Quantification of pharmaceutical peptides using selenium as an elemental detection label

Area of Science:

• Biochemistry
• Analytical Chemistry
• Pharmacology

Background:

• Cell-penetrating peptides (CPPs) are crucial for drug delivery.
• Assessing CPP stability and cellular uptake is vital for drug development.
• Current methods may lack precision in quantitative analysis.

Purpose of the Study:

• To demonstrate selenium labeling for evaluating CPP stability and cellular uptake.
• To quantify peptide uptake using inductively coupled plasma mass spectrometry (ICP-MS).
• To assess the fate of synthetic CPPs in cellular environments.

Main Methods:

• Synthesis of two selenium-labeled penetratin analogues (N-PenM(Se) and i-PenM(Se)).
• Purity determination using liquid chromatography (LC)-ICP-MS.
• Cell uptake studies in HeLa WT cells.
• Stability monitoring in various conditions.
• Quantification of total selenium uptake by flow injection (FI)-ICP-MS.
• Speciation analysis by LC-ICP-MS and LC-electrospray ionization mass spectrometry (ESI-MS).

Main Results:

• Peptide purity was determined (92% for N-PenM(Se), 89% for i-PenM(Se)).
• LC-ICP-MS confirmed mainly intact peptide uptake.
• Peptides showed degradation in cell medium and extensive degradation during cell uptake.
• LC-ESI-MS identified major degradation products.
• FI-ICP-MS enabled total selenium uptake quantification.

Conclusions:

• Selenium labeling combined with ICP-MS techniques provides detailed insights into CPP fate.
• The method facilitates early-stage assessment of drug delivery candidates.
• This approach enhances the critical evaluation of synthetic peptide-based therapeutics.