Efficient red-emitting carbon dots and albumin composites for precise synovial bioimaging in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that frequently leads to significant disabilities and requires complex therapeutic strategies. Early detection and accurate monitoring of synovial lesions are crucial for effective treatment; however, the development of targeted imaging probes remains a significant challenge. Secreted protein acidic and rich in cysteine (SPARC) is overexpressed in the synovium and the concentration of serum albumin is lower in RA patients. Inspired by this, we developed a novel bioimaging strategy for monitoring RA progression by constructing a 100 nm red-fluorescent nanoprobe (CDs@BSA) through electrostatic conjugation of carbon dots (CDs) with bovine serum albumin (BSA). The interaction between BSA and SPARC facilitates precise targeting of RA lesion sites, improving imaging accuracy. The probe demonstrated rapid imaging capabilities, with signal initiation within 1 h and sustained for at least 24 h, enabling the real-time monitoring of disease progression. This work introduces a straightforward approach for designing diagnostic probes using carbon-based nanomaterials, emphasizing their potential for high-resolution, synovial-targeted photoluminescence imaging in RA.