N. Gomathi

High-sensitivity ascorbic acid sensor using graphene sheet/graphene nanoribbon hybrid material as an enhanced electrochemical sensing platform.

A novel electrode material of graphene sheet/graphene nanoribbon (GS/GNR) hybrid material was developed by incorporating graphene nanoribbons into graphene nanosheets through simultaneous chemical reduction of graphene oxide sheets and graphene oxide ribbons. The structure and properties of synthesized GS/GNR were characterized by transmission electron microscope, scanning electron microscope, X-ray diffraction, Brunauer Emmett Teller measurements and Fourier transform infrared spectroscopy. This work compares the electro catalytic performance of the GS/GNR, chemically reduced graphene oxide sheets (CRGOS) and GS/carbon nanotube (CNT) by modifying the glassy carbon electrode (GCE) using ascorbic acid (AA) as analyte. The electrochemical impedance spectroscopy revealed that the charge transfer resistance of GS/GNR modified electrode was less than that of CRGOS modified electrode and bare GCE. The cyclic voltammetric sensing of GS/GNR modified electrode towards AA was negatively shifted (0.08 V) compared to CRGOS, GS/CNT modified electrode and bare GCE (0.222, 0.150 and 0.666 V). This catalytic oxidation allows an amperometric detection of AA with a detection limit of 230 nM and sensitivity of 22 nA μM(-1) cm(-2). GS/GNR modified GCE exhibited a high selectivity for ascorbic acid in the presence of other interferents like dopamine, uric acid and citric acid.

Recent trends in nano-based drug delivery systems for efficient delivery of phytochemicals in chemotherapy

The advent of nanotechnology has revolutionized various scientific inventions, out of which the debut of nanomedicine is outstanding. Especially, research has embarked on nano-drug delivery for treating cancer. Natural compounds present in plants, namely phytochemicals, have been extensively exploited for their anticancer properties. Despite their excellent anticancer abilities, phytochemicals are limited by their low water solubility and poor bioavailability. However, the field of nanotechnology has overcome these limitations. This review focusses on various methods of nano-drug delivery of phytochemicals against the killer disease, cancer. Common carriers that were employed ranged from micelles, with a polymeric base, to dendrimers, liposomes and nanoparticles. The phytochemicals were found to become more soluble when delivered by the nanocarriers and exhibited a remarkable effect on the cancer cells, compared to their free form. More interestingly, the half-maximal dose of the phytochemical was reduced significantly when it was delivered by the nanocarrier. On the whole, this review encourages the idea of “cancer-nanotechnology” after in-depth clinical studies on these phytochemical-loaded nanocarriers. Moreover, it will epitomize the nanocarriers as a crusader in improving cancer chemotherapy by reducing undesired effects and will invigorate site-specific drug delivery.

Enhanced Cell Adhesion to Helium Plasma-Treated Polypropylene

Materials used for biomedical applications are required to have suitable surface properties since they depend more on the surface properties than on the bulk properties. Surface properties greatly influence the cell adhesion and its behavior either directly by guiding cell spreading or indirectly by controlling proteins adsorption and their structural rearrangement on the material. Modulation of physical and chemical properties of polymers by various treatments can render the substrates adhesive for cells in a culture. In the present study, polypropylene surface was modified using helium plasma to enhance cell adhesion to its surface. The experiments were run according to the central composite design of response surface methodology to optimize the process conditions. The effects of the process variables, namely, RF power, pressure, flowrate and treatment time on surface energy and percentage weight loss were studied through central composite design (CCD). A statistical model relating the process variables and the responses was developed. The improved hydrophilicity of polypropylene through helium plasma treatment was observed from its surface energy data. Changes in surface chemistry and surface morphology were studied by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Enhanced cell adhesion to polypropylene treated with helium plasma at the optimum conditions, obtained from the statistical design, was observed from cell adhesion test and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay with L929 mouse fibroblast cells.

Electrochemical performance of nitrogen and oxygen radio-frequency plasma induced functional groups on tri-layered reduced graphene oxide

Tri-layered reduced graphene oxide with better graphitization was synthesized and functioned using radio frequency N2 and O2 plasma. The layer numbers of reduced graphene oxide were determined by atomic force microscopy (AFM) and x-ray diffraction (XRD). The effect of plasma treatment on crystal structure, surface morphology and chemical composition were studied from XRD, transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Fourier transforms infrared spectroscopy (FTIR) and Raman spectroscopy. The chemical species present in N2/O2 plasma during functionalization of tri-layered reduced graphene oxide was analyzed by optical emission spectroscopy. Tri-layered reduced graphene oxide and functioned tri-layered reduced graphene oxide exhibits higher electrochemical performance towards ferrocyanide redox reaction than glassy carbon and platinum electrode with much decrease in overpotential. This indicates that tri-layered reduced graphene oxide and N2/O2 functionalized tri-layered reduced graphene oxide are promising working electrodes in the application of electrochemical based biosensor.

Investigation on Argon–Oxygen Plasma Induced Blood Compatibility of Polycarbonate and Polypropylene

Surface properties of polycarbonate and polypropylene were modified using low pressure radiofrequency argon–oxygen mixture plasma in order to increase their wettability and make them useful for biomedical applications. The effects of process variables on wettability and weight loss were studied statistically using response surface methodology. Increased surface energies were observed for both argon–oxygen plasma treated polycarbonate and polypropylene. Formation of aldehyde and hydroxyl groups on polycarbonate and hydroxyl group on polypropylene were the surface chemistry changes observed by means of Fourier transform infrared spectroscopy. Qualitative analysis of surface morphology was performed through scanning electron microscopy. A statistical model was developed relating the process variables with the responses: surface energy and percentage weight loss. The obtained statistical models were optimized to maximize the surface energy and minimize the percentage weight loss. Blood compatibility of the polymers was tested for control sample and polymers treated with argon–oxygen plasma at optimized conditions by measuring the partial thromboplastin time. Increased partial thromboplastin time (PTT) was observed for both polycarbonate (144 s) and polypropylene (149 s) after plasma treatment compared to both control samples (128 s).

Helium Plasma Treatment to Improve Biocompatibility and Blood Compatibility of Polycarbonate

Radiofrequency discharge of helium gas at low pressure was employed to modify surface properties of polycarbonate. The effects of process parameters on wettability and plasma etching were determined by monitoring surface energy and weight loss, respectively. Quadratic equations for surface energy and weight loss, in terms of process variables, namely power, pressure, flowrate and treatment time were developed. Multiple response optimization was performed using central composite design (CCD) of response surface methodology (RSM) to maximize the surface energy and minimize the weight loss. Helium plasma treated polycarbonate resulted in increased hydrophilicity. From optical emission spectroscopic studies helium was identified as excited and metastable atom and ions which caused surface chemistry and morphology changes. Enhanced biocompatibility in terms of increased cell adhesion and proliferation was observed for all plasma treatment conditions. Confluent cell growth was observed with helium plasma treated polycarbonate. Both reduced platelet adhesion and increased partial thromboplastin time (increased to 204 s from 128 s corresponding to untreated polycarbonate) confirm the improved blood compatibility of plasma treated polycarbonate.

Surface modification of poly(dimethylsiloxane) through oxygen and nitrogen plasma treatment to improve its characteristics towards biomedical applications

Polymeric materials successfully applied in biomedical applications have an issue of poor surface properties which may restrict their applications as biomaterials. The present paper aims to study the effect of oxygen and nitrogen plasma treatment on physico-chemical properties of poly(dimethylsiloxane) (PDMS) and enhancement in its biocompatibility. Various characterization techniques including Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy (SEM), atomic force microscopy were used to evaluate the changes in surface chemistry and morphology of plasma treated PDMS. Changes in the wettability after plasma treatments and the effects of ageing on wettability were studied by contact angle measurement. Ageing studies showed that the contact angle was stable after two hours. The effect of plasma treatment on biocompatibility was studied through cell adhesion and MTT using 3T3 fibroblast cells. Morphology of cells obtained through SEM was analyzed using ImageJ software. Among the different treated and untreated samples, substantial enhancement in biocompatibility was observed for nitrogen plasma treated PDMS for 5 min in terms of highest cell area observed from cell adhesion test and highest cell viability observed from MTT test. This may be probably due to its highest polarity (0.4) and surface energy (33.3 N mm?2) with a moderate surface roughness (Rrms?=?100.24 nm) among the other treated and untreated samples.

Production and hemocompatibility assessment of novel electrospun polyurethane nanofibers loaded with dietary virgin coconut oil for vascular graft applications

To develop biodegradable polymer scaffolds suitable for vascular tissue engineering applications, the bioengineering community has invested an extensive effort. The most common cause for the failure of vascular graft scaffolds is thrombosis. In this work, the scaffold based on polyurethane and virgin coconut oil was produced by electrospinning process for vascular tissue engineering applications with improved antithrombogenicity. The diameter of this electrospun polyurethane/virgin coconut oil composite was found to be reduced in the range of 886 ± 207 nm compared to pristine polyurethane which was in the range of 969 ± 217 nm. The Fourier transform infrared spectroscopy analysis revealed the interaction between polyurethane and virgin coconut oil as indicated by phase shifting of CH bond along with the formation of hydrogen bond. The contact angle measurement of fabricated composites was found to be increased owing to hydrophobic nature and also exhibited enhanced thermal stability as noted in thermogravimetric analysis. The atomic force microscopy analysis insinuated the increased surface roughness of the composite in comparison with the pure polyurethane. Developed scaffold resulted in delayed blood clotting as revealed by activated partial thromboplastin time and partial thromboplastin time assay. The hemolytic index of fabricated composites was found to be low indicating the enhanced safety of red blood cells. Hence, the newly developed nanofibrous composite scaffold could open the door for a suitable alternative for vascular graft applications.

Synthesis and characterization of nickel oxide/graphene sheet/graphene ribbon composite

A novel and simple hydrothermal synthesis of nickel oxide (NiO)/graphene sheets (GNS)/graphene ribbon (GR) hybrid material is reported for the first time. The crystalline property and surface morphology of NiO/GNS/GR (NiO/HG) hybrid material is characterized by X-ray diffraction, Raman spectroscopy and Transmission electron spectroscopy. The fast electron transfer of GNS/GR along with NiO contributes an excellent electrochemical performance in the field of non-enzymatic glucose sensor.

Effect of carbon nanotubes on mechanical, electrical and thermal properties of plasma-modified multi-walled carbon nanotubes/polyimide nanocomposites

A nanocomposite of polyimide based surface modified multiwall carbon nanotubes (MWCNTs) has been prepared. The surface modified MWCNTs were synthesized by exposing MWCNTs to radio frequency (RF) plasma discharge of oxygen, nitrogen and ammonia gases. Raman spectra studies evidences the inclusion of defects onto the surface of carbon nanotubes. A homogenous dispersion of plasma modified MWCNTs was achieved in polyimide matrix. Owing to the strong interfacial interaction between the polymer matrix and incorporated plasma modified MWCNTs the mechanical, electrical and thermal property of the polyimide was enhanced. These results indicate that the plasma surface modified MCNTs incorporated into the polyimide matrix acts as an effective reinforcement filler material in the polyimide matrix.