Silica-coated graphene compared to Si-CdSe/ZnS quantum dots: Toxicity, emission stability, and role of silica in the uptake process for imaging purposes.

Quantum dots (QDs) present a special type of nanocrystals (NCs) due to their unique optical and chemical properties. While cadmium-based QDs (Cd-QDs) have the most favorable physicochemical properties, their toxicity, instability in the aqueous phase, and loss of brightness at high temperature are some of the obstacles that prevent the wide use of Cd-QDs. Carbon-based QDs as graphene quantum dots (GQDs) represent a very promising biocompatible replacement. In the present work, we mainly focus on comparing the efficiency and uptake of GQDs and Cd-QDs for fluorescent imaging purposes and studying the effect of growing silica shell on the emission and the uptake of QDs inside living human and bacterial cells. Graphene and CdSe/ZnS QDs were prepared and encapsulated in silica to increase their emission and uptake by living cells. Moreover, we studied their photostability and cytotoxicity. The Prepared G-Si QDs showed good emission inside the cytoplasmic portion of the liver hepatocellular carcinoma cell line (HepG2) and Bacillus subtilis (B. subtilis), but they revealed lower photoluminescence (PL) intensity compared to Si-CdSe/ZnS NCs although G-Si QDs are advantageous in other aspects, i.e. possess lower toxicity and higher stability with temperature variations.

Spectroscopic and photostability study of water-soluble hypericin encapsulated with polyvinylpyrrolidone.

Hypericin has gained great attention as a powerful photosensitizing and fluorescent agent for photodynamic therapy (PDT) and fluorescence diagnosis (FD) of cancer. However, native hypericin is hydrophobic and nearly insoluble in aqueous media which hinders its photobiological activity. Herein, we demonstrate the encapsulation of hypericin and polyvinylpyrrolidone (hypericin@PVP) as an attractive class of water-soluble formula of hypericin with improved absorption and emission characteristics in water. The absorption and fluorescence properties of the water-soluble hypericin@PVP were studied at room temperature. Also, the photostability of the prepared hypericin@PVP was studied under visible light irradiation. The absorbance and emission measurements confirm the association and binding of hypericin and PVP with a binding constant (Kb) of 1.2 × 105 M-1. The interaction between hypericin and PVP in water could lead to the dissociation of aggregated hypericin into their monomeric state which is crucial for effective photobiological implementation in PDT and FD. Upon encapsulation with PVP, hypericin showed a significant increase in the fluorescence properties with an enhanced emission intensity of 300% at a PVP concentration of 1 × 10-4 M. Moreover, water-soluble hypericin@PVP demonstrated high photostability under visible light irradiation with an irradiance of 15 mW/cm2 and exposure time up to 150 min. This enhancement in the absorption, emission, and photostability of hypericin in water is related to the effects of encapsulation with PVP and the unique spectroscopic properties of the formulated hypericin@PVP.

IR-enhanced photothermal therapeutic effect of graphene magnetite nanocomposite on human liver cancer HepG2 cell model.

Background: Graphene magnetite nanocomposites (G/Fe3O4) exhibit light photothermal conversion upon enhancement by 808 nm IR laser excitation. We evaluated the cytotoxic and photothermal effects of G/Fe3O4 on a HepG2 human liver cancer cell model. Methods: Graphene nanosheets (rGO), magnetite nanoparticles (Fe3O4), and G/Fe3O4 were prepared by chemical methods and characterized using transmission electron microscopy, Raman spectroscopy, zeta analysis, and vibrating sample magnemeter. Dark and light cytotoxicity were screened with colorimetric Sulforhodamine B cell viability assay after 24 and 48 hours. DNA fragmentation and some apoptotic genes on a transcriptional RNA level expression were performed. All prepared nanomaterials were evaluated for their photothermal effect at concentrations of 10 and 50 µg/mL. The power density incident on the cells by 300 mW 808 IR diode laser was 0.597 W/cm2. Results: Treatment of HepG2 with 400 µg/mL of rGO, Fe3O4, and G/Fe3O4 showed alteration in cell morphology after 24 hours of cell treatment and revealed toxic effects on cellular DNA. Evaluation of the cytotoxic effects showed messenger RNA (mRNA) in ß-actin and Bax apoptotic genes, but no expression of mRNA of caspase-3 after 24 hours of cell exposure, suggesting the involvement of an intrinsic apoptotic caspase-independent pathway. A photothermal effect was observed for G/Fe3O4 after irradiation of the HepG2 cells. A marked decrease was found in cell viability when treated with 10 and 50 µg/mL G/Fe3O4 from 40% to 5% after 48 hours of cell treatment. Conclusion: Results indicate that G/Fe3O4 nanocomposite was effective at transformation of light into heat and is a promising candidate for cancer therapy.

Photothermal versus photodynamic treatment for the inactivation of the bacteria Escherichia coli and Bacillus cereus: An in vitro study.

The widespread occurrence of microbial pathogens, including multidrug-resistant (MDR) bacteria, has ignited research efforts to discover alternative strategies to combat infections in patients. Recently, photodynamic therapy (PDT) and photothermal therapy (PTT) have been proposed for the inactivation of pathogens. Although PDT and PTT are very promising antipathogenic tools, further effort is needed to determine their real impact on pathogens apart from the effects of individual elements involved in the photodynamic/photothermal processes, i.e., light, photosensitizers (PSs), and nanoparticles. Accordingly, in the current study, toluidine blue O (TBO) and gold nanoparticles (GNP) were used as generators of reactive oxygen species (ROS) and hyperthermia in the presence of light, respectively. Escherichia coli (E. coli) and Bacillus cereus (B. cereus) bacteria were chosen as examples of gram-negative and gram-positive bacteria, respectively. Before the bactericidal activity of PDT was assessed, the aggregation of TBO and its effect on the growth of both strains of bacteria were studied. Additionally, E. coli and B. cereus were exposed to a range of doses of 633 nm helium-neon laser light to investigate its effect. In a separate set of experiments, the bactericidal activity of PTT was assessed after the effects of GNP and green light (530 nm) had been assessed. The results showed that PDT and PTT should be considered useful tools for bacterial eradication even when the light, PSs, and nanoparticles are each used at doses safe for bacterial growth. Moreover, different photodynamic responses were observed for E. coli and B. cereus, and light from a 633 nm laser and a 530 nm light-emitting diode (LED) showed disparate responses when applied alone to both bacteria.

One-step synthesis of phyto-polymer coated gold nanospheres as a delivery system to enhance resveratrol cytotoxicity.

This study introduces a simple method for one-step synthesis of highly stable nontoxic polymer-coated gold nanospheres for use in drug delivery, focuses on the ability of chloroauric acid (HAu Cl4 ) to induce polyphenols polymerization, puts up an easy procedure for loading hydrophobic drugs onto gold nanoparticles with ultra-high loading efficiency and studies the cytotoxicity of free and gold nanoparticles-loaded resveratrol. Gold nanospheres were synthesized simply by direct reaction between resveratrol itself and HAu Cl4 in aqueous medium. Synthesized gold nanospheres exhibited high stability in both aqueous and ethanolic solutions. UV-visible spectrum showed that the synthesized gold nanospheres have maximum absorption at 532 nm. TEM imaging, mass and FT-IR spectrometry revealed the presence of a distinct polymeric shell around each nanoparticle. Resveratrol, as a chemopreventive agent, was loaded onto the synthesized gold nanospheres with an ultra-high loading capacity (11.6% w/w). Free resveratrol, free gold nanospheres, and resveratrol-loaded gold nanospheres were examined for cytotoxicity on HepG2 cell line where cytotoxicity of loaded resveratrol was dramatically enhanced to reach about nine folds as that of free resveratrol at the same concentration.

Effect of Novel Quercetin Titanium Dioxide-Decorated Multi-Walled Carbon Nanotubes Nanocomposite on Bacillus subtilis Biofilm Development.

The present work was targeted to design a surface against cell seeding and adhering of bacteria, Bacillus subtilis. A multi-walled carbon nanotube/titanium dioxide nano-power was produced via simple mixing of carbon nanotube and titanium dioxide nanoparticles during the sol-gel process followed by heat treatment. Successfully, quercetin was immobilized on the nanocomposite via physical adsorption to form a quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite. The adhesion of bacteria on the coated-slides was verified after 24 h using confocal laser-scanning microscopy. Results indicated that the quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite had more negativity and higher recovery by glass surfaces than its counterpart. Moreover, coating surfaces with the quercetin-modified nanocomposite lowered both hydrophilicity and surface-attached bacteria compared to surfaces coated with the multi-walled carbon nanotubes/titanium dioxide nanocomposite.

Gelatin nanoparticles enhance delivery of hepatitis C virus recombinant NS2 gene.

BACKGROUND: Development of an effective non-viral vaccine against hepatitis C virus infection is of a great importance. Gelatin nanoparticles (Gel.NPs) have an attention and promising approach as a viable carrier for delivery of vaccine, gene, drug and other biomolecules in the body. AIM OF WORK: The present study aimed to develop stable Gel.NPs conjugated with nonstructural protein 2 (NS2) gene of Hepatitis C Virus genotype 4a (HCV4a) as a safe and an efficient vaccine delivery system. METHODS AND RESULTS: Gel.NPs were synthesized and characterized (size: 150±2 nm and zeta potential +17.6 mv). NS2 gene was successfully cloned and expressed into E. coli M15 using pQE-30 vector. Antigenicity of the recombinant NS2 protein was confirmed by Western blotting to verify the efficiency of NS2 as a possible vaccine. Then NS2 gene was conjugated to gelatin nanoparticles and a successful conjugation was confirmed by labeling and imaging using Confocal Laser Scanning Microscope (CLSM). Interestingly, the transformation of the conjugated NS2/Gel.NPs complex into E. coli DH5-α was 50% more efficient than transformation with the gene alone. In addition, conjugated NS2/Gel.NPs with ratio 1:100 (w/w) showed higher transformation efficiency into E. coli DH5-α than the other ratios (1:50 and 2:50). CONCLUSION: Gel.NPs effectively enhanced the gene delivery in bacterial cells without affecting the structure of NS2 gene and could be used as a safe, easy, rapid, cost-effective and non-viral vaccine delivery system for HCV.

Silver nanoparticles: Antimicrobial activity, cytotoxicity, and synergism with N-acetyl cysteine.

The fast progression of nanotechnology has led to novel therapeutic interventions. Antimicrobial activities of silver nanoparticles (Ag NPs) were tested against standard ATCC strains of Staphylococcus aureus (ATCC 9144), Escherichia coli (O157:H7), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 90028) in addition to 60 clinical isolates collected from cancer patients. Antimicrobial activity was tested by disk diffusion method and MIC values for Ag NPs alone and in combination with N-acetylcysteine (NAC) against tested pathogens were determined by broth microdilution method. Ag NPs showed a robust antimicrobial activity against all tested pathogens and NAC substantially enhanced the antimicrobial activity of Ag NPs against all tested pathogens. Synergism between Ag NPs and NAC has been confirmed by checkerboard assay. The effect of Ag NPs on tested pathogens was further scrutinized by Transmission Electron Microscope (TEM) which showed disruption of cell wall in both bacteria and fungi. Ag NPs abrogated the activity of respiratory chain dehydrogenase of all tested pathogens and released muramic acid content from S. aureus in culture. The cytotoxic effect of Ag NPs alone and in combination with NAC was examined using human HepG2 cells and this revealed no cytotoxicity at MIC values of Ag NPs and interestingly, NAC reduced the cytotoxic effect of Ag NPs at concentrations higher than their MIC values. Taken together, Ag NPs have robust antimicrobial activity and NAC substantially enhances their antimicrobial activities against MDR pathogens which would provide a novel safe, effective, and inexpensive therapeutic approach to control the prevalence of MDR pathogens.

Synthesis, Characterization and Cytotoxic Evaluation of Graphene Oxide Nanosheets: In Vitro Liver Cancer Model

Background: Graphene nanosheets have a broad spectrum of biomedical applications. Hepatocellular cancer (HCC) is a major health problem in the Egyptian population. Currently, treatment strategies are invasive and have several adverse side effects. Thus, other approaches are required for managing this aggressive type of cancer. Our objective here was to prepare and characterize graphene oxide nanosheets and evaluate cytotoxic effect at the molecular level in an in vitro human liver cancer cell model (HepG2). Methods: Graphene oxide nanosheets were generated by chemical oxidation and characterized by transmission electron microscopy and X-ray diffraction. Cytotoxic effects in HepG2 cells were monitored by sulforhodamine B (SRB) colorimetric assay followed by flow cytometric analysis. Molecular investigations of DNA fragmentation and expression of some apoptotic genes at the transcriptional RNA level were also performed. Results: Treatment of HepG2 cells with 400µg/ml graphene oxide nanosheets showed alteration in cell morphology after 24 h. Flow cytometry revealed accumulation of cells in S phase of cell cycle followed by dramatic effects on cellular DNA. Extensive evaluation of the cytotoxic effects of graphene oxide showed increased mRNA Bax apoptotic gene expression with not of P53 and caspase-3 mRNA after 24h, suggesting involvement of an intrinsic apoptotic caspase-independent pathway. Conclusion. Graphene oxide can mediate apoptotic gene signaling in human liver cancer cells opening a novel approach to cancer management. Further analyses at the molecular level are now required to confirm our results and facilitate biomedical applications in vivo.

Application of quercetin and its bio-inspired nanoparticles as anti-adhesive agents against Bacillus subtilis attachment to surface.

The aim of this study was directed to reveal the repulsive effect of coated glass slides by quercetin and its bio-inspired titanium oxide and tungsten oxide nanoparticles on physical surface attachment of Bacillus subtilis as an ab-initio step of biofilm formation. Nanoparticles were successfully synthesized using sol-gel and acid precipitation methods for titanium oxide and tungsten oxide, respectively (in the absence or presence of quercetin). The anti-adhesive impact of the coated-slides was tested through the physical attachment of B. subtilis after 24h using Confocal Laser Scanning Microscopy (CLSM). Here, quercetin was presented as a bio-route for the synthesis of tungsten mixed oxides nano-plates at room temperature. In addition, quercetin had an impact on zeta potential and adsorption capacity of both bio-inspired amorphous titanium oxide and tungsten oxide nano-plates. Interestingly, our experiments indicated a contrary effect of quercetin as an anti-adhesive agent than previously reported. However, its bio-inspired metal oxide proved their repulsive efficiency. In addition, quercetin-mediated nano-tungsten and quercetin-mediated amorphous titanium showed anti-adhesive activity against B. subtilis biofilm.