# Surface Functionalization of ITO for Dual-Mode Hypoxia-Associated Cancer Biomarker Detection

## TL;DR

Researchers developed a new biosensor using ITO to detect a cancer biomarker linked to hypoxia, combining electrochemical and optical methods for improved cancer diagnostics.

## Contribution

A novel ITO-based biosensing platform for dual-mode detection of carbonic anhydrase IX, a hypoxia-associated cancer biomarker.

## Key findings

- ITO surfaces were successfully functionalized to immobilize CA IX-specific antibodies.
- Electrochemical detection achieved a limit of detection of 266.4 ng/mL for CA IX.
- The biosensor demonstrated potential for sensitive and selective cancer biomarker detection.

## Abstract

Indium tin oxide (ITO) is a transparent conducting material with exceptional electrical and optical properties, widely used in biosensing and bioelectronics. Functionalization of ITO with linker molecules enables covalent attachment of biomolecules, allowing for dual-mode optical and electrochemical detection. Carbonic anhydrase IX (CA IX), a transmembrane enzyme overexpressed in hypoxic tumors, is a promising biomarker for cancer diagnostics due to its restricted expression in normal tissues. However, conventional detection methods are time-intensive and unsuitable for point-of-care applications. In this study, ITO surfaces were functionalized using silane-based chemistry to immobilize CA IX-specific antibodies, creating a novel biosensing platform. The biosensor utilized a secondary horseradish peroxidase (HRP)-conjugated antibody to catalyze the oxidation of luminol in the presence of hydrogen peroxide, producing a chemiluminescent and electrochemical signal. Characterization of the biosensor via a dual-mode optical and electrochemical approach revealed efficient antibody immobilization. Due to the high variation observed in the optical approach, limit of detection (LOD) experiments were conducted exclusively with electrochemistry, yielding an LOD of 266.4 ng/mL. These findings demonstrate the potential of ITO-based electrochemical biosensors for sensitive and selective CA IX detection, highlighting their applicability in cancer diagnostics and other biomedical fields.