Biqing Bao

Far-red/near-infrared fluorescent conjugated polymer nanoparticles with size-dependent chirality and cell imaging applications

A novel chiral conjugated polymer is developed and used for the preparation of conjugated polymer nanoparticles (CPNs) with particle sizes ranging from 80 to 190 nm. The size-dependent optical properties of chiral CPNs are fully studied and it was found that the nanoparticles exhibited a prominent red shift both in UV-vis and fluorescence emission with increasing diameters. The circular dichroism (CD) spectra and anisotropy r values of the CPNs display size-tunable chirality features, which can be attributed to the nature of the aggregates as nanoparticles grow. Meanwhile, the obtained CPNs can serve as efficient far-red/near-infrared (FR/NIR) fluorescent probes with low cytotoxicity and high photostability for HeLa cell imaging.

Facile preparation of multicolor polymer nanoparticle bioconjugates with specific biorecognition.

A facile and efficient strategy to prepare multicolor and surface-functionalizable conjugated polymer nanoparticles (PPVseg-COOH CPNs) was demonstrated. The CPNs with tunable photoluminescence colors and carboxylate groups were further covalently modified with a series of specific molecules such as streptavidin, IgG and poly(ethylene glycol) to show their generality for subsequent bioconjugation and biological applications. The streptavidin coating can significantly improve the photostability of the PPVseg-SA CPNs, which indicates that specific biomolecules such as streptavidin functionalization of multicolor PPVseg-COOH CPNs can be applied to achieve high optical stability of CPNs in various buffer solutions, metal ions for many biological applications. Furthermore, the resulted PPVseg-SA CPNs also show efficient labeling ability in specific cellular imaging. The synthetic methods present the feasibility and versatility for further developing surface-functionalizable CPNs probes with full-color tunability for biological imaging and bioanalytical applications.

Sensitive DNA detection using cascade amplification strategy based on conjugated polyelectrolytes and hybridization chain reaction

In this paper, a novel homogeneous hybridization chain reaction (HCR) assay is developed by using cationic conjugated polyelectrolytes (CPEs) as an indicator for the detection of DNA. In this assay, two hairpin probes H1 and H2 are labeled with fluorescein at their 5′-end and 3′-end respectively. After the HCR, the two hairpin probes are triggered by target DNA to form a long two-stranded DNA polymer with numerous fluorescein labelling in the strand, which is resistant to the S1 nuclease degradation. When the CPEs are added, strong electrostatic interaction between fluorescein-labeled DNA and CPEs occurred, which allowed fluorescence resonance energy transfer (FRET) from the CPEs to the fluorescein-labeled DNA and an obvious fluorescence colour change of the conjugated polymer solution. With HCR amplification and CPEs to amplify the fluorescence signal, homogeneous HCR for sensitive DNA detection is performed successfully. This proposed cascade amplification strategy can not only extend the application of HCR but also provides an alternative platform for homogeneous detection of DNA.

Chemically Functionalized Conjugated Oligoelectrolyte Nanoparticles for Enhancement of Current Generation in Microbial Fuel Cells

Water-soluble conjugated oligoelectrolyte nanoparticles (COE NPs), consisting of a cage-like polyhedral oligomeric silsesquioxanes (POSS) core equipped at each end with pendant groups (oligo(p-phenylenevinylene) electrolyte, OPVE), have been designed and demonstrated as an efficient strategy in increasing the current generation in Escherichia coli microbial fuel cells (MFCs). The as-prepared COE NPs take advantage of the structure of POSS and the optical properties of the pendant groups, OPVE. Confocal laser scanning microscopy showed strong photoluminescence of the stained cells, indicating spontaneous accumulation of COE NPs within cell membranes. Moreover, the electrochemical performance of the COE NPs is superior to that of an established membrane intercommunicating COE, DSSN+ in increasing current generation, suggesting that these COE NPs thus hold great potential to boost the performance of MFCs.

Nanoscale Organic–Inorganic Hybrid Photosensitizers for Highly Effective Photodynamic Cancer Therapy

Recently, photodynamic therapy (PDT) has attracted significant attention as a minimally invasive approach for cancer treatment. Clinical applications of current photosensitizers are often limited by their poor water solubility, low singlet oxygen (1O2) quantum yields, long-term toxicity, instability, and complex nanostructures. Here, we report a rational design of polyhedral oligomeric silsesquioxanes (POSSs)-based porphyrin (PPP5000) used as an intrinsically nanoscale photosensitizer. In this strategy, inorganic 3D rigid block POSSs not only act as antiaggregate units but also provide conjugating reactive sites for further chemical modification. Without an additional carrier and formulation process, PPP5000 intrinsically shows high water solubility (∼40 mg/mL), good PDT efficiency, and more excellent anticancer performance compared to tetra(hydroxyphenyl)porphyrin (the parent compound of m-THPC, Foscan). Considering the organic nature of porphyrin and the biodegradable property of inorganic POSS scaffolds at physiological conditions, the present work may lead to a new generation of biodegradable and intrinsic PDT agents with overall performance superior to conventional agents in terms of 1O2 production efficiency, water solubility, structurally stability, photostability, and biocompatibility.

AIE-active conjugated polymer nanoparticles with red-emission for in vitro and in vivo imaging

A novel red-emission conjugated polymer (PBPTPE) with aggregation-induced emission (AIE) characteristics was developed from boron dipyrromethene (BODIPY) derivatives and 1,2-bis(4-ethynylphenyl)-1,2-diphenylethene via palladium-catalyzed Sonogashira coupling reaction. The resulting polymer (PBPTPE) was weakly fluorescent in dichloromethane solution, but showed bright fluorescent emission when aggregated in dichloromethane/hexane mixtures or fabricated into conjugated polymer nanoparticles (PBPTPE NPs). The nanoparticles from PBPTPE were prepared through solvent-exchange method. PBPTPE NPs possess excellent photostability, including superior photobleaching resistance, and good stability in a wide pH range. Besides, in vitro cytotoxicity and hemolysis assay indicated that PBPTPE NPs had favorable biocompatibility. Furthermore, biological evaluation and bioimaging were performed using developmental stage zebrafish embryos. From the survival and hatching rate, oxidative stress and immune-related parameters, no significant adverse effect was observed. The microangiography in zebrafish, further shows that PBPTPE NPs can be used as a bioprobe for future in vivo applications.

Recent advances in fluorescent conjugated polymer nanoparticles

Fluorescent conjugated polymer nanoparticles have shown great potential applications in analytical chemistry, biomedicine and environmental chemistry. CPNs have received more and more intensive attention because of their excellent optical properties. These nanoparticles offer numerous advantages over traditional inorganic nanocrystals, including structure variety and improved photostability. Here, we present a review of current development in CPNs, including their synthetic method, optical properties, surface modification and bioconjugation. Significantly, we discussed their applications in bioimaging and chemosensors, the main development direction and the problems needed to solve in current research.

Investigation of Conjugated Polymers for Metal Ion Sensing

Two carboxylate-containing fluorene-based anoinic water-soluble conjugated polymers, which are specially de- signed to link fluorene with alternating moieties such as 5% benzo(2,1,3)thiadiazole (BT) and amine groups have been syn- thesized via the Pd-catalyzed Suzuki-coupling reaction, respectively. The optical properties of the neutral precursory poly- mers in CHCl3 and final carboxylic-anionic conjugated polyelectrolytes in aqueous solution were investigated. These poly- mers had good solubility in water and showed different responses for metal ions in aqueous environments. The fluorescence of carboxylic-anionic polyfluorene (PFA) can be quenched by most of metal ions selected (except K + , Li

Two-Photon Semiconducting Polymer Nanoparticles as a New Platform for Imaging of Intracellular pH Variation

Intracellular pH (pHi) plays a crucial role in cell physiological and pathological processes. We herein report an efficient pH-sensitive sensor based on two-photon excitable semiconducting polymer nanoparticles (PFV/PSMA-DA NPs) for pHi sensing. PFV/PSMA NPs were functionalized with redox-active dopamine (DA) and the obtained PFV/PSMA-DA NPs showed sensitive and reversible pH response over the pH range of 5.0-9.0. Owning to the high biocompatibility and pH-responsive DA, PFV/PSMA-DA NPs show low cytotoxicity and the quantification and imaging of intracellular pH changes of HeLa cells were successfully realized. Moreover, the detection of intracellular pH fluctuation induced by redox species such as NAC (N-acetylcysteine) and H2O2 was also achieved by both one- and two-photon excitation of the PFV/PSMA-DA NPs probe. This work clearly shows that nanoprobe based on two-photon PFV/PSMA-DA NPs could serve as a promising platform for quantitatively monitoring the intracellular pH fluctuations.

Polyhedral Oligomeric Silsesquioxane (POSS)-Based Cationic Conjugated Oligoelectrolyte/Porphyrin for Efficient Energy Transfer and Multiamplified Antimicrobial Activity

Cationic quaternary ammonium (QA) groups and reactive oxygen species as two main approaches for antibacterial study have been intensively studied. Herein, we report a multifunctional antimicrobial agent (porphyrin-POSS-OPVE, PPO), which combines bacterial membrane intercalation, high density of local QA groups, efficient energy transfer, significantly reduced aggregation, and high water solubility into one single molecule. The light-harvesting PPO contains multiple donor-absorbing arms (oligo( p-phenylenevinylene) electrolytes, OPVEs) on its globular periphery and a central porphyrin acceptor in the core by using three-dimensional nanocages (polyhedral oligomeric silsesquioxanes, POSSs) as bridges. The antiaggregation ability of POSS and the highly efficient energy transfer from multiple OPVE arms to porphyrin could greatly amplify singlet oxygen generation in PPO. Particularly, OPVEs with QA terminal chains were able to intercalate into Escherichia coli membranes, which facilitated 1O2 diffusion and bacterial cell membrane disintegration by QA groups. The increased local cationic QA charges in OPVE arms can also enhance the biocidal activity of PPO. Benefiting from these satisfactory features, PPO exhibits multiamplified antibacterial efficacy under a very low concentration level and white light dose (400-700 nm, 6 mW·cm-2, 5 min, 1.8 J·cm-2) to Escherichia coli (8 μM) and Staphylococcus aureus (500 nM). Therefore, PPO shows great potential for photodynamic antimicrobial chemotherapy at a much lower irradiation light dose and photosensitizer concentration level compared to previous reports.