Debalina Bhattacharya

A novel study of antibacterial activity of copper iodide nanoparticle mediated by DNA and membrane damage.

In this article potential activity of nanoparticles (NPs) of copper iodide (CuI) as an antibacterial agent has been presented. The nano particles are synthesized by co-precipitation method with an average size of 8 nm as determined by Transmission Electron Microscope (TEM). The average charge of the NPs is -21.5 mV at pH 7 as obtained by zeta potential measurement and purity is determined by XRD. These NPs are able to kill both gram positive and gram negative bacteria. Among the bacteria tested, DH5α is more sensitive but Bacillus subtilis is more resistant to NPs of CuI. Consequently, the MIC and MBC values of DH5α is least (0.066 mg/ml and 0.083 mg/ml respectively) and B. subtilis is highest (0.15 mg/ml and 0.18 mg/ml respectively) among the tested bacterial strains. From our studies it is inferred that CuI NPs produce reactive oxygen species (ROS) in both gram negative and gram positive bacteria and it also causes ROS mediated DNA damage for the suppression of transcription as revealed by reporter gene assay. Probably ROS is formed on the surface of NPs of CuI in presence of amine functional groups of various biological molecules. Furthermore they induce membrane damage as determined by atomic force microscopy (AFM). Thus production of ROS and membrane damage are major mechanisms of the bactericidal activity of these NPs of CuI.

Morphology-Directing Synthesis of Rhodamine-Based Fluorophore Microstructures and Application toward Extra- and Intracellular Detection of Hg2+

A new, easily synthesizable rhodamine-based chemosensor with potential N2O2 donor atoms, L(3), has been characterized by single-crystal X-ray diffraction together with (1)H NMR and high-resolution mass spectrometry (HRMS) studies. L(3) was found to bind selectively and reversibly to the highly toxic Hg(2+) ion. The binding stoichiometry and formation constant of the sensor toward Hg(2+) were determined by various techniques, including UV-vis, fluorescence, and Jobs studies, and substantiated by HRMS methods. None of the biologically relevant and toxic heavy metal ions interfered with the detection of Hg(2+) ion. The limit of detection of Hg(2+)calculated by the 3σ method was 1.62 nM. The biocompatibility of L(3) with respect to its good solubility in mixed organic/aqueous media (MeCN/H2O) and cell permeability with no or negligible cytotoxicity provides good opportunities for in vitro/in vivo cell imaging studies. As the probe is poorly soluble in pure water, an attempt was made to frame nano/microstructures in the absence and in the presence of sodium dodecyl sulfate (SDS) as a soft template, which was found to be very useful in synthesizing morphologically interesting L(3) microcrystals. In pure water, micro-organization of L(3) indeed occurred with block-shaped morphology very similar to that in the presence of SDS as a template. However, when we added Hg(2+) to the solution of L(3) under the above two conditions, the morphologies of the microstructures were slightly different; in the first case, a flowerlike structure was observed, and in second case, a simple well-defined spherical microstructure was obtained. Optical microscopy revealed a dotlike microstructure for L(3)-SDS assemblies, which changed to a panicle microstructure in the presence of Hg(2+). UV-vis absorption and steady-state and time-resolved fluorescence studies were also carried out in the absence and presence of Hg(2+), and also the SDS concentration was varied at fixed concentrations of the receptor and guest. The results revealed that the fluorescence intensity increased steadily with [SDS] until it became saturated at ∼7 mM SDS, indicating that the extent of perturbation to the emissive species increases with the increase in [SDS] until it becomes thermodynamically stable. There was also an increase in anisotropy with increasing SDS concentration, which clearly manifests the restriction of movement of the probe in the presence of SDS.

Evaluation of copper iodide and copper phosphate nanoparticles for their potential cytotoxic effect

To explore the potential biological activities of transition metal-based nanoparticles (NPs), we synthesized two copper-based NPs, CuI and Cu3(PO4)2. The structural features of these NPs were determined by the X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). The size of CuI and Cu3(PO4)2 NPs were 35 ± 4.2 nm and 67 ± 6.3 nm respectively as determined by TEM. Cell viability, generation of reactive oxygen species (ROS), cell cycle and induction of apoptosis were assessed on human breast cancer cell line MCF7 after the treatment of these NPs. Exposure of CuI and Cu3(PO4)2 NPs decreased cell viability in a dose-dependent manner. Also, CuI NPs produced more ROS compared to Cu3(PO4)2 and presence of N-acetyl cysteine (NAC) along with NPs increased the cell survival. Cell cycle analysis indicated that after exposure of these NPs at their respective LD50 doses increased Sub G1 and G2/M peak after 8 h and 24 h of treatment respectively. Apoptosis study by AnnexinV-FITC staining showed slight increased in the early and late apoptosis after 8 h of treatment and most of the cells were dead after 24 h of treatment. Thus our observations suggest that the exposure of these two NPs induced dose-dependent cytotoxicity on MCF7 cell that is associated with ROS-mediated apoptosis.

Influence of ionic strength on the interaction of THA and its Cu(II) complex with DNA helps to explain studies on various breast cancer cells

THA, a structural analogue of the family of anthracycline anticancer drugs, was used to understand how environmental changes affect its biophysical interactions with DNA. A variation of the ionic strength of the medium was attempted at a constant pH. Under such varying conditions, the binding constant and the site size of interaction were evaluated. Owing to the close structural similarity with anthracyclines and the fact that the quinone moiety in these drugs control the chemical reactions, the effect of the ionic strength on the physicochemical and biophysical attributes of hydroxy-9,10-anthraquinones is important. With an increase in ionic strength, the dissociation of the first proton of THA is affected to a greater extent compared to the second proton. Since the pKa1 is connected to the generation of the mono-anion of THA, an increase in its value implies that there would be less anion in the medium leading to improved DNA binding. Increased NaCl concentration neutralizes the negative charges on the DNA backbone manifesting in an overall increase in the binding constant for THA. This fact might be exploited for the use of such molecules in cancer patients. However, in the case of a CuII complex of THA and the formation of anions being almost negligible, there is a marked improvement in DNA binding. The cytotoxic action of THA (LH3) and its CuII complex [CuII(LH2)2] was also studied on three breast carcinoma cell lines and a primary human dermal fibroblast cell line. The complex was seen to perform better than THA. The results could be explained with the help of the comet assay, the γH2AX foci assay, and DAPI staining followed by western blotting with an apoptotic protein marker. The findings of THA and its CuII complex were compared to anthracycline doxorubicin.

A novel Cu(II)–mal–picoline complex induces mitotic catastrophe mediated by deacetylation of histones and α-tubulin leading to apoptosis in human cell lines

In this study, we investigated mitotic catastrophe followed by apoptosis induced in human cell lines [HeLa, HepG2 and THP1] by a novel Cu(II) complex having malonate as the primary ligand and protonated 2-amino-4-picoline as the counter ion; whose in vitro DNA binding ability was demonstrated previously (B. Saha et al., J. Phys. Chem. B, 2010, 114(17), 5851–5861). Using the auto-fluorescence property of the complex, it was observed that the complex entered into the cells within 15 min after the exposure and was able to kill cells as determined by clonogenic survivability and MTT assay in a dose and time dependent manner. While dissecting the cell killing mechanisms, it was found that initially the complex induced multinucleated cells by inhibiting acetylation of a histone acetyl transferase (HAT) domain of CBP/p300, although histone deacetylase 6 (HDAC6) expression did not change much. As a result, histone proteins, H3 and H2AX, along with a non-histone protein, α-tubulin, were mostly deacetylated after 48 h of the treatment. This eventually led to mitotic catastrophe (MC), as histone acetylation–deacetylation dynamics is essential for the successful mitosis. DNA damage-induced γH2AX and 53BP1 foci in the treated cells were also observed after 72 h of treatment, as abnormal mitosis with decondensed chromosomes are prone to nucleolytic attack. These molecular phenomena ultimately rendered apoptosis. Taken together, our results provided evidence that the said complex perturbed the signaling events associated with mitosis and consequently induced cell death.

γ radiation-induced damage of nucleic acid bases, calf thymus DNA and DNA within MCF-7 breast cancer cells by [Cu2(OAc)4(tnz)2]: a potential radiosensitizer

A dimeric complex of Cu(II) with tinidazole characterized earlier was used to study radiosensitizing attributes. Studies reveal that the complex is better than tinidazole in sensitizing radiation-induced damage of nucleic acid bases uracil and thymine, radiation-induced double strand modification of calf thymus DNA and modification of DNA within MCF-7 breast cancer cells. The unique aspect of this study is that in spite of a substantial decrease in the generation of the nitro-radical anion (NO2˙−) following complex formation of tinidazole with Cu(II), no decrease was observed in the radiosensitizing attribute of nitroimidazoles. Rather the complex was clearly ahead of tinidazole with regard to radiosensitization. Hence, complex formation of important drug molecules are an advantage since it helps to target DNA better. This study serves as a good example where a common intermediate (NO2˙−) responsible for efficacy as well as toxic side effects can be suitably tuned in its generation using a modified form of 5-nitroimidazole (here tinidazole) to be able to strike the correct balance between efficacy and toxic side effects.

Load Handling and Repetitive Movements Are Associated with Chronic Low Back Pain among Jute Mill Workers in India

Introduction. WHO recognizes low back pain as one of the most important ergonomic stressors. Therefore, the present study was designed to find out the magnitude of the problem among jute mill workers in India and identify possible associations. Methodology. This cross-sectional workplace based study was conducted among eight (8) selected jute mills of India. Subjects with self-reported back pain for at least last 12 weeks were included and n = 717 male jute mill workers actively engaged in work entered the study and completed all assessments. Results. Among all participants 55% (n = 392) had current chronic low back pain. Age was an important association with subjects in the age group of 40–59 years more likely to have pain (p = 0.02, OR 1.44). Regarding ergonomic risk factors lifting of load of more than 20 kg (p = 0.04, OR 1.42) and repetitive movements of limbs (p = 0.03, OR 0.67) were significant associations of chronic low back pain. Conclusion. This study identified a significant prevalence of current chronic low back pain among jute mill workers. Regarding ergonomic risk factors the present study has identified two significant associations: lifting of load above 20 kg and repetitive movements of limbs. Therefore, this study has identified need for workplace interventions in this occupational group employing approximately 3,50,000 workers in India.