Multifunctional nanoparticles for protein detections in thin channels

This paper presents a method for simultaneous detection of two proteins by using multifunctional nanoparticles with a magnetic immunoassay in thin channels. Biofunctional magnetic graphene quantum dots (GQDs) combined with two biofunctional quantum dots (QDs) were used for simultaneously detecting two proteins. Magnetic GQDs enabled selective and quantitative nanoparticle deposition with blue emission. Biofunctional QDs confirmed the two protein detections with orange and green emissions. We used two model biomarkers [alpha-fetoprotein (AFP) and cancer antigen 125 (CA125)] to demonstrate the feasibility of the proposed method. The detection limits (0.06 pg/mL AFP and 0.001 U/mL CA125) and linear ranges (0.2 pg/mL-0.68 ng/mL AFP and 0.003-25 U/mL CA125) of this method are the same as those of single protein detection within experimental errors. These detection limits are substantially lower and the linear ranges are considerably wider than those of enzyme-linked immunosorbent assay (ELISA) and other immunoassay methods. The differences between the proposed method and an ELISA method in AFP and CA125 measurements of serum samples were less than 12%. The proposed method demonstrates favorable detection of biomarkers with advantages of speed, sensitivity, selectivity, and throughput.