Bioconjugation of InGaP quantum dots for molecular sensing.

Fluorescence-based molecular sensing and cellular imaging are commonly carried out with the application of organic dyes. Quantum dots (QDs) are now recognized as better tools because they are brighter, size tunable, and more photostable than dyes. Most of the proposed QD-based biosensing systems involve elements of known toxicity. The present work reports the functionalization of biocompatible InGaP/ZnS core-shell QDs with anti-bovine serum albumin (anti-BSA) to exploit them as fluorescent probes for antigen detection. Successful bioconjugation was characterized with the absorption and emission spectra showing blue shifts of around 40 and 30 nm, respectively. Gel electrophoresis and particle size distribution studies further confirmed the mass increment of QDs after their functionalization with anti-BSA. Surface plasmon resonance spectrometry has been used to study the affinity of QD-(anti-BSA) probes for bovine serum albumin (BSA). Photoluminescence quenching of the developed probe is observed in the presence of BSA.

Recovery of pure ZnO nanoparticles from spent Zn-MnO2 alkaline batteries.

The recovery of pure ZnO (zinc oxide) nanoparticles from spent Zn-Mn dry alkaline batteries is reported. Spent batteries were dismantled to separate the contained valuable metals of the cell electrodes in the form of black powder. Treatment of this black powder with 5 mol L(-1) HCl produced leach liquor, primarily containing 2.90 g L(-1) Zn and 2.02 g L(-1) Mn. Selective and quantitative liquid-liquid extraction of Zn(II) was then carried out in three counter current steps by using Cyanex 923 (0.10 mol L(-1) in n-hexane). Zn(II) distributed in the organic phase as complex ZnCl(2)·2R (R = Cyanex 923 molecule). The metal loaded organic phase was subjected to combust at 600 °C to yield pure ZnO nanoparticles (40-50 nm). Important characteristics of the synthesized nanoparticles were investigated by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and atomic force microscopy (AFM).

Metal Organic Framework steered electrosynthesis of anisotropic gold nanorods for specific sensing of organophosphate pesticides in vegetables collected from the field.

The uncontrolled use of organophosphate (OP) group of pesticides has led to their accumulation in food and vegetables, causing major health issues. Hence, the development of a reliable sensor is imperative for the detection of neurotoxic organophosphates (OP). In the present study, we have intertwined the interfaces of a Metal Organic Framework (MOF), MOF-directed rapid electrochemically grown gold nanorods (aAuNR), cysteamine (Cys) functionalization, and the neurotransmitter acetylcholinesterase (AChE) to fabricate a novel electrochemical bioprobe AChE/Cys/aAuNR/MOF/ITO for sensing OP pesticides with an ultra-low detection limit of 3 ng L-1 over a linear range of 30 to 600 ng L-1. Prior to sensing, in silico docking studies were employed for tracking the structural aspects of the molecular recognition of specific OP as potential inhibitors. The sensor can quantify residues of sprayed OP (chlorpyrifos, malathion, parathion, methyl parathion, ethion) in field vegetables (Abelmoschus esculentus, Solanum melongena, Capsicum annuum, Momordica charantia Linn) using a single calibration curve designed using chlorpyrifos, and the results were validated via gas chromatography-electron capture detector (GC-ECD) measurements. The inhibition rate kinetics of structurally different OP (chlorpyrifos, malathion, methyl parathion) were studied via the bioprobe and further validated using the standard Ellman method, confirming the practical applicability of the sensor for the detection of a specific group of OP. The bioprobe AChE/Cys/aAuNR/MOF/ITO offers good stability, specificity, and anti-interference properties for the detection of OP in real samples.

Electro-deposited nano-webbed structures based on polyaniline/multi walled carbon nanotubes for enzymatic detection of organophosphates.

We report the development of an ultrasensitive electrochemical sensor using polyaniline (PANi) and carboxyl functionalized multi-walled carbon nanotubes (fMWCNT) for the detection of organophosphates (OPs) in real samples. The sensor was tested in the linear concentration range of 10 ng/L to 120 ng/L. The limit of detection (LoD) was found to be 8.8 ng/L with sensitivity 0.41 mA/ng/L/cm2 for chlorpyrifos (CPF); and 10.2 ng/L with sensitivity 0.58 mA/ng/L/cm2 for methyl parathion (MP). The vegetable samples (cucumber) were also tested. The average % recovery for CPF and MP were found to be 98.05% and 96.63% respectively. The developed sensor showed stability for a period of 30 days. The interference of the sensor was studied with heavy metals (cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As)) which was found to be < 10%. The developed sensor will play a major role in real-time monitoring of food products, leading to food safety.

Microfluidic Affinity Sensor Based on a Molecularly Imprinted Polymer for Ultrasensitive Detection of Chlorpyrifos.

The persistent use of pesticides in the agriculture field remains a serious issue related to public health. In the present work, molecularly imprinted polymer thin films were developed using electropolymerization of pyrrole (py) onto gold microelectrodes followed by electrodeposition for the selective detection of chlorpyrifos (CPF). The molecularly imprinted polymer (MIP) was synthesized by the electrochemical deposition method, which allowed in-line transfer of MIP on gold microelectrodes without using any additional adhering agents. Various parameters such as pH, monomer ratio, scan rate, and deposition cycle were optimized for sensor fabrication. The sensor was characterized at every stage of fabrication using various spectroscopic, microscopic, and electrochemical techniques. The sensor requires only 2 µL of the analyte and its linear detection range was found to be 1 µM to 1 fM. The developed sensor's limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.93 and 2.82 fM, respectively, with a sensitivity of 3.98 (µA/(µM)/ mm2. The sensor's shelf life was tested for 70 days. The applicability of the sensor in detecting CPF in fruit and vegetable samples was also assessed out with recovery % between 91 and 97% (RSD < 5%). The developed sensor possesses a huge commercial potential for on-field monitoring of pesticides.

Electrochemical micro analytical device interfaced with portable potentiostat for rapid detection of chlorpyrifos using acetylcholinesterase conjugated metal organic framework using Internet of things.

An Electrochemical micro Analytical Device (EµAD) was fabricated for sensitive detection of organophosphate pesticide chlorpyrifos in the food chain. Gold microelectrode (µE) modified with Zinc based Metal Organic Framework (MOF-Basolite Z1200) and Acetylcholinesterase (AChE) enzyme served as an excellent electro-analytical transducer for the detection of chlorpyrifos. Electrochemical techniques such as Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV) were performed for electrochemical analysis of the developed EµAD. The sensor needs only 2 µL of the analyte and it was tested within the linear range of 10 to 100 ng/L. The developed EµAD's limit of detection (LoD) and sensitivity is 6 ng/L and 0.598 µ A/ng L-1/mm2 respectively. The applicability of the device for the detection of chlorpyrifos from the real vegetable sample was also tested within the range specified. The fabricated sensor showed good stability with a shelf-life of 20 days. The EµAD's response time is of 50 s, including an incubation time of 20 s. The developed EµAD was also integrated with commercially available low-cost, handheld potentiostat (k-Stat) using Bluetooth and the results were comparable with a standard electrochemical workstation.

Covalent attachment of actin filaments to Tween 80 coated polystyrene beads for cargo transportation.

In this manuscript, a new strategy has been reported for circumscribed covalent attachment of barbed and pointed ends of actin filaments to polystyrene beads. A comparative study of attachment of actin filaments to polystyrene beads was performed by blocking functionally active sites on polystyrene beads with nonionic detergents such as Tween 20, Tween 80 and polyethylene glycol (PEG). Effective blocking of active sites was obtained with Tween 80 at 0.1% concentration. Attachment of single bundle of actin filament to bead was assessed by rotational motion of bead tailed actin in front and lateral view. Velocity of actin filaments attached to different size of beads in in-vitro motility assay was calculated to ascertain their attachments. Velocity of actin attached to 1.0 and 3.0 microm polystyrene beads was reduced to 3.0-4.0 and 0.0-1.0 microm/s, respectively as compared to free actin velocity of 4.0-6.0 microm/s. Single point attachment of actin filaments to different size of beads was assessed by decrease in sliding velocity. Present study provides insight into the actin-myosin based molecular motor systems for drug delivery and biosensors applications.

DNA immobilization chemical interference due to aggregates study by Dip and Drop approach.

In the present manuscript, we report the studies and observations for chemical interference due to aggregates formation during covalent immobilization of thiolated lambda-DNA between gold microelectrodes. Dip and Drop approaches were employed to study DNA immobilization using thiolated oligos (oligoA 5' GGGCGGCGACCT 3' and oligoB 5' AGGTCGCCGCCC 3'). As a result of aggregation, less interference was observed in Dip approach as compared to Drop approach. Atomic Force Microscopy (AFM) analysis of piranha treated gold surface revealed 47.5% increase in height roughness, contributing in interference by creating active sites. Cyclic voltammetry (CV) studies ascertain the multitude of adsorption states existing in long strand of DNA on surface. Surface coverage was found to be approximately 72% (1.35x10(10) molecules/cm(2)), and approximately 42% (7.89x10(9) molecules/ cm(2)) in Dip and Drop approach, respectively. Dip approach can be used as a measure to minimize interference due to aggregation.

Translocation and toxicity of docetaxel multi-walled carbon nanotube conjugates in mammalian breast cancer cells.

Multi-walled-carbon nanotubes (MWNTs) are widely explored as carriers for drug delivery due to their facile transport through cellular membranes and are reportedly found to be effective against cancer. In the present study, we have evaluated cellular uptake of Docetaxel (DTX) conjugated MWNTs from human breast cancer cells (MCF-7 and MDA-mb-231) and have provided primary results on cytotoxicity of the same. Efficient internalization of the drug conjugate (DTX-MWNTs) inside the cell was corroborated with the help of confocal microscopy, transmission electron microscopy and flow cytometry. The comparison of cytotoxicity of the conjugate and DTX was done by MTT assay. Results of the study indicated increased efficacy of the conjugates over the drug in terms of their cytotoxicity. It was observed that such conjugation of drug to MWNTs can be explored as a strategy to improve therapeutic index of cytotoxic drugs such as DTX and thereby enriching cancer therapies of coming time.

Controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes.

A facile method for controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes is demonstrated. Nitric acid based oxidation was carried out to create carboxylic groups exclusively at the ends of carbon nanotubes, whereas oxidation using a mixture of nitric and sulfuric acid with varied reaction time was carried out to control the population of carboxylic groups on the side walls of nanotubes. In turn, 4-aminothiophenol modified gold nanoparticles were covalently interfaced to these carboxylated multi-walled carbon nanotubes in the presence of a zero length cross-linker, 1-ethylene-3-(3-dimethylaminopropyl) carbodiimide. Raman spectroscopic results showed increase in height of disorder band with each of these successive steps, indicating the increase in degree of functionalization of the carbon nanotubes. Fourier transformed infrared spectroscopic analysis affirmed the functionalization of nanostructures and the formation of nanohybrid. Transmission electron and field emission scanning electron microscopic analysis ascertained the attachment of gold nanoparticles to the ends and side walls of the multi-walled carbon nanotubes. The new hybrid nanostructures may find applications in electronic, optoelectronic, and sensing devices.

Immobilization of enzyme on long period grating fibers for sensitive glucose detection.

Glucose oxidase (GOD) immobilized long period grating (LPG) fibers have been proposed for the specific and sensitive detection of glucose. The treatment of LPG fibers with aminopropyl triethoxysilane has induced biding sites for the subsequent GOD immobilization. Field emission scanning electron microscopy, confocal laser scanning microscopy, infrared spectroscopy and Raman spectroscopy have provided detailed evidences about the effectiveness of the adopted biofunctionalization methodology. The enzyme activity is conserved during the immobilization step. Fabricated LPG sensor was tested on different glucose solutions to record the transmission spectra on an optical spectrum analyzer. The wavelength shifts in the transmission spectra are linearly correlated with the glucose concentration in the range of 10-300 mg dL(-1). The fabricated sensor gives fast response and is demonstrated to be of practical utility by determining glucose contents in blood samples. Proposed technique can further be extended to develop LPG fiber based novel, sensitive and label free nanosensors for disease diagnosis and clinical analysis.

Divalent cation induced actin ring formation.

In this paper we explored the effect of copper sulphate on the morphology of actin filaments. Actin filaments attain different shapes and structure when exposed to 2mM concentration of copper sulphate. Lateral branches were observed after 4 h of incubation while shapes like Y- and V- were formed after 8h of incubation. Rings and loops of actin filaments were formed when the concentration of copper sulphate was increased from 2 to 5 mM. Additionally, ring formation was also observed when bead tailed actin filaments were incubated with copper sulphate (5 mM). Electrostatic adhesion energy between ends of actin filaments attracted due to counterion was estimated to be 7.34 kT/µm. Divalent cation induced actin ring formation are similar to toroids of DNA but actin filaments have great bending stiffness due to large diameter of the ring formed. From these results we proposed that polyelectrolyte nature of actin filaments leads to the change in their morphology on exposure to high concentration divalent cations.

Low-intensity magnetic fields assisted alignment of actin filaments.

This article represents the effects on actin filaments attached to magnetic nanoparticles when exposed to low-intensity magnetic field. In this approach, streptavidin functionalized magnetic nanoparticles were used to demonstrate the alignment of actin filament under external magnetic field of 22mT. To check the directionality of myosin on magnetically aligned actin filaments in vitro motility assay was performed with myosin and average velocity was found to be 3.50microm/s. It was observed that myosin moves in the direction in which actin filaments were magnetically aligned. This approach will explore the capability of integrating molecular motor into microelectronics mechanical system (MEMS) and nanoelectro-mechanical system (NEMS).

Transportation of drug-(polystyrene bead) conjugate by actomyosin motor system.

The Nanorobotics and cargo transportation application of molecular motors is of recent intent. The present study explores the transportation of Mesalamine/5-aminosalicylic acid/5-ASA drug by molecular motors. Mesalamine is an anti-inflammatory drug used to treat Crohn's disease and ulcerative colitis. Conjugate of mesalamine and polystyrene (Dia.: 3 microm) beads was prepared by amide linkage between amine (-NH2) group of drug and carboxyl (-COOH) group of the bead. In Fourier Transform Infrared spectra, peaks were observed at 3428.1 and 1654.0 cm(-1) for N-H and C=O stretching bond respectively confirming the amide bond formation between drug and microbeads. Quantification of 5-ASA attached to polystyrene bead was done by UV-vis spectroscopy and it was ascertained that 93% of 5-ASA was loaded on polystyrene beads. Conjugate of drug-polystyrene beads were then covalently attached to actin filaments. Velocity of actin filaments attached to drug loaded beads in in-vitro motility assay reduced to 0.89 microm/s as compared to free actin velocity (4.64 microm/s). This further ascertains the microcomposites formation. The present study provides an insight into the actin-myosin based molecular motor systems for an efficient tool for drug transportation.

Comparative study of carbon nanotube dispersion using surfactants.

Dispersion of carbon nanotubes (CNTs) is a challenging task for their utilization in nanoscale device applications. This account reports a comparative analysis on dispersion of multiwalled carbon nanotubes (MWNTs) with four surfactants-Triton X-100, Tween 20, Tween 80, and sodium dodecyl sulfate (SDS). Among the four surfactants, Triton X-100 and SDS provide maximum and minimum dispersion, respectively. Dispersion of MWNTs has been characterized with UV-vis spectroscopy and transmission electron microscopy (TEM). TEM results are in agreement with the UV-vis measurements. The experimentally observed trend of dispersing power of surfactants is consistent with their chemical structures. An optimum CNT-to-surfactant ratio has been determined for each surfactant. This parameter is shown to affect the nanotube dispersion significantly. Surfactant concentration above or below this ratio is shown to deteriorate the quality of nanotube dispersion. TEM analysis of a high-surfactant-concentration sample enables us to construct a plausible mechanism for decrease in CNT dispersion at high surfactant concentration, consistent with the UV-vis observations. Temperature stability of the surfactant is another important factor affecting the quality of CNT dispersion.

1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide interference with Lowry method.

1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) was tested for interference with the Lowry method of protein determination. The EDC interference was nearly additive at both 660 and 750 nm. Blue-colored complex developed in the case of EDC and showed maximum absorbance at 750 nm, similar to the bovine serum albumin (BSA) estimation. In time response analysis, blue-colored complex was developed after 30 min of incubation in both cases (EDC and BSA); therefore, it followed the same kinetic pattern of color development as that of BSA. Interference is believed to be caused by the reduction of the folin-ciocalteu reagent by EDC, resulting in increased blue-colored complex and apparently causing increased protein content of the sample.