Innovative gold-free carbon nanotube/chitosan-based competitive immunosensor for determination of HIV-related p24 capsid protein in serum

In the past decade, the need for simple, rapid, sensitive, specific and inexpensive screening methods for diagnosis of HIV infection has led to a focus on the HIV1-related capsid protein p24. In this work, the first competitive electrochemical immunosensor for the detection of p24 in untreated human serum was developed as a simple, easy-to-use and promising tool for serum screening for early diagnosis of HIV infection. The immunodevice was implemented on disposable gold-free single-walled carbon nanotube-functionalized screen-printed electrodes. The competitive sensor is based on the immobilization of the target protein on the electrode surface using a chitosan/glutaraldehyde crosslinking system, able to ensure, under mild conditions, a robust immobilization and a proper exposition of p24 for interaction with a mouse anti-p24 IgG1. The immunosensor setup as well as the assay's experimental conditions were then optimized, achieving a wide linear detection range of 10 pM to 1 nM, with a low detection limit of 2 pM in human serum. The good performance, also in terms of selectivity, trueness and precision, coupled with the advantages of an easy preparation compared to other methods requiring very complex conjugation procedures between bioreceptors and expensive nanostructures, makes the immunosensor a powerful diagnostic tool, valuable for implementation of large-scale screening programs for early diagnosis of seropositivity.