Biplab Bhowmick

Anticancer (in vitro) and antimicrobial effect of gold nanoparticles synthesized using Abelmoschus esculentus (L.) pulp extract via a green route

Green synthesis of gold nanoparticles (Au NPs) using Abelmoschus esculentus (L.) pulp extract has been elaborately studied and reported here. The Au NPs have been characterized using several techniques. Optical analysis indicates adequate stability of the synthesized Au NPs, while FTIR analyses the fact that phytochemicals present in the Abelmoschus esculentus (L.) pulp extract play the key role in stabilizing the Au NPs. Morphological study shows that the nanoparticles are mostly spherical in shape with an average particle size of ∼14 nm, and these results are comparable with the particle size obtained from XRD. The selected area electron diffraction pattern indicates the crystalline nature of the Au NPs, which is further confirmed from XRD studies. The present study also demonstrates the in vitro efficacy of Au NPs against Jurkat cells. Results show that the IC50 dose of Au NPs is capable of significantly elevating intracellular reactive oxygen species and diminishing mitochondrial membrane potential, indicating the effective involvement of apoptosis in cell death. Furthermore, the synthesized Au NPs show a sufficient degree of antimicrobial activity against different types of bacteria. These results clearly show that the Abelmoschus esculentus (L.) pulp synthesized Au NPs have excellent medicinal applications.

Effect of xanthan gum and guar gum on in situ gelling ophthalmic drug delivery system based on poloxamer-407

The aim of this investigation was to develop a novel in situ gelling formulation based on poloxamer-407 (PM) for the sustained release of an ophthalmic drug. In an attempt to reduce the concentration of PM without compromising the in situ gelling capability and also to increase the drug release time, xanthan gum (XG) and guar gum (GG) were added into PM to develop different formulations. At concentrations of 18% and above, the PM was able to undergo sol-gel transition below body temperature. It was found that XG and GG at a weight ratio of 3:7 were able to convert PM solution into gel below body temperature at PM concentrations below 18%. Both the in vitro and in vivo studies indicated that the PM with an XG-GG combination had a better ability to retain the drug than PM itself. The results indicated that the developed in situ gelling formulations containing PM with XG-GG may be a better alternative than a conventional eye drop.

Effect of clay concentration on morphology and properties of hydroxypropylmethylcellulose films

Hydroxypropylmethylcellulose (HPMC)/montmorillonite (MMT) nanocomposite films are prepared by solution intercalation method. Mechanical, thermal, moisture absorption, optical clarity and water vapor permeability of HPMC/MMT nanocomposite films are measured. X-ray diffraction (XRD) and transmission electron microscopic (TEM) results establish formation of partially intercalated and partially exfoliated HPMC/MMT nanocomposite films. In presence of MMT, the tensile strength, tensile modulus and elongation at break of HPMC films are improved. The thermal stability of HPMC/MMT nanocomposites is better than pure HPMC. The moisture absorption of HPMC film measured in 75% of constant relative humidity is reduced with loading of MMT. Optical clarity of HPMC film is almost unaffected in presence of MMT. Water vapor permeability of HPMC decreases in presence of nanoclay due to increasing tortuous path for diffusion.

Synergistic effect of salt mixture on the gelation temperature and morphology of methylcellulose hydrogel

Gelation temperature of methylcellulose (MC) can be altered by adding different additives. Pure MC showed sol-gel transition at 60°C. Sodium citrate and sodium tartrate were used alone and in combination to see the effect of individual salt and combination of salts on the gelation temperature of MC. The gelation temperature of all the binary and ternary combinations of MC and salts were measured with different methods such as test tube tilting method (TTM), UV-vis spectroscopy, viscometry, and by rheometer and also the morphology of gels were characterized with the help of environmental scanning electron microscopy (ESEM). It was observed that when 0.1 M sodium citrate (NaC) and 0.1 M sodium tartrate (NaT) were used separately, the gelation temperature of MC was reduced up to 44°C and 47°C respectively but when mixture of NaC and NaT (0.1 (M) NaC and 0.1 (M) (NaT)) were used the gelation temperature was further reduced to 36°C. It was clear from ESEM images that when NaC and NaT were used separately the formation of network was not distinguishable. But, well-connected network structure was observed when a mixture 0.1 M NaC and 0.1 M NaT was used.

Effect of PEG–salt mixture on the gelation temperature and morphology of MC gel for sustained delivery of drug

Gelation temperature of MC was reduced from 59°C to 54°C with the addition of 10% PEG. Sodium tartrate (NaT) and sodium citrate (NaC) were added to the MC-PEG solution to further reduce the gelation temperature close to physiological temperature. Different techniques were used to measure the gelation temperature of all formulations. It was observed that NaC was more effective in reducing the gelation temperature of MC-PEG combination than NaT. Environmental scanning electron microscopy (ESEM) images of hydrogels containing NaC and NaT showed that NaC containing hydrogel having an interconnected microporous structure instead of the hollow rod like structure as in the case of NaT containing hydrogel. In vitro drug release studies showed that drug release time increased from 6 to 9h by only changing the type of salt from NaT to NaC in MC-PEG combination.

Effect of PVA on the gel temperature of MC and release kinetics of KT from MC based ophthalmic formulations

The effect of molecular weight of poly(vinyl alcohol) (PVA) and sodium chloride on the gelation temperature of methylcellulose (MC) was studied with the objective to develop a MC based formulation for sustained delivery of ketorolac tromethamine a model ophthalmic drug. Pure MC showed sol-gel transition at 61.2 °C. In order to reduce the gelation temperature of MC and to increase the drug release time, PVA was used. Different techniques such as test tube tilting method, UV-vis spectroscopy, viscometry and rheometry were used to measure gelation temperature of all the binary combinations of MC and PVA. It was observed that the gelation temperature of MC was reduced with the addition of 4% PVA and also the extent of reduction of the gelation temperature of MC was dependent on the molecular weight of PVA. The strong interactions between MC and PVA molecules were established using Fourier transform infrared spectroscopy. To study the in vitro drug release properties of the MC-PVA binary combinations, 6% sodium chloride was used to reduce the gelation temperature further up to physiological temperature. It was observed that the drug release time increased from 5 to 8h with the increase of molecular weight of PVA from 9×10(3) to 1.3×10(5) and this was due to the higher viscosity, better gel strength and greater interactions between the drug and PVA molecules in case of PVA (1.3×10(5)) compared to PVA (9×10(3)). In order to have an idea about the nature of interactions between the functional moieties of the drug and the polymer unit of PVA, a theoretical study was carried out.

Investigation on Sodium Benzoate Release from Poly(Butylene Adipate‐Co‐Terephthalate)/Organoclay/Sodium Benzoate Based Nanocomposite Film and Their Antimicrobial Activity

Polymeric nanocomposites embedded with nontoxic antimicrobial agents have recently gained potential industrial significance, mainly for their applicability to preserve food quality and ensure safety. In this study, a poly(butylene adipate-co-terephthalate) (PBAT)/organoclay (CMMT) based nanocomposite film doped with sodium benzoate (SB) as antimicrobial agent was prepared by a solution mixing process. A homogenous dispersion of organoclay (cetyltrimethylammonium-modified montmorillonite [CMMT]) in PBAT matrix was observed by X-ray diffraction and transmission electron microscopy. PBAT/CMMT nanocomposite film showed higher barrier properties against water and methanol vapor compared to the PBAT film. The release of SB from PBAT and its nanocomposite film was measured and the relevant data were fitted to the Weibull model. The higher values of Weibulls shape factor and scale parameter as corroborated by experimental findings indicated faster rate of SB release from PBAT/CMMT/SB nanocomposite film, when compared to the pristine PBAT film. Bacterial inhibition studies were accomplished against 2 food pathogenic bacteria, Bacillus subtilis and Staphylococcus aureus, by determining the zone of inhibition and corresponding growth profiles. Both bacterial inhibition studies and growth profiles established that PBAT/CMMT/SB demonstrated better antimicrobial activity than PBAT/SB film. Therefore, PBAT/CMMT/SB nanocomposite film can be used for food packaging application as it showed good barrier properties and antimicrobial activity against food pathogenic bacteria.

Green one step morphosynthesis of silver nanoparticles and their antibacterial and anticancerous activities

Bile salts carry out a vital bioactive responsibility among the various physiologically important molecules. The use of bile acids and their conjugates in nanoscience is a novel idea, which opens up fascinating prospects and gives rise to various versatile properties. Sodium cholate, a biosurfactant which is environmentally safe, has been used to reduce and stabilize silver nitrate solution. The silver nanostructures thus produced are crystalline and anisotropic in nature and show different types of particle shapes and sizes depending on the reaction conditions including star and wire shapes which have not been reported earlier, by simply varying the reaction conditions. The silver precursor concentration and the ratio of sodium cholate to silver precursor were the key factors which controlled the morphosynthesis. The formation of the silver NPs was monitored using UV-vis spectrophotometry. The transmission electron microscopy (TEM) technique was used to study the morphology of the synthesized NPs. Fourier transform infrared (FT-IR) spectroscopy was used to identify the interaction of sodium cholate with the synthesized NP. The possible mechanistic role of sodium cholate in the reduction and stabilization of silver nanoparticles (Ag NPs) has also been discussed. The obtained Ag NPs exhibit antibacterial and anticancerous activities. The present study also explores the cytotoxic role of Ag NPs in KG-1A (human acute myeloid leukemia) and K562 (human chronic myeloid leukemia) cell lines.

Dynamics of sex expression and chromosome diversity in Cucurbitaceae: a story in the making

The family Cucurbitaceae showcases a wide range of sexual phenotypes being variedly regulated by biological and environmental factors. In the present context, we have tried to assemble reports of cytogenetic investigations carried out in cucurbits accompanied by information on sex expression diversities and chromosomal or molecular basis of sex determination in dioecious (or other sexual types, if reported) taxa known so far. Most of the Cucurbitaceae tribes have mixed sexual phenotypes with varying range of chromosome numbers and hence, ancestral conditions become difficult to probe. Occurrence of polyploidy is rare in the family and has no influence on sexual traits. The sex determination mechanisms have been elucidated in some well-studied taxa like Bryonia, Coccinia and Cucumis showing interplay of genic, biochemical, developmental and sometimes chromosomal determinants. Substantial knowledge about genic and molecular sex differentiation has been obtained for genera like Momordica, Cucurbita and Trichosanthes. The detailed information on sex determination schemes, genomic sequences and molecular phylogenetic relationships facilitate further comprehensive investigations in the tribe Bryonieae. The discovery of organ identity genes and sex-specific sequences regulating sexual behaviour in Coccinia, Cucumis and Cucurbita opens up opportunities of relevant investigations to answer yet unaddressed questions pertaining to floral unisexuality, dioecy and chromosome evolution in the family. The present discussion brings the genera in light, previously recognized under subfamily Nhandiroboideae, where the study of chromosome cytology and sex determination mechanisms can simplify our understanding of sex expression pathways and its phylogenetic impacts.

Effect of carrageenan and potassium chloride on an in situ gelling ophthalmic drug delivery system based on methylcellulose

Our research is devoted to developing a methylcellulose (MC) based in situ gelling ophthalmic formulation using pilocarpine hydrochloride as a model drug, containing different proportions of i (iota)-carrageenan and potassium chloride. This study will evaluate the utility of the proposed formulation to be a substitute for traditional eye drops. Use of both i-carrageenan and potassium chloride of definite wt% effectively reduces the gel temperature of the virgin MC solution from 60 °C to 33.5 °C which is below physiological temperature. The conventional methods like test tube tilting, and viscosity measurements are used to determine the gelation temperature while the gels are subjected to swelling as well as a gel dissolution study. Subsequently, the outcome from in vitro and in vivo studies confirms that the present system may be a better alternative compared to conventional eye drops.