## 2 Application of BRBS in the Detection of Diabetic Nephropathy Biomarkers
### Platelet-Derived Growth Factor (PDGF)  
PDGF is an important cytokine composed of two peptide chains (A and B) connected by disulfide bonds in serum, which can promote the proliferation of vascular endothelial cells, smooth muscle cells, and the biosynthesis of renal tubule matrix, playing a crucial role in regulating cell growth and division [82]. PDGF-AA, PDGF-BB, and PDGF-AB are three subtypes of PDGF [83]. Among them, PDGF-BB is directly involved in cell transformation and tumor growth [84]. Studies have shown that the level of PDGF in the plasma of patients with diabetic nephropathy increases. PDGF can promote the proliferation and matrix generation of renal tubular cells, further accelerating the process of renal fibrosis, which leads to further deterioration of renal function. In addition, PDGF-BB is considered an important marker capable of predicting early deterioration of renal function in patients with diabetic nephropathy. Therefore, the sensitive and selective detection of PDGF-BB in biological samples has significant implications for the diagnosis of diabetic nephropathy. [PERSON] et al. [85] introduced an ECL aptasensor based on improved AuNPs to detect PDGF-BB (Figure 7). In this scheme, AuNPs-electrochemically reduced graphene(AuNPs-EG) nanocomposite material was electrodeposited on the GCE surface, and a large number of PDGF-BB APT (APT\({}_{1}\)) were fixed to amplify the detection response, constructing a highly conductive Aptasensor platform that can amplify the Luminol-H\({}_{2}\)O\({}_{2}\) system ECL signal. By functionalizing AuNPs with glucose oxidase (GOD), a signal probe for the sandwich sensor of the second aptamer (APT\({}_{2}\)) and GOD-modified AuNPs was designed. This ECL sensor has the advantages of high sensitivity, good stability, and good selectivity, and has good analytical performance in the concentration range of \(1.0\times 10^{-13}\)-\(5.0\times 10^{-10}\) mol L\({}^{-1}\) PDGF-BB, with a detection limit of \(1.7\times 10^{-14}\) mol L\({}^{-1}\) (Table 4). It has the potential for application in biochemical analysis. In recent years, two-dimensional layered transition metal dichalcogenide materials have opened a new door in the field of electrochemistry due to their unique electronic and electrochemical properties [86]. VS\({}_{2}\) has significant advantages in large specific surface area, good catalytic adsorption performance, and good biocompatibility. Normally, VS\({}_{2}\) has a stacked-layer structure, and the V atom inserts between two S atoms to form a sandwich structure. Unfortunately, like most transition metal oxides, the weak conductivity of VS\({}_{2}\) severely limits its further application in electrochemical biosensors. In order to improve the electrochemical performance of VS\({}_{2}\), it seems necessary to combine it with good electronic conductive materials. Framework nucleic acids (FNAs) are one-dimensional to three-dimensional (3D) framework structures formed by nucleic acid molecules through self-assembly [87]. The surface performance of electrochemical DNA biosensors modified with FNAs has been significantly improved. Due to the good stability and controllability of FNAs, they can be assembled in an ordered manner on gold surfaces to fabricate more probes [88; 89]. The controllable charge transfer characteristics of FNAs can be utilized to optimize the performance of electrochemical biosensors based on FNAs [90]. Compared to traditional electrochemical sensors functionalized with single-stranded DNA, electrochemical biosensors based on FNAs have stronger interference resistance and higher protein resistance. The empty structure allows for the maximization of space utilization, making it highly suitable for interface assembly with various materials [91]. [PERSON] et al.