Anti-proliferative activity of silver nanoparticles

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Enhanced Genotoxicity of Silver Nanoparticles in DNA Repair Deficient Mammalian Cells

Silver nanoparticles (Ag-np) have been used in medicine and commercially due to their anti-microbial properties. Therapeutic potentials of these nanoparticles are being explored extensively despite the lack of information on their mechanism of action at molecular and cellular level. Here, we have investigated the DNA damage response and repair following Ag-np treatment in mammalian cells. Studies have shown that Ag-np exerts genotoxicity through double-strand breaks (DSBs). DNA-PKcs, the catalytic subunit of DNA dependent protein kinase, is an important caretaker of the genome which is known to be the main player mediating Non-homologous End-Joining (NHEJ) repair pathway. We hypothesize that DNA-PKcs is responsible for the repair of Ag-np induced DNA damage. In vitro studies have been carried out to investigate both cytotoxicity and genotoxicity induced by Ag-np in normal human cells, DNA-PKcs proficient, and deficient mammalian cells. Chemical inhibition of DNA-PKcs activity with NU7026, an ATP-competitive inhibitor of DNA-PKcs, has been performed to further validate the role of DNA-PKcs in this model. Our results suggest that Ag-np induced more prominent dose-dependent decrease in cell viability in DNA-PKcs deficient or inhibited cells. The deficiency or inhibition of DNA-PKcs renders the cells with higher susceptibility to DNA damage and genome instability which in turn contributed to greater cell cycle arrest/cell death. These findings support the fact that DNA-PKcs is involved in the repair of Ag-np induced genotoxicity and NHEJ repair pathway and DNA-PKcs particularly is activated to safeguard the genome upon Ag-np exposure

Predictive Genomics: A Post-genomic Integrated Approach to Analyse Biological Signatures of Radiation Exposure

The ultimate objective of radiation research is to link human diseases with the altered gene expression that underlie them and the exposure type and level that caused them. However, this has remained a daunting task for radiation biologists to indent genomic signatures of radiation exposures. Transcriptomic analysis of the cells can reveal the biochemical or biological mechanisms affected by radiation exposures. Predictive genomics has revolutionised how researchers can study the molecular basis of adverse effects of exposure to ionising radiation. It is expected that the new field will find efficient and high-throughput means to delineate mechanisms of action, risk assessment, identify and understand basic mechanisms that are critical to disease progression, and predict dose levels of radiation exposure. Previously, we have shown that cells responding to environmental toxicants through biological networks that are engaged in the regulation of molecular functions such as DNA repair and oxidative stress. To illustrate radiation genomics as an effective tool in biological dosimetry, an overview has been provided of some of the current radiation genomics landscapes as well as potential future systems to integrate the results of radiation response profiling across multiple biological levels in to a broad consensus picture. Predictive genomics represents a promising approach to high-throughput radiation biodosimetry.Defence Science Journal, 2011, 61(2), pp.133-137, DOI:http://dx.doi.org/10.14429/dsj.61.83

Convolutional neural network-based techniques and error level analysis for image tamper detection

Photographs are the foremost powerful and trustworthy media of expression. At present, digital pictures not only serve forged information but also disseminate deceptive information. Users and experts with various objectives edit digital photographs. Images are frequently used as proof of reality or fact, therefore fake news or any publication that makes use of photos that have been altered in any way has a larger chance of deceiving readers. There is a need for a high-resolution image analysis model that processes individual pixels in images and a substantial amount of diverse image data, to detect image falsification. Convolutional neural network (CNN) with error level analysis (ELA) adopted in this research is found to be an ideal deep learning concept for detecting image manipulation. The model exhibited a validation accuracy of 99.6%, 99.7%, and 99.4% for CASIA V1.0, CASIA V2.0 and MICC datasets respectively. The accuracy for handmade tampered images was found to be 99.2%

Low temperature tolerance of human embryonic stem cells

This study investigated the effects of exposing human embryonic stem cells (hESC) to 4(o)C and 25(o)C for extended durations of 24h and 48h respectively. Cell survivability after low temperature exposure was assessed through the MTT assay. The results showed that hESC survivability after exposure to 25(o)C and 4(o)C for 24h was 77.3 ± 4.8 % and 64.4 ± 4.4 % respectively (significantly different, P < 0.05). The corresponding survival rates after 48h exposure to 25(o)C and 4(o)C was 71.0 ± 0.5 % and 69.0 ± 2.3 % respectively (not significantly different, P > 0.05). Spontaneous differentiation of hESC after low temperature exposure was assessed by morphological observations under bright-field and phase-contrast microscopy, and by immunocytochemical staining for the pluripotency markers SSEA-3 and TRA-1-81. hESC colonies were assigned into 3 grades according to their degree of spontaneous differentiation: (1) Grade A which was completely or mostly undifferentiated, (2) Grade B which was partially differentiated, and (3) Grade C which was mostly differentiated. In all low temperature exposed groups, about 95% of colonies remain undifferentiated (Grade A), which was not significantly different (P > 0.05) from the unexposed control group maintained at 37(o)C. Additionally, normal karyotype was maintained in all low temperature-exposed groups, as assessed by fluorescence in situ hybridization (FISH) of metaphase spreads with telomere and centromere-specific PNA probes. Further analysis with m-FISH showed that chromosomal translocations were absent in all experimental groups. Hence, hESC possess relatively high-tolerance to extended durations of low temperature exposure, which could have useful implications for the salvage of hESC culture during infrequent occurrences of incubator break-down and power failure

Differential regulation of intracellular factors mediating cell cycle, DNA repair and inflammation following exposure to silver nanoparticles in human cells

10.1186/2041-9414-3-2Genome Integrity3

Inhibition of poly (ADP-Ribose) polymerase-1 in telomerase deficient mouse embryonic fibroblasts increases arsenite-induced genome instability

10.1186/2041-9414-1-5Genome Integrity1

Differential resistance of human embryonic stem cells and somatic cell types to hydrogen peroxide-induced genotoxicity may be dependent on innate basal intracellular ROS levels

Previously, we demonstrated that undifferentiated human embryonic stem cells (hESC) displayed higher resistance to oxidative and genotoxic stress compared to somatic cells, but did not further probe the underlying mechanisms. Using H2O2-induced genotoxicity as a model, this study investigated whether higher resistance of hESC to oxidative and genotoxic stress could be due to lower innate basal intracellular levels of reactive oxygen species (ROS), as compared to their differentiated fibroblastic progenies (H1F) and two other somatic cell types — human embryonic palatal mesenchymal (HEPM) cells and peripheral blood lymphocytes (PBL). Comet assay demonstrated that undifferentiated hESC consistently sustained lower levels of DNA damage upon acute exposure to H2O2 for 30 min, compared to somatic cells. DCFDA and HE staining with flow cytometry showed that undifferentiated hESC had lower innate basal intracellular levels of reactive oxygen species compared to somatic cells, which could lead to their higher resistance to genotoxic stress upon acute exposure to H2O2