Dynamic Surfaces—Degradable Polyester Networks that Resist Protein Adsorption

Abstract

We synthesized a series of novel degradable alternating copolyesters composed of diglycolic anhydride (DGA) and two epoxides, epoxymethoxytriethylene glycol (ETEG) and a photoactive crosslinking agent epoxy benzophenone (EBP). After UV crosslinking, soaking the films in a good solvent (tetrahydrofuran) removed uncrosslinked material, and the resulting film gel fractions were calculated. These network films were then degraded in buffer solutions of varying pH values. The degradation of networks with lower gel fraction (fewer crosslinks) was faster and followed first-order kinetics. In contrast, the denser network degraded slower and followed zeroth-order kinetics. The lower gel fraction networks possess a higher swelling ratio and resist bovine serum albumin (BSA) adsorption better by entropic shielding and faster degradation. In comparison, higher gel fraction networks with higher EBP mole fractions adsorb more BSA due to hydrophobic interactions and slower degradation.

Degradable Anti-Biofouling Polyester Coatings with Controllable Lifetimes

“…We and others have previously used benzophenone (BP)-containing units to promiscuously cross-link and covalently anchor polymer layers to surfaces. ,, Under UV irradiation, the BP units form triplet C•–O• bi-radicals. Those radicals abstract an adjacent hydrogen atom, creating two carbon-based radicals (C•–C•), which combine to form a covalent C–C linkage both between polymer chains and with the surfaces, forming surface-bound networks as described previously. ,, With the same strategy, the polyester with BP units were coated onto the glass slides and cross-linked by UV irradiation. After measuring their thicknesses, the specimens were incubated in tetrahydrofuran (THF) overnight to wash off the uncross-linked material.…”

“…4-[3-(Triethoxysilyl)­propyloxy]-benzophenone (TESPBP) was synthesized as described previously . Freshly prepared TESPBP were dissolved in toluene and spin-coated onto a UVO-cleaned silicon wafer (1500 rpm, 45 s spinning).…”

“…The specimen was then extracted with THF overnight to remove any uncross-linked polymer from the substrate leaving the cross-linked polyester network attached to the substrate (60–75 nm). The degradation study followed the procedure provided previously …”

“…We assumed that the adsorbed protein would be released with the degradation of the coatings. From our previous work, those dynamic (e.g., degradable) coatings resist protein adsorption better than similar, non-dynamic coatings within their lifetime …”

“…However, the lifetimes of those previously reported coatings are short due to fast degradation . Moreover, they could be prepared with only limited thickness, and they had poor mechanical properties, likely from their low molecular weight. − We synthesized new polyesters with a lower ester ratio in their backbone and with higher molecular weights to solve those problems.…”