Diagnosis of albuminuria by tryptic digestion and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry

BackgroundMatrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry has been successfully used to detect trace albumin in urine for the diagnosis of albuminuria. However, only the monomeric form of albumin was detected with this approach.MethodsTrypsin was used to digest urinary albumin and its related compounds in urine to produce characteristic peptides. The digest solution was subsequently analyzed by MALDI-TOF MS to obtain peptide ion signals which were used as diagnostic biomarkers for albuminuria.ResultsThe analytical protocol was optimized for efficient digestion and high-performance MALDI-TOF MS analysis. The limit of detection (LOD) of albumin in urine was about 5 × 10− 7 M.ConclusionsTrypsin digestion combined with MALDI-TOF MS analysis is an efficient and simple approach for rapidly diagnosing albuminuria.

► Trypsin was used to digest albumin in urine to produce characteristic peptides.
► The digest solution was subsequently analyzed by MALDI-TOF/MS.
► Peptide ion signals were used as diagnostic biomarkers for albuminuria.
► The LOD of albumin in this approach reached the microalbuminuria range.