Antimicrobial Blue Light Inactivation of Gram-Negative Pathogens in Biofilms: In Vitro and In Vivo Studies.

BACKGROUND: Biofilms affect >80% bacterial infections in human and are usually difficult to eradicate because of their inherent drug resistance. METHODS: We investigated the effectiveness of antimicrobial blue light (aBL) (wavelength, 415 nm) for inactivating Acinetobacter baumannii or Pseudomonas aeruginosa biofilms in 96-well microplates or infected mouse burn wounds. RESULTS: In vitro, in 96-well microplates, exposure of 24-hour-old and 72-hour-old A. baumannii biofilms to 432 J/cm(2) aBL resulted in inactivation of 3.59 log10 and 3.18 log10 colony-forming units (CFU), respectively. For P. aeruginosa biofilms, similar levels of inactivation-3.02 log10 and 3.12 log10 CFU, respectively-were achieved. In mouse burn wounds infected with 5 × 10(6) CFU ofA. baumannii, approximately 360 J/cm(2) and 540 J/cm(2) aBL was required to inactivate 3 log10 CFU in biofilms when delivered 24 and 48 hours, respectively, after bacterial inoculation. High-performance liquid chromatography analysis revealed the presence of endogenous porphyrins in both A. baumannii and P. aeruginosa TUNEL assay detected no apoptotic cells in aBL-irradiated mouse skin at up to 24 hours after aBL exposure (540 J/cm(2)). CONCLUSIONS: aBL has antimicrobial activity in biofilms ofA. baumannii and P. aeruginosa and is a potential therapeutic approach for biofilm-related infections.

Antimicrobial blue light inactivation of Pseudomonas aeruginosa by photo-excitation of endogenous porphyrins: In vitro and in vivo studies.

Pseudomonas aeruginosa is among the most common pathogens that cause nosocomial infections and is responsible for about 10% of all hospital-acquired infections. In the present study, we investigated the potential development of tolerance of P. aeruginosa to antimicrobial blue light by carrying 10 successive cycles of sublethal blue light inactivation. The high-performance liquid chromatographic (HPLC) analysis was performed to identify endogenous porphyrins in P. aeruginosa cells. In addition, we tested the effectiveness of antimicrobial blue light in a mouse model of nonlethal skin abrasion infection by using a bioluminescent strain of P. aeruginosa. The results demonstrated that no tolerance was developed to antimicrobial blue light in P. aeruginosa after 10 cycles of sub-lethal inactivation. HPLC analysis showed that P. aeruginosa is capable of producing endogenous porphyrins in particularly, coproporphyrin III, which are assumed to be responsible for the photodynamic effects of blue light alone. P. aeruginosa infection was eradicated by antimicrobial blue light alone (48 J/cm(2) ) without any added photosensitizer molecules in the mouse model. In conclusion, endogenous photosensitization using blue light should gain considerable attention as an effective and safe alternative antimicrobial therapy for skin infections. Lasers Surg. Med. 48:562-568, 2016. © 2016 Wiley Periodicals, Inc.

Predictive value of α-synuclein expression in peripheral blood of multiple sclerosis patients: A two-dimensional assessment of a selected biomarker.

INTRODUCTION: Our study aimed to evaluate whether assessing α-synuclein expression levels in blood samples could provide a reliable and straightforward alternative to existing diagnostic and prognostic methods for neurodegenerative disorders, including multiple sclerosis (MS). We specifically investigated if α-synuclein and IL-6 expression levels from serum and peripheral blood mononuclear cells (PBMCs) could accurately predict MS severity in patients using a two-dimensional approach. METHODS: We designed a case-control study to analyze the expression of α-synuclein and IL-6 in the peripheral blood of an MS patient group (n = 51) and a control group (n = 51). We statistically evaluated the PBMCs and serum profiles of α-synuclein and IL-6 in MS patients, along with their age of onset, disease duration, tobacco exposure, and Expanded Disability Status Scale (EDSS) score, using SPSS V22.0 software and GraphPad Prism V9.0. RESULTS: Our findings indicate that α-synuclein production was significantly downregulated in MS patients. Principal component analysis also revealed distinct profiles between MS patients and controls. PBMCs and serum profiles of α-synuclein correlated with the EDSS score, suggesting that disease severity can be predicted using α-synuclein profiles. Moreover, α-synuclein showed a significant correlation with IL-6 and age of onset. Lastly, receiver operating characteristic curves of PBMCs and serum activity of α-synuclein profiles displayed discrimination with area under the curve values of 0.856 and 0.705, respectively. CONCLUSION: Our results imply that measuring α-synuclein levels in both serum and PBMCs could be a valuable method for diagnosing and predicting MS severity, potentially serving as a non-invasive biomarker for the disease.

Antimicrobial Photodynamic Therapy against Escherichia coli and Staphylococcus aureus Using Nanoemulsion-Encapsulated Zinc Phthalocyanine.

Multidrug-resistant microorganisms have become a significant public health threat, and traditional antibiotics are becoming ineffective. Photodynamic therapy (PDT) is a promising alternative that utilizes photosensitizers and light to produce Reactive Oxygen Species (ROS) that can kill microorganisms. Zinc phthalocyanine (ZnPc) is a promising photosensitizer due to its strong affinity for encapsulation in nanoemulsions and its antimicrobial properties. In this study, nanoemulsion was prepared using Miglyol 812N, a surfactant, and distilled water to dissolve hydrophobic drugs such as ZnPc. The nanoemulsion was characterized by its particle size, polydispersity index, Transmission Electron Microscope and Zeta potential, and the results showed that it was an efficient nanocarrier system that facilitated the solubilization of hydrophobic drugs in water. The use of ZnPc encapsulated in the nanoemulsion produced through the spontaneous emulsification method resulted in a significant reduction in cell survival percentages of gram-positive Staphylococcus aureus and gram-negative Escherichia coli by 85% and 75%, respectively. This may be attributed to the more complex cell membrane structure of E. coli compared to S. aureus. This demonstrates the potential of nanoemulsion-based PDT as an effective alternative to traditional antibiotics for treating multidrug-resistant microorganisms.

Potential of nanotechnology to replace cancer stem cells.

Stem cells, which were initially identified in the 1900s, are distinct cells with the potential to replenish themselves as well as differentiate into specialised cells with certain forms and functions. Cancer stem cells play a significant role in the growth and recurrence of the tumours and, similar to normal stem cells, are capable of proliferating and differentiating. Traditional cancer treatments are ineffective against cancer stem cells, which leads to tumour regrowth. Cancer stem cells are thought to emerge as a result of epithelial-to-mesenchymal transition pathways. Brain, prostate, pancreatic, blood, ovarian, lung, liver, melanomas, AML, and breast cancer stem cells are among the most prevalent cancer forms. This review aims to comprehend the possibility of using specific forms of nanotechnology to replace cancer stem cells. In terms of nanotechnology, magnetic nanoparticles can deliver medications, especially to the target region without harming healthy cells, and they are biocompatible. In order to kill glioma cancer stem cells, the gold nanoparticles bond with DNA and function as radio sensitizers. In contrast, liposomes can circulate and traverse biological membranes and exhibit high therapeutic efficacy, precise targeting, and better drug release. Similar to carbon nanotubes, grapheme, and grapheme oxide, these substances can be delivered specifically when utilized in photothermal therapy. Recent treatments including signaling pathways and indicators targeted by nanoparticles are being researched. Future research in nanotechnology aims to develop more effective and targeted medicinal approaches. The results of the current investigation also showed that this technology's utilization will improve medical therapy and treatment.

Evaluation of photodynamic treatment using aluminum phthalocyanine tetrasulfonate chloride as a photosensitizer: new approach.

Photodynamic therapy (PDT) has been the subject of several clinical studies. Evidence to date suggests that direct cell death may involve apoptosis. T(24) cells (bladder cancer cells, ATCC-Nr. HTB-4) were subjected to PDT with aluminum phthalocyanine tetrasulfonate chloride (AlS(4)Pc-Cl) and red laser light at 670 nm. Morphological changes after PDT were visualized under confocal microscopy. Raman microspectroscopy is considered as one of the newly established methods used for the detection of cytochrome c as an apoptotic marker. Results showed that PDT treated T(24) cells seem to undergo apoptosis after irradiation with 3 J cm(-2). Cytochrome c could not be detected from cells incubated with AlS(4)Pc-Cl using Raman spectroscopy whereas AlS(4)Pc-Cl seems to interfere with the Raman spectrum of cytochrome c.

The analysis of dynamic gene expression patterns in peripheral blood of multiple sclerosis patients indicates possible diagnostic and prognostic biomarkers.

INTRODUCTION: Among numerous invasive procedures for the research of biomarkers, blood-based indicators are regarded as marginally non-invasive procedures in the diagnosis and prognosis of demyelinating disorders, including multiple sclerosis (MS). In this study, we looked into the blood-derived gene expression profiles of patients with multiple sclerosis to investigate their clinical traits and linked them with dysregulated gene expressions to establish diagnostic and prognostic indicators. METHODS: We included 51 patients with relapsing-remitting MS (RRMS, n = 31), clinically isolated syndrome (CIS, n = 12), primary progressive MS (PPMS, n = 8) and a control group (n = 51). Using correlational analysis, the transcriptional patterns of chosen gene panels were examined and subsequently related with disease duration and the expanded disease disability score (EDSS). In addition, principal component analysis, univariate regression, and logistic regression analysis were employed to highlight distinct profiles of genes and prognosticate the excellent biomarkers of this illness. RESULTS: Our findings demonstrated that neurofilament light (NEFL), tumor necrosis factor α (TNF-α), Tau, and clusterin (CLU) were revealed to be increased in recruited patients, whereas the presenilin-1 (PSEN1) and cell-surface glycoprotein-44 (CD44) were downregulated. Principal Component Analysis revealed distinct patterns between the MS and control groups. Correlation analysis indicated co-dependent dysregulated genes and their differential expression with clinical findings. Furthermore, logistic regression demonstrated that Clusterin (AUC=0.940), NEFL (AUC=0.775), TNF-α (AUC=0.817), Tau (AUC=0.749), PSEN1 (AUC=0.6913), and CD44 (AUC=0.832) had diagnostic relevance. Following the univariate linear regression, a significant regression equation was found between EDSS and IGF-1 (R2 adj = 0.10844; p= 0.0060), APP (R2 adj = 0.1107; p= 0.0098), and PSEN1 (R2 adj = 0.1266; p=0.0102). CONCLUSION: This study exhibits dynamic gene expression patterns that represent the significance of specified genes that are prospective diagnostic and prognostic biomarkers for multiple sclerosis.

Zinc Oxide Nanoparticle-Loaded Electrospun Polyvinylidene Fluoride Nanofibers as a Potential Face Protector against Respiratory Viral Infections.

ZnO-NPs loaded polyvinylidene fluoride (PVDF) composite nanofibers were fabricated by electrospinning and optimized using different concentrations (0, 2, and 5 wt %) of ZnO-NPs. Characterization techniques, for example, FTIR, SEM, XRD, and tensile strength analysis were performed to analyze the composite nanofibers. Molecular docking calculations were performed to evaluate the binding affinity of PVDF and ZnO@PVDF against the hexon protein of adenovirus (PDB ID: 6CGV). The cytotoxicity of tested materials was evaluated using MTT assay, and nontoxic doses subjected to antiviral evaluation against human adenovirus type-5 as a human respiratory model were analyzed using quantitative polymerase chain reaction assay. IC50 values were obtained at concentrations of 0, 2, and 5% of ZnO-loaded PVDF; however, no cytotoxic effect was detected for the nanofibers. In 5% ZnO-loaded PVDF nanofibers, both the viral entry and its replication were inhibited in both the adsorption and virucidal antiviral mechanisms, making it a potent antiviral filter/mask. Therefore, ZnO-loaded PVDF nanofiber is a potentially prototyped filter embedded in a commercial face mask for use as an antiviral mask with a pronounced potential to reduce the spreading of infectious respiratory diseases, for example, COVID-19 and its analogues.

Inhibition of SARS-CoV-2 spike protein entry using biologically modified polyacrylonitrile nanofibers: in vitro study towards specific antiviral masks.

With the increase of the contagiousness rates of Coronavirus disease (COVID-19), new strategies are needed to halt virus spread. Blocking virus entry by capturing its spike (S) protein is one of the effective approaches that could help in eliminating or reducing transmission rate of viruses. Herein, we aim to develop a nanofiber-based filter for protective face masks, composed of polyacrylonitrile (PAN) nanofibers (NFs)-loaded with Angiotensin Converting Enzyme-2 (ACE-2) for capturing the spike protein of severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) and blocking its entry. Docking simulations were performed to evaluate interactions of PAN with target proteins of both SARS-CoV-2 and Human Adenovirus type 5 (ADV-5) which was used as an in vitro model of human respiratory viruses. Scanning electron microscopy (SEM) and Fourier transformed infrared (FT-IR) spectroscopy was employed to investigate the surface morphology and to analyze the functional groups of the NFs, respectively. The mechanical properties of the electrospun NFs were investigated, according to which the tensile strengths of PAN and modified PAN NFs were 4.9 ± 1.2 GPa and 4.5 GPa. Additionally, elongations at break were 25 ± 2.5% to 24 ± 1.48% for PAN and modified PAN NFs. The tensile strength test showed good mechanical characteristics of the NFs. The ACE-2-loaded NFs were shown to be safe, with promising antiviral activity towards ADV-5. Meanwhile, a binding affinity study between the spike protein and ACE-2 was performed and the dissociation constant (K D) was found to be 1.1 nM. Accordingly, the developed antiviral filters have a potential role to stand as a base for combating various human respiratory viruses.

Electrospun PVA/hyaluronic acid/L-arginine nanofibers for wound healing applications: Nanofibers optimization and in vitro bioevaluation.

Hyaluronic acid (HA) based nanofibers (NFs) represented a novel class of bioactive wound dressings that have a vital role in wound management due to their unique properties as an extracellular-matrix and accelerating wound healing. Novel L-arginine-loaded citric acid crosslinked PVA-HA NFs were fabricated by electrospinning and proposed for potential wound healing purposes. However, poor mechanical properties of HA NFs might limit its biological usage, thus this study aims to develop reinforced PVA/HA NFs by incorporation of cellulose nanocrystals (CNCs) as nanofiller and loading L-arginine as wound healing accelerator. Results revealed that incorporation of CNCs into PVA/HA significantly improved mechanical and swelling properties of NFs, compared to CNC-free NFs. Biological performance of NFs was evaluated on normal human skin melanocyte (HFB-4) and lung fibroblast (WI38) cell-lines. PVA/HA/CNC/L-arginine NFs exhibited excellent hemocompatibility, high protein adsorption, outstanding proliferative and adhesive potential on HFB-4 cells expressed by high wound gap-closure 99.9% after 48 h of exposure. Released arginine from PVA/HA/CNC NFs showed sustained release about 46.5% and ~90% after 24 h and 48 h, respectively. Briefly, PVA/HA/CNCs/L-arginine showed adequate antibacterial activity especially against Klebsiella pneumonia, as an acute popular pathogen causing a skin infection. These results indicate that PVA/HA/CNC/L-arginine could act as promising and multifunctional wound dressings.

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.

Green synthesis and biological activity of silver-curcumin nanoconjugates.

AIM: There is an urgent need to develop alternative antimicrobial agents and, one of which is via the use of nanotechnology. Green synthetic routes are recently being replaced for nanoparticles preparation. Methods results: Silver-curcumin nanoconjugates (Ag-CurNCs) were prepared in an eco-friendly method. The prepared nanomaterials were characterized and the photostability was studied under the influence of UV irradiation. Results showed that, the conjugation between curcumin and silver in the nanoform improve the photostability of curcumin. Cytotoxicity was studied on different skin cell lines, and antibacterial activity was investigated against Escherichia coli. Results revealed the antibacterial activity of the prepared nanoconjugates (Ag-CurNCs) with minimal toxicity to skin cells. CONCLUSION: Silver nanoparticles improve the photostability and antibacterial activity of curcumin, while curcumin helps in preparing biocompatible silver nanoparticles.

Fluorescence-based CdTe nanosensor for sensitive detection of cytochrome C.

Cytochrome c (Cyt c) is commonly used as intrinsic biomarker for several characteristics of the cell such as respiration, energy level and apoptosis. In the present study a simple colorimetric sensor should be developed and tested for the real-time detection of Cyt c in living cells. We synthesized cadmium telluride quantum dots (CdTe QDs) capped with thioglycolic acid (TGA) as a fluorometric Cyt c nanosensor. The synthesized TGA/CdTe QDs nanosensor was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and absorption as well as fluorescence spectrophotometry. We investigated the developed TGA/CdTe QDs sensor with regard to its applicability in the fluorometric detection of Cyt c. Results showed that the TGA/CdTe QDs could be used as a sensitive fluorescence probe for the quantification of different concentrations of Cyt c ranging from 0.5 - 2.5µM. Increased binding of QDs to Cyt c results in decreasing fluorescence. The fluorescence of the QDs is inversely correlated to the Cyt c concentration. Based on these data, a standard curve up to 2.5µM Cyt c was established. Moreover, the developed nanosensor was applied in different concentrations on primary human dermal fibroblasts. Results showed that TGA/CdTe QDs were taken up by cells and could be visualized by fluorescence microscopy. Quantification of Cyt c within living cells via QDs is, however, influenced by various factors such as cell damage, QD aggregation or the level of reactive oxygen species, which have to be taken into account.

Exploiting biosynthetic gold nanoparticles for improving the aqueous solubility of metal-free phthalocyanine as biocompatible PDT agent.

Increasing the limit of dispersion of metal-free phthalocyanine (H2Pc) in an aqueous medium using biosynthetic gold nanoparticles for photodynamic therapy (PDT) is investigated. Gold nanoparticles (Au NPs) are biosynthesized in one step using Potatoes (Solanum tuberosum) extract and are characterized by UV/VIS spectrophotometry, Fourier transformer infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The metal-free phthalocyanine is conjugated to the surface of the gold nanoparticles in a side to side regime through the secondary amine groups of H2Pc. The clear violet solution of phthalocyanine-gold (Pc-Au) nanoconjugates is investigated by UV-VIS, FTIR and TEM techniques. Disappearance of the absorption band of the secondary amine in the Pc-Au nanoconjugates compared to that of the parent H2Pc, and detection of the absorption band of H2Pc in the aqueous medium confirmed the dispersion of H2Pc and consequently the loading of H2Pc on the surface of Au NPs. The cytotoxic effect of biosynthetic gold nanoparticles and Pc-Au nanoconjugates compared to chemically synthesized gold nanoparticles on buffalo epithelial cells has been studied in vitro. Interestingly, the results showed that the biosynthetic Au NPs as well as Pc-Au nanoconjugates have no effect on buffalo epithelial cells viability, which indicating their biocompatibility contrary to the chemically synthesized Au NPs. This work will open the door, for the first time, for using H2Pc suspended in water for PDT and other phototherapeutic applications.

A new biocompatible nanocomposite as a promising constituent of sunscreens.

Skin naturally uses antioxidants to protect itself from the damaging effects of sunlight. If this is not sufficient, other measures have to be taken. Like this, hydroxyapatite has the potential to be applied as an active constituent of sunscreens since calcium phosphate absorbs in the ultraviolet region (UV). The objective of the present work was to synthesize a hydroxyapatite-ascorbic acid nanocomposite (HAp/AA-NC) as a new biocompatible constituent of sunscreens and to test its efficiency with skin cell models. The synthesized HAp/AA-NC was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, absorption spectrophotometry and X-ray diffraction analysis. The protective effect of the construct was tested with respect to viability and intracellular reactive oxygen species (ROS) generation of primary human dermal fibroblasts (SKIN) and human epidermal keratinocytes (HaCaT). Both cell lines were irradiated with UV light, λmax=254 nm with a fluence of 25 mJ cm(-2) to mimic the effect of UV radiation of sunlight on the skin. Results showed that HAp/AA-NC had a stimulating effect on the cell viability of both, HaCaT and SKIN cells, relative to the irradiated control. Intracellular ROS significantly decreased in UV irradiated cells when treated with HAp/AA-NC. We conclude that the synthesized HAp/AA-NC have been validated in vitro as a skin protector against the harmful effect of UV-induced ROS.

Preparation and Characterization of Novel Polyaniline Nanosensor for Sensitive Detection of Formaldehyde.

Nanomaterials are promising in the field of optical sensors due to their unique properties. Emeraldine base of polyaniline (Nano EB-PANI) was prepared, characterized and applied as an optical formaldehyde sensor. FTIR data confirm the formation of the EB-PANI. TEM and SEM revealed the size and shape of the nanoscale EB-PANI. XRD showed that the obtained nano EB-PANI has a partial crystalline nature. The sensing mechanism is based on the reaction of formaldehyde with Nano EB-PANI- to form a complex as described by molecular modeling HF/3-21G** level of theory. Results showed that Nano EB-PANI- detect low concentrations of formaldehyde ranging from 0.0003 to 0.9 ppm in a dose-dependent manner. The molecular modeling theory analysis showed that formaldehyde could interact with the amine of EB-PANI in, ring 3 or 4 or both together. The binding energy and dipole moment of the interaction between formaldehyde and polyaniline nanosensor were calculated by HF/3-21g** level of theory. The interaction with ring 3-NH gives a less stable product with a high dipole moment 6.978 Debye comparing with 1.678 Debye for the product of formaldehyde interaction with the terminal ring 4-NH. The development of such novel EB-PANI nanosensor can be used as, reliable and sensitive formaldehyde sensor.

Fluorescent sensor for bacterial recognition.

Boronic acid-based fluorescent sensor is one of the non-enzymatic methods used for the recognition of saccharides. Since bacterial membrane has polysaccharides with diol groups, boronic acids probe could be applied for rapid bacterial recognition. Escherichia coli (XL-1 blue) were recognized by applying (3-(5-(dimethylamino) naphthalene-1-sulfonamide) phenyl) boronic acid (DNSBA) as a sensor and the fluorescence recorded by fluorometer micro-plate reader. Results showed that, fluorescence records of DNSBA increase in a dose dependent manner upon increasing the bacterial cell numbers. Moreover, the increase in the number of bacterial cells induces a shift in the spectra due to the formation of the anionic form of boronic acid complex. Therefore, DNSBA is an efficient sensor for monitoring bacterial cells.

Microplate assay for screening the antibacterial activity of Schiff bases derived from substituted benzopyran-4-one.

Schiff bases (SB(1)-SB(3)) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB(1)), p-phenylenediamine (SB(2)) and o-phenylenediamine (SB(3)), while Schiff bases (SB(4)-SB(6)) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB(4)), p-phenylenediamine (SB(5)) and o-phenylenediamine (SB(6)). Schiff bases were characterized using elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH(3) on position five have higher antibacterial activity than that containing hydroxy group on the same position.

Antibacterial effect of some benzopyrone derivatives.

The Schiff base derivatives of benzopyran-4-one are characterized by imine groups which have biological activities such as antimicrobial, antifungal and antitumoral. The aim of this study was therefore to evaluate the toxicity of Schiff bases towards bacterial cells. Escherichia coli as Gram-negative bacteria and Staphylococcus capitis as Gram-positive bacteria were exposed to different concentrations of Schiff bases. For assessment of toxicity a 96-well turbidimetric procedure, capable of testing the antimicrobial properties on a single microplate, was used. Analysis of the growth curves showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria was higher than that on Gram-positive. Furthermore the presence of hydroxylic groups is correlated with an increased antibacterial effect.

Rapid and sensitive microplate assay for screening the effect of silver and gold nanoparticles on bacteria.

BACKGROUND & AIM: Nanomaterials are the leading requirement of the rapidly developing field of nanomedicine and bionanotechnology, and in this respect, nanotoxicology research is gaining great importance. In the field of infections, nanoparticles are being utilized as therapeutic tools against microbes, thus understanding the properties of nanoparticles and their effect on microbes is essential prior to clinical application. The aim of this study was to evaluate a microplate-based assay for monitoring the toxicity of silver and gold nanoparticles on bacteria. METHOD: Escherichia coli, a Gram-negative bacteria, and Staphylococcus capitis, a Gram-positive bacteria, were exposed to different concentrations of gold and silver nanoparticles. RESULTS: Analysis of bacterial growth showed that the toxicity of silver nanospheres is higher than that of gold nanospheres. The toxicity of silver nanoparticles is dependent on their concentration, whereas in the case of gold nanoparticles, there is no significant toxic effect. Therefore, the described microplate assay could be used as a rapid and sensitive method for detection of bacterial growth inhibition.