Abstract
Programmed death ligand-1 (PD-L1) plays an important role in tumor evasion from the host immune system. The level of soluble PD-L1 (sPD-L1) in serum is closely related to tumor aggressiveness and outcomes. This study aimed to propose a localized surface Plasmon resonance (LSPR) biosensor based on excessively tilted fiber grating (ExTFG) coated with large-sized (∼160 nm) gold nanoshells for label-free and specific detection of sPD-L1. The experimental results showed that the limit of detection (LOD) of the immunosensor for sPD-L1 in buffer solutions was ∼1 pg/mL due to the enhanced LSPR effect resulting from the interaction between sPD-L1 molecules and anti-sPD-L1 monoclonal antibodies. The detection of sPD-L1 in complex serum media, such as fetal bovine serum, confirmed that the label-free immunosensor was extremely specific to sPD-L1 and could identify it at a concentration as low as 5 pg/mL. Therefore, it can be potentially applied in clinic for the fast and early diagnosis of cancer.
Highlights
Cancer has become a serious threat to human life
The transmission spectra of an excessively tilted fiber grating (ExTFG) in water before and after gold-nanoshell immobilization were compared to investigate the spectral properties of the ExTFG-localized surface Plasmon resonance (LSPR) sensor
This study presented a large-sized gold-nanoshell (∼160 nm)-immobilized ExTFG-LSPR biosensing platform
Summary
Cancer has become a serious threat to human life. The survival rate is still low, and, reliable biomarkers to help the early diagnosis, prevention, and treatment of cancer urgently need to be identified [1]. PD-1 is an immunoglobulin superfamily type I transmembrane glycoprotein consisting of 288 amino acids It is expressed on different immune cells, especially T cells. The soluble PD-L1 (sPD-L1) is released from PD-L1-positive cells. The overall survival was very poor in patients with a higher level of initial sPD-L1 (1.315 pg/mL). A higher level of sPD-L1 after 1 month (>12.9 pg/mL) was significantly related to early lung metastasis. A higher level of sPD-L1 might be associated with the prognosis of malignancies, including lung cancer [5], multiple myeloma [6], extranodal natural killer/T-cell lymphoma [7]. The level of sPD-L1 is associated with tumor aggressiveness and outcomes, suggesting its role as a possible predictive biomarker [8]
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