A Hydrogen‐Bonded‐Supramolecular‐Polymer‐Based Nanoprobe for Ratiometric Oxygen Sensing in Living Cells

Abstract

5419wileyonlinelibrary.com signifi cant efforts have been devoted toward developing optical sensors for oxygen. [6][7][8][9][10][11] Quenching of phosphorescence is a powerful tool for oxygen sensing due to its invasiveness, selectivity, and (when applied in specifi c systems) sensitivity to oxygen. In addition, it can measure and map oxygen with high-resolution and in real-time in cells and tissues. Ratiometric oxygen sensing at two wavelengths allows for better calibration of oxygen levels and is more desirable in the chemical and medical fi elds than simple phosphorescence quenching. In a ratiometric sensor, oxygen concentration is calculated from the phosphorescence of an indicator dye and the fl uorescence of a reference dye. In the literature, such ratiometric oxygen sensors have been constructed by incorporation of phosphorescent dyes such as Pd(II)/Pt(II) porphyrin complexes inside conjugated polymer nanoparticles, [ 8 ] quantum dots, [ 9 ] silica gels, [ 10 ] and metal-organic frameworks. [ 11 ] Supramolecular polymers (SP), which are prepared from low-molecular-weight monomeric units that are associated through reversible noncovalent interactions (and thus different compositional constituents) can be effi ciently incorporated by copolymerization and provide a promising scaffold to fabricate phosphorescent functional nanomaterial for oxygen sensing. [ 12,13 ] In contrast to the rapid development of conjugated polymer nanoparticles for biosensing and bioimaging applications, [ 8 ] nanomaterials constructed from supramolecular polymers for sensing are still rare. [ 14 ] This can be attributed to the small number of examples of supramolecular polymers that have been found to form uniform nanostructures in water and are compatible with biological systems. Recently, we reported the construction of water-dispersible nanoparticles based on ureidopyrimidinone (UPy) quadruple hydrogen-bonded supramolecular polymers by a mini-emulsion method. [ 15 ] These nanoparticles exhibit several characteristics that make them ideal candidate for biological and biomedical applications. First, they have good structural and functional tunability because they are constructed from low-molecular-weight molecules, allowing synthetic elaborations for specifi c applications. Second, the nanoparticles are dispersed uniformly in aqueous solutions and stable for reasonably long periods. Third, the sizes of the nanoparticles are controllable by the concentration and type of the skeleton units. The small sizes of the nanoparticles should produce minimal cell damage and allow better cellular uptakeThe fi rst example of a ratiometric optical oxygen nanoprobe based on a hydrogen-bonded supramolecular polymer has been reported. The supramolecular polymer based nanoprobe (SPNP) is prepared from the co-assembly of a bis-ureidopyrimidinone (bis-UPy)-containing phosphorescent indicator (Por(Pd)-bisUPy), fl uorescent reference dye (BF 2 -bisUPy), and skeleton unit (DPA-bisUPy) through quadruple hydrogen bonds by a mini-emulsion method. The water-...

A Phosphorescent Platinum(II) Bipyridyl Supramolecular Polymer Based on Quadruple Hydrogen Bonds

“…The nanoparticles of Pt‐bisUPy in water maintain bright‐yellow luminescence at room temperature in the presence or absence of oxygen. This result is quite different from our previous report on nanoparticles made from bisUPy‐functionalized palladium porphyrin . This is likely due to the densely packed structure from the planar Pt‐bisUPy monomer inhibiting diffusion of oxygen to the emitting site.…”

A Solid‐State Fluorescent Material Based on Carbazole‐Containing Difluoroboron β‐Diketonate: Multiple Chromisms, the Self‐Assembly Behavior, and Optical Waveguides

“…Its derivatives have several attributes such as intense emission in both solutions and solid state, large molar extinction coefficients, two photoabsorption cross sections, and room‐temperature phosphorescence . These attributes make them have wide applications in various areas such as fluorescent sensors, bioimaging, and organic light‐emitting device (OLED) . Previously reported BF 2 bdk derivatives were mainly based on the aromatic rings (such as phenyl, naphthyl), whose assembly behaviors were rarely studied.…”

Supramolecular Interfacial Polymerization: A Controllable Method of Fabricating Supramolecular Polymeric Materials

“…Supramolecular polymers refer to polymers in which monomers are held together through highly directional noncovalent interactions, such as hydrogen bonding, host–guest interactions, π–π interactions, and metal coordination . Owing to the dynamic nature of the noncovalent interactions, supramolecular polymers exhibit unique properties such as reversibility, stimuli‐responsiveness, self‐healing, and good processability .…”