Accomplishing rapid adhesion of polymers could make it possible for various brand-new applications, consisting of, for example, hydrogels whose tightness might be finely tuned to much better adhere to particular tissues, on-demand encapsulation of versatile electronic devices for medical diagnostics, or the creation of self-adhesive tissue covers for hard-to-bandage parts of the body.Now, researchers at the Wyss Institute for Biologically Inspired Engineering at Harvard University and Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a flexible and easy approach to instantly and effectively bond layers made of the exact same or various types of hydrogels and other polymeric materials, using a thin movie of chitosan: a fibrous, sugar-based material derived from the processed outer skeletons of shellfish. It is presently used to deal with seeds and as a biopesticide in agriculture, to avoid spoilage in wine making, in self-healing paint finishes, and in medical wound management.The team discovered that chitosan films achieved strong and fast bonding of hydrogels through chemical and physical interactions that are various from those involved in standard hydrogel bonding approaches. Instead of producing new chemical bonds based on the sharing of electrons in between specific atoms (covalent bonds), induced by a tiny shift in pH, chitosans sugar strands quickly absorb water residing between hydrogel layers and entangle themselves with the polymer stands of hydrogels, forming numerous bonds via electrostatic interactions and hydrogen bonding (non-covalent bonds). Due to the high water material of chitosan-bonded hydrogels, their application likewise allowed the regional cooling of underlying human skin, which in the future could lead to alternative burn treatments.The researchers also wrapped hydrogels (hard gels) whose surfaces were modified with thin chitosan films seamlessly around bowel, tendon, and peripheral nerve tissue without bonding to the tissues themselves.
By Wyss Institute for Biologically Inspired Engineering at Harvard March 20, 2024This illustration highlights how 2 hydrogels (revealed in blue) can be bonded in different methods by thin chitosan films (displayed in orange). The bonds that form are extraordinarily strong and can withstand high tensions. Credit: Peter Allen, Ryan Allen, and James C. Weaver.An unique method for the quick and effective bonding of hydrogels offers the prospective to substantially propel forward the development of brand-new biomaterials, attending to a vast array of unhappy clinical demands.Hydrogels are ending up being progressively widespread in different biomedical fields due to their versatility. These biomaterials, which are comprised of networks of molecules inflamed with water, can be customized to reproduce the mechanical and chemical characteristics of different organs and tissues. This permits them to communicate with both the internal and external surfaces of the body without damaging even the most delicate locations of human anatomy.Hydrogels are already utilized in scientific practice for the therapeutic shipment of drugs to combat pathogens; as intraocular and contact lenses, and corneal prostheses in ophthalmology; bone cement, wound dressings, blood-coagulating bandages, and 3D scaffolds in tissue engineering and regeneration.However, attaching hydrogel polymers rapidly and highly to one another has stayed an unresolved unmet need as conventional methods frequently lead to weaker adhesion after longer-than-desired adhesion times, and count on complicated procedures. Achieving fast adhesion of polymers might enable various new applications, consisting of, for instance, hydrogels whose stiffness could be finely tuned to better comply with specific tissues, on-demand encapsulation of flexible electronic devices for medical diagnostics, or the creation of self-adhesive tissue wraps for hard-to-bandage parts of the body.Now, scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University and Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have actually produced a versatile and basic method to immediately and efficiently bond layers made from the exact same or different types of hydrogels and other polymeric materials, utilizing a thin movie of chitosan: a fibrous, sugar-based material obtained from the processed external skeletons of shellfish. They effectively applied their brand-new technique to a number of unsolved medical problems, consisting of the regional protective cooling of tissues, sealing of vascular injuries, and avoidance of undesirable “surgical adhesions” of internal body surfaces that should not stick to each other. The findings are published in the Proceedings of the National Academy of Science.”Chitosan films with their abilities to efficiently assemble, fine-tune, and secure hydrogels in the body and beyond, open numerous new chances to develop devices for regenerative medicine and surgical care,” said senior author and Founding Wyss Institute Core Faculty member David Mooney, Ph.D. “The speed, ease, and efficiency with which they can be used makes them extremely flexible tools and parts for in vivoassembly procedures in typically brief time-windows throughout surgical treatments, and the simple fabrication of complicated biomaterial structures in manufacturing centers.” Mooney also is the Robert P. Pinkas Family Professor of Bioengineering at SEAS.Engineering a brand-new bondOver the past years, Mooneys team at the Wyss Institute and SEAS has actually developed “Tough Adhesives,” a collection of regenerative medicine methods that use stretchable hydrogels to facilitate injury recovery and tissue regrowth by highly staying with wet tissue surfaces and adhering to tissues mechanical homes. “Precisely formulated Non-adhesive hydrogels and tough adhesives offer us and other scientists brand-new chances to enhance client care. To take their functionalities one or even multiple steps even more, we desired to be able to integrate 2 or more hydrogels in more intricate assemblies, and to do this quickly, securely, and in a basic procedure,” said co-first author and former Wyss Research Associate Benjamin Freedman, Ph.D., who led numerous Tough Adhesive advancements with Mooney. “Existing methods to immediately bond hydrogels or elastomers had striking disadvantages since they count on hazardous glues, the chemical functionalization of their surface areas, or other complicated treatments.”Through a biomaterial screening approach, the group identified bridging films completely made of chitosan. Chitosan is a sweet polymer that can be easily made from the chitin shells of shellfish and has currently discovered its way into extensive commercial applications. For instance, it is presently utilized to deal with seeds and as a biopesticide in farming, to prevent spoilage in winemaking, in self-healing paint coverings, and in medical injury management.The team found that chitosan films achieved strong and rapid bonding of hydrogels through chemical and physical interactions that are different from those included in conventional hydrogel bonding approaches. Instead of creating new chemical bonds based on the sharing of electrons in between individual atoms (covalent bonds), caused by a small shift in pH, chitosans sugar strands rapidly take in water residing in between hydrogel layers and entangle themselves with the polymer stands of hydrogels, forming several bonds by means of electrostatic interactions and hydrogen bonding (non-covalent bonds). This leads to adhesive forces between hydrogels that significantly exceed those developed through conventional hydrogel bonding approaches.First applicationsTo show the breadth of potential of their brand-new technique, the scientists concentrated on really different medical difficulties. They revealed that Tough Adhesives modified with chitosan movies might now be quickly twisted around cylindrical shapes like a hurt finger as self-adhering plasters to provide better wound care. Due to the high water content of chitosan-bonded hydrogels, their application also enabled the regional cooling of underlying human skin, which in the future might result in alternative burn treatments.The scientists also wrapped hydrogels (tough gels) whose surface areas were modified with thin chitosan films perfectly around bowel, tendon, and peripheral nerve tissue without bonding to the tissues themselves. “This method provides the possibility to successfully insulate tissues from each other during surgeries, which otherwise can form fibrotic adhesions with often devastating consequences. Their avoidance is an unmet clinical requirement that industrial technologies can not effectively address yet,” explained Freedman.In another application, they put down a thin chitosan movie on a tough gel that was already put on an injured pig aorta ex vivo as an injury sealant to increase the total strength of the plaster, which was exposed to the cyclical mechanical forces of blood pulsing through the vessel.”The many possibilities emerging from this research study by Dave Mooneys group add a new dimension to the engineering of biomedical hydrogel gadgets, which could lead to sophisticated services for urgent unmet problems in surgical and regenerative medicine that numerous clients could take advantage of,” said Wyss Founding Director Donald Ingber, M.D., Ph.D., who is likewise the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Childrens Hospital, and the Hansjörg Wyss Professor of Bioinspired Engineering at SEAS.Reference: “Instant tough adhesion of polymer networks” by Benjamin R. Freedman, Juan A. Cintron Cruz, Phoebe Kwon, Matthew Lee, Haley M. Jeffers, Daniel Kent, Kyle C. Wu, James C. Weaver and David J. Mooney, 20 February 2024, Proceedings of the National Academy of Sciences.DOI: 10.1073/ pnas.2304643121 Additional authors on the study are co-first author Juan Cintron Cruz, Mathew Lee, and James Weaver at the Wyss Institute and SEAS; Phoebe Kwon, Haley Jeffers, and Daniel Kent at SEAS; and Kyle Wu at Beth Israel Deaconess Medical Center in Boston. The research study was supported by the Wyss Institute at Harvard University, the National Institutes of Healths National Institute on Aging (under award # K99/R00AG065495), and the Harvard GSAS Research Scholar effort.