Saiqa Ikram

A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: A green expertise.

Graphical abstract

Green synthesis of silver nanoparticles using Azadirachta indica aqueous leaf extract

Abstract In this study, rapid, simple approach was applied for synthesis of silver nanoparticles using Azadirachta indica aqueous leaf extract. The plant extract acts both as reducing agent as well as capping agent. To identify the compounds responsible for reduction of silver ions, the functional groups present in plant extract were investigated by FTIR. Various techniques used to characterize synthesized nanoparticles are DLS, photoluminescence, TEM and UV–Visible spectrophotometer. UV–Visible spectrophotometer showed absorbance peak in range of 436–446 nm. The silver nanoparticles showed antibacterial activities against both gram positive (Staphylococcus aureus) and gram negative (Escherichia coli) microorganisms. Photoluminescence studies of synthesised silver nanoparticles were also evaluated. Results confirmed this protocol as simple, rapid, one step, eco-friendly, non-toxic and an alternative conventional physical/chemical methods. Only 15 min were required for the conversion of silver ions into silver nanoparticles at room temperature, without the involvement of any hazardous chemical.

Biosynthesis of gold nanoparticles: A green approach

Nanotechnology is an immensely developing field due to its extensive range of applications in different areas of technology and science. Different types of methods are employed for synthesis of nanoparticles due to their wide applications. The conventional chemical methods have certain limitations with them either in the form of chemical contaminations during their syntheses procedures or in later applications and use of higher energy. During the last decade research have been focussed on developing simple, clean, non-toxic, cost effective and eco-friendly protocols for synthesis of nanoparticles. In order to get this objective, biosynthesis methods have been developed in order to fill this gap. The biosynthesis of nanoparticles is simple, single step, eco-friendly and a green approach. The biochemical processes in biological agents reduce the dissolved metal ions into nano metals. The various biological agents like plant tissues, fungi, bacteria, etc. are used for biosynthesis for metal nanoparticles. In this review article, we summarised recent literature on biosynthesis of gold nanoparticles which have revolutionised technique of synthesis for their applications in different fields. Due to biocompatibility of gold nanoparticles, it has find its applications in biomedical applications. The protocol and mechanism of biosynthesis of gold nanoparticles along with various applications have also been discussed.

A review on biogenic synthesis of ZnO nanoparticles using plant extracts and microbes: A prospect towards green chemistry

Nanotechnology is emerging as an important area of research with its tremendous applications in all fields of science, engineering, medicine, pharmacy, etc. It involves the materials and their applications having one dimension in the range of 1-100nm. Generally, various techniques are used for syntheses of nanoparticles (NPs) viz. laser ablation, chemical reduction, milling, sputtering, etc. These conventional techniques e.g. chemical reduction method, in which various hazardous chemicals are used for the synthesis of NPs later become liable for innumerable health risks due to their toxicity and endangering serious concerns for environment, while other approaches are expensive, need high energy for the synthesis of NPs. However, biogenic synthesis method to produce NPs is eco-friendly and free of chemical contaminants for biological applications where purity is of concerns. In biological method, different biological entities such as extract, enzymes or proteins of a natural product are used to reduce and stabilised formation of NPs. The nature of these biological entities also influence the structure, shape, size and morphology of synthesized NPs. In this review, biogenic synthesis of zinc oxide (ZnO) NPs, procedures of syntheses, mechanism of formation and their various applications have been discussed. Various entities such as proteins, enzymes, phytochemicals, etc. available in the natural reductants are responsible for synthesis of ZnO NPs.

Silver Nanoparticles: One Pot Green Synthesis Using Terminalia arjuna Extract for Biological Application

Among all the nanoparticles synthesized; silver nanoparticles have attained special place in the area of nano technology because of their antimicrobial and biomedical applications. In general; their syntheses involves the use of hazardous chemicals or costly physical methods. However, the biological processes are making their ways in between and proving their advantages over them. The use of plants and their extracts is one of the most valuable methods which are gaining concerns due to their imperative biological benefits. Plants are not only beautiful but majestic because they are rich sources of various medicinally important substances. They explore the huge diversity which can be utilized towards rapid and single step protocol preparatory method for various nanoparticles keeping intact “the green principles” over the conventional ones and proving their dominance for medicinal importance. Here, in the presented work “one pot synthesis of silver nanoparticles” is described. Silver nanoparticles have world-wide desirability due to their exceptional physical and chemical properties in particular to antimicrobial activities plus being non-toxic and environmentally safe. Therefore; a simple, cost effective bio-reduction on the principle of “green synthesis” of silver nanoparticles using the Terminalia arjuna plant extract is reported. The beauty of the synthesis is: no involvement of any surfactant, catalyst or template. The aqueous silver ions are reduced to silver nanoparticles when exposed to leaves extract. The bio-reduction and stabilization of so formed silver nanoparticles was monitored by UV-Vis spectrophotometry. The synthesized silver nanoparticles were also characterized by various other techniques viz. FTIR spectroscopy, Dynamic light scattering (DLS), and TEM. FTIR spectroscopy revealed that silver nanoparticles that are functionalized with biomolecules that are present in the natural aqueous extract are themselves acting as the capping agents and stabilizing the nanoparticles. Biological evaluations of silver nanoparticles were also done against gram positive (S. aureus) and gram negative bacteria (E. coli) for their future applications in biomedicines especially for the treatment of wounds.

Kinetic and thermodynamic evaluation of adsorption of Cu(II) by thiosemicarbazide chitosan.

A modified biomacromolecule, chitosan-thiosemicarbazide framework (TSCS) as an adsorbent for Cu(II) was prepared from dialdehyde chitosan through condensation reaction with thiosemicarbazide, stabilized by the reduction reaction with sodium borohydride. TSCS was characterized by means of FT-IR and XPS. Surface morphologies were studied by FESEM and BET, which revealed the highly macro porous structure. The thermal analyses was done through TGA showing much stable chemical configuration at about ≥400°C. The experimental equilibrium data was evaluated by Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The Langmuir adsorption model was best fitted with experimental value, suggests the existence of monolayer coverage of adsorbed molecules with a maxima of 142.85mgg-1. The kinetic data was analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models and the pseudo-second-order kinetics were found for all the concentrations. The calculated thermodynamic parameters such as ΔGo, ΔH and ΔS were -2.33kJmol-1, 570.40Jmol-1 and 9.75Jmol-1K-1 respectively signifies the adsorption of Cu(II) onto TSCS is endothermic, spontaneous and a process of physisorption. The regeneration efficiency of the TSCS as an adsorbent was found to be ≥90-95% using 0.1M EDTA.

Chitosan and gelatin based biodegradable packaging films with UV-light protection.

Biopolymers are polymers obtained from biological origins and used for various biological and industrial applications. A biopolymer should be non-toxic, non-antigenic, non-irritant, non-carcinogenic, sterilisable and adequately available for their widespread applications. In this study, chitosan (CS) and gelatin (GL) based films were prepared to be used as biodegradable packaging films. CS was blended with GL to improve various physicochemical properties. The blended CSGL films were crosslinked with boric acid (BA) to improve various properties viz. light barrier properties, Water Vapour Permeability (WVP), moisture content (%), Total Solubility Matter (TSM), most important to improve the strength. The studies of transparency, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and optical microscopy confirms that the synthesized films were found to be transparent and homogenous indicating good compatibility among different components. The synthesized CS and GL based films showed UV-light barrier properties as supported by data. The tensile strength of films increases, decreases water solubility, moisture content (%) and WVP on crosslinking. In order to make the crosslinked films more flexible, Polyethylene glycol was used as plasticizer, making the films more flexible and transparent. This study indicates that these biodegradable CS and GL based films are potent to be used as packing films.

Chitosan Based Dressings for Wound Care

Biopolymer researchers have advanced new strategies to improve the properties of wound dressings over the last decade which is becoming one of the most swiftly growing fields in the biomedical and pharmacy. The advantages of these biopolymers (particularly chitosan) is that, they can be easily processed into different forms which needs to be for different biomedical applications. Chitosan is the well-known natural biopolymer which is safe to be use, biocompatible and biodegradable in nature. This review provides an outline of the chitosan properties and its biomedical properties toward applications in anti-inflammatory and wound caring management.

Characterization and physiochemical studies of crosslinked thiolated polyvinyl alcohol hydrogels

Modification and crosslinking of polyvinyl alcohol (PVA) by thiolation using thioglycolic acid (TGlA) and various crosslinkers were carried out. The crosslinked thiolated PVA (TPVA) hydrogels were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infra red spectroscopy coupled with thermal analysis (TG-FTIR) techniques. The crosslinking of the resultant material was carried out using three crosslinker sodium trimetaphosphate (STMP), glyoxal and boric acid. The influence of esterification and crosslinking on the physical and chemical properties of the material was studied. XRD showed that after crosslinking the crystallinity of TPVA hydrogels decreased. These results were further substantiated by DSC observations. The thermal stability of the TPVA hydrogels is enhanced. A significant variation in the initial decomposition temperature was observed with respect to different STMP crosslinked samples having varying TGlA concentration and different crosslinkers. The coupled TG-FTIR studies of crosslinked samples at different temperatures show that the evolution of sulfur-containing gases (carbon disulfide and carbon monosulfide) is being prominent for this material.

Potentiometric polymeric membrane electrodes for mercury detection using calixarene ionophores.

It is here established that potentiometric polymeric membrane electrodes based on electrically neutral ionophores are a useful analytical tool for the detection of heavy metal ions from environmental and industrial waste water. PVC based membrane containing p-tert-butyl-calix[4]arenethioether derivative as active material along with sodiumtetraphenylborate (NaTPB) as solvent mediator and dibutylphthalate as a plasticizer in the ratio 45:9:460:310 (w/w%) (I:NaTPB:DBP:PVC) exhibits good properties with a Nernstian response of 29.50+/-1.0 mV per decade of activity and a working concentration range of 7.2 x 10(-8)-1.0 x 10(-1) M. The electrode gave more stable potential readings when used around pH 2.5-6.8 and exhibits fast response time of 14 s. The sensors were found to work satisfactorily in partially non-aqueous media up to 40% (v/v) content of acetone, methanol or ethanol and could be used over a period of 7-9 months. Excellent selectivity for Hg(2+) ions is indicated by match potential method and fixed interference method. The sensors could be used successfully in the estimation of mercury in different sample.