Pediatric nephrotic syndrome (NS), characterized by proteinuria, hypoalbuminemia and progressive loss of kidney function, is a debilitating childhood kidney disease. In addition, steroid-resistant NS, accounting for about 10% of end- stage kidney disease in the pediatric population, may require long-term use of immunosuppressants that can cause nephrotoxicity. The daunting difficulty in pediatric venipuncture, as well as the small volume limit of maximum blood draw allowed for a single draw and within 2 months, especially in neonates, infants and young children, has limited close monitoring of kidney function in the active phase of NS. Moreover, urine dipstick test, as a semi-quantitative and not- always-reliable assay, is a crude way of evaluating the treatment response. It is also unable to assess the kidney function that may be compromised by volume contraction, routine use of diuretics and angiotensin-converting enzyme inhibitors, and drug-induced renal toxicity acutely. Thus, development of an innovative, pain-free and volume extraction-free, and highly sensitive biodiagnostic platform is imperative to improve the clinical care for pediatric NS patients. Bioanalyte-rich dermal interstitial fluid (ISF) provides a novel opportunity to achieve painless and effective biodiagnostic technologies. However, the clinical utility of ISF is limited by the current technology. Our goal is to develop our newly invented ultrabright plasmonic-fluor (PF)-enabled microneedle (MN) technology (PF-MN) as an ultrasensitive and minimally-invasive diagnostic tool for rapid sampling and quantification of ISF blood urea nitrogen (BUN) and creatinine (Cr) in point-of-care settings and at home. To accomplish our research goals, we will utilize a highly reproducible hereditary NS mouse model. In this preclinical model, we aim to determine concentrations of BUN and Cr in the dermal ISF by using PF-enhanced competitive immunoassay performed on MN. Furthermore, we will correlate their concentrations derived from MN-sampled ISF, extracted ISF and serum. A successful completion of our pioneering proposal may lead to a paradigm-shift in the newborn and pediatric diagnostics. It will also pave the way for future translational study in pediatric NS patients.