A sensitive and quantitative prognosis of C-reactive protein at picogram level using mesoporous silica encapsulated core-shell up-conversion nanoparticle based lateral flow strip assay.

C- reactive protein (CRP) is a sensitive indicator for infectious or inflammatory diseases in human which can reflect the body's inflammation latency and early pathophysiological changes. The most common detection method of serum CRP is ELISA that has been proved to be expensive and time-consuming, restricting its use in point-of-care application. In this paper, we demonstrated a lateral flow system for CRP quantification by using mesoporous silica (mSiO) coated up-converting nanoparticles (UCNPs) (denoted as UCNPs@mSiO) as fluorescent labels. The up-converting core can emit strong green fluorescence signals under NIR excitation light (980 nm) with excellent photostability, high signal-to-noise ratio and low background fluorescence. By wrapping ultrathin mSiO outside, the core-shell structured UCNPs@mSiO exhibits good dispersity and stability meanwhile maintains strong fluorescence emission. Besides, the mSiO shell provides further functionalities for antibody linkage. By using a portable fluorescence sensor, we reached a CRP detection limit of 0.05 ng/mL and a linear range from 0.1 ng/mL-50 ng/mL, and the detection time was no more than 8 min. The lateral flow test strips exhibit great stability in CRP quantification (CV%<5) and have a life time of more than 1 week at ambient temperature. Furthermore, the proposed system can work with a cloud-enabled smartphone through Bluetooth for Internet of Medical Things application. This CRP detection method proves to be rapid and easy-operated, which has great potential in early inflammatory disease perception in the point-of-care tests and future's 5G-enabled remote healthcare management.