A Simple 3D-Printed Enzyme Reactor Paper Spray Mass Spectrometry Platform for Detecting BuChE Activity in Human Serum

To achieve personalized healthcare, a quick, accurate, and high-throughput method to detect disease biomarkers is essential. In the traditional practice, mass spectrometry is one of the most powerful tools and is widely studied. However, the test of human serum usually requires complicated sample pretreatment, tedious operations, and precise condition control, especially for the detection of enzymes as biomarkers. As butyrylcholinesterase (BuChE) has an indicative significance in detecting degenerative disease, liver injury, and organophosphate poisoning, the quick quantification of BuChE is of vital importance to the clinic. In this paper, we report the design and fabrication of a portable 3D-printed enzyme reactor paper spray cartridge (3D ER-PS) with integrated functions: temperature control, enzyme reaction, analyte transfer, and paper spray ionization. Coupled with mass spectrometry, quantitative testing of BuChE activity in human serum was realized conveniently and accurately. While it only requires very simple sample preparation, the results from current 3D ER-PS approach are well consistent with those obtained using Ellman's method. This 3D ER-PS platform not only provides a novel solution for the liquid biopsy of BuChE in clinics but also contributes to the development of quick and targeted medical approaches for analyzing other types of serum biomarker molecules in the field of disease diagnosis.