Control of Kinetic Pathways toward Supramolecular Chiral Polymorphs for Tunable Circularly Polarized Luminescence.

An amphiphilic aza-BODIPY dye (S)-1 bearing two chiral hydrophilic side chains with S-stereogenic centers was synthesized. This dye exhibited kinetic-controlled self-assembly pathways and supramolecular chiral polymorphism properties in MeOH/H2O (9/1, v/v) mixed solvent. The (S)-1 monomers first aggregated into a kinetic controlled, off-pathway species Agg. A, which was spontaneously transformed into an on-pathway metastable aggregate (Agg. B) and subsequently into the thermodynamic Agg. C. The three aggregate polymorphs of dye (S)-1 displayed distinct optical properties and nanomorphologies. In particular, chiral J-aggregation characteristics were observed for both Agg. B and Agg. C, such as Davydov-split absorption bands (Agg. B), extremely sharp and intense J-band with large bathochromic shift (Agg. C), non-diminished fluorescence upon aggregation, as well as strong bisignated Cotton effects. Moreover, the AFM and TEM studies revealed that Agg. A had the morphology of nanoparticle while fibril or rod-like helical nanostructures with left-handedness were observed respectively for Agg. B and Agg. C. By controlling the kinetic transformation process from Agg. B to Agg. C, thin films consisting of Agg. B and Agg. C with different ratios were prepared, which displayed tunable CPL with emission maxima at 788-805 nm and g-factors between -4.2×10-2 and -5.1×10-2.

Room-Temperature Liquid Crystalline Tetraphenylethylene-Surfactant Complex with Chiral Supramolecular Structure and Tunable Circularly Polarized Luminescence.

A novel room-temperature liquid crystal of tetraphenylethylene derivative (TPE-DHAB) was synthesized using an ionic self-assembly strategy. The TPE-DHAB complex exhibits typical aggregation-induced emission properties and a unique helical supramolecular structure. Moreover, the generation and handedness inversion of circularly polarized luminescence (CPL) can be achieved through further chiral solvation, providing a facile approach to fabricate room-temperature liquid crystalline materials with controllable supramolecular structures and tunable CPL properties through a synergistic strategy of ionic self-assembly and chiral solvation process.

Supramolecular Structure and Photo-Thermo-Electric Property of Hydrogen-Bonded Liquid Crystalline Polymer Containing Poly(4-vinylpridine) and Cyanostilbene Side Chains.

A series of side-chain liquid crystalline polymers P4VP(CN-DBE)x , where x is the molar ratio of cyanostilbene (CN-DBE) to poly(4-vinylpyridine) (P4VP) repeating unit, was synthesized based on the intermolecular hydrogen bonding between P4VP and CN-DBE. Their luminescent property, liquid crystalline structure and photo-thermo-electric property were elucidated using photoluminescence spectra, X-ray diffraction, thermal imaging and thermoelectric experiments. With the increase of x, the supramolecular system can be changed from lamellar structure to hexagonal columnar structure. Moreover, the P4VP(CN-DBE)x polymer with columnar structure exhibits more efficient photothermal effect. The temperature of P4VP(CN-DBE)0.6 can rise to 130 °C within 10 s under the irradiation of ultraviolet lamp. In addition, the supramolecular system possesses unique photo-thermo-electric conversion ability, and 25 mA current can be detected in the circuit coupled with the thermoelectric module. This work broadens the potential applications of hydrogen-bonded polymer, and provides a simple and facile strategy to prepare liquid crystalline polymers with photo-thermo-electric property.

Correction: Synthesis and properties of siloxane modified perylene bisimide discotic liquid crystals.

Correction for 'Synthesis and properties of siloxane modified perylene bisimide discotic liquid crystals' by Tingjie Zhang et al., Soft Matter, 2013, 9, 10739-10745, https://doi.org/10.1039/C3SM52054D.

An amphiphilic B,O-chelated aza-BODIPY dye: synthesis, pH-sensitivity, and aggregation behaviour in a H2O/DMSO mixed solvent.

A novel amphiphilic B,O-chelated azadipyrromethene (aza-BODIPY) dye, containing hydrophobic dodecyloxy groups and hydrophilic tetraethylene glycol (TEG) chains, was synthesized and characterized by NMR, HRMS, Vis/NIR absorption and fluorescence spectroscopy. The B,O-chelated dye 1 exhibited largely bathochromically shifted NIR absorption and fluorescence spectra in comparison with common BF2-chelated aza-BODIPY dyes. Upon gradual addition of trifluoroacetic acid (TFA) to the dye 1 solution, obvious spectral changes were observed in Vis/NIR absorption and fluorescence spectroscopy measurements. Meanwhile, the colour change of the dye 1 solution from pink to blue was noticeable by the naked eye, indicating the pH-sensitivity of dye 1. The pH-sensitivity of dye 1 under acidic conditions could be ascribed to the formation of dye species 2·H+. Furthermore, owing to the amphiphilic feature of dye 1, it self-assembled into J-type aggregates in a mixed solvent of water/DMSO (2/8, v/v). Temperature-dependent Vis/NIR spectroscopic studies revealed a cooperative aggregation process of dye 1 and a nanowire-like morphology of the nanoaggregates was observed by AFM.

Blue emissive dimethylmethylene-bridged triphenylamine derivatives appending cross-linkable groups.

Five new dimethylmethylene-bridged triphenylamine (DTPA) derivatives 4a-e bearing peripheral cross-linkable vinyl and trifluorovinyl groups were synthesized. The chemical structure of these compounds was characterized by 1H NMR, 13C NMR and HRMS. Their optical properties were studied by UV/Vis spectroscopy and fluorescence spectroscopy. Based on these studies, blue-coloured fluorescence and high fluorescence quantum yields were obtained for 4a-e. The electrochemical properties of these compounds were studied by cyclic voltammetry and the results were further elucidated by DFT calculations. Furthermore, the thermotropic properties of the new DTPAs were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Compounds 4a-d exhibit high thermal stability and thermal cross-linkable properties. These results provide an effective strategy for the design and synthesis of thermally stable and cross-linkable DTPA derivatives with tunable optical and electrochemical properties.

Redox stimulus disulfide conjugated polyethyleneimine as a shuttle for gene transfer.

Redox-responsive cationic polymers have gained considerable attention in gene delivery due to low cytotoxicity and spatio-temporal release of DNA into the cells. Here, we reported the synthesis of reducible disulfide conjugated polyethyleneimine (1.8 kDa) (denoted as SS-PEI) and its application to transfer pEGFP-ZNF580 plasmid (pZNF580) into EA.hy926 cell. This reducible SS-PEI polymer was prepared by one-step polycondensation reaction of low molecular weight PEI with bis-(p-nitrophenyl)-3,3'-dithiodipropionate. The SS-PEI successfully condensed pZNF580 into nano-sized complexes (170 ± 1.5 nm to 255 ± 1.6 nm) with zeta potentials of 3 ± 0.4 mV to 17 ± 0.9 mV. The complexes could be triggered to release pZNF580 when exposed to the reducing environment of 5 mM dithiothreitol. Besides, the SS-PEI exhibited low cytotoxicity. In vitro transfection results showed that SS-PEI exhibited good transfection efficiency comparable to PEI25kDa. Thus, the SS-PEI could act as an reducible gene carrier with good transfection efficiency and low cytotoxicity.

Living Supramolecular Polymerization of an Aza-BODIPY Dye Controlled by a Hydrogen-Bond-Accepting Triazole Unit Introduced by Click Chemistry.

An aza-BODIPY dye 1 bearing two hydrophobic fan-shaped tridodecyloxybenzamide pendants through 1,2,3-triazole linkages was synthesized by a click reaction and characterized. 1 H NMR studies indicated that dye 1 exhibited variable conformations through intramolecular H-bonding interaction, which is beneficial for the polymorphism of aggregation. The thermodynamic, structural, and kinetic aspect of the supramolecular polymerization of dye 1 was investigated by UV/Vis absorption spectroscopy, IR spectroscopy, AFM, TEM, and SEM. Biphasic aggregation pathways of dye 1, leads to the formation of off-pathway, metastable Agg. I and thermodynamically stable Agg. II with distinct H-aggregation spectra and nanoscale morphology. The living manner of the supramolecular polymerization of dye 1 was demonstrated in seeded polymerization experiments with temperature-modulated successive cooling-heating cycles.

Multifunctional Gene Carriers Labeled by Perylene Diimide Derivative as Fluorescent Probe for Tracking Gene Delivery.

Multifunctional carriers with both gene transfection property and fluorescent tracking function have attracted significant attention in recent years. Herein, a kind of perylene diimide derivative (PDI-C10C8) is conjugated onto the polyethylenimine-g-poly(lactide-co-glycolide)-g-polyethylenimine (PLGA-PEI) polymer to obtain fluorescent multifunctional polymer and micelles (abbreviated as MP). Then, the REDV-G-TAT-G-NLS (TP-G) peptide sequence is grafted onto this MP to obtain multifunctional micelles labeled by perylene diimide derivative (MP-TP-G). These micelles exhibit enhanced photobleaching stability compared with the reference Cy5-labeled micelles, and the fluorescent images of cellular uptake show bright red emission without any background noise. Confocal laser scanning microscope (CLSM) experiments show that gene complexes can deliver gene into nucleus. MP-TP-G carriers do not enter into the cell nucleus, which proves that the nuclear localization signal sequence may not exert its nucleus accumulation ability via conjugating to the amphiphilic polymers. The high transfection efficiency and the enhanced photobleaching stability, combined with the ability to monitor the detailed process of cellular uptake and gene delivery, make these multifunctional micelles have great potential application for endothelialization of artificial blood vessels and gene delivery process study.

Synthesis, Self-Assembly and Characterization of Tandem Triblock BPOSS-PDI-X Shape Amphiphiles.

In this article, we report the facile synthesis, self-assembly, and characterization of shape amphiphiles (BPOSS-PDI-X) based on isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS), perylene tetracarboxylic diimide (PDI), and (60)fullerene (C60) moieties. Firstly, an asymmetrically functionalized diblock shape amphiphile precursor (BPOSS-PDI-OH) was obtained through the one-pot reaction between perylene-3,4,9,10-tetracarboxylic dianhydride and two different amines, namely BPOSS-NH2 and 3-amino-1-propanol. It was further conjugated with C60-COOH to give a tri-block shape amphiphile (BPOSS-PDI-C60). Their chemical structures were thoroughly characterized by NMR, IR and MALDI-TOF MS spectrometry. In order to gain insights on the structure-property relationship, their self-assembly in gas phase, in solution, and in solid state were characterized using traveling wave ion mobility mass spectrometry (TWIM-MS), UV/Vis absorption, fluorescence emission spectrophotometer, and transmission electron microscopy, respectively. It was found that BPOSS-PDI-OH formed more complicated dimers than BPOSS-PDI-C60. Both samples showed unique aggregation behaviors in solution with increasing concentration, which could be attributed neither to H- nor to J-type and might be related to the discrete dimers. While BPOSS-PDI-C60 could hardly crystalize into ordered structures, BPOSS-PDI-OH could form nanobelt-shaped single crystals, which may hold potential applications in microelectronics.

Oligohistidine and targeting peptide functionalized TAT-NLS for enhancing cellular uptake and promoting angiogenesis in vivo.

BACKGROUND: Gene therapy has been developed and used in medical treatment for many years, especially for the enhancement of endothelialization and angiogenesis. But slow endosomal escape rate is still one of the major barriers to successful gene delivery. In order to evaluate whether introducing oligohistidine (Hn) sequence into gene carriers can promote endosomal escape and gene transfection or not, we designed and synthesized Arg-Glu-Asp-Val (REDV) peptide functionalized TAT-NLS-Hn (TAT: typical cell-penetrating peptide, NLS: nuclear localization signals, Hn: oligohistidine sequence, n: 4, 8 and 12) peptides with different Hn sequence lengths. pEGFP-ZNF580 (pZNF580) was condensed by these peptides to form gene complexes, which were used to transfect human umbilical vein endothelial cells (HUVECs). RESULTS: MTT assay showed that the gene complexes exhibited low cytotoxicity for HUVECs. The results of cellular uptake and co-localization ratio demonstrated that the gene complexes prepared from TAT-NLS-Hn with long Hn sequence (n = 12) benefited for high internalization efficiency of pZNF580. In addition, the results of western blot analysis and PCR assay of REDV-TAT-NLS-H12/pZNF580 complexes showed significantly enhanced gene expression at protein and mRNA level. Wound healing assay and transwell migration assay also confirmed the improved proliferation and migration ability of the transfected HUVECs by these complexes. Furthermore, the in vitro and in vivo angiogenesis assay illustrated that these complexes could promote the tube formation ability of HUVECs. CONCLUSION: The above results indicated that the delivery efficiency of pZNF580 and its expression could be enhanced by introducing Hn sequence into gene carriers. The Hn sequence in REDV-TAT-NLS-Hn is beneficial for high gene transfection. These REDV and Hn functionalized TAT-NLS peptides are promising gene carriers in gene therapy.

From S,N-Heteroacene to Large Discotic Polycyclic Aromatic Hydrocarbons (PAHs): Liquid Crystal versus Plastic Crystalline Materials with Tunable Mechanochromic Fluorescence.

A novel type of discotic polycyclic aromatic hydrocarbon (PAH) based on an enlarged dibenzo[a,c]phenazine core has been developed. The large conjugated mesogenic core with increased dipole moment derived from S,N heteroatoms facilitates the formation of highly ordered columnar superstructures both in solution and bulk. Columnar mesophases, including liquid crystal (LC) and plastic crystal (PC) assemblies could form unprecedentedly based on the same PAH core. The cores are delicately modulated by the peripherical alkoxy chains. Both mesogens have mechanochromic fluorescent (MCF) character, which is also structure dependent and correlated with the different mesophase formation. For the first time, MCF properties can be realized in such a large conjugated mesogenic system.

Ionic Self-Assembled Derivative of Tetraphenylethylene: Synthesis, Enhanced Solid-State Emission, Liquid-Crystalline Structure, and Cu2+ Detection Ability.

A novel tetraphenylethylene complex composed of 4',4'',4''',4''''-(ethene-1,1,2,2-tetrayl)tetrabiphenyl-4-carboxylic acid (H4 ETTC) and dimethyldioctadecylammonium bromide (DOAB) with enhanced solid-state emission is designed and synthesized through an ionic self-assembly (ISA) strategy. The aggregation-induced emission property, phase behavior, and supramolecular structure of the complex are characterized by a combination of experimental measurements. The experimental results reveal that the ISA complex can self-assemble into an ordered helical supramolecular structure with enhanced luminescent properties, although the ETTC cores possess extensive conjugation and high rigidity. Due to the prolonged conjugation length, the fluorescence quantum yield of ETTC-DOAB is boosted to 66 %. Moreover, it is demonstrated that assemblies of the ISA complex are an effective sensor for Cu2+ . Owing to the disassembly modulation of ETTC-DOAB aggregations, the fluorescence emission of the assemblies can be selectively and sensitively quenched by Cu2+ , with a detection limit as low as 12.6 nm. The enhanced emission efficiency, in combination with the liquid crystallinity and superior sensing performance to Cu2+ , make the ETTC-DOAB complex a potential candidate for the fabrication of a luminescent device and chemosensor for Cu2+ detection.

Core/Shell Gene Carriers with Different Lengths of PLGA Chains to Transfect Endothelial Cells.

In order to improve the transfection efficiency and reduce the cytotoxicity of gene carriers, many strategies have been used to develop novel gene carriers. In this study, five complex micelles (MSP(2 k), MSP(4 k), MSP(6 k), MSP(8 k), and MSP(10 k)) were prepared from methoxy-poly(ethylene glycol)-b-poly(d,l-lactide-co-glycolide) (mPEG-b-PLGA) and sorbitol-poly(d,l-lactide-co-glycolide)-graft-PEI (sorbitol-PLGA-g-PEI, where the designed molecular weights of PLGA chains were 2 kDa, 4 kDa, 6 kDa, 8 kDa, and 10 kDa, respectively) copolymers by a self-assembly method, and the mass ratio of mPEG-b-PLGA to sorbitol-PLGA-g-PEI was 1/3. These complex micelles and their gene complexes had appropriate sizes and zeta potentials, and pEGFP-ZNF580 (pDNA) could be efficiently internalized into EA.hy926 cells by their gene complexes (MSP(2 k)/pDNA, MSP(4 k)/pDNA, MSP(6 k)/pDNA, MSP(8 k)/pDNA, and MSP(10 k)/pDNA). The MTT assay results demonstrated that the gene complexes had low cytotoxicity in vitro. When the hydrophobic PLGA chain increased above 6 kDa, the gene complexes showed higher performance than that prepared from short hydrophobic chains. Moreover, the relative ZNF580 protein expression levels in MSP(6 k)/pDNA, MSP(8 k)/pDNA, and MSP(10 k)/pDNA) groups were 79.6%, 71.2%, and 73%, respectively. These gene complexes could promote the transfection of endothelial cells, while providing important information and insight for the design of new and effective gene carriers to promote the proliferation and migration of endothelial cells.

Near-IR Absorbing J-Aggregate of an Amphiphilic BF2 -Azadipyrromethene Dye by Kinetic Cooperative Self-Assembly.

A new amphiphilic BF2 -azadipyrromethene (aza-BODIPY) dye 1 has been synthesized using a CuI -catalyzed "click" reaction. For this dye, two self-assembly pathways that lead to different type of J-aggregates with distinct near-infrared optical properties have been discovered. The metastable off-pathway product displays a broad, structureless absorption band while the thermodynamically stable on-pathway aggregate exhibits the characteristic spectral features of a J-aggregate, that is, red-shifted intense absorption band with significantly narrowed linewidth. The morphology and structure of the aggregates were studied by atomic force microscopy, transmission and scanning electron microscopy. The aggregation processes of 1 were investigated by temperature- and concentration-dependent UV/Vis spectroscopy and evaluated by models for cooperative self-assembly.

Multitargeting Gene Delivery Systems for Enhancing the Transfection of Endothelial Cells.

Gene therapy demonstrates promising prospects on cardiovascular diseases. However, nonviral gene delivery system has relatively low transfection efficiency, especially for endothelial cells (ECs). Herein, typical cell-penetrating peptide (TAT), nuclear localization signals (NLSs), and REDV functional peptide have been used to prepare multitargeting complexes. These complexes exhibit higher transfection efficiency owing to the targeting sequences of REDV and NLSs as well as the cell-penetrating function of TAT. The multifunction of the complexes provides high cell uptake, endo/lysosomal escape, and nucleus accumulation of the encapsulated DNA. Thus these multitargeting complexes can provide a potential platform for gene delivery, especially for EC transfection.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications.

Surface modification and endothelialization of vascular biomaterials are common approaches that are used to both resist the nonspecific adhesion of proteins and improve the hemocompatibility and long-term patency of artificial vascular grafts. Surface modification of vascular grafts using hydrophilic poly(ethylene glycol), zwitterionic polymers, heparin or other bioactive molecules can efficiently enhance hemocompatibility, and consequently prevent thrombosis on artificial vascular grafts. However, these modified surfaces may be excessively hydrophilic, which limits initial vascular endothelial cell adhesion and formation of a confluent endothelial lining. Therefore, the improvement of endothelialization on these grafts by chemical modification with specific peptides and genes is now arousing more and more interest. Several active peptides, such as RGD, CAG, REDV and YIGSR, can be specifically recognized by endothelial cells. Consequently, graft surfaces that are modified by these peptides can exhibit targeting selectivity for the adhesion of endothelial cells, and genes can be delivered by targeting carriers to specific tissues to enhance the promotion and regeneration of blood vessels. These methods could effectively accelerate selective endothelial cell recruitment and functional endothelialization. In this review, recent developments in the surface modification and endothelialization of biomaterials in vascular tissue engineering are summarized. Both gene engineering and targeting ligand immobilization are promising methods to improve the clinical outcome of artificial vascular grafts.

Correction: Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications.

Correction for 'Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications' by Xiangkui Ren et al., Chem. Soc. Rev., 2015, DOI: .

Aqueous self-assembly of a charged BODIPY amphiphile via nucleation-growth mechanism.

A new amphiphilic boron-dipyrromethene (BODIPY) dye 1 with a hydrophobic wedge at the meso-position and two hydrophilic cationic moieties at boron was synthesized. Temperature- and concentration-dependent UV/Vis spectroscopic studies in water were conducted to explore the self-assembly process of the dye. Detailed analysis of the data using two different models (developed by Van der Schoot et al. and Goldstein et al. respectively) for cooperative supramolecular polymerization indicates distinctly a nucleation-growth mechanism of the aggregation of dye 1 and the nucleus size (ca. 12-18 molecules) and a cooperativity factor (ca. 0.01) could be derived. Further investigation by transmission electron microscopy, scanning confocal microscopy, and X-ray diffraction revealed a unique vesicular morphology of the aggregates with multilamellar wall structure. Meanwhile, these dye vesicles exhibit unique optical characteristics, i.e. red-shifted sharp absorption band, narrowed emission linewidth, and increase in fluorescence quantum yield, as compared with the monomeric dye.

Electrospun scaffolds of silk fibroin and poly(lactide-co-glycolide) for endothelial cell growth.

Electrospun scaffolds of silk fibroin (SF) and poly(lactide-co-glycolide) (PLGA) were prepared to mimic the morphology and chemistry of the extracellular matrix. The SF/PLGA scaffolds were treated with ethanol to improve their usability. After ethanol treatment the scaffolds exhibited a smooth surface and uniform fibers. SF transformed from random coil conformation to ß-sheet structure after ethanol treatment, so that the SF/PLGA scaffolds showed low hydrophilicity and dissolving rate in water. The mechanical properties and the hydrophilicity of the blended fibrous scaffolds were affected by the weight ratio of SF and PLGA. During degradation of ethanol-treated SF/PLGA scaffolds in vitro, the fibers became thin along with the degradation time. Human umbilical vein endothelial cells (HUVECs) were seeded onto the ethanol-treated nanofibrous scaffolds for cell viability, attachment and morphogenesis studies. These SF/PLGA scaffolds could enhance the viability, spreading and attachment of HUVECs. Based on these results, these ethanol-treated scaffolds are proposed to be a good candidate for endothelial cell growth.