Electrochemical Biosensor for Rapid Detection of Acute Rejection in Kidney Transplants

Kidney transplant recipients face a high risk of acute rejection (AR), where the immune system attacks the transplanted organ. Current diagnostics rely on invasive biopsies with procedural risks, costs, and limited temporal resolution. While urinary chemokines CXCL9 and CXCL10 are promising non-invasive AR biomarkers, clinical adoption is limited by labor-intensive detection and lack of point-of-care (POC) solutions. A rapid, label-free electrochemical biosensing platform for simultaneous quantification of CXCL9 and CXCL10 chemokines from 5 µL of unprocessed urine in 15 min, which for ELISA and biopsy is between 24-72 hrs, is presented. The system uses screen-printed carbon electrodes modified with a Ti₃C₂T_x MXene-crosslinked bovine serum albumin hydrogel, offering high conductivity, nano-porosity, anti-fouling properties, and signal stability for up to 30 days. The platform enables single-digit pg/mL-level sensitivity, meeting clinical thresholds. In a prospective clinical study, biosensor-measured chemokine data trained a bootstrapped logistic regression classifier, achieving 83% AR classification accuracy. When combined with additional clinical and histopathological features, accuracy increased to 98%. This work integrates advanced materials, biosensor engineering, and machine learning to deliver a scalable, cost-effective POC solution for real-time, non-invasive AR monitoring. The platform will help reduce biopsy dependence, enable earlier intervention, and ultimately improve long-term transplant outcomes.