title: A silicon nitride ISFET based immunosensor for Ag85B detection of tuberculosis.
abstract: A silicon nitride Ion Sensitive Field Effect Transistor (ISFET) based immunosensor was developed as a low-cost and label-free electrical detection for the detection of antigen 85 complex B (Ag85B). The sensing membrane of the ISFET was modified with 3-aminopropyltriethoxysilane (APTES) followed by glutaraldehyde (GA), yielding an aldehyde-terminated surface. This group is available for immobilization of a monoclonal antibody against a recombinant Ag85B protein (anti-Ag85B antibody). The optimal concentration for anti-Ag85B antibody immobilization onto the modified ISFET was 100 μg ml-1. This optimal condition provided the maximal binding capability and minimal non-specific background signal. The binding event between the recombinant Ag85B antigen and anti-Ag85B antibody on the ISFET surface is presented by monitoring the gate potential change at a constant drain current. The dose response for the recombinant Ag85B protein showed a linear response between 0.12 and 1 μg ml-1without significant interference from other recombinant proteins. The analytical imprecision (CV%) and accuracy of this Ag85B protein biosensor were 9.73-10.99% and 95.29%, respectively. In addition, an irrelevant antibody and other recombinant proteins were employed as a negative control to demonstrate the non-specific interaction of the antigen and antibody. The success of this immunosensor system for Ag85B protein detection facilitates the construction of a promising device which can shorten the turnaround time for the diagnosis of tuberculosis compared to a standard culture method. Furthermore, this device could also be applied for real-time growth monitoring of Mycobacterium tuberculosis in a mycobacterial culture system.
authors.affiliation: Department of Clinical Chemistry, Faculty of Medical Technology, Mahidol University, Nakhon Pathom 73170, Thailand.
authors.forename: Pawasuth
authors.initials: P
authors.lastname: Saengdee
authors.forename: Woraphan
authors.initials: W
authors.lastname: Chaisriratanakul
authors.forename: Win
authors.initials: W
authors.lastname: Bunjongpru
authors.forename: Witsaroot
authors.initials: W
authors.lastname: Sripumkhai
authors.forename: Awirut
authors.initials: A
authors.lastname: Srisuwan
authors.forename: Charndet
authors.initials: C
authors.lastname: Hruanun
authors.forename: Amporn
authors.initials: A
authors.lastname: Poyai
authors.forename: Ponrut
authors.initials: P
authors.lastname: Phunpae
authors.forename: Supansa
authors.initials: S
authors.lastname: Pata
authors.forename: Wutthinan
authors.initials: W
authors.lastname: Jeamsaksiri
authors.forename: Watchara
authors.initials: W
authors.lastname: Kasinreak
authors.forename: Chamras
authors.initials: C
authors.lastname: Promptmas
mesh_terms: D000217:Acyltransferases / Q000032:analysis*; D055910:Antibodies, Immobilized; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000032:analysis*; D001426:Bacterial Proteins / Q000032:analysis*; D015374:Biosensing Techniques; D005976:Glutaral; D007477:Ions; D009169:Mycobacterium tuberculosis / Q000254:growth & development; D011437:Propylamines; D012821:Silanes; D017655:Silicon Compounds; D014376:Tuberculosis / Q000175:diagnosis*
chemical_list: D055910:Antibodies, Immobilized; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D007477:Ions; D011437:Propylamines; D012821:Silanes; D017655:Silicon Compounds; D000217:Acyltransferases; C121433:antigen 85B, Mycobacterium tuberculosis; C477625:amino-propyl-triethoxysilane; C032734:silicon nitride; D005976:Glutaral