Artificial cartilage made from a novel double‐network hydrogel: In vivo effects on the normal cartilage and ex vivo evaluation of the friction property

Abstract

This study evaluated the in vivo influence of a poly-(2-Acrylamido-2-methylpropane sulfonic acid)/poly-(N,N'-dimetyl acrylamide) (PAMPS/PDMAAm) double-network (DN) hydrogel on counterface cartilage in rabbit knee joints and its ex vivo friction properties on normal cartilage. In the first experiment, the DN gel was implanted in a surgically created defect in the femoral trochlea of rabbit knee joints and the left knee was used as the control. Evaluations using a confocal laser scanning microscopy demonstrated that the DN gel did not affect the surface microstructure (surface roughness, the number of small pits) of the counterface cartilage in vivo at 4 and 12 weeks. The histology also showed that the DN gel hadno pathological damage on the cartilage matrices and cells at 4 weeks. However, two of the five DN gel-implanted knees showed mild irregularity on the counterface cartilage surface at 12 weeks. In the second experiment, the friction property between the normal and the artificial cartilage was determined using a joint simulator apparatus. The ex vivo mean friction coefficient of the DN gel to normal cartilage was 0.029, while that of the normal-to-normal cartilage articulation was 0.188. The coefficient of the DN gel-to-normal cartilage articulation was significantly lower than that of the normal-to-normal cartilage articulation (p < 0.0001). This study suggested that the PAMPS/PDMAAm DN gel has very low friction coefficient on normal cartilage and has no significant detrimental effects on counterface cartilage in vivo, and can be a promising material to develop the artificial cartilage.

Designing hydrogels for controlled drug delivery

“…The cross-linked polymer network makes hydrogels solid-like, and they can possess a wide range of mechanical properties. For example, their stiffness can be tuneable 9 from 0.5 kPa to 5 MPa, allowing their physical properties to be matched with different soft tissues in the human body 10–12 . The cross-linked network can impede penetration of various proteins 13 , and thus is believed to protect bioactive therapeutics from premature degradation by inwardly diffusing enzymes.…”

Hydrogels for the Repair of Articular Cartilage Defects

“…164 The two hydrogel networks combine to form one material, theoretically mimicking the collagen and glycosaminoglycan phases of cartilage. 165 These degradation-resistant hydrogels exhibit similar compressive moduli to articular cartilage and lower coefficients of friction against normal cartilage than cartilage articulating against cartilage. 164,165 Implantation into weight-bearing defects or analysis of integration with surrounding tissue has not yet been performed.…”

Tissue Engineering of Muscles and Cartilages Using Polyelectrolyte Hydrogels

“…Moreover, PAMPS/PDMAAm DN gel caused a mild inflammation at 1 week after the gel implantation, and the inflammation degree significantly decreased at 4 and 6 weeks [29], and the implantation of PAMPS/PDMAAm DN gel into a femoral cartilage defect induced no significant damage to the opposite normal cartilage in the patella as well as to the postoperative healing of the knee joint [30]. There were no statistical differences in the cartilage surface roughness and the number of the small pits between the DN gel and the normal cartilage surface and the coefficient of the DN gel to normal cartilage articulation was significantly lower than that of the normal-to-normal cartilage articulation [30]. Recently, high stretchable and tough polyelectrolyte-based gel was developed by double network structure of negatively charged alginate and neutral polyacrylamide [31].…”

“…The double network gel composed of PAMPS and PDMAAm (PAMPS/PDMAAm DN gel) had a wear property comparable to the clinically available ultra-high molecular weight polyethylene [27,28]. Moreover, PAMPS/PDMAAm DN gel caused a mild inflammation at 1 week after the gel implantation, and the inflammation degree significantly decreased at 4 and 6 weeks [29], and the implantation of PAMPS/PDMAAm DN gel into a femoral cartilage defect induced no significant damage to the opposite normal cartilage in the patella as well as to the postoperative healing of the knee joint [30]. There were no statistical differences in the cartilage surface roughness and the number of the small pits between the DN gel and the normal cartilage surface and the coefficient of the DN gel to normal cartilage articulation was significantly lower than that of the normal-to-normal cartilage articulation [30].…”