Chaitali Singhal

Point of care with micro fluidic paper based device integrated with nano zeolite–graphene oxide nanoflakes for electrochemical sensing of ketamine

The present study was aimed to develop an ultrasensitive technique for electroanalysis of ketamine; a date rape drug. It involved the fabrication of nano-hybrid based electrochemical micro fluidic paper-based analytical device (EμPADs) for electrochemical sensing of ketamine. A paper chip was developed using zeolites nanoflakes and graphene-oxide nanocrystals (Zeo-GO). EμPAD offers many advantages such as facile approach, economical and potential for commercialization. Nanocrystal modified EμPAD showed wide linear range 0.001-5nM/mL and a very low detection limit of 0.001nM/mL. The developed sensor was tested in real time samples like alcoholic and non-alcoholic drinks and found good correlation (99%). The hyphenation of EμPAD integrated with nanocrystalline Zeo-GO for detection of ketamine has immense prospective for field-testing platforms. An extensive development could be made for industrial translation of this fabricated device.

An enzyme free Vitamin C augmented sensing with different ZnO morphologies on SnO2/F transparent glass electrode: A comparative study

Three types of Zinc oxide (ZnO) nanostructures viz. ZnO nanocrystals (ZnONCs), ZnO nanoparticles (ZnONPs) and ZnO nanobelts (ZnONBs) were synthesized and characterized by UV-Vis, FTIR and SEM. A comparison of signal amplification by these ZnO nanostructures as judged by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) revealed that ZnONCs are better sensing interface for electrochemical detection. When these ZnO nanostructure were compared electrochemically for sensing Vitamin C, ZnONCs sensor outperformed the ZnONP and ZnONB sensor and previously reported sensors. The ZnONCs/MB/FTO electrode showed a wide linear sensing range (0.001μM to 4000μM), low detection limit (0.0001μM), a small response time (5s) and a storage stability of 6months. To the best of our knowledge, this elevated sensitivity and remarkable stability for electrochemical Vitamin C detection using ZnONCs have not been reported so far.

Hierarchical electrodeposition of methylene blue on ZnO nanocrystals thin films layered on SnO2/F electrode for in vitro sensing of anti-thalassemic drug

Zinc oxide nanocrystals-methylene blue nanocomposites were developed by electrodeposition of methylene blue onto the thin films of zinc oxide nanocrystals deposited onto SnO2/F coated glass substrates for in vitro sensing of anti-thalassemic drug i.e. deferiprone. Detailed morphological, electrochemical, structural and optical characterizations of ZnONC-MB/FTO electrode were done using XRD, SEM, EIS, FTIR, LSV, and CV and show quick response time (within 5 s), linearity as 1 × 10(-3) to 10(3) μM and shelf life of about 10 weeks under refrigerated conditions. Attempts have been made to utilize this electrode for estimation of deferiprone in urine samples. The developed sensor exhibited high reproducibility and good storage stability.

Impedimetric genosensor for detection of hepatitis C virus (HCV1) DNA using viral probe on methylene blue doped silica nanoparticles

An impedimetric genosensor was fabricated for detection of hepatitis C virus (HCV) genotype 1 in serum, based on hybridization of the probe with complementary target cDNA from sample. To achieve it, probe DNA complementary to HCVgene was immobilized on the surface of methylene blue (MB) doped silica nanoparticles MB@SiNPs) modified fluorine doped tin oxide (FTO) electrode. The synthesized MB@SiNPs was characterized using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) pattern. This modified electrode (ssDNA/MB@SiNPs/FTO) served both as a signal amplification platform (due to silica nanoparticles (SiNPs) as well as an electrochemical indicator (due to methylene blue (MB)) for the detection of the HCV DNA in patient serum sample. The genosensor was optimized and evaluated. The sensor showed a dynamic linear range 100-106 copies/mL, with a detection limit of 90 copies/mL. The sensor was applied for detection of HCV in sera of hepatitis patient and could be renewed. The half life of the sensor was 4 weeks. The MB@SiNPs/FTO electrode could be used for preparation of other gensensors also.

Detection of alprazolam with a lab on paper economical device integrated with urchin like Ag@ Pd shell nano-hybrids

We present results of the studies relating to fabrication of a microfluidic biosensor chip based on urchin like Ag@ Pd shell nano-hybrids that is capable of sensing alprazolam through electrochemical detection. Using this chip we demonstrate, with high reliability and in a time efficient manner, the detection of alprazolam present in buffer solutions at clinically relevant concentrations. Methylene blue (MB) was also doped as redox transition substance for sensing alprazolam. Nano-hybrids modified EμPAD showed wide linear range 1-300ng/ml and low detection limit of 0.025ng/l. Low detection limit can further enhance its suitability for forensic application. Nano-hybrids modified EμPAD was also employed for determination of drug in real samples such as human urine. Reported facile lab paper approach integrated with urchin like Ag@ Pd shell nano-hybrids could be well applied for the determination of serum metabolites.

Portable bioactive paper based genosensor incorporated with Zn-Ag nanoblooms for herpes detection at the point-of-care

The present work describes the fabrication of an electrochemical paper-based analytical device (EPAD) integrated with Zn-Ag nanoblooms for detection of herpes in human, caused by Herpes virus 5(HHV-5) DNA, at the point of care. The cyclic voltammetry(CV) was used for electrochemical detection of the HHV-5 DNA in infected patient samples. The EPAD exihibited optimum current response within 5s at pH7.0 and 35°C with two dynamic linear/working ranges, 113-103 and 3×105-106copies/mL and detection limit of 97copies/mL. The device showed high selectivity, repeatability, and sensitivity. The device had many advantageous features such as portable, facile approach, economical and potential for commercialization. The proposed sensing scheme is highly feasible for future clinical detection of Herpes virus.

Comparative analysis of single-walled and multi-walled carbon nanotubes for electrochemical sensing of glucose on gold printed circuit boards

In the present work, a comparative study was performed between single-walled carbon nanotubes and multi-walled carbon nanotubes coated gold printed circuit board electrodes for glucose detection. Various characterization techniques were demonstrated in order to compare the modified electrodes viz. cyclic voltammetry, electrochemical impedance spectroscopy and chrono-amperometry. Results revealed that single-walled carbon nanotubes outperformed multi-walled carbon nanotubes and proved to be a better sensing interface for glucose detection. The single-walled carbon nanotubes coated gold printed circuit board electrodes showed a wide linear sensing range (1 mM to 100 mM) with detection limit of 0.1 mM with response time of 5 s while multi-walled carbon nanotubes coated printed circuit board gold electrodes showed linear sensing range (1 mM to 100 mM) with detection limit of 0.1 mM with response time of 5 s. This work provided low cost sensors with enhanced sensitivity, fast response time and reliable results for glucose detection which increased the affordability of such tests in remote areas. In addition, the comparative results confirmed that single-walled carbon nanotubes modified electrodes can be exploited for better amplification signal as compared to multi-walled carbon nanotubes.

Prussian blue nanocubes/carbon nanospheres heterostructure composite for biosensing of metformin

This paper reports the fabrication of highly sensitive metformin sensor based on Prussian blue (PB) nanocubes/carbon nanosphere (CNS) heterostructures composed of a perfect cube and spherical composite on a fluorine-doped tin oxide surface. Due to the excellent biocompatibility of PB nanocubes the PB/CNS based Mf sensor exhibited a wide linear range of 0.001–10 mM with a response duration of less than 5 s and a detection limit (based on signal to noise ratio) of 0.1 µM.

Hydrothermally synthesized zinc oxide nanorods incorporated on lab-on-paper device for electrochemical detection of recreational drug

Abstract This paper reports an electrochemical paper analytical device (EPAD) for detection of recreational drug; methylenedioxymethamphetamine (MDMA). MDMA is used as an addictive narcotic by youth and there is an urgent need to detect this drug as it is a potential neurotoxic agent. The proposed EPAD represents many advantageous features of being simple, low-cost, consistent and disposable. The working electrode of the EPAD features zinc oxide nanorods (ZnONRs). The morphological, optical, elemental composition and phase analysis of the synthesized ZnONRs has been characterized by field emission scanning electron microscopy (FESEM), UV–Vis spectroscopy, energy dispersive X-ray spectroscopy (EDAX), photo-luminescence (PL) and X-ray diffraction (XRD). The developed sensor showed optimum response at 7.0 pH and wide linear range of 1 µM–1 mM with a low detection limit of 0.1 µM for MDMA. Evaluation of the sensor also revealed best results in terms of analytical recovery (95%) and accuracy (95%). The designed EPAD could prove to be very effective in case of forensic diagnostic applications. This work provides a reliable diagnostic method for remote areas with limited resources, and will also help people who cannot afford expensive medical tests and have limited access to power and trained personnel.