Construction methods and biomedical applications of PVA-based hydrogels

Abstract

Polyvinyl alcohol (PVA) hydrogel is favored by researchers due to its good biocompatibility, high mechanical strength, low friction coefficient, and suitable water content. The widely distributed hydroxyl side chains on the PVA molecule allow the hydrogels to be branched with various functional groups. By improving the synthesis method and changing the hydrogel structure, PVA-based hydrogels can obtain excellent cytocompatibility, flexibility, electrical conductivity, viscoelasticity, and antimicrobial properties, representing a good candidate for articular cartilage restoration, electronic skin, wound dressing, and other fields. This review introduces various preparation methods of PVA-based hydrogels and their wide applications in the biomedical field.

Keywords: PVA; articular cartilage restoration; electronic skin; hydrogels; wound dressing.

FIGURE 1

Physical cross-linking methods for PVA-based hydrogels. (A) PVA hydrogel prepared by F-T method, the number of F-T cycles can affect the structure and properties of the hydrogel (Stauffer and Peppast, 1992); (B) Principle of salting method (Wu et al., 2021); (C) Principle of directional freezing method (Hua et al., 2021); (D) Cross-linking by hydrogen bonding cross-linker (Liu et al., 2021).

FIGURE 2

(A) PVA-based hydrogel cross-linked by glutaraldehyde (Pei et al., 2021); (B) PVA-based hydrogel cross-linked by borax (Songfeng et al., 2020); (C) PVA-SA copolymer hydrogel (Shen et al., 2022).

FIGURE 3

(A) Schematic diagram of PVA-based hydrogel synthesis (Branco et al., 2022); (B) PVA-based hydrogel has good flexibility; (C) Annealing can enhance the mechanical strength of hydrogel (Chen et al., 2018); (D) PVA-based hydrogel can be used as articular cartilage contact surface with good tribological properties (Liu J. et al., 2020); (E) Organic solvent impregnation can significantly reduce the friction coefficient of hydrogel (Hu et al., 2022); (F) PVA-based hydrogel has good compression resistance and has the potential to be used as a load-bearing joint (Yang et al., 2020); (G,H) PVA-based hydrogel has good biocompatibility (Zhu C. K. et al., 2022).

FIGURE 4

(A,B) PVA-based hydrogel doped with Al³⁺ or Ca²⁺, the metal ions can make the hydrogel have good ionic conductivity (Gan et al., 2021; Lu L. et al., 2022); (C) The application of organic solvents enables the hydrogel to maintain good electrical conductivity in low-temperature environments and underwater. The concentration of NaCl solution affects the conductivity, and this hydrogel possesses sustained conductivity (Li et al., 2022c).

FIGURE 5

Properties and applications of PVA-based hydrogels in flexible sensing. (A) Ionically conductive PVA-based hydrogels can sensitively and reproducibly convert motion signals into electrical signals (Zhang L. et al., 2022); (B) Sweat sensors prepared using PVA-based hydrogels can respond to Na⁺, K⁺, Ca²⁺ and their concentrations in sweat (Qin et al., 2022); (C). Anti-freezing and water-preserving design of PVA-based hydrogel can in realizing sensing underwater (Lu L. et al., 2022); (D) PVA-based hydrogel monitors the movement process of human body (Qin et al., 2022); (E) Anisotropic PVA-based hydrogel can differentiate the movement signals in different directions (Peng et al., 2020); (F) PVA-composite hydrogel possesses excellent anti-freezing properties and can realize stable electrical signal conduction at −60°C (Dai et al., 2022).

FIGURE 6

Methods to enhance the mechanical properties of conductive PVA-based hydrogels; (A) Salt precipitation, especially immersion in Na₂SO₄ solution can substantially enhance the toughness of hydrogels (Wu et al., 2021); (B) Starch/PVA dual-network hydrogels possess good tensile properties and tensile strength (Lu L. et al., 2022); (C) Small multi-amine molecules enable the formation of dynamic nanoconfinement in the hydrogel, allowing the hydrogel to have excellent mechanical strength (Liu et al., 2021); (D) Composite PVA-based hydrogels formed with the introduction of a large number of metal-ligand and reversible bonds possess good mechanical strength (Cao J. L. et al., 2022).

FIGURE 7

Reversible chemical bonding and non-covalent interactions can confer good self-healing properties to PVA-based hydrogels. (A) Self-healing photographs and pattern diagrams of PVA-based hydrogels enriched with borate ester bonding and hydrogen bonding (Qin et al., 2022); (B) Schematic illustration of the principle of self-healing in PVA-based hydrogels, and their energy storage modulus and loss modulus before and after self-healing (Cao J. L. et al., 2022); (C) Copolymerization with poly (dopamine) enabled the PVA-based hydrogel to obtain excellent adhesion properties, and showed a certain adhesion strength to different substrates (Zhu H. et al., 2022); (D) Repeatable interfacial adhesion of the PVA-based hydrogel to the pig skin exhibit (Huang et al., 2023).

FIGURE 8

(A) PVA-based hydrogels can be affixed to chronic wounds and slowly release drugs under NIR light stimulation (Su et al., 2023); (B) PVA-based hydrogels can promote hydrogel wound healing (Liu et al., 2023); (C) PVA-based hydrogels can be copolymerized with antimicrobial active materials to obtain better antimicrobial properties (Su et al., 2023); (D) PVA-based hydrogels show better anti-inflammatory effects (Liu B. et al., 2022); (E,F) PVA-based hydrogels can achieve long-lasting drug release (Chen S. Y. et al., 2022).

FIGURE 9

Other applications of PVA-based hydrogels; (A) Schematic and photographs of the synthesis of PVA-based hydrogels for microneedle patches; (B) Schematic and photographs of microneedle patch application (Chen S. Y. et al., 2022); (C) PVA-based hydrogel for gastric retention device, which can be rapidly dissolved in the stomach and retained for a long period of time up to 30 days (Liu et al., 2019); (D) Gastric retention device in porcine stomach with X-ray photographs and drug release profile (Liu et al., 2017).