Pramod Kumar

Ormosil nanoparticles as a sustained-release drug delivery vehicle

Silica-based nanoparticles are well known for their ease of synthesis, structural robustness, resistance to biofouling, enhanced storage stability, and multimodality. Organically modified silica (ormosil) nanoparticles are a special type of hybrid nanoparticle known for encapsulating/conjugating active agents for applications such as in photodynamic therapy (PDT), gene therapy and diagnostic imaging. Herein, we report the use of ormosil nanoparticles as a sustained release drug delivery vehicle, using the well-known anticancer and fluorescent drug doxorubicin (Dox). These drug/dye loaded nanoparticles have been synthesized within an oil-in-water microemulsion medium, and characterized for their size, shape, porosity, and optical properties. Nanoencapsulation significantly enhanced the optical stability of a dye against chemical quenching. Particle-size variation could be achieved by changing the amount of co-surfactant. However, size variation did not affect their pore size. The release pattern of encapsulated drug was found to depend on the size of the nanoparticles, with optimal drug release observed for the 50 nm particles at about 70% in a sustained manner over two weeks. Confocal bioimaging was used to demonstrate the differential pattern of cellular uptake of the free and nanoencapsulated drugs, as the sub-cellular distribution of nanoencapsulated Dox is guided by the nanoparticles distributing throughout the cytosol. Cell viability (MTS) and soft-agar colony formation assays in vitro have confirmed the cytotoxic effects of the drug loaded nanoparticles, but not of the blank nanoparticles. The results indicate that ormosil nanoparticles can act as a sustained release vehicle of potent lipophilic anticancer drugs.

Arene-based fluorescent probes for the selective detection of iron

Pyridine-2,6-dicarboxamide based probes containing phenyl (L1), naphthyl (L2) and anthracenyl (L3) groups have been synthesized and screened towards Na+, Mg2+, Ca2+, Cr3+, Mn2+, Mn3+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, Cd2+ and Pb2+ ions. Probes L2 and L3 exhibited remarkable sensing for Fe2+ and Fe3+ ions with L3 being particularly selective. Collective studies comprising of Jobs plot, Benesi–Hildebrand fitting, Stern–Volmer plot and detection limit display notable sensing ability of probe L3 for Fe3+ as compared to Fe2+ ion. Competitive binding studies in presence of other metal ions further illustrated the high efficiency of L3. The probe L3 binds to Fe3+ ion by forming a 1u2006:u20061 complex with the apparent association constant (Ka) of 3.31 × 103 M−1. L3–Fe3+ system is shown to have potential applications in logic gate and cell imaging.

The wonderful world of pyridine-2,6-dicarboxamide based scaffolds

The present perspective focusses on a variety of scaffolds based on a pyridine-2,6-dicarboxamide fragment and their noteworthy roles in coordination chemistry, stabilization of reactive species, synthetic modelling of some metalloenzyme active sites, catalytic organic transformations, and sensing as well as recognition applications. These examples illustrate the significance of synthetic scaffolds based on the pyridine-2,6-dicarboxamide fragment in synthetic chemistry in general and coordination chemistry in particular.

Formulation of size reduction technique in microstrip circuits by using DGS and DMS

In this work a simplified and accurate mathematical formula is derived to predict the reduced dimension of the microstrip circuit by using applicable etching geometry on plane of microstrip circuit such as DGS/DMS that will affect the resonance frequency of microstrip circuit in desired direction due to increment of slow wave effect. Here we developed proportional formula of defect which is verified successfully by applying to network implemented with an open circuit and for microstrip patch antennas, phase shifter.

Selective fluorescent turn-off sensing of Pd2+ ion: applications as paper strips, polystyrene films, and in cell imaging

Pyridine-2,6-dicarboxamide based scaffolds with appended naphthyl groups act as fluorescent probes for the selective detection of Pd2+ ions in aqueous medium. Collective studies comprising Jobs plots, Benesi–Hildebrand fittings, Stern–Volmer plots and detection limits illustrate the notable sensing abilities of such probes for the Pd2+ ion. These probes further demonstrate potential applications as paper-strip sensors, as polystyrene film-based sensors, and in cell imaging.

Synthesis of Dox Drug Conjugation and Citric Acid Stabilized Superparamagnetic Iron-Oxide Nanoparticles for Drug Delivery

In this manuscript, we report a novel, low cost and easy synthesis, iron-oxide nanoparticles were synthesized via room-temperature reduction of a mixture of ferric and ferrous salts, containing citric acid as capping agent. Next, anticancer drug doxorubicin (Dox) was used to form electrostatic conjugation with these nanoparticles. The resulting drug-nanoconjugates were characterized for their size, composition, functionality, crystallinity, along with their magnetic and optical behavior. Following that, they were treated with cultured lung carcinoma cell lines (A 549) to probe their non-toxicity and biocompatibility. Concurrently, their uptake in cells in culture was studied by optical bioimaging. In vitro studies have shown that these nanoparticles are nontoxic (using MTT assay) to cells in culture.

Synthesis of MacMillan catalyst modified with ionic liquid as a recoverable catalyst for asymmetric Diels–Alder reaction

MacMillan catalyst was modified with imidazolium ionic liquid by ester linkage and acts as recoverable and reusable catalyst for asymmetric Diels–Alder reactions. A Diels–Alder reaction between cyclopentadiene and crotonaldehyde was carried out using MacMillan catalyst modified with ionic liquid (5 mol%) using trifluoroacetic acid (5 mol%) as co-catalyst in acetonitrile–water (95u2006:u20065) at room temperature, to give 94% conversion of Diels–Alder adduct with exo/endo (1u2006:u20061.1) and 90% ee of endo product. The catalyst was recovered and reused up to 5 cycles with a slight decrease in ee and product conversion.

Size-Selective Detection of Picric Acid by Fluorescent Palladium Macrocycles

This work presents the synthesis and characterization of two palladium-based fluorescent macrocycles offering hydrogen-bonding cavities of contrasting dimensions. Both palladium macrocycles function as chemosensors for the detection of nitroaromatics, whereas the larger macrocycle not only illustrates nanomolar detection of picric acid but also transports its significant amount from an aqueous to an organic phase.

Optically and magnetically doped ormosil nanoparticles for bioimaging: synthesis, characterization, and in vitro studies

In this manuscript, we report the fabrication of a dual-modality nanoprobe involving the co-encapsulation of fluorophores and iron oxide nanoparticles within ormosil nanoparticles, and their applications in in vitro bioimaging. The entire synthesis, including microwave-mediated precipitation of the iron oxide nanoparticles, was carried out within the non-aqueous core of an oil-in-water microemulsion. The nanoparticles are spherical and monodispersed, with an average diameter of around 150 nm. After synthesis, their composition, stability, crystallinity, as well as their magnetic and optical properties were evaluated. X-ray diffraction studies of the non-encapsulated iron oxide nanoparticles showed them to be crystalline, corresponding to an α-Fe2O3 phase. However, their crystallinity was found to diminish upon ormosil encapsulation. These doped nanoparticles displayed both optical and superparamagnetic properties, by virtue of which they have the potential to serve as dual diagnostic probes. The stability of the fluorophores was found to increase upon nanoencapsulation. In vitro studies have shown that the nanoparticles are non-toxic to cells in culture and undergo efficient cellular uptake, as shown by optical bioimaging. These observations demonstrate the promise of such nanoparticles for non-toxic bioimaging applications.

Fluorescent detection of multiple ions by two related chemosensors: structural elucidations and logic gate applications

Two related chemosensors L1 and L2 display selective detection of multiple ions (Cu2+, Al3+, Cd2+ and S2−) as a result of minor variation of functional groups. Both chemosensors offer identical pyrrole-2-carboxamide fragments; however, they differ by the presence of either an ester (L1) or an acid group (L2) at a remote arene ring. While L1 shows selectivity towards the Cu2+ ion L2 is highly selective for Al3+ and Cd2+ cations as well as S2− anion. A combination of studies (Stern–Volmer plots, detection limits and Benesi–Hildebrand fittings) displays the notable sensing abilities of both chemosensors. Both chemosensors were utilized to develop logic gate-based applications by considering multiple detection of assorted ions. Structural studies provide vital details about the mode of binding between chemosensors and cations. Simple synthesis, multi-stimuli response, fast response, solution visualization, and practical detection methods (filter paper strips and polystyrene films) suggest excellent sensing potentials of both chemosensors.