Written By Annie Duong After a surgical operation, it is common to use stitches, sutures, or staples to reconnect damaged tissue. Although effective, these methods present many difficulties in both the application and healing process because they may be challenging to use in parts of the body that are hard to reach and may take longer to heal due to risk of infection or damage to the surrounding tissue area. Researchers from Harvard University and Massachusetts Institute of Technology have engineered a surgical sealant made primarily from a very elastic protein found in connective tissue called tropoelastin [1]. This sealant has promising applications in surgery as it is quicker and more efficient to use, and may reduce infection rate and blood loss, especially in fragile tissue with sensitive pressure conditions.
The sealant is synthesized using human recombinant tropoelastin protein produced in large amounts of E. coli bacteria and a reagent with crosslinking properties, which allow for the chemical combination of molecules. With additional help from UV light, the highly elastic gel, termed MeTro gel, is solidified [2]. Another currently FDA approved surgical sealant in use called Progel has elasticity and tensile strength (or resistance to tension) that is much lower than that of the MeTro gel [3]. Thus, MeTro gel’s high resistance is promising in repairing elastic tissues found in the lung, heart, or blood vessels. MeTro’s properties were tested with in vivo experiments to assess its effectiveness in strength, high pressure conditions, and wound closure. A lap shear test was used to determine the strength of the gel by coating two glass slides with gelatin. As more stress was applied to the MeTro sealant and other developed sealants, the sealants’ resistance was measured. The resistance measurements in the lap shear tests of each sealant was found to be relatively similar. To investigate the other characteristics of the gels, in vitro burst pressure tests were performed. In this experiment, MeTro was found to have higher resistance to burst pressure than other developed sealants, demonstrating that it is ideal for lung tissue because it can withstand high pressures. Therefore, adhesive strength for MeTrol was significantly higher than the other commercially developed products, as it withstood the maximum pressure applied [3]. In addition, animal models were used to determine MeTro gel’s biocompatibility in vivo in its effectiveness in sealing. Using incision models in rat arteries, MeTro was applied at certain points of the cut aorta or placed at two ends of segments of the aorta. Pressure was applied to the artery to test the adhesion strength. All of the animals survived after the procedure, demonstrating that the gel sealed the incision effectively and blood pressure levels returned to normal. In addition, sealant tests were applied on pig lungs to determine how well the blood leakage held. At the end of the testing period, signs of pneumothorax were not detected. In effect, this demonstrated that the MeTro gel was able to seal wounds without the usage of the sutures [3]. The MeTro sealant still needs more testing to determine its effects on tissue healing and the biodegradation of the gel to make sure it can be used for widespread clinical use. With the development of this technology, hopefully those who undergo any form of surgeries can have better recoveries. References [1] Annabi, N., Shin, S.R., Tamayol A., Miscuglio, M., Afshar, M., Assmann, A., Mostafalu, P., Sun, J.Y., Mithieuz, S., Cheung, L., Tang, X., Weiss, A.S., Khademhosseini, A. 2016. Highly elastic and conductive human-based protein hybrid hydrogels. Adv Mater 28(1): 40-49. [2] Boettner, Benjamin. “A Super-Elastic Surgical Glue That Sticks and Seals in Vivo, Even When Tissues Are Moving.” Wyss Institute. 4 Oct. 2017 [3] Annabi, N., Zhang, Y.N., Assmann, A., Sani E.S., Cheng, G., Lassaletta, A.D., Vegh, A., Dehghani, B., Ruiz-Esparza, G.U., Wang, X. Gangadharan, S., Weiss, A.S., and Khademhosseini, A. 2017. Engineering a highly elastic human protein-based sealant for surgical applications. Sci Transl Med 9: 1-14.
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