Colloidal Supraballs of Mesoporous Silica Nanoparticles as Bioresorbable Adhesives for Hydrogels

The adsorption of polymers at the surface of mesoporous silica nanoparticles (MSNs) has been shown to provide a versatile way to create adhesion between hydrogels or biological tissues. Nevertheless, above a critical number of deposited nanoparticles, thick multilayers accumulate at the interface and the adhesion strength decreases as cracks easily propagate between weakly cohesive polymer-free nanoparticles. In order to suppress this limitation, we prepared spherical aggregates by spray drying during which MSNs are strongly adhered to by thermal annealing. The coatings produced with these microscopic supraballs (SB-MSNs) exhibit the same high specific surface area as MSN layers but with a much stronger cohesion between nanoparticles. Lap-shear tests with polydimethylacrylamide hydrogels clearly showed that the adhesion energy with supraballs can be significantly enhanced compared with nanoparticles (similar to 200% at 0.4 wt %). Peeling tests showed that the maximum adhesion energy reached with SB-MSNs (8 +/- 0.5 J/m(2)) is significantly higher than the one achieved with nonaggregated nonporous (3 +/- 0.1 J/m(2)) or mesoporous (6 +/- 0.4 J/m(2)) SNs. It can be even further increased (10 +/- 0.4 J/m(2)) by using macroporous supraballs. Moreover, confocal observations reveal that the largest adhesion enhancement obtained at high deposition concentrations is related to the formation of corrugated interfaces stabilized by supraballs. Finally, SB-MSNs degrade in biological media at the same rate as the elementary mesoporous nanoparticles, therefore offering an interesting combination of adhesion and bioresorbability for use as bioadhesives.