Semi-Automated Electrochemical Microfluidic Immunoarray for Cancer Diagnostics

Abstract

Over-expression of Parathyroid hormone-related peptide (PTHrP) is recognized as the main causative agent of the paraneoplastic syndrome, humoral hypercalcemia of malignancy (HHM). PTHrP is known to be indicative of progression and metastasis of several human cancers. The established prognosis method of PTHrP, immunoradiometric assay (IRMA), is unable to determine the peptide levels prior to the advancement of hypercalcemia due to insufficient sensitivity. Prostate specific antigen (PSA) is a biomarker that has been extensively used as a diagnostic tool in prostate cancer. Unfortunately, PSA is limited in its’ inability to distinguish cancer from other prostate conditions such as Benign Prostatic Hyperplasia (BPH) or Prostatitis. These inaccuracies lead to unnecessary treatments including surgery on indolent cancer patients that adversely affect the patients’ quality of life. Therefore, there is strong appeal for the development of ultrasensitive, low cost multiplexed detection of appropriate biomarkers in clinically relevant ranges to assist the diagnosis and progression of cancers. Here we have employed a lab-developed microfluidic immunoarray for small samples, that features automation, miniaturisation, sensitivity adjustable to the sample characteristics, rapid analysis, and low reagent consumption for the detection of PTHrP and PSA in human cancer patient serum. The immunoarrays employ nanostructured sensors decorated with capture antibodies to perform a sandwich immunoassay using poly-horseradish peroxidase (poly-HRP) with about 80 HPRs per molecule that links to a secondary antibody bound to analytes on the sensor for high sensitivity detection. Incubation times were tailored to obtain limits of detection (LOD) in sub-fg mL-1 without a significant compromise in sensitivity leading to a simple, quick cancer diagnostics and personalized cancer therapy strategies. This may be able to transform the current methods of prostate cancer diagnosis. This system will be utilized to evaluate PTHrP peptides as aggressive prostate cancer biomarkers by analysis of human serum samples from patients.