Dual-state responsive gelatin colloid coating: Dynamically switching lubrication-adhesion for Ti-6Al-4V alloy

As a key metallic biomaterial in orthopedic implants, the clinical efficacy of titanium alloys is constrained by the colloid-based lubrication-adhesion imbalance at the bone-integration interface. In this study, leveraging the principles of colloid interface engineering, we innovatively developed an acrylic acid N-hydroxysuccinimide ester (AA-NHS) cross-linked gelatin/acrylic acid-surface functionalized nano-hydroxyapatite (nHAP) composite colloidal system. Through controlled self-assembly technology, an intelligent dual-state responsive interface coating was successfully fabricated. Coating characterization revealed that the 15 % gelatin component within the colloid network formed an ordered boundary lubrication layer under dehydrated conditions, reducing the friction coefficient by 77 %. In contrast, under hydrated conditions, the colloid-induced interfacial reconstruction triggered viscoelastic phase transitions, enhancing adhesion by 33 %, leading to a wear rate reduction of over 60 %. This colloid interface engineering strategy, through synergistic regulation of dry and wet state properties, established a dynamically adaptive smart lubrication-adhesion conversion mechanism tailored for physiological microenvironments, offering a theoretical framework for the development of next-generation biomedical interface materials.