A facile plasmonic silver needle for fluorescence-enhanced detection of tumor markers

Tumor markers have been regularly detected for early cancer diagnosis in clinical oncology. The development of facile and low cost technology has become an important challenge for their diagnosis. We here report a low-cost plasmonic silver needle (PSN) for immunofluorescence detection of tumor biomarkers. The fluorescence signal is enhanced on the needle by up to 220-fold, allowing high-performance detection of tumor markers down to 0.08 ng mL^-1. To assess the clinical potential of the proposed assay technique, PSN-based sandwich immunoassay for the detection of alpha-fetoprotein and carcinoembryonic antigen were performed for blood as well as for serum sample. The results from serum sample have an excellent agreement with an electrochemluminecence assay. The small relative error and a good linear correlation suggest that the accuracy and precision of this analytical technology are satisfactory. This assay technique with lower cost, use of less sample, higher sensitivity and easier procedure shows great promise for the facile and early cancer diagnosis.