Highly sensitive detection of dipicolinic acid with a water-dispersible terbium-metal organic framework

Bhardwaj, Neha,Bhardwaj, Sanjeev,Mehta, Jyotsana,Kim, Ki-Hyun,Deep, Akash Elsevier 2016 Biosensors & bioelectronics Vol.86 No.-

<P><B>Abstract</B></P> <P>The sensitive detection of dipicolinic acid (DPA) is strongly associated with the sensing of bacterial organisms in food and many types of environmental samples. To date, the demand for a sensitive detection method for bacterial toxicity has increased remarkably. Herein, we investigated the DPA detection potential of a water-dispersible terbium-metal organic framework (Tb-MOF) based on the fluorescence quenching mechanism. The Tb-MOF showed a highly sensitive ability to detect DPA at a limit of detection of 0.04nM (linear range of detection: 1nM to 5µM) and also offered enhanced selectivity from other commonly associated organic molecules. The present study provides a basis for the application of Tb-MOF for direct, convenient, highly sensitive, and specific detection of DPA in the actual samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dipicolinic acid (DPA) is an excellent indicator of bacterial infection. </LI> <LI> In this work, metal organic frameworks (MOFs) are explored as potential DPA detectors. </LI> <LI> Fluorescent detection of DPA is achieved by synthesizing the Tb-MOF ‘Tb(BTC)(H<SUB>2</SUB>O)<SUB>6</SUB>’. </LI> </UL> </P>

Fluorescent nanobiosensors for the targeted detection of foodborne bacteria

Bhardwaj, Neha,Bhardwaj, Sanjeev K.,Nayak, Manoj K.,Mehta, Jyotsana,Kim, Ki-Hyun,Deep, Akash Elsevier 2017 Trends in analytical chemistry Vol.97 No.-

<P>Foodborne diseases caused by bacterial pathogens are severe threats to human health. Conventional culture based microbiologic methods for the analysis of bacterial contamination in food products are laborious, time consuming and require specific skills. Immunologic and polymerase chain reaction (PCR) based molecular methods are also costly, lack specificity, and may yield false results. As outlined in this review, fluorescent nanobiosensors have now become effective alternative tools for rapid and routine detection of foodborne bacteria. We provide an overview of the use of different fluorescent nano materials in the development of nanobiosensors with special emphasis on underlying detection principles, sensitivity, specificity, and their capability of multiplexed analysis. In summary, the diverse nanomaterials used for bacterial detection are critically analyzed with respect to their advantages and limitations for future applications in the diagnosis of foodborne bacteria. (C) 2017 Elsevier B.V. All rights reserved.</P>

An overview of different strategies to introduce conductivity in metal-organic frameworks and miscellaneous applications thereof

Bhardwaj, Sanjeev K.,Bhardwaj, Neha,Kaur, Rajnish,Mehta, Jyotsana,Sharma, Amit L.,Kim, Ki-Hyun,Deep, Akash The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.31

<P>Metal-organic frameworks (MOFs) are known to possess many interesting material properties such as high specific surface area, tailorable porosity, adsorption/absorption capabilities, post-synthetic modifications, and chemical/thermal stabilities. Because of these unique features, they have been explored for the development of sensors for a variety of analytes. A large proportion of pre-existing MOF-based sensors are well suited for optical transductions due to a lack of electrical conduction in their pristine forms. Hence, the development of MOF-based electrochemical/electrical sensors requires specialized strategies through which MOFs are modified or hybridized with enhanced conductive moieties (<I>e.g.</I>, <I>via</I> doping or post synthetic modification). In this review article, we provide a comprehensive review of various synthetic and integrating strategies to improve electrical conductivity and long-range charge transport properties in MOFs. To this end, we have compiled details of different techniques that have been used to develop electrically/electrochemically active platforms for MOF-based sensing of various targets.</P>

MOF–Bacteriophage Biosensor for Highly Sensitive and Specific Detection of <i>Staphylococcus aureus</i>

Bhardwaj, Neha,Bhardwaj, Sanjeev K.,Mehta, Jyotsana,Kim, Ki-Hyun,Deep, Akash American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.39

<P>To produce a sensitive and specific biosensor for Staphylococcus aureus, bacteriophages have been interfaced with a water-dispersible and environmentally stable metal-organic framework (MOF), NH2-MIL-53(Fe). The conjugation of the MOF with bacteriophages has been achieved through the use of glutaraldehyde as cross-linker. Highly sensitive detection of S. aureus in both synthetic and real samples was realized by the proposed MOF-bacteriophage' biosensor based on the photoluminescence quenching phenomena; limit of detection (31 CFU/mL) and range of detection (40 to 4 X 10(8) CFU/mL). This is the first report exploiting the use of an MOF-bacteriophage complex for the biosensing of S. aureus. The results of our study highlight that-the proposed biosensor is more sensitive than most of the previous methods while exhibiting some advanced features like specificity) regenerability, extended range of linear 'detection, and stability for long-term storage (even at room temperature).</P>

Selective hydrolysis of amorphous cellulosic fines for improvement in drainage of recycled pulp based on ratios of cellulase components

Nishi K. Bhardwaj,Nishi K. Bhardwaj,Surendra P. Singh 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.22 No.-

Recycled pulp contains large amount of fines having high surface area and amorphous cellulose. Thesefines adsorb water to large extent and dewatering rate is lower compared to virgin pulp. Selectivehydrolysis of these excess ultra fines through cellulase enzymes can be utilized for enhancing thedrainage rate. The concept of monocomponent cellulase treatment of recycled pulp for improvement indrainage and the understanding whether effectiveness depends on a specific type of cellulasecomponent (endoglucanase/cellobiohydrolase) is described. The improvement of 15–23% in pulpdrainability was achieved along with better paper properties.

Role of low energy transition metal ions in interface formation in ZnO thin films and their effect on magnetic properties for spintronic applications

Bhardwaj, Richa,Kaur, Baljeet,Singh, Jitendra Pal,Kumar, Manish,Lee, H.H.,Kumar, Parmod,Meena, R.C.,Asokan, K.,Hwa Chae, Keun,Goyal, Navdeep,Gautam, Sanjeev Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.479 No.-

<P><B>Abstract</B></P> <P>In this study, X-ZnO/ZnO/Si(100) (X = Co, Ni and Cu) bilayer structure is fabricated using low energy ion implantation technique. Five different fluences 1 × 10<SUP>15</SUP>, 5 × 10<SUP>15</SUP>, 1 × 10<SUP>16</SUP>, 2.5 × 10<SUP>16</SUP> and 5 × 10<SUP>16</SUP> ions/cm<SUP>2</SUP> with 100 keV ion-beam energy were selected in order to implant the ions up to the depth of ≈44 nm as calculated through Stopping Range of Ion in Matter and Transport Range of Ions in Matter software. Structural modification was investigated by high resolution X-ray diffraction measurements in ZnO bilayer system. An observed systematic 2<I>θ</I> shift in (002) peak with increasing fluence implies increased density of implanted metal ions in ZnO matrix revealing the substitution of implanted ion at Zn-site. The mechanism of bilayer formation by ion-beam implantation technique has been discussed for metal-ions by investigating their interface properties. Atomic force microscopy reveals the morphological modification after ion implantation. Near-edge X-ray absorption fine-structure (NEXAFS) measurements at metal <I>K</I>- and <I>L</I> <SUB>3,2</SUB>-edges have been used to investigate the nature of implanted ions in terms of their valance state and local electronic environment. Further, O <I>K</I>-edge NEXAFS measurement for Ni-ZnO/ZnO/Si bilayer is highly sensitive to incident beam angles whereas no spectral change is seen for Zn <I>L</I>-edge measurements. The magnetic measurements were performed via vibrating sample magnetometer that showed the films are ferromagnetic at room temperature. The origin of ferromagnetism has been understood through defect mediated bound magnetic polaron model. Further, perpendicular magnetic anisotropy is also observed for Ni-ZnO/ZnO/Si bilayer structure at room temperature, which is correlated with the angle dependent O K-edge NEXAFS measurements. Fabrication of ZnO bilayer via ion implantation and investigation of above properties may prove useful in spin related and optoelectronic applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Observance of RTFM in metal ion-implanted Ni-ZnO/ZnO/Si bilayer </LI> <LI> HRXRD and NEXAFS measurements confirms the wurtzite phase and Zn<SUP>2+</SUP> substitution in ZnO matrix. </LI> <LI> Angle dependent NEXAFS measurements provides the evidence of observed PMA. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>Mechanism of ion beam interaction X (X = Co, Ni and Cu) with ZnO lattice forming X-ZnO/ZnO/Si(100) bilayer structure. Films were implanted using a multi cathode source of negative-ions by cesium sputtering (MC-SNICS) and with the increasing ion flux, X can undergo one of two mechanisms of either substituting the Zn-site or occupy interstitial position in ZnO matrix. Angle dependent O K-edge NEXAFS measurements provides the evidence of perpendicular magnetic anisotropy in ZnO bilayer. </P> <P>[DISPLAY OMISSION]</P>

Immunomodulatory Effect of Tea Saponin in Immune T-cells and T-lymphoma Cells via Regulation of Th1, Th2 Immune Response and MAPK/ERK2 Signalling Pathway.

Bhardwaj JYOTI,Chaudhary NARENDRA,Hyo Jin SEO,Tai Sun SHIN,Min Yong KIM,Jong Deog KIM 한국생물공학회 2014 한국생물공학회 학술대회 Vol.2014 No.4

Transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes for a mixed-potential based NO₂ sensor

Bhardwaj, Aman,Kim, In-ho,Hong, Jae-woon,Kumar, Aniket,Song, Sun-Ju Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.284 No.-

<P><B>Abstract</B></P> <P>A mixed-potential based sensor utilizing transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes are fabricated for the first time and investigated for the gas sensing performance towards the highly toxic nitrogen dioxide. The nanocomposites are synthesized by solvo-combustion route and characterized for the physical, gas sensing and electrochemical properties in a temperature range of 600–700 ℃. The sensor equipped with Fe<SUB>2</SUB>O<SUB>3</SUB>-SnO<SUB>2</SUB> (Fe:Sn = 2:1) nanocomposite sensing electrodes sintered at 1000 ℃ shows the maximum response of 60 mV towards 100 ppm NO<SUB>2</SUB> with a relatively fast response and recovery dynamics at an operating temperature of 650 ℃. The sensor also shows a linear dependence of response over the logarithm of NO<SUB>2</SUB> concentration with a sensitivity of ∼44 mV/decade. Additionally, the oxygen concentration dependence, cyclability and cross-sensitivity towards interfering gases are also investigated. Finally, the sensing mechanism and electrochemical activity of the sensing electrodes are studied using polarization curve measurement and electrochemical impedance spectroscopy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mixed-potential based sensor utilizing transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>-SnO<SUB>2</SUB> nanocomposite sensing electrode responded 60mV towards 100ppm NO<SUB>2</SUB> at 650 ℃. </LI> <LI> The sensitivity of the sensor was found to be 44 mV/dec. in 10-100 ppm NO<SUB>2</SUB> concentration. </LI> <LI> The sensor displayed a low oxygen conc. dependence, high selectivity and high cyclability. </LI> <LI> Sensing mechanism and key parameters determining the sensing performance are discussed in details. </LI> </UL> </P>

Vertical flow-based paper immunosensor for rapid electrochemical and colorimetric detection of influenza virus using a different pore size sample pad

Bhardwaj, Jyoti,Sharma, Abhinav,Jang, Jaesung Elsevier Applied Science 2019 Biosensors & Bioelectronics Vol. No.

<P><B>Abstract</B></P> <P>We present a novel vertical flow-based paper immunosensor for the rapid and sensitive electrochemical and colorimetric detection of influenza H1N1 viruses using a different pore size (DP) sample pad. The DP sample pad consisted of two different pore size papers: larger pores (diameter: 11 µm) facing the inlet, and smaller pores (diameter: 0.45 µm) facing the conjugate pad. This sample pad offered moderate and uniform flows, and hence concentrated horseradish peroxidase tagged antibodies (HRP-Abs)-H1N1 complexes from 40 µL of sample volumes on a conjugate pad for 2 min after sample injection, thereby providing fast detection (6 min for both detection methods) with 100 µL of flushing afterwards, high sensitivity, and the simplicity of the sensor. The filtration characteristics of the DP sample pad were evaluated using fluorescent beads, indicating that only small-sized bio-particles such as viruses can pass through the sample pad. Sandwich immunoreactions of HRP-Ab-H1N1-Ab were performed on the gold paper electrode of the immunoStrip, which was determined by electrochemical impedance spectroscopy (EIS) measurements. Simultaneously, the color signal of free HRP-Ab captured on the colorimetric zone was obtained using a scanner, and the intensity was analyzed using ImageJ. This immunosensor detected H1N1 virus concentration as low as 3.3 plaque forming units (PFU)/mL (phosphate buffer saline; PBS) and 4.7 PFU/mL (saliva) by EIS, and 1.34 PFU/mL (PBS) and 2.27 PFU/mL (saliva) by the colorimetric method. Furthermore, integrating these two detection methods can reduce false results with double assurance, and this device can provide a simple and economical on-site detection platform.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The first paper immunosensor using a double pore size (DP) sample pad. </LI> <LI> The first vertical flow assay-based, sandwich ELISA-type paper immunosensor for the detection of influenza viruses. </LI> <LI> Dual (electrochemical and colorimetric) detection methods to provide double assurance. </LI> <LI> The DP sample pad offered fast detection (~6 min), high sensitivity (the limit of detection <5 PFU/mL), and the simplicity. </LI> <LI> The DP sample pad also acted as a filter to pass only small-sized particles. </LI> </UL> </P>

Density by Moduli and Korovkin Type Approximation Theorem of Boyanov and Veselinov

Bhardwaj, Vinod K.,Dhawan, Shweta Department of Mathematics 2018 Kyungpook mathematical journal Vol.58 No.4

The concept of f-statistical convergence which is, in fact, a generalization of statistical convergence, has been introduced recently by Aizpuru et al. (Quaest. Math. 37: 525-530, 2014). The main object of this paper is to prove an f-statistical analog of the classical Korovkin type approximation theorem of Boyanov and Veselinov. It is shown that the f-statistical analog is intermediate between the classical theorem and its statistical analog. As an application, we estimate the rate of f-statistical convergence of the sequence of positive linear operators defined from $C^*[0,{\infty})$ into itself.