Rehab M. Amin

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.

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.

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.

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.

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.

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.

Bioluminescence-Sensing Assay for Microbial Growth Recognition

The conventional methods for microbial viability quantification require cultivation and are laborious. There is consequently a widespread need for cultivation-free methods. The adenosine triphosphate (ATP) bioluminescence-sensing assay is considered an extremely effective biosensor; hence ATP is the energy currency of all living microbes and can be used as a rapid indicator of microbial viability. We developed an ATP bioluminescence-sensing assay to detect microbial viability. A bioluminescent recombinant E. coli strain was used with luciferase extracted from transformed bacteria. Results showed that there is a direct correlation between the bioluminescence intensity of the ATP bioluminescence-sensing assay and the microbial viability. Bacterial counts from food samples were detected using the developed sensing assay and validated by the traditional plate-counting method. Compared with the plate-counting method, ATP bioluminescence-sensing assay is a more rapid and efficient approach for detecting microbial viability.

Production of Well-Dispersed Aqueous Cross-Linked Chitosan-Based Nanomaterials as Alternative Antimicrobial Approach

In the current study, chitosan was extracted by deacetylation of chitin, which is extracted from shrimp shell. chitosan nanoparticles (CSNPs) were prepared by ionotropic gelation technique. chitosan/tripolyphosphate ratio (CS:TPP) was kept at 3:1 to prepare CSNPs. chitosan/silver nanocomposite (CS/AgNCs) were prepared by incorporating silver nanoparticles into CSNPs. The quality of the prepared nanocomposite was evaluated by infrared spectroscopy, UV–Vis spectroscopy, transmission electron microscopy, and antibacterial activity. Results showed that chitosan/silver nanocomposite in which, both chitosan and silver are in nanoscale was successfully prepared for the first time in a well-dispersed aqueous form. Whereas CSNPs act as a host material to form the nanocomposite unlike the previously prepared forms of chitosan–silver nanocomposites, that used chitosan bulk as host materials and the dispersion medium was slightly acidic. Moreover, results revealed that the antibacterial activity of CSNPs was significantly enhanced after incorporating trace amount of silver nanoparticles (0.535% w/w AgNPs/CSNPs).

Cytotoxicity of Magnetic Nanoparticles on Normal and Malignant Human Skin Cells

Magnetic nanoparticles have received considerable attention in nanomedicine due to their potential application as therapeutic or diagnostic tools based on their particular properties. However, prior to clinical application investigating the effect of these nanoparticles on cells is essential. The aim of the following study is therefore to evaluate the cytotoxicity of magnetic (Fe3O4) and gold-coated magnetic nanoparticles (Fe3O4@Au) on various cell lines in order to clarify the risk of these materials for human use. Toxicity of these nanoparticles on human dermal fibroblasts (SKIN), human squamous cell carcinoma cells (A431 cells) and human epidermal keratinocytes (HaCaT cells) were determined using the MTT assay. Results showed that, within the used concentration range, Fe3O4 nanoparticles had no significant effect on all investigated cell lines, while Fe3O4@Au nanoparticles seem to have a moderate toxicity on all cell lines with some selectivity for the malignant cells, although it is yet moderate. The ...