Excellence in Research: Designing biodegradable bottlebrush polymers based on their structure-property relationships for strong tissue adhesion and drug delivery

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NONTECHNICAL SUMMARYBiomedical adhesive polymers are nonmetallic materials which possess the ability to join two tissue surfaces together via bonding. Targeted tissues may include everything from hard tissues (bone, tooth, cartilage) to soft tissues (most other organs). The most common application of biomedical adhesives involves the replacement of conventional wound closures such as sutures and staples. Biomedical adhesives can be also used as hemostatic agents to stop bleeding, sealants to close large space gap between tissues, wound dressing to enhance healing, and drug delivery matrices to transport drugs efficiently and safely into the body. However, these existing biomedical adhesives products have significant limitations. These limitations include poor adhesion strength, limited tissue application, poor release over curing rate, applied tissues stiffening, and safety concerns surrounding their base materials, polymers. This project will develop a new, well-defined bottlebrush polymer that has strong adhesion to tissue, drug delivery capabilities, degradability, and biocompatibility. The proposed program will establish synthetic principles and structure-property relationships for multifunctional biomedical polymeric adhesives to overcome current limitations. This funding will also be used for the educational goal of developing a new participatory summer research program for HBCU undergraduate students. The program will allow students to acquire knowledge on basic research methods while studying polymeric adhesives at the PI’s lab. An additional collaborative summer research program, focused on underserved students, will provide state of the art research opportunities with other prestigious research groups at prominent institutes. TECHNICAL SUMMARY Bottlebrush polymers contain dense polymer brush chains linked to a backbone. The densely populated polymer brushes form a three-dimensional cylindrical shape and can encompass an increased population of functionalities in a unit space compared to linear polymers. Because the bottlebrush polymer demonstrates unique bulk properties such as low entanglement, low modulus, and other unique viscoelastic properties (e.g., supersoft elastomer), the bottlebrush polymer has received considerable attention in the past decade. However, previous bottlebrush polymer research has paid less attention to adhesive properties due to synthetic challenges. These challenges include the preparation of well-defined polymer structures and the lack of interdisciplinary knowledge on sophisticated polymer synthesis and adhesion/viscoelastic property characterization. In particular, integration of two or more functional groups on a bottlebrush polymer while still maintaining strong adhesion remains a challenging issue. In this project, a new approach is proposed by using both controlled radical polymerization and ring opening polymerization to synthesize the bottlebrush main structure. Then, a terminal of the dense bottlebrush chains will be modified to form ester linkages to gallol (strong adhesion), Ertapenem (antibiotics), 5-Fu (anticancer agent), and Oxaliplatin (anticancer agent). The detailed structure-property relationships of the new bottlebrush biomedical adhesive will be determined through the variation of the segmental ratio of gallol/drug, total polymer molecular weight, and brush chain lengths. The following comprehensive property characterizations will be performed to complete the structure-property relationship study: adhesion tests (lap shear strength tests and uniaxial indentation tests), viscoelastic property (rheometer), modulus test (tensile tester), heat generation test (thermometer), drug release test, biocompatibility test, and degradability test. The outreach and educational goals of this proposal is to develop a new participatory educational research program for underrepresented groups in HBCU. The participants will conduct real-world biomaterials research with Chung research group at FAMU-FSU college of engineering and with other collaborating research groups at other prestigious universities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.