Compressive Mechanical Behavior of Partially Oxidized Polyvinyl Alcohol Hydrogels for Cartilage Tissue Repair

Abstract

Polyvinyl alcohol (PVA) hydrogels are extensively used as scaffolds for tissue engineering, although their biodegradation properties have not been optimized yet. To overcome this limitation, partially oxidized PVA has been developed by means of different oxidizing agents, obtaining scaffolds with improved biodegradability. The oxidation reaction also allows tuning the mechanical properties, which are essential for effective use in vivo. In this work, the compressive mechanical behavior of native and partially oxidized PVA hydrogels is investigated, to evaluate the effect of different oxidizing agents, i.e., potassium permanganate, bromine, and iodine. For this purpose, PVA hydrogels are tested by means of indentation tests, also considering the time-dependent mechanical response. Indentation results show that the oxidation reduces the compressive stiffness from about 2.3 N/mm for native PVA to 1.1 ÷ 1.4 N/mm for oxidized PVA. During the consolidation, PVA hydrogels exhibit a force reduction of about 40% and this behavior is unaffected by the oxidizing treatment. A poroviscoelastic constitutive model is developed to describe the time-dependent mechanical response, accounting for the viscoelastic polymer matrix properties and the flow of water molecules within the matrix during long-term compression. This model allows to estimate the long-term Young’s modulus of PVA hydrogels in drained conditions (66 kPa for native PVA and 34–42 kPa for oxidized PVA) and can be exploited to evaluate their performances under compressive stress in vivo, as in the case of cartilage tissue engineering.

Designing Viscoelastic Gelatin-PEG Macroporous Hybrid Hydrogel with Anisotropic Morphology and Mechanical Properties for Tissue Engineering Application

“…The hydrogel showed compressive moduli of 0.33 MPa and 0.12 MPa, respectively, when compressed parallel and perpendicular to the macroporous channels. These moduli are in the same range as native articular cartilage [47][48][49][50][51][52][53][54][55]. Consecutive cyclic (showed hysteresis loop) and stress relaxation (overall stress relaxed around 30%) tests revealed that the Gel-PEG hydrogel was viscoelastic in nature, which made the hydrogel a potential platform for cartilage tissue engineering [38].…”

“…Consecutive cyclic (showed hysteresis loop) and stress relaxation (overall stress relaxed around 30%) tests revealed that the Gel-PEG hydrogel was viscoelastic in nature, which made the hydrogel a potential platform for cartilage tissue engineering [38]. This time-dependent response of the hydrogel is due to the contribution of the viscoelastic behavior of the polymer matrix and water migration through the hydrogel pores [48,56]. The hydrogel showed excellent shape recoverability during the cyclic loading-unloading test.…”

Bridging Gaps in Peripheral Nerves: From Current Strategies to Future Perspectives in Conduit Design

“…This material represents a sort of evolution from the non-resorbable polyvinyl alcohol, of which the commercially available SaluBridge TM /SaluTunnel TM (Salumedica LLC) guides are made. With respect to its native counterpart, OxPVA is distinguished by a tunable biodegradation rate, highly potential bioactivity, and adjustable physical characteristics, thus standing out as a customizable polymer, as proved by the ability to satisfy different prosthesis characteristics for different tissue targets [36,69,70,102,[106][107][108][109][110][111]. Additionally, the possibility to be "impressed" or poured with/within specific molds and safely physically cross-linked (freezing-thawing method) without potentially toxic chemical agents is also fundamental from the perspective of creating "cell-instructive devices" (such as those encouraging an orderly regeneration of the axons) with no cytotoxic effect [69].…”

Development and preclinical evaluation of bioactive nerve conduits for peripheral nerve regeneration: A comparative study

“…In the wide panorama of biomaterials, the new OxPVA stands out revealing as a promising resource for smart prosthesis fabrication in tissue engineering [ 2 , [16] , [17] , [18] , 20 , 29 , 43 ]. However, despite first appealing in vivo results, its specific chemical and physical characteristics still allow for intense research and development activities [ 22 , 23 , 43 , 44 ] to assure a fine control over pro-regenerative behaviour of the derived devices.…”