Background: Poly(acrylic acid) (PAA) is a water-soluble synthetic polymer with tissue-adhesive properties. When PAA is mixed with polyvinylpyrrolidone (PVP) in water, it forms a water-insoluble precipitate that neither swells nor adheres to tissues. Methods and Results: We developed a novel solid/solution interface complexation method to obtain a water-swellable PAA/PVP complex. First, PAA solution was dried up in a vessel to form a film. The PAA film was then immersed in an aqueous PVP solution to obtain a highly swollen PAA/PVP hydrogel. Heat drying of the hydrogel yielded a transparent film, while freeze-drying the hydrogel provided a soft sponge. Both the PAA/PVP film and sponge could be re-swelled by water to obtain a bioadhesive gel. A relatively larger specific surface area of the sponge than that of the film led to a more rapid swelling and water absorption behavior and quick adhesion to tissues. The addition of hyaluronic acid (HA) improved the mechanical characteristics of the sponges. PAA/PVP/HA sponges had low cytotoxicity, and they exhibited high hemostatic efficiency in clinical studies after dialysis treatment or tooth extraction, even in patients on antithrombotic drugs. Conclusions: Such bioadhesive materials consisting of low-toxicity polymers have a high potential for use in medical hemostatic devices.

In addition to protection against microorganisms and hemostasis, wound dressings are now expected to actively promote healing. A water-absorbing complex of poly(acrylic acid) (PAA) and polyvinylpyrrolidone (PVP) was developed by mixing the polymers under specific conditions. This complex swells in water and adheres strongly to biological tissues. Upon application to a wound, it absorbs blood, swells, and adheres firmly, providing coverage. During this process, blood cells that infiltrate the gel secrete growth factors and other bioactive molecules, which are retained and gradually released toward the wound, promoting healing. In the present study, the mechanical properties of the PAA/PVP complexes were analyzed, and their healing-promoting effects were examined. In a diabetic mouse skin wound model, untreated wounds remained over 95% of their original size after 4 days. In contrast, wounds treated with the PAA/PVP complex shrank to 70–75% of their original size by day 4, and further reduced to 17–23% by day 11. Histological analysis on day 11 showed complete or nearly complete re-epithelialization in PAA/PVP-treated wounds, while untreated wounds exhibited incomplete tissue regeneration. These results suggest that the PAA/PVP complex not only provides physical protection, but also facilitates tissue repair, demonstrating its potential as a next-generation wound dressing.

Poly(acrylic acid)/polyvinylpyrrolidone (PAA/PVP) hydrogen-bonded complexes are of growing interest as functional materials for biomedical applications. However, the influence of polyhydroxyl additives, such as polyols and sugars, on complex formation and material performance remains insufficiently understood. This study aimed to elucidate how polyhydroxyl compounds affect the physical properties of PAA/PVP complexes. Dried PAA films were brought into contact with aqueous PVP solutions containing various additives (glycerol, sugar alcohols, or sugars), and the resulting hydrogels were dried to form films. Their swelling behavior in water and PBS, thermal stability, and mechanical properties were comparatively evaluated. Sugar alcohols markedly improved swelling and flexibility, whereas sugars showed limited effects. Glucitol exhibited intermediate performance due to a high tendency toward intramolecular hydrogen bonding in aqueous media. Mechanistic analysis suggested that sugar alcohols act in a chaperone-like manner during complex formation, promoting microphase-separated structures composed of hydrogen-bonded domains and free segment regions. These findings provide new molecular insight into designing PAA/PVP-based materials with additives for biomedical applications.