A label-free fluorescence aptasensor for salivary exosomes based on a nano-micro dual-scale signal amplification strategy

Abstract

Oral squamous cell carcinoma (OSCC) is the most prevalent histological subtype of oral cancer and urgently requires a noninvasive approach for timely detection to improve patients’ prognose. Salivary exosome act as a promising biomarker, while the complex and expensive analytical methods impeded its popularization in clinical applications. In this study, we developed a label-free aptasensor for salivary exosomes that utilizes a “one exosome to multiple carbon dots” signal conversion method along with nano-micro dual-scale signal amplification strategy. SiO₂ microspheres served as substrates, while carbon dots acted as luminophores, with CD63 aptamers functioning as selective recognition elements. Exosomes compete to bind with the aptamers, thereby leading to the release of non-specifically adsorbed carbon dots from the substrates. The concentration of exosomes is proportional to the variation in fluorescence intensity, enabling highly sensitive detection in artificial saliva samples, with a favorable linearity range of 2.5 × 10²∼5 × 10⁸ particles/mL and a relatively low LOD of 100 particles/mL. The anti-interference ability is deemed acceptable, and the fabrication process is affordable coupled with a straightforward signal output mode. The aptasensor was applied successfully to distinguish OSCC patients from healthy individuals, suggesting its potential for screening OSCC in physical examination centers and communities.