Sugar‐based biopolymers have been recognized as attractive materials to develop macromolecule‐ and nanoparticle‐based cancer imaging and therapy. However, traditional biopolymer‐based imaging approaches rely on the use of synthetic or isotopic labeling, and because of it, clinical translation often is hindered. Recently, a novel magnetic resonance imaging (MRI) technology, chemical exchange saturation transfer (CEST), has emerged, which allows the exploitation of sugar‐based biopolymers as MRI agents by their hydroxyl protons‐rich nature. In the study, we reviewed recent studies on the topic of CEST MRI detection of sugar‐based biopolymers. The CEST MRI property of each biopolymer was briefly introduced, followed by the pre‐clinical and clinical applications. The findings of these preliminary studies imply the enormous potential of CEST detectable sugar‐based biopolymers in developing highly sensitive and translatable molecular imaging agents and constructing image‐guided biopolymer‐based drug delivery systems.

Sepsis‐induced acute kidney injury (SAKI) is a major complication of kidney disease associated with increased mortality and faster progression. Therefore, the development of imaging biomarkers to detect septic AKI is of great clinical interest. In this study, we aimed to characterize the endogenous chemical exchange saturation transfer (CEST) MRI contrast in the lipopolysaccharide (LPS)‐induced SAKI mouse model and to investigate the use of CEST MRI for detecting such injury. We used a SAKI mouse model that was generated by i.p. injection of 10 mg/kg LPS. The resulting kidney injury was confirmed by the elevation of serum creatinine and histology. MRI assessments were performed 24 h after LPS injection, including CEST MRI at different B₁ strengths (1, 1.8 and 3 μT), T₁mapping, T₂ mapping and conventional magnetization transfer contrast (MTC) MRI. The CEST MRI results were analyzed using Z‐spectra, in which the normalized water signal saturation (S_sat/S₀) is measured as a function of saturation frequency. Substantial decreases in CEST contrast were observed at both 3.5 and − 3.5 ppm frequency offset from water at all B₁ powers, with the most significant difference obtained at a B₁ of 1.8 μT. The average S_sat/S₀ differences between injured and normal kidneys were 0.07 (0.55 ± 0.04 versus 0.62 ± 0.04, P = 0.0028) and 0.07 (0.50 ± 0.04 versus 0.57 ± 0.03, P = 0.0008) for 3.5 and − 3.5 ppm, respectively. In contrast, the T₁ and T₂ relaxation times and MTC contrast in the injured kidneys did not show a significant change compared with the normal control. Our results showed that CEST MRI is more sensitive to the pathological changes in injured kidneys than the changes in T₁, T₂ and MTC effect, indicating its potential clinical utility for molecular imaging of renal diseases.