Brijesh Rathi

Algae as crucial organisms in advancing nanotechnology: a systematic review

As nanotechnology is expanding to several commercial fields, there is a need of ecofriendly and energy-efficient methods for the synthesis of nanoparticles. Algae have been discovered to reduce metal ions and subsequently for the biosynthesis of nanoparticles. Since algae-mediated biosynthesis of nanoparticles is an ecofriendly, economical, high-yielding, expeditious and energy-efficient method, a large number of studies have been published in the last few years. This review article therefore is focused on recent progress on the utilization of algae of various classes, viz., Cyanophyceae, Chlorophyceae, Phaeophyceae, Rhodophyceae, etc. for the synthesis of nanoparticles, their characterization and the possible mechanisms involved.

Single crystal growth of ninhydrin by unidirectional Sankaranarayanan–Ramasamy (SR) method by using a glass ampoule for nonlinear optical applications

An organic nonlinear optical single crystal of ninhydrin was grown by Sankaranarayanan–Ramasamy (SR) method by using specially designed glass ampoule. The good quality seed crystal has been prepared by conventional solution growth technique using double distilled water as the solvent. The lattice dimension of the grown specimen was identified from the powder X-ray diffraction analysis and found that it crystallized in a monoclinic system with non-centrosymmetric space group P21. The presence of functional groups was examined by Fourier transform infrared (FTIR) analysis and it was found that there was no incorporation of foreign elements during crystallization. The surface defects were assessed by optical microscope and the dielectric constant and dielectric loss were carried out by LCR meter. Laser damaged threshold, relative second harmonic generation (SHG) and phase matching were measured by using a high intensity Nd:YAG laser as a source having the wavelength of 1064 nm. Its thermal stability has been assessed by TG–DTA and specific heat measurements with respect to different temperatures. The optical studies show that the crystal has transmittance ability of light in the entire visible region.

Synthesis and single crystal growth of L-proline cadmium chloride monohydrate and its characterization for higher order harmonic generation applications

The semi-organic non linear optical single crystal of L-proline cadmium chloride monohydrate was successfully synthesized and the single crystal was grown by a slow evaporation solution growth technique, using double distilled water as the solvent. The lattice dimensions of the grown crystal were examined by powder X-ray diffraction and it was found to belong to the orthorhombic crystal system with a noncentrosymmetric space group. Its crystallinity was assessed by a high resolution X-ray diffraction method and its structural imperfections were recorded using X-ray topography. The presence of functional groups was identified from heteronuclear correlation methods. Its optical behavior was examined by birefringence and photoluminescence and its optical constants were determined from UV-Vis. analysis. Its thermal and third order nonlinear optical properties were characterised by photopyroelectric and Z-scan methods, respectively. The mechanical and ferroelectric behavior was also assessed on the grown single crystal of L-proline cadmium chloride monohydrate.

Bulk growth of ninhydrin single crystals by solvent evaporation method and its characterization for SHG and THG applications

Ninhydrin is a well-known compound generally used in amino acid synthesis and also for detecting the latent fingerprints on porous surfaces. Single crystals can be grown by dissolving the compound in double distilled water at ambient temperature, and can be used as a potential material for second and third harmonic generation applications. The grown specimen was subjected to different characterization techniques in order to find out its suitability for device fabrication. Its lattice dimensions have been confirmed by X-ray powder diffraction and its crystalline quality has been assessed by high resolution X-ray diffraction and X-ray topography methods. The presence of functional groups was identified from HETCOR analysis and confirmed the absence of impurities during crystallization. Its optical properties have been examined by photoluminescence and birefringence analyses. Its thermal parameters such as thermal diffusivity, thermal conductivity and specific capacity have been carried out by following photopyroelectric method. Third order nonlinear optical measurements have been carried out using Z-scan technique and its nonlinear optical absorption coefficient has been determined.

Design, synthesis and biological evaluation of functionalized phthalimides: A new class of antimalarials and inhibitors of falcipain-2, a major hemoglobinase of malaria parasite

Phthalimides functionalized with cyclic amines were synthesized, characterized and screened for their in vitro antimalarial efficacy against Plasmodium falciparum (Pf3D7). Of all the listed phthalimides evaluated, 14 and 24 were identified as potent antimalarial agents as advocated by assessment of their ability to inhibit [(3)H] hypoxanthine incorporation in the nucleic acid of parasites. In addition, phthalimides 14 and 24 were incubated for 60 and 90h and an enhanced antimalarial effect was noticed with increase in time to great extent. A reduction in IC50 values was observed with increase in exposure time of the parasite to the compounds. A symmetric phthalimide, 24 possessing piperazine as linker unit was identified as the most potent antimalarial agent with IC50 values of 5.97±0.78, 2.0±1.09 and 1.1±0.75μM on incubation period of 42, 60 and 90h, respectively. The abnormal morphologies such as delay in developmental stages, growth arrest and condensed nuclei of parasite were observed with the aid of microscopic studies upon exposure with 14 and 24. The evaluation of 14 and 24 against chloroquine resistant strain, (Pf7GB) of P. falciparum afforded IC50 values, 13.29±1.20 and 7.21±0.98μM, respectively. The combination of 24 with artemisinin (ART) showed enhanced killing of parasite against Pf3D7. Further, all phthalimides were evaluated for their activity against falcipain-2 (FP2), a major hemoglobinase of malarial parasite. The enzymatic assay afforded 6 as most active member against FP2. To the best of our knowledge this is the initial study represents phthalimide protected amino acids functionalized with cyclic amines as potent antimalarial agents.

Functionalized hydroxyethylamine based peptide nanostructures as potential inhibitors of falcipain-3, an essential proteases of Plasmodium falciparum

Self-assembled peptide based nanostructures gained enough popularity due to their easy biocompatibility and numerous potential applications. An excellent model of self-assembly of hydroxyethylamine based peptide nanostructures was synthesized and characterized by DLS and TEM. Spherical nano structures of I and III were observed with particle size ∼50 and ∼80nm, respectively. Further, I and III were screened against anti-malarial target, falcipain-3 (FP3), a crucial cysteine protease involved as a major hemoglobinase of Plasmodium falciparum. Interestingly, compound III completely inhibited the activity of FP3. The effective concentration (1.5μM) of III found to be more potent than I. This biochemical result was substantiated by molecular-docking studies indicating III to be best inhibitor of FP3. This is the first report showing that bis hydroxethylamine based peptide nanostructures could be very effective inhibitor of malarial cysteine proteases.

Synthesis and nucleation studies on L‐leucine hydrobromide: a promising nonlinear optical material

To achieve good quality bulk size crystal growth, an assessment of the nucleation kinetics of a semi-organic l-leucine hydrobromide (L-LHBr) crystal was carried out using double-distilled water as solvent medium. The effect on metastable zone width (MSZW) with increasing temperature and on induction period with varied supersaturation level was determined experimentally and was found to be very well in accordance with the nucleation theory prospects. Thereafter, various other nucleation parameters, such as Gibbs free energy and interfacial energy, were also determined. The knowledge of these nucleation parameters indicated the requisite temperature domain and the appropriate growth technique, leading to the successful single-crystal growth of L-LHBr by slow cooling in the temperature range 298-291 K. The cooling rate of 0.25 K per day was optimized after repeated trials. X-ray diffraction and Raman analysis were performed on grown crystals for the verification of the material. High-resolution X-ray diffraction analysis was used to assess the crystalline perfection of the grown crystals. To further explore the properties of the grown crystals, photoluminescence and time decay studies, etching analysis, and Z-scan measurements were performed.

Magnetic iron oxide nanoparticles encapsulating horseradish peroxidase (HRP): synthesis, characterization and carrier for the generation of free radicals for potential applications in cancer therapy

This article reports a method of preparation of iron oxide nanoparticles using a reverse micellar (water-in-oil) approach. We have encapsulated horseradish peroxidase (HRP) in iron oxide nanoparticles. HRTEM, XRD, and DLS analyses showed that the average diameter of these particles was around 20 nm, 20.5 nm, and 30 nm, respectively, and the particles were highly monodispersed with spherical morphology. The entrapment efficiency of HRP was found to be as high as 92%. Practically, the entrapped enzyme shows zero leachability for up to 30 days. Enzyme entrapped in iron oxide nanoparticles followed Michaelis–Menten kinetics and showed higher stability towards temperature change as compared to free enzyme. Entrapped enzyme is stable at up to 65 °C; however, the free enzyme starts to lose its activity above 38 °C. The entrapped enzyme, HRP, has been used to convert a benign prodrug, indole-3-acetic acid (IAA), to a toxic oxidized product, and its toxic effect has been tested on cancerous cell lines through thiazolyl blue tetrazolium blue (MTT) assay. MTT assay on two cancer cell lines revealed that indole acetic acid (IAA), the prodrug alone, had no cytotoxic effect, and it became active only after oxidative decarboxylation by HRP. The benign substrate IAA reaches the cells and is oxidized by HRP. IAA, on reacting with HRP, forms free radicals such as indolyl, skatole and peroxyl radicals. This creates severe oxidative stress in the cancer cells, resulting in cell death.

Hydroxyethylamine Based Phthalimides as New Class of Plasmepsin Hits: Design, Synthesis and Antimalarial Evaluation.

A novel class of phthalimides functionalized with privileged scaffolds was designed, synthesized and evaluated as potential inhibitors of plasmepsin 2 (Ki: 0.99 ± 0.1 μM for 6u) and plasmepsin 4 (Ki: 3.3 ± 0.3 μM for 6t), enzymes found in the digestive vacuole of the plasmodium parasite and considered as crucial drug targets. Three compounds were identified as potential candidates for further development. The listed compounds were also assayed for their antimalarial efficacy against chloroquine (CQ) sensitive strain (3D7) of Plasmodium falciparum. Assay of twenty seven hydroxyethylamine derivatives revealed four (5e, 6j, 6o and 6s) as strongly active, which were further evaluated against CQ resistant strain (7GB) of P. falciparum. Compound 5e possessing the piperidinopiperidine moiety exhibited promising antimalarial activity with an IC50 of 1.16 ± 0.04 μM. Further, compounds 5e, 6j, 6o and 6s exhibited low cytotoxic effect on MCF-7 cell line. Compound 6s possessing C 2 symmetry was identified as the least cytotoxic with significant antimalarial activity (IC50: 1.30 ± 0.03 μM). The combined presence of hydroxyethylamine and cyclic amines (piperazines and piperidines) was observed as crucial for the activity. The current studies suggest that hydroxyethylamine based molecules act as potent antimalarial agent and may be helpful in drug development.

Entry of chiral phthalimides with significant second order nonlinear optical and piezoelectric properties

Three new chiral phthalimides have been synthesized and characterized. Phthalimides (1–3) possess an acentric structure as revealed by structural investigation. Compounds 1 and 2 crystallize in an orthorhombic system with the space group P212121, however the monoclinic system with the chiral space group P21 is observed for 3. The presence of C–H⋯O hydrogen bonds in 1–3 facilitates the construction of several supramolecular structures. Helical structural motifs are also observed. The maximum value of hyperpolarizability (β), 159.9446 × 10−30 esu calculated for compound 3 is several times greater than that of urea. On the other hand 1 and 2 have hyperpolarizabilities of 10.8063 × 10−30 and 121.9519 × 10−30 esu, respectively. The polycrystalline samples of 1–3 were assessed for a second-harmonic generation response, which was found to be 8.8, 10.2 and 9.7 mV respectively. Further, compounds 1–3 showed d33 values of 0.93, 1.97 and 1.88 pC N−1 respectively. The present investigation demonstrates chiral phthalimides as effective contenders for nonlinear optical and piezoelectric properties.