Cell Tracking with Caged Xenon: Using Cryptophanes as MRI Reporters upon Cellular Internalization

Abstract

Caged xenon has great potential in overcoming sensitivity limitations for solution-state NMR detection of dilute molecules. However, no application of such a system as a magnetic resonance imaging (MRI) contrast agent has yet been performed with live cells. We demonstrate MRI localization of cells labeled with caged xenon in a packed-bed bioreactor working under perfusion with hyperpolarized-xenon-saturated medium. Xenon hosts enable NMR/MRI experiments with switchable contrast and selectivity for cell-associated versus unbound cages. We present MR images with 10(3) -fold sensitivity enhancement for cell-internalized, dual-mode (fluorescence/MRI) xenon hosts at low micromolar concentrations. Our results illustrate the capability of functionalized xenon to act as a highly sensitive cell tracer for MRI detection even without signal averaging. The method will bridge the challenging gap for translation to in vivo studies for the optimization of targeted biosensors and their multiplexing applications.

A “Smart” 129Xe NMR Biosensor for pH-Dependent Cell Labeling

“…43 Most recently, Klippel et al performed hp 129 Xe chemical exchange saturation transfer (Hyper-CEST) NMR spectroscopy and imaging studies in cells loaded with lipophilic cryptophane and found a similar 9-11 ppm downfield chemical shift change, likely due to membrane association. 44-46 These studies highlight the large 129 Xe NMR chemical shift changes that can be achieved by engineering cryptophane-lipid membrane interactions.…”

Magnetic resonance imaging with hyperpolarized agents: methods and applications

“…The potential applications of the technique have expanded to include in vitro labeling of cells and cell lysates. Klippel et al demonstrated the ability to discriminate between cells labeled with cryptophane-A 129 Xe hosts and unlabeled cells [226], highlighting the potential of HP 129 Xe hyper-CEST MRI for cell tracking. The ability to distinguish specific cell types based on their surface receptors has also been experimentally tested in vitro for cells expressing surface proteins such as cluster of differentiation 14 (CD14) [227], cells exhibiting metabolically labeled cell-surface glycans [228], and lymphoma cells targeted by specific DNA aptamers attached to MS2 viral capsids enclosing cryptophane-A host molecules [229].…”

Xenon‐MRT an lebenden Zellen mit Hyper‐CEST‐Biosensoren für metabolisch markierte Glykane an der Zelloberfläche

“…Weiterhin untersuchten wir den Einfluss von CrA und BCN auf die Spezifität des Biosensors, da beide Einheiten als Ursache unspezifischer Bindung bekannt sind. [26,31] Die Konjugate 2-4 (Abbildung 2 a) wurden analog zu 1 synthetisiert, nämlich unter Auslassen von BCN (2), CrA (3) oder beiden (4). Jede der funktionalen Einheiten erhçht demnach die unspezifische Bindung geringfügig (Abbildung 2 c).…”

“…Diese Ergebnisse wurden dann mit unserem zuvor entwickelten Bioreaktor [31] für MRT mit lebenden Zellen (Abbildung 4) bestätigt. Eine Anlieferung von Medium, das vorab mit hyperpolarisiertem Xenon gesättigt wurde (Abbildung 4 a) gewähr-leistet eine hohe Viabilität der Zellen über die Messung hinweg und simuliert gleichzeitig zu einem gewissen Grad die Anlieferung von Xenon in lebendem Gewebe.…”