# Continuous Optical Biosensing of IL-8 Cancer Biomarker Using a Multimodal Platform

## TL;DR

This paper introduces a portable optical biosensor for continuously detecting the IL-8 cancer biomarker, offering a fast and non-invasive method for cancer prognosis and therapy evaluation.

## Contribution

The novel contribution is a compact, multimodal biosensing platform that enables rapid, label-free IL-8 detection using resonant nanopillar transducers integrated into a microfluidic system.

## Key findings

- The biosensor successfully detected IL-8 with a sensogram showing anti-IL-8 immobilization and specific recognition.
- The device is suitable for in-line sensing in organ-on-a-chip systems and offers potential for high-throughput screening of multiple biomarkers.
- The system provides a non-invasive alternative to traditional cancer diagnostic methods like imaging and immunohistology.

## Abstract

In this work, we used a label-free biosensor that provides optical readouts to perform continuous detection of human interleukin 8 (IL-8), which is especially overexpressed in certain cancers and, thus, could be an effective biomarker for cancer prognosis estimation and therapy evaluation. For this purpose, we engineered a compact, portable, and easy-to-assemble biosensing module device. It combines a fluidic chip for reagent flow, a biosensing chip for signal transduction, and an optical readout head based on fiber optics in a single module. The biosensing chip is based on independent arrays of resonant nanopillar transducer (RNP) networks. We integrated the biosensing chip with the RNPs facing down in a simple and rapidly fabricated polydimethyl siloxane (PDMS) microfluidic chip, with inlet and outlet channels for the sample flowing through the RNPs. The RNPs were vertically oriented from the backside through an optical fiber mounted on a holder head fabricated ad hoc on polytetrafluoroethylene (PTFE). The optical fiber was connected to a visible spectrometer for optical response analysis and consecutive biomolecule detection. We obtained a sensogram showing anti-IL-8 immobilization and the specific recognition of IL-8. This unique portable and easy-to-handle module can be used for biomolecule detection within minutes and is particularly suitable for in-line sensing of physiological and biomimetic organ-on-a-chip systems. Cancer biomarkers’ continuous monitoring arises as an efficient and non-invasive alternative to classical tools (imaging, immunohistology) for determining clinical prognostic factors and therapeutic responses to anticancer drugs. In addition, the multiplexed layout of the optical transducers and the simplicity of the monolithic sensing module yield potential high-throughput screening of a combination of different biomarkers, which, together with other medical exams (such as imaging and/or patient history), could become a cutting-edge technology for further and more accurate diagnosis and prediction of cancer and similar diseases.