Abstract
Bridged silsesquioxane (BS) nanomaterials with chemical structures O1.5Si-R-SiO1.5 where R organic groups are emerging as the next generation of organosilica nanocomposites. Physical and chemical properties of BS materials can be governed by the nature of homogenously distributed organic fragments within the siloxane network.1 Nonetheless, due to the synthetic challenge to control the kinetic in sol-gel processes, most non-porous BS materials that have been extensively studied in the past two decades were macroscaled.2 For biomedical purposes BS NPs should be nonaggregated sub-200 nm nanomaterials to benefit the enhanced permeation and retention effect and have long circulation time, thus, accumulate in cancerous tissues and organs. Nature-inspired oxamide bridged silsesquioxane was used as a key component to endow nanoparticles with degradable feature. The designed nanomaterials were nonaggregated with biologically relevant sizes (sub-200 nm) for preferential accumulation in tumors. The unique constitution of the materials with a very high organic content (~50%) was found to be homogenously distributed within individual particle and confirmed by various techniques: FTIR, solid state NMR and STEM-EELS elemental mapping. The biodegradation of NPs was demonstrated in the presence of the trypsin enzymes in simulated biological media. Moreover, for in-vitro imaging nonporous fluorescent BS NPs were obtained via incorporation of fluorescein isothiocyanate moieties (Fig. 1). We described the first example of enzymatically degradable BS NPs based on oxamide bridges. These novel hybrid organosilica NPs can find significant interest as future biomedical applications of inorganic silica NPs require higher biodegradability. Currently the work with mesoporous BS nanomaterials based on the same precursor is conducting.