Ultrasensitive detection of protein biomarkers by MALDI-TOF mass spectrometry based on ZnFe2O4 nanoparticles and mass tagging signal amplification

Abstract

A facile MALDI-TOF mass spectrometric platform for quantitative analysis of protein biomarkers was developed based on magnetic ZnFe2O4 nanoparticles and mass tagging signal amplification. In this platform, magnetic ZnFe2O4 nanoparticles functionalized with an aptamer of the biomarker of interest was used to magnetically separate silica nanoparticles modified with another aptamer of the target biomarker and a barcoding peptide from solution phase in the presence of the biomarker of interest. After the silica nanoparticles were dissolved by KHF2, the released barcoding peptide was detected by MALDI-TOF mass spectrometry with magnetic ZnFe2O4 nanoparticles used as assisting matrix of laser desorption ionization. Since the mass spectral intensity of the barcoding peptide is directly related to the concentration of the target biomarker, the proposed platform can be applied to the quantification of the target biomarker in complex biological samples. The effectiveness of the proposed platform was tested on the detection of carcinoembryonic antigen (CEA) in serum. Experimental results revealed that the proposed platform could achieve quite reliable quantitative results for CEA in human serum samples with accuracy comparable to a commercial CEA ELISA Kit. Its limit of detection and limit of quantification for CEA were estimated to be 0.6 × 10−3 and 1.8 × 10−3 ng/mL, respectively, considerably lower than the corresponding values reported in literature. Due to its features of simplicity in design, extremely low background signal, high sensitivity and selectivity, the proposed method can be further developed to be a competitive alternative for the quantification of CEA and other protein biomarkers as well.