Recently, interest in polyphenol-containing composite adhesives for various biomedical applications has been growing. Tannic acid (TA) is a polyphenolic compound with advantageous properties, including antioxidant and antimicrobial properties. Additionally, TA contains multiple hydroxyl groups that exhibit biological activity by forming hydrogen bonds with proteins and biomacromolecules. Furthermore, TA-containing polymer composites exhibit excellent tissue adhesion properties. In this study, the gelation behavior and adhesion forces of TA/Pluronic F127 (TA/PluF) composite hydrogels were investigated by varying the TA and PluF concentrations. PluF (above 16 wt%) alone showed temperature-responsive gelation behavior because of the closely packed micelle aggregates. After the addition of a small amount of TA, the TA/PluF hydrogels showed thermosensitive behavior similar to that of PluF hydrogels. However, the TA/PluF hydrogels containing more than 10 wt% TA completely suppressed the thermo-responsive gelation kinetics of PluF, which may have been due to the hydrogen bonds between TA and PluF. In addition, TA/PluF hydrogels with 40 wt% TA showed excellent tissue adhesion properties and bursting pressure in porcine intestinal tissues. These results are expected to aid in understanding the use of mixtures of TA and thermosensitive block copolymers to fabricate adhesive hydrogels for versatile biomedical applications.

The occurrence of leakage from anastomotic sites is a significant issue given its potential undesirable complications. The management of anastomotic leakage after gastrointestinal surgery is particularly crucial because it is directly associated with mortality and morbidity in patients. If adhesive materials could be used to support suturing in surgical procedures, many complications caused by leakage from the anastomosis sites could be prevented. In this study, we have developed self-healing, shear-thinning, tissue-adhesive, carbon-black-containing, gallic acid-conjugated chitosan (CB/Chi-gallol) hydrogels as sealing materials to be used with suturing. The addition of CB into Chi-gallol solution resulted in the formation of a crosslinked hydrogel with instantaneous solidification. In addition, these CB/Chi-gallol hydrogels showed enhancement of the elastic modulus (G′) values with increased CB concentration. Furthermore, these hydrogels exhibited excellent self-healing, shear-thinning, and tissue-adhesive properties. Notably, the hydrogels successfully sealed the incision site with suturing, resulting in a significant increase in the bursting pressure. The proposed self-healing and adhesive hydrogels are potentially useful in versatile biomedical applications, particularly as suture support materials for surgical procedures.

Postsurgical adhesions are common complications of abdominal and pelvic surgeries, often leading to bowel obstruction, chronic pain, and increased risks during reoperation. Although various physical barrier materials have been developed to prevent postsurgical adhesions, retaining anti-adhesive materials at surgical sites is challenging. In this study, we developed thermosensitive injectable gallic acid-conjugated hyaluronic acid (HA-GA) and Pluronic F127 (PluF) composite hydrogels to retain anti-adhesive materials and prevent postsurgical adhesion. The incorporation of HA-GA reduced the critical gelation concentration of PluF from approximately 18 to 12 wt% and decreased the gelation temperature from 28.5 °C for PluF to 25.6 °C for HA-GA (2 wt%)/PluF hydrogels with the left-shift in sol–gel curves. The G′ values increased from 10.1 ± 1.7 kPa for PluF to 24.8 ± 3.6 kPa for HA-GA (2 wt%)/PluF hydrogels at 37 °C. In addition, the HA-GA/PluF hydrogels exhibited enhanced mass retention as a function of time compared to PluF hydrogels alone. HA-GA (2 wt%)/PluF hydrogels retained 33.4 ± 3.5% of their initial mass after 7 d, whereas PluF was completely eroded within 3 d. The anti-adhesion efficacy of the HA-GA/PluF hydrogels was evaluated using a rat cecum abrasion model. Notably, the HA-GA (2 wt%)/PluF hydrogels showed reduced adhesion scores, with an adhesion extent score of 0.67 and 2.33 on postoperative day 7 and 21, respectively, compared with the untreated control group (3 and 3 on postoperative day 7 and 21). In addition, the adhesion severity scores of HA-GA (2 wt%)/PluF hydrogel groups were 0.33 and 1.33 on postoperative day 7 and 21, respectively, compared with the untreated control groups (1.67 and 2.33 on postoperative day 7 and 21). Therefore, HA-GA/PluF hydrogels provide reversible thermosensitive properties with enhanced stability and retention, supporting their potential as injectable physical barriers for postoperative adhesion prevention.