Ayaz Mahmood Dar

Physicochemical Properties of Nanomaterials: Implication in Associated Toxic Manifestations

Nanotechnology has emerged as one of the leading fields of the science having tremendous application in diverse disciplines. As nanomaterials are increasingly becoming part of everyday consumer products, it is imperative to assess their impact on living organisms and on the environment. Physicochemical characteristics of nanoparticles and engineered nanomaterials including size, shape, chemical composition, physiochemical stability, crystal structure, surface area, surface energy, and surface roughness generally influence the toxic manifestations of these nanomaterials. This compels the research fraternity to evaluate the role of these properties in determining associated toxicity issues. Reckoning with this fact, in this paper, issues pertaining to the physicochemical properties of nanomaterials as it relates to the toxicity of the nanomaterials are discussed.

In vitro cytotoxcity and interaction of new steroidal oxadiazinanones with calf thymus DNA using molecular docking, gel electrophoresis and spectroscopic techniques

Herein we report synthesis of new steroidal oxadiazinanones from steroidal ketones. After characterization by spectral and analytical data, the interaction studies of compounds (4-6) with DNA were carried out by UV-vis, fluorescence spectroscopy and gel electrophoresis. The compounds bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb; 1.8×10(4) M(-1), 2.2×10(4) M(-1) and 2.6×10(4) M(-1), respectively, indicating the higher binding affinity of compound 6 towards DNA. Gel electrophoresis showed the concentration dependent cleavage activity of compound 6 alone or in presence of Cu (II) causes the nicking of supercoiled pBR322 and it seems to follow the mechanistic pathway involving generation of hydroxyl radicals that are responsible for initiating DNA strand scission. Molecular simulations suggest that compounds binds through minor groove of DNA. MTT assay depicted promising anticancer activity of compound 5 and 6 particularly against HL-60 and MCF-7. The apoptotic degradation of DNA was analyzed by agarose gel electrophoresis and visualized by ethidium bromide staining (comet assay). The results revealed that compound 6 has better prospectus to act as cancer chemotherapeutic candidate which warrants further in vivo anticancer investigations.

Molecular Docking: Approaches, Types, Applications and Basic Challenges

Abstract Molecular docking is a kind of bioinformatic modelling which involves the interaction of two or more molecules to give the stable adduct. Depending upon binding properties of ligand and target, it predicts the three-dimensional structure of any complex. Molecular docking generates different possible adduct structures that are ranked and grouped together using scoring function in the software. Docking simulations predict optimized docked conformer based upon total energy of the system. In spite of all potential approaches, ligand chemistry (tautomerism and ionization), receptor flexibility (single conformation of rigid receptor) and scoring function (differentiate true binding mode) still remained the challenge. Many important aspects of molecular docking in terms of its approaches, types, applications and challenges are briefly discussed in this article.

Photoinactivation of multidrug resistant bacteria by monomeric methylene blue conjugated gold nanoparticles

Multidrug resistant (MDR) bacterial infections have become a severe threat to the community health due to a progressive rise in antibiotic resistance. Nanoparticle-based photodynamic therapy (PDT) is increasingly been adopted as a potential antimicrobial option, yet the cytotoxicity associated with PDT is quite unspecific. Herein, we show Concanavalin-A (ConA) directed dextran capped gold nanoparticles (GNPDEX-ConA) enhanced the efficacy and selectivity of methylene blue (MB) induced killing of multidrug resistant clinical isolates. Here, we show that our complex MB@GNPDEX-ConA is effective against range of MDR clinical isolates, including Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae. In our treatment modality negligible dark toxicity suggests photochemically driven process with 97% killing of MDR bacteria. GNPDEX-ConA with monomeric form of MB departs maximum fluorescence decay time (τf: 1.7ns in HSA) and singlet oxygen (ΔΦ; 0.84) for improved activity in albumin rich infection sites. Further, the complex show least toxicity when tested against HEK293 mammalian cells. The principle component analysis (PCA) and confocal microscopy illustrates cytosolic 1O2 mediated type-II PDT as mechanism of action. Hence, MB@GNPDEX-ConA mediated PDT is potential therapeutic approach against MDR infections and can be tailored to fight other infectious diseases.

Strategies for the Synthesis of Thiazolidinone Heterocycles

Thiazolidinones is the special class of heterocyclic compounds with a broad spectrum of biological activities such as anti-inflammatory, antiproliferative, antihistaminic, anti-HIV, hypnotic, anaesthetic, antifungal, anthelmintic and antiviral agents as well as CNS stimulants. Therefore researchers have synthesized these condensed heterocycles through different complex pathways as target structures for biological studies. This review focuses on the various strategies followed for the convenient synthesis of thiazolidinone based heterocyclic derivatives. The steps included condensation followed by cyclization of Schiff’s bases, either in a step-wise manner or in one pot under different conditions. Mercaptoacetic acid, thiolactic acid, chloroacetyl chloride, potassium thiocyanate, ethylchloro acetate and ammonium thiocyanate are the most common reagents used for the synthesis thiazolidinone appended on different heterocyclic skeletons.

DNA Binding, Cleavage Activity, Molecular Docking, Cytotoxicityand Genotoxicity Studies of Newly Synthesized Copper Based MetalComplexes

The design and synthesis of medicinal chemotherapeutic agents of copper with 2-(benzothiazol-2-yl iminomethyl)-phenol, 2-(benzothiazol-2-yliminomethyl)-valine, cyanoaceto (2-mer- captobenzylidene)-hydrazide, 2-(phenacyl bromide)-aminothiophenol, (2-mercaptobenzaldehyde) thio- semicarbazone, N-(phenacyl bromide)-2- yliminobenzothiazole, 2-aminobenzothiazole, benzothiazol-2-yliminomethyl)-phenol and 2-[(2E¹-aminobenzylidene)- amino]-benzenethiol were synthesized. The characterization was done by FTIR, 1H and 13C NMR, MS, TGA and elemental analysis. Interaction of complexes 8 and 9 with CT DNA was done by using UV-vis and fluorescence spectroscopy depicting the hyperchromic behaviour of complexes. The intrinsic binding constants (Kb) for complex 8 and 9 were 2.35 × 103 M-1 and 2.12 × 103 M-1. The cleavage studies of complex 8 and 9 were done with pBR322 plasmid showing the potential cleaving ability of the complexes at very low concentration. The gel electrophoresis pattern also demonstrated that the complex 8 alone or in presence of Cu (II) causes the nicking of supercoiled pBR322 and it seems to follow the mechanistic pathway involving generation of hydroxyl radicals that are responsible for initiating DNA strand scission. The molecular docking studies showed the minor groove binding behaviour of the complexes 8 and 9 with DNA. During the MTT assay against different cancer cell lines like SW480, HepG2, HT29 and HL60, all the complexes showed potential cytotoxic behaviour by giving effective IC50 close to Cisplatin. The bioactivity score and PASS analysis also depicted the drug like nature of the complexes. During the comet assay, apoptotic degradation of DNA in the presence of complex 8 and 9 was analysed by agarose gel electrophoresis and visualized by ethidium bromide staining.

Synthesis, molecular docking and biological evaluation of new steroidal 4H-pyrans.

A series of new steroidal 4H-pyrans (4-6) have been synthesized from steroidal α, β-unsaturated ketones (1-3). The products (4-6) were characterized by IR, (1)H NMR, (13)C NMR, MS and analytical data. The interaction studies of compounds (4-6) with DNA were carried out by employing gel electrophoresis, UV-vis and fluorescence spectroscopy. The gel electrophoresis pattern revealed that compounds (4-6) bind to DNA and also demonstrated that the compound 6 alone or in presence of Cu (II) causes the nicking of supercoiled pBR322. The compounds 4 and 5 bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb values found to be 5.3×10(3) and 3.7×10(3) M(-1), respectively, indicating the higher binding affinity of compound 4 towards DNA. The docking study suggested the intercalation of compounds in between the nucleotide base pairs. The cytotoxicity and genotoxicity of the newly synthesized compounds were checked by MTT and comet assay, respectively during which compound 6 showed potential behaviour.

DNA binding, artificial nuclease activity and cytotoxic studies of newly synthesized steroidal pyrimidines

The new steroidal pyrimidine derivatives (4-6) were synthesized by the reaction of steroidal thiosemicarbazones with (2-methyl) diethyl malonate in absolute ethanol. After characterization by spectral and analytical data, the DNA interaction studies of compounds (4-6) were carried out by UV-vis, fluorescence spectroscopy, hydrodynamic measurements, molecular docking and gel electrophoresis. The compounds bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb; 2.31×103M-1, 1.93×103M-1 and 2.05×103M-1, respectively indicating the higher binding affinity of compound 4 towards DNA. Gel electrophoresis demonstrated that compound 4 showed a strong interaction during the concentration dependent cleavage activity with pBR322 DNA. The molecular docking study suggested the intercalation of steroidal pyrimidine moiety in the minor groove of DNA. During in vitro cytotoxicity, compounds (4-6) revealed potential toxicity against the different human cancer cells (MTT assay). During DAPI staining, the nuclear fragmentations on cells occurred after treatment with compounds 4 and 5. Western blotting analysis clearly indicates that compound 4 causes apoptosis in MCF-7 cancer cells. The results revealed that compound 4 has better prospectus to act as a cancer chemotherapeutic candidate, which warrants further in vivo anticancer investigations.

Steroidal imidazoles: Synthesis, characterization, molecular docking studies with DNA and in vitro cytotoxicity

Bio-active steroidal imidazoles 7–9 were synthesised by reacting steroidal thiosemicarbazones 4–6 with phenacyl bromide. After characterisation by spectral and analytical data, the interaction of compounds 7–9 with DNA were carried out by UV-vis, luminescence spectroscopy and gel electrophoresis. The compounds bind with DNA preferentially through electrostatic and hydrophobic interactions with Kb; 3.14 × 104, 6.27 × 104 and 5.17 × 104 M−1, respectively indicating higher binding affinity of compound 8 towards DNA. Gel electrophoresis depicted the concentration dependent cleavage activity of compound 8 with supercoiled pBR322. The docking study revealed the minor groove binding of compounds with DNA and intercalation between the nucleotide base pairs is due to imidazole moiety. In Dimethyl thiazolyl diphenyl tetrazolium bromide assay, compounds 7 and 8 showed promising activity against different human cancer cells especially against A545, HepG2 and MCF7 cells. The uptake of compounds by HepG2, MCF7 and A549 cells was studied by confocal microscopy. The Genotoxic nature of compounds 7 and 8 was studied by the comet assay while as the relative expressions of apoptotic markers of A545 cells after interacting with steroidal imidazoles was studied by western blotting analysis.

A Concise Review on the Synthesis of Pyrazole Heterocycles

Study background: Pyrazole moiety, being called as pharmacophore, plays an important role in many biologically active compounds and therefore represents an interesting template for combinatorial as well as medicinal chemistry. In addition pyrazoles are also used extensively as useful synthons in organic synthesis. These derivatives have wide spread biological activities such as anticancer, analgesic, anti-inflammatory, antimicrobial, antiviral, anticonvulsant, antihistaminic and anti-HIV. The recent success of pyrazole COX-2 inhibitor has further highlighted the importance of these heterocycles in medicinal chemistry. Methodology: The steps included condensation followed by cyclization or MCR, either in a step-wise manner or in one pot has been achieved successfully to obtain this class of heterocycles under different conditions. Phosphorus oxychloride (POCl3 ), dimethyl formamide, acetamide and hydrazine are the most common reagents used for the synthesis of pyrazole appended heterocyclic skeletons. Results: The reaction schemes resulted in the synthesis of heterocyclic appended pyrazoles in potential yields under either simple reaction conditions or microwave irradiation. Conclusion: These protocols provide convenient strategies to annelate different heterocyclic nuclei with widespread bioactive pyrazoles thereby extending the categories of heterocyclic systems. These strategies also provide valuable information for the further design of more active biological agents through various modifications and derivatizations.