‘On-demand’ soft tissue adhesives
Mogal, Vishal Tukaram
Date of Issue2016
School of Materials Science and Engineering
Bioadhesive mechanisms that employ external triggers for on-demand adhesion were developed to satisfy the following conditions 1) tunable adhesion 2) post-treatment modification on model and 3) application on wet, soft-tissue surfaces. A bioadhesive with these attributes could be activated on-site by an external trigger to overcome the challenges of non-specific protein binding and inadequate adhesion in wet conditions more often faced by clinicians who require better methods of soft tissue and medical implant fixation. Various plasma parameters were investigated for controlling model drug release and soft-tissue adhesion of polyester thin films. When compared to non-treated polyester thin films, plasma intensity could give rise to a ~ 6-fold (for 100 W, 5 min.) increase in shear adhesion strength (157 ± 24 mN/cm2). Shear adhesion was 5-fold higher than L-3,4-dihydroxyphenylalanine-based mussel adhesives tested on similar biomaterials. The results indicated that the adhesion strength was dependent upon plasma treatment time and plasma intensity, but was independent of the ratio of argon/oxygen generated plasmas. This plasma-mediated surface chemistry allows on-demand soft tissue adhesion of polyester thin films. The novel bioadhesive mechanism using diazirines that allows tunable adhesion using external stimuli was demonstrated and can be grafted on biodegradable polyester surfaces. These surface functionalized adhesive thin films works in wet condition by generating carbene radicals upon UV stimulation. The functionalized alkyl and aryl diazirine polyester films when tested for shear adhesion to ex-vivo swine aorta tissues, showed 450±50 mN/cm2 and 476±50 mN/cm2 adhesion strength when activated for 10 min and 2 min respectively using 0.5±0.1 mW/cm2 UV light of 365 nm. Thus, indicating the tuning of adhesion depending on time of UV irradiation and type of diazirines functionalized on polyester films. The covalent crosslinking of hydroxyethyl methacrylate polymer brushes grafted on quartz surface to wetted tissues were studied following long-range UV light activation. The potential applications of PHEMA polymer brushes through use of UV irradiation as a soft tissue adhesive in wet conditions were demonstrated for the first time. The technique demonstrate the dynamic and strong covalent adhesion of polymer brushes, which is reliable and straightforward, producing tissue-substrate bond that could retain their protein bio-functionality.