Hierarchical Composite Nanoarchitectonics with a Graphitic Core, Dendrimer and Fluorocarbon Domains, and a Poly(ethylene glycol) Shell as O2 Reservoirs for Reactive Oxygen Species Production

Graphene oxide (GO), single-walled carbon nanohorn (CNHox), and nitrogen-doped CNH (N-CNH) were functionalized with fluorinated poly(ethylene glycol) (F-PEG) and/or with a fluorinated dendrimer (F-DEN) to prepare a series of assembled nanocomposites (GO/F-PEG, CNHox/F-PEG, N-CNH/F-PEG, N-CNH/F-DEN, and N-CNH/F-DEN/F-PEG) that provide effective multisite O2 reservoirs. In all cases, the O2 uptake increased with time and saturated after 10-20 min. When graphitic carbons (GO and CNHox) were coated with F-PEG, the O2 uptake doubled. The O2 loading was slightly higher in N-CNH compared to CNHox. Notably, coating N-CNH with F-DEN or F-PEG, or with both F-DEN and F-PEG, was more effective. The best performance was obtained with the N-CNH/F-DEN/F-PEG nanocomposite. The O2 uptake kinetics and mechanisms were analyzed in terms of the Langmuir adsorption equation based on a multibinding site assumption. This allowed the precise determination of multiple oxygen binding sites, including on the graphitic structure and in the dendrimer, F-DEN, and F-PEG. After an initial rapid, relatively limited release, the amount of O2 trapped in the nanomaterials remained high (> 95%). This amount was marginally lower for the functionalized composites, but the oxygen stored was reserved for longer times. Finally, it is shown that these systems can generate singlet oxygen after irradiation by a light-emitting diode, and this production correlates with the amount of O2 loaded. Thus, it was anticipated that the present nanocomposites hierarchically assembled from components with different characters and complementary affinities for oxygen can be useful as O(2 )reservoirs for singlet oxygen generation to kill bacteria and viruses and to perform photodynamic therapy.

Automated summary

In this study, a series of assembled nanocomposites were prepared by functionalizing graphene oxide, single-walled carbon nanohorn, and nitrogen-doped CNH with fluorinated poly(ethylene glycol) and/or a fluorinated dendrimer. These nanocomposites provide effective multisite O2 reservoirs and show improved O2 uptake after coating with fluorinated materials. The best performance was obtained with the nanocomposite consisting of nitrogen-doped CNH coated with both fluorinated dendrimer and fluorinated poly(ethylene glycol).