Triple bioaffinity mass spectrometry concept for thyroid transporter ligands

Area of Science:

• Analytical Chemistry
• Biochemistry
• Environmental Science

Background:

• Thyroid transporter ligands, including drugs and endocrine-disrupting chemicals (EDCs), require robust analytical methods for detection and characterization.
• Existing methods may lack the sensitivity or specificity needed for comprehensive analysis of these compounds in biological and environmental samples.

Purpose of the Study:

• To develop a versatile triple bioaffinity mass spectrometry (BioMS) concept for analyzing thyroid transporter ligands.
• To enable rapid screening, confirmation of known ligands, and identification of unknown ligands using a single biorecognition element.

Main Methods:

• Development of a radiolabel-free competitive inhibition mass spectrometry (MS) binding assay using recombinant thyroid transport protein (rTTR) and ultrahigh performance liquid chromatography-electrospray ionization-triple-quadrupole-MS (UPLC-QqQ-MS).
• Utilized a stable isotopic thyroid hormone ((13)C(6)-L-thyroxine) as a label, with binding inhibition by potential ligands.
• Employed rTTR for bioaffinity purification and nano-UPLC-quadrupole time-of-flight-MS (nLC-Q-TOF-MS) for identification of unknown ligands in urine samples.

Main Results:

• Demonstrated concentration-dependent inhibition of the (13)C(6)-L-thyroxine label by l-thyroxine (T4) in water (part-per-trillion) and urine (part-per-billion).
• Successfully confirmed naturally present free T4 in urine using rTTR-based bioaffinity purification.
• Identified model unknown EDCs (triclosan, tetrabromobisphenol-A) in spiked urine samples using nLC-Q-TOF-MS.

Conclusions:

• The developed triple BioMS concept offers a powerful and adaptable platform for thyroid ligand analysis.
• This approach facilitates rapid screening, confirmation, and identification of both known and emerging thyroid EDCs.
• The study highlights the potential of using a single affinity system (rTTR) for diverse analytical objectives in complex biological samples.