A Chromium-Based magnetic resonance probe for in situ gastric pH imaging

Effective monitoring of gastric fluid pH is crucial for diagnosing gastric diseases and evaluating anti-gastric-acid therapies. The invasiveness and low patient compliance with traditional gastric fluid aspiration methods highlight the need of a non-invasive, real-time technique for in situ gastric pH monitoring. This study introduces a novel chromium (Cr)-based magnetic resonance probe, Cr(OH) 3 @HSA, specifically designed for pH-sensitive gastric imaging. Synthesized via an albumin-mediated biomimetic mineralization process, Cr(OH) 3 @HSA possesses an amorphous structure that facilitates the sensitive release of paramagnetic Cr(III) ions in acidic environments. This release substantially decreases the longitudinal relaxation time of surrounding hydrogen protons, as demonstrated by an 18.29-fold increase in the longitudinal relaxation rate from pH 6.5 to pH 1.0. In vivo experiments show that Cr(OH) 3 @HSA accurately detects abnormal gastric pH levels and evaluates the efficacy of gastric antiacids, surpassing the performance of the conventional “always-on” contrast agent, Magnevist®. Notably, our research reveals that chromium picolinate, a common dietary supplement for diabetes, generates a “turn-on” signal in the gastrointestinal tract, suggesting potential MR signal interference in diabetic patients. Consequently, we recommend that diabetic patients avoid chromium-based dietary supplements prior to MRI procedures to prevent Cr(III)-induced signal alterations.