title: Electrochemical immunosensor based on bismuth nanocomposite film and cadmium ions functionalized titanium phosphates for the detection of anthrax protective antigen toxin.
abstract: Bacillus anthracis is a bioterrorism agent classified by the Centers for Disease Control and Prevention (CDC). Herein, a novel electrochemical immunosensor for the sensitive, specific and easy detection of anthrax protective antigen (PA) toxin in picogram concentration was developed. The immunosensor consists of (i) a Nafion-multiwall carbon nanotubes-bismuth nanocomposite film modified glassy carbon electrodes (BiNPs/Nafion-MWCNTs/GCE) as a sensing platform and (ii) titanium phosphate nanoparticles-cadmium ion-mouse anti-PA antibodies (TiP-Cd(2+)-MαPA antibodies) as signal amplification tags. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), thermogravimmetric analysis (TGA), Fourier transform-infra red spectroscopy (FT-IR), zeta-potential analysis, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize the synthesized TiP nanoparticles and modified electrode surfaces. The immunosensing performance of BiNPs/Nafion-MWCNTs/GCE was evaluated based on sandwich immunoassay protocol. A square wave voltammetry (SWV) scan from -1.2 to -0.3 V in HAc-NaAc buffer solution (pH 4.6) without stripping process was performed to record the electrochemical responses at -0.75 V corresponding to high content of Cd(2+) ions loaded in TiP nanoparticles for the measurement of PA toxin. Under optimal conditions, the currents increased with increasing PA toxin concentrations in spiked human serum samples and showed a linear range from 0.1 ng/ml to 100 ng/ml. The limit of detection of developed immunosensor was found to be 50 pg/ml at S/N=3. The total time of analysis was 35 min.
authors.affiliation: Biosensor Development Division, Defence Research and Development Establishment, Jhansi road, Gwalior, M.P. 474002, India. Electronic address: mksharma@drde.drdo.in.
authors.forename: Mukesh K
authors.initials: MK
authors.lastname: Sharma
authors.affiliation: Biosensor Development Division, Defence Research and Development Establishment, Jhansi road, Gwalior, M.P. 474002, India.
authors.forename: J
authors.initials: J
authors.lastname: Narayanan
authors.affiliation: Biosensor Development Division, Defence Research and Development Establishment, Jhansi road, Gwalior, M.P. 474002, India.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Upadhyay
authors.affiliation: Biotechnology Division, Defence Research and Development Establishment, Jhansi road, Gwalior, M.P. 474002, India. Electronic address: akgoel73@yahoo.co.uk.
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Goel
mesh_terms: D000942:Antigens, Bacterial / Q000097:blood*; D001427:Bacterial Toxins / Q000097:blood*; D015374:Biosensing Techniques / Q000379:methods*; D001729:Bismuth / Q000737:chemistry*; D002104:Cadmium / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000379:methods; D004566:Electrodes; D005465:Fluorocarbon Polymers / Q000737:chemistry; D006801:Humans; D057230:Limit of Detection; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D037742:Nanotubes, Carbon / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*
chemical_list: D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D005465:Fluorocarbon Polymers; D037742:Nanotubes, Carbon; C030325:anthrax toxin; D002104:Cadmium; C036532:titanium phosphate; C040402:perfluorosulfonic acid; D014025:Titanium; D001729:Bismuth
keywords: Bacillus anthracis; Bismuth nanocomposite; Immunosensors; Protective antigen; Square wave voltammetry; Titanium phosphate