Polymer Coating Adhesion Drives Functional and Biological Outcomes in Meniscus Implants

Abstract

Achieving stable integration of drug-releasing polymer coatings with load-bearing meniscus implants remains a challenge in biomaterials engineering. In this study, four surface modification strategies, femtosecond-pulsed laser treatment, oxygen plasma, polydopamine, and an ethyl-2-cyanoacrylate (ECA) interlayer, were evaluated for the integration of a dexamethasone (DEX)- and celecoxib (CLX)-releasing bilayer coating with a polycarbonate urethane (PCU) meniscus implant. The selected construct comprised an ECA interlayer applied from a 40% (w/v) solution, a CLX-loaded PLLA/PCL layer prepared at 100 mg/mL and a 53/47 (w/w) polymer ratio with 16.6% CLX loading, and an outer DEX-loaded PLGA layer prepared at 200 mg/mL with 2.44% DEX loading. At 37 °C, compared with uncoated PCU, ECA-containing constructs showed significantly higher storage modulus, loss modulus, and elastic modulus (p < 0.05), while tan δ remained unchanged, indicating preservation of the elastic-dominant viscoelastic response of the complete construct. The ECA-containing coating was subsequently adapted to the geometry of a sheep meniscus implant using an optimized dip-coating procedure. During a 21-day bioreactor study, repeated compression and shear increased cumulative DEX release from 59 to 67% and CLX release from 25 to 40% relative to static controls, while no visible coating delamination was observed. Ethylene oxide sterilization preserved drug loading and release behavior. In an exploratory three-month sheep study, the fiber-fixed coated implants remained in position, and the coating remained macroscopically associated with the retrieved prostheses. These findings support the use of an ECA interlayer to integrate a bilayer drug-releasing coating with a PCU meniscus implant while preserving construct-level mechanical behavior and drug release under the conditions evaluated.