Jahangir Ahmad Rather

Carbon nanotubes based electrochemical aptasensing platform for the detection of hydroxylated polychlorinated biphenyl in human blood serum

A novel strategy to sense target molecules in human blood serum is achieved by immobilizing aptamers (APTs) on multi-walled carbon nanotubes (MWCNT) modified electrodes. In this work, the aminated aptamer selected for hydroxylated polychlorinated biphenyl (OH-PCB) was covalently immobilized on the surface of the MWCNT-COOH modified glassy carbon electrode through amide linkage. The aptamers function as recognition probes for OH-PCB by the binding induced folding of the aptamer. The developed aptasensing device was characterized by electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The aptasensor displayed excellent performance for OH-PCB detection with a linear range from 0.16 to 7.5 μM. The sensitivity of the developed aptasensing platform is improved (1×10(-8) M) compared to the published report (1×10(-6) M) for the determination of OH-PCB (Turner et al., 2007). The better performance of the sensor is due to the unique platform, i.e. the presence of APTs onto electrodes and the combination with nanomaterials. The aptamer density on the electrode surface was estimated by chronocoulometry and was found to be 1.4×10(13) molecules cm(-2). The validity of the method and applicability of the aptasensor was successfully evaluated by the detection of OH-PCB in a blood serum sample. The described approach for aptasensing opens up new perspectives in the field of biomonitoring providing a device with acceptable stability, high sensitivity, good accuracy and precision.

Next generation NIR fluorophores for tumor imaging and fluorescence-guided surgery: A review

Cancer is a group of diseases responsible for the major causes of mortality and morbidity among people of all ages. Even though medical sciences have made enormous growth, complete treatment of this deadly disease is still a challenging task. Last few decades witnessed an impressive growth in the design and development of near infrared (NIR) fluorophores with and without recognition moieties for molecular recognitions, imaging and image guided surgeries. The present article reviews recently reported NIR emitting organic/inorganic fluorophores that targets and accumulates in organelle/organs specifically for molecular imaging of cancerous cells. Near infrared (NIR probe) with or without a tumor-targeting warhead have been considered and discussed for their applications in the field of cancer imaging. In addition, challenges persist in this area are also delineated in this review.

Rapid microwave synthesis of high aspect-ratio ZnO nanotetrapods for swift bisphenol A detection.

Highly crystalline and high aspect-ratio ZnO nanotetrapods were grown by a novel and swift microwave synthesis. FESEM analysis revealed that each tetrapod has four thin arms and are derived from the midst of the crystal. The diameter of each arm is larger at the base and smaller at the tip. Structural analysis revealed that these nanotetrapods are single crystalline and have a wurtzite hexagonal crystal structure. These ZnO nanotetrapods were used for the detection of BPA. The electrochemical sensor based on the ZnO nanotetrapods modified electrode showed electrocatalytic activity in terms of significant improvement of the anodic current of BPA and lowering of the detection limit. Under optimized conditions, the squarewave oxidation peak current of BPA was linear over the concentration range of 12.4 nM to 1.2 μM with the detection limit of 1.7 nM and sensitivity of 5.0 μA nM(-1) cm(-2). This sensor showed high sensitivity and response compared with other electrochemical sensors reported for the detection of BPA.

An electrochemical sensor based on fullerene nanorods for the detection of paraben, an endocrine disruptor

In the present work, fullerene nanorods (C60NRs) were synthesized by liquid–liquid interface and characterized using Fourier transform infrared (FTIR) spectroscopy, field emission electron microscopy (FESEM) and X-ray diffraction (XRD) techniques. The C60NRs were covalently immobilized on the surface of a glassy carbon electrode (GCE) using surface bound diazonium salts as an interface. This method involves electrografting of the p-nitrophenyl diazonium salt at the GCE to give the nitrophenyl-modified electrode (GCE–Ph–NO2). The nitrophenyl groups of the GCE–Ph–NO2 modified electrode were reduced to phenylamine groups (GCE–Ph–NH2) using an aqueous solution of the sodium borohydride/gold–polyaniline (NaBH4/Au–PANI) system. The C60NRs were covalently immobilized on the surface of GCE–Ph–NH2via an N–H addition reaction across the π-bond of C60. The functionalized fullerene nanorod (C60NRs–NH–Ph–GCE) modified electrode was electrochemically reduced in 1.0 M potassium hydroxide (KOH) to produce a highly conductive electrochemically reduced fullerene nanorod (ERC60NRs–NH–Ph–GCE) sensor. The developed sensor shows high electrocatalytic activity for the detection of ethylparaben (EP) over a concentration range from 0.01–0.52 μM with a detection limit (LOD) of 3.8 nM (0.0038 μM). In addition, the ERC60NRs–NH–Ph–GCE sensor was also tested for EP in real sample analysis using the standard addition method where the total concentration of EP was found to be 0.011 μM (0.12%) within the permissible limit of 0.19%.

Graphene-amplified femtosensitive aptasensing of estradiol, an endocrine disruptor

We report the construction of a novel electrochemical femtomolar aptasensing APT-ERGO/GCE interface based on the covalent immobilization of 38-mer amine-functionalized (NH2-APT) 17β-estradiol (E2) DNA aptamers on a graphene amplifying platform. Graphene oxide (GO) was synthesized and characterized by using FTIR, UV-vis spectroscopy, XRD spectroscopy, and SEM technique. The strategy for the construction of the E2-aptasensing interface involves in a three-step modification process. (i) First, we carried out the electrochemical reduction of GO on the GCE electrode to form ERGO/GCE. (ii) Then, as an impact strategy, the E2-aptamers (NH2-APT) were further immobilized on the surface of the ERGO/GCE interface through electrochemical reduction of surface-functionalized diazonium salts. This step includes electrografting of ERGO/GCE by electrochemical reduction of the diazonium salt (ClN2+-Ph-COOH) to obtain the ERGO/GCE-Ph-COOH-modified electrode. (iii) Finally, the free carboxyl groups on the ERGO/GCE-Ph-COOH surface were conjugated with NH2-APT through formation of carbodiimide to afford an aptasensing APT-ERGO/GCE interface. The presence of ERGO as an amplifying platform led to the successful immobilization of E2-aptamers with a surface coverage of 1.9 × 1013 molecule per cm2, which is higher than the values obtained in other reported methods. The constructed aptasensing APT-ERGO/GCE interface was appraised using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The synergetic effect of high affinity and specificity of E2-aptamers and graphene platform was beneficial for the novel femtosensitive label-free electrochemical aptasensing APT-ERGO/GCE interface for the detection of [E2]. The oxidation current peaks at the aptasensing APT-ERGO/GCE interface were proportional to [E2] over two different concentration linearity ranges 1.0 × 10-15 mol L-1-9.0 × 10-12 mol L-1-1.2 × 10-11 mol L-1 to 2.3 × 10-10 mol L-1 with a limit of detection (LOD) of 0.5 × 10-15 mol L-1. This aptasensing APT-ERGO/GCE interface was employed as a femtomolar tool for the determination of [E2] in the environmental and pharmaceutical samples such as wastewater (spiked) and pharmaceutical dosages.

Recent Progress on Rubber Based Biocomposites: From Carbon Nanotubes to Ionic Liquids

Currently, reinforcement of a polymer matrix via the integration of fillers is a common industrial exercise which improves the properties of the composite material. Rubber nanocomposites (NCs) demonstrated remarkable properties due to the interaction between the polymer and filler and the homogeneous dispersion of the filler within the polymer matrix. These improved properties included increased stiffness, high strength, reduced elongation to failure, improved resistance to crack growth and tearing and finally various modifications of abrasion, dynamic and fatigue properties, due to their high surface area and significant aspect ratios. Different reinforcing fillers have been incorporated in the rubber to develop elastomeric composites having improved properties. This current chapter focus on development, properties and applications of various elastomeric composites. Secondly, this chapter also emphasis on ionic liquids (ILs) role as additives in elastomer composites as well as effects of nanofillers on elastomer composites.

Graphene-Fabricated Electrodes for Improving the Performance of Microbial Bioelectrochemical Systems

Abstract Graphene (GR), as an outstanding material, has shown powerful applications in microbial fuel cells (MFCs) promoting the concept of bioenergy production. Featuring unique physical and chemical characteristics, GR exhibits great possibilities for designing its novel hybrids. GR as an anode material accelerates extracellular electron transfer (EET) between microbes and electrode surface and as potent cathodic catalyst facilitates oxygen reduction reaction (ORR) kinetics. A bulk of dimension-tailored GR nanocomposites with conducting polymers, metal nanoparticles, metal oxides, ionic liquids, and doped heteroatoms have been designed as novel electrodes leading to enhanced performance of MFCs. GR-based bioactive architectures hold great promise for their effective applications in bioelectrochemical systems. The present chapter deals with different nanohybrids of GR as anodes and cathodes improving the overall efficiency of MFCs. Future perspectives addressing some key challenges pertaining to implication of GR materials in MFCs have been concluded at the end.

Bioplastics and Bionanocomposites Based on Nanoclays and Other Nanofillers

This chapter provides an overall review on the latest progress in the research and development of bionanocomposites that are utilized in various applications such as packaging, durable goods, electronics and biomedical applications. The rise of biobased materials is guided by its renewability, low carbon footprint and biodegradability issues and by virtue of which vast applications of these materials are already available. The bionanocomposites provides a better alternative for the various drawbacks which can be found in the biobased polymer matrix materials. Some of the issues of low strength, poor barrier properties, hydrophilicity, low thermal stability and conductivity can be addressed by the development of bionanocomposites. The chapter will begin with the introduction and recent advances in the development of biobased materials from renewable resources and their usefulness. In the very next part, many types of bionanocomposites based on these fillers i.e. nanocellulose, carbon nanotubes and nanoclays, are discussed. This review also presents up-to-date progress in this area in terms of processing technologies, product development and applications.

Modification of Nanoclay Systems: An Approach to Explore Various Applications

Nanoclay has a great potential in various fields. Small amount of nanoclay can change the whole physical and chemical properties of polymers, paints, inks and lubricants by dispersing nanoclay layers into the polymer matrices. The flexibility of interlayer gallery of nanoclay helps in the release of drugs to the targeted place. The controlled release of drugs takes place on account of the drug incorporated within the nanoclay galleries. This makes these nanomaterials as potential materials with its application in pharmaceutical field. Organoclays, a type of nanoclay are also being utilized for waste water treatment in junction with other sorbents viz. activated carbon and alum. Organoclays have been found to be the finest material for water treatment especially when the water contains enough amounts of oil and grease or humic acid. The use of nanoclays as reinforcing agent or additives in polymers for various properties is exploited for various applications. This chapter provides an overview of nanoclays or types of nanoclays with significance on the utilization of nanoclays as the filler in polymer matrices for the synthesis/fabrication of polymer nanocomposites, drug delivery agents, viscosity modifier for coatings, inks and lubricants and nanoclays for industrial effluent as well as potable water treatment.