Articular Cartilage-Inspired Hybrid Double-Network Hydrogels with a Layered Structure and Low Friction Properties

Abstract

Biomimetic tough hydrogels composed of a biopolymer and a large amount of water, which show high mechanical and lubricating properties, are of great significance for articular cartilage application. In conventional tough hydrogel materials, there is a conflicting relationship between the lubricating capacity (hydration capacity) and the load-bearing capacity. Herein, inspired by the structure of articular cartilage, a layered hybrid double-network hydrogel (DN gel) was prepared by a two-step method; that is, the stiff and tough agar/poly (acrylamide-coacrylic acid)-Fe 3+ (Agar/PAMAAc-Fe 3+ ) DN gel was first fabricated, and then a layer of soft and tough Agar/PAMAAc DN gel was formed on it by an alkali-induced network dissociation strategy. In the layered hybrid DN gel, physical agar gel served as the first network, while chemical PAMAAc gel or PAMAAc-Fe 3+ gel acted as the second network. The coordination or dissociation between Fe 3+ ions and carboxyl groups can render the high stiffness or a low modulus of the DN gels, and the soft and tough Agar/PAMAAc DN gel layer played a role in reducing friction and the stiff and tough Agar/PAMAAc-Fe 3+ layer played a supporting role. As a result, a soft and tough lubricating layer on a stiff and tough load-bearing substrate provides an excellent balance of lubrication and load bearing, leading to a low coefficient of friction (COF) and wear-resistant biomimetic cartilage layered DN gel. The COF decreases from 0.024 to 0.001 as the compressive stress increases from 0.81 to 30.6 kPa. Because of their exceptional lubricating properties, layered hydrogels are attractive candidates for tissue engineering and medical devices.

Ultra‐low Friction and High Load‐Bearing Hydrogel with Tubular Structure Based on Controllable Light‐Induced Dissociation†

“…Hydrogel, the new functional material, as one of the scaffold materials suitable for tissue engineering, has the advantage of being a promising soft tissue material for articular cartilage replacement due to its high water content, good biocompatibility and surface lubricity. [ 6‐11 ] However, conventional hydrogel materials [ 12‐13 ] ( e.g ., polyvinyl alcohol (PVA), poly(hydroxyethyl methacrylate) (PHEMA) hydrogels, etc .) do not have sufficient mechanical properties and durability to withstand the constant cycles of load and friction.…”

Physically cross-linked organo-hydrogels for friction interfaces in joint replacements: design, evaluation and potential clinical applications

“…4 The hybrid agar/poly(acrylamideco-acrylic acid)-Fe 3+ hydrogels reported by Huang et al exhibit high tensile strength (up to 5.12 MPa) and tearing energy (1814 J m À2 ). 26 Despite the satisfactory mechanical performances of these double-crosslinked hydrogels, the possible residual acrylamide monomer caused by an incomplete reaction is carcinogenic and poses a threat to body health. 27 In this work, we used physically crosslinked organohydrogels based on hydrogen bonds between PVA, PHEMA, and glycerin to develop a promising alternative to current materials used in joint replacement surgery.…”

“…4 The hybrid agar/poly(acrylamide- co -acrylic acid)-Fe 3+ hydrogels reported by Huang et al exhibit high tensile strength (up to 5.12 MPa) and tearing energy (1814 J m −2 ). 26 Despite the satisfactory mechanical performances of these double-crosslinked hydrogels, the possible residual acrylamide monomer caused by an incomplete reaction is carcinogenic and poses a threat to body health. 27…”