Antibacterial and cytotoxic effects of photoexcited Au clusters via blue high-power or white low-power light emitting diode irradiation

The development of photosensitizers and light sources has enabled the use of antimicrobial photodynamic therapy (aPDT) in various dental therapies. In the present study, we compared the antibacterial and cytotoxic effects of Au clusters photoexcited by blue and white LED irradiation. We fabricated novel photosensitizers, captopril-protected gold (Capt-Au) clusters and lysozyme-stabilized gold (Lyz-Au) clusters, for aPDT. Au clusters were then photoexcited by two kinds of light sources, blue high-power and white low-power light-emitting diodes (LEDs). Since white LED contains a wide spectrum of light (400–750 nm), white LED would be relevant for aPDT even if using a low-power source. The turbidity and viability of Streptococcus mutans were assessed following application of Capt-Au clusters (500 μg/mL) or Lyz-Au clusters (1,000 μg/mL) photoexcited by a blue high-power LED (1,000 mW/cm2) or white low-power LED (80 mW/cm2). In addition, the cytotoxicity of Au clusters and LED irradiation was evaluated in NIH3T3 and MC3T3-E1 cells. Au clusters photoexcited by the white low-power LED equally decreased the turbidity and viability of S. mutans compared with blue high-power LED. However, Au clusters photoexcited by white LED irradiation caused decreased cytotoxicity in mammalian cells compared with those photoexcited by blue LED irradiation. In conclusion, white LEDs possess biosafe properties for aPDT using Au clusters

Prognostic Impact of Baseline Hemoglobin Levels on Long-Term Thrombotic and Bleeding Events After Percutaneous Coronary Interventions

Background: Association of baseline hemoglobin levels with long-term adverse events after percutaneous coronary interventions has not been yet thoroughly defined. We aimed to assess the clinical impact of baseline hemoglobin on long-term ischemic and bleeding risk after percutaneous coronary intervention. Methods and Results: Using the pooled individual patient-level data from the 3 percutaneous coronary intervention studies, we categorized 19 288 patients into 4 groups: high-normal hemoglobin (≥14.0 g/dL; n=7555), low-normal hemoglobin (13.0-13.9 g/dL in men and 12.0-13.9 g/dL in women; n=5303), mild anemia (11.0-12.9 g/dL in men and 11.0-11.9 g/dL in women; n=4117), and moderate/severe anemia (<11.0 g/dL; n=2313). Median follow-up duration was 3 years. Low-normal hemoglobin, mild anemia, and moderate/severe anemia correlated with significant excess risk relative to high-normal hemoglobin for GUSTO (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Arteries Trial) moderate/severe bleeding, with adjusted hazard ratios of 1.22 (95% CI, 1.04-1.44), 1.73 (95% CI, 1.47-2.04), and 2.31 (95% CI, 1.92-2.78), respectively. Moderate/severe anemia also correlated with significant excess risk relative to high-normal hemoglobin for the ischemic composite end point of myocardial infarction/ischemic stroke (adjusted hazard ratio, 1.33; 95% CI, 1.11-1.60), whereas low-normal hemoglobin and mild anemia did not. However, the excess risk of low-normal hemoglobin, mild anemia, and moderate/severe anemia relative to high-normal hemoglobin remained significant for ischemic stroke and for mortality. Conclusions: Decreasing baseline hemoglobin correlated with incrementally higher long-term risk for major bleeding, ischemic stroke, and mortality after percutaneous coronary intervention. Even within normal range, lower baseline hemoglobin level correlated with higher ischemic and bleeding risk

Capture of bacteria by flexible carbon nanotubes

Capture of bacteria with flexible carbon nanotubes (CNTs) was done in vitro. Bundles of single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) was mixed with Streptococcus mutans. Precipitation assays and colony-forming unit formation assays showed free S. mutans in the solution was significantly decreased by the addition of the CNTs. Observation of the precipitate by scanning electron microscopy showed bacterial adhesion to CNTs. It has been shown that CNTs of different diameters have significantly different effects on the precipitation efficiency, and the manners in which they capture the cells are different. We found that MWCNTs (diameter of approximately 30 nm) had the highest precipitation efficiency, which was attributable to both their adequate dispersibility and aggregation activity. From observations by scanning electron microscopy, bundles of SWCNTs and thin MWCNTs (diameter of approximately 30 nm), which were moderately flexible, were easily wound around the curved surface of S. mutans. Bare CNTs having high adhesive ability could be useful as biomaterials, e.g., as tools for the elimination of oral pathogens at the nano-level

Strong adhesion of Saos-2 cells to multi-walled carbon nanotubes

In recent years, carbon nanotubes (CNTs) have been considered potential biomedical materials because of their unique character. The aim of this study was to investigate the response of a human osteoblast-like cell line - Saos-2 - on single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs). The surface of a culture dish was coated with CNTs, and Saos-2 cells were cultured for three days. Cell morphology, viability, alkaline phosphatase (ALP) activity, adhesion, and vinculin expression were evaluated. The result showed high cell viability and strong adhesion to MWCNTs. Saos-2 cultured on MWCNTs exhibited vinculin expression throughout the cell body. while the cells attached to SWCNTs and glass were mostly limited to their periphery. Our results suggest that CNT coatings promote cell activity and adhesiveness. These findings indicate that MWCNTs could be used as surface coating materials to promote cell adhesion

Modification of the dentin surface by using carbon nanotubes.

Recent studies have shown that carbon nanotubes (CNTs) can be used as biomedical materials because of their unique properties. CNTs effect nucleation of hydroxyapatite, because of which considerable interest has been generated regarding the use of CNTs in dentistry. However, there are only a few reports on the use of CNTs as dental materials. In this study, we investigated the changes induced in the surfaces of tooth slices by the application of a coating of CNTs by observing CNT-coated tooth slices both macroscopically as well as under a scanning electron microscope. Further, we investigated the effect of CNT coating on the tensile bond strength of dentin adhesives. CNTs adhered easily to the tooth surfaces when tooth slices were suspended in a CNT-dispersed solution. Interestingly, it was observed that CNTs selectively adhered to the surfaces of dentin and cementum, possibly by adhering to their exposed collagen fibers. In addition, the CNT coating did not affect the tensile bond strength of dentin adhesives. These results indicate that coating of the teeth with CNTs can be a possible application of CNTs as dental materials

Apatite formation on carbon nanotubes

Apatite coating on carbon nanotubes (CNTs) was done with a biomimetic coating method. The multi-walled CNTs (MWNTs) of curled shape with about 30 nm in diameter were immersed for 2 weeks in the simulated body fluid. Observation by scanning electron microscopy (SEM) showed the formation of apatite on the MWNTs surface. The clusters of spherules consisting of needle shape of apatite crystallites were massively grown on the aggregated MWNTs. The crystallites of 100 nm in width and 200-500 nm in length were grown perpendicularly to the longitudinal direction and radially originating from a common center of a single MWNT. Thus the architecture of crystalline apatite at nano-scale levels could be produced by simple method and the MWNT may be acting as core for initial crystallization of apatite

Thin films of single-walled carbon nanotubes promote human osteoblastic cells (Saos-2) proliferation in low serum concentrations

One strategy used for the regeneration of bone is the development of cell culture substrates and scaffolds that can control osteoblast proliferation and differentiation. In recent investigations, carbon nanotubes (CNTs) have been utilized as scaffolds for osteoblastic cell cultures; however, there are only a few reports describing the proliferation of osteoblastic cells on thin CNT films; in particular, the effects of serum concentration on cell proliferation has not been studied. In the present study, we prepared culture dishes with homogeneous thin or thick films of non-modified CNTs and examined the effect of serum concentrations on human osteoblastic cells (Saos-2) proliferation in these culture dishes. We demonstrated that the ratio of cell proliferation was strongly affected by the concentration of serum. Interestingly, single-walled carbon nanotube (SWNT) thin films were found to be the most effective substrate for the proliferation of Saos-2 cells in low concentrations of serum. Thus, thin SWNT films may be used as an effective biomaterial for the culture of Saos-2 cells in low serum concentrations

Maintenance of hemiround colonies and undifferentiated state of mouse induced pluripotent stem cells on carbon nanotube-coated dishes

Induced pluripotent stem (iPS) cells have attracted　worldwide interest. However, there　have been only a few studies investigating effective culture　substrates for feeder-free culturing for the　maintenance of iPS cells. In this study, we cultured mouse iPS cells under feeder-free conditions on carbon nanotube (CNT)-coated dishes and then evaluated the colony morphology and differentiation state of the cells on the dishes. After 5 d of cultivation in a medium containing 15% fetal bovine serum (FBS) and leukemia inhibitory factor (LIF), the colonies on thick films of multi-walled CNTs (MWCNTs) were observed to be hemiround; further, the cells expressed early undifferentiation markers. On the other hand, the colonies on a cell culture polystyrene dish and a collagen-coated polystyrene dish showed indistinct outline and spread well, and most spreading cells only weakly expressed early undifferentiation markers. These results indicate that the thick films of MWCNTs could maintain hemiround colonies and undifferentiated state of mouse iPS cells cultured under feeder-free conditions