Detection of C-Reactive Protein in Serum with Near-Infrared Fluorescent Sensors

The human immune system is central in the defense against pathogens but is also involved in autoimmune diseases. Inflammatory processes are orchestrated by biomolecules, including the inflammation marker C-reactive protein (CRP), for which fast point-of-care diagnostics are desired. Single-walled carbon nanotubes (SWCNTs) exhibit fluorescence in the beneficial near-infrared (NIR) tissue-transparency window, making them ideal building blocks for biosensors. Here, we demonstrate that SWCNTs modified with certain phospholipids are highly sensitive sensors for CRP. We synthesize n-hexadecylphosphocholine (HPC)-modified SWCNTs (HPC-SWCNTs) (emission at 995 nm) and characterize their stability and sensitivity to CRP. In human serum samples, HPC-SWCNT sensors respond to CRP with a fluorescence change of up to 15 % within < 20 min and a detection limit of < 13 mg/L, which enables identification of inflammation above the base level. These nanosensors can be read out with a low-footprint point-of-care optical setup. Thus, we demonstrate fast CRP detection in serum using nanosensors with a high potential for integration into multiplexed diagnostic tools.