Abstract
Directed self-assemblies in water are known as the most efficient means of forming complex higher ordered structures in nature. Here we show a straightforward and robust method for particle assembly which utilises the amphiphilic tri-block co-polymer poloxamer-188 and a hydrophobic fluorophore as the two designer components, which have a built-in ability to convey spatial and temporal information about their surroundings to an observer. Templating of particle self-assembly is attributed to interactions between the fluorophore and hydrophobic segment of the poloxamer. Particle fluorescence in water is quenched but can be induced to selectively switch on in response to temperature, surface adsorption and cellular uptake. The ability of the particles to dynamically modulate emission intensity can be exploited for selective labelling and real-time imaging of drug crystal surfaces, natural fibres and insulin fibrils, and cellular delivery. As particle solutions are easily prepared, further applications for this water-based NIR-fluorescent paint are anticipated.
Highlights
Directed self-assemblies in water are known as the most efficient means of forming complex higher ordered structures in nature
We have devised a two component system that orchestrates a directed self-assembly (DSA) of fluorophore containing nano-capsules, which can self-report on dynamic changes within their local environment
Templating of the self-assembly is attributed to hydrophobic interactions between the fluorophore and PPO segment of the poloxamer leading to nanoparticles of ~100 nm in size
Summary
Directed self-assemblies in water are known as the most efficient means of forming complex higher ordered structures in nature. The availability of such a series of related polymers provides a valuable set of building blocks from which key physical and chemical properties can be selected at the outset to tailor a specific designer use or function[5] As such, they continue to receive substantial attention as drugdelivery systems for medicine, surfactants and coating agents for pharmaceutical formulations, constituents of nanoparticles engineered for drug delivery, and biological response modifiers[6]. The ability of certain poloxamers to re-sensitise multidrug resistant cancer cells is of great medicinal potential, with chemotherapeutics such as doxorubicin showing significant increases in cytotoxicity when a poloxamer delivery mechanism is used[8] Their surface adsorption properties make them widely used as coating agents for pharmaceutical formulation of drug nanocrystals, synthetic nanoparticles and other industrial material applications[9]. It would be a ground-breaking step forward if these advantageous NIR photophysical properties could be harnessed for off to on responsive imaging, in water, without the need for multi-step synthetic elaboration of the fluorophore to introduce PeT or ICT responsive moieties and water solubilizing groups
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