Nanosilicate Platelets Research Articles

Laponite-Gelatin Nanofibrous Microsphere Promoting Human Dental Follicle Stem Cells Attachment and Osteogenic Differentiation for Noninvasive Stem Cell Transplantation.

Nanofibrous microspheres (NFM) are emerging as prominent next-generation biomimetic injectable scaffold system for stem cell delivery and different tissue regeneration where nanofibrous topography facilitates ECM-like stem cells niches. Addition of osteogenic bioactive nanosilicate platelets within NFM can provide osteoconductive cues to facilitate matrix mediated osteogenic differentiation of stem cells and enhance the efficiency of bone tissue regeneration. In this study, gelatin nanofibrous microspheres are prepared containing fluoride-doped laponite XL21 (LP) using the emulsion mediated thermal induce phase separation (TIPS) technique. Systematic studies are performed to understand the effect of physicochemical properties of biomimicking NFM alone and with different concentrations of LP on human dental follicle stem cells (hDFSCs), their cellular attachment, proliferation, and osteogenic differentiation. The study highlights the effect of LP nanosilicate with biomimicking nanofibrous injectable scaffold system aiding in enhancing stem cell differentiation under normal physiological conditions compared to NFM without LP. The laponite-NFM shows suitability as excellent injectable biomaterials system for stem cell attachment, proliferation and osteogenic differentiation for stem cell transplantation and bone tissue regeneration.

Biocompatibility and antimicrobial activity of copper(II) oxide hybridized with nano silicate platelets

Nano-sized copper(II) oxide (CuO) is an interesting material with proficient antibacterial activities but limited due to its toxicity to mammalian cells. In this study, CuO nano-sized needles were coated on the surface of nano-silicate platelets (NSP), which were exfoliated from natural montmorillonite clays and with the thickness of about 1 nm, to form nanohybrids. Our findings indicate that NSPs can effectively prevent the aggregation of CuO needles, and significantly enhance antibacterial efficiency without affecting biocompatibility. An optimal antibacterial activity against Staphylococcus aureus exceeding 99% could be obtained, while that for Escherichia coli was about 88%. Electron paramagnetic resonance results suggest that •OH radicals, one of the reactive oxygen species generated by CuO/NSP, might damage the cellular components and thus result in the death of bacterial.

Cytotoxicity Produced by Silicate Nanoplatelets: Study of Cell Death Mechanisms.

Nano-silicate platelets (NSP), an exfoliated product from natural clays, have been validated for biosafety and as an effective supplement to alleviate mycotoxicosis. Since NSP induced noticeable cell death, we therefore investigated further the mechanism of cytotoxicity caused by NSP. Exposure to NSP impaired membrane integrity and caused cell death in a dose-dependent manner. Reactive oxygen species (ROS) generation other than of NADH oxidase origin, and subcellular interactions by internalized NSP also contributed to NSP-induced cell death. NSP persistently provoked receptor-interacting protein 1 Ser/Thr (RIP1) kinase and caspase 6 and 3/7 activation without altering caspase 8 activity and induced evident chromatolysis of necrosis in the later stage. These events proceeded along with increased ER stress and mitochondrial permeability, to final Cyt-C (Cytochrome C) release and AIF (apoptosis inducing factor) translocation, a hallmark of cell necroptosis. Fluorescent probing further manifested NSP traffic, mostly adherence on the cell surfaces, or via internalization, being compartmentalized in the nuclei, cytosols, and mitochondria. Pharmacological approaches with specific inhibitors suggested that endocytosis and particularly RIP1 kinase provocation mediate NSP-induced cell death independent of caspase activation. In conclusion, the necroptotic process contributes to most of the cell death induced by NSP due to membrane interactions/impaired integrity, ROS generation, and subcellular interactions by internalized NSP.

Effect of Fluoride Doping in Laponite Nanoplatelets on Osteogenic Differentiation of Human Dental Follicle Stem Cells (hDFSCs)

Bioactive nanosilicates are emerging prominent next generation biomaterials due to their intrinsic functional properties such as advanced biochemical and biophysical cues. Recent studies show interesting dose-dependent effect of fluoride ions on the stem cells. Despite of interesting properties of fluoride ions as well as nanosilicate, there is no reported literature on the effect of fluoride-doped nanosilicates on stem cells. We have systematically evaluated the interaction of fluoride nanosilicate platelets (NS + F) with human dental follicle stem cells (hDFSCs) to probe the cytotoxicity, cellular transport (internalization) and osteogenic differentiation capabilities in comparison with already reported nanosilicate platelets without fluoride (NS − F). To understand the osteoinductive and osteoconductive properties of the nanosilicate system, nanosilicate treated hDFSCs are cultured in three different medium namely normal growth medium, osteoconductive medium, and osteoinductive medium up to 21 d. NS + F treated stem cells show higher ALP activity, osteopontin levels and significant alizarin red staining compared to NS − F treated cells. This study highlights that the particles having fluoride additives (NS + F) aid in enhancing the osteogenic differentiation capabilities of hDFSCs thus potential nanobiomaterial for periodontal bone tissue regeneration.

A Method to Prepare Magnetic Nanosilicate Platelets for Effective Removal of Microcystis aeruginosa and Microcystin-LR.

Algal toxin is a unique type of toxin generated with harmful algal blooms in water bodies. This phenomenon is worsened by eutrophication caused by excessive discharge of nutrients into surface water bodies. Since algal toxins are hard to remove after they enter the water treatment processes, an efficient method is required to inhibit the growth of algal cells, to settle the cells at the bottom of the water body and to removes the toxin from the water. We report an efficient way to prepare a novel nanohybrid material, i.e., magnetic nanosilicate platelet (MNSP), and its effects on the removal of microcystin toxins as well as the cells of Microcystis aeruginosa. MNSP was fabricated by a special treatment of a clay mineral, montmorillonite, and then its surface was decorated with magnetite nanoparticles by in situ synthesis. The nanohybrid can efficiently inhibit the growth of M. aeruginosa-a typical species that can generate one of the most notorious algal toxins, i.e., microcystins. Algal cells can be settled with minimal 500 ppm MNSP, and the turbidity can be reduced by more than 67%. The removal of microcystin-LR (MC-LR) was as high as 99.39% at an concentration of 100 ppm, while the pristine nanosilicate platelet could only remove 36.84% at the same dosage.

Interaction of novel fluorescent nanoscale ionic silicate platelets with biomaterials for biosensors.

The nano silicate platelets (NSPs) of 100 × 100 × 1 nm(3) in dimension were previously derived from the exfoliation of naturally occurring sodium montmorillonite clay, and their affinity to the surface of bacteria was revealed. The unique characteristics of ionic charges (≡Si-O-Na(+)) and the presence of siloxanol functionalities (≡Si-OH) allowed the organic modification of NSP to form NSP-tethering poly(hydroxyethyl methacrylate) (PHEMA) pendants through a sol-gel and living polymerization. By attaching nathphalimide-type fluorescence onto NSP-PHEMA, a new class of fluorescent organic-inorganic hybrid (NSP-PHEMA-HA), was prepared and its photoluminescence (PL) and bacterial trapping properties were characterized. The investigation of PL emission revealed that the fluorescent NSP hybrids could be used to detect bacteria and possess the potential for the biosensor applications.

Inhibition of fumonisin B1 cytotoxicity by nanosilicate platelets during mouse embryo development.

Nanosilicate platelets (NSP), the form of natural silicate clay that was exfoliated from montmorillonite (MMT), is widely used as a feed additive for its high non-specific binding capacity with mycotoxins such as fumonisin B1 (FB1), and has been evaluated its safety for biomedical use including cytotoxicity, genotoxicity, and lethal dosage (LD). In the study, we further examined its toxicity on the development of CD1 mouse embryos and its capacity to prevent teratogenesis-induced by FB1. In vitro cultures, NSP did not disturb the development and the quality of intact pre-implantation mouse embryos. Further, newborn mice from females consumed with NSP showed no abnormalities. NSP had an unexpected high adsorption capacity in vitro. In contrast to female mice consumed with FB1 only, a very low residual level of FB1 in the circulation, reduced incidence of neutral tube defects and significantly increased fetal weight were observed in the females consumed with FB1 and NSP, suggesting a high alleviation effect of NSP on FB1 in vivo. Furthermore, FB1 treatment disturbed the gene expression of sphingolipid metabolism enzymes (longevity assurance homolog 5, LASS 5; sphingosine kinase 1, Sphk1; sphingosine kinase 2, Sphk2; sphingosine 1- phosphate lyase, Sgpl1; sphingosine 1-phosphate phosphatase, Sgpp1) in the maternal liver, uterus, fetus, and placenta, but NSP administration reversed the perturbations. Based on these findings, we conclude that NSP is a feasible and effective agent for supplementary use in reducing the toxicity of FB1 to animals.

Effective removal of Microcystis aeruginosa and microcystin-LR using nanosilicate platelets

Drinking water safety has been threatened by increasing harmful algal blooms (HABs) in water sources. HABs are closely associated with eutrophication in freshwater lakes, e.g. Lake Tai in China, and marine environments as well, e.g. Baltic Sea in Europe. Among all HABs, Microcystis aeruginosa attracted much attention due to its easy proliferation and potent toxins, microcystins. Most of the current control technologies can result in immediate release of microcystins which are hard to remove by drinking water treatment processes. Here we propose to simultaneously remove M. aeruginosa and its toxin, microcystin-LR (MC-LR), using nanosilicate platelet (NSP) derived from natural clay mineral. In this study, NSP showed strong selective growth inhibition and good settling enhancing effects on M. aeruginosa and highly efficient removal of MC-LR. NSP can inhibit the growth of M. aeruginosa (initial cell concentration at 3.00×106cellmL−1) with a LC50 at 0.28ppm after 12h exposure. At the dosage of 100ppm, NSP can enhance settling of suspended M. aeruginosa. Bacterial growth inhibition tests showed NSP had very mild growth inhibition effects on Escherichia coli at high dosage but promoted the growth of Pseudomonas aeruginosa and Bacillus halodurans. For MC-LR removal, at an initial concentration of 100μgL−1, NSP achieved higher than 99% removal. Thus, the results suggest that NSP could be an excellent candidate for controlling M. aeruginosa-related HABs in water bodies.

Correction to Evaluation of the Antibacterial Activity and Biocompatibility for Silver Nanoparticles Immobilized on Nano Silicate Platelets

Correction to Evaluation of the Antibacterial Activity and Biocompatibility for Silver Nanoparticles Immobilized on Nano Silicate Platelets

Evaluation of the Antibacterial Activity and Biocompatibility for Silver Nanoparticles Immobilized on Nano Silicate Platelets

Silver nanoparticles (AgNPs) are known for their bactericidal abilities. The antibacterial potency is dependent on the particle size and dispersion status. In this study, we synthesized AgNP/NSP nanohybrids in two different weight ratios (1/99 and 8/92) using the fully exfoliated clay, i.e., nanosilicate platelets (NSP), as a dispersing agent and carrier for AgNPs. Due to the size of NSP, the immobilized AgNPs do not enter cells readily, which may lower the risk associated with the cellular uptake of AgNPs. The biocompatibility, immunological response, and antimicrobial activities of AgNP/NSP hybrids were evaluated. The results revealed that AgNP/NSP hybrids elicited merely mild inflammatory response and retained the outstanding antibacterial activity. The hybrids were further embedded in poly(ether)urethane (PEU) to increase the biocompatibility. At the same silver content (20 ppm), the PEU-AgNP/NSP nanocomposites were nontoxic to mouse skin fibroblasts, while simultaneously exhibiting nearly complete bacterial growth reduction (99.9%). PEU containing the same amount of free AgNPs did not display such an effect. Our results verify the better biosafety of the AgNPs/NSP hybrids and their polymer nanocomposites for further clinical use.

Amphiphilic silver-delaminated clay nanohybrids and their composites with polyurethane: physico-chemical and biological evaluations.

Silver nanoparticles (AgNPs) exhibit size-dependent bactericidal activity. They are, however, subject to aggregation when added to most hydrophobic polymers. In this study, a surfactant-modified delaminated clay (surfactant-capped nanosilicate platelets, or "NSQ") was employed to be a nanocarrier for AgNPs. The nanohybrid of AgNPs and NSQ ("AgNP/NSQ") in aqueous solution showed remarkable bactericidal effect as well as negligible cytotoxicity and immune response at a concentration of 10 ppm. Poly(carbonate)urethane (PCU) with different hard/soft segment ratios was synthesized and used in the preparation of the nanocomposites, PCU-AgNP/NSQ. Based on TEM observation, AgNP/NSQ was well dispersed in the resulting nanocomposites. The reinforcing effects of AgNP/NSQ in nanocomposites were distinct for PCU with different hard/soft segment ratios. The phase-separated structure of PCU-AgNP/NSQ nanocomposites was investigated by small-angle X-ray scattering (SAXS). PCU-AgNP/NSQ containing 75 ppm of Ag demonstrated superior microbiostatic effect, as well as better biodurability and lower foreign body reaction than the commercial Pellethane 2363-80A.

Characterization, Antimicrobial Activities, and Biocompatibility of Organically Modified Clays and Their Nanocomposites with Polyurethane

A novel method to exfoliate the montmorillonite clay was developed previously to generate random nanosilicate platelets (NSP), one kind of delaminated clay. To improve their dispersion in a polymer, we modified NSPs by three types of surfactants (cationic Qa, nonionic Qb, and anionic Qc) in this study and used them to prepare nanocomposites with polyurethane (PU). The zeta potential, antimicrobial ability, and biocompatibility of these surfactant-modified NSPs (abbreviated "NSQ") were characterized. It was found that the zeta potential of Qa-modified NSP (NSQa) was positive, whereas those of NSP and the other two NSQs (NSQb and NSQc) were negative. All NSQ presented less cytotoxicity than NSP. NSQa and NSQc showed excellent antimicrobial activities against S. aureus (Gram-positive strain) and E. coli (Gram-negative strain). The nanocomposites of NSQ with PU were then characterized for surface and mechanical properties, cell attachment and proliferation, antimicrobial activity in vitro, and biocompatibility in vivo. A higher surfactant to NSP ratio was found to improve the dispersion of NSQ in PU matrix. The mechanical properties of all PU/NSQ nanocomposites were significantly enhanced. Among various NSQ, only NSQa were observed to migrate to the composite surface. The attachment and proliferation of endothelial cells and fibroblasts in vitro as well as biocompatibility in vivo were significantly better for PU/NSQa containing 1% of NSQa than other materials. The microbiostasis ratios of PU/NSQ nanocomposites containing 1% NSQa or NSQc were >90%. These results proposed the safety and potential antimicrobial applications of surfactant-modified delaminated clays and their nanocomposites with PU polymer.

The biocompatibility and antimicrobial activity of nanocomposites from polyurethane and nano silicate platelets

Nanocomposites from a polyether-type waterborne polyurethane (PU) and 0.1 wt % of silicate materials were prepared. The individual silicate materials were natural clays (montmorillonite and mica), their exfoliated clays [nano silicate platelets (NSP) and nano mica platelets], and NSP modified with C18 fatty amine (NSP-S). The physico-chemcical properties and antimicrobial activity of the nanocomposites were characterized in vitro. The biostability and biocompatibility of the nanocomposites were evaluated in vivo. The nanocomposites exhibited various surface morphologies with phase separation of hard and soft domains in nanometric scales. The nanocomposite containing NSP (PU-NSP) showed better endothelial cell attachment and gene expression. The better biocompatibility of PU-NSP and PU-NSP-S was evidenced by the lower thickness of foreign body capsules in rat subcutaneous implantation. PU-NSP had the least surface degradation in vivo as demonstrated by the electron microscopy and infrared spectroscopy. This may be associated with the different surface structure. PU-NSP and PU-NSP-S showed strong bacteriostatic effects, which suggested that the nano clay in the polymer matrix may still interact with the microbes.

Evaluation on Cytotoxicity and Genotoxicity of the Exfoliated Silicate Nanoclay

The concern about toxicity for nanosilicate platelets (NSP) derived from natural montmorillonite clay is addressed. The NSP nanoclay was isolated from polyamine-salt exfoliation of the layered silicate clay into randomized individual plates, possessing multiple ionic charges on the surface of silicate plates with an average geometric dimension of ca. 80 x 80 x 1 nm(3). The material had been previously shown to be effective for antimicrobial and tendency for adhering onto the biomaterial surface based on the direct observation by using scanning electron microscope. The material safety on genotoxic effect was investigated by using three different test systems: the Comet assay test on Chinese Hamster Ovary (CHO) cells in vitro, micronucleus (MN) assay in vivo and the Salmonella gene mutation assay on strain TA98, TA100, TA102, TA1535 and TA1537. The Comet assay showed no DNA damage after 24 h of incubation with NSP of 1000 microg/mL. The MN test indicated no significant micronucleus induction in the CHO cells at the concentrations tested. With all five strains of Salmonella typhimurium, none of mutations was found. Furthermore, cytotoxicity of the same material was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release, showing a low cytotoxicity on CHO cells below 1000 microg/mL after 12 h incubation period and a dose-dependent effect after 24 h incubation. For feeding to rats, the acute oral toxicity was shown a low lethal dose (LD(50)) or greater than 5700 mg/kg body weight for both male and female Sprague-Dawley rats. Overall, the study has demonstrated the safety of the NSP for potential uses in biomedical areas.

Poly(N-isopropylacrylamide)-Tethered Silicate Platelets for Colloidal Dispersion of Conjugated Polymers with Thermoresponsive and Photoluminescence Properties

Poly(N-isopropylacrylamide)-tethered nanosilicate platelets (NSP-PNiPAAm) have been synthesized by covalently bonding the polymer onto the surfaces of silicate platelets of nanometer dimension, and this class of nanohybrids has proved to be effective for dispersing water-insoluble conjugated polymers (CPs). Simple pulverization of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with NSP-PNiPAAm rendered the powder material dispersible in water, whereupon it displayed thermoresponsive properties at 37.5 degrees C and CP particle size variation between ca. 50 and 100 nm by SEM observation. The same dispersion had a maximum UV-vis absorption at 524 nm and PL emission at 605 nm. The PL emission was significantly higher at 4 degrees C than at 45 degrees C. Being coated as a film, it showed an orange emission under an ultraviolet lamp, consistent with the PL measurement. The water-borne process of dispersing the CP in aqueous media by the presence of NSP-PNiPAAm and followed by film formation to demonstrate a unique method of manipulating hydrophobic conjugated polymers in a facile manner.

Thermoresponsive Dual-Phase Transition and 3D Self-Assembly of Poly(N-Isopropylacrylamide) Tethered to Silicate Platelets

Thermoresponsive poly(N-isopropylacrylamide) (PNiPAAm) was covalently tethered to nanosilicate platelets (NSP) to generate a new class of organic−inorganic hybrid that exhibits self-assembly and phase transformation properties under applied stimuli. Hybrids of two grafting densities were prepared and the PNiPAAm length was precisely controlled to yield a degree of polymerization of 350−1890 and a narrow molecular weight distribution (1.21−1.50 polydispersity or Mw/Mn). Two distinctive second-order transitions were observed during differential scanning calorimetry analysis, indicating the existence of dual-segment density zones. The difference between the two transition temperatures gradually vanished with increasing chain length, and a single endothermic first-order transition emerged. The hybrid also underwent a heat-induced phase transformation after treatment with several heating and cooling cycles. It is believed that fixation of PNiPAAm onto NSP greatly inhibited chain relaxation movements and hindered reversible coil−globule transitions. Furthermore, thermally induced self-assembly behavior was directly observed by transmission electronic microscopy of the hybrid coating as a thin film on a silicon wafer surface. The formation of a 3D network of nanostructures was directed by the platelet shape at temperatures higher than the critical solution temperature of the PNiPAAm chains. The temperature-controllable phase separation for formation of an ordered domain network of 100−500 nm in dimension has potential for the fabrication of new smart nanomaterials.

Enhancing the performance of dye-sensitized solar cells by incorporating nanosilicate platelets in gel electrolyte

Two kinds of gel-type dye-sensitized solar cells (DSSCs), composed of two types of electrolytes, were constructed and the respective cell performance was evaluated in this study. One electrolyte, TEOS-Triton X-100 gel, was based on a hybrid organic/inorganic gel electrolyte made by the sol–gel method and the other was based on poly(vinyidene fluoride-co-hexafluoro propylene) (PVDF-HFP) copolymer. TEOS-Triton X-100 gel was based on the reticulate structure of silica, formed by hydrolysis, and condensation of tetraethoxysilane (TEOS), while its organic subphase was a mixture of surfactant (Triton X-100) and ionic liquid electrolytes. Both DSSC gel-type electrolytes were composed of iodine, 1-propy-3-methyl-imidazolium iodide, and 3-methoxypropionitrile to create the redox couple of I 3 −/I −. Based on the results obtained from the I– V characteristics, it was found that the optimal iodine concentrations for the TEOS-Triton X-100 gel electrolyte and PVDF-HFP gel electrolyte are 0.05 M and 0.1 M, respectively. Although the increase in the iodine concentration could enhance the short-circuit current density ( J SC), a further increase in the iodine concentration would reduce the J SC due to increased dark current. Therefore, the concentration of I 2 is a significant factor in determining the performance of DSSCs. In order to enhance cell performance, the addition of nanosilicate platelets (NSPs) in the above-mentioned gel electrolytes was investigated. By incorporating NSP-Triton X-100 into the electrolytes, the J SC of the cells increased due to the decrease of diffusion resistance, while the open circuit voltage ( V OC) remained almost the same. As the loading of the NSP-Triton X-100 in the TEOS-Triton X-100 gel electrolyte increased to 0.5 wt%, the J SC and the conversion efficiency increased from 8.5 to 12 mA/cm 2 and from 3.6% to 4.7%, respectively. However, the J SC decreased as the loading of NSP-Triton X-100 exceeded 0.5 wt%. At higher NSP-Triton X-100 loading, NSPs acted as a barrier interface between the electrolyte and the dye molecules, hindering electron transfer, hence, reducing the cell's photocurrent density. The same behavior was also observed in the PVDF-HFP gel electrolyte DSSC system.

UV-curing and characterization of polymer–clay nanocoatings by dispersion of acrylate-funtionalized organoclays

Nanocoatings have been prepared by dispersing two different surfmer-modified nanosilicate platelets into acrylic resins. UV-induced polymerization gave rise to highly crosslinked networks. The UV-curing kinetics was not affected by the presence of the nanofiller. XRD and TEM investigations showed that, during the dispersion of the organoclays in the UV-curable resins, the surfmer treatment promotes an important lamellae intercalation which is maintained after UV curing. An increase of the T g values and of the thermal stability was achieved in the samples containing 5 wt% of modified clay.

Mesoscopic structure of dry-pressed clay samples from small-angle X-ray scattering measurements

Weakly hydrated samples of platelet-shaped nano-particles obtained by dry-pressing suspensions of the synthetic Na fluorohectorite clay are studied. The particles consist of stacks of several tens of 1 nm-thick nanosilicate platelets. They form a compound of quasi-two-dimensional particles whose average director is aligned with the direction of the uniaxial stress applied at dehydration. Small-angle X-ray scattering images from these samples are either isotropic or anisotropic, depending on the sample orientation with respect to the X-ray beam. From anisotropic images, changes in the scattering objects' orientation distribution probability (ODP) function are investigated as the temperature is lowered, thus triggering swelling of the individual particles by water intercalation. This is done, on the one hand, by inferring the width of the ODP function from the eccentricity of quasi-elliptic iso-intensity cuts of the small-angle scattering images, and, on the other hand, by obtaining the ODP function from azimuthal profiles of the images. The decays of the scattering intensity as a function of momentum transfer along the two principal directions of the images exhibit power law behaviors. A crossover scale between two power law regimes is observed on the profiles recorded along the horizontal axis; it corresponds to the typical pore size along the direction of the initially applied load. These results are compared with a previous study of similar systems.