Physically crosslinked polyvinyl alcohol hydrogels as synthetic cartilage materials

Introduction Polyvinyl alcohol (PVA) hydrogels have been considered very promising materials for the replacement of cartilage tissues due to their biocompatibility, chemical resistance, swelling capacity, and tribological behaviour [1 Baker MI, Walsh SP, Schwartz Z, et al. A review of polyvinyl alcohol and its uses in cartilage and orthopedic applications. J Biomed Mater Res B Appl Biomater. 2012;100(5):1451–1457.[Crossref], [PubMed] , [Google Scholar],2 Oliveira AS, Seidi O, Ribeiro N, et al. Tribomechanical comparison between PVA hydrogels obtained using different processing conditions and human cartilage. Materials. 2019;12(20):3413.[Crossref], [Web of Science ®] , [Google Scholar]]. However, their mechanical properties are still far from those of articular cartilage. In the present work, some PVA hydrogels are prepared with different compositions and under different conditions, to obtain materials with superior physical and mechanical properties.Materials and methods A 13.5% w/w PVA solution, prepared by dissolving the polymer (Mw 145,000 Da) in pure water for 20 h at 95 °C, was poured into Petri dishes and cooled to room temperature (8 h). Cast-drying (CD) (60 °C, 80% RH, 7 days) method was used to produce CDPVA gels. Some of these were subsequently annealed for 30 min at 100 °C, giving rise to CDPVA+A100 samples. The freeze-thawing (FT) procedure (6 cycles of 16 h of freezing at −20 °C and 8 h of thawing at room temperature) was chosen to prepare FTPVA and FTPVA+PAA samples. For the latter case, polyacrylic acid (PAA, MW 100,000 Da) was added to the PVA solution in the ratio of 3:10 (w/w) in relation to the PVA. The materials were characterised in terms of water content, wettability (captive bubble method), microstructure (SEM) and mechanical performance (compression tests).Results The CD gels presented lower water content and contact angles, a non-porous microstructure (see Figure 1), and higher rigidity than the FT samples. The annealing procedure slightly affected the studied properties of CDPVA, while the addition of PAA improved the water absorption of FT gels. Discussion and conclusions: The characteristics of PVA-based hydrogels can be easily tailored by adjusting the production method or combining PVA with other compounds in order to produce materials that best resemble human cartilage, and that can be used as substitutes for joint cartilage tissue.Physically crosslinked polyvinyl alcohol hydrogels as synthetic cartilage materialsAll authorsS. Schweizer, I. Monteiro, A.S Oliveira, P. Nolasco, R. Colaço & A.P Serrohttps://doi.org/10.1080/07853890.2021.1896904Published online:28 September 2021Figure 1. Microstructure of (a) CDPVA, (b) CDPVA+A100, (c) FTPVA, and (d) FTPVA+PAA.Display full sizeFigure 1. Microstructure of (a) CDPVA, (b) CDPVA+A100, (c) FTPVA, and (d) FTPVA+PAA.