Nanomolar small-molecule detection using a genetically encoded ¹²⁹Xe NMR contrast agent

Area of Science:

• Biophysics
• Molecular Imaging
• Biochemistry

Background:

• Genetically encoded contrast agents offer non-invasive biomarker detection in vivo.
• Hyperpolarized 129Xe Nuclear Magnetic Resonance (NMR) techniques provide sensitive molecular imaging capabilities.

Purpose of the Study:

• To develop and validate genetically encoded, analyte-sensitive molecular imaging agents.
• To quantify maltose using a novel hyper-CEST 129Xe NMR approach with maltose binding protein (MBP).

Main Methods:

• Utilized hyper-CEST 129Xe NMR to monitor xenon exchange with MBP.
• Quantified maltose concentrations ranging from 32 nM to 1 mM.
• Investigated MBP variants, including a Val to Ala mutation, for enhanced contrast properties.

Main Results:

• MBP demonstrated ultrasensitive, "smart" contrast agent properties, with no signal in the absence of maltose.
• Bound 129Xe showed a significant downfield shift (Δδ = 95 ppm), enabling detection in E. coli and multiplexing.
• An MBP mutation enhanced contrast by 34% and shifted 129Xe resonance upfield by 59 ppm.

Conclusions:

• Engineered MBPs represent a new class of genetically encoded, analyte-sensitive molecular imaging agents.
• These agents are detectable by 129Xe NMR/MRI, opening avenues for sensitive biomarker detection.