Glutathione capped gold nanoparticles-based fluorescent biosensor for dual detection of albumin and creatinine

Abstract

The ratio of urine albumin-to-creatinine (UACR) is an essential parameter for evaluating kidney function to diagnose ailments such as chronic kidney disease (CKD). Regular monitoring of UACR is essential for individuals susceptible to CKD, especially ones suffering from diabetes or hypertension. In this context, an advanced fluorescent (FL) biosensor is fabricated using glutathione-capped gold nanoparticles (GSH-AuNPs) with vibrant red emission around 656 nm (λexcitation = 570 nm). The utility of the as prepared GSH-AuNPs is recognized in the parallel detection of albumin and creatinine (CR) across a range of media (e.g., buffer solutions, synthetic urine, and real urine samples). The effects of albumin/CR on the FL attributes of GSH-AuNPs are also investigated. GSH-AuNPs exhibit enhanced FL upon the introduction of albumin (at pH 7.4) due to electrostatic interactions in an alkaline environment. In contrast, under acidic conditions (pH 5.0), the presence of CR substantially attenuates their FL intensity due to non-covalent interactions. The detection limits (with the corresponding detection ranges) for albumin and CR are 3.1 × 10−4 (0.0001–0.15) and 6.4 × 10−3 (0.05–4.9) mg·dL−1, respectively. The GSH-AuNPs biosensor is demonstrated to have excellent specificity and reproducibility against CR and albumin (plus the resulting UACR) in urine samples from individuals with normal renal function and those with CKD. This performance is maintained despite the presence of potential interfering substances, including glucose, urea, cations (Ca2+, K+, and Mg2+), anions (PO43− and SO42−), ascorbic acid, and GSH. A statistical comparison of our method with the Jaffe method shows outstanding correlation through the Bland-Altman plot (R2 = 0.99: n = 20). Our research should serve as a valuable reference for advancing point-of-care devices designed for detecting CKD biomarkers in biological fluid samples.