## 2 Application of BRBS in the Detection of Diabetic Nephropathy Biomarkers
### Creatinine (Crn)  
Crn is formed in everyday muscle wear and tear and is an important biomarker of renal qualitative and quantitative function. Crn levels play an important role in calculating muscle and renal function. The normal range of urinary Crn is about 282-2600 ppm. The normal range of serum Crn for women is 0.5-1.1 mg/dL (5-11 ppm) and for men is 0.6-1.2 mg/dL (6-12 ppm). Concentrations above 15 ppm require medical attention, and above 59 ppm indicate serious kidney damage [22]. The kidneys filter plasma through the processes of glomerular filtration and tubular excretion, thereby removing Crn to maintain homeostasis in the body. Crn content is helpful in quantifying the GFR, which is a very important indicator of kidney function and has been proven to be a potential biomarker for DN [23]. Clinically, early detection of renal impairment and the implementation of appropriate treatment measures can slow the progression of diabetic nephropathy by monitoring the levels of the albumin-to-Crn ratio [24]. [PERSON] et al. [25] developed an instant medical (Point-of-Care, PoC) sensor device based on LoRaWAN (Long Range Wide Area Network, remote wide area network). In this strategy, Crn was used as the template, methacrylic acid (MAA) as the functional monomer, 2,2-azoisobutronitrile (AIBN) as the reaction initiator, and divinylbenzene (DVB) as the cross-linking agent. MIP prepared by standard chemical methods using precipitation polymerization effectively coated the sensor surface with MIP by acrylic resin, making the sensing interface highly functionalized. The constructed sensor has a high specificity for selective adsorption of Crn molecules, and the electrochemical impedance spectrum (EIS) can accurately detect different levels of Crn content. The detection limit is as low as 0.1 ppm (Table 1). This low-cost, portable device allows patients to self-test at home, and the results obtained from this system can help doctors take necessary measures, which is  
Figure 1: (**A**) Schematic of the proposed procedure for constructing the molecularly imprinted polymer electrochemical biosensor. (**B**) Principle of MIP-ECS detection of HSA [20]. conducive to early detection and treatment of kidney injury to avoid further deterioration of diabetic nephropathy. In recent years, the advantages of N-MIT compared with traditional MIP preparation methods have attracted widespread attention. Currently, the common technique for preparing N-MIPs is solid-phase synthesis. In traditional methods for preparing MIPs, the TM are dispersed in the liquid medium, while the solid-phase synthesis method anchors the TM on a specific solid support, and subsequently carries out affinity purification of N-MIPs [26]. [PERSON] et al. synthesized N-MIPs with advantages such as high affinity, high specificity, excellent stability, and immobilized templates by uniformly distributing imprint nanoparticles in a polyvinyl chloride membrane through precipitation polymerization [27]. In particular, N-MIPs have a large specific surface area, which can expose more binding sites for recognizing small molecules or large biological molecules such as proteins, promoting the development of the imprinting material towards broader application prospects. On the other hand, electrochemiluminescence (ECL) has unique characteristics that differ from other electrochemical methods, such as high signal-to-noise ratio, high sensitivity, wide linear range, high temporal and spatial resolution, and near-zero background light [28]. Developing new chemiluminescence systems is one of the important ways to expand the detection range of ECL [29; 30]. [PERSON] et al. [31] synthesized nickel nanoclusters (NiNCs) as a new luminescent body and constructed an MIECS based on ECL for Crn detection.