Introduction: Recently, our lab discovered that cationic hydrogels can be affixed to animal tissues using Electroadhesion (EA). This simple process involves contacting the gel with a tissue and applying a low DC electric field (~9 V) for just 30 seconds. The gel and tissue then become strongly adhered, and the adhesion persists indefinitely. Remarkably, this adhesion can also be reversed, if necessary, by applying the DC field with reversed polarity. While this discovery could transform surgical repairs, the current EA gels (Q33) suffer from significant drawbacks that limit their broader use. These acrylamide-based gels are non-degradable, necessitating surgical removal after the tissues have healed. Furthermore, they are quite fragile, prone to rupturing when stretched. To address these issues, we have developed next generation electroadhesive gels termed Q800/G that are tough, stretchable, degradable and also adhere strongly to tissues.
Materials and
Methods: Previous electroadhesive gels, termed Q33, were synthesized from a mixture of acrylated monomers containing quaternary ammonium for imparting a positive charge. Gel toughness was enhanced using two approaches. First, by synthesizing a double network that combines our original covalently cross-linked gel with a physically cross-linked gelatin network. Second, by increasing the monomer to cross-linker molar ratio from 33 to 800 in the chemically cross-linked network. Degradability was then introduced into this optimized gel by replacing the non-degradable cross-linker, N,N′-methylenebis(acrylamide), with a hydrolytically degradable analog, poly (ethylene glycol) diacrylate (PEGDA). Mechanical and adhesion strength were assessed through tensile and pull-off tests, respectively. In-vitro degradability was evaluated in phosphate-buffered saline (PBS) at 37°C. The surgical feasibility was assessed by measuring and comparing the burst pressure of a 4 mm incision in chicken intestines repaired using the Q800/G and Q33 gels.
Results, Conclusions, and Discussions: The next-generation electroadhesive gel, Q800/G, exhibited substantial improvements over the original EA gel, Q33. As shown in Figure 1, Q800/G showed a tensile strength of 115 kPa (17 times greater than Q33 gels) and elongation at break of 491% (35 times that of Q33 gels). Adhesion strength of Q33 and Q800/G to anionic gels (sodium acrylate) remained consistent at 20 kPa demonstrating that EA gels can be strong and degradable, with electroadhesive properties remained. In vitro degradation in PBS at 37°C revealed complete degradation within two weeks, with tunable degradation rates by adjusting PEGDA content. The Q800/G gel demonstrated significant improvement by effectively sealing 4.0 mm intestinal cuts, achieving a burst pressure of 92 mm Hg. In contrast, the Q33 gel failed to repair this size of intestinal injury, as its resulting burst pressure was below 80 mm Hg, which is the normal human bowel pressure.
In conclusion, the next generation electroadhesive gel, Q800/G, has been designed for mechanical robustness and degradability, effectively withstanding high burst pressures without compromising on adhesive strength. This underscores its potential as a robust surgical patch, offering significant advancements over current electroadhesive gels.
1. Borden, L. K.; Gargava, A.; Kokilepersaud, U. J.; Raghavan, S. R. “Universal Way to ‘Glue’ Capsules and Gels into 3D Structures by Electroadhesion.” ACS Appl. Mater. Interfaces, 2023, 15, 17070.
2. Borden, L. K.; Gargava, A.; Raghavan, S. R. “Reversible electroadhesion of hydrogels to animal tissues for suture-less repair of cuts or tears.” Nat. Commun., 2021, 12, 4419.
