How Human Serum Albumin-Selective Aptamers Complexed with Graphene Quantum Dot Recognize Canine and Feline Albumins: Simulation Studies

Kidney and liver disorders pose significant health challenges in companion animals. Human serum albumin (HSA) has been identified as a promising biomarker for these conditions in humans. Given the high sequence similarity (∼80%) among HSA, canine (CSA), and feline (FSA) serum albumins, this study investigates the feasibility of using CSA and FSA as biomarkers for kidney dysfunction in veterinary diagnostics. Graphene-based aptasensors have shown promise for selective albumin detection. Graphene acts as a sorbent for fluorescent dye-labeled HSA-selective aptamer. The HSA concentration is determined by the recovery of the fluorescence intensity. With a comparable size to aptamers, noncytotoxicity, and high biocompatibility of graphene quantum dot (GQD), it is attractive to explore the use of aptamer-functionalized GQD (GQDA) to recognize pet albumins. Herein, Molecular Dynamics (MD) simulations were performed to evaluate the binding of GQDA to CSA and FSA in comparison to HSA. The results indicate the spontaneous GQDA-albumin complex. Lysines and arginines serve as the main contributors. CSA binds GQDA through domain III like HSA, where the aptamer 3' tail serves as a key recognition site. In contrast, FSA shows weak binding to GQDA. FSA interacts with a rigid hairpin loop at the aptamer 5' end, which limits its accessibility. Overall, our findings suggest that the HSA-selective GQDA complex has strong potential to recognize CSA, but not FSA. This insight supports the future design of diagnostic tools for detecting kidney and liver dysfunction in canine patients.