A new approach to immunoFET operation

Schasfoort, Richardus B.M.; Kooyman, R.P.H.; Bergveld, Piet; Greve, Jan

doi:10.1016/0956-5663(90)80002-u

Cited by 86 publications

(49 citation statements)

References 8 publications

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“…Success or failure could only be tested by completion of the total procedure, since the result is also determined by the membrane properties, we used for adsorption of the antibodies. The membrane preparation was kept identical to the procedure used in earlier immuno experiments [ 1,2].…”

Section: Discussionmentioning

confidence: 99%

“…It was known from earlier experiments [2] that lysozyme, if adsorbed to a bare membrane, shifts the inversion point from p1' = 2.0 to p1' = 7.0. We found that the non-specific adsorption could be extensively reduced, if after adsorption of anti-progesterone at high concentration, a blocking of the remaining sites in the membrane by incubation with polyethylene glycol (MW 20 kD) was carried out.…”

Section: Conjugate Preparationmentioning

confidence: 99%

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Competitive immunological detection of progesterone by means of the ion-step induced response of an immunoFET

Schasfoort

Keldermans

Kooyman

et al. 1990

Sensors and Actuators B: Chemical

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The ion-step method was originally designed to measure immunoreactions via the change in charge density which occurs in an antibody loaded membrane, deposited on an ISFET, upon reaction with a charged antigen. In this paper we show the possibility of detecting an immunoreaction involving a non-charged antigen, progesterone, by using competitive binding of progesterone and a charged progesterone-lysozyme conjugate in the membrane. Both the immunoreaction and the non-specific binding could unequivocally be measured. The detection limit was approximately lo-* M of progesterone in the sample solution. This proves that the ion-step method is suitable for detection of both charged and non-charged antigens.tions can be determined, provided they cause a change in charge density in the membrane. Details of the detection method are described by Schasfoort et al. [ 1, 21. The purpose of this paper is to show an application of the ion-step method to an immunochemical model system, in which the analyte is uncharged. As a model system we have chosen the immunological reaction between progesterone and anti-progesterone. As before, the antibody is incorporated in the membrane which is deposited on an ISFET. Progesterone is an uncharged molecule, so it cannot be detected directly by using the ion-step method. However detection can

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Section: Discussionmentioning

confidence: 99%

Section: Conjugate Preparationmentioning

confidence: 99%

Competitive immunological detection of progesterone by means of the ion-step induced response of an immunoFET

Schasfoort

Keldermans

Kooyman

et al. 1990

Sensors and Actuators B: Chemical

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“…By substituting in Eq. [1], we obtain the step is considered immediate. This is acceptable since the following for the proton dissociation equilibrium of groups rise in the KNO 3 concentration at the electrolyte/membrane of type j: interface and the subsequent KNO 3 diffusion through the membrane are completed in about 1 s, which is negligible on the scale of the measured transient (3).…”

Section: General Assumptions Top Of Both Ion Sensors Is Deposited a Mmentioning

confidence: 99%

“…Proton titration curves / pK a ,med, j / pK a,el, j / log a j (t, x) 1 0 a j (t, x) , [1] describe s w as a function of c e and pH e , and are obtained by solving Eqs. [2], [4], and [5].…”

Section: General Assumptions Top Of Both Ion Sensors Is Deposited a Mmentioning

confidence: 99%

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Constructing a Proton Titration Curve from Ion-Step Measurements, Applied to a Membrane with Adsorbed Protein

Eijkel

Bosch

Olthuis

et al. 1997

Journal of Colloid and Interface Science

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Previously it was shown that the potential transient is A new measuring method is described for obtaining a proton determined by a proton release or uptake in the membrane titration curve. The curve is obtained from a microporous compos-(7). In this paper the theoretical relationships are derived ite membrane, consisting of polystyrene beads in an agarose ma-between the amplitude and the duration of the transients and trix, with lysozyme molecules adsorbed to the bead surface. The the proton titration curve of the membrane at a certain pH.membrane is incorporated into a sensor system by deposition on a Using these relationships, and measuring the potential transilicon chip with a pH-sensitive ion-sensitive field effect transistor sients at a series of pH values, it will be possible to construct (ISFET) located in the middle of a Ag/AgCl electrode. The actual a titration curve and thus to obtain information on adsorbed measurement is performed by creating a stepwise change in the macromolecules. For biosensor purposes, the relationships salt concentration of the bathing electrolyte (the ion step) and measuring the ISFET potential versus the Ag/AgCl electrode. This can also be applied in the inverse direction; i.e., the device potential shows a transient change in the ion step, which indicates response can be predicted from known titrational behavior a transient pH change in the membrane. This procedure is re-of the different components. In this paper the adsorption peated at a series of pH values. Equations are presented to calcu-of the positively charged protein lysozyme is studied as a late the proton titration curve of the membrane from the amplitude model. and duration of the measured transients. Measurements showThe measurements presented can be regarded as an extenqualitative agreement between the curves obtained and equilib-sion of common practice in protein titration, namely, the rium titration experiments on the same system. ᭧ 1997 Academic Press relative positioning of the titration curves at different ionic Key Words: proton titration; ion-sensitive field effect transistor; strengths by using the pH change that results from a change polystyrene bead; lysozyme; concentration step; Ag/AgCl elecin ionic strength (8,9). In this type of experiment, the pH trode.change is measured at only one initial pH value. In the investigations presented the method is extended by measuring at a series of pH values. The extension is made possible

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Immunologically Sensitive Field‐Effect Transistors

Zachariah

Gopalakrishnakone

Neužil

2006

Encyclopedia of Medical Devices and Instrumentation

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The Immunologically Sensitive Field‐Effect Transistors (IMFETs) represent the amalgamation of the technologies of Solid‐state electronics and Immunodiagnostics. The immunosensor is fabricated by immobilizing immunoagent, preferably, antibody on the gate region of an Ion‐Sensitive Field Effect Transistor (ISFET). Consequently, IMFETs embodying a range of monoclonal antibodies and the unique ISFET transduction mechanism could, in principle, be made possible for detection of a wide array of analytes, ranging from small biomolecules to bacteria. There have been several studies describing the application of ISFET as the IMFET, and they are broadly discussed in two headings, viz., Direct‐acting (label free) IMFET and Indirect‐sensing IMFET. In the label free approach, antibody‐antigen reaction has been monitored without addition of enzyme labels. Whereas the latter approach utilizes the advantage of enzyme label to indirectly monitor the antibody‐antigen reaction with pH‐sensitive ISFET. This chapter describes the challenges met with the development of practical IMFETs, their strengths and limitations.

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A new approach to immunoFET operation

Cited by 86 publications

References 8 publications

Competitive immunological detection of progesterone by means of the ion-step induced response of an immunoFET

Competitive immunological detection of progesterone by means of the ion-step induced response of an immunoFET

Constructing a Proton Titration Curve from Ion-Step Measurements, Applied to a Membrane with Adsorbed Protein

Immunologically Sensitive Field‐Effect Transistors

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