Aptamer-based biotherapeutic conjugate for shear responsive release of Von Willebrand factor A1 domain

Smart polymers that mimic and even surpass the functionality of natural responsive materials have been actively researched. This study explores the design and characterization of a Single-MOlecule-based material REsponsive to Shear (SMORES) for the targeted release of A1, the platelet binding domain of the blood clotting protein von Willebrand factor (VWF). Each SMORES construct employs an aptamer molecule as the flow transducer and a microparticle to sense and amplify the hydrodynamic force. Within the construct, the aptamer, ARC1172, undergoes conformational changes beyond a shear stress threshold, mimicking the shear-responsive behavior of VWF. This conformational alteration modulates the bioavailability of its target, the VWF-A1 domain, ultimately releasing it at elevated shear. Through optical tweezer-based single-molecule force measurement, ARC1172s role as a force transducer was assessed by examining its unfolding under constant pulling force. We also investigated its refolding rate as a function of force under varied relaxation periods. These analyses revealed a narrow range of threshold forces (3-7 pN) governing the transition between folded and unfolded states. We subsequently constructed the SMORES material by conjugating ARC1172 and a microbead, and immobilizing the other end of the aptamer on a substrate. Single-molecule flow experiments on immobilized SMORES constructs revealed a peak A1 domain release within a flow rate range of (40-70 μL min^-1). A COMSOL Multiphysics model translated these flow rates to total forces of 3.10 pN-5.63 pN experienced by the aptamers, aligning with single-molecule force microscopy predictions. Evaluation under variable flow conditions showed a peak binding of A1 to the platelet glycoprotein Ib (GPIB) within the same force range, confirming released payload functionality. Building on knowledge of aptamer biomechanics, this study presents a new strategy to create shear-stimulated biomaterials based on single biomolecules.