Kynurenic Acid Electrochemical Immunosensor: Blood-Based Diagnosis of Alzheimer's Disease.

Jose Marrugo-Ramírez,Mónica Mir,Montserrat Rodríguez-Núñez,Josep Samitier,M.-Pilar Marco

doi:10.3390/bios11010020

Abstract

Alzheimer’s disease (AD) is a neurodegenerative disorder, characterized by a functional deterioration of the brain. Currently, there are selected biomarkers for its diagnosis in cerebrospinal fluid. However, its extraction has several disadvantages for the patient. Therefore, there is an urgent need for a detection method using sensitive and selective blood-based biomarkers. Kynurenic acid (KYNA) is a potential biomarker candidate for this purpose. The alteration of the KYNA levels in blood has been related with inflammatory processes in the brain, produced as a protective function when neurons are damaged. This paper describes a novel electrochemical immunosensor for KYNA detection, based on successive functionalization multi-electrode array. The resultant sensor was characterized by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The proposed biosensor detects KYNA within a linear calibration range from 10 pM to 100 nM using CA and EIS, obtaining a limit of detection (LOD) of 16.9 pM and 37.6 pM in buffer, respectively, being the lowest reported LOD for this biomarker. Moreover, to assess our device closer to the real application, the developed immunosensor was also tested under human serum matrix, obtaining an LOD of 391.71 pM for CA and 278.8 pM for EIS with diluted serum.

Highlights

Alzheimer’s disease (AD) is the primary common cause of dementia in people over the age of 60, and the 3rd leading cause of death for the elderly population
We describe in this paper the development of a robust, reliable, and non-invasive detection platform based on an electrochemical immunosensor for the analysis of kynurenic acid (KYNA) concentrations in blood, to move towards an automated platform for the non-invasive early diagnosis of AD that contains different bioreceptors for the detection of blood biomarkers in an array format
The immunoreagents used for KYNA detection, the polyclonal antiserum As301, used as a KYNA receptor (KYNA-Ab), and the bioconjugate derived from bovine serum albumin (BSA), As301/BSA-CHNH2, used as pseudo-KYNA labeled to BSA (BSA-pseudo-KYNA), were developed by the Nanobiotechnology for Diagnostics (Nb4D) group with the support of the Infraestructuras Científico-Tecnológicas Singulares (ICTS) “NANBIOSIS”, by the Custom Antibody Service (CAbS, CIBER-BBN, IQAC-CSIC)

Summary

Introduction

Alzheimer’s disease (AD) is the primary common cause of dementia in people over the age of 60, and the 3rd leading cause of death for the elderly population. AD is a progressive deterioration of the neuronal cells until their death, being currently incurable. This disease is mainly characterized by the abnormal accumulation of extracellular amyloid in plaques, where its main component is the amyloid beta peptide (Aβ42). Intraneuronal neurofibrillary tangle aggregates, formed by hyperphosphorylated tau (P-τ) protein, are accumulated in the cerebral vasculature, with a subsequent loss of neuronal and synaptic activity in selected brain areas. Due to these alterations, astrocytes and microglia are activated, resulting in neuroinflammation and the death of neurons [3,4]

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Results

Conclusion