A Comprehensive Workflow for Plasma Proteomics by Mass Spectrometry: A Strategy for Biomarker Discovery in Systemic Human Diseases

Summary

Plasma proteomics enables biomarker discovery for systemic diseases through minimally invasive sampling. Despite analytical challenges posed by plasma complexity, this study presents an optimized liquid chromatography-mass spectrometry (LC-MS/MS) workflow that enhances proteome coverage, reduces variability, and improves reproducibility, enabling accurate comparisons between disease and control samples.

Abstract

Plasma, the cell-free component of blood, offers a minimally invasive and rich source of biomolecular information, making it ideal for investigating systemic diseases. The advent of high-throughput proteomic technologies has revolutionized plasma analysis by enabling large-scale identification and quantification of circulating proteins. These advances have facilitated biomarker discovery for early diagnosis, prognosis, and therapeutic targeting of various disorders, including cancers and inflammatory diseases. However, the inherent complexity of plasma, along with inconsistent sample preparation and analysis methods, has historically limited proteome coverage and reproducibility. Early approaches relying on crude plasma analysis often suffered from poor consistency and significant batch effects, impeding reliable comparative studies across clinical cohorts.

To overcome these limitations, the current study introduces a robust and scalable plasma proteomics workflow. The protocol integrates key preparatory steps such as immunodepletion, molecular weight cutoff filtration, lyophilization, protein quantification and normalization, enzymatic digestion, and LC-MS/MS profiling. This optimized strategy significantly enhances proteome depth and reduces variability, thereby enabling more accurate and reproducible differential protein expression analysis between disease cases and healthy controls. The workflow provides a valuable platform for researchers aiming to generate high-quality proteomic data from plasma, ultimately contributing to the advancement of biomarker-driven diagnostics and personalized medicine.

Introduction

Plasma, the cell-free component of blood, is gaining increasing recognition as a reservoir of biological information relevant for disease studies. It carries a plethora of diverse circulating biomolecules, ranging from proteins and metabolites to lipids and nucleic acids, which is a mirror of the organism's physiological and pathological status. This systemic nature of plasma makes it an ideal biospecimen for investigation into disease pathophysiology, ranging from cancer to metabolic and inflammatory disorders. A major benefit of using plasma as a sample lies in its minimally invasive collection method, allowing for repeated sampling in clinical settings, which i....

Protocol

This protocol outlines a streamlined workflow designed to enhance plasma proteomics for biomarker discovery in systemic inflammatory diseases^14,15. The study was done in accordance with the Institutional Ethics Committee and the Helsinki Declaration of 1975, as revised in 2000. Informed consent was obtained from the participants. Initially, plasma samples undergo immunodepletion to remove high-abundance proteins, followed by molecular weight-based filtration to reduce sample complexity. The samples are then lyophilized and quantified to ensure protein concentration is adequate for downstream processing. After ....

Results

Plasma samples were processed using a spin cartridge to selectively remove 14 high-abundance proteins, namely albumin, IgG, IgA, transferrin, haptoglobin, antitrypsin, fibrinogen, alpha2-macroglobulin, alpha1-acid glycoprotein, IgM, apolipoprotein AI, apolipoprotein AII, complement C3, and transthyretin. This depletion step was critical to enhance the detection of low-abundance biomarkers in downstream proteomic analysis. Each plasma sample (8-10 µL) was diluted, clarified via 0.22 µm spin filtration, and passed through .......

Discussion

The intrinsic complexity of plasma as a biological matrix presents a major challenge to proteomic analysis. The enormous dynamic range of protein concentrations, along with the predominance of a few high-abundance species, can mask the detection of clinically relevant lower-abundance proteins. For this current study, we mitigated these disadvantages utilizing a multi-step, standardized pipeline for sample preparation that was designed to selectively enrich moderate- and low-abundance proteins and to maintain analytical c.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
5 kDa Molecular Weight Cutoff Spin Concentrator	Agilent Technologies	5185−5991	Used for buffer exchange and salt removal; retains proteins above 5 kDa
Ammonium Bicarbonate (ABC)	Sigma Aldrich	Cat no: T6567	Used for Tryptic digestion
Buffer A Equil/Load/Wash	Agilent Technologies	5185-5987
Buffer B Elution	Agilent Technologies	5185-5988
Cool centrifuge	CPR-30 Plus Refrigerated Centrifuge	N/A	Used for centrifuging protein samples at low temperature
DTT	Sigma Aldrich	CASNo: 3483-12-3	Used for Tryptic digestion
Electrophoretic apparatus	BIO RAD	1658004	Used for SDS PAGE
IAA	Sigma Aldrich	CAS No: 144-48-9	Used for Tryptic digestion
IMS T-Wave	Waters	https://www.waters.com/content/dam/waters/en/library/white-papers/2012/water-whitepapers-Triwav eMoreCompleteCharacterizationofMi xturesandMolecules-720004176.pdf	Ion mobility separation (IMS)
Infinite M Plex Multi mode reader	TECAN		Multiplate reader
LC-MS system	Waters	https://www.waters.com/nextgen/us/en/products/mass-spectrometry/mass-spectrometry-systems/liquid-chromatography-ms-systems.html
MassLynx 4.1 SCN781 software	Waters	https://www.waters.com/nextgen/us/en/products/informatics-and-software/mass-spectrometry-software/masslynx-mass-spectrometry-software.html	Mass spectrometry software
Multiple Affinity Removal Spin Cartridge Human 14 (MARS Hu-14)	Agilent Technologies	5188−6560	Used to deplete 14 high-abundance plasma proteins including albumin, IgG, IgA, transferrin, etc.
nanoACQUITY UPLC system	Waters	https://www.waters.com/nextgen/en/products/chromatography/chromatography-systems/acquity-uplc-m-class-system.html
NanoLockSpray	Waters	https://www.waters.com/nextgen/us/en/services/instrument-services/instrument-upgrades/mass-spectrometry-ms-upgrades/nanolockspray-exact-mass-ionization-source-upgrade.html
Operon FDU-7003	Operon	http://www.operon.co.kr/en/pro2-FDU.html	speed vacuum lyophilizer
Pierce BCA protein assay kit	Thermo Scientific	23225	Used to quantify protein concentration using colorimetric assay
Progenesis QI for Proteomics	Waters	V4.2
R-8C BL Laboratory centrifuge, fixed-angle rotor with 12 × 15 mL	REMI		Centrifuge
SYNAPT G2 high-definition MS	HDMSE System, Waters Corporation	https://www.waters.com/content/dam/waters/en/app-notes/2009/720003057/720003057-en.pdf	Hybrid quadrupole IMS orthogonal acceleration time-of-flight (oa-Tof) mass spectrometer
Total recovery vial	Waters	https://www.waters.com/nextgen/us/en/shop/vials-containers--collection-plates/186004631-clear-glass-12-x-32-mm-screw-neck-total-recovery-vial-preassembl.html
Trypsin	Sigma Aldrich	Cat no: T6567	Used for Tryptic digestion