Development of coatings rich in primary amines for biomedical applications

Martocq, Laurine and Douglas, Timothy and Robson, Alexander (2023) Development of coatings rich in primary amines for biomedical applications. PhD thesis, Lancaster University.

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Abstract

Biomaterials, such as hip prostheses or dental implants, must be well tolerated by the recipient, i.e., they must not cause inflammation, allergy, or a rejection reaction. The long-term success of a biomaterial largely depends on its integration into the body tissues due to adhesion of tissue-forming cells on the biomaterial’s surface, their proliferation, and differentiation to form tissue-specific extracellular matrix. Biomaterial surfaces govern their interaction with surrounding tissues, which can be tailored by modifying the surfaces. Microbial infection must also be prevented due to the growing threat of antibiotic-resistant bacteria. In this project, coatings rich in primary amine groups (-NH2) were developed via two different strategies. The first method involved plasma polymerisation. Allylamine plasma polymer coatings (AApp) were deposited with the usual collisionless ɑ regime vs. the collisional γ regime. The atomic composition of the coatings was characterised by XPS. -NH2 groups were quantified by a chemical derivatisation technique. Results showed that AApp coatings produced with the γ regime led to a higher degree of -NH2 retention. Therefore, the γ regime may be suitable to use during plasma polymerisation to obtain coatings rich in -NH2. The second method involved deposition of whey protein isolate (WPI) fibrillar coatings. Fibrils withstood autoclave sterilisation and were used as a matrix to incorporate biomolecules such as phloroglucinol (PG) and tannic acids (TAs). The presence of the coatings was attested by SEM images and XPS analyses. WPI/PG coatings improved bone forming-cell behaviour by increasing gene expression relative to matrix formation and mineralisation as well as by reducing the inflammatory response. WPI/TAs coatings did not have a negative impact on cell viability and might improve osteogenic differentiation. These amine-rich coatings may be applied on biomaterials such as bone implants to improve cell behaviour, but further work needs to be done to endow them with antimicrobial properties.