Non-invasive diagnosis of lupus nephritis based on dual-mode optical fiber biosensor.

Lupus nephritis (LN) is the most common and severe complication of systemic lupus erythematosus (SLE), which requires the use of renal biopsy techniques to determine the pathological type and guide subsequent treatment. Recent studies have identified neutrophil gelatinase associated lipocalin (NGAL) as a promising biomarker for the non-invasive diagnosis, assessment of disease activity, and prediction of recurrence in lupus nephritis. However, current single-signal detection methods based on NGAL lack sufficient specificity and accuracy. In this paper, we reported a novel dual-mode optical fiber biosensor based on microfiber Bragg gratings (μFBG) and surface-enhanced Raman spectroscopy (SERS) for the detection of NGAL. In this sensor, the refractive index change data and Raman spectral data are independently measured and cross-validated, ensuring reliable and accurate analysis. The limits of detection (LOD) of the two modal sensors are 0.49 pg/ml (μFBG) and 48.44 pg/ml (SERS) within the concentration range of 0.01 ng/ml to 1000 ng/ml, respectively. More importantly, the AUC value for clinical samples is significantly improved by utilizing the two modal sensing paradigm. The proposed sensor is particularly suitable for regions with limited medical resources and provides strong support for early diagnosis of lupus nephritis and precise treatment strategies.