Biomimetic adhesion motifs based on RAFT polymers with phosphonate groups

Adhesion processes play a decisive role in the animal and human body and have been studied in great detail. Phosphorylation of serine as adhesion strategy is found in different species and serves different purposes, e.g. under water surface adhesion and protection strategies. Based on these biological adhesion applications, we present a biomimetic phosphonate-containing block copolymer approach to study surface adhesion. We synthesized two block copolymers (28 kDa and 39 kDa), which differed in their phosphonate-containing block dimethyl(2-methacryloyloxyethyl phosphonate) (DMMEP), using reversible addition fragmentation-chain transfer (RAFT) polymerization and tethered these polymers onto atomic force microscopy (AFM) probes. After performing AFM in single molecule force spectroscopy (SMFS) mode under physiological-like conditions (phosphate buffered saline - PBS, pH 7.2) on different substrates (mica, calcium deficient hydroxyapatite, TiO2 coated Si-wafer) we determined adhesion forces of 1610 +/- 76 pN and 2257 +/- 48 pN for the 28 kDa and the 39 kDa block copolymer, respectively. Our results show higher adhesion on hydroxyapatite, TiO2 and mica using polymers with a longer phosphonate block. This phosphonate containing block copolymer could serve as adhesion motif in several applications, and is very promising in the biomedical field, especially for tissue engineering applications due to its excellent adhesion on hydroxyapatite and titanium under physiological-like conditions.