Afzal Shah

Polymeric micelles as drug delivery vehicles

Though much progress has been made in drug delivery systems, the design of a suitable carrier for the delivery of hydrophobic drugs is still a major challenge for researchers. The use of micellar solutions of low molecular weight surfactants has been one of the popular methods for the solubilization of hydrophobic drugs; however, such surfactants suffer from high critical micelle concentration and concomitant low stabilities. In contrast to surfactants of low molecular masses, polymeric micelles are associated with general advantages like higher stability, tailorability, greater cargo capacity, non-toxicity and controlled drug release. Therefore, the current review article is focused on the engineering of the core of polymeric micelles for maximum therapeutic effect. For enhanced drug encapsulation capacity and getting useful insights into the controlled release mechanism we have reviewed the effects of temperature and pH on responsive polymeric micelles. The article also presents important research outcomes about mixed polymeric micelles as better drug carriers in comparison to single polymeric micelles.

Voltammetric and spectroscopic investigations of 4-nitrophenylferrocene interacting with DNA.

Cyclic voltammetry (CV) coupled with UV-vis and fluorescence spectroscopy were used to probe the interaction of potential anticancer drug, 4-nitrophenylferrocene (NFC) with DNA. The electrostatic interaction of the positively charged NFC with the anionic phosphate of DNA was evidenced by the findings like negative formal potential shift in CV, ionic strength effect, smaller bathochromic shift in UV-vis spectroscopy, incomplete quenching in the emission spectra and decrease in viscosity. The diffusion coefficients of the free and DNA bound forms of the drug were evaluated from Randles-Sevcik equation. The binding parameters like binding constant, ratio of binding constants (K(red)/K(ox)), binding site size and binding free energy were determined from voltammetric data. The binding constant was also determined from UV-vis and fluorescence spectroscopy with a value quite close to that obtained from CV.

Redox Behavior of Anticancer Chalcone on a Glassy Carbon Electrode and Evaluation of its Interaction Parameters with DNA

The interaction of anticancer chalcone [AMC, 1-(4′-aminophenyl)-3-(4-N,N-dimethylphenyl)-2-propen-1-one] with DNA has been explored using electrochemical, spectroscopic and viscometric techniques. A shift in peak potential and decrease in peak current were observed in cyclic voltammetry and hypochromism accompanied with bathochromic shift were noticed in UV-Vis absorption spectroscopy. These findings were taken as evidence for AMC –DNA intercalation. A binding constant (K) with a value of 6.15 × 105 M−1 was obtained from CV data, which was also confirmed by UV-Vis absorption titration. Moreover, the diffusion coefficient of the drug with and without DNA (Db and Du), heterogeneous electron transfer rate constant (ko) and electron affinity (A) were also calculated from electrochemical data.

Synthesis, spectroscopic characterization, X-ray structure and evaluation of binding parameters of new triorganotin(IV) dithiocarboxylates with DNA

Three new triorganotin(IV) dithiocarboxylates (1-3) with general formula R(3)SnL, where R=C(4)H(9) (1), C(6)H(11) (2), C(6)H(5) (3) and L=4-(4-nitrophenyl)piperazine-1-carbodithioate, have been synthesized and characterized by elemental analysis, Raman, FT-IR, multinuclear NMR ((1)H, (13)C and (119)Sn) and mass spectrometry. The crystal structure of complex 3 confirmed distorted trigonal-bipyramidal geometry around Sn atom. The interaction of compounds 1-3 with DNA was investigated by cyclic voltammetry (CV) and UV-vis spectroscopy. The positive peak potential shift in CV and hypochromic effect in spectroscopy evidenced intercalative mode of interaction. The results indicate that the binding affinity varies in this sequence: 1>3>2.

Chemistry of DNA minor groove binding agents

Most of the clinically used anticancer drugs exert their antitumor effect by damaging the replication machinery of DNA either by covalent or non-covalent binding. Intercalation and groove fitting are the major modes of non-covalent interaction. Small crescent shaped molecules have been claimed to bind with DNA via minor grooves. A plethora of hybrid molecules based on distamycin or netropsin have been synthesised with the objectives of improved selectivity and specificity with no/reduced unwanted side effects. This review critically and objectively describes the previously known hybrid DNA minor groove binding agents based on five membered, distamycin or netropsin. Moreover, the future use of six-membered benzamides has also been highlighted. Special emphasis has been put on developing structure-activity relationships of DNA minor groove binding agents.

Micelles as Soil and Water Decontamination Agents

Contaminated soil and water pose a serious threat to human health and ecosystem. For the treatment of industrial effluents or minimizing their detrimental effects, preventive and remedial approaches must be adopted prior to the occurrence of any severe environmental, health, or safety hazard. Conventional treatment methods of wastewater are insufficient, complicated, and expensive. Therefore, a method that could use environmentally friendly surfactants for the simultaneous removal of both organic and inorganic contaminants from wastewater is deemed a smart approach. Surfactants containing potential donor ligands can coordinate with metal ions, and thus such compounds can be used for the removal of toxic metals and organometallic compounds from aqueous systems. Surfactants form host-guest complexes with the hydrophobic contaminants of water and soil by a mechanism involving the encapsulation of hydrophobes into the self-assembled aggregates (micelles) of surfactants. However, because undefined amounts of surfactants may be released into the aqueous systems, attention must be paid to their own environmental risks as well. Moreover, surfactant remediation methods must be carefully analyzed in the laboratory before field implementation. The use of biosurfactants is the best choice for the removal of water toxins as such surfactants are associated with the characteristics of biodegradability, versatility, recovery, and reuse. This Review is focused on the currently employed surfactant-based soil and wastewater treatment technologies owing to their critical role in the implementation of certain solutions for controlling pollution level, which is necessary to protect human health and ensure the quality standard of the aquatic environment.

Self-assembly of guanosine and deoxy-guanosine into hydrogels: monovalent cation guided modulation of gelation, morphology and self-healing properties

In this study, we report the effect of monovalent cations including Na+, K+, Rb+, Ag+, Au+, Tl+, Hg+ and NH4 + on the stimulation of purine nucleosides guanosine (G) and deoxy-guanosine (dG) to self-assemble into hydrogels. The gelation properties in terms of gel crystallization, lifetime stability, thermo-reversibility, minimum gelation concentration, gel melting temperature, thixotropic property and others were thoroughly investigated and compared not only between two nucleosides but also among different metal ions. A few metal ions were found to induce G/dG to form gels with much improved lifetime stability. The results revealed that dG is a much better gelator than G for introduction of a thixotropic property. Interestingly, morphological, fluorescence and rheological (thixotropic) properties of the gels were found to modulate significantly by changing the metal ions. In the presence of K+ ions, G produces a self supporting tight gel but it has poor lifetime stability. In contrast, the presence of K+ ions stimulates dG to form a very loose gel but with excellent lifetime stability and thixotropic property. In this context, we have successfully engineered a self-supporting stable co-gel using a simple co-gelation method by mixing an equimolar amount of K+ induced G and dG gels and this co-gel shows long lifetime stability, self-healing and injectable properties which may allow for a broad range of biological applications. Furthermore, an Ag+ induced G gel was exploited for the light triggered in situ fabrication of uniform AgNPs within a gel to make a nano-bio hybrid material.

Separation and recycling of nanoparticles using cloud point extraction with non-ionic surfactant mixtures

A viable cost-effective approach employing mixtures of non-ionic surfactants Triton X-114/Triton X-100 (TX-114/TX-100), and subsequent cloud point extraction (CPE), has been utilized to concentrate and recycle inorganic nanoparticles (NPs) in aqueous media. Gold Au- and palladium Pd-NPs have been pre-synthesized in aqueous phases and stabilized by sodium 2-mercaptoethanesulfonate (MES) ligands, then dispersed in aqueous non-ionic surfactant mixtures. Heating the NP-micellar systems induced cloud point phase separations, resulting in concentration of the NPs in lower phases after the transition. For the Au-NPs UV/vis absorption has been used to quantify the recovery and recycle efficiency after five repeated CPE cycles. Transmission electron microscopy (TEM) was used to investigate NP size, shape, and stability. The results showed that NPs are preserved after the recovery processes, but highlight a potential limitation, in that further particle growth can occur in the condensed phases.

New supramolecular ferrocenyl amides: synthesis, characterization, and preliminary DNA-binding studies

Three ferrocenyl amides have been synthesized and characterized by analytical techniques. Based on single-crystal X-ray analysis, a supramolecular structure was attributed to 1 owing to the presence of intermolecular non-covalent interactions. UV-Visible spectroscopy, viscometry, and dynamic laser light scattering was used to assess the mode of interaction and binding of these complexes with DNA, which varied in the sequence 1 > 2 > 3. The binding is presumably due to the ability of these complexes to form secondary non-covalent interactions with DNA bases. Complex-DNA adduct formation depends on the nature of R of the amide.

Characterization and DNA binding studies of unexplored imidazolidines by electronic absorption spectroscopy and cyclic voltammetry

UV-Vis spectroscopic behavior of four imidazolidine derivatives i.e., [5-benzylideneimidazolidine-2,4-dione (NBI), 5-(2-hydroxybenzylidene)imidazolidine-2,4-dione (HBI), 5-(4-methoxybenzylidene)imidazolidine-2,4-dione (MBI) and 5-(3,4-di-methoxybenzylidene)imidazolidine-2,4-dione (DBI)] was studied in a wide pH range. Spectroscopic response of the studied compounds was found sensitive to pH and the attached substituents. Incited by anti-tumor activity, structural miscellany and biological applications of imidazolidines, the DNA binding affinity of some novel derivatives of this class of compounds was examined by cyclic voltammetry (CV) and UV-Vis spectroscopy at pH values of blood (7.4) and lysosomes (4.5). The CV results showed the following order of binding strength: KNBI (6.40×10(6)M(-1))>KHBI (1.77×10(5)M(-1))>KMBI (2.06×10(4)M(-1))>KDBI (1.01×10(4)M(-1)) at pH 7.4. The same order was also obtained from UV-Vis spectroscopy. The greater affinity of NBI justified its preferred candidature as an effective anti-cancer drug. The DNA binding propensity of these compounds was found comparable or greater than most of the clinically used anticancer drugs.