Dual-Porosity Hollow Carbon Spheres with Tunable Through-Holes

Aug 24, 2018 - Dual-porosity hollow carbon spheres (DPHCs) with small mesopores (2–4 nm) and large through-holes (20–30 nm) on the shell were ...
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Functional Nanostructured Materials (including low-D carbon)

Dual-Porosity Hollow Carbon Spheres with Tunable Through-Holes for Multi-Guests Delivery Xi Wu, Yinsong Si, Yibiao Zou, Yuting Mao, Qiuju Li, Shuxue Zhou, Min Chen, and Limin Wu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b11825 • Publication Date (Web): 24 Aug 2018 Downloaded from http://pubs.acs.org on August 26, 2018

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Dual-Porosity Hollow Carbon Spheres with Tunable Through-Holes for Multi-Guests Delivery Xi Wu, Yinsong Si, Yibiao Zou, Yuting Mao, Qiuju Li, Shuxue Zhou, Min Chen*, Limin Wu

Department of Materials Science and State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, People’s Republic of China

ABSTRACT: Dual-porosity hollow carbon spheres (DPHCs) with small mesopores (2–4 nm) and large through-holes (20–30nm) on the shell were successfully synthesized using colloidal silica as templates, small silica nanoparticles (SNPs) as nanomasks, and nontoxic dopamine as the carbon precursor followed by post-carbonization and etching. The synthesized DPHCs were further oxidized to be hydrophilic and then used to simultaneously deliver the protein bovine serum albumin (BSA, 21×4×14 nm3) and the small molecule doxorubicin (DOX, 10 nm) 27-28. Two other techniques—emulsion approach and weak counterions templating method—are widely used to synthesize dendritic nanoparticles with hierarchical mesopores,14-15, 28 in which the pore sizes gradually increase from the particle center to the surface. It can thus form special center-radial pore structures29-30. For instance, Du and co-workers synthesized uniform dendrimer-like silica particles with small mesopores (4.3 nm) and center-radial pores (10–30 nm) through an ethyl ether emulsion approach, and the as-obtained nanocarriers were further functionalized to co-load hydrophilic anticancer drug (topotecan, TPT) with low molecular weight (M.W. = 421) as well as nucleic acid (pEGFP-N1 plasmid DNA (pDNA)) with high molecular weight (M.W. = 4733 bp)15. The TPT and pDNA co-loading capacity of this silica-based material is 200 mg/g and 9.7 mg/g, respectively. Although such hierarchically 3

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structured mesoporous nanoparticles are useful for co-loading and co-delivery of multiguests, the loading capacity is still relatively low due to the difficulty in tuning pores sizes to the appropriate scale. Recently, is was found that large through-holes on the shell of hollow nanospheres are beneficial for quick mass penetration, simultaneously loading and delivery of guest molecules of various sizes31. We have previously synthesized hollow silica nanospheres (300−460 nm) with large through-holes (10−30 nm) using lysozyme-assisted miniemulsion approach, and the as-obtained materials were utilized to load BSA biomacromolecules with a high loading capacity of 374.5 mg/g32. However, the large through-holes on the shell of silica spheres are irregular and unadjustable. Hence, it remains a challenge to fabricate uniform nanospheres with small mesopores and regular large through-holes, which should be promising for the co-loading/delivery of multiple guests of various sizes. Herein, a flexible and controllable synthetic strategy to fabricate dual-porosity hollow carbon spheres (DPHCs) with small mesopores (2–4 nm) and large throughholes (20–30 nm) is presented. In the synthesis, the amino-functionalized colloidal silica (SiO2-NH2) of 350 nm was utilized as the template, and small silica nanoparticles (SNPs, ~25 nm) were selected as through-hole nanomasks. Non-toxic dopamine (DA) was used as the carbon precursor and polymerized onto colloidal silica spheres in the ethanol/water/ammonia system. The SNPs were then simultaneously embedded into the PDA shell due to the hydrogen bonding interaction between amine and catechol groups 4

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ACS Applied Materials & Interfaces

in dopamine species and silanol groups in SNPs. Hollow cavity and through-holes were thus formed by etching the colloidal silica and small silica nanoparticles. To further verify the co-loading ability of synthesized carbon nanospheres, BSA (21×4×14 nm3) and DOX (