Rapid And Sensitive Detection Of Procalcitonin Using Upconversion Nanoparticles NaYF₄:Yb³⁺,Er³⁺-based Immunochromatography Test Strip

Procalcitonin?PCT?,a precursor protein of calcitonin,is a glycoprotein without hormone activity.It is a protein of 116 amino-acids,with molecular weight of 14 kD,mainly produced by C cells of the thyroid gland.Serum PCT is normally undetectable?<0.05ng/ml?,but is increased sharply in the plasma of patients with sepsis and infection,produced by extra extra-thyroidal tissues.The Sepsis is a common critically ill.About 1.8 million cases of severe sepsis happened every year globally.Sepsis is a disease with a fast onset and a high mortality rate.Once developed to sepsis shock,the mortality rate can reach 80%.In sepsis,serum PCT is increase significantly within 2-3 h,the concentration and severity of inflammation is positively correlated.After nearly 20 years of research,PCT has been recommended for the diagnosis,stratification,treatment monitoring and prognostic assessment of bacterial infection with sepsis.So specific and homogeneous detection of PCT is of great importance for early and accurate diagnosis of sepsis.It can also help doctors to monitor the progress of the disease in time to prevent sepsis shock,multiple organ dysfunction syndrome?MODS?and other complications happened,to reduce mortality.In this work,we used up-converting phosphor nanoparticle?UCNP?as immunochromatographic strip signal probe and established a quantitative detection model based on the ratio of T/C for detection of PCT.The approach was based on a sandwich immunoassay fashion.UCNP(NaYF₄:Yb³⁺,Er³⁺)in this work were synthesized by solvothermal method.The silica coated NaYF₄:Yb³⁺,Er³⁺ UCNPs were synthesized by reverse microemulsion method,and further fabricated with epoxy groups,applied by 3-?glycidyloxypropyl?trimethoxysilane?GPTMS?,to covalent binding to monoclonal antibody JG03 without activation.The optimized conditions for immunochromatographic reaction were as follows: 0.07 mol/L sodium borate buffer,15 mg of labeled antibody,1 mL/cm of immune complex?UCNP-JG03?,0.3 mg/m L of capture antibody JG05 dispensed on the NC membrane as test line and 10 min of detection time.The regression equation could be represented by y=0.2594x+2.1991?R2=0.9862?in 0.05-40 ng/m L of PCT,where y was the ratio of signal-to-background and x was the PCT concentration in PBS.The limit detection for the fluorescent strip was 0.02 ng/m L.Recoveries of PCT in human serum sample ranged from 96% to 102.7%,and the coefficient of variation?CVs?in intra-assay and inter-assay were below 10% and 15% respectively.Upconversion nanoparticles NaYF₄:Yb³⁺,Er³⁺-based immunochromatography test strip is a rapid and sensitive method for quantitative detection of PCT in serum.