Mudasir Ahmad

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.

Preparation and characterization of antibacterial thiosemicarbazide chitosan as efficient Cu(II) adsorbent.

In the present work a method has been developed for the preparation of thiosemicarbazide-chitosan (TSCS) exploring the evaluation of enhanced adsorption of metal ions and antibacterial activities via derivatization. The splitting of carbon-carbon (C-2 and C-3) bond of vicinal diols of the chitosan chain is planned in a way to figure a Schiff base intermediate which undergoes the addition reaction in order to enhance total nitrogen and sulphur content for the chelation of Cu(II) ions from aqueous solutions in a batch adsorption system. Fourier transform infrared spectroscopy (FT-IR), (1)H NMR, elemental analysis (CHN analyzer), X-ray diffraction (XRD) and differential scanning calorimetric (DSC) analyses were used for the characterization of the end product. Surface morphologies were also studied by scanning electron microscopy (FESEM). The adsorption results showed that maximum adsorption was achieved at a dose concentration of 1.5 g/L, temperature of 25 °C with contact time of 20 min. The adsorption properties of TSCS toward Cu(II) ions were evaluated and found to be 99 ± 1%. The antibacterial properties were evaluated against Escherichia coli bacteria confirming that the modified material (TSCS) possess enhanced antibacterial activities when compared with the virgin chitosan.

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 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.

Versatile nature of hetero-chitosan based derivatives as biodegradable adsorbent for heavy metal ions; a review

The polyfunctional chitosan can act as the biological macromolecule ligand not only for the adsorption and the recovery of metal ions from an aqueous media, but also for the fabrication of novel adsorbents which shows selectivity and better adsorption properties. The unmodified chitosan itself, a single cationic polysaccharide, has hydroxyl and amine groups carrying complex properties with the metal ions. In addition, the selectivity of metal ions, the adsorption efficiency and adsorption capacity of the adsorbent can be modified chemically. This review covers the synthetic strategies of chitosan towards the synthesis of hetero-chitosan based adsorbents via chemical modifications in past two decades. It also includes how chemical modification influences the metal adsorption with N, O, S and P containing chitosan derivatives. Hope this review article provides an opportunity for researchers in the future to explore the potential of chitosan as an adsorbent for removal of metal ions from wastewater.

Chitosan centered bionanocomposites for medical specialty and curative applications: A review

The polyfunctional nature of chitosan enables its application not only in polymer technology but also shows their importance in the field of nanotechnology for the fabrication of the wide spectrum of functional nanomaterials in biomedical field. Chitosan is a poly aminosaccharide with appealing structure composed of β-(1→4)-linked D-glucosamine (deacetylated unit) and N-acetyl-d-glucosamine (acetylated unit). It has various functional groups that enriches for various properties such as antibacterial, mucoadhasive, nontoxic, biodegradable, biocompatible. With the advancement of material technologies, chitosan is being chemically modified into self-assembled nanocomposites for advanced biomedical applications. This review article demonstrate the various schemes for the preparation of chitosan nanocomposites from different functional material, focusing on their application specifically in tissue engineering, drug and gene delivery, wound healing and bioimaging.

Chitosan based nanocomposites for drug, gene delivery, and bioimaging applications

Abstract Nanocomposites of chitosan are novel materials with very less aged history and proving their utilities in biomedical application as well as in pharmaceuticals. Chitosan is a polyaminosaccharide with appealing physical and biological features that have attracted attention due to their outstanding properties related to bioabsorbable, biocompatible and antibacterial activity. Additionally low immunogenicity, controlled release behavior, muco-adhesive, and structural functionality have been useful for chemical modifications to prepare new functional materials for the application in drug and gene delivery and bioimaging. This chapter discusses the progresses in the preparation and application of chitosan nanocomposites toward different kinds of applications.