Accurate Quantification of intact Insulin-like Growth Factor I (IGF-I) using High Resolution Mass Spectrometry (HRMS) for Clinical Research

Significance of the Topic

The accurate measurement of insulin-like growth factor I in biological samples is critical for clinical research and therapeutic monitoring. Methods that maintain protein integrity while offering high selectivity and sensitivity enable more reliable biomarker studies and drug development efforts.

Objectives and Study Overview

The goal of this work was to demonstrate a streamlined workflow for quantifying intact IGF-I in plasma using high resolution mass spectrometry. The study compares performance metrics against established triple quadrupole systems and highlights the practicality of direct protein analysis without enzymatic digestion.

Methodology and Sample Preparation

A simple sample preparation protocol based on mixed-mode solid phase extraction was applied to isolate IGF-I from mouse plasma. Analytical-scale liquid chromatography was coupled to a time-of-flight mass spectrometer using targeted ToF MRM transitions of the +7 precursor ion. Mass tolerance optimization was performed to enhance specificity and signal intensity.

Instrumentation

• Xevo G2-XS QTof high resolution mass spectrometer
• Analytical scale liquid chromatography system
• Mixed-mode solid phase extraction cartridges

Main Results and Discussion

Optimizing the mass tolerance at ±0.050 Da for the 1093.716 m/z precursor minimized background interference and maximized peak area. Calibration curves in neat solution (0.5–1000 ng/mL) and plasma (10–1000 ng/mL) exhibited linearity (r2 >0.99) with mean accuracies above 100% and coefficients of variation below 10%. Quality control samples across multiple concentration levels showed robust precision and accuracy comparable to a triple quadrupole platform.

Benefits and Practical Applications

• Direct quantification of intact proteins without digestion simplifies workflow
• High resolution mass accuracy improves selectivity in complex matrices
• Wide dynamic range supports multiplexed biomarker analysis
• Comparable sensitivity and robustness to tandem quadrupole instruments

Future Trends and Potential Applications

Advances in high resolution instrumentation and data processing are expected to further enhance the throughput and multiplexing capabilities of intact protein quantification. Emerging clinical and biopharmaceutical applications may include targeted proteomics for personalized medicine and quality control in biologics manufacturing.

Conclusion

High resolution mass spectrometry provides a viable and efficient alternative to traditional triple quadrupole methods for intact IGF-I quantification. The demonstrated workflow achieves the sensitivity, accuracy, and precision required for clinical research applications while preserving protein integrity.

Reference

• Waters Application Note 720006097EN
• Waters Technology Brief 720006167EN