Article pubs.acs.org/cm
Water-Soluble Fluorinated and PEGylated Cyanostilbene Derivative: An Amphiphilic Building Block Forming Self-Assembled Organic Nanorods with Enhanced Fluorescence Emission Seunghoon Shin,†,‡ Se Hoon Gihm,§ Chong Rae Park,§ Sehoon Kim,*,‡ and Soo Young Park*,† †
Center for Supramolecular Optoelectronic Materials, WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea ‡ Center for Theragnosis, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Korea § Carbon Nanomaterials Design Laboratory, Global Research Laboratory, Research Institute of Advanced Materials, and Department of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea S Supporting Information *
ABSTRACT: We report synthesis and optical/structural characterization of new fluorescent rod−coil amphiphiles based on the PEGylated α-cyanostilbene skeleton (12EOCNMBE and 12EO-CNTFMBE) and their self-assembly behaviors in water. Distinct from the common amphiphilic behavior of nonfluorinated 12EO-CNMBE forming spherical nanostructures, fluorinated 12EO-CNTFMBE has proven to be the first example of a molecular building block that can selfassemble in water into small-dimension, small-aspect-ratio organic nanorods with aggregation-induced enhanced emission (AIEE). The robust structural integrity and hydrophobic/πconjugated nature of the fluorinated block assembly, as well as the antifouling coating by the hydrophilic PEG block, enabled stable encapsulation of a model drug (Nile Red) within the selfassembled nanorod structure and its successful delivery through membrane filters. By virtue of these advantageous attributes along with high intracellular uptake efficiency, the 12EO-CNTFMBE nanorods manifested potential as a self-signaling fluorescent nanocarrier for the intracellular delivery of hydrophobic cargos. KEYWORDS: aggregation-induced enhanced emission, bioimaging, cellular delivery carrier, fluorinated/PEGylated amphiphile, organic nanorods, self-assembly
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INTRODUCTION Organic molecular assemblies having controlled nanostructures are a class of nanomaterials that offer unique physicochemical properties distinct from those of inorganic counterparts. Among organic nanomaterials, self-assembled aggregates of amphiphilic molecular building blocks have gained considerable attention from the standpoint of basic researches on supramolecular chemistry as well as practical potential for biotechnological applications such as drug delivery, biomedical imaging, and tissue regeneration.1−4 Rigid-flexible block molecules (or rod−coil molecules), constituted of a rigid/ hydrophobic π-conjugated rod segment and flexible/hydrophilic poly(ethylene glycol) (PEG) coils, are a representative example that undergoes spontaneous assembly toward programmed nanostructures depending on the overall balance between noncovalent inter-rod attraction and rod−coil mutual repulsion.5−7 It has been reported that these rod−coil molecules can self-assemble into a variety of supramolecular architectures (spherical particles, capsules, fibers, tubes, ribbons, etc.) in aqueous solution by elaborate molecular design controlling the molecular shape and relative volume fraction © XXXX American Chemical Society
between the hydrophilic/hydrophobic parts. Among various nanostructures, however, tiny small-aspect-ratio nanorods have rarely been obtained by molecular assembly, except for largedimension cylindrical aggregates (>100 nm in diameter) produced by template growth,8 self-assembly,9 and anisotropic crystallization.10 In the development of inorganic nanomaterials, matallic or semiconducting nanorods (
