A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethox... more A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) sol–gel matrices with purified MWCNT.
The development, optimization and validation of an analytical method for the detection and identi... more The development, optimization and validation of an analytical method for the detection and identification of reactive metabolite of nitrogen mustards (a Chemical Warfare Agent),i.e.half nitrogen mustards in blood samples by GC-MS/MS (PCI).
Unpurified rabbit anti-SEB polyclonal IgG and mice anti-SEB monoclonal IgG was purified by affini... more Unpurified rabbit anti-SEB polyclonal IgG and mice anti-SEB monoclonal IgG was purified by affinity chromatography based method as per details given by the manufacturer. In this method, unpurified serum sample was first mixed properly with the binding buffer. After that the "Protein A Cartridge" was washed with regeneration buffer. For this purpose, regeneration buffer was passed through the cartridge at the approx flow rate of 1mL/min. Then the cartridge was equilibrated by binding buffer by passing the binding buffer through the cartridge at the same flow rate. Then, we had loaded the sample-binding buffer mixture by passing it to the "Protein A Cartridge" at the approx flow rate of 0.5mL/min. Binding buffer was passed through the cartridge after the sample loading at the flow rate of about 1mL/min. Desalting cartridge was washed with [N-(2-hydroxyethyl)peiperazine-N'-(2-ethanesulfonic acid)] i.e. (HEPES) buffer by passing it through the cartridge at an approximate flow rate of 1mL/min. Then we had attached the one end of the "Protein A Cartridge" to another end of the desalting cartridge. Then, we had eluted the cartridges with elution buffer by passing it through the cartridges at an approximate flow rate of 0.5mL/minute. Elute was contained the purified IgG at physiological pH. After it, we had detached both the cartridges and regenerate them. "Protein A Cartridge" was regenerated by regeneration buffer by passing it through the cartridge. HEPES buffer was passed through the desalting cartridge and was regenerated. These cartridges are ready and can be used for another affinity chromatographic purification.
In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electroche... more In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electrochemical and fluorescence immunoassay methods using zinc sulphide (ZnS) QDs. Wet-chemical method was adopted for the preparation of fluorescent ZnS QDs (diameter ∼ 5-10 nm). These QDs were bioconjugated with monoclonal antibodies and then characterized by various method. A detection limit of 0.02 ng mL(-1) by fluorescence assay and 1.0 ng mL(-1) by electrochemical assay for SEB was achieved. While by sandwich ELISA it is possible to detect 0.24 ng mL(-1) only. The sensitivity of all techniques is very good, since the LD50 of SEB is 20 ng kg(-1). Electrochemical assay is faster, need low-cost instrument, independent to the size of QDs and found to be one of the best alternative methods as compared to the other existing methods studied herein. The presented method could be expanded to the development of electrochemical and fluorescence biosensors for various agents for field and laboratory use.
The hexafluoroisopropanol moiety was grafted onto graphene and used as a sensing layer for the de... more The hexafluoroisopropanol moiety was grafted onto graphene and used as a sensing layer for the detection of a nerve agent simulant using QCM.
Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (i... more Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (insects, mice and other animals, unwanted plants, fungi, microorganisms). They are fall into three major classes: insecticides, fungicides, and herbicides (or weed killers). There are also rodenticides (for control of vertebrate pests), nematicides (to kill microscopic eelworms), molluscicides (to kill slugs and snails), and acaricides (to kill mites).Considering their chemical structure, the pesticides are organophosphorous, carbamates, organochlorines, and pyrethroid ones (U.S. EPA, 2009). OP compounds are widely used in the agriculture industry around the world as pesticides and insecticides. Phosphorous plays a central role in the living organism; it is sufficient to mention photosynthesis, metabolism, and involvement in coenzyme systems etc. It can have a variety of oxidation states 3 and 5, generally OP compounds based on their derivatives of phosphorous. Organophosphate trimesters, phosphonates, phosphonofluoridates and phosphonothioates comprise broad class chemical neurotoxins ((Pesticides action network, Ullman agrochemicals) (Fig 1). However, the high toxicity of the OP compounds had not been recognized until the 1930s, when Lange and Krűger described effects, which they noticed during synthesis of some OP with the P-F bond (Holmstedt, 1963). German Chemists subsequently became interested in synthesizing insecticides. G.Schrader, in 1936, synthesized highly toxic OP insecticide ethyl-N,N-Dimethylphosphor-amidocyanidate (tabun) and iso-propyl methylphosphonofluoridate (sarin) in 1937 (Robinson & Leitenberg, 1971). Schrader synthesized the toxic OP compounds in search of better insecticides. Nerve agents are also OP compounds such as sarin (GB), tabun (GA), soman (GD) and VX are categorized as chemical warfare (CW) agents. During World War II, the Germans possessed large quantities of tabun and sarin although they were not used in that conflict. Nerve agents are divided into two main groups: the G-agents and Vagents. The G-agents are nonpersistent (sarin, soman, & tabun) and cause casualties primarily by inhalation. Sarin is highly volatile compared to tabun and soman. The V-agents are persistent (VX) they can therefore cause casualties by both inhalation and absorption through the skin.
Nitrogen doped graphene nanosheet coated interdigitated electrodes for sensitive detection of NO2... more Nitrogen doped graphene nanosheet coated interdigitated electrodes for sensitive detection of NO2 gas at room temperature.
A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethox... more A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) sol–gel matrices with purified MWCNT.
Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (i... more Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (insects, mice and other animals, unwanted plants, fungi, microorganisms). They are fall into three major classes: insecticides, fungicides, and herbicides (or weed killers). There are also rodenticides (for control of vertebrate pests), nematicides (to kill microscopic eelworms), molluscicides (to kill slugs and snails), and acaricides (to kill mites).Considering their chemical structure, the pesticides are organophosphorous, carbamates, organochlorines, and pyrethroid ones (U.S. EPA, 2009). OP compounds are widely used in the agriculture industry around the world as pesticides and insecticides. Phosphorous plays a central role in the living organism; it is sufficient to mention photosynthesis, metabolism, and involvement in coenzyme systems etc. It can have a variety of oxidation states 3 and 5, generally OP compounds based on their derivatives of phosphorous. Organophosphate trimesters, phosphonates, phosphonofluoridates and phosphonothioates comprise broad class chemical neurotoxins ((Pesticides action network, Ullman agrochemicals) (Fig 1). However, the high toxicity of the OP compounds had not been recognized until the 1930s, when Lange and Krűger described effects, which they noticed during synthesis of some OP with the P-F bond (Holmstedt, 1963). German Chemists subsequently became interested in synthesizing insecticides. G.Schrader, in 1936, synthesized highly toxic OP insecticide ethyl-N,N-Dimethylphosphor-amidocyanidate (tabun) and iso-propyl methylphosphonofluoridate (sarin) in 1937 (Robinson & Leitenberg, 1971). Schrader synthesized the toxic OP compounds in search of better insecticides. Nerve agents are also OP compounds such as sarin (GB), tabun (GA), soman (GD) and VX are categorized as chemical warfare (CW) agents. During World War II, the Germans possessed large quantities of tabun and sarin although they were not used in that conflict. Nerve agents are divided into two main groups: the G-agents and Vagents. The G-agents are nonpersistent (sarin, soman, & tabun) and cause casualties primarily by inhalation. Sarin is highly volatile compared to tabun and soman. The V-agents are persistent (VX) they can therefore cause casualties by both inhalation and absorption through the skin.
In this work, a novel electrochemical immunosensor was developed for the detection of botulinum n... more In this work, a novel electrochemical immunosensor was developed for the detection of botulinum neurotoxin-E (BoNT/E). This method relied on graphene nanosheets-aryldiazonium salt modified glassy carbon electrodes (GCE) as sensing platform and enzyme induced silver nanoparticles (AgNPs) deposited on gold nanoparticles (AuNPs) as signal amplifier. Herein, a GCE was electrografted with mixed monolayer of phenyl and aminophenyl (Ph-PhNH2/GCE) by diazotization reaction. Further, graphene nanosheets (GNS) were covalently attached on electrode surface (GNS/Ph-PhNH2/GCE). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize synthesized graphene oxide and modified electrode surfaces. In the sandwich immunoassay format, the sensitivity was amplified using rabbit anti-mouse IgG-alkaline phosphatase (RαMIgG-ALP) functionalized with gold nanoparticles (RαMIgG-ALP/AuNPs). In order to study the immunosensing performance of GNS/Ph-PhNH2/GCE, first the capturing antibody (rabbit-anti BoNT/E antibody) was covalently immobilized via EDC/NHS chemistry. Further, the electrode was sequentially subjected to sample containing spiked BoNT/E, revealing antibody (mouse-anti BoNT/E) followed by RαMIgG-ALP/AuNPs. 3-indoxyl phosphate (3-IP) was used as substrate which finally reduces the silver ions. The deposited AgNPs on electrode surface were determined by linear sweep voltammetry (LSV). The developed electrochemical immunosensor could detect BoNT/E with linear range from 10pg/ml to 10ng/ml with the minimum detection limit of 5.0pg/ml and total analysis time of 65min. In addition, the immunosensor was successfully evaluated against food samples (orange juice and milk).
In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electroche... more In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electrochemical and fluorescence immunoassay methods using zinc sulphide (ZnS) QDs. Wet-chemical method was adopted for the preparation of fluorescent ZnS QDs (diameter $ 5-10 nm). These QDs were bioconjugated with monoclonal antibodies and then characterized by various method. A detection limit of 0.02 ng mL À1 by fluorescence assay and 1.0 ng mL À1 by electrochemical assay for SEB was achieved. While by sandwich ELISA it is possible to detect 0.24 ng mL À1 only. The sensitivity of all techniques is very good, since the LD 50 of SEB is 20 ng kg À1. Electrochemical assay is faster, need low-cost instrument, independent to the size of QDs and found to be one of the best alternative methods as compared to the other existing methods studied herein. The presented method could be expanded to the development of electrochemical and fluorescence biosensors for various agents for field and laboratory use.
ABSTRACT Staphylococcal enterotoxin B (SEB) is a potent foodborne pathogen and categorized as a c... more ABSTRACT Staphylococcal enterotoxin B (SEB) is a potent foodborne pathogen and categorized as a class B type of biological warfare agent. In this research work, SEB is detected by various sensitive analytical methods such as enzyme linked immunosorbent assay (ELISA), quantum dots-based fluorescence linked immunosorbent assay (QDs-FLISA) and square-wave voltammetry (SWV). The obtained results were compared in terms of sensitivity, ease of experimentation and analysis time. For the QD-based detection, fluorescent lead sulfide (PbS) QDs were prepared by a bottom-up approach and characterized by various techniques. Highly specific antibodies against SEB were conjugated with the prepared PbS QDs and were used as revealing antibodies. For the electrochemical detection of SEB, rabbit anti-SEB polyclonal antibodies (primary antibodies) were immobilized on screen-printed electrodes (SPEs) followed by the addition of various concentrations of SEB antigen. These electrodes were further incubated with revealing antibodies. Finally, 1 M HCl solution was added to the SPE to dissolve the PbS QDs which were captured in a sandwiched immunoassay, and resulting Pb2+ ions were determined by the SWV method using a glassy-carbon electrode. The obtained peak current is proportional to the amount of Pb2+ ions which indirectly depends on the SEB concentration. Linearity was observed in the concentration range of 1 ng mL−1 to 1 μg mL−1 of SEB antigen. The limit of detection was found to be 0.01 ng mL−1 for SEB. The results reveal that electrochemical SWV sensing is much easier, faster and provides high sensitivity as compared to the other methods. It is found that the detection limits achieved for sandwich ELISA and QDs-FLISA were 0.24 ng mL−1 and 0.03 ng mL−1 respectively. In addition, the developed SWV method can be implemented for the on-site detection of SEB particularly for civil and defense applications where security is of prime importance.
ABSTRACT This paper describes the electrocatalytic activity of layer-by-layer self-assembled copp... more ABSTRACT This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV–vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1 M NaOH; such as low overpotentials (− 0.15 V vs Ag/AgCl), linear concentration range of 3 × 10− 5 M to 6 × 10− 3 M, and with a detection limit of 2.5 × 10− 5 M using simple amperometry.
A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethox... more A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) sol–gel matrices with purified MWCNT.
The development, optimization and validation of an analytical method for the detection and identi... more The development, optimization and validation of an analytical method for the detection and identification of reactive metabolite of nitrogen mustards (a Chemical Warfare Agent),i.e.half nitrogen mustards in blood samples by GC-MS/MS (PCI).
Unpurified rabbit anti-SEB polyclonal IgG and mice anti-SEB monoclonal IgG was purified by affini... more Unpurified rabbit anti-SEB polyclonal IgG and mice anti-SEB monoclonal IgG was purified by affinity chromatography based method as per details given by the manufacturer. In this method, unpurified serum sample was first mixed properly with the binding buffer. After that the "Protein A Cartridge" was washed with regeneration buffer. For this purpose, regeneration buffer was passed through the cartridge at the approx flow rate of 1mL/min. Then the cartridge was equilibrated by binding buffer by passing the binding buffer through the cartridge at the same flow rate. Then, we had loaded the sample-binding buffer mixture by passing it to the "Protein A Cartridge" at the approx flow rate of 0.5mL/min. Binding buffer was passed through the cartridge after the sample loading at the flow rate of about 1mL/min. Desalting cartridge was washed with [N-(2-hydroxyethyl)peiperazine-N'-(2-ethanesulfonic acid)] i.e. (HEPES) buffer by passing it through the cartridge at an approximate flow rate of 1mL/min. Then we had attached the one end of the "Protein A Cartridge" to another end of the desalting cartridge. Then, we had eluted the cartridges with elution buffer by passing it through the cartridges at an approximate flow rate of 0.5mL/minute. Elute was contained the purified IgG at physiological pH. After it, we had detached both the cartridges and regenerate them. "Protein A Cartridge" was regenerated by regeneration buffer by passing it through the cartridge. HEPES buffer was passed through the desalting cartridge and was regenerated. These cartridges are ready and can be used for another affinity chromatographic purification.
In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electroche... more In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electrochemical and fluorescence immunoassay methods using zinc sulphide (ZnS) QDs. Wet-chemical method was adopted for the preparation of fluorescent ZnS QDs (diameter ∼ 5-10 nm). These QDs were bioconjugated with monoclonal antibodies and then characterized by various method. A detection limit of 0.02 ng mL(-1) by fluorescence assay and 1.0 ng mL(-1) by electrochemical assay for SEB was achieved. While by sandwich ELISA it is possible to detect 0.24 ng mL(-1) only. The sensitivity of all techniques is very good, since the LD50 of SEB is 20 ng kg(-1). Electrochemical assay is faster, need low-cost instrument, independent to the size of QDs and found to be one of the best alternative methods as compared to the other existing methods studied herein. The presented method could be expanded to the development of electrochemical and fluorescence biosensors for various agents for field and laboratory use.
The hexafluoroisopropanol moiety was grafted onto graphene and used as a sensing layer for the de... more The hexafluoroisopropanol moiety was grafted onto graphene and used as a sensing layer for the detection of a nerve agent simulant using QCM.
Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (i... more Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (insects, mice and other animals, unwanted plants, fungi, microorganisms). They are fall into three major classes: insecticides, fungicides, and herbicides (or weed killers). There are also rodenticides (for control of vertebrate pests), nematicides (to kill microscopic eelworms), molluscicides (to kill slugs and snails), and acaricides (to kill mites).Considering their chemical structure, the pesticides are organophosphorous, carbamates, organochlorines, and pyrethroid ones (U.S. EPA, 2009). OP compounds are widely used in the agriculture industry around the world as pesticides and insecticides. Phosphorous plays a central role in the living organism; it is sufficient to mention photosynthesis, metabolism, and involvement in coenzyme systems etc. It can have a variety of oxidation states 3 and 5, generally OP compounds based on their derivatives of phosphorous. Organophosphate trimesters, phosphonates, phosphonofluoridates and phosphonothioates comprise broad class chemical neurotoxins ((Pesticides action network, Ullman agrochemicals) (Fig 1). However, the high toxicity of the OP compounds had not been recognized until the 1930s, when Lange and Krűger described effects, which they noticed during synthesis of some OP with the P-F bond (Holmstedt, 1963). German Chemists subsequently became interested in synthesizing insecticides. G.Schrader, in 1936, synthesized highly toxic OP insecticide ethyl-N,N-Dimethylphosphor-amidocyanidate (tabun) and iso-propyl methylphosphonofluoridate (sarin) in 1937 (Robinson & Leitenberg, 1971). Schrader synthesized the toxic OP compounds in search of better insecticides. Nerve agents are also OP compounds such as sarin (GB), tabun (GA), soman (GD) and VX are categorized as chemical warfare (CW) agents. During World War II, the Germans possessed large quantities of tabun and sarin although they were not used in that conflict. Nerve agents are divided into two main groups: the G-agents and Vagents. The G-agents are nonpersistent (sarin, soman, & tabun) and cause casualties primarily by inhalation. Sarin is highly volatile compared to tabun and soman. The V-agents are persistent (VX) they can therefore cause casualties by both inhalation and absorption through the skin.
Nitrogen doped graphene nanosheet coated interdigitated electrodes for sensitive detection of NO2... more Nitrogen doped graphene nanosheet coated interdigitated electrodes for sensitive detection of NO2 gas at room temperature.
A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethox... more A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) sol–gel matrices with purified MWCNT.
Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (i... more Pesticides are chemicals designed for preventing, destroying, repelling or mitigating any pest (insects, mice and other animals, unwanted plants, fungi, microorganisms). They are fall into three major classes: insecticides, fungicides, and herbicides (or weed killers). There are also rodenticides (for control of vertebrate pests), nematicides (to kill microscopic eelworms), molluscicides (to kill slugs and snails), and acaricides (to kill mites).Considering their chemical structure, the pesticides are organophosphorous, carbamates, organochlorines, and pyrethroid ones (U.S. EPA, 2009). OP compounds are widely used in the agriculture industry around the world as pesticides and insecticides. Phosphorous plays a central role in the living organism; it is sufficient to mention photosynthesis, metabolism, and involvement in coenzyme systems etc. It can have a variety of oxidation states 3 and 5, generally OP compounds based on their derivatives of phosphorous. Organophosphate trimesters, phosphonates, phosphonofluoridates and phosphonothioates comprise broad class chemical neurotoxins ((Pesticides action network, Ullman agrochemicals) (Fig 1). However, the high toxicity of the OP compounds had not been recognized until the 1930s, when Lange and Krűger described effects, which they noticed during synthesis of some OP with the P-F bond (Holmstedt, 1963). German Chemists subsequently became interested in synthesizing insecticides. G.Schrader, in 1936, synthesized highly toxic OP insecticide ethyl-N,N-Dimethylphosphor-amidocyanidate (tabun) and iso-propyl methylphosphonofluoridate (sarin) in 1937 (Robinson & Leitenberg, 1971). Schrader synthesized the toxic OP compounds in search of better insecticides. Nerve agents are also OP compounds such as sarin (GB), tabun (GA), soman (GD) and VX are categorized as chemical warfare (CW) agents. During World War II, the Germans possessed large quantities of tabun and sarin although they were not used in that conflict. Nerve agents are divided into two main groups: the G-agents and Vagents. The G-agents are nonpersistent (sarin, soman, & tabun) and cause casualties primarily by inhalation. Sarin is highly volatile compared to tabun and soman. The V-agents are persistent (VX) they can therefore cause casualties by both inhalation and absorption through the skin.
In this work, a novel electrochemical immunosensor was developed for the detection of botulinum n... more In this work, a novel electrochemical immunosensor was developed for the detection of botulinum neurotoxin-E (BoNT/E). This method relied on graphene nanosheets-aryldiazonium salt modified glassy carbon electrodes (GCE) as sensing platform and enzyme induced silver nanoparticles (AgNPs) deposited on gold nanoparticles (AuNPs) as signal amplifier. Herein, a GCE was electrografted with mixed monolayer of phenyl and aminophenyl (Ph-PhNH2/GCE) by diazotization reaction. Further, graphene nanosheets (GNS) were covalently attached on electrode surface (GNS/Ph-PhNH2/GCE). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize synthesized graphene oxide and modified electrode surfaces. In the sandwich immunoassay format, the sensitivity was amplified using rabbit anti-mouse IgG-alkaline phosphatase (RαMIgG-ALP) functionalized with gold nanoparticles (RαMIgG-ALP/AuNPs). In order to study the immunosensing performance of GNS/Ph-PhNH2/GCE, first the capturing antibody (rabbit-anti BoNT/E antibody) was covalently immobilized via EDC/NHS chemistry. Further, the electrode was sequentially subjected to sample containing spiked BoNT/E, revealing antibody (mouse-anti BoNT/E) followed by RαMIgG-ALP/AuNPs. 3-indoxyl phosphate (3-IP) was used as substrate which finally reduces the silver ions. The deposited AgNPs on electrode surface were determined by linear sweep voltammetry (LSV). The developed electrochemical immunosensor could detect BoNT/E with linear range from 10pg/ml to 10ng/ml with the minimum detection limit of 5.0pg/ml and total analysis time of 65min. In addition, the immunosensor was successfully evaluated against food samples (orange juice and milk).
In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electroche... more In this paper an attempt was made to detect Staphylococcal enterotoxin B (SEB) both by electrochemical and fluorescence immunoassay methods using zinc sulphide (ZnS) QDs. Wet-chemical method was adopted for the preparation of fluorescent ZnS QDs (diameter $ 5-10 nm). These QDs were bioconjugated with monoclonal antibodies and then characterized by various method. A detection limit of 0.02 ng mL À1 by fluorescence assay and 1.0 ng mL À1 by electrochemical assay for SEB was achieved. While by sandwich ELISA it is possible to detect 0.24 ng mL À1 only. The sensitivity of all techniques is very good, since the LD 50 of SEB is 20 ng kg À1. Electrochemical assay is faster, need low-cost instrument, independent to the size of QDs and found to be one of the best alternative methods as compared to the other existing methods studied herein. The presented method could be expanded to the development of electrochemical and fluorescence biosensors for various agents for field and laboratory use.
ABSTRACT Staphylococcal enterotoxin B (SEB) is a potent foodborne pathogen and categorized as a c... more ABSTRACT Staphylococcal enterotoxin B (SEB) is a potent foodborne pathogen and categorized as a class B type of biological warfare agent. In this research work, SEB is detected by various sensitive analytical methods such as enzyme linked immunosorbent assay (ELISA), quantum dots-based fluorescence linked immunosorbent assay (QDs-FLISA) and square-wave voltammetry (SWV). The obtained results were compared in terms of sensitivity, ease of experimentation and analysis time. For the QD-based detection, fluorescent lead sulfide (PbS) QDs were prepared by a bottom-up approach and characterized by various techniques. Highly specific antibodies against SEB were conjugated with the prepared PbS QDs and were used as revealing antibodies. For the electrochemical detection of SEB, rabbit anti-SEB polyclonal antibodies (primary antibodies) were immobilized on screen-printed electrodes (SPEs) followed by the addition of various concentrations of SEB antigen. These electrodes were further incubated with revealing antibodies. Finally, 1 M HCl solution was added to the SPE to dissolve the PbS QDs which were captured in a sandwiched immunoassay, and resulting Pb2+ ions were determined by the SWV method using a glassy-carbon electrode. The obtained peak current is proportional to the amount of Pb2+ ions which indirectly depends on the SEB concentration. Linearity was observed in the concentration range of 1 ng mL−1 to 1 μg mL−1 of SEB antigen. The limit of detection was found to be 0.01 ng mL−1 for SEB. The results reveal that electrochemical SWV sensing is much easier, faster and provides high sensitivity as compared to the other methods. It is found that the detection limits achieved for sandwich ELISA and QDs-FLISA were 0.24 ng mL−1 and 0.03 ng mL−1 respectively. In addition, the developed SWV method can be implemented for the on-site detection of SEB particularly for civil and defense applications where security is of prime importance.
ABSTRACT This paper describes the electrocatalytic activity of layer-by-layer self-assembled copp... more ABSTRACT This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV–vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1 M NaOH; such as low overpotentials (− 0.15 V vs Ag/AgCl), linear concentration range of 3 × 10− 5 M to 6 × 10− 3 M, and with a detection limit of 2.5 × 10− 5 M using simple amperometry.
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