Dynamic mechanical response of polyvinyl alcohol-gelatin theta-gels for nucleus pulposus tissue replacement

Abstract

Intervertebral disk degeneration is one of the most significant contributors to low back pain. Thus, there is significant interest in designing new treatments and nucleus pulposus (NP) tissue replacements. Herein, the authors propose a biosynthetic material, comprised of a polyvinyl alcohol (PVA) and gelatin theta-gel, as an acellular NP tissue replacement. Theta-gels form during the solidification of PVA and gelatin (phase I), and the phase separation of a disklike short-chain polyethylene glycol (PEG, phase II). The PVA concentration and weight ratio of PVA to PEG were optimized, in order to achieve mechanical properties resembling NP tissue. Mechanical and material properties were analyzed for the PVA-gelatin theta-gels under static and dynamic conditions. Cyclic stress-strain testing demonstrated the theta-gels' ability to relax and perform properly under dynamic loading. Altering the molecular weight and concentration of the theta-gel constituents allows for a tunable material that can match a variety of native tissue properties.

PVA-gelatin hydrogels formed using combined theta-gel and cryo-gel fabrication techniques

“…(5-9) Theta-gels, PVA hydrogels formed in the presence of a porogen, take on a unique structure, with the lower molecular weight porogen and higher molecular weight PVA separating into two distinct phases during the thermal transition, resulting in enhanced crystallinity in the denser PVA-abundant regions. (10)(11)(12) The porogen can later be removed through dialysis, resulting in macro-pores in a rigid PVA network. (11,12) PVA hydrogels can also be formed through cryo-processing, during which the mechanical properties can be tuned through subsequent freeze-thaw cycles, resulting in cryo-gels.…”

“…(10)(11)(12) The porogen can later be removed through dialysis, resulting in macro-pores in a rigid PVA network. (11,12) PVA hydrogels can also be formed through cryo-processing, during which the mechanical properties can be tuned through subsequent freeze-thaw cycles, resulting in cryo-gels. (13)(14)(15) During cryo-gel fabrication, the formation and expansion of ice crystals within the PVA solution (or hydrogel for repeated freeze-thaw cycles) results in PVA densification in the material, increasing the overall organization and crystallinity of the material, thus increasing PVA rigidity.…”

Chondro‐inductive nanofibrous scaffold based gelatin/polyvinyl alcohol/chondroitin sulfate for cartilage tissue engineering

“…However, degradation of GT is fast in the body temperature . To overcome this problem, we used another polymer (PVA) to stabilize GT . Therefore, by combining GT and PVA in this study, we enjoy both GT and PVA characteristics, and results showed that the GT/PVA scaffold had improved cell behavior.…”

PVA‐Based Hydrogels: Promising Candidates for Articular Cartilage Repair

“…reported the preparation of PVA theta gel where polyethylene glycol (PEG) serves as porogen and is removed through dialysis after phase separation. [ 64 ]…”