Shahzad Maqsood Khan

Novel green nano composites films fabricated by indigenously synthesized graphene oxide and chitosan.

Graphene oxide (GO) was indigenously synthesized from graphite using standard Hummers method. Chitosan-graphene oxide green composite films were fabricated by mixing aqueous solution of chitosan and GO using dilute acetic acid as a solvent for chitosan. Chitosan of different viscosity and calculated molecular weight was used keeping amount of GO constant in each composite film. The structural properties, thermal stability and mechanical properties of the composite films were investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and tensile test. FTIR studies revealed the successful synthesis of GO from graphite powder and it was confirmed that homogenous blending of chitosan and GO was promising due to oxygenated functional groups on the surface of GO. XRD indicated effective conversion of graphite to GO as its strong peak observed at 11.06° as compared to pristine graphite which appeared at 26°. Moreover, mechanical analysis confirmed the effect of molecular weight on the mechanical properties of chitosan-GO composites showing that higher molecular weight chitosan composite (GOCC-1000) showed best strength (higher than 3GPa) compared to other composite films. Thermal stability of GOCC-1000 was enhanced for which residual content increased up to 56% as compared to the thermal stability of GOCC-200 whose residue was restricted to only 24%. The morphological analysis of the composites sheets by SEM was smooth having dense structure and showed excellent interaction, miscibility, compatibility and dispersion of GO with chitosan. The prepared composite films find their applications as biomaterials in different biomedical fields.

An Investigation of Ac Impedance and Dielectric Spectroscopic Properties of Conducting Chitosan-silane Crosslinked-poly (Vinyl Alcohol) Blended Films

The films of chitosan (CS)-silane crosslinked-poly(vinyl alcohol) (PVA) with different weight % were prepared. The effect on conductivity of CS/PVA blended films due to change in the concentration of PVA and temperature was investigated by impedance spectroscopy and showed good conductance properties. The complex impedance plots revealed single semicircular arcs indicating the bulk contribution to overall electrical behavior of all synthesized samples. The ac conductivity obeyed the Jonschers power law for all samples in the frequency range of 2 kHz to 2 MHz. The ionic conductivity of the films was increased with the increase in temperature for all synthesized samples which showed an increase in the number of effective charge carriers while it was decreased at a specific higher temperature for each film. The observed activation energy for CP4, CP8 and CP10 were 0.431, 0.610 and 0.425 eV, respectively. These properties showed that the films were promising materials to be employed for conducting properties.

Fabrication and performance characteristics of tough hydrogel scaffolds based on biocompatible polymers.

Novel silane crosslinked tough hydrogel scaffolds were prepared using chitosan (CS) and polyvinyl alcohol (PVA) to give network structure and scaffolds properties. The influence of crosslinking and PVA concentration on scaffolds were studied. Fourier transform infrared spectroscopy (FTIR) spectroscopy confirmed the presence of incorporated components. Tensile strength (TS) and fracture strain analysis of scaffolds were detected owing to the mutual effect of chemically and physically crosslinked network. Tough hydrogel scaffolds having 90% CS and 10% PVA exhibited TS of 49.18MPa and 10.15% elongation at break. The contact angle is less than 90° exhibited the hydrophilic nature of the scaffold. X-ray diffraction analysis (XRD) indicated the characteristics peaks fitting to CS and PVA and increase in the crystallinity of scaffolds. Cytotoxicity of scaffolds with different human fibroblast cell lines (F121, F192 and F84) for indirect method and human dermal fibroblast cell lines (F121) for direct method was evaluated. This indicated that these biomaterials were non-toxic, viable to the used cell lines, helpful in the growth of these cells and did not discharge toxic material damaging to the living cells.

In-situ crosslinked nanofiber mats of chitosan/poly(vinyl alcohol) blend: Fabrication, characterization and MTT assay with cancerous bone cells

Biocompatible crosslinked nanofiber mats of chitosan (CS)/poly(vinyl alcohol) (PVA) were fabricated using electrospinning technique. CS and PVA blends (7, 9 and 11 weight %) of prepared keeping ratios of CS: PVA to 1:4 and was crosslinked with tetraethoxysilane (TEOS). Fourier transform infrared (FTIR) analysis confirmed the existence of inter- and intramolecular hydrogen bonding between polymer chains and the development of siloxane linkage within the nanofibers. X-ray diffractometry (XRD) analysis showed an increase in the crystallinity of electrospun nanofibers after crosslinking as compared to the uncrosslinked nanofibers and with an increase in CS/PVA content. Scanning electron microscopy (SEM) micrographs exhibited the formation bead-free fibers at higher polymer concentration. The average size of the nanofibers was found in the range of 40 to 100 nm. The concentration and crosslinker content affected the mechanical and thermal properties of the nanofibers. The crosslinker has increased the tensile strength (TS) values upto 120 % and Young’s modulus by 71 % as compared to the uncrosslinked nanofibers while elongation at break was decreased in all nanofibers. The cell viability of the nanofibers was investigated by employing human cancerous bone cells (MG63). The obtained results showed that cancerous bone cells were not proliferated in the presence of nanofibers and the growth of the cells was inhibited confirming the worth of CS/PVA nanofibers against cancerous bone cells. This inherent behaviour can be exploited as base material for anticancer biomedical applications.

γ-Irradiated chitosan based injectable hydrogels for controlled release of drug (Montelukast sodium)

Novel pH-sensitive γ-irradiated low molecular weight (MW) chitosan (CS) (pre-irradiated) and poly (vinyl alcohol) (PVA) blended injectable hydrogels, crosslinked with varying concentrations of glycerol, were fabricated for drug delivery application. The effect of low MW irradiated CS on controlled drug release was evaluated to address the problem of higher viscosity and lower solubility of high MW CS. The FTIR spectra of hydrogels depicted the presence of all the incorporated functional groups and the developed interactions (physical and chemical). The surface morphology of hydrogels assessed by scanning electron microscope exhibited porous microstructure. All hydrogels were subjected to the swelling analysis in different media (water, buffer and electrolytes). The pH sensitive hydrogel samples exhibited less swelling at acidic and neutral pH while higher swelling at basic pH. CPG-0.5 showed the highest swelling at all pH media as compared to other hydrogel samples. CPG-1.0 was selected for the release analysis of drug because of its highest swelling (114.47%) in distilled water having neutral pH. It was loaded with model drug (Montelukast Sodium) during the preparation phase and studied for drug release capability. The in-vitro controlled release evaluation of hydrogel (CPG-1.0) was performed in SGF and SIF using UV-visible spectroscopy. The results confirmed their applications in injectable drug release systems as all the loaded drug was released in 30 min in SGF (pH -1.2) while the release of drug in SIF (pH -6.8) was in controlled manner (99.62% in 3 h). The improved antibacterial activity of these hydrogel films was owing to the fact that the γ-irradiated low MW CS has ruptured the bacterial cell and its metabolism more efficiently by inflowing in the cell.

Co-concentration effect of silane with natural extract on biodegradable polymeric films for food packaging

Novel biodegradable films were prepared by blending guar gum, chitosan and poly (vinyl alcohol) having mint (ME) and grapefruit peel (GE) extracts and crosslinked with nontoxic tetraethoxysilane (TEOS). The co-concentration effect of TEOS with natural extracts on the films was studied. FTIR analysis confirmed the presence of incorporated components and the developed interactions among the polymer chains. The surface morphology of the films by SEM showed the hydrophilic character due to porous network structure. The films having both ME and GE with maximum amount of crosslinker (100μL), showed maximum swelling (58g/g) and stability while the optical properties showed increased protection against UV light. This film sample showed compact network structure which enhanced the ultimate tensile strength (40.03MPa) and elongation at break (104.8%). ME/GE conferred the antioxidant properties determined by radical scavenging activity and total phenolic contents (TPC) as ME films have greater TPC compared to GE films. The soil burial test exhibited the degradation of films rapidly (6days) confirming their strong microbial activity in soil. The lower water vapour transmission rate and water vapour permeability showed better shelf life; hence, these biodegradable films are environmental friendly and have potential for food and other packaging.

Controlled release of cephradine by biopolymers based target specific crosslinked hydrogels

The novel silane crosslinked (TEOS) hydrogels based on eco-friendly biodegradable chitosan/guargum were prepared by blending with PEG to develop pH sensitive hydrogels (CGP) and achieved its hydrophilicity and target specificity for controlled release of drug. The crosslinker amount was varied to analyze its effect on the hydrogel properties and were characterized using FTIR, SEM, TGA, swelling studies (water, buffer and ionic solution) and in-vitro release of cephradine (CED). FTIR confirmed the presence of characteristic peaks and crosslinking between the components while SEM images showed the formation of clear micro- and macro-pores. The swelling behavior in water showed that compared to the controlled hydrogel, the crosslinked hydrogels revealed more swelling but a decrease in swelling with further increase in the amount of crosslinker was observed. The hydrogels showed low swelling at basic and neutral pH while maximum swelling was observed at acidic pH. This pH response made these hydrogels an ideal candidate for injectable controlled release. The CED was loaded on hydrogels and its release mechanism was studied in PBS, SGF and SIF which revealed that out of all hydrogels (CGP100, CGP150, CGP200 and CGP250), CGP100 has shown CED release of 85% in 130 min in PBS and 82.4% in SIF.

Controlled release of Montelukast Sodium from pH-sensitive injectable hydrogels

ABSTRACT pH sensitive hydrogels showed excellent drug release properties, with promise for other biomedical applications. Also, the impact of molecular weight (MW) and degree of deacetylation (DDA) of chitosan on the fabricated chitosan/poly (vinyl alcohol) (3:1 mol ratio) hydrogel with selective silane crosslinker amount was evaluated for controlled drug delivery. The FTIR spectroscopy confirmed the incorporated components and the developed interactions among the polymer chains. The hydrogel characteristics were expressed by their responsive behaviour in different environments (water, ionic media and pH). The hydrogel sample (CH1000) having chitosan with higher MW and DDA exhibited more thermal stability and bacterial growth inhibition against E.coli. All hydrogels exhibited maximum swelling at basic and neutral pH and less swelling was observed in acidic media. For drug release analysis performed in simulated gastric fluid, hydrogel showed controlled drug release in 2 h but it was more than 10%, consequently cannot be used for oral purpose. In simulated intestinal fluid, hydrogels exhibited more than 80% release within 90 min. This characteristic phenomenon at neutral pH empowered hydrogel appropriate towards injectable and targeted controlled release of applicable drug. It was concluded that the prepared hydrogel can be administered directly into the venous circulation through syringe and can be used with better results for biomedical applications. Graphical Abstract

Modification of Polyaniline

Abstract Modification of polyaniline (PANI) is significant to attain the required targeted applications in this modern era. Radiations are preferred to modify PANI because this protocol of modification does not involve any chemical agent that can introduce any impurity. In this chapter, modification of PANI via gamma irradiation, electron beam (EB) irradiation, and ion implantation technique is discussed in detail. The principles of all these techniques are also elaborated. The effect of gamma and EB irradiations on different properties including cross-linking, microstructure, mechanical and wear properties, degradation and oxidative behavior, stability and solubility of PANI are explained. In case of ion implantation technique, effects of ion implantation on concentration of radical of PANI, amount of nitrogen and hydrogen atom in PANI, electrical conductivity, stability, shrinkage effect, color change, oxidation–reduction effect, and degradation behavior of PANI are illustrated. It is found that these irradiation techniques offered constructive effects for the improvement of abovementioned properties of PANI.

Cellulaose acetate based thin film nanocomposite reverse osmosis membrane incorporated with TiO 2 nanoparticles for improved performance

In this work, cellulose acetate (CA) based thin film nanocomposite reverse osmosis (RO) membranes were fabricated using dissolution casting method by optimizing the CA/polyethylene glycol (CA/PEG-400) ratios for improved RO performance. The selectivity of optimized membrane was further enhanced by incorporating TiO2 (0-25 wt.%) nanoparticles. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were conducted to characterize control and modified membranes for the analysis of functional groups, thermal properties, morphology and structural investigation respectively. CP-2 of CA/PEG-400 (80/20) was selected for further modification with TiO2 nanoparticles. The maximum salt rejection (95.4%) was observed for the membrane having 15% TiO2 nanoparticles. Further escalation of TiO2 concentration resulted in the agglomeration of nanoparticles which subsequently decreased the permeation flux. The test results demonstrated that the modified membranes had higher salt rejection and chlorine resistance, lower degradation profile, successful inhibition of Escherichia coli growth and facilitating permeation flux compared to the control membrane.