Interdigitated Conductometric Immunosensor for Determination of Interleukin‐6 in Humans Based on Dendrimer G4 and Colloidal Gold Modified Composite Film

Abstract

A highly sensitive, fast and stable conductometric immunosensor for determination of interleukin-6 (IL6) in humans is developed by encapsulation of horseradish peroxidase-labeled interleukin-6 antibody (HRP-anti-IL6) in poly(amidoamine) fourth-generation dendrimer (dendrimer) and colloidal gold (nanogold) modified composite architecture. The presences of nanogold and dendrimer provided a congenial microenvironment for the immobilized biomolecules and decreased the electron transfer impedance, leading to a direct electrochemical behavior of the immobilized HRP. The formation of the antibody-antigen complex by a simple one-step immunoreaction between the immobilized HRP-anti-IL6 and IL6 in sample solution introduced a barrier of direct electrical communication between the immobilized HRP and the gold electrode surface, thus local conductivity variations could be detected by the HRP electrocatalytic reaction in 0.02 M phosphate buffer solution (pH 7.0) containing 50 mM H 2 O 2 , 0.01 M KI and 0.15 M NaC1. Under optimal conditions, the proposed immunosensor exhibited a good conductometric response to IL6 in a linear range from 30 to 300 pg/mL with a relatively low detection limit of 10 pg/mL at 3d. The precision and reproducibility are acceptable with the intra-assay CV of 7.3% and 5.6% at 100 and 200 pg/mL IL6, respectively. The storage stability of the proposed immunosensor is acceptable in a pH 7.0 PBS at 4 8C for 8 days. Importantly, the proposed methodology could be extended to the detection of other antigens or biocompounds.

Multifunctional Dendrimer‐Templated Antibody Presentation on Biosensor Surfaces for Improved Biomarker Detection

“…The lower limit of detection (LLD, 3STD) of IL-6 was determined to be 0.29 pg ml -1 for TMB detection and 0.13 pg ml -1 for luminol detection (Table 1). In literature, various methods have been developed for determination of IL-6 levels, such as microfluidic immunosensor, [22a] conductometric immunosensor, [8b] microsphere-based immunoassay [52] and capacitive biosensor [53] with varying detection limits. Dendrimer based assay in present study has a detection limit superior to that of other previously reported IL-6 assay except that obtained by Johansson et al .…”

“…[5] In addition, dendrimers can have a larger area of capture than linear analogs with consequently high capture probability. Dendrimers have been utilized in dip-pen nanolithography, [6] DNA and protein arrays, [7] nanocatalyst-based electrochemical immunosensor, [8] biosensor-based on dendrimer encapsulated Pt nanoparticles [9] and regenerable affinity biosensing surfaces. [10] Recent work on a glass surface coated with a polyamidoamine dendrimer terminated with carboxylic acid group (PAMAM-COOH), showed that the dendrimer-modified surface had relatively low nonspecific cellular protein adsorption, and can also enable antibody binding.…”

Conductometric immunoassay for interleukin-6 in human serum based on organic/inorganic hybrid membrane-functionalized interface

“…Therefore, the sensitive part of each electrode was about 1 mm 2 . The schematic diagram of the interdigitated transducer is described in previous report [13].…”

“…Conductometric immunoassays with highly specific molecular recognition of antigens by antibodies have become important analytical tools in clinical and biochemical analyses and for monitoring of environment and food quality control, since it is highly sensitive, low cost, low power requirements, and has high compatibility with advanced micromachining technologies [8][9][10][11][12]. Moreover, the technology has been developed for the detection of interleukin-6 by using an interdigitated conductometric immunosensor in our report previously [13].…”

Magnetic colorimetric immunoassay for human interleukin-6 based on the oxidase activity of ceria spheres

“…Several methods have been used to detect the level of IL-6 in diseased tissues including enzyme-linked immunosorbent assay (ELISA) [10], fluorescent sensor [11], conductometric immunosensor [12], chemiluminescence immunoassay [13], fluorescence-based fiber-opticbiosensors [14] and electrochemical immunosensor [6,15]. However, sophisticated instrumentation and relatively low limits of detection (LODs) for these methods restrict their further application for detecting early stage disease in real samples.…”