Summary

Quantitating ultra‐low concentrations of protein biomarkers is critical for early disease diagnosis and treatment. However, most current point‐of‐care (POC) assays are limited in sensitivity. This paper introduces an ultra‐sensitive and facile microbubbling assay for the quantification of protein biomarkers with a digital‐readout method that requires only a smartphone camera.

The Wang Lab developed and validated a novel and simple platform for measuring femtomolar concentrations of proteins, which is traditionally only achievable with large and expensive research instruments. The platform uses microbubbles generated in platinum nanoparticle-catalyzed chemistry reactions to “visualize” target molecules. The concentration of the target molecules is read directly using a simple smartphone camera coupled with a machine-learning-based app to count the microbubbles. The platform may find many applications, especially where rapid and ultra-sensitive biomarker measurement is needed. Two applications were demonstrated using PSA and βhCG. Sensitive and convenient measurement of PSA at home or in the clinic helps patients detect early cancer recurrence after prostatectomy. Rapid and sensitive measurement of βhCG is essential for rule-in or rule-out of early pregnancy, especially in emergency settings before diagnostic radiography procedures.