Evaluating the Activity of Neuraminidase in Bacterial Vaginosis Microflora and Imaging Sialic Acid on the Cell Membrane by Boron and Nitrogen Codoped Fluorescent Carbon Dots

Sialic acids (SAs) are commonly located on the cell surface as terminal ends of glycoproteins and glycolipids. Neuraminidase (NEU) is a class of glycoside hydrolase enzymes that can cleave SAs from receptors. Both SA and NEU play important roles in human physiological and pathological processes of cell-cell interaction, communication, and signaling. Additionally, bacterial vaginosis (BV), a form of gynecological inflammation caused by dysbiosis of the vaginal microbiome, results in the abnormal activity of NEU in vaginal fluid. Here, we developed a novel probe for rapidly and selectively sensing SA and NEU based on a one-step prepared boron and nitrogen codoped fluorescent carbon dots (BN-CDs). The selective recognition reaction between SA and the phenylboronic acid groups on the surface of BN-CDs inhibits fluorescence emission from BN-CDs, while the NEU-catalyzed hydrolysis of SA bound on BN-CDs leads to fluorescence recovery. The probe was applied in diagnosing BV and showed consistent results to Amsel criteria. Moreover, the low cytotoxicity of BN-CDs facilitates its application in fluorescence imaging of SA on the membrane of red blood cells (RBCs) and leukemia cell lines (U937, KAS-1). The excellent sensitivity, accuracy, and applicability of the developed probe support its broad potential applications in future clinical diagnosis and treatment.