Alak Kumar Buragohain

A novel ‘green’ synthesis of colloidal silver nanoparticles (SNP) using Dillenia indica fruit extract

In the present research we have defined a novel green method of silver nanoparticles synthesis using Dillenia indica fruit extract. D. indica is an edible fruit widely distributed in the foothills of Himalayas and known for its antioxidant and further predicted for cancer preventive potency. The maximum absorbance of the colloidal silver nanoparticle solution was observed at 421 nm when examined with UV-vis spectrophotometer.

One step preparation of a biocompatible, antimicrobial reduced graphene oxide–silver nanohybrid as a topical antimicrobial agent

A reduced graphene oxide–silver nanohybrid (Ag–RGO) was prepared by simultaneous reduction of graphene oxide and silver ions, using the aqueous extract of the Colocasia esculenta leaf. The nanohybrid demonstrated better antimicrobial activity than the individual nanomaterials. Excellent cytocompatibility was observed for peripheral blood mononuclear cells (PBMCs) and mammalian red blood cells (RBCs). An acute dermal toxicity study on wistar rats confirmed no induction of direct or indirect toxicity to the host. Thus, this nanohybrid holds potential for applications as a non-toxic topical antimicrobial agent in dressings, bandages, ointments etc.

Antibacterial and hemolysis activity of polypyrrole nanotubes decorated with silver nanoparticles by an in-situ reduction process

Polypyrrole nanotube-silver nanoparticle nanocomposites (PPy-NTs:Ag-NPs) have been synthesized by in-situ reduction of silver nitrate (AgNO3) to suppress the agglomeration of Ag-NPs. The morphology and chemical structure of the nanocomposites have been studied by HRTEM, SEM, XRD, FTIR and UV-vis spectroscopy. The average diameter of the polypyrrole nanotubes (PPy-NTs) is measured to be 130.59±5.5 nm with their length in the micrometer range, while the silver nanoparticles (Ag-NPs) exhibit spherical shape with an average diameter of 23.12±3.23 nm. In-vitro blood compatibility of the nanocomposites has been carried out via hemolysis assay. Antimicrobial activity of the nanocomposites has been investigated with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The results depict that the hemolysis and antimicrobial activities of the nanocomposites increase with increasing Ag-NP concentration that can be controlled by the AgNO3 precursor concentration in the in-situ process.

Comparative analysis of phytochemicals and nutrient availability in two contrasting cultivars of sweet potato (Ipomoea batatas L.)

Sweet potato ranks as the worlds seventh most important food crop, and has major contribution to energy and phytochemical source of nutrition. To unravel the molecular basis for differential nutrient availability, and to exploit the natural genetic variation(s) of sweet potato, a series of physiochemical and proteomics experiment was conducted using two contrasting cultivars, an orange-fleshed sweet potato (OFSP) and a white-fleshed sweet potato (WFSP). Phytochemical screening revealed high percentage of carbohydrate, reducing sugar and phenolics in WFSP, whereas OFSP showed increased levels of total protein, flavonoids, anthocyanins, and carotenoids. The rate of starch and cellulose degradation was found to be less in OFSP during storage, indicating tight regulation of gene(s) responsible for starch-degradation. Comparative proteomics displayed a cultivar-dependent expression of proteins along with evolutionarily conserved proteins. These results suggest that cultivar-specific expression of proteins and/or their interacting partners might play a crucial role for nutrient acquisition in sweet potato.

Biocompatible high performance hyperbranched epoxy/clay nanocomposite as an implantable material

Polymeric biomaterials are in extensive use in the domain of tissue engineering and regenerative medicine. High performance hyperbranched epoxy is projected here as a potential biomaterial for tissue regeneration. Thermosetting hyperbranched epoxy nanocomposites were prepared with Homalomena aromatica rhizome oil-modified bentonite as well as organically modified montmorillonite clay. Fourier transformed infrared spectroscopy, x-ray diffraction and scanning and transmission electron microscopic techniques confirmed the strong interfacial interaction of clay layers with the epoxy matrix. The poly(amido amine)-cured thermosetting nanocomposites exhibited high mechanical properties like impact resistance (>100 cm), scratch hardness (>10 kg), tensile strength (48-58 MPa) and elongation at break (11.9-16.6%). Cytocompatibility of the thermosets was found to be excellent as evident by MTT and red blood cell hemolytic assays. The nanocomposites exhibited antimicrobial activity against Staphylococcus aureus (ATCC 11632), Escherichia coli (ATCC 10536), Mycobacterium smegmatis (ATCC14468) and Candida albicans (ATCC 10231) strains. In vivo biocompatibility of the best performing nanocomposite was ascertained by histopathological study of the brain, heart, liver and skin after subcutaneous implantation in Wistar rats. The material supported the proliferation of dermatocytes without induction of any sign of toxicity to the above organs. The adherence and proliferation of cells endorse the nanocomposite as a non-toxic biomaterial for tissue regeneration.

Copper–copper oxide coated nanofibrillar cellulose: a promising biomaterial

Nanocellulose is gaining impetus as a hierarchical material in many advanced applications. The isolation of nanocellulose from easily available bio-resources is an area to be delved into thoroughly. This article highlights the isolation of nanofibrillar cellulose from an abundant natural source, Colocasia esculenta, by a chemical method. The nanofibrils were coated with copper–copper oxide nanoparticles through a ‘green’ reductive technique using the alcoholic extract of Terminalia chebula fruit. The prepared fibrils and the nanohybrid were characterized by Fourier transformed infrared spectroscopy, X-ray diffraction and transmission electron microscopic studies. The coated nanofibrils showed promising antimicrobial activity against Staphyllococcus aureus, Escherichia coli and Candida albicans. The nanohybrid was quite compatible with peripheral blood mononuclear cells (PBMC) as well as mammalian red blood cells (RBCs). The structural integrity of bovine serum albumin (BSA) was unaltered upon interaction with the nanohybrid. The biocompatible and antimicrobial nanohybrid presented here possesses high potential to be used as a biomaterial in a suitable niche of modern biomedical fields.

Extraction and characterization of microcrystalline cellulose from fodder grass; Setaria glauca (L) P. Beauv, and its potential as a drug delivery vehicle for isoniazid, a first line antituberculosis drug

Microcrystalline cellulose (MCC) is generally produced through acid hydrolysis of woody plants and agro sources. MCC synthesized from a common wild grass Setaria glauca (L) P. Beauv was characterized to explore the possibility of application in pharmaceutical industry especially as a drug delivery vehicle. The SEM, TGA, XRD and FTIR investigations of the prepared MCC reveal that the 5-30μm long, non aggregated MCC rods have high crystallinity index of 80% and were stable at 286°C. The preliminary investigation of the MCC incorporated micro beads containing isoniazid, one of the first line drugs for treatment of tuberculosis was carried out in the simulated intestinal fluid (SIF). The MCC incorporated micro beads with isoniazid drug load showed sustained release upto 24h with release of 0.521μg of isoniazid equivalent drug in the SIF system. No cytotoxicity of the MCC was observed in the haemolytic assay. The MCC also showed good antioxidant activity. Thus, the study reveals that the MCC can be prepared from an inexpensive and abundant grass species. The MCC have properties advantageous for application in the pharmaceutical industry and may be explored further in drug delivery research.

A Study in Entire Chromosomes of Violations of the Intra-strand Parity of Complementary Nucleotides (Chargaff's Second Parity Rule)

Chargaffs rule of intra-strand parity (ISP) between complementary mono/oligonucleotides in chromosomes is well established in the scientific literature. Although a large numbers of papers have been published citing works and discussions on ISP in the genomic era, scientists are yet to find all the factors responsible for such a universal phenomenon in the chromosomes. In the present work, we have tried to address the issue from a new perspective, which is a parallel feature to ISP. The compositional abundance values of mono/oligonucleotides were determined in all non-overlapping sub-chromosomal regions of specific size. Also the frequency distributions of the mono/oligonucleotides among the regions were compared using the Kolmogorov–Smirnov test. Interestingly, the frequency distributions between the complementary mono/oligonucleotides revealed statistical similarity, which we named as intra-strand frequency distribution parity (ISFDP). ISFDP was observed as a general feature in chromosomes of bacteria, archaea and eukaryotes. Violation of ISFDP was also observed in several chromosomes. Chromosomes of different strains belonging a species in bacteria/archaea (Haemophilus influenza, Xylella fastidiosa etc.) and chromosomes of a eukaryote are found to be different among each other with respect to ISFDP violation. ISFDP correlates weakly with ISP in chromosomes suggesting that the latter one is not entirely responsible for the former. Asymmetry of replication topography and composition of forward-encoded sequences between the strands in chromosomes are found to be insufficient to explain the ISFDP feature in all chromosomes. This suggests that multiple factors in chromosomes are responsible for establishing ISFDP.

In vitro method for propagation of centella asiatica (L) urban by shoot tip culture

A rapid clonal propagation system has been developed for the medicinally important herb Centella asiatica (L) Urban by shoot tip (2–3 cm long) culture. The shoot tips isolated from mature plants were inoculated on MS medium incorporated with BA alone or in combination with NAA and Kn. The optimum number of shoots (3.38) with optimum number of leaves per shoot (4.25) were attained on MS medium supplemented with 4.0 mg l−1 BA and 0.1 mg l−1 NAA. On transferring the microshoots on full strength MS medium supplemented with various concentrations of IBA (1.0-3.0 mg l−1) and NAA (0.5-2.0 mg l−1), profuse rooting (46.8 per shoot) was obtained in MS basal medium with 2.0 mg l−1 IBA with root length of 19.7 cm. Well rooted plantlets were acclimatized successfully by adjusting the temperature and humidity for 3–4 weeks after transfer to pots filled with sterilized vermiculite soil: sand (1:1)mixture. This micropropgation protocol could be useful for raising a stock of genetically homogenous material for field cultivation within a very short period.

DFT-based QSAR Models to Predict the Antimycobacterial Activity of Chalcones

In this study, antimycobacterial activity of a set of synthesized chalcone derivatives against Mycobacterium tuberculosis H37Rv was investigated by quantitative structure–activity relationship (QSAR) analysis using density functional theory (DFT) and molecular mechanics (MM+)‐based descriptors in both gas and solvent phases. The best molecular descriptors identified were hardness, EHOMO, MRA‐4 and MRB‐4′ that contributed to the antimycobacterial activity of the chalcones as independent factors. The correlation of these four descriptors with their antimycobacterial activity increases with the inclusion of solvent medium, indicating their importance in studying biological activity. QSAR models revealed that in gas phase, lower values of EHOMO, MRA‐4 and MRB‐4′ increase the antimycobacterial activity of the chalcone molecules. However, in solvent phase, lower values of EHOMO and MRB‐4′ and higher values of MRA‐4 increase their activity.