Exploring the antibiofilm and toxicity of tin oxide nanoparticles: Insights from in vitro and in vivo investigations

BACKGROUND INFORMATION

The advancement of biological-mediated nanoscience towards higher levels and novel benchmarks is readily apparent, owing to the use of non-toxic synthesis processes and the incorporation of various additional benefits. This study aimed to synthesize stable tin oxide nanoparticles (SnO2-NPs) using S. rhizophila as a mediator.

METHODS

The nanoparticles that were created by biosynthesis was examined using several analytical techniques, including Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), UV-visible (UV-vis) spectroscopy, and energy dispersive X-ray spectroscopy (EDS).

RESULTS

The results obtained from the characterization techniques suggest that S. rhizophila effectively catalyzed the reduction of SnCl2 to SnO2-NPs duration of 90 min at ambient temperature with the ƛmax of 328 nm. The size of the nano crystallite formations was measured to be 23 nm. The present study investigates nanoscale applications' antibacterial efficacy against four bacterial strains, including Klebsiella Sp, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The observed zone of inhibition for the nanoparticles (NPs) varied from 10 to 25 mm. The research findings demonstrate that the nanoparticles (NPs) are effective as antibacterial, phytotoxic, and cytotoxic agents.

Investigation of antimicrobial and anti-cancer activity of thermally sensitive SnO2 nanostructures with green-synthesized cauliflower morphology at ambient weather conditions

A tin oxide (SnO2) nanostructure was prepared using Matricaria recutita leaf extract to investigate its anticancer activity against SK-MEL-28 cells. The tetragonal crystal structure of tin oxide nanoparticles with an average crystal size of 27 nm was confirmed by X-ray diffraction (XRD) analysis. The tetragonal crystal structure of the tin oxide nanoparticles, with an average crystallite size of 27 nm, was confirmed by XRD an absorbance peak at 365 nm was identified by UV-visible spectroscopy analysis as belonging to the bio-mediated synthesis of SnO2 nanoparticles. The SnO2 NPs are capped and stabilized with diverse functional groups derived from bioactive molecules, including aldehydes, benzene rings, amines, alcohols, and carbonyl stretch protein molecules. Fourier transform infrared spectroscopy (FTIR) analysis validated the presence of these capping and stabilizing chemical bonds. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed the cauliflower-shaped morphology of the SnO2 nanoparticles with an average particle size of 28 nm. The antimicrobial activity of both prepared and encapsulated samples confirmed their biological activities. Furthermore, both prepared and encapsulated tin oxide samples exhibited excellent anticancer activity against SK-MEL-28 human cancer cells. The present study introduces a reliable and uncomplicated approach to produce SnO2 nanoparticles and demonstrates their effectiveness in various applications, including cancer therapy, drug administration, and disinfectant.

Near-Infrared Upconversion Mesoporous Tin Dioxide Theranostic Nanocapsules for Synergetic Cancer Chemophototherapy

Smart nanotheranostic systems (SNSs) have attracted extensive attention in antitumor therapy. Nevertheless, constructing SNSs with disease diagnosis ability, improved drug delivery efficiency, inherent imaging performance, and high treatment efficiency remains a scientific challenge. Herein, ultrasmall tin dioxide (SnO₂) was assembled with upconversion nanoparticles (UCNPs) to form mesoporous nanocapsules by an in situ hydrothermal deposition method, followed by loading with doxorubicin (DOX) and modification with bovine serum albumin (BSA). pH/near-infrared dual-responsive nanotheranostics was constructed for computed tomography (CT) and magnetic resonance (MR) imaging-induced collaborative cancer treatment. The mesoporous channel of SnO₂ was utilized as a reservoir to encapsulate DOX, an antineoplastic drug, for chemotherapy and as a semiconductor photosensitizer for photodynamic therapy (PDT). Furthermore, the DOX-loaded UCNPs@SnO₂-BSA nanocapsules combined PDT, Nd³⁺-doped UCNP-triggered hyperthermia effect, and DOX-triggered chemotherapy simultaneously and demonstrated prominently enhanced treatment efficiency compared to the monotherapy model. Moreover, tin, as one of the trace elements in the human body, has a similar X-ray attenuation coefficient to iodine and therefore can act as a contrast agent for CT imaging to monitor the treatment process. Such an orchestrated synergistic anticancer treatment exhibited apparent inhibition of tumor growth in tumor-bearing mice with negligible side effects. Our study demonstrates nanocapsules with excellent biocompatibility and great potential for cancer treatment.

Induction of mitochondria mediated apoptosis in human ovarian cancer cells by folic acid coated tin oxide nanoparticles

PURPOSE

This study aims to prepare folic acid coated tin oxide nanoparticles (FA-SnO2 NPs) for specifically targeting human ovarian cancer cells with minimum side effects against normal cells.

METHODS

The prepared FA-SnO2 NPs were characterized by FT-IR, UV-vis spectroscopy, XRD, SEM and TEM. The inhibition effects of FA-SnO2 NPs against SKOV3 cancer cell were tested by MTT and LDH assay. Apoptosis induction in FA-SnO2 NPs treated SKOV3 cells were investigated using Annexin V/PI, AO/EB and Comet assays and the possible mechanisms of the cytotoxic action were studied by Flow cytometry, qRT-PCR, Immunohistochemistry, and Western blotting analyses. The effects of FA-SnO2 NPs on reactive oxygen species generation in SKOV3 cells were also examined. Additionally, the safety of utilization FA-SnO2 NPs were studied in vivo using Wister rats.

RESULTS

The obtained FA-SnO2 NPs displayed amorphous spherical morphology with an average diameter of 157 nm and a zeta potential value of -24 mV. Comparing to uncoated SnO2 NPs, FA-SnO2 NPs had a superior inhibition effect towards SKOV3 cell growth that was suggested to be mediated through higher reactive oxygen species generation. It was showed that FA-SnO2 NPs increased significantly the % of apoptotic cells in the sub- G1 and G2/M phases with a higher intensity comet nucleus in SKOV3 treated cells. Furthermore, FA-SnO2 NPs was significantly increased the expression levels of P53, Bax, and cleaved Caspase-3 and accompanied with a significant decrease of Bcl-2 in the treated SKOV3 cells.

CONCLUSION

Overall, the results suggested that an increase in cellular FA-SnO2 NPs internalization resulted in a significant induced cytotoxicity in SKOV3 cancer cells in dose-dependent mode through ROS-mediated cell apoptosis that may have occurred through mitochondrial pathway. Additionally, the results confirmed the safety of utilization FA-SnO2 NPs against living systems. So, FA-SnO2 NPs with a specific targeting moiety may be a promising therapeutic candidate for human ovarian cancer.

Adhesion of Neurons and Glial Cells with Nanocolumnar TiN Films for Brain-Machine Interfaces

Coupling of cells to biomaterials is a prerequisite for most biomedical applications; e.g., neuroelectrodes can only stimulate brain tissue in vivo if the electric signal is transferred to neurons attached to the electrodes' surface. Besides, cell survival in vitro also depends on the interaction of cells with the underlying substrate materials; in vitro assays such as multielectrode arrays determine cellular behavior by electrical coupling to the adherent cells. In our study, we investigated the interaction of neurons and glial cells with different electrode materials such as TiN and nanocolumnar TiN surfaces in contrast to gold and ITO substrates. Employing single-cell force spectroscopy, we quantified short-term interaction forces between neuron-like cells (SH-SY5Y cells) and glial cells (U-87 MG cells) for the different materials and contact times. Additionally, results were compared to the spreading dynamics of cells for different culture times as a function of the underlying substrate. The adhesion behavior of glial cells was almost independent of the biomaterial and the maximum growth areas were already seen after one day; however, adhesion dynamics of neurons relied on culture material and time. Neurons spread much better on TiN and nanocolumnar TiN and also formed more neurites after three days in culture. Our designed nanocolumnar TiN offers the possibility for building miniaturized microelectrode arrays for impedance spectroscopy without losing detection sensitivity due to a lowered self-impedance of the electrode. Hence, our results show that this biomaterial promotes adhesion and spreading of neurons and glial cells, which are important for many biomedical applications in vitro and in vivo.

Oxi-Redox Selective Breast Cancer Treatment: An In Vitro Study of Theranostic In-Based Oxide Nanoparticles for Controlled Generation or Prevention of Oxidative Stress

In this article, we demonstrate that specifically engineered oxide nanoparticles (NPs) have the potential to act as theranostic materials that are able to generate or prevent oxidative stress through their oxi-redox activity in various types of malignant and nonmalignant cells. The oxi-redox activity is related to the type and presence of surface defects, which is modified with appropriate synthesis conditions. In the present work, we used MDA-MB-231 and MCF-7 human breast cancer cells and nonmalignant MCF-10A human breast cells to demonstrate how controlled oxidative stress mediated by specifically nanoengineered indium tin oxide (ITO) NPs can selectively induce cell death in the cancer cells while reducing the oxidative stress in the normal cells and supporting their proliferation. The ITO NPs are also promising nanotheranostic materials for cancer therapy and contrast agents because of their multimodal imaging capabilities. We demonstrate that the synthesized ITO NPs can selectively increase the generation of reactive oxygen species (ROS) in both breast tumor cell lines, resulting in activation of apoptosis, and can also greatly suppress the cellular proliferation in both types of tumor cells. In contrast, the ITO NPs exhibit ROS scavenging-like behavior, significantly decreasing the ROS levels in MCF-10A cells exposed to the additional ROS, hydrogen peroxide (H₂O₂), so that they protect the proliferation of nonmalignant MCF-10A cells from ROS damage. In addition, fluorescent microscopy images revealed that the ITO NPs emit strong fluorescence that could be used to reveal their location. Moreover, computed tomography imaging demonstrated that the ITO NPs exhibited a comparable capability toward anatomical contrast enhancement. These results suggest that the synthesized ITO NPs have the potential to be a novel selective therapeutic agent with a multimodal imaging property for anticancer treatment.

SnO2-Doped ZnO/Reduced Graphene Oxide Nanocomposites: Synthesis, Characterization, and Improved Anticancer Activity via Oxidative Stress Pathway

BACKGROUND

Therapeutic selectivity and drug resistance are critical issues in cancer therapy. Currently, zinc oxide nanoparticles (ZnO NPs) hold considerable promise to tackle this problem due to their tunable physicochemical properties. This work was designed to prepare SnO2-doped ZnO NPs/reduced graphene oxide nanocomposites (SnO2-ZnO/rGO NCs) with enhanced anticancer activity and better biocompatibility than those of pure ZnO NPs.

MATERIALS AND METHODS

Pure ZnO NPs, SnO2-doped ZnO (SnO2-ZnO) NPs, and SnO2-ZnO/rGO NCs were prepared via a facile hydrothermal method. Prepared samples were characterized by field emission transmission electron microscopy (FETEM), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), ultraviolet-visible (UV-VIS) spectrometer, and dynamic light scattering (DLS) techniques. Selectivity and anticancer activity of prepared samples were assessed in human breast cancer (MCF-7) and human normal breast epithelial (MCF10A) cells. Possible mechanisms of anticancer activity of prepared samples were explored through oxidative stress pathway.

RESULTS

XRD spectra of SnO2-ZnO/rGO NCs confirmed the formation of single-phase of hexagonal wurtzite ZnO. High resolution TEM and SEM mapping showed homogenous distribution of SnO2 and rGO in ZnO NPs with high quality lattice fringes without any distortion. Band gap energy of SnO2-ZnO/rGO NCs was lower compared to SnO2-ZnO NPs and pure ZnO NPs. The SnO2-ZnO/rGO NCs exhibited significantly higher anticancer activity against MCF-7 cancer cells than those of SnO2-ZnO NPs and ZnO NPs. The SnO2-ZnO/rGO NCs induced apoptotic response through the upregulation of caspase-3 gene and depletion of mitochondrial membrane potential. Mechanistic study indicated that SnO2-ZnO/rGO NCs kill cancer cells through oxidative stress pathway. Moreover, biocompatibility of SnO2-ZnO/rGO NCs was also higher against normal breast epithelial (MCF10A cells) in comparison to SnO2-ZnO NPs and ZnO NPs.

CONCLUSION

SnO2-ZnO/rGO NCs showed enhanced anticancer activity and better biocompatibility than SnO2-ZnO NPs and pure ZnO NPs. This work suggested a new approach to improve the selectivity and anticancer activity of ZnO NPs. Studies on antitumor activity of SnO2-ZnO/rGO NCs in animal models are further warranted.

Near-Infrared Upconversion Mesoporous Tin Oxide Bio-Photocatalyst for H2O2-Activatable O2-Generating Magnetic Targeting Synergetic Treatment

Tumor hypoxia compromises the therapeutic efficacy of oxygen (O₂)-dependent treatment methods as the endogenous O₂ levels have an important influence on the production of reaction oxygen species. Herein, a synergistic multifunctional mesoporous Fe@Sn-UCNPs bio-photocatalytic nanoplatform is provided to comprehensively realize endogenous hydrogen peroxide (H₂O₂)-activatable, self-supplied O₂, photothermal performance, and near-infrared-mediated magnetic targeting PDT/PTT simultaneously for relieving tumor hypoxia. Such a nanoplatform is constructed by encapsulating magnetic Fe₃O₄ with lanthanide-ion-doped mesoporous tin oxide upconversion nanoparticles and further modified with phosphorylated serine and poly(ethylene glycol) for enhancing the biocompatibility and solubility. The nanoparticles can be activated by endogenous H₂O₂ and in situ generated O₂ to relieve hypoxia through catalytic reaction. Therefore, H₂O₂-responsive/O₂-evolving nanoparticles can elevate the O₂ level in the tumor site for an apparently enhanced PDT effect in vitro and in vivo. What is more, Fe@Sn-UCNPs demonstrate enhanced photothermal conversion efficiency based on the special nanostructure and much more circuit loops for electron transitions between Fe₃O₄ and Sn-UCNPs, and the electronic structure of Fe@Sn-UCNPs was calculated. In addition, such Fe@Sn-UCNPs also exhibit multimodality imaging performance (including photothermal, magnetic resonance, and computed tomography imaging) for monitoring and tracking the in vivo tumor therapeutic process. This work provides novel insight into the smart Fe@Sn-UCNPs as an "all-in-one" theranostic nanosystem for cancer therapy.

Antibiofilm Action of ZnO, SnO2 and CeO2 Nanoparticles Towards Grampositive Biofilm Forming Pathogenic Bacteria

BACKGROUND

The ability to form biofilm and produce several virulence factors has caused numerous human pathogens to become tremendously resistant towards traditional antibiotic treatments, thus, new alternative strategies are urgently in demand. One of the strategies that have recently been developed involves the application of metallic Nanoparticles (NPs). Up to the present, promising results in terms of antimicrobial and antibiofilm activities have been observed in a wide range of metal NPs.

METHODS

The present study has selected three metal oxides such as ZnO, SnO2 and CeO2 NPs to comparatively investigate their antibiofilm and antibacterial properties against two Gram-positive human pathogens, which are Listeria monocytogenes and Staphylococcus aureus.

RESULTS

The anti-biofilm activities of ZnO, SnO2 and CeO2 NPs against S. aureus and L. monocytogenes were assayed by crystal violet staining and confirmed by microscopic visualization using SEM. The synthesis of amyloid protein by S. aureus and exopolysaccharide by L. monocytogenes in the presence of ZnO, SnO2 and CeO2 NPs was evaluated by Congo red assay.

DISCUSSION

Results have shown that ZnO, SnO2 and CeO2 NPs effectively inhibited biofilm formation of both L. monocytogenes and S. aureus. The microscopic analysis also confirmed the antibiofilm activity of these NPs. It was also found that only ZnO NPs inhibited cell growth as well as the production of amyloid protein in S. aureus.

CONCLUSION

Overall, these results indicated that ZnO, SnO2 and CeO2 NPs can be considered as potential agents for treating the infections caused by L. monocytogenes and S. aureus, especially those associated with biofilm formation. Based on the present study, further studies are required to understand their mechanisms at both phenotypic and molecular levels, as well as their in vivo cytotoxicity, thereby enabling the applications of these metal oxide NPs in biomedical fields and food industry.

Influence of pure fluorides and stannous ions on the initial bacterial colonization in situ

The present clinical-experimental study aims to examine the effect of pure experimental fluoride solutions and stannous chloride on the initial oral bioadhesion under in situ conditions. After 1 min of pellicle formation on bovine enamel slabs, 12 subjects rinsed with 8 ml of the fluoride test solutions (NaF, Na2PO3F, AmF, SnF2,) with 500 ppm fluoride concentration each for 1 min. Additionally, rinsing without a solution (control) and rinsing with 1563 ppm SnCl2 solution took place for 1 min. Afterwards, fluorescence microscopy took place to visualize bacterial adhesion and glucan formation (8 h oral exposition) with DAPI and ConA and the BacLight method. TEM was performed to visualize the pellicle ultrastructure together with EDX to detect stannous ions. The rinsing solutions with pure SnF2 and SnCl2 reduced significantly the initial bacterial colonization (DAPI). While, NaF and Na2PO3F showed no significant effect compared to the control. There was no significant difference between AmF, SnF2 and SnCl2. All tested experimental solutions showed no reducing effect on the glucan formation. Considerable alterations of the pellicle ultrastructure resulted from rinsing with the Sn-containing solutions. SnF2 appears to be the most effective type of fluoride to reduce initial bacterial colonization in situ. The observed effects primarily have to be attributed to the stannous ions' content.

Enhanced Osseointegration of Hierarchically Structured Ti Implant with Electrically Bioactive SnO2-TiO2 Bilayered Surface

The poor osseointegration of Ti implant significantly compromise its application in load-bearing bone repair and replacement. Electrically bioactive coating inspirited from heterojunction on Ti implant can benefit osseointegration but cannot avoid the stress shielding effect between bone and implant. To resolve this conflict, hierarchically structured Ti implant with electrically bioactive SnO₂-TiO₂ bilayered surface has been developed to enhance osseointegration. Benefiting from the electric cue offered by the built-in electrical field of SnO₂-TiO₂ heterojunction and the topographic cue provided by the hierarchical surface structure to bone regeneration, the osteoblastic function of basic multicellular units around the implant is significantly improved. Because the individual TiO₂ or SnO₂ coating with uniform surface exhibits no electrical bioactivity, the effects of electric and topographic cues to osseointegration have been decoupled via the analysis of in vivo performance for the placed Ti implant with different surfaces. The developed Ti implant shows significantly improved osseointegration with excellent bone-implant contact, improved mineralization of extracellular matrix, and increased push-out force. These results suggest that the synergistic strategy of combing electrical bioactivity with hierarchical surface structure provides a new platform for developing advanced endosseous implants.

Structural, Optical, Morphological and Microbial Studies on SnO₂ Nanoparticles Prepared by Co-Precipitation Method

Nanoparticles of tin oxide (SnO2) powders were prepared by co-precipitation method at 500 °C, 700 °C and 900 °C temperature. The sintered SnO2 nanoparticles, structural, optical, magnetic, morphological properties and microbial activity have been studied. XRD studies reveals that sintered powder which exhibits tetragonal crystal structure and both crystallinity as well as crystal size increase with increase in temperature. The morphological studies reveal randomly arranged grains with compact nature grain size increases with sintering temperature. The compositional analyses of SnO2 nanoparticles have been studied using X-ray photoelectron spectroscopy analysis. The optical band gap values of SnO2 nanoparticles were calculated to be about 4.3 eV in the temperature 500 °C, comparing with that of the bulk SnO2 3.78 eV, by optical absorption measurement. Room temperature M-H curve for pure SnO2 nanoparticles exhibits ferromagnetic behaviour. The tin oxide nanoparticles are acted as potential candidate material for bacterial and fungal activity.

Effect of wastewater quality parameters on coliform inactivation by tin oxide anodes

The effect of six water quality constituents on wastewater effluent disinfection by tin oxide anodes (TOAs) was investigated in single cell laboratory reactors. Several concentrations of suspended solids, chemical oxygen demand (COD), alkalinity, ammonia-nitrogen, nitrite-nitrogen, and nitrate-nitrogen were added to media containing 10⁶ total coliform bacteria mL^-1. Current was applied through the TOAs, and coliform bacteria viability was analyzed over time. Over 99.9% inactivation of coliform bacteria was found over 15 min in TOA reactors. Concentrations of the six water quality constituents typical of concentrations found in wastewaters had no effect on TOA disinfection efficacy. The results of this research demonstrate that TOAs, which could potentially be powered by solar panels, have potential as a sustainable disinfection process compared to chlorine, ozone, and ultraviolet light.

Biosynthesis of vitamin C stabilized tin oxide nanoparticles and their effect on body weight loss in neonatal rats

The green synthesis of tin oxide nanoparticles (SnO₂ NPs) using vitamin C (Vc) as a reducing agent via a biosynthetic approach is described. The effect of Vc-stabilized SnO₂ NPs on the body weight of neonatal rats is also studied. The prepared SnO₂NPs were characterized using spectroscopic and microscopic instrumental techniques including transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-vis), X-ray diffraction and Fourier transform infrared spectroscopy, which confirmed the formation of NPs. TEM images confirmed the formation of spherical NPs with a mean particle size of around 30nm. The body weight studies showed that vitamin-C stabilized SnO₂ NPs promote a higher body weight gain compared to raw SnO₂ NPs. It was also shown that Vc can counteract the decreased body weight caused by SnO₂ NPs in neonatal rats.

Effective Electrochemistry of Human Sulfite Oxidase Immobilized on Quantum-Dots-Modified Indium Tin Oxide Electrode

The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO.

Biocompatible and Antibacterial SnO2 Nanowire Films Synthesized by E-Beam Evaporation Method

In this work, the biocompatibility and antibacterial activities of novel SnO2 nanowire coatings prepared by electron-beam (E-Beam) evaporation process at low temperatures were studied. The nanowire coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) methods. The results of in vitro cytotoxicity and cell proliferation assays suggested that the SnO2 nanowire coatings were nontoxic and promoted the proliferation of C2C12 and L929 cells (> 90% viability). Cellular activities, cell adhesion, and lactate dehydrogenase activities were consistent with the superior biocompatibility of the nanowire materials. Notably, the nanowire coating showed potent antibacterial activity against six different bacterial strains. The antibacterial activity of the SnO2 material was attributed to the photocatalytic nature of SnO2. The antibacterial activity and biocompatibility of the newly developed SnO2 nanowire coatings may enable their use as coating materials for biomedical implants.

Electrochemical and fluorescence properties of SnO2 thin films and its antibacterial activity

Nanocrystalline SnO2 thin films were deposited by a simple and inexpensive sol-gel spin coating technique and the films were annealed at two different temperatures (350°C and 450°C). Structural, vibrational, optical and electrochemical properties of the films were analyzed using XRD, FTIR, UV-Visible, fluorescence and cyclic voltammetry techniques respectively and their results are discussed in detail. The antimicrobial properties of SnO2 thin films were investigated by agar agar method and the results confirm the antibacterial activity of SnO2 against Escherichiacoli and Bacillus.

Biogenic synthesis of SnO₂ nanoparticles: evaluation of antibacterial and antioxidant activities

Nanostructured semiconductors have been of special interest to scientific community due to their peculiar properties. The quantum size effect results in spectacular variation in the optical and vibrational characteristics of nanostructured materials compared to their bulk counterparts. The present work emphasizes an unexploited, cost effective, and environmentally benign method of synthesizing bioactive tin oxide nanoparticles of size from 2.1 nm to 4.1 nm using Saraca indica flower. The XRD pattern and HRTEM images of the samples revealed an increase in particle size with annealing temperature. Fine tuning band gap could be attained as evidenced by the shift of absorption band edge and photoluminescence emission. It is found that oxygen vacancies play an important role on PL emission. The synthesized nanoparticles exhibit antibacterial activity against gram negative bacteria Escherichia coli. The antioxidant activity is evaluated by scavenging free radicals of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The efficiency of biogenic SnO₂ nanoparticles as a promising antibacterial agent as well as an antioxidant for pharmaceutical applications is suggested.

The effect of saliva substitutes on enamel erosion in vitro

OBJECTIVES

To investigate the effect of saliva substitutes on enamel erosion in vitro.

METHODS

A total of 204 bovine enamel samples were embedded in acrylic resin and allocated to 17 groups (n=12). The specimens were eroded in an artificial mouth (3 days; 6×30 s/days, flow rate: 2 ml/min) using citric acid (pH: 2.5). Immediately after the erosive attacks, saliva substitutes (12 sprays, 3 gels) were applied. Between the erosive cycles the specimens were rinsed with artificial saliva (flowrate: 0.5 ml/min). A SnCl2/AmF/NaF-containing mouthrinse was used as positive control, water spray served as negative control. Enamel loss was measured profilometrically and the data were analyzed using one-way ANOVA followed by Scheffé's post hoc tests (p<0.05).

RESULTS

Four saliva substitutes increased enamel erosion, probably due to the low pH or the content of citric acid. Several saliva substitutes were able to reduce enamel erosion significantly by 60-90% (in the range of the positive control). The protective potential of these products was in the range of the positive control (reduction of enamel loss to 30% of negative control). The erosion-protective potential of these high-viscous products is probably related to their film-forming properties, leading to a mechanical protection of the surface.

CONCLUSION

Saliva substitutes containing a very low pH exhibit a distinct erosive potential, while most high-viscous products present an erosion-protective effect. It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.

CLINICAL SIGNIFICANCE

It can be recommended that patients suffering from xerostomia and at high risk for dental erosion should use high-viscous saliva substitutes, but should avoid saliva substitutes with low pH or containing citric acid.

Interaction of preosteoblasts with surface-immobilized collagen-based nanotubes

In a previous work, we demonstrated the successful use of electrophoretic deposition (EPD) to immobilize collagen-based nanotubes onto indium-tin-oxide-coated glass (ITO glass), leading to the creation of biointerfaces with protein-based chemistry and topography [1]. In this work, we present a first study of preosteoblasts behavior in contact with surface-immobilized collagen-based nanotubes. Changes in cell morphology after their interaction with ITO glass modified with collagen-based nanotubes were studied using fluorescence microscopy and compared to those observed on virgin ITO glass as well as on ITO glass on which a collagen layer was simply adsorbed. Scanning electron microscopy (SEM) was used to study interactions of cell filopodias with the deposited nanotubes. Cytotoxicity of these biointerfaces was examined as well in short term cultures, using Alamar blue assay. Cells showed particular morphologies on ITO glass coated with nanotubes compared to virgin ITO glass or collagen adsorbed layer on ITO glass. High resolution SEM images suggest that apart from cell morphology, length and thickness of filopodias seem to be significantly affected by surface modification with collagen-based nanotubes. Moreover, nanotube-coated ITO glass did not show any obvious cytotoxicity in short term culture, opening new perspectives for the surface modification of biomaterials. We show the versatility of the proposed surface modification procedure by tailoring biointerfaces with a mixture of micro- and nanometer-scale collagen-based tubes.

Tin oxide nanowires suppress herpes simplex virus-1 entry and cell-to-cell membrane fusion

The advent of nanotechnology has ushered in the use of modified nanoparticles as potential antiviral agents against diseases such as herpes simplex virus 1 and 2 (HSV-1) (HSV-2), human immunodeficiency virus (HIV), monkeypox virus, and hepatitis B virus. Here we describe the application of tin oxide (SnO₂) nanowires as an effective treatment against HSV-1 infection. SnO₂ nanowires work as a carrier of negatively charged structures that compete with HSV-1 attachment to cell bound heparan sulfate (HS), therefore inhibiting entry and subsequent cell-to-cell spread. This promising new approach can be developed into a novel form of broad-spectrum antiviral therapy especially since HS has been shown to serve as a cellular co-receptor for a number of other viruses as well, including the respiratory syncytial virus, adeno-associated virus type 2, and human papilloma virus.

Effect of tin oxide nanoparticle binding on the structure and activity of α-amylase from Bacillus amyloliquefaciens

Proteins adsorbed on nanoparticles (NPs) are being used in biotechnology, biosensors and drug delivery. However, understanding the effect of NPs on the structure of proteins is still in a nascent state. In the present paper tin oxide (SnO2) NPs were synthesized by the reaction of SnCl4·5H2O in methanol via the sol-gel method and characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The binding of these SnO2-NPs with α-amylase was investigated by using UV-vis, fluorescence and circular dichroism (CD) spectroscopic techniques. A strong quenching of tryptophan fluorescence intensity in α-amylase was observed due to formation of a ground state complex with SnO2-NPs. Far-UV CD spectra showed that the secondary structure of α-amylase was changed in the presence of NPs. The Michaelis-Menten constant (K(m)), was found to be 26.96 and 28.45 mg ml(-1), while V(max) was 4.173 and 3.116 mg ml(-1) min(-1) for free and NP-bound enzyme, respectively.

Indium-tin oxide coated microfabricated device for the injection of a single cell into a fused silica capillary for chemical cytometry

A microfabricated device is described for the capture and injection of a single mammalian cell into a fused silica capillary for subsequent analysis by chemical cytometry. The device consists of a 500 μm diameter well made from polydimethylsiloxane on an indium-tin oxide coated microscope slide. The bottom of the well contains a 2 μm high aperture, which was designed to block passage of cells. A cellular suspension was allowed to settle on the device, and aspiration through the aperture was used to trap a single NG-108 cell. Untrapped cells were washed from the device, and a 150 μm outer diameter and 50 μm inner diameter capillary was placed in the well. To inject a cell, voltage was applied to the indium-tin oxide while simultaneously applying vacuum at the distal end of the capillary.

Antioxidant activity of butyl- and phenylstannoxanes derived from 2-, 3- and 4-pyridinecarboxylic acids

In vitro antioxidant activity for 12 stannoxanes derived from Ph₃SnCl (compounds 1-3), Ph₂SnCl₂ (compounds 4-6), Bu₃SnCl (compounds 7-9), and Bu₂SnCl₂ (compounds 10-12), was assayed qualitatively by the chromatographic profile with 1,1-diphenyl-2-picrylhydrazil (DPPH) method and by two quantitative methods: the DPPH radical scavenging activity and Ferric-Reducing Antioxidant Power (FRAP) assays. The results were compared with those obtained with the starting materials 2-pyridine- carboxylic acid (I), 3-pyridinecarboxylic acid (II) and 4-pyridinecarboxylic acid (III), as well as with standard compounds, such as vitamin C and vitamin E, respectively. The in vitro antiradical activity with DPPH of diphenyltin derivative 5 showed a very similar behavior to vitamin C at a 20 μg/mL concentration, whereas according to the FRAP method, compound 8 was better. This difference is due to the mechanism of the antioxidant process. The Structure-Activity Relationships (SAR) for both methods is also reported.

Synthesis and characterization of tin(II) complexes of fluorinated Schiff bases derived from amino acids

New tin(II) complexes of general formula Sn(L)(2) (L=monoanion of 3-methyl-4-fluoro-acetophenone phenylalanine L(1)H, 3-methyl-4-fluoro-acetophenone alanine L(2)H, 3-methyl-4-fluoro acetophenone tryptophan L(3)H, 3-methyl-4-fluoro-acetophenone valine L(4)H, 3-methyl-4-fluoro-acetophenone isoleucine L(5)H and 3-methyl-4-fluoro-acetophenone glycine L(6)H) have been prepared. It is characterized by elemental analyses, molar conductance measurements and molecular weight determinations. Bonding of these complexes is discussed in terms of their UV-visible, infrared, and nuclear magnetic resonance ((1)H, (13)C, (19)F and (119)Sn NMR) spectral studies. The ligands act as bidentate towards metal ions, via the azomethine nitrogen and deprotonated oxygen of the respective amino acid. Elemental analyses and NMR spectral data of the ligands with their tin(II) complexes agree with their proposed square pyramidal structures. A few representative ligands and their tin complexes have been screened for their antibacterial activities and found to be quite active in this respect.

Micropatterning of proteins and mammalian cells on indium tin oxide

This paper describes a novel surface engineering approach that combines oxygen plasma treatment and electrochemical activation to create micropatterned cocultures on indium tin oxide (ITO) substrates. In this approach, photoresist was patterned onto an ITO substrate modified with poly(ethylene) glycol (PEG) silane. The photoresist served as a stencil during exposure of the surface to oxygen plasma. Upon incubation with collagen (I) solution and removal of the photoresist, the ITO substrate contained collagen regions surrounded by nonfouling PEG silane. Chemical analysis carried out with time-of-flight secondary ion mass spectrometry (ToF-SIMS) at different stages in micropatterned construction verified removal of PEG-silane during oxygen plasma and presence of collagen and PEG molecules on the same surface. Imaging ellipsometry and atomic force microscopy (AFM) were employed to further investigate micropatterned ITO surfaces. Biological application of this micropatterning strategy was demonstrated through selective attachment of mammalian cells on the ITO substrate. Importantly, after seeding the first cell type, the ITO surfaces could be activated by applying negative voltage (-1.4 V vs Ag/AgCl). This resulted in removal of nonfouling PEG layer and allowed to attach another cell type onto the same surface and to create micropatterned cocultures. Micropatterned cocultures of primary hepatocytes and fibroblasts created by this strategy remained functional after 9 days as verified by analysis of hepatic albumin. The novel surface engineering strategy described here may be used to pattern multiple cell types on an optically transparent and conductive substrate and is envisioned to have applications in tissue engineering and biosensing.

Effects of a chayotte (Sechium edule) extract (macerated) on the biochemistry of blood of Wistar rats and on the action against the stannous chloride effect

The use of natural products as medicines has been growing in the entire world. There are concerns that these products may contain potentially toxic ingredients and contaminants such as heavy metals. The labeling of blood constituents with technetium-99m has been influenced by the presence of natural extracts. We evaluated the influence of a chayotte (Sechium edule) extract (100% v/v macerated) on the labeling of blood elements with 99mTc. The animals were treated with the extract during 15 days. Samples of blood were carried out with specific blood biochemistry kits. The present study analyzed the influence ofchayotte in the survival of the strain of Escherichia coli AB1157 submitted to reactive oxygen species induced by stannous chloride. There was a reduction of the lethal effect induced by stannous chloride on the survival of the E. coli culture in the presence of chayotte. The results indicated a decrease in the level of glucose and globulin The effect of the extract could be explained by its metabolic transformation inducing the generation of oxidant metabolites. The culture of bacteria when was treated with stannous chloride and chayotte simultaneously, the extract could be reacting with stannous chloride ions, protecting them against the oxidation avoiding the generation of reactive oxygen species.

Evaluation of oxidative stress in d-serine induced nephrotoxicity

It has been suggested that oxidative stress is involved in d-serine-induced nephrotoxicity. The purpose of this study was to assess if oxidative stress is involved in this experimental model using several approaches including (a) the determination of several markers of oxidative stress and the activity of some antioxidant enzymes in kidney and (b) the use of compounds with antioxidant or prooxidant effects. Rats were sacrificed at several periods of time (from 3 to 24h) after a single i.p. injection of d-serine (400mg/kg). Control rats were injected with l-serine (400mg/kg) and sacrificed 24h after. The following markers were used to assess the temporal aspects of renal damage: (a) urea nitrogen (BUN) and creatinine in blood serum, (b) kidney injury molecule (KIM-1) mRNA levels, and (c) tubular necrotic damage. In addition, creatinine clearance, proteinuria, and urinary excretion of N-acetyl-beta-d-glucosaminidase (NAG) were measured 24h after d-serine injection. Protein carbonyl content, malondialdehyde (MDA), 4-hydroxy-2-nonenal (4-HNE), fluorescent products of lipid peroxidation, reactive oxygen species (ROS), glutathione (GSH) content, and heme oxygenase-1 (HO-1) expression were measured as markers of oxidative stress in the kidney. Additional experiments were performed using the following compounds with antioxidant or pro-oxidant effects before d-serine injection: (a) alpha-phenyl-tert-butyl-nitrone (PBN), a spin trapping agent; (b) 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron(III) (FeTPPS), a soluble complex able to metabolize peroxynitrite; (c) aminotriazole (ATZ), a catalase (CAT) inhibitor; (d) stannous chloride (SnCl(2)), an HO-1 inductor; (e) tin mesoporphyrin (SnMP), an HO inhibitor. In the time-course study, serum creatinine and BUN increased significantly on 15-24 and 20-24h, respectively, and KIM-1 mRNA levels increased significantly on 6-24h. Histological analyses revealed tubular necrosis at 12h. The activity of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase remained unchanged at all times studied. Protein carbonyl content, MDA, 4-HNE, and ROS remained unchanged at all time-points studied. GSH content decreased transiently on 9 and 12h. Interestingly, fluorescent products of lipid peroxidation decreased significantly on 3-24h. HO-1 expression was undetectable by Western blot and the immunohistochemistry studies revealed that the intensity of HO-1 staining was weak. The administration of PBN, FeTPPS, ATZ, SnCl(2), and SnMP did not prevent or enhance renal damage induced by d-serine. Our data taken as a whole suggest that oxidative stress is not involved in the early phase of the nephrotoxicity induced by d-serine.

Sensitivity to Sn2+ of the yeast Saccharomyces cerevisiae depends on general energy metabolism, metal transport, anti-oxidative defences, and DNA repair

Resistance to stannous chloride (SnCl(2)) of the yeast Saccharomyces cerevisiae is a product of several metabolic pathways of this unicellular eukaryote. Sensitivity testing of different null mutants of yeast to SnCl(2) revealed that DNA repair contributes to resistance, mainly via recombinational (Rad52p) and error-prone (Rev3p) steps. Independently, the membrane transporter Atr1p/Snq1p (facilitated transport) contributed significantly to Sn(2+)-resistance whereas absence of ABC export permease Snq2p did not enhance sensitivity. Sensitivity of the superoxide dismutase mutants sod1 and sod2 revealed the importance of these anti-oxidative defence enzymes against Sn(2+)-imposed DNA damage while a catalase-deficient mutant (ctt1) showed wild type (WT) resistance. Lack of transcription factor Yap1, responsible for the oxidative stress response in yeast, led to 3-fold increase in Sn(2+)-sensitivity. While loss of mitochondrial DNA did not change the Sn(2+)-resistance phenotype in any yeast strain, cells with defect cytochrome c oxidase (CcO mutants) showed gradually enhanced sensitivities to Sn(2+) and different spontaneous mutation rates. Highest sensitivity to Sn(2+) was observed when yeast was in exponential growth phase under glucose repression. During diauxic shift (release from glucose repression) Sn(2+)-resistance increased several hundred-fold and fully respiring and resting cells were sensitive only at more than 1000-fold exposure dose, i.e. they survived better at 25 mM than exponentially growing cells at 25 microM Sn(2+). This phenomenon was observed not only in WT but also in already Sn(2+)-sensitive rad52 as well as in sod1, sod2 and CcO mutant strains. The impact of metabolic steps in contribution to Sn(2+)-resistance had the following ranking: Resting WT cells > membrane transporter Snq1p > superoxide dismutases > transcription factor Yap1p >or= DNA repair >> exponentially growing WT cells.

Carbon monoxide protects PC12 cells from peroxynitrite-induced apoptotic death by preventing the depolarization of mitochondrial transmembrane potential

Heme oxygenase-1 (HO-1), the rate-limiting enzyme in catalyzing heme degradation into biliverdin, free iron, and carbon monoxide (CO), serves as a protective enzyme against oxidative and nitrosative stresses. In the present study, we investigated the cytoprotective effects of HO-1 upregulation and its product CO against the peroxynitrite-induced PC12 cell death. PC12 cells treated with 3-morphoinosydonimine (SIN-1), a generator of peroxynitrite (ONOO-), underwent apoptotic cell death as evidenced by dissipation of mitochondrial transmembrane potential (DeltaPsim), release of mitochondrial cytochrome c into cytoplasm, cleavage of poly(ADP-ribose)polymerase and fragmentation of internucleosomal DNA. Pretreatment of PC12 cells with a low non-toxic concentration of SIN-1 (0.5 mM) induced HO-1 expression and abrogated the cell death caused by subsequent challenge with high dose SIN-1 (2.5 mM). Furthermore, pretreatment of PC12 cells with SnCl2, a potent inducer of HO-1 expression, increased endogenous production of CO (HO activity) and rescued the PC12 cells from peroxynitrite-induced apoptosis. The cytoprotective effect of SnCl2 was abolished when the HO activity was inhibited by zinc protoporphyrin IX (ZnPP IX). PC12 cells treated directly with the CO-releasing molecule, tricarbonyldichlororuthenium (II) dimer ([Ru(CO)3Cl2]2) became tolerant to the depolarization of DeltaPsim and apoptosis induced by high dose peroxynitrite. Taken together, these data demonstrate that the adaptive protection against peroxynitrite-induced apoptotic death in PC12 cells is mediated by CO formed as a consequence of HO-1 induction.

Interaction of stannous chloride leads to alteration in DNA, triphosphate nucleotides and isolated bases

Stannous chloride (SnCl2) is a reducing chemical agent used in several man-made products. SnCl2 can generate reactive oxygen species (ROS); therefore, studies have been carried out in order to better understand its damaging action in biological systems. In this work, calf thymus DNA, triphosphate nucleotides and isolated bases were incubated with SnCl2 and the results were analyzed through UV spectrophotometry. The presence of stannous ions altered the absorption spectra of all three isolates. The amount of stannous ions associated to DNA was measured by atomic absorption spectrophotometry. Data showed that more than 40% of the initial SnCl2 concentration was present in the samples. Our results are in accordance with the damaging potential of this salt and present evidence that stannous ions can complex with DNA, inducing ROS in its vicinity, which may be responsible for the observed lesions.

Medicinal potential from in vivo and acclimatized plants of Cleome rosea

Methanolic extracts obtained from different organs of Cleome rosea, collected from its natural habitat and from in vitro-propagated plants, were submitted to in vitro biological assays. Inhibition of nitric oxide (NO) production by J774 macrophages and antioxidant effects by protecting the plasmid DNA from the SnCl(2)-induced damage were evaluated. Extracts from the stem of both origins and leaf of natural plants inhibited NO production. The plasmid DNA strand breaks induced by SnCl(2) were reduced by extracts from either leaf or stem of both sources. On the other hand, root extracts did not show any kind of effects on plasmid DNA, and presented significant toxic effects to J774 cells. The results showed that C. rosea presents medicinal potential and that the acclimatization process reduces the plant toxicity both to plasmid DNA and to J774 cells, suggesting the use of biotechnology tools to obtain elite plants as source of botanical material for pharmacological and phytochemical studies.

The influence of tin compounds on the dynamic properties of liposome membranes: a study using the ESR method

The influence of organic and inorganic compounds of tin on the dynamic properties of liposome membranes obtained in the process of dipalmitoylphosphatidylcholine (DPPC) sonication in distilled water was investigated. This was carried out by means of the spin ESR probe method. The probes were selected in such a way as to penetrate different areas of the membrane (a TEMPO probe, 5-DOXYL stearic acid, 16-DOXYL stearic acid). Four compounds of tin were chosen: three organic ones, (CH(3))(4)Sn, (C(2)H(5))(4)Sn and (C(3)H(7))(3)SnCl, and one inorganic one, SnCl(2). The investigated compounds were added to a liposome dispersion, which was prepared prior to that. The concentration of the admixture was changed within the values from 0 to 10%-mole in proportion to DPPC. The studies indicated that the chlorides of tin display the highest activity in their interaction with liposome membranes. Since these compounds have ionic form in a water solution, the obtained result can mean that this form of admixture has a considerable influence on its activity. Furthermore, it was found that there is a slightly stronger influence of tin compounds with a longer hydrocarbon chain on changes in the probes' spectroscopic parameters.

Influence of administration route on tumor uptake and biodistribution of etoposide loaded solid lipid nanoparticles in Dalton's lymphoma tumor bearing mice

The study evaluates the capability of tripalmitin nanoparticles in enhancing the tumor uptake of etoposide, and the influence of administration route on the biodistribution and tumor uptake of etoposide loaded tripalmitin (ETPL) nanoparticles in Dalton's lymphoma tumor bearing mice. ETPL nanoparticles were prepared by melt-emulsification and high pressure homogenization followed by the spray drying of nanodispersion. Characterization of the nanoparticles was done by particle size analysis, zeta potential measurement and scanning electron microscopy. The size of ETPL nanoparticles was 387 nm and possessed negative charge. Etoposide and ETPL nanoparticles were radiolabeled with 99mTc with high labeling efficiency. The labeled complexes showed good in vitro stability in the presence of DTPA/cysteine and serum stability. Etoposide and ETPL nanoparticles were injected by subcutaneous, intravenous or intraperitoneal routes and their biodistribution and tumor uptake were determined. Subcutaneous injection reduced the distribution of ETPL nanoparticles to all the tissues studied whereas after intraperitoneal injection, the distribution of ETPL nanoparticles to tissues was higher than free etoposide. The intravenous injection resulted in lower concentrations of ETPL nanoparticles in the organs of RES compared to free etoposide. ETPL nanoparticles experienced significantly high brain distribution after intraperitoneal injection indicating its potential use in targeting etoposide to brain tumors. After subcutaneous injection, the tissue distribution of ETPL nanoparticles increased with time indicating their accumulation at the injection site for a longer time. The tumor uptake of both etoposide and ETPL nanoparticles was significantly high after subcutaneous injection (P<0.001) compared to the other routes of administration. The tumor concentration of ETPL nanoparticles after subcutaneous injection was 59 folds higher than that obtained after intravenous and 8 folds higher than after intraperitoneal route at 24 h post-injection. The tumor concentration of ETPL nanoparticles increased with time after subcutaneous injection indicating the slower and progressive penetration from the injection site into the tumor. The study signifies the advantage of incorporating etoposide into tripalmitin nanoparticles in controlling its biodistribution and enhancing the tumor uptake by several folds. The study also reveals that, of the three routes investigated, subcutaneous injection is the route of preference for facilitating high tumor uptake and retention and is likely to have greater antitumor effect resulting in tumor regression.

Labeling efficiency and biodistribution of Technetium-99m labeled nanoparticles: interference by colloidal tin oxide particles

The interference of colloidal tin oxides on the biodistribution of (99m)Technetium radiolabeled chitosan nanoparticles has been overcome by using sodium borohydride instead of commonly used stannous salts as reducing agent for the reduction of (99m)Tc (VII) to lower valency states. Biodistribution of radiolabeled chitosan nanoparticles prepared by using stannous chloride method revealed localization of the radioactivity mainly in the liver and spleen while that of radiolabeled chitosan nanoparticles prepared by using sodium borohydride method manifested the presence of radioactivity in blood up to an extent of 10% even after 2 h. Interestingly, the reduction of radioactivity in the latter case with the progress of time was not manifested through an increase in activity in the liver. Rather, a time dependent increased accumulation of radioactive materials was observed in the stomach. From the results it has been concluded that the biodistribution is strongly influenced by the presence of colloidal particles of tin oxides and (99m)Tc labeled chitosan nanoparticles are RES evading and long circulating in blood when Tc (VII) is reduced by sodium borohydride and not by stannous chloride during radiolabeling process.

Protection of plasmid DNA by a Ginkgo biloba extract from the effects of stannous chloride and the action on the labeling of blood elements with technetium-99m

Ginkgo biloba extract (EGb) is a phytotherapeutic agent used for the treatment of ischemic and neurological disorders. Because the action of this important extract is not fully known, assays using different biological systems need to be performed. Red blood cells (RBC) are labeled with technetium-99m (Tc-99m) and used in nuclear medicine. The labeling depends on a reducing agent, usually stannous chloride (SnCl2). We assessed the effect of different concentrations of EGb on the labeling of blood constituents with Tc-99m, as sodium pertechnetate (3.7 MBq), and on the mobility of a plasmid DNA treated with SnCl2 (1.2 microg/ml) at room temperature. Blood was incubated with EGb before the addition of SnCl2 and Tc-99m. Plasma (P) and RBC were separated and precipitated with trichloroacetic acid, and soluble (SF-P and SF-RBC) and insoluble (IF-P and IF-RBC) fractions were isolated. The plasmid was incubated with Egb, SnCl2 or EGb plus SnCl2 and agarose gel electrophoresis was performed. The gel was stained with ethidium bromide and the DNA bands were visualized by fluorescence in an ultraviolet transilluminator system. EGb decreased the labeling of RBC, IF-P and IF-RBC. The supercoiled form of the plasmid was modified by treatment with SnCl2 and protected by 40 mg/ml EGb. The effect of EGb on the tested systems may be due to its chelating action with the stannous ions and/or pertechnetate or to the capability to generate reactive oxygen species that could oxidize the stannous ion.

Prolactin increases HO-1 expression and induces VEGF production in human macrophages

The pituitary hormone prolactin (PRL) is a multifunctional polypeptide which exerts a role on cell proliferation and may also contribute to cell differentiation. PRL is also produced by immune cells and is regarded as a key component of the neuroendocrine-immune loop and as a local regulator of macrophage response. The involvement of PRL in regulating monocyte/macrophage functions is suggested by the presence of PRL receptors in these cells. It has been shown that PRL possess both angiogenic and antiangiogenic effects. Recently, we revealed that augmentation of HO-1 activity enhances PRL-mediated angiogenesis in human endothelial cells. Since macrophages are key participants in angiogenesis our objective was to investigate the effect of PRL also in human macrophages. In vitro treatment of macrophages with PRL was found to increase both heme oxygenase-1 (HO-1) expression and protein synthesis in a time and dose dependent manner as quantified respectively by reverse-transcriptase real-time polymerase chain reaction and Western blot analysis. PRL-treated macrophages also showed an enhanced release of vascular endothelial growth factor (VEGF) as demonstrated by ELISA assay. Furthermore, to determine whether PRL-induced HO-1 activity was required for VEGF production by macrophages, the effect of PRL on the induction of VEGF was studied in the presence of an inducer stannic chloride (SnCl(2)) and of an inhibitor stannic mesoporphyrin (SnMP) of HO activity. Our observations suggest that PRL may regulate monocyte activation and influences not only immune function but also angiogenesis.

Protective effect of SnCl2 on K2Cr2O7-induced nephrotoxicity in rats: the indispensability of HO-1 preinduction and lack of association with some antioxidant enzymes

We have shown that the ameliorative effect of stannous chloride (SnCl2) pretreatment on potassium dichromate (K2Cr2O7)-induced renal damage 24 h after K2Cr2O7 injection was associated with the induction of heme oxygenase-1 (HO-1). In this work we evaluated: (a) if the protective effect of SnCl2 (given 12 h before K2Cr2O7) is associated with changes in the renal activity of HO-1, superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT) 24 and 48 h after K2Cr2O7 injection, and (b) if HO-1 induction is indispensable before K2Cr2O7 injection. It was found that the protective effect of SnCl2 on renal function was observed both at 24 and 48 h reaching its maximum at 24 h when HO-1 expression was higher. Cu,Zn-SOD, Mn-SOD, and GR activities remained unchanged whereas GPx and CAT activities decreased at 48 h in K2Cr2O7-treated rats. The activity of Cu,Zn-SOD, Mn-SOD, GPx, CAT, and GR was unchanged in the SnCl2-treated rats. To fulfill the objective (b) groups of rats treated with K2Cr2O7 and SnCl2 (given at the same time or 12 h after K2Cr2O7) were studied 24 h after K2Cr2O7-injection. The simultaneous injections of SnCl2 and K2Cr2O7 had no protective effect whereas the injection of SnCl2 12 h after K2Cr2O7 exacerbated renal damage. In conclusion, the protective effect of SnCl2 on K2Cr2O7-induced nephrotoxicity is associated with HO-1 induction and not with other antioxidant enzymes (Cu,Zn-SOD, Mn-SOD, GPx, GR, and CAT) and SnCl2 has a preventive and not a therapeutic effect on renal damage induced by K2Cr2O7.

Influence of stannous chloride on the adhesive properties of Corynebacterium diphtheriae strains

Stannous ion, as a chloride salt, influenced on the survival and adhesive properties of two toxigenic Corynebacterium diphtheriae of the sucrose-fermenting (241 strain) and non-sucrose-fermenting (CDC-E8392 strain) biotypes. Differences in survival fractions suggested differences in susceptibility of strains to bactericidal effect of stannous chloride (SnCl2). A number of 0.3% bacterial cells of 241 strain and 0.02% of CDC-E8392 strain survived after 220 micro l ml(-1) SnCl2 treatment. Results of polystyrene and spontaneous autoaggregation tests showed an increase in hydrophobicity of SnCl2 treated-bacteria. Spontaneous bacterial autoaggregation was induced in the presence of SnCl2. Stannous chloride also induced adherence to glass and totally inhibited the haemagglutinating activity of the non-sucrose-fermenting CDC-E8392 strain (original titer 32). Decrease in haemagglutination was dependent on SnCl2 concentration used. The presence of SnCl2 exerted differences in the expression of diphtheria bacilli surface carbohydrates possibly related with differences in degrees of haemagglutination and adherence to glass. Lectin-binding assays showed increase in the expression of cell surface receptors to the lectin Canavalia ensiformis (Con A) with affinity for mannose-like residues. The occurrence of cell filamentation suggests genotoxicity of SnCl2 to diphtheria bacilli. SnCl2 treatment was capable of modifying cell morphology, hydrophobins and adhesin expression, suggesting ability of C. diphtheriae to withstand oxidative stressing environment. Therefore, the SnCl2, widely used in nuclear medicine as reducing agent in the 99mTc-labelling process, may influence the outcome of bacterial infections.

HO-1 induction attenuates renal damage and oxidative stress induced by K2Cr2O7

Heme oxygenase (HO) is the rate-limiting enzyme in the degradation of heme; its inducible isozyme HO-1 protects against some types of acute tissue injury. The expression and functional role of HO-1 in rats with renal injury induced by potassium dichromate (K(2)Cr(2)O(7)) was investigated in this work. Rats were studied 24 h after a single injection of K(2)Cr(2)O(7). To address the possible protective effect of HO-1 in this experimental model, this enzyme was induced by an injection of stannous chloride (SnCl(2)) 12 h before K(2)Cr(2)O(7) administration. The functional role of HO-1 in K(2)Cr(2)O(7) + SnCl(2)-treated animals was tested by inhibiting HO activity with an injection of zinc (II) protoporphyrin IX (ZnPP) 18 h before K(2)Cr(2)O(7). In K(2)Cr(2)O(7)-treated rats: (i) renal HO-1 content, measured by Western blot, increased 2.6-fold; and, (ii) renal nitrotyrosine and protein carbonyl content, markers of oxidative stress, increased 3.5- and 1.36-fold, respectively. Renal damage and oxidative stress were ameliorated and HO-1 content was increased in the K(2)Cr(2)O(7) + SnCl(2) group. The attenuation of renal injury and oxidative stress was lost by the inhibition of HO activity in K(2)Cr(2)O(7) + SnCl(2) + ZnPP-treated animals. Our data suggest that HO-1 overexpression induced by SnCl(2) is responsible for the attenuation of renal damage and oxidative stress induced by K(2)Cr(2)O(7).

Heme oxygenase-1 localization in the rat nephron

BACKGROUND/AIMS

Renal tubules undergo oxidative injury in various nephropathies. It is unknown whether tubular cells possess mechanisms to attenuate this form of injury. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, may provide such a mechanism by reducing levels of free heme, a prooxidant molecule, and by limiting activity of heme-containing prooxidant enzymes. Determination of the distribution of HO-1 in the nephron may identify those segments where HO-1 can afford protection against oxidative injury.

METHODS

Rats were injected subcutaneously with two different inducers of HO-1: Stannous chloride and cobalt protoporphyrin. At completion of injections, frozen sections of kidneys were stained for HO-1 using a biotin-conjugated monoclonal anti-HO-1 antibody. To identify the origin of tubules staining positive for HO-1, Tetragonolobus purpureas (TP)-derived lectin and Arachnis hypogaea (AH)-derived lectin were applied to sequential sections of the kidney cortex.

RESULTS

In rats injected with either HO-1 inducer, HO-1 was immunolocalized in tubules but not in glomeruli. Staining of sequential sections with TP-derived lectin, which binds mainly to proximal tubular cells, was negative in the tubules that stained positive for HO-1. Staining of sequential sections with AH-derived lectin, which binds mainly to distal and collecting tubular cells, was positive in those tubules that were also positive for HO-1.

CONCLUSIONS

In kidneys of rats injected with inducers of HO-1, distal and collecting tubular cells were identified as the main segments of the nephron that express HO-1. We suggest that the distal nephron, by expressing HO-1, may be less vulnerable to oxidative injury.

Protective effect of HO-1 against oxidative stress in human hepatoma cell line (HepG2) is independent of telomerase enzyme activity

Heme oxygenase-1 (HO-1) is a stress response protein and its induction is associated with protection against oxidative stress. Cell survival during exposure to environmental stresses is associated with elevation of HO-1. Telomerase plays an important role in cell proliferation and immortalization. Our objective was to determine whether the adaptive cellular response to survive exposure to environmental stresses is dependent on expression of HO-1 and telomerase activity in hepatoma cell line (HepG2). Exposure of HepG2 to oxidants, H(2)O(2) (100 microM), as well as HO-1 inducers, heme (10 microM) and stannic chloride (SnCl(2)) (10 microM), resulted in an increased HO-1 mRNA, protein and total HO activity. On the other hand, HO activity was inhibited by addition of stannic mesoporphyrin (SnMP) (10 microM). These effects were brought about without altering endogenous HO-2 protein levels. Telomerase activity was not affected by oxidants, inducers of HO-1 or inhibitors of HO activity. Similarly, the catalytic subunit of telomerase enzyme human telomerase reverse transcriptase (hTERT), which is considered as the major regulator of telomerase activity, was not affected by oxidants, heme and H(2)O(2), or downregulation of HO gene activity by SnMP. This study demonstrates, for the first time, that induction of HO-1 gene mediates protection against oxidants and increases cell survival by a mechanism independent of telomerase enzyme activity. Suppression of HO activity by SnMP decreased cell resistance to oxidant stressors without altering telomerase activity.

Effect of an extract of cauliflower (leaf) on the labeling of blood elements with technetium-99m and on the survival of Escherichia coli AB1157 submitted to the treatment with stannous chloride

The labeling of red blood cells (RBC) with technetium-99m (99mTc) depends on a reducing agent and stannous chloride (SnCl(2)) and is widely utilized. This labeling may also be altered by drugs, and SnCl(2) reduces the survival of Escherichia coli cultures. Cauliflower (Brassica oleracea L. var. botrytis) is used in folk medicine and we evaluated its influence on (i) the labeling of blood elements with 99mTc, and (ii) on the survival of an E. coli strain. Blood was withdrawn from rats that drank the extract of cauliflower (15 days). Blood was incubated with SnCl(2) and with 99mTc, as sodium pertechnetate, centrifuged and plasma (P) and RBC were isolated. Samples of P and RBC were also precipitated, centrifuged and soluble and insoluble fractions isolated. E. coli culture was treated with SnCl(2) in the presence of cauliflower. The extract of cauliflower did not alter the fixation of 99mTc on blood fractions; however, it abolished the lethal effect of SnCl(2) on the E. coli culture. We suggest that the substances present in the extract of cauliflower probably, would have redox property with different mechanisms of action. The oxidant action of the substances of the extract would not be strong enough to oxidise the stannous ions altering the 99mTc-labeling. However, the referred substances could oxidise these ions sufficiently to protect the E. coli culture against the lethal effect of the stannous ion.

Preoperative stress conditioning prevents paralysis after experimental aortic surgery: increased heat shock protein content is associated with ischemic tolerance of the spinal cord

BACKGROUND

All forms of surgical therapy are stressful and injurious. The problems of paralysis, renal dysfunction, and colonic ischemia associated with aortic occlusion are due to acute ischemia-reperfusion injury at the cellular level. Acute-anterior spinal cord ischemia is the most devastating outcome of these iatrogenic-ischemic events. The majority of surgical procedures are performed electively and therefore provide an opportunity to preoperatively condition the patient to minimize these ischemia-related morbidities.

OBJECTIVES

We sought to determine whether acute spinal cord injury associated with aortic occlusion can be prevented by induction of the cellular stress response by means of preoperative administration of whole-body hyperthermia or stannous chloride.

METHODS

The study consisted of an experimental rabbit model of infrarenal aortic occlusion for 20 minutes at normothermic body temperature.

RESULTS

Control rabbits experienced an 88% (7/8) incidence of paralysis after spinal cord ischemia induced by 20 minutes of aortic occlusion, whereas animals treated preoperatively with either whole-body hyperthermia (0/9) or stannous chloride (0/4) never became paralyzed (P <.001 for control vs treated groups). Ischemic protection of the spinal cord was associated with increased content of stress proteins within tissues of pretreated animals.

CONCLUSION

Prior induction of the heat shock response in the whole animal will increase the content of stress proteins within the spinal cord and other tissues and result in the prevention of hind-limb paralysis associated with aortic occlusion. We have designated the preoperative induction of the cellular stress response for the prevention of ischemic tissue injury stress conditioning. We suggest that stress-conditioning protocols represent the opportunity to practice preventative medicine at the molecular level.

Regulation of cyclooxygenase- and cytochrome p450-derived eicosanoids by heme oxygenase in the rat kidney

Heme oxygenase enzymes (HO-1 and HO-2) catalyze the conversion of heme to biliverdin, free iron, and carbon monoxide (CO). Heme and products derived from its metabolism potentially influence renal function and blood pressure by affecting the expression and/or activity of hemeproteins, including cytochrome P450 (CYP4A) monooxygenases and cyclooxygenases (COX-1 and COX-2). We studied HO isoform expression and examined the effect of HO-1 induction by SnCl(2) on CYP4A and COX expression and activity in the rat kidney. HO-1 protein levels in kidney tissues from untreated rats were barely detectable, whereas HO-2 protein was expressed in all kidney structures examined and its levels were higher in the outer medulla followed by the inner medulla/papilla and cortex. HO-2 expression along the nephron followed its regional distribution, ie, the highest levels were detected in the medullary thick ascending limb (mTAL) and inner medullary collecting ducts followed by proximal tubules. SnCl(2) Treatment did not significantly affect HO-2 expression or distribution; however, it markedly increased HO-1 protein in the inner and outer medulla, specifically, in the inner medullary collecting ducts and mTAL. CYP4A expression and 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis were the highest in the outer medulla followed by the cortex and inner medulla/papilla. SnCl(2) treatment reduced cortical and inner medullary CYP4A protein levels by 60% and 50% and inhibited 20-HETE synthesis by 90% and 60%, respectively. Despite a significant induction of HO-1 protein in the outer medulla, CYP4A expression and 20-HETE synthesis were hardly affected. SnCl(2) treatment did not affect COX-1 expression but markedly reduced cortical and medullary COX-2 protein levels. We conclude that HO isoform expression is segmented within the kidney and along the nephron and that treatment with an HO-1 inducer suppressed the levels of CYP4A and COX-2 proteins in a tissue-specific manner with concomitant effects on their activity. Such interactions may play an important role in the regulation of renal function.

[No influence of propanolol, cyclosporine, adriamycin, and nifedipine on the in vitro labelling of erythrocytes]

The objective of this work was to study the potential interference of propanolol, cyclosporine, adriamycin, and nifedipine with the in vitro labelling of erythrocytes.

MATERIALS AND METHODS

20-ml blood specimens were collected from 40 healthy volunteers who had not taken any drug in the week before collection. 2.0-ml alliquots were incubated at 37 C with different concentrations of the drugs for 30 minutes. In all cases, a control group was incubated with saline (0.9%). Two labelling methods were used: 1) EDTA method, in which 60 l of SnCl2 (10.2 g/ml), 2.0 ml of saline, 0.2 ml EDTA 2.2%, and 7.4 MBq of Na99mTcO4 were added, and the mix was incubated for 5 minutes. 2) The hypochlorite method, in which specimens were initially incubated with SnCl2 (10.2 g/ml) for 5 minutes. Then, 40 l of 1% hypochlorite and all the reagents described in the previous method were added. With both methods, erythrocytes were separated by centrifugation and the labelling yield was estimated.

RESULTS

RESULTS did not show significant differences between the yield of the control group labelling and the yield of the different concentrations of the tested drugs. Also, significant differences were not observed the two labelling methods used.

CONCLUSION

Both labelling methods are useful for the in vitro preparation of 99mTc-erythrocytes. The absence of significant differences in the labelling yield indicates that in vitro interferences observed by some investigators are associated with concentrations exceeding therapeutic plasma levels. On the other hand, the reported in vivo interferences might be due to the presence of active catabolites and/or interference between different drugs.

[The effects of fluoride-containing trace element agents on the growth of mutants of S. mutans]

OBJECTIVE

To compare the influence of 6 trace element agents containing fluoride versus 6 trace element agents not containing fluoride on the growth of mutants of S. mutans and detect the interaction between fluoride and trace elements.

METHODS

Six trace element agents containing fluoride [SnF2, ZnF2, SrF2, LaF2, (NH3)2MoF8, NaF] and 6 trace element agents not containing fluoride [SnCl2, SrCl2, LaCl2, ZnAc2, (NH3)2MoO4, NaCl] were selected. The continuous anaerobic cultivating technique and the absorbency of bacteria liquid and the count of bacteria were used to assess the effects of different agents on the growth of S. mutans.

RESULTS

NaF, SnF2, SnCl2, ZnF2, ZnAc2, (NH3)2MoF8 and (NH3)2MoO4 were found to have strong inhibition effects on the growth of mutant of S. mutans(P < 0.01). SnF2 had more stronger inhibition effects than SnCl2; ZnF2 had more stronger inhibition effects than ZnAc2, no significant differences were seen between (NH3)2MoF8 and (NH3)2MoO4. SnF2 and ZnF2 had most potent inhibition effects(P < 0.01). No significant differences were observed between SrF2, SrCl2, LaCl2, LaF2, NaCl and the control groups(P > 0.05).

CONCLUSION

The agents containing fluoride and trace elements, such as stannum and zinc had the effects of prohibiting the growth of mutant of S. mutans, As far as caries prevention is concerned, the agents containing both fluoride and trace elements are more effective than mono-fluoride, the potential mechanism may be the synergistic action between fluoride and trace elements.

Potentiation by stannous chloride of calcium entry into osteoblastic MC3T3-E1 cells through voltage-dependent L-type calcium channels

The present study was undertaken to confirm that L-type Ca(2+) channels are involved in Ca(2+) entry into osteoblastic MC3T3-E1 cells and to examine the effect of SnCl2, a Ca(2+)]-channel activator, on the intracellular Ca(2+)concentration ([Ca(2+)]i). High K(+)concentration-dependently raised the [Ca(2+)]i. All of the L-type Ca(2+)channel blockers used here, such as nifedipine, nicardipine, verapamil, and diltiazem, and CdCl2 (a non-selective blocker) inhibited the high K(+)-induced [Ca(2+)]i rise, but v-conotoxin GVIA (an N-type blocker) and NiCl2(a T-type blocker) had no effect. Application of SnCl2 alone did not change the [Ca(2+)]i. However, in the presence of high K(+), SnCl2 enhanced the high K(+)-induced [Ca(2+)]i rise, which was inhibited by Ca(2+)]-free medium or nifedipine. In the case where high K(+)was applied prior to SnCl2, SnCl2 alone raised the [Ca(2+)]i by itself. In conclusion, MC3T3-E1 cells possess the voltage-dependent L-type Ca(2+)] channels and SnCl2 facilitates the Ca(2+) entry through the L-type ones under the condition of the membrane depolarization. There is the possibility that Ca(2+) release from intracellular Ca(2+) stores is involved in the action of SnCl2.

New evidence for the mechanism of the tin(II) chloride catalyzed reactions of vicinal diols with diazodiphenylmethane in 1,2-dimethoxyethane

A kinetic study of the tin(II) chloride catalyzed reaction of diazodiphenylmethane with ethylene glycol in dimethoxyethane is reported. The preparation and characterization of ethylene glycol monodiphenylmethyl ether, the main product from this reaction, is also reported as well as the preparation of the two diphenylmethyl monoethers of methyl 4,6-O-benzylidene-alpha-D-glucopyranoside. An unexpected relationship between the concentration of ethylene glycol and the pseudo first-order rate constant, k', was observed in these reactions. For low concentrations of ethylene glycol (below 0.06 M), k' increases with increasing concentration of the diol. This trend is reversed for high concentrations of ethylene glycol (from about 0.06 to about 0.2 M). The apparent rate constant was also inversely related to the initial concentration of diazodiphenylmethane for the concentrations investigated. These results make the previously proposed involvement of a 1,3,2-dioxastannolane intermediate very unlikely [Petursson, S.; Webber, J.M. Carbohydr. Res. 1982, 103, 41-52]. The results suggest that more likely intermediates for these reactions involve tin(II) chloride complexes in a dynamic equilibrium with the diol.

Effects of heat shock, stannous chloride, and gallium nitrate on the rat inflammatory response

Heat and a variety of other stressors cause mammalian cells and tissues to acquire cytoprotection. This transient state of altered cellular physiology is nonproliferative and antiapoptotic. In this study, male Wistar rats were stress conditioned with either stannous chloride or gallium nitrate, which have immunosuppressive effects in vivo and in vitro, or heat shock, the most intensively studied inducer of cytoprotection. The early stages of inflammation in response to topical suffusion of mesentery tissue with formyl-methionyl-leucyl-phenylalanine (FMLP) were monitored using intravital microscopy. Microvascular hemodynamics (venular diameter, red blood cell velocity [Vrbc], white blood cell [WBC] flux, and leukocyte-endothelial adhesion [LEA]) were used as indicators of inflammation, and tissue levels of inducible Hsp70, determined using immunoblot assays, provided a marker of cytoprotection. None of the experimental treatments blocked decreases in WBC flux during FMLP suffusion, an indicator of increased low-affinity interactions between leukocytes and vascular endothelium known as rolling adhesion. During FMLP suffusion LEA, an indicator of firm attachment between leukocytes and vascular endothelial cells increased in placebo and gallium nitrate-treated animals but not in heat- and stannous chloride-treated animals, an anti-inflammatory effect. Hsp70 was not detected in aortic tissue from placebo and gallium nitrate-treated animals, indicating that Hsp70-dependent cytoprotection was not present. In contrast, Hsp70 was detected in aortic tissues from heat- and stannous chloride-treated animals, indicating that these tissues were in a cytoprotected state that was also an anti-inflammatory state.