3D-printed target plates for high-throughput ambient mass spectrometry analysis of nanoliter biofluids

Ambient mass spectrometry, such as desorption electrospray ionization mass spectrometry (DESI-MS), represent a promising high-throughput platform for biomarkers analysis in biospecimens. However, its application to clinical biomarker analysis in biofluids remains limited by inherent trade-offs among sample preparation complexity, quantitative accuracy, and analytical reproducibility.

In this study, we report, for the first time, the fabrication of a custom-designed target plate, using three-dimensional (3D) printing technology, to enable nanodroplet array preparation for high-throughput DESI-MS analysis. A single square target plate (2 mm × 2 mm) can accommodate 188 discrete 80-nL biofluid droplets, permitting high-throughput biomarker screening in biofluids with DESI-MS. For three clinically relevant renal function biomarkers, creatinine (Cr), urea nitrogen (UN), and uric acid (UA), the limits of detection (LODs) achieved with DESI-MS range from 0.1 to 0.8 μmol/L, an approximately tenfold improvement over conventional colorimetric enzymatic assays routinely employed in clinical laboratories. More critically, DESI-MS analysis of each individual urine or serum sample requires only 6.5 s, substantially shorter than the several minutes typically needed per sample for enzymatic methods. Finally, the feasibility, reliability, and reproducibility of the developed method were demonstrated through quantifying Cr, UN, and UA in serum and urine samples from mice exposed to inorganic mercury (Hg(II)), serving as a proof-of-concept validation.

We anticipate that this robust strategy for biofluid analysis will advance both biomarker discovery and mechanistic studies across clinical medicine, biology, and environmental health science.