Ultrasensitive Immunosensor for Cancer Biomarker Proteins Using Gold Nanoparticle Film Electrodes and Multienzyme-Particle Amplification

TLDR

The immunosensor employs a densely packed gold nanoparticle platform coupled with magnetic bead bioconjugates that carry 7,500 horseradish peroxidase labels and detection antibodies, enabling ultrasensitive electrochemical detection of cancer biomarkers in serum. The sensors achieved a sensitivity of 31.5 µA mL ng⁻¹ and a detection limit of 0.5 pg mL⁻¹ (5 fg PSA), eight times lower than a prior CNT‑forest sensor, and correlated well with ELISA, indicating strong potential for bioelectronic arrays.

Abstract

A densely packed gold nanoparticle platform combined with a multiple-enzyme labeled detection antibody-magnetic bead bioconjugate was used as the basis for an ultrasensitive electrochemical immunosensor to detect cancer biomarkers in serum. Sensitivity was greatly amplified by synthesizing magnetic bioconjugates particles containing 7500 horseradish peroxidase (HRP) labels along with detection antibodies (Ab2) attached to activated carboxyl groups on 1 μm diameter magnetic beads. These sensors had sensitivity of 31.5 μA mL ng−1 and detection limit (DL) of 0.5 pg mL−1 for prostate specific antigen (PSA) in 10 μL of undiluted serum. This represents an ultralow mass DL of 5 fg PSA, 8-fold better than a previously reported carbon nanotube (CNT) forest immunosensor featuring multiple labels on carbon nanotubes, and near or below the normal serum levels of most cancer biomarkers. Measurements of PSA in cell lysates and human serum of cancer patients gave excellent correlations with standard ELISA assays. These easily fabricated AuNP immunosensors show excellent promise for future fabrication of bioelectronic arrays.