Lab-on-Pipet-Tips: A Low-Cost Photothermal Immunosensing Platform for On-Site Testing of Acute Brain Injuries

The preclinical window for acute brain injury is characterized by its considerable narrowness, thus necessitating the development of clinical evaluation methods that are both highly efficient and sensitive. Herein, we constructed a highly miniaturized photothermal immunoassay platform integrated onto a pipet tip for on-site detection of the central nervous system-specific protein S100β. Signal amplification was performed using a liposome-embedded CuS nano-octahedral framework (CuS NOFs). The template-synthesized CuS NOFs demonstrated a high photothermal conversion efficiency (30.2%). Chitosan gel served as the sensitization and immobilization matrix, functionalizing the inner wall of pipet-compatible tips with capture probes for signal transduction in the presence of targets. The developed photothermal assay protocol based on pipet tips satisfied the specificity requirements for S100β in blood samples and enables rapid and low-cost (1.0 $ per test) testing across an ultrawide range of 0.05-500 ng·mL^-1. Using 3D printing technology, all components were fabricated and integrated, including a pipet, a support platform, a smartphone, a near-infrared laser, and a dedicated sample chamber. This work provides novel insights for developing rapid point-of-care photothermal immunoassays for acute brain injury.