Surface-enhanced Raman spectroscopy (SERS)-based urine biopsy for kidney transplant patients☆

For kidney transplantation patients, monitoring potential complications such as immune rejection and infection has always been a clinical challenge since the existing detection technology faces difficulties due to limited information, insufficient sensitivity and specificity, and lack of continuous dynamic monitoring ability. Herein, we employed surface-enhanced Raman spectroscopy (SERS) for liquid biopsy, which has non-invasive and highly sensitive characteristics, to assess the physiological status of kidney transplant patients. Two SERS methods were applied to analyze the changes in urine at different stages of renal transplantation. One is a label-free strategy achieved by a SERS substrate with colloidal Ag-assembled film. The other method uses a 4-mercaptopyridine (MPY) probe to obtain the comprehensive information about MPY in response to small metabolic molecules, including carbonyl and hydroxyl groups in urine. Urine samples from kidney transplant patients collected at different time points before and after surgery were measured, and biomarkers related to kidney function and immune status were explored. The machine learning algorithm extracted key features from the massive SERS spectral data and established accurate models to distinguish kidney transplant patients at different surgery stages. This study may help diagnose the immune rejection of kidney transplant patients and provide valuable information about the physiological status of kidney transplant patients during convalescence.