Wenbo Hu

Lanthanide-doped NaxScF3+ x nanocrystals : crystal structure evolution and multicolor tuning

Rare-earth-based nanomaterials have recently drawn considerable attention because of their unique energy upconversion (UC) capabilities. However, studies of Sc(3+)-based nanomaterials are still absent. Herein we report the synthesis and fine control of Na(x)ScF(3+x) nanocrystals by tuning of the ratio of oleic acid (OA, polar surfactant) to 1-octadecene (OD, nonpolar solvent). When the OA:OD ratio was increased from low (3:17) to high (3:7), the nanocrystals changed from pure monoclinic phase (Na(3)ScF(6)) to pure hexagonal phase (NaScF(4)) via a transition stage at an intermediate OA:OD ratio (3:9) where a mixture of nanocrystals in monoclinic and hexagonal phases was obtained and the coexistence of the two phases inside individual nanocrystals was also observed. More significantly, because of the small radius of Sc(3+), Na(x)ScF(3+x):Yb/Er nanocrystals show different UC emission from that of NaYF(4):Yb/Er nanocrystals, which broadens the applications of rare-earth-based nanomaterials ranging from optical communications to disease diagnosis.

Engineering Lysosome-Targeting BODIPY Nanoparticles for Photoacoustic Imaging and Photodynamic Therapy under Near-Infrared Light

Developing lysosome-targeting organic nanoparticles combined with photoacoustic imaging (PAI) and photodynamic therapy (PDT) functions toward personalized medicine are highly desired yet challenging. Here, for the first time, lysosome-targeting BODIPY nanoparticles were engineered by encapsulating near-infrared (NIR) absorbed BODIPY dye within amphiphilic DSPE-mPEG5000 for high-performing lysosomal PAI and acid-activatable PDT against cancer cells under NIR light.

Homogeneous near-infrared emissive polymeric nanoparticles based on amphiphilic diblock copolymers with perylene diimide and PEG pendants: self-assembly behavior and cellular imaging application

An amphiphilic diblock copolymer, poly(perylene diimide acrylate)-block-poly(poly(ethyleneglycol)methacrylate) (PPDA-b-P(PEGMA)), has been synthesized via the reversible addition fragmentation transfer polymerization (RAFT) method. The polymer shows self-assembly behavior in water due to the synergistic effects of the strong hydrophobic interactions and π–π stacking of perylene diimide (PDI) groups. Homogeneous polymer nanoparticles (PNPs) in aqueous solution with good water solubility and stability were formed with an average size of 64.3 ± 3.3 nm, revealed by dynamic light scattering (DLS). The PNPs showed near-infrared (NIR) emission at 660 nm instead of the traditional emission of individual PDI groups at 530 nm. The aggregation-enhanced π–π stacking and the resulting NIR emission of the PDI groups were demonstrated by spectroscopy and 1H-NMR characterization. Cellular imaging of human pancreatic cancer cells was conducted with the obtained PNPs. Confocal microscopy results showed that the PNPs were located specifically within the cell cytoplasm. This study provides a new design concept to take full advantage of polymer amphipathy to fabricate nanoparticles with NIR emission for applications in bio-imaging.

Monodispersed grafted conjugated polyelectrolyte-stabilized magnetic nanoparticles as multifunctional platform for cellular imaging and drug delivery

An anionic grafted conjugated polyelectrolyte was synthesized, and then magnetic nanoparticles stabilized with this material were successfully prepared by a convenient method and used for bioimaging and drug delivery. Grafted conjugated polymer (PFPAA) containing abundant carboxyl groups was attached to the surface of Fe3O4 nanoparticles through ligand exchange with oleic acid and anionic grafted conjugated polyelectrolyte-stabilized magnetic nanoparticles (MNPs@PFPANa) were then obtained by ionization with sodium carbonate. These as-synthesized nanoparticles showed good water solubility and stability, with no precipitation observed in 8 months, and had a narrow size distribution with a mean hydrodynamic diameter of 26 ± 2.4 nm. In addition, these nanoparticles exhibited superparamagnetic properties with a saturation magnetization (Ms) of 20 emu g-1, which sufficient for bioapplications. Upon 48 h incubation with macrophage cells, the obtained nanoparticles showed good biocompatibility of 2 pg Fe per cell as measured by ICP-OES. Furthermore, MNPs@PFPANa were low toxicity as confirmed by an MTT assay using NIH-3T3 fibroblasts. Confocal microscopy results revealed that MNPs@PFPANa can be retained in cytoplasm with high fluorescence. MNPs@PFPANa exhibited good DOX drug loading efficiency of about 10 wt% and showed good therapeutic efficiency for BGC-823 cancer cells. These results indicated such multifunctional nanoparticles would be useful in bioimaging and as drug carriers for cancer treatment.

Conjugated polyelectrolyte brushes with extremely high charge density for improved energy transfer and fluorescence quenching applications

A conjugated polyelectrolyte brush (PB3) composed of a polyfluorene backbone and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) side chains is synthesized via atom transfer radical polymerization (ATRP), and its properties are investigated and compared with its linear counterpart (P2, poly[9,9′-bis(6-N,N,N-trimethylammoniumhexyl)fluorene] dibromide). Despite the same conjugated backbones for PB3 and P2, the polymer brush architecture of PB3 endows it with an extremely high charge density, consequently give rise to better optical stability, higher water solubility (28 mg mL−1) and higher quantum efficiency (52%) as compared to those of P2; moreover, it induces stronger electrostatic attraction with oppositely-charged analytes, making PB3 contact the energy donor or quencher molecules much more efficiently than P2 does. As such, PB3 can afford not only higher FRET-amplified dye emission but also larger fluorescence quenching constant as compared to P2. With its high water-solubility, the fluorescence of PB3 sustains in the presence of a large amount of ssDNA, showing its optical durability in complicated biological media. As a result, CPE brushes could constitute a new generation of water-soluble fluorescent macromolecules having desirable optical and biochemical properties for various sensing applications.

Oligo(p-phenyleneethynylene) embedded amphiphiles: synthesis, photophysical properties and self-assembled nanoparticles with high structural stability and photostability for cell imaging

Novel amphiphilic organic asymmetrically oligo(p-phenyleneethynylene) (OPE) conjugated molecules, ending with a hydrophobic alkyl chain and a hydrophilic methoxypolyethyleneglycol (MPEG) segment, were designed and synthesized. Due to the hydrophilic–hydrophobic nature of the asymmetrically amphiphilic OPE conjugated molecules, monodispersed fluorescent nanoparticles were obtained easily by self-assembly in aqueous solution. Through adjusting the length of MPEG chains in amphiphilic OPE, a series of nanoparticles with different water solubility were prepared. The aggregation behaviors of these dyes were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which indicated that when the MPEG chains bonding with amphiphilic OPE are longer, smaller sized nanoparticles will be formed at the same concentration of 10−5 mol L−1. Besides, taking OPE–PEG1900 as an example, diversified aggregation behaviors under different concentrations can be inferred through DLS and TEM, which were also supported by ultraviolet absorption (UV) and photoluminescence (PL) analyses. Compared with previously reported conjugated-polymer nanoparticles consisting of amphiphiles without photoelectric features and oil-soluble conjugated-polymers through non-covalent encapsulation, the introduction of OPE chromophores into amphiphiles by covalent linkage efficiently enhanced the structural stability of nanoparticles. A photobleaching test under UV excitation revealed the high photostability of these OPE nanoparticles. In view of the good water solubility, biocompatibility, structural stability, photostability, and excellent photoelectric features of these nanoparticles, cellular imaging of human pancreatic cancer cells (PANC-1 cells) was conducted. Confocal microscopy results showed that the nanoparticles (OPE–PEG1000 and OPE–PEG1900) were located specifically within the cell cytoplasm. We believe that the OPE nanoparticles would play an important role as fluorescent biomarkers for long-term bioimaging, and offer new opportunities for good applicability in cell imaging and sensing in biomedical science.

Efficiency enhancement in P3HT-based polymer solar cells with a NaYF4:2% Er3+, 18% Yb3+ up-converter

The commonly used donor material poly(3-hexylthiophene) (P3HT) confines the power conversion efficiency (PCE) in P3HT-based polymer solar cells due to its relatively large bandgap of ∼1.9 eV and the resultant limited absorption wavelength region of less than 650 nm. In this communication, the highly efficient up-conversion (UC) material NaYF4:2% Er3+, 18% Yb3+, converting near-infrared radiation into green and red emissions, is introduced into a P3HT/P3HT:[6,6] phenyl C61 butyric acid methyl ester (PC61BM) bulk heterojunction solar cell, referred to as a “bilayer cell”, to compensate for the non-absorbable wavelength region of P3HT. With an optimal UC doping concentration of 11.7% (weight ratio of UC to P3HT) in the P3HT matrix, the short-circuit current density and PCE for UC-doped bilayer cell are as high as 10.89 mA cm−2 and 3.62%, about 16.6% and 10.7% higher than the P3HT/P3HT:PC61BM bilayer cell and 22.4% and 16.4% higher than the standard P3HT:PC61BM bulk heterojunction one, respectively, although the fill factor in the UC-doped bilayer cell shows a slight decrease. The research result demonstrates that both the emission and the scattering of UC nanoparticles are beneficial to the enhancement of the solar cells electrical performances.

O-Nitrobenzyl-alt-(phenylethynyl)benzene copolymer-based nanoaggregates with highly efficient two-photon-triggered degradable properties via a FRET process

Light-controlled drug delivery systems constituted an appealing means to realize drug release spatiotemporally at the site of interest with high specificity. However, the utilization of light-activatable systems was hindered by the lack of suitable drug carriers that respond to near infrared light. Here, we reported a two-photon-triggered degradable amphiphilic copolymer in which the photo-cleavable species o-nitrobenzyl (ONB) was positioned alternately into the backbone of a (phenylethynyl)benzene (PEB) based polymer. Further, hydrophilic polyethylene glycol was grafted onto the side chain of the copolymer to obtain an amphiphilic structure, which could self-assemble into nanoaggregates (NAs). The state of NAs was unambiguously demonstrated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In this structure, the PEB fluorophore with a relatively good two-photon absorption (TPA) cross-section performed fluorescence resonance energy transfer (FRET) to ONB under 800 nm irradiation for two-photon-triggered photolysis. The aggregation state of copolymer NAs provided a large TPA cross-section and effective intermolecular/intramolecular FRET between PEB and ONB, which was beneficial for improving the degradation efficiency. As a proof of concept, a hydrophobic drug (Nile Red) was encapsulated into the NAs via a self-assembly method and was successfully released due to the photo-destruction of copolymer NAs upon two-photon excitation, thereby providing a variety of potential applications in two-photon-responsive drug delivery.

Perylene Diimide-Grafted Polymeric Nanoparticles Chelated with Gd3+ for Photoacoustic/T1-Weighted Magnetic Resonance Imaging-Guided Photothermal Therapy

Developing versatile and easily prepared nanomaterials with both imaging and therapeutic properties have received significant attention in cancer diagnostics and therapeutics. Here, we facilely fabricated Gd3+-chelated poly(isobutylene-alt-maleic anhydride) (PMA) framework pendent with perylene-3,4,9,10-tetracarboxylic diimide (PDI) derivatives and poly(ethylene glycol) (PEG) as an efficient theranostic platform for dual-modal photoacoustic imaging (PAI) and magnetic resonance imaging (MRI)-guided photothermal therapy. The obtained polymeric nanoparticles (NPs) chelated with Gd3+ (PMA-PDI-PEG-Gd NPs) exhibited a high T1 relaxivity coefficient (13.95 mM-1 s-1) even at the higher magnetic fields. After 3.5 h of tail vein injection of PMA-PDI-PEG-Gd NPs, the tumor areas showed conspicuous enhancement in both photoacoustic signal and T1-weighted MRI intensity, indicating the efficient accumulation of PMA-PDI-PEG-Gd NPs owing to the enhanced permeation and retention effect. In addition, the excellent tumor ablation therapeutic effect in vivo was demonstrated with living mice. Overall, our work illustrated a straightforward synthetic strategy for engineering multifunctional polymeric nanoparticles for dual-modal imaging to obtain more accurate information for efficient diagnosis and therapy.

A water-soluble conjugated polymer with azobenzol side chains based on “turn-on” effect for hypoxic cell imaging

A water-soluble conjugated polymer (WSCP) with enzymatic cleavable linkages (azobenzene) side chains for hypoxia imaging is reported. The fluorescence of the polymer would be recovered as the azobenzene moieties cleaved in hypoxia. This conjugated polymer was proved to be a good hypoxic sensor.