverse effects; and consequently, it promotes to think new strategies to avoid this problem. In this work, it has been described the adsorption/release (or desorption) behavior of two drugs, ciprofloxacin (CIP) and ibuprofen (IBU), onto hydroxyapatite (nano-HA) at 37 °C. Through Ultraviolet-Visible (UV-Vis) spectroscopy, the concentrations of both drugs in adsorption, kinetic and desorption processes were obtained. The Fourier Transformed-Infrared (FT-IR) spectroscopy, Zeta-potential (ζ-potential), High-Resolution Transmission Electron Microscopy (H-TEM) and x-Ray Diffraction (xRD) were also used to characterize bared nanoparticles and those with adsorbed drugs. Five adsorption models (Langmuir, Freundlich, Sips, Temkin and Dubinin-Radushkevich) were used for describing the behavior of both active compounds. The adsorption processes (CIP/nano-HA and IBU/nano-HA) were better predicted by the Sips model than by the others. The kinetic adsorption data were processed, for both active agents, by application of Avrami's model. Desorption/release process (of both drugs) was evaluated though Korsmeyer-Peppas (K-P) model. Owing to the predictability of these systems, we propose the use of these active ceramics as potential bone filler for improving the treatment against bacterial bone infections and to avoid its associated inflammatory process.

Electrophoretic deposition of chitosan reinforced graphene oxide-hydroxyapatite on the anodized titanium to improve biological and electrochemical characteristics

Chitosan reinforced hydroxyapatite-graphene oxide (CS-GO-HA) nanocomposite coatings were developed using electrophoretic deposition process in order to improve the biological and electrochemical properties of Ti surface. Moreover, the role of anodized layer on the physical and electrochemical properties of the CS-GO-HA nanocomposite coating was evaluated. After synthesize of HA-GO nanopowder using a sol-gel process, nanocomposite coatings with various concentrations of chitosan (0.5, 1 and 1.5 mg/ml) were produced. Increasing the chitosan content lowered the deposition rate of HA-GO nanoparticles, reduced the coating thickness and diminished apatite-formation ability and biocompatibility. Noticeably, MG63 cell viability significantly reduced form 119.3 ± 5.1 (% control) to 51.9 ± 14.8 (% control), when the chitosan concentration increased from 0.5 to 1.5 mg/ml. In addition, the CS-GO-HA coating containing 0.5 mg/ml chitosan revealed the best barrier property owing to the less crack formation. Furthermore, anodizing of titanium substrate and formation of TiO₂ nanotube (TiNT) resulted in the formation of crack-free and homogeneous CS-GO-HA coatings without any observable defect. Moreover, the TiNT formation noticeably improved barrier resistance of the coating (6.7 times) due to better adhesion governed between coating and substrate. Our results confirmed that the surface modification using both anodizing of Ti substrate and electrophoretic deposition of ternary CS-GO-HA nanocomposite coating with 0.5 mg/ml chitosan successfully improves electrochemical properties, bioactivity and cell function, which makes it promising for bone implant applications.

A dual-channel homogeneous aptasensor combining colorimetric with electrochemical strategy for thrombin

In this protocol, a dual-channel homogeneous aptasenor was proposed for protein molecule determination, employing thrombin as target analyte. The colorimetric and electrochemical transducers were combined in a single analytical system for signal readout. In this dual-channel sensing strategy, the G-quadruplex sequence was released and incorporated with hemin to form DNAzyme for naked-eye colorimetric detection. Meanwhile, the hydroxyapatite nanoparticle as signal probe was combined with magnetic nanoparticles to construct sandwich-type structure for generating the electrochemical current when thrombin was present in solution. By introducing two kinds of reporter probes and transducers, this dual-channel sensor produced two different kinds of signal to improve the analytical accuracy and diversity. The results revealed that the dual-channel sensor achieved the quantatitive determination of thrombin with low limit of detection (0.40 fM) and wide range (0.1 fM to 1 nM), which offer a promise for rapid and accurate detection of biomolecule.

Crystallinity of hydroxyapatite drives myofibroblastic activation and calcification in aortic valves

Calcific aortic valve disease (CAVD) is an inexorably degenerative pathology characterized by progressive calcific lesion formation on the valve leaflets. The interaction of valvular cells in advanced lesion environments is not well understood yet highly relevant as clinically detectable CAVD exhibits calcifications composed of non-stoichiometric hydroxyapatite (HA). In this study, Fourier transform infrared spectroscopic imaging was used to spatially analyze mineral properties as a function of disease progression. Crystallinity (size and perfection) increased with increased valve calcification. To study the relationship between crystallinity and cellular behavior in CAVD, valve cells were seeded into 3D mineral-rich collagen gels containing synthetic HA particles, which had varying crystallinities. Lower crystallinity HA drove myofibroblastic activation in both valve interstitial and endothelial cells, as well as osteoblastic differentiation in interstitial cells. Additionally, calcium accumulation within gels depended on crystallinity, and apoptosis was insufficient to explain differences in HA-driven cellular activity. The protective nature of endothelial cells against interstitial cell activation and calcium accumulation was completely inhibited in the presence of less crystalline HA particles. Elucidating valve cellular behavior post-calcification is of vital importance to better predict and treat clinical pathogenesis, and mineral-containing hydrogel models provide a unique 3D platform to evaluate valve cell responses to a later stage of valve disease.

STATEMENT OF SIGNIFICANCE

We implement a 3D in vitro platform with embedded hydroxyapatite (HA) nanoparticles to investigate the interaction between valve interstitial cells, valve endothelial cells, and a mineral-rich extracellular environment. HA nanoparticles were synthesized based on analysis of the mineral properties of calcific regions of diseased human aortic valves. Our findings indicate that crystallinity of HA drives activation and differentiation in interstitial and endothelial cells. We also show that a mineralized environment blocks endothelial protection against interstitial cell calcification. Our HA-containing hydrogel model provides a unique 3D platform to evaluate valve cell responses to a mineralized ECM. This study additionally lays the groundwork to capture the diversity of mineral properties in calcified valves, and link these properties to progression of the disease.

Determination of protein kinase A activity and inhibition by using hydroxyapatite nanoparticles as a fluorescent probe

The authors describe a fluorometric method for the determination of the activity and inhibition of protein kinase A (PKA). In the presence of ATP, PKA catalyzes the transfer of phosphate groups from ATP to a peptide, and the generated phosphorylated peptide quenches the fluorescence (measured at excitation/emission peaks of 340/440 nm) of the hydroxyapatite nanoparticles (HAP-NPs). A linear logarithmic relationship of PKA concentrations with fluorescence intensity in the range from 1 to 50 U·L^-1 was obtained, and the lower limit of detection (LOD) is 0.5 U·L^-1. This is much lower than LODs reported in the literature. The PKA inhibitor H-89 was studied, and the inhibition plot has a sigmoidal shape with a half-maximal inhibitory concentration of around 750 nM of H-89. At a 4.5 nM level of H-89, fluorescence of HAP-NPs fell to levels of no PKA controls, demonstrating that the assay is a viable tool to screen for kinase inhibitors. An assay with Hela cell lysates in combination with forskolin (an activator of adenylyl cyclase) and IBMX (a phosphodiesterase inhibitor used to activate the cellular activity of PKA) resulted in decreased fluorescence of HAP-NPs. This suggests that the assay can be applied for testing in vitro cell kinase activity. In our perception, this method will enable high-throughput screening for kinase-related drugs and fluorometric enzymatic detection in various areas. Graphical abstract Fluorescence assay based on hydroxyapatite nanoparticles (HAP) fluorescence quenching was developed for analysis of the activity and inhibition of protein kinase A (PKA).

Selective effect of hydroxyapatite nanoparticles on osteoporotic and healthy bone formation correlates with intracellular calcium homeostasis regulation

Adequate bone substitutes osseointegration has been difficult to achieve in osteoporosis. Hydroxyapatite of the osteoporotic bone, secreted by pathologic osteoblasts, had a smaller crystal size and lower crystallinity than that of the normal. To date, little is known regarding the interaction of synthetic hydroxyapatite nanoparticles (HANPs) with osteoblasts born in bone rarefaction. The present study investigated the biological effects of HANPs on osteoblastic cells derived from osteoporotic rat bone (OVX-OB), in comparison with the healthy ones (SHM-OB). A selective effect of different concentrations of HANPs on the two cell lines was observed that the osteoporotic osteoblasts had a higher tolerance. Reductions in cell proliferation, ALP activity, collagen secretion and osteoblastic gene expressions were found in the SHM-OB when administered with HANPs concentration higher than 25µg/ml. In contrast, those of the OVX-OB suffered no depression but benefited from 25 to 250µg/ml HANPs in a dose-dependent manner. We demonstrated that the different effects of HANPs on osteoblasts were associated with the intracellular calcium influx into the endoplasmic reticulum. The in vivo bone defect model further confirmed that, with a critical HANPs concentration administration, the osteoporotic rats had more and mechanically matured new bone formation than the non-treated ones, whilst the sham rats healed no better than the natural healing control. Collectively, the observed epigenetic regulation of osteoblastic cell function by HANPs has significant implication on defining design parameters for a potential therapeutic use of nanomaterials.

STATEMENT OF SIGNIFICANCE

In this study, we investigated the biological effects of hydroxyapatite nanoparticles (HANPs) on osteoporotic rat bone and the derived osteoblast. Our findings revealed a previously unrecognized phenomenon that the osteoporotic individuals could benefit from higher concentrations of HANPs, as compared with the healthy individuals. The in vivo bone defect model confirmed that, with a critical HANPs concentration administration, the osteoporotic rats had more mechanically matured new bone formation than the non-treated ones, whilst the sham rats healed no better than the natural healing control. The selective effect of HANPs might be associated with the intracellular calcium influx into the endoplasmic reticulum. Collectively, the observed epigenetic regulation by HANPs has significant implication on defining design parameters for a potential therapeutic use of nanomaterials in a pathological condition.

Hybrid nanofibers based on poly-caprolactone/gelatin/hydroxyapatite nanoparticles-loaded Doxycycline: Effective anti-tumoral and antibacterial activity

Cancer is one of the leading causes of morbidity and mortality Worldwide, 19.3 million new cancer cases are expected to be identified in 2025. Among the therapeutic arsenal to cancer control one could find the Doxycycline and the nano hydroxyapatite. The Doxycycline (Dox) not only shown antibiotic effect but also exhibits a wide range of pleiotropic therapeutic properties as the control of the invasive and metastatic cancer cells characteristics. The purpose of the present study was to evaluate both cytotoxicity in vitro and antibacterial activity of electrospun Dox-loaded hybrid nanofibrous scaffolds composed by hydroxyapatite nanoparticles (nHA), poly-ε-caprolactone (PCL) and gelatin (Gel) polymers. Both nHA and Dox were dispersed into different PCL/Gel ratios (70:30, 60:40, 50:50wt%) solutions to form electrospun nanofibers. The nHA and Dox/nHA/PCL-Gel hybrid nanofibers were characterized by TEM microscopy. In vitro Dox release behavior from all of these Dox-loaded nHA/PCL-Gel nanofibers showed the same burst release profile due to the high solubility of Gel in the release medium. Antibacterial properties of nanofiber composites were evaluated using Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Porphyromonas gingivalis (P. gingivalis) bacteria. The co-delivery of nHA particles and Dox simultaneously exhibited inhibition of bacterial growth more efficiently than the delivery of either Dox or nHA at the same concentrations, indicating a synergistic effect. The results showed that cancer cell tested had different sensibility to co-delivery system. On the whole, A-431 cells were found exhibited the most pronounced synergistic effect compared to CACO-2 and 4T1 cancer cells. Based on the anticancer as well as the antimicrobial results in this study, the developed Dox/nHA/PCL-Gel composite nanofibers are suitable as a drug delivery system with potential applications in the biomedical fields.

Synthesis and characterization of amino acid-functionalized calcium phosphate nanoparticles for siRNA delivery

Small interfering RNAs (siRNA) are short nucleic acid fragments of about 20-27 nucleotides, which can inhibit the expression of specific genes. siRNA based RNAi technology has emerged as a promising method for the treatment of a variety of diseases. However, a major limitation in the therapeutic use of siRNA is its rapid degradation in plasma and cellular cytoplasm, resulting in short half-life. In addition, as siRNA molecules cannot penetrate into the cell efficiently, it is required to use a carrier system for its delivery. In this work, chemically and morphologically different calcium phosphate (CaP) nanoparticles, including spherical-like hydroxyapatite (HA-s), needle-like hydroxyapatite (HA-n) and calcium deficient hydroxyapatite (CDHA) nanoparticles were synthesized by the sol-gel technique and the effects of particle characteristics on the binding capacity of siRNA were investigated. In order to enhance the gene loading efficiency, the nanoparticles were functionalized with arginine and the morphological and their structural characteristics were analyzed. The addition of arginine did not significantly change the particle sizes; however, it provided a significantly increased binding of siRNA for all types of CaP nanoparticles, as revealed by spectrophotometric measurements analysis. Arginine functionalized HA-n nanoparticles showed the best binding behavior with siRNA among the other nanoparticles due to its high, positive zeta potential (+18.8mV) and high surface area of Ca⁺⁺ rich "c" plane. MTT cytotoxicity assays demonstrated that all the nanoparticles tested herein were biocompatible. Our results suggest that high siRNA entrapment in each of the three modified non-toxic CaP nanoparticles make them promising candidates as a non-viral vector for delivering therapeutic siRNA molecules to treat cancer.

Surface-enrichment with hydroxyapatite nanoparticles in stereolithography-fabricated composite polymer scaffolds promotes bone repair

Fabrication of composite scaffolds using stereolithography (SLA) for bone tissue engineering has shown great promises. However, in order to trigger effective bone formation and implant integration, exogenous growth factors are commonly combined to scaffold materials. In this study, we fabricated biodegradable composite scaffolds using SLA and endowed them with osteopromotive properties in the absence of biologics. First we prepared photo-crosslinkable poly(trimethylene carbonate) (PTMC) resins containing 20 and 40wt% of hydroxyapatite (HA) nanoparticles and fabricated scaffolds with controlled macro-architecture. Then, we conducted experiments to investigate how the incorporation of HA in photo-crosslinked PTMC matrices improved human bone marrow stem cells osteogenic differentiation in vitro and kinetic of bone healing in vivo. We observed that bone regeneration was significantly improved using composite scaffolds containing as low as 20wt% of HA, along with difference in terms of osteogenesis and degree of implant osseointegration. Further investigations revealed that SLA process was responsible for the formation of a rich microscale layer of HA corralling scaffolds. To summarize, this work is of substantial importance as it shows how the fabrication of hierarchical biomaterials via surface-enrichment of functional HA nanoparticles in composite polymer stereolithographic structures could impact in vitro and in vivo osteogenesis.

STATEMENT OF SIGNIFICANCE

This study reports for the first time the enhance osteopromotion of composite biomaterials, with controlled macro-architecture and microscale distribution of hydroxyapatite particles, manufactured by stereolithography. In this process, the hydroxyapatite particles are not only embedded into an erodible polymer matrix, as reported so far in the literature, but concentrated at the surface of the structures. This leads to robust in vivo bone formation at low concentration of hydroxyapatite. The reported 3D self-corralling composite architecture provides significant opportunities to develop functional biomaterials for bone repair and tissue engineering.

Glycol chitosan/nanohydroxyapatite biocomposites for potential bone tissue engineering and regenerative medicine

In the last few decades, research on biocomposite nanomaterials has grown exponentially due to the global demand for novel solutions in bone tissue engineering and repair. In the present study, it is reported the design and synthesis of biocomposites based on glycol chitosan (GLY-CHI) matrices incorporated with nano-hydroxyapatite particles (nHA) produced via an eco-friendly chemical colloidal process in water media followed by solvent casting and evaporation methods at room temperature. The structure, morphology, and crystallinity of the components and biocomposites were extensively characterized by light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), wavelength dispersive X-ray fluorescence spectroscopy (WD-XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray micro-computed tomography analysis (μCT). Furthermore, cytotoxicity and cell viability tests were performed on three cell lines using a 3-(4,5-dimethylthiazol-2yl) 2,5-diphenyl tetrazolium bromide (MTT) assay, an alkaline phosphatase (ALP) activity test, and LIVE/DEAD^® assays. The results demonstrated that the GLY-CHI ligand played a major role in the nucleation, growth and colloidal stabilization of calcium phosphate particles at nanoscale dimensions with a narrow distribution and average size of 74±15nm. The FTIR spectroscopy associated with the XRD results indicated that nanosized hydroxyapatite (nHA) was the predominant calcium phosphate phase produced in the colloidal processing route. In addition, the X-ray micro-CT analysis of the nanocomposite membranes showed that nHA particles were homogenously dispersed in the glycol-chitosan polymeric matrix. Moreover, according to the in vitro bioassays, the biocomposites showed an adequate cell viability response and non-cytotoxic behavior toward osteoblastic-like (SAOS) and embryonic cell lines (HEK293T). Finally, the results of osteogenic differentiation tests demonstrated that the nHA/GLY-CHI composites are osteoinductive for human bone marrow mesenchymal stem cells (HBMS), which can be envisioned for prospective use in tissue engineering (e.g., bone, cartilage and periodontal) applications.

Cotransport of hydroxyapatite nanoparticles and hematite colloids in saturated porous media: Mechanistic insights from mathematical modeling and phosphate oxygen isotope fractionation

The fate and transport of individual type of engineered nanoparticles (ENPs) in porous media have been studied intensively and the corresponding mechanisms controlling ENPs transport and deposition are well-documented. However, investigations regarding the mobility of ENPs in the concurrent presence of another mobile colloidal phase such as naturally occurring colloids (colloid-mediated transport of ENPs) are largely lacking. Here, we investigated the cotransport and retention of engineered hydroxyapatite nanoparticles (HANPs) with naturally occurring hematite colloids in water-saturated sand columns under environmentally relevant transport conditions, i.e., pH, ionic strength (IS), and flow rate. Particularly, phosphate oxygen isotope fractionation of HANPs during cotransport was explored at various ISs and flow rates to examine the mechanisms controlling the isotope fractionation of HANPs in abiotic transport processes (physical transport). During cotransport, greater mobility of both HANPs and hematite occurred at higher pHs and flow rates, but at lower ISs. Intriguingly, the mobility of both HANPs and hematite was substantially lower during cotransport than the individual transport of either, attributed primarily to greater homo- and hetero-aggregation when both particles are copresent in the suspension. The shapes of breakthrough curves (BTCs) and retention profiles (RPs) during cotransport for both particles evolved from blocking to ripening with time and from flat to hyperexponential with depth, respectively, in response to decreases in pH and flow rate, and increases in IS. The blocking BTCs and RPs that are flat or hyperexponential can be well-approximated by a one-site kinetic attachment model. Conversely, a ripening model that incorporates attractive particle-particle interaction has to be employed to capture the ripening BTCs that are impacted by particle aggregation during cotransport. A small phosphate oxygen isotope fractionation (≤1.8‰) occurred among HANPs populations during cotransport responding to IS and flow rate changes. This fractionation is most likely a result of hetero-aggregation between hematite and HANPs that favors light phosphate isotopes (P(16)O4). This interpretation is further supported by the increase in isotope fractionation at higher ISs (i.e., greater aggregation). However, the fractionation was progressively erased by decreasing flow rate, ascribed to the reduced mass transfer of HANPs between the influent and effluent. Together our findings suggest that the cotransport and retention of HANPs and hematite colloids are highly sensitive to the considered physicochemical factors, and isotope tracing could serve as a promising tool to identify the sources and transport of phosphate-based NPs in complex subsurface environments due to insignificant transport-related isotope fractionation.

FEM modeling of the reinforcement mechanism of Hydroxyapatite in PLLA scaffolds produced by supercritical drying, for Tissue Engineering applications

Scaffolds have been produced by supercritical CO2 drying of Poly-L-Lactid Acid (PLLA) gels loaded with micrometric fructose particles used as porogens. These structures show a microporous architecture generated by the voids left in the solid material by porogen leaching, while they maintain the nanostructure of the gel, consisting of a network of nanofilaments. These scaffolds have also been loaded with Hydroxyapatite (HA) nanoparticles, from 10 to 50% w/w with respect to the polymer, to improve the mechanical properties of the PLLA structure. Based on miscroscopic and mechanical considerations, we propose a parametric Finite Element Method (FEM) model of PLLA-HA composites that describes the microporous structure as a close-packing of equal spheres and the nanoscale structure as a space frame of isotropic curved fibers. The effect of HA on the mechanical properties of the scaffolds has been modeled on the basis of SEM images and by taking into consideration the formation of concentric cylinders of HA nanoparticles around PLLA nanofibers. Modeling analysis confirms that mechanical properties of these scaffolds depend on nanofibrous network connections and that bending is the major factor causing deformation of the network. The FEM model also takes into account the formation of HA multi-layer coating on some areas in the nanofiber network and its increase in thickness with HA percentage. The Young modulus tends to a plateau for HA percentages larger than 30% w/w and when the coverage of the nanofibers produced by HA nanoparticles reaches a loaded surface index of 0.14 in the FEM model.

Effect of hydroxyapatite nanoparticles on osmotic responses of pig iliac endothelial cells

In order to fully explore the potential applications of nanoparticles in biopreservation, it is necessary to study the effect of nanoparticles on cell membrane permeabilities. The aim of this study is therefore to comparatively evaluate the osmotic responses of pig iliac endothelial cells in the absence and presence of commercially available hydroxyapatite nanoparticles. The results indicate that, after the introduction of 0.0 1 wt% hydroxyapatite nanoparticles, the dependence of cell membrane hydraulic conductivity (Lp) on temperature still obeys the Arrhenius relationship, while the reference value of the hydraulic conductivity of the cell membrane at 273.15K (Lpg) and the activation energy for water transport across cell membrane (ELp) change from 0.77 × 10(-14)m/Pa/s and 15.65 kJ/mol to 0.65 × 10(-14)m/Pa/s and 26.14 kJ/mol. That is to say, the reference value of the hydraulic conductivity of the cell membrane has been slightly decreased while the activation energy for water transport across cell membrane has been greatly enhanced, and thus it implies that the hydraulic conductivity of cell membrane are more sensitive to temperature in the presence of nanoparticles. These findings are of potential significance to the optimization of nanoparticles-aided cryopreservation.

The effect of particle agglomeration on the formation of a surface-connected compartment induced by hydroxyapatite nanoparticles in human monocyte-derived macrophages

Agglomeration dramatically affects many aspects of nanoparticle–cell interactions. Here we show that hydroxyapatite nanoparticles formed large agglomerates in biological medium resulting in extensive particle uptake and dose-dependent cytotoxicity in human macrophages. Particle citration and/or the addition of the dispersant Darvan 7 dramatically reduced mean agglomerate sizes, the amount of particle uptake and concomitantly cytotoxicity. More surprisingly, agglomeration governed the mode of particle uptake. Agglomerates were sequestered within an extensive, interconnected membrane labyrinth open to the extracellular space. In spite of not being truly intracellular, imaging studies suggest particle degradation occurred within this surface-connected compartment (SCC). Agglomerate dispersion prevented the SCC from forming, but did not completely inhibit nanoparticle uptake by other mechanisms. The results of this study could be relevant to understanding particle–cell interactions during developmental mineral deposition, in ectopic calcification in disease, and during application of hydroxyapatite nanoparticle vectors in biomedicine.

Effect of hydroxyapatite nanoparticles on the growth and p53/c-Myc protein expression of implanted hepatic VX2 tumor in rabbits by intravenous injection

AIM: To evaluate the effect of hydroxyapatite nano-particles (Nano HAP) by intravenous injection on the inhibition of implanted hepatic VX₂ tumor growth in rabbits and cell p53/c-Myc protein expression.

METHODS: 60 hepatic VX₂ tumor-bearing rabbits was randomly divided into five groups. Nano HAP collosol 20 mg/kg, 40 mg/kg, 5-FU solutions 20 mg/mL, mixed liquor of 5-FU solution 20 mg/mL and Nano HAP collosol 20 mg/kg were infused by vein, normal saline conducted as the control. The general state, weight, liver function and gross tumor volume were detected dynamically. The expression of p53 and c-Myc gene protein in tumor tissue was detected by immunohistochemistry methods.

RESULTS: The growth of implanted hepatic VX₂ tumors was significantly inhibited in all therapy groups, 3 wk after the injection, the tumor control rates in Nano HAP collosol groups were 25.5% and 32.5% respectively, and the gross tumor volumes were obviously less than that of control group. (24.81 ± 5.17 and 22.73 ± 4.23 vs 33.32 ± 5.26, P < 0.05). The tumor control rate of 5-FU group was 43.7% (18.74 ± 4.40 vs 33.32 ± 5.26, P < 0.05), but the general state of the animals after injection aggravated; and the adverse reaction in the drug combination group obviously decreased. Due to the effect of Nano HAP, the positive expression of tumor associated the mutated p53 and c-Myc in tumor tissue was decreased obviously compared with the control group.

CONCLUSION: Nano HAP has evident inhibitory action on rabbit implanted hepatic VX₂ tumor in vivo, which may be the result of decreasing the expression of the mutated p53 and c-myc, and drug combination can obviously decrease the adverse reaction of 5-FU.