CTSB and Crohn disease: The limit of detection and binding affinity values of the peptide-on-a-AuNPs/MXene sensor interface were two to four times lower than those of the two other sensors, indicating that the peptide-on-a-AuNPs/MXene sensor is more specific for cathepsin B (good recovery (86–102%) and %RSD (< 11%) with clinical samples, and can distinguish different stages of Crohn’s disease.