Development and evaluation of an immuno-MALDI (iMALDI) assay for angiotensin I and the diagnosis of secondary hypertension

Abstract

Plasma renin activity (PRA) is an essential analytical tool for screening and diagnosis of secondary forms of hypertension. Typically, PRA is measured by competitive radioimmunoassay, but there are significant drawbacks to this technique including non-specificity, long analysis times, narrow calibration range, and the requirement for radionucleotides. In this paper, we report a method for plasma renin activity determination by immuno-MALDI mass spectrometry detection. This method overcomes the issues of non-specificity and long analytical times present with RIA, and does not require the use of radionucleotides. As an initial methodological evaluation, plasma renin activity results obtained by radioimmunoassay, LC/ESI-MS/MS, and immuno-MALDI on 64 samples from an outpatient primary aldosteronism screening program have been compared. A strong correlation was found between immuno-MALDI and radioimmunoassay (R2 = 0.9412, 62/64 within the 95% CI of the Bland-Altman plot), and iMALDI and LC/ESI-MS/MS (R2 = 0.9471, 62/64 within the 95% CI of the Bland-Altman plot). Technical replicates showed a 4.8% CV, while inter- and intra-day replicates showed CVs of 17.3% and 17.2% respectively. We have developed an assay capable of measuring PRA without the use of radionucleotides. This immuno-MALDI approach affords the specificity of MS while avoiding the long analytical run times and technical problems associated with HPLC. With the use of robotic sample preparation to optimize precision, this assay should be adaptable to clinical environments.

Immune-enrichment of insulin in bio-fluids on gold-nanoparticle decorated target plate and in situ detection by MALDI MS

“…Therefore, several immune-MALDI MS methods have been developed to pre-concentrate target analytes and increase analyzing efficiency. These methods generally applied immune-affinity column [20] or antibody-conjugated magnetic beads [21, 22] to capture target biomolecules, followed by MALDI MS analysis. However, these strategies required additional steps of centrifugation, sample transferring, or column-fractions, which increased sample consumption and limited the analysis throughput [13].…”

MALDI-TOF MS in the Microbiology Laboratory: Current Trends

“…For these labelled peptides a calibration curve has to be established. Development of methods to quantify hypertension markers has already been described (Reid et al, 2010;Camenzind et al, 2013). Applications of this technology to solve microbiology-related problems, e.g.…”

Biomarker Characterization by MALDI–TOF/MS

“…MS/MS analyses were also performed to provide sequence information for accurate determination of angiotensin I. A calibration curve obtained by this approach had over a 50-fold linear range in plasma [253,254]. Another application of immuno-MALDI-TOF/MS is for the detection of beta amyloid peptides in serum.…”

“…Immuno-MALDI has been used to determine angiotensin I, an indicator of plasma renin activity, with a stable isotopically labeled antibody for quantification [253,254]. The antibodies were bound to small beads for easy manipulation.…”