Ratiometric pH sensing by fluorescence resonance energy transfer-based hybrid semiconducting polymer dots in living cells.

Intracellular pH plays a significant role in all cell activities. Due to their precise imaging capabilities, fluorescent probes have attracted much attention for the investigation of pH-regulated processes. Detecting intracellular pH values with high throughput is critical for cell research and applications. In this work, hybrid semiconducting polymer dots (Pdots) were developed and characterized and were applied for cell imaging and exclusive ratiometric sensing of intracellular pH values. The reported Pdots were prepared by blending a synthesized block polymer (POMF) and a semiconducting polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV) to construct a fluorescence resonance energy transfer system for ratiometric sensing. Pdots showed many advantages, including high brightness, excellent photostability and biocompatibility, giving the pH probe high sensitivity and good stability. Our results proved the capability of POMF-MEHPPV Pdots for the detection of pH in living cells.

Ratiometric Polymer Probe for Detection of Peroxynitrite and the Application for Live-Cell Imaging.

Peroxynitrite (ONOO-) is one of the sources of oxidation stress involved in many biological signaling pathways. The role of ONOO- being a double-edged sword in biological systems drives the development of effective detection tools. In this work, a boronate-based polymeric fluorescent probe PB-PVA was synthesized and the probe performance was evaluated. The probe exhibits ratiometric sensing of ONOO- in a range of 0-6 µM. There is good linear relationship between the probe fluorescence intensity ratio and ONOO- concentration. The probe also displays moderate selectivity towards ONOO- over other ROS. Moreover, it is water-soluble and possesses good biocompatibility which aids the imaging of ONOO- in living cells. These properties could make the probe a promising tool in in vitro study related to ONOO-.

Metallopolymer strategy to explore hypoxic active narrow-bandgap photosensitizers for effective cancer photodynamic therapy.

Practical photodynamic therapy calls for high-performance, less O2-dependent, long-wavelength-light-activated photosensitizers to suit the hypoxic tumor microenvironment. Iridium-based photosensitizers exhibit excellent photocatalytic performance, but the in vivo applications are hindered by conventional O2-dependent Type-II photochemistry and poor absorption. Here we show a general metallopolymerization strategy for engineering iridium complexes exhibiting Type-I photochemistry and enhancing absorption intensity in the blue to near-infrared region. Reactive oxygen species generation of metallopolymer Ir-P1, where the iridium atom is covalently coupled to the polymer backbone, is over 80 times higher than that of its mother polymer without iridium under 680 nm irradiation. This strategy also works effectively when the iridium atom is directly included (Ir-P2) in the polymer backbones, exhibiting wide generality. The metallopolymer nanoparticles exhibiting efficient O2•- generation are conjugated with integrin αvß3 binding cRGD to achieve targeted photodynamic therapy.

Nanoreactor-based catalytic systems for therapeutic applications: Principles, strategies, and challenges.

Inspired by natural catalytic compartments, various synthetic compartments that seclude catalytic reactions have been developed to understand complex multistep biosynthetic pathways, bestow therapeutic effects, or extend biosynthetic pathways in living cells. These emerging nanoreactors possessed many advantages over conventional biomedicine, such as good catalytic activity, specificity, and sustainability. In the past decade, a great number of efficient catalytic systems based on diverse nanoreactors (polymer vesicles, liposome, polymer micelles, inorganic-organic hybrid materials, MOFs, etc.) have been designed and employed to initiate in situ catalyzed chemical reactions for therapy. This review aims to present the recent progress in the development of catalytic systems based on nanoreactors for therapeutic applications, with a special emphasis on the principles and design strategies. Besides, the key components of nanoreactor-based catalytic systems, including nanocarriers, triggers or energy inputs, and products, are respectively introduced and discussed in detail. Challenges and prospects in the fabrication of therapeutic catalytic nanoreactors are also discussed as a conclusion to this review. We believe that catalytic nanoreactors will play an increasingly important role in modern biomedicine, with improved therapeutic performance and minimal side effects.

Nanoscale semiconducting polymer dots with rhodamine spirolactam as fluorescent sensor for mercury ions in living systems.

Mercury ion (Hg2+), as one of the most poisonous heavy metal ions, could seriously damage mental and neurological functions thus causing severe diseases. A fluorescent ratiometric sensor based on semiconducting polymer dots (Pdots) and rhodamine spirolactam derivate was developed for the detection of Hg2+. The Pdots were prepared by Poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-diphenylene-vinylene-2-methoxy-5-{2-ethylhexyloxy}-benzene)] (PDDB) with emitting strong green fluorescence. The organic fluorescence dye N-(rhodamine-B) lactam-hydrazine (RhBH), as Hg2+-recognizing monomer, was conjugated to the surface of Pdots. Hg2+ could specifically trigger ring-opening process of RhBH and thus induce strong Förster resonance energy transfer (FRET) effect, resulting in the green fluorescence decrease of Pdots (energy donor) and red emission derived from the ring-opened RhBH (energy acceptor) increasing. PDDB@RhBH showed a sensitive and reversible response toward Hg2+ and had a great performance on resisting interferences from various biological analytes. Additionally, both fluorescent imaging in living cells and zebrafish, and systemic toxicity analysis in rats demonstrated that PDDB@RhBH was a great potential fluorescent sensor for quantitative Hg2+ imaging in living systems.