Abstract
Point-of-care devices are expected to play very critical roles in early diagnosis and better treatment of cancer. Here, we report the end-to-end development of novel and portable biosensors for detecting carcinoembryonic antigen (CEA), a cancer biomarker, almost instantly at room temperature. The device uses reduced graphene oxide (rGO) as the base conducting layer and a novel poly[(1,4-phenylene)-alt-(3,6-(1,2,4,5-tetrazine)/3,6-(1,2,4,5-dihydrotetrazine))] (PhPTz) as an immobilizing matrix for the CEA antibodies. Judiciously introduced nitrogen-rich semiconducting PhPTz brings multiple advantages to the device—(1) efficiently immobilizes anti-CEA via synergistic H-bonding with peptide and N-glycal units and (2) transports the charge density variations, originated upon antibody-antigen interactions, to the rGO layer. The CEA was dropped onto the anti-CEA/PhPTz/rGO devices at ambient conditions, to facilitate binding and the change in current flowing through the sensors was measured. A response of 2.75–33.7 μA was observed when the devices were tested for a broad range of concentrations (0.25 pg/mL to 800 ng/mL) of CEA. A portable read-out circuit was assembled using Arduino UNO and a voltage divider circuit, and a simple algorithm was developed for the classification of the CEA concentrations. The prediction accuracy of the interfacing electronics along with the algorithm was found to be 100%.
Highlights
Rapid and easy diagnostics of diseases have always been crucial for better treatment and prognosis of any disease
The novel tetrazine polymer-based immobilizing matrix was synthesized by following a two-step synthetic process
The resulting material was subjected to oxidation with aq. NaNO2 to achieve the fully oxidized tetrazine polymer (PhTz)
Summary
Rapid and easy diagnostics of diseases have always been crucial for better treatment and prognosis of any disease. There is resistance among the patients to get themselves tested at an early stage because the current diagnostic methods (computerized tomography scan, bone scan, biopsy, magnetic resonance imaging, positron emission tomography, etc.) are expensive, lab-intensive, and invasive in n ature[6] This prompts for exploring new ways to detect cancer using simple techniques which have the potential to become point-of-care (POC) devices. RGO has functional groups attached to its edges and basal planes It exhibits outstanding properties, including high carrier mobilities which are of interest for developing electronic sensors that capture antibody-antigen interactions[20,21]. This paper reports an end-to-end development of a novel and simple device fabricated using rGO as the base charge transport layer and a novel semiconducting nitrogen-rich tetrazine polymer as an immobilizing matrix for the anti-CEA, owing to the unique ability to develop strong H-bonding interactions with the antibody. The results have been presented and discussed in detail in the subsequent sections
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