Bioactive silica nanoparticles target autophagy, NF-κB, and MAPK pathways to inhibit osteoclastogenesis.

Spherical 50 nm silica-based nanoparticles (SiNPs) promote healthy bone homeostasis and maintenance by supporting bone forming osteoblast lineage cells while simultaneously inhibiting the differentiation of bone resorbing osteoclasts. Previous work demonstrated that an intraperitoneal injection of SiNPs in healthy mice - both young and old - increased bone density and quality, suggesting the possibility that SiNPs represent a dual action therapeutic. However, the underlying mechanisms governing the osteoclast response to SiNPs have yet to be fully explored and defined. Therefore, the goals of this study were to investigate the cellular and molecular mechanisms by which SiNPs inhibit osteoclastogenesis. SiNPs strongly inhibited RANKL-induced osteoclast differentiation within the first hours and concomitantly inhibited early transcriptional regulators such as Nfatc1. SiNPs simultaneously stimulated expression of autophagy related genes p62 and LC3ß dependent on ERK1/2 signaling pathway. Intriguingly, SiNPs were found to stimulate autophagosome formation while inhibiting the autophagic flux necessary for RANKL-stimulated osteoclast differentiation, resulting in the inhibition of both the canonical and non-canonical NF-κB signaling pathways and stabilizing TRAF3. These results suggest a model in which SiNPs inhibit osteoclastogenesis by inhibiting the autophagic machinery and RANKL-dependent functionality. This mechanism of action defines a novel therapeutic strategy for inhibiting osteoclastogenesis.

Synergistic Effects of Pulsed Focused Ultrasound and a Doxorubicin-Loaded Microparticle-Microbubble Complex in a Pancreatic Cancer Xenograft Mouse Model.

The synergistic effects of a doxorubicin (Dox)-loaded microparticle-microbubble complex (DMMC) and focused ultrasound (FUS) with a short duty cycle (5%) were evaluated in a pancreatic cancer xenograft model established by inoculating immunodeficient mice with CFPAC-1 cells. The efficacy of the DMMC with FUS (study 1), the effect of conjugating the particles as opposed to mixing them (study 2) and the levels of tumor apoptosis and intracellular Dox (study 3) were evaluated. The DMMC with FUS exhibited the lowest tumor growth rate (30.8 mm3/wk) and the highest intracellular Dox uptake (8.8%) and tumor cell apoptosis rate (58.7%) among all treatments. DMMC had a significantly lower growth rate than the mixture of Dox-loaded microparticles and microbubbles (44.2 mm3/wk, p < 0.01) when they were combined with FUS. In conclusion, DMMC with short-duty-cycle FUS holds promise for tumor growth suppression, which may be attributed to high intracellular Dox uptake.

Evaluation of lymph node metastasis in a rabbit tumor model: correlations between contrast-enhanced ultrasound and pathologic findings.

PURPOSE: The purpose of this study was to evaluate the ability of contrast-enhanced ultrasonography (CEUS) with microbubbles to detect metastatic lymph nodes (LNs) for treatment planning and prognosis. METHODS: For the metastatic LN model, ground VX2 tumor tissues were injected subcutaneously in 12 rabbits, just below the right hind limb. The rabbits were classified into three groups based on the LN area: group A (n=4, >1.9 cm2 ), group B (n=4, 1-1.9 cm2 ), and group C (n=4, <1 cm2 ). The LNs were monitored on CEUS for 10 seconds after injecting 2.5 mL of microbubbles. The percent area of metastatic LNs was calculated on pathologic images and compared with CEUS images. RESULTS: In group A, the mean percent area of metastasis was 40.7%±19.4%. In all cases of metastasis, round-shaped perfusion defects were clearly observed in CEUS images. The metastatic areas were strongly correlated with pathologic findings. The mean percent area in group B was 21.5%±14.4%. The CEUS findings showed multiple nodular perfusion defects, clearly revealing the metastatic areas. In group B, the CEUS and pathologic findings were concordant for three of the four cases. The mean percent area in group C was 9.1%±6.4%. However, in this group, CEUS only detected a small perfusion defect in one case. CONCLUSION: CEUS has the potential to depict characteristic imaging features of metastatic LNs but still has limitations in early detection.

Ultrasound-sensitizing nanoparticle complex for overcoming the blood-brain barrier: an effective drug delivery system.

Background: Crossing the blood-brain barrier (BBB) is crucial for drug delivery to the brain and for treatment of brain tumors, such as glioblastoma, the most common of all primary malignant brain tumors. Microbubble (MB) is oscillated and destroyed by controlling ultrasound (US) parameters. This oscillation and destruction of MB can open the BBB transiently, and a drug can be delivered to the brain. Materials and methods: For testing the efficiency of delivery to the brain, we synthesized a US-sensitizing nanoparticle (NP) complex via chemically binding MBs and NPs for the BBB opening, including near-infrared dye-incorporated albumin nanoparticles (NIR-Alb NPs) for fluorescence detection. Results: The human-derived, biocompatible NIR-Alb NPs did not show significant cytotoxicity to 500 µg/mL for 3 days in four human glioma cell lines. In an in vivo animal study, some US parameters were investigated to determine optimal conditions. The optimized US conditions were applied in a U87MG orthotopic mouse model. We found that the fluorescence intensity in the brain was 1.5 times higher than in the control group. Conclusion: Our US-sensitizing NP complex and US technique could become one of the critical technologies for drug delivery to the brain.

Antitumor Effects of Intra-Arterial Delivery of Albumin-Doxorubicin Nanoparticle Conjugated Microbubbles Combined with Ultrasound-Targeted Microbubble Activation on VX2 Rabbit Liver Tumors.

Image-guided intra-arterial therapies play a key role in the management of hepatic malignancies. However, limited clinical outcomes suggest the need for new multifunctional drug delivery systems to enhance local drug concentration while reducing systemic adverse reactions. Therefore, we developed the albumin-doxorubicin nanoparticle conjugated microbubble (ADMB) to enhance therapeutic efficiency by sonoporation under exposure to ultrasound. ADMB demonstrated a size distribution of 2.33 ± 1.34 µm and a doxorubicin loading efficiency of 82.7%. The echogenicity of ADMBs was sufficiently generated in the 2-9 MHz frequency range and cavitation depended on the strength of the irradiating ultrasound. In the VX2 rabbit tumor model, ADMB enhanced the therapeutic efficiency under ultrasound exposure, compared to free doxorubicin. The intra-arterial administration of ADMBs sufficiently reduced tumor growth by five times, compared to the control group. Changes in the ADC values and viable tumor fraction supported the fact that the antitumor effect of ADMBs were enhanced by evidence of necrosis ratio (over 70%) and survival tumor cell fraction (20%). Liver toxicity was comparable to that of conventional therapies. In conclusion, this study shows that tumor suppression can be sufficiently maximized by combining ultrasound exposure with intra-arterial ADMB administration.

An ultrasound-responsive dual-modal US/T1 -MRI contrast agent for potential diagnosis of prostate cancer.

BACKGROUND: Interest in an ultrasound-mediated delivery system for effective T1 -MRI of prostate cancer without adverse effects has steadily increased. PURPOSE: To develop an ultrasound-responsive dual-modal ultrasound (US)/T1 -MRI contrast agent for efficient diagnosis of prostate cancer cells overexpressing prostate-specific membrane antigen (PSMA) and assess their potential. STUDY TYPE: In vitro. SUBJECTS: Two prostate cancer cell lines. FIELD STRENGTH/SEQUENCE: Each study group underwent 3.0T MRI under a TR 400 msec, TE 10 msec, a 240 × 240 matrix, a flip angle 90°, a slice thickness 3 mm, NSA with 4, bandwidth 115 Hz/pixel, and an FOV of 120 × 120 mm. ASSESSMENT: Microscopes, quantitative and qualitative analyzing instruments, and clinical devices were used for assessing this novel contrast agent and its diagnosis effects. STATISTICAL TESTS: We used linear regression analyses to determine the longitudinal relaxivity (r1 ) values of our US/T1 -MRI contrast agent and gadobutrol. RESULTS: Microbubble+Fe3+ melanin nanoparticle+peptides (MB+Fe3+ MNPPs) had a good US contrast effect, like a commercial US agent. The differences of US intensities between them was below 5%. The r1 values of MB+Fe3+ MNPPs and gadobutrol were 4.5 and 3.7 s-1 /mM, respectively. More than hundreds of Fe3+ MNPPs were located in prostate cancer cells treated with MB+Fe3+ MNPPs and US stimulus, but the number of Fe3+ MNPPs was below dozens in the other prostate cancer cells expressing less PSMA. The former cells with MB+Fe3+ MNPPs and US stimulus only showed the highest T1 -MRI signal because of synergy effects of the peptides targeting the cells and US stimulus for delivery of Fe3+ MNPPs to the cells. No cytotoxicity of MB+Fe3+ MNPPs was confirmed by using a WST assay. Viability of the cells with the complexes was above 90%. DATA CONCLUSION: We synthesized MB+Fe3+ MNPPs as a potential US/T1 -MRI contrast agent. This complex was applicable for diagnosing desired prostate cancer cells. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1610-1616.

Bioactive effects of silica nanoparticles on bone cells are size, surface, and composition dependent.

Silica based nanoparticles have been demonstrated to have intrinsic biologic activity towards the skeleton and to function by promoting the differentiation of bone forming osteoblasts while inhibiting the differentiation of bone resorbing osteoclasts. The excitement surrounding nanomedicine in part revolves around the almost unlimited possibilities for varying the physicochemical properties including size, composition, and surface charge. To date few studies have attempted to manipulate these characteristics in concert to optimize a complex biologic outcome. Towards this end, spherical silica nanoparticles of various sizes (50-450 nm), of different surface properties (OH, CO2H, NR4+, mNH2), and of different composition (silica, gold, and polystyrene) were synthesized and evaluated for biological activity toward skeletal cells. Osteoblast activity was most influenced by composition and size variables, whereas osteoclasts were most affected by surface property variation. The study also establishes nanoparticle mediated suppression of Nfatc1, a key transcriptional regulator for osteoclast differentiation, identifying a novel mechanism of action. Collectively, the study highlights how during the design of bioactive nanoparticles, it is vital to consider not only the myriad of physical properties that can be manipulated, but also that the characteristics of the target cell plays an equally integral role in determining biological outcome. STATEMENT OF SIGNIFICANCE: Silica nanomaterials represent a promising biomaterial for beneficial effects on bone mass and quality as well as regenerative tissue engineering and are currently being investigated for intrinsic bioactivity towards the primary cells responsible for skeletal homeostasis; osteoblasts and osteoclasts. The goal of the current study was to assess the physical properties of silica nanoparticles that impart intrinsic bioactivity by evaluating size, surface charge, and composition. Results reveal differential influences of the physical properties of nanoparticles towards osteoblasts and osteoclasts. This study provides new insights into the design of nanoparticles to specifically target different aspects of bone metabolism and highlights the opportunities provided by nanotechnology to modulate a range of cell specific biological responses for therapeutic benefit.

Synthesis of pH stable, blue light-emitting diode-excited, fluorescent silica nanoparticles and effects on cell behavior.

To date, delivery of light-emitting diode (LED)-activated compounds to cells and tissue remains a challenge. Silica-based materials possess good biocompatibility and have advantages of control of size and shape. Fluorescent silica nanoparticles (NPs) have been synthesized and used for applications such as cell tracking and tumor identification. Here, we report the synthesis and optimization of fluorescent silica NPs, which incorporate a naphthalimide dye with triethoxysilanes that are excited by the blue LED wavelength (LEDex NPs). The NPs can be imaged in the 420-470 nm wavelength, demonstrate a high quantum yield, are stable in a range of pH, and are taken into the cells. Therefore, these NPs represent a novel imaging technology for biomedical applications.

Ions doped melanin nanoparticle as a multiple imaging agent.

BACKGROUND: Multimodal nanomaterials are useful for providing enhanced diagnostic information simultaneously for a variety of in vivo imaging methods. According to our research findings, these multimodal nanomaterials offer promising applications for cancer therapy. RESULTS: Melanin nanoparticles can be used as a platform imaging material and they can be simply produced by complexation with various imaging active ions. They are capable of specifically targeting epidermal growth factor receptor (EGFR)-expressing cancer cells by being anchored with a specific antibody. Ion-doped melanin nanoparticles were found to have high bioavailability with long-term stability in solution, without any cytotoxicity in both in vitro and in vivo systems. CONCLUSION: By combining different imaging modalities with melanin particles, we can use the complexes to obtain faster diagnoses by computed tomography deep-body imaging and greater detailed pathological diagnostic information by magnetic resonance imaging. The ion-doped melanin nanoparticles also have applications for radio-diagnostic treatment and radio imaging-guided surgery, warranting further proof of concept experimental.

Nano-Hydroxyapatite Stimulation of Gene Expression Requires Fgf Receptor, Phosphate Transporter, and Erk1/2 Signaling.

Hydroxyapatite (HAp) is critical to health both as the main structural material of the skeleton and storage material of calcium and phosphate. Nanosized HAp (nHAp) is naturally produced by mineralizing cells during bone formation and remodeling and is the main constituent of the skeleton. As such, HAp is currently being investigated as a therapeutic biomaterial for orthopedic and dental purposes. Recent studies have suggested that extracellular nHAp can influence osteoblast lineage commitment and cell function through changes in gene expression; however, the mechanisms remain to be elucidated. Here, the cellular and molecular mechanism by which rod-shaped nHAp (10 × 100 nm) stimulates gene expression in preosteoblast bone marrow stromal cells was investigated. Electron microscopy detected a rapid and stable interaction of nHAp with the cell membrane, which correlated with a strong stimulation of the Erk1/2 signaling pathway. Results also identified the requirement of the Fgf receptor signaling and phosphate-transporters for nHAp regulated gene expression whereas a calcium-sensing receptor inhibitor had no effect. Collectively, the study uncovers novel signaling pathways and cellular events specifically stimulated by and required for the cellular response to free extracellular HAp. The results provide insight into the osteoblastic response to HAp relevant to functional mineralization and pathological calcification and could be used in the development of biomaterials for orthopedic purposes.

Impact of Phosphorus-Based Food Additives on Bone and Mineral Metabolism.

CONTEXT: Phosphorus-based food additives can substantially increase total phosphorus intake per day, but the effect of these additives on endocrine factors regulating bone and mineral metabolism is unclear. OBJECTIVE: This study aimed to examine the effect of phosphorus additives on markers of bone and mineral metabolism. Design and Setting, and Participants: This was a feeding study of 10 healthy individuals fed a diet providing ∼1000 mg of phosphorus/d using foods known to be free of phosphorus additives for 1 week (low-additive diet), immediately followed by a diet containing identical food items; however, the foods contained phosphorus additives (additive-enhanced diet). Parallel studies were conducted in animals fed low- (0.2%) and high- (1.8%) phosphorus diets for 5 or 15 weeks. MAIN OUTCOME MEASURES: The changes in markers of mineral metabolism after each diet period were measured. RESULTS: Participants were 32 ± 8 years old, 30% male, and 70% black. The measured phosphorus content of the additive-enhanced diet was 606 ± 125 mg higher than the low-additive diet (P < .001). After 1 week of the low-additive diet, consuming the additive-enhanced diet for 1 week significantly increased circulating fibroblast growth factor 23 (FGF23), osteopontin, and osteocalcin concentrations by 23, 10, and 11%, respectively, and decreased mean sclerostin concentrations (P < .05 for all). Similarly, high-phosphorus diets in mice significantly increased blood FGF23, osteopontin and osteocalcin, lowered sclerostin, and decreased bone mineral density (P < .05 for all). CONCLUSIONS: The enhanced phosphorus content of processed foods can disturb bone and mineral metabolism in humans. The results of the animal studies suggest that this may compromise bone health.

Nano-hydroxyapatite modulates osteoblast lineage commitment by stimulation of DNA methylation and regulation of gene expression.

Hydroxyapatite (HA) is the primary structural component of the skeleton and dentition. Under biological conditions, HA does not occur spontaneously and therefore must be actively synthesized by mineralizing cells such as osteoblasts. The mechanism(s) by which HA is actively synthesized by cells and deposited to create a mineralized matrix are not fully understood and the consequences of mineralization on cell function are even less well understood. HA can be chemically synthesized (HAp) and is therefore currently being investigated as a promising therapeutic biomaterial for use as a functional scaffold and implant coating for skeletal repair and dental applications. Here we investigated the biological effects of nano-HAp (10 × 100 nm) on the lineage commitment and differentiation of bone forming osteoblasts. Exposure of early stage differentiating osteoblasts resulted in dramatic and sustained changes in gene expression, both increased and decreased, whereas later stage osteoblasts were much less responsive. Analysis of the promoter region one of the most responsive genes, alkaline phosphatase, identified the stimulation of DNA methylation following cell exposure to nano-HAp. Collectively, the results reveal the novel epigenetic regulation of cell function by nano-HAp which has significant implication on lineage determination as well as identifying a novel potential therapeutic use of nanomaterials.

Bioactive silica nanoparticles reverse age-associated bone loss in mice.

We recently reported that in vitro, engineered 50nm spherical silica nanoparticles promote the differentiation and activity of bone building osteoblasts but suppress bone-resorbing osteoclasts. Furthermore, these nanoparticles promote bone accretion in young mice in vivo. We have now investigated the capacity of these nanoparticles to reverse bone loss in aged mice, a model of human senile osteoporosis. Aged mice received nanoparticles weekly and bone mineral density (BMD), bone structure, and bone turnover were quantified. Our data revealed a significant increase in BMD, bone volume, and biochemical markers of bone formation. Biochemical and histological examinations failed to identify any abnormalities caused by nanoparticle administration. Our studies demonstrate that silica nanoparticles effectively blunt and reverse age-associated bone loss in mice by a mechanism involving promotion of bone formation. The data suggest that osteogenic silica nanoparticles may be a safe and effective therapeutic for counteracting age-associated bone loss. FROM THE CLINICAL EDITOR: Osteoporosis poses a significant problem in the society. Based on their previous in-vitro findings, the authors' group investigated the effects of spherical silica nanoparticles in reversing bone loss in a mouse model of osteoporosis. The results showed that intra-peritoneal injections of silica nanoparticles could increase bone mineral density, with little observed toxic side effects. This novel method may prove important in future therapy for combating osteoporosis.

Inorganic phosphate induces cancer cell mediated angiogenesis dependent on forkhead box protein C2 (FOXC2) regulated osteopontin expression.

Recent studies in both rodents and humans suggest that elevated serum phosphorus, in the context of normal renal function, potentiates, or exacerbates pathologies associates with cardiovascular disease, bone metabolism, and cancer. Our recent microarray studies identified the potent stimulation of pro-angiogenic genes such as forkhead box protein C2 (FOXC2), osteopontin, and Vegfα, among others in response to elevated inorganic phosphate (Pi). Increased angiogenesis and neovascularization are important events in tumor growth and the progression to malignancy and FOXC2 has recently been identified as a potential transcriptional regulator of these processes. In this study we addressed the possibility that a high Pi environment would increase the angiogenic potential of cancer cells through a mechanism requiring FOXC2. Our studies utilized lung and breast cancer cell lines in combination with the human umbilical vascular endothelial cell (HUVEC) vessel formation model to better understand the mechanism(s) by which a high Pi environment might alter cancer progression. Exposure of cancer cells to elevated Pi stimulated expression of FOXC2 and conditioned medium from the Pi-stimulated cancer cells stimulated migration and tube formation in the HUVEC model. Mechanistically, we define the requirement of FOXC2 for Pi-induced osteopontin (OPN) expression and secretion from cancer cells as necessary for the angiogenic response. These studies reveal for the first time that cancer cells grown in a high Pi environment promote migration of endothelial cells and tube formation and in so doing identify a novel potential therapeutic target to reduce tumor progression.

Bioactive silica nanoparticles promote osteoblast differentiation through stimulation of autophagy and direct association with LC3 and p62.

We recently identified an engineered bioactive silica-based nanoparticle formulation (designated herein as NP1) that stimulates in vitro differentiation and mineralization of osteoblasts, the cells responsible for bone formation, and increases bone mineral density in young mice in vivo. The results demonstrate that these nanoparticles have intrinsic biological activity; however, the intracellular fate and a complete understanding of the mechanism(s) involved remains to be elucidated. Here we investigated the cellular mechanism(s) by which NP1 stimulates differentiation and mineralization of osteoblasts. We show that NP1 enters the cells through a caveolae-mediated endocytosis followed by stimulation of the mitogen activated protein kinase ERK1/2 (p44/p42). Our findings further revealed that NP1 stimulates autophagy including the processing of LC3ß-I to LC3ß-II, a key protein involved in autophagosome formation, which is dependent on ERK1/2 signaling. Using a variant of NP1 with cobalt ferrite magnetic metal core (NP1-MNP) to pull down associated proteins, we found direct binding of LC3ß and p62, two key proteins involved in autophagosome formation, with silica nanoparticles. Interestingly, NP1 specifically interacts with the active and autophagosome associated form of LC3ß (LC3ß-II). Taken together, the stimulation of autophagy and associated signaling suggests a cellular mechanism for the stimulatory effects of silica nanoparticles on osteoblast differentiation and mineralization.

Bio-active engineered 50 nm silica nanoparticles with bone anabolic activity: therapeutic index, effective concentration, and cytotoxicity profile in vitro.

Silica-based nanomaterials are generally considered to be excellent candidates for therapeutic applications particularly related to skeletal metabolism however the current data surrounding the safety of silica based nanomaterials is conflicting. This may be due to differences in size, shape, incorporation of composite materials, surface properties, as well as the presence of contaminants following synthesis. In this study we performed extensive in vitro safety profiling of ∼ 50 nm spherical silica nanoparticles with OH-terminated or Polyethylene Glycol decorated surface, with and without a magnetic core, and synthesized by the Stöber method. Nineteen different cell lines representing all major organ types were used to investigate an in vitro lethal concentration (LC) and results revealed little toxicity in any cell type analyzed. To calculate an in vitro therapeutic index we quantified the effective concentration at 50% response (EC50) for nanoparticle-stimulated mineral deposition activity using primary bone marrow stromal cells (BMSCs). The EC50 for BMSCs was not substantially altered by surface or magnetic core. The calculated Inhibitory concentration 50% (IC50) for pre-osteoclasts was similar to the osteoblastic cells. These results demonstrate the pharmacological potential of certain silica-based nanomaterial formulations for use in treating bone diseases based on a favorable in vitro therapeutic index.

LONG-TERM MONITORING OF THE PHYSICOCHEMICAL PROPERTIES OF SILICA-BASED NANOPARTICLES ON THE RATE OF ENDOCYTOSIS AND EXOCYTOSIS AND CONSEQUENCES OF CELL DIVISION.

Nanomaterials are diverse in size, shape and charge and these differences likely alter their physicochemical properties in biological systems. We have investigated how these properties alter the initial and long-term dynamics of endocytosis, cell viability, cell division, exocytosis, and interaction with a collagen extracellular matrix using silica-based fluorescent nanoparticles and the murine pre-osteoblast cell line, MC3T3-E1. Three surface modified nanoparticles were analyzed: positively charged (PTMA), negatively charged (OH), and neutrally charged polyethylene glycol (PEG). Positively charged PTMA-modified nanoparticles demonstrated the most rapid uptake, within 2 hours, while PEG modified and negatively charged OH nanoparticles demonstrated slower uptake. Cell viability was >80% irrespective of nanoparticle surface charge suggesting a general lack of toxicity. Long-term monitoring of fluorescent intensity revealed that nanoparticles were passed to daughter cells during mitotic cell division with a corresponding decrease in fluorescent intensity. These data suggest that irrespective of surface charge silica nanoparticles have the potential to internalize into osteoblasts, albeit with different kinetics. Furthermore, long lived nanoparticles have the potential to be transferred to daughter cells during mitosis and can be maintained for weeks intracellularly or within a collagen matrix without toxicity and limited exocytosis.

Zinc oxide nanoparticle induced autophagic cell death and mitochondrial damage via reactive oxygen species generation.

Zinc oxide nanoparticles (ZnO-np) are used in an increasing number of industrial products such as paint, coating and cosmetics, and in other biological applications. There have been many suggestions of a ZnO-np toxicity paradigm but the underlying molecular mechanisms about the toxicity of ZnO-np remain unclear. This study was done to determine the potential toxicity of ZnO-np and to assess the toxicity mechanism in normal skin cells. Synthesized ZnO-np generated reactive oxygen species (ROS), as determined by electron spin resonance. After uptake into cells, ZnO-np induced ROS in a concentration- and time-dependent manner. To demonstrate ZnO-np toxicity mechanism related to ROS, we detected abnormal autophagic vacuoles accumulation and mitochondria dysfunction after ZnO-np treatment. Furthermore mitochondria membrane potential and adenosine-5'-triphosphate (ATP) production are decreased for culture with ZnO-np. We conclude that ZnO-np leads to cell death through autophagic vacuole accumulation and mitochondria damage in normal skin cells via ROS induction. Accordingly, ZnO-np may cause toxicity and the results highlight and need for careful regulation of ZnO-np production and use.

Bioactive silica-based nanoparticles stimulate bone-forming osteoblasts, suppress bone-resorbing osteoclasts, and enhance bone mineral density in vivo.

Bone is a dynamic tissue that undergoes renewal throughout life in a process whereby osteoclasts resorb worn bone and osteoblasts synthesize new bone. Imbalances in bone turnover lead to bone loss and development of osteoporosis and ultimately fracture, a debilitating condition with high morbidity and mortality. Silica is a ubiquitous biocontaminant that is considered to have high biocompatibility. The authors report that silica nanoparticles (NPs) mediate potent inhibitory effects on osteoclasts and stimulatory effects on osteoblasts in vitro. The mechanism of bioactivity is a consequence of an intrinsic capacity to antagonize activation of NF-κB, a signal transduction pathway required for osteoclastic bone resorption but inhibitory to osteoblastic bone formation. We further demonstrate that silica NPs promote a significant enhancement of bone mineral density (BMD) in mice in vivo, providing a proof of principle for the potential application of silica NPs as a pharmacological agent to enhance BMD and protect against bone fracture.

Effect of fluorescent silica nanoparticles in embryo and larva of Oryzias latipes: sonic effect in nanoparticle dispersion.

We characterized fluorescent silica nanoparticles (FNPs), which had been applied in many biological systems, in fish embryo rearing media (ERM) solution and evaluated the potential toxicity to the early development of Oryzias latipes embryos. Distribution of FNPs in embryos and larvae of O. latipes was studied by fluorescent and confocal laser scanning microscopic studies. Embryos exposed to three different concentrations of FNPs in stirred or sonicated ERM solutions were observed up to 2d after hatching. FNPs had a negligible effect on the hatchability of O. latipes embryos; however, compared to controls, more than 30% of eggs were abnormal in 10 and 50 mg FN P L(-1) solutions. We found that the toxic effect was increased in sonicated FNP solution, which seems to be related with the dissolution of FNPs in ERM solutions that could be accelerated by sonication. Further study found that the CaCl2 included in ERM solution might enhance the dissolution of the FNPs and the silicate ion released from FNPs partially contributed to larval toxicity. This study showed that some nanoparticles may not be stable in biological fluids even if they are stable in water. Dissolution factors such as sonication and cellular components should be considered in biological application of nanoparticles.