Towards microfluidics assisted optical fiber metatip biosensors

The importance of biosensors based on optical fiber (OF) technology is increasing due to their high sensitivity and compatibility with minimally invasive real-time diagnostics and enormous potentials for in vivo biopsies. This study investigates the technical aspects behind integrating Lab-on-Tip optrodes within microfluidic channels, which is propaedeutic for guidelines setting towards their correct connection with minimally invasive clinical tools such as needles, catheters and nanoendoscopes. Here, as proof of concept, we investigated the integration of a plasmonic Metasurface-assisted Lab-on-Tip optrode, realized onto a single mode OF tip (OFMT), into a T-shaped microfluidic chip for the detection of a clinically relevant target molecule as the breast cancer biomarker receptor tyrosine protein kinase (ErbB2). The biosensor response to different ErbB2 concentrations (1–1000 ng/mL) was analyzed under controlled flow conditions. Experiments demonstrated a strong dependence of the detection performance on the probe position within the microfluidic channel, with increased performance frustration as the distance of the tip from the center is reduced. These findings, confirmed by numerical modeling, revealed an inverse relationship between the flow velocity and the biosensor performance. This relationship was further corroborated by additional experiments demonstrating that higher flow rates reduce the target molecule capability to correctly recognize the bioreceptor immobilized on the sensor surface due to the shorter analyte-probe interaction time. In summary, the present study highlights the importance of a multi-aspect microfluidics design considering local flow conditions for optimal probe placement, providing valuable guidelines for improving detection capabilities of microfluidic assisted Lab-on-Tip biosensing platforms for biomedical applications.