Design of NanoBiT-Nanobody-based FGL1 biosensors for early assisted diagnosis of esophageal cancer

Esophageal cancer (EC) is one of the most common causes of cancer-related mortality due in part to challenges in early diagnosis. Biomarker identification is crucial for improved early screening and treatment strategies for patients. Firstly, we employed serum proteomics techniques to screen for potential biomarkers in 15 early-stage EC patients and 5 healthy individuals. Among the differentially expressed proteins, FGL1 emerged as a promising candidate (AUC = 0.974) for early detection of EC. Subsequently, we developed NanoBiT-conjugated dual nanobodies (NBNB) sensors for robust and quantitative signal detection in fetal bovine serum (FBS) in 30 min or less, with a limit of detection (LoD) of 11.38 pM. In a case–control study recruiting 96 EC patients and 99 control samples, testing serum samples with the developed NBNB sensors revealed significantly elevated serum level of FGL1 in all-stage EC patients (AUC = 0.7880) and early-stage EC patients (AUC = 0.8286). Additionally, the combined diagnostic performance of FGL1 and CEA in EC samples is notably enhanced (AUC = 0.8847). These findings propose FGL1 as a novel and promising target for the early-stage EC diagnosis and treatment selection. Furthermore, we applied the assay to patients across six types of cancer, suggesting FGL1 as a potential pan-cancer marker. This study introduces a rapid, easy-to-use, cost-effective, reliable, universal, and high-throughput alternative to meet the growing demand for cancer biomarker testing in both academic and clinical settings.