N-acetyl-β-d-glucosaminidase (NAGase) is an established indicative biomarker released upon damage or necrosis of tubular epithelial cells in both humans and animals, indicating severe nephrological disorders and bovine mastitis (BM), respectively. The latter is the most common and costly disease in dairy cattle associated with production losses, elevated somatic cell counts and deteriorated health status. Herein, we report on a reflective based assay for early diagnosis of BM through the analysis of NAGase inherent content found in whole milk samples using a miniaturized optical transducer. Gelatin functionalized porous Si Fabry–Pérot interferometers are employed for monitoring the lysosomal activity in various stages of the inflammation (healthy, subclinical and clinical). The enzymatic reaction products precipitate and accumulate within the porous nanostructure, thus alter the average refractive index monitored using reflectometric interference spectroscopy. The optical assay is calibrated within the clinically relevant concentrations of BM while presenting a dynamic range of 1.04–16.7 μM min⁻¹ and the detection limit of 0.49 μM min⁻¹. The specific optical performance of the biosensor correlates with a gold standard laboratory-based approach, in which escalated somatic cell counts reveal augmented NAGase levels and thus severe pathogenesis. Overall, our study provides new opportunities to develop a convenient bio-diagnostic sensing system for BM detection and classification by addressing the limitations of conventional practices.

N-乙酰基-β- d-氨基葡萄糖苷酶（NAGase）是在人和动物中肾小管上皮细胞受损或坏死时释放的确定的指示性生物标志物，分别指示严重的肾病和牛乳腺炎（BM）。后者是奶牛中最常见，代价最高的疾病，与生产损失，体细胞计数升高和健康状况恶化有关。在这里，我们报告了一种基于反射的测定法，用于通过使用小型化光学传感器分析全脂牛奶样品中发现的NAGase固有含量来对BM进行早期诊断。明胶功能化的多孔SiFabry-Pérot干涉仪用于监测炎症各个阶段（健康，亚临床和临床）的溶酶体活性。酶促反应产物沉淀并积聚在多孔纳米结构中，因此改变了使用反射干涉光谱法监测的平均折射率。光学测定在临床相关的BM浓度范围内进行校准，同时动态范围为1.04–16.7μMmin^-1和0.49μM分钟检测极限^-1。生物传感器的特定光学性能与基于实验室的金标准的方法相关，在该方法中，体细胞计数的增加揭示了NAGase水平升高，从而导致严重的发病机理。总体而言，我们的研究为解决常规做法的局限性提供了开发方便的生物诊断检测系统用于BM检测和分类的新机会。