A Pilot Study of Aptamer-Conjugated Silk Ligament with MSCs Recruitment Ability for ACL Reconstruction

Anterior cruciate ligament (ACL) rupture is one of the most common knee injuries. Due to the limited self-healing capacity, complex structure, and mechanical environment, the regeneration of ACL remains a challenge. To achieve fast recovery and long-term ACL regeneration, biodegradable scaffolds with excellent initial mechanical support and cell recruitment ability have gained increasing research interest. The aptamer-functionalized silk fiber was fabricated by embedding silk fiber into morpholinoethanesulfonic/1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride, N-hydroxysuccinimide buffer with aptamer 19s (Apt19s) and characterized in vitro. The clinically size-matched silk ligament was braided utilizing commercial methodology (polyethylene terephthalate ligament), and the tensile strength was analyzed. A total of 18 rabbits were used to test the early mesenchymal stem cell (MSC) recruitment of Apt19s-functionalized silk ligaments. Macroscopic analysis and hematoxylin and eosin and immunohistochemistry stainings were applied at 3, 5, and 7 days post-implantation. The ultimate strength of silk fiber was lower than that of PET fibers. However, the prepared silk ligament had comparable mechanical strength to the native ACL. In vitro, the Apt19s-functionalized fiber recruited bone marrow-derived MSCs. In vivo, Apt19s-functionalized silk ligament enhanced early MSCs recruitment after implantation in comparison with the aptamer-free ligament. The Apt19s-functionalized scaffold silk ligament exhibited comparable mechanical strength with native ACL and enhanced endogenous MSC homing.