Engineering a highly elastic bioadhesive for sealing soft and dynamic tissues

Abstract

Injured tissues often require immediate closure to restore the normal functionality of the organ. In most cases, injuries are associated with trauma or various physical surgeries where different adhesive hydrogel materials are applied to close the wounds. However, these materials are typically toxic, have low elasticity, and lack strong adhesion especially to the wet tissues. In this study, a stretchable composite hydrogel consisting of gelatin methacrylol catechol (GelMAC) with ferric ions, and poly(ethylene glycol) diacrylate (PEGDA) was developed. The engineered material could adhere to the wet tissue surfaces through the chemical conjugation of catechol and methacrylate groups to the gelatin backbone. Moreover, the incorporation of PEGDA enhanced the elasticity of the bioadhesives. Our results showed that the physical properties and adhesion of the hydrogels could be tuned by changing the ratio of GelMAC/PEGDA. In addition, the in vitro toxicity tests confirmed the biocompatibility of the engineered bioadhesives. Finally, using an ex vivo lung incision model, we showed the potential application of the developed bioadhesives for sealing elastic tissues.

Keywords: adhesive; elastic; hydrogel; poly(ethylene glycol) diacrylate; sealant.

FIGURE 1

Synthesis and characterization of GelMAC/PEGDA hydrogels. (a) Schematic representation for the fabrication of GelMAC/PEGDA hydrogels by visible light crosslinking of prepolymer solutions, and interactions between GelMAC and PEGDA comprised of covalent bonding upon photocrosslinking and ferric ion induced non-covalent chelation interactions. (b) ¹H NMR spectrum of porcine gelatin and GelMAC. (c) ¹H NMR spectrum of PEG and PEGDA. (d) ¹H NMR spectrum of GelMAC/PEGDA prepolymer and GelMAC/PEGDA crosslinked.

FIGURE 2

In vitro adhesive properties of the GelMAC/PEGDA hydrogels. (a) Schematic representation of tissue-hydrogel interaction. (b) Schematic representation of wound closure test (c) Adhesion strength for GelMAC/PEGDA hydrogels containing varying ratios of GelMAC and PEGDA. (d) Schematic representation of burst pressure test. (e) Burst pressure of elastic hydrogels fabricated with varying ratios of GelMAC and PEGDA. Hydrogels were prepared at 20% (w/v) total polymer concentration and 4 min visible light exposure time. Error bars indicate standard error of the means, asterisks mark significance levels of p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), and p < 0.0001 (****).

FIGURE 3

Tensile properties of GelMAC/PEGDA hydrogels. (a) Schematic and representative image of tensile test. (b) Extensibility, (c) Elastic modulus, and (d) Ultimate stress of the fabricated hydrogels containing varying ratios of GelMAC and PEGDA. Hydrogels were prepared at 20% (w/v) total polymer concentration and 4 min visible light exposure time. Error bars indicate standard error of the means, asterisks mark significance levels of p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), and p < 0.0001 (****).

FIGURE 4

In vitro swelling behavior and normalized mass of GelMAC/PEGDA hydrogels. In vitro swelling behavior of the fabricated hydrogels containing varying ratios of GelMAC and PEGDA incubated in DPBS at 37°C (a) without ferric ions, (b) with 2.5 mM ferric ions. Normalized mass of the GelMAC/PEGDA hydrogels containing varying ratios of GelMAC and PEGDA incubated in 5 U/mL of collagenase type II in DPBS at 37°C (c) without ferric ions, (d) with 2.5 mM ferric ions solution. Hydrogels were prepared at 20% (w/v) total polymer concentration and 4 min visible light exposure time. Error bars indicate standard error of the means.

FIGURE 5

In vitro 2D seeding of NIH 3T3 fibroblast cells on the GelMAC-Fe and (GelMAC/PEGDA)-Fe hydrogels. (a) Representative live/dead images of the cells seeded on the surface of fabricated hydrogels after 1, 4, and 7 days post-seeding. (b) Quantification of cell proliferation based on live/dead assay at days 1, 4, and 7 post-seeding. (c) Quantification of the viability of 3T3 cells seeded on the hydrogels using live/dead assays on days 1, 4, and 7 post-culture. (d) Quantification of metabolic activity of 3T3 cells seeded on the hydrogels using PrestoBlue assay on days 1, 4, and 7 post-culture. Hydrogels were applied at 20% (w/v) total polymer concentration and 20 s visible light exposure time. Error bars indicate standard error of the means, asterisks mark significance levels of **** p < 0.0001).

FIGURE 6

Ex vivo test to evaluate the sealing capability of the (GelMAC/PEGDA)-Fe sealant using a porcine lung incision model. (a) Creating incision, injecting hydrogel and photocrosslinking in situ: (a-i) incision created, (a-ii) removed visceral pleural layer, (a-iii) photocrosslinking of hydrogel, (a-iv) crosslinked hydrogel at the wound site. (b) A representative graph depicting the stepwise pressure increasing over time during testing (c) Burst pressure of GeMAC-Fe, (GelMAC/PEGDA)-Fe, and CoSeal. Hydrogels were formed at 20% (w/v) total polymer concentration and 4 min visible light exposure time.