Cysteine and pH-responsive hydrogel based on a saccharide derivative with an aldehyde group.

For the development of chemoresponsive hydrogel, a new saccharide-derived hydrogelator 1 [methyl-4,6-O-(4'-aldehydephenylidene)-alpha-D-glucopyranoside] was synthesized and characterized. The resulting hydrogel not only shows thermal responsiveness but also exhibits cysteine and pH responsiveness due to the presence of aldehyde and acetal groups in 1. The release of guest molecules from the hydrogel of 1 was examined by employing compound 2 (fluorescein disodium) and compound 3 [methyl-4,6-O-(2'-pyrenylidene)-alpha-D-glucopyranoside] as guest molecules. The results indicate that the release of compound 2 from the hydrogel of 1 is controlled by the diffusion process, while the release of compound 3 from the hydrogel of 1 is facilitated by the presence of cysteine. These results demonstrate (1) the proof of principle to design chemoresponsive gels by incorporating reactive groups into the gelators and (2) it is possible to stimulate the release of guest molecules from hydrogels upon addition of reactive chemicals by manipulating the intermolecular interactions among the hydrogelators and guest molecules.

Aggregation-Induced Emission Nanoparticles Encapsulated with PEGylated Nano Graphene Oxide and Their Applications in Two-Photon Fluorescence Bioimaging and Photodynamic Therapy in Vitro and in Vivo.

Aggregation-induced emission (AIE) nanoparticles have been shown promise for fluorescence bioimaging and photodynamic therapy due to the good combination of nanoparticles and organic dyes or photosensitizers. Among several kinds of AIE nanoparticles, those that are capsulated with nanographene oxides (NGO) are easy to make, size-tunable, and have proven to be very stable in deionized water. However, the stability in saline solution still needs improvement for further applications in chemical or biomedical fields, and the efficacy of photodynamic therapy using NGO-capsulate AIE photosensitizers has not been evaluated yet. Herein, we modified NGO with polyethylene glycol (PEG) to improve the stability of NGO-capsulated AIE nanoparticles in phosphate buffer saline. Furthermore, by combining this modification method with a dual-functional molecule which has both typical AIE property and photosensitizing ability, we performed both two-photon fluorescence bioimaging and photodynamic therapy in vitro and in vivo. Our work shows that AIE nanoparticles capsulated with PEGylated nanographene oxide can be a powerful tool for future bioimaging and photodynamic therapy applications.

Determination of H2O2-dependent generation of singlet oxygen from human saliva with a novel chemiluminescence probe.

Singlet oxygen (1O2) has been shown to play an important role in salivary defense system, but its generation process and level from human saliva remain uncertain due to the lack of a reliable detection method. We have previously reported 4,4'(5')-bis[2-(9-anthryloxy)ethylthio]tetrathiafulvalene (BAET) as a novel chemiluminescence probe for 1O2. In this work, the probe is successfully used to characterize H2O2-dependent generation of 1O2 from saliva in real time. However, the yield of 1O2 is found to be very low, for example, being about 0.13 nmol from 200 microL saliva in the presence of 1 mM of hydrogen peroxide over a 5-s reaction period. The result is also compared with that obtained with another 1O2 probe 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-3-one (CLA), demonstrating that, besides 1O2, the other reactive oxygen species such as hydroxyl radical may also be involved in the reaction of saliva with H2O2. Furthermore, the present study shows that the selectivity of BAET for 1O2 is much higher than that of CLA and thus BAET is highly suited for the detection of 1O2 in the presence of other reactive oxygen species in biological systems.

Gold nanorods contained polyvinyl alcohol/chitosan nanofiber matrix for cell imaging and drug delivery.

Gold nanorods (AuNRs) that contained polyvinyl alcohol/chitosan (PVA/CS) hybrid nanofibers with dual functions are successfully fabricated by a simple electrospinning method. The results of transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy indicate that AuNRs are indeed encapsulated into the PVA/CS hybrid nanofibers. FTIR spectra results demonstrate that the chemical structures of PVA and CS are not affected when the AuNRs are introduced into the fibers. In vitro cytotoxicity test reveals that the hybrid fibers involving AuNRs are completely biocompatible. The as-prepared fibers can be used as a carrier for anticancer agent doxorubicin (DOX), and the drug is delivered into the cell nucleus. The AuNRs and DOX incorporated fibers are effective for inhibiting the growth and proliferation of ovary cancer cells and they can also be used as the cell imaging agent due to the unique optical properties of AuNRs. The nanofiber matrix combining two functions of cell imaging and drug delivery may be of great application potential in biomedical-related areas.

Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive.

Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene-conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions.

New organic semiconductors with imide/amide-containing molecular systems.

Due to their high electron affinities, chemical and thermal stabilities, π-conjugated molecules with imide/amide frameworks have received considerable attentions as promising candidates for high-performance optoelectronic materials, particularly for organic semiconductors with high carrier mobilities. The purpose of this Research News is to give an overview of recent advances in development of high performance imide/amide based organic semiconductors for field-effect transistors. It covers naphthalene diimide-, perylene diimide- and amide-based conjugated molecules and polymers for organic semiconductors.

Biocompatible core-shell electrospun nanofibers as potential application for chemotherapy against ovary cancer.

Polyvinyl alcohol/chitosan (PVA/CS) core-shell nanofibers are successfully fabricated by a simple coaxial electrospinning method, in which PVA forms the core layer and CS forms the shell layer. With the change of the feed ratio between PVA and CS, the surface morphology and the microstructures of the nanofibers are largely changed. The as-prepared core-shell fibers can be used as a carrier for doxorubicin (DOX) delivery. FT-IR analysis demonstrates that hydrogen bond between CS and PVA chains forms. The results of in vitro cytotoxicity test indicate that the core-shell fibers are completely biocompatible and the free DOX shows higher cytotoxicity than the DOX loaded nanofibers. The standing PVA/CS core-shell fibers remarkably promote the attachment, proliferation and spreading of human ovary cancer cells (SKOV3). Via observing by confocal laser scanning microscopy (CLSM), the DOX released from the fibers can be delivered into SKOV3 cell nucleus, which is significant for the future tumor therapy. And, the as-prepared fibers exhibit controlled release for loaded DOX via adjusting the feed ratio between PVA and CS, and the DOX loaded nanofibers are quite effective in prohibiting the SKOV3 ovary cells attachment and proliferation, which are potential for chemotherapy of ovary cancer.

Electrospun polyvinyl alcohol/chitosan composite nanofibers involving Au nanoparticles and their in vitro release properties.

Au nanoparticles (Au NPs) containing polyvinyl alcohol (PVA)/chitosan (CS) composite nanofibers were successfully prepared by a simple and effective method called electrospinning. Au NPs were firstly synthesized under a mild condition with CS as the reducing agent and stabilizer, followed by being mixed with PVA solution and then the resulting fibers were fabricated. The research indicated that Au NPs were indeed doped into the as-prepared fibers and the composite fibers well preserved Au NPs' unique optical characteristics. Additionally, with the adjustment of the weight ratios between PVA and CS, the diameter distribution and the morphology of the nanofibers were largely changed. In vitro drug release experiments demonstrated that the drug release rate can be conveniently controlled by changing the crosslink time.

Fluorescent polymeric micelles with tetraphenylethylene moieties and their application for the selective detection of glucose.

By linking TPE moieties that exhibit aggregation-induced (enhanced) emission to the amphiphilic copolymer 1, fluorescent micelles are prepared and characterized. The polymeric micelles exhibit relatively strong fluorescence which can be tuned by heating and cooling. By combining cascaded enzymatic (oxidation of D-glucose with GOx) and chemical (oxidation of I(-) by H(2) O(2) ) reactions, the fluorescent micelles of copolymer 1 are successfully utilized for the selective detection of D-glucose in aqueous solution. The influences of proteins (e.g., bovine serum albumin) and reductants (e.g., ascorbic acid) on this fluorescence detection of D-glucose are also discussed.

A simple method for preparation of Ag nanofilm used as active, stable, and biocompatible SERS substrate by using electrostatic self-assembly.

A new SERS-active Ag nanofilm on the surface of a glass slide has been prepared by a low-cost electrochemical strategy using polyvinyl alcohol (PVA) at a proper voltage. The two-dimensional morphology of the Ag nanofilm has been examined by scanning electron microscopy (SEM). The average size of the aggregated particles on the surface of the Ag nanofilm is up to ca. 200+/-50 nm, which is much larger than that of PVA-protected Ag colloidal nanoparticles (PVA-Ag CNPs, 45+/-8 nm). Meanwhile, many nano-scale regions with average sizes of ca. 300+/-50 nm are formed between the adjacent Ag nanoparticles. By the SERS measurements of human serum (HS) and hemoglobin (Hb), this Ag nanofilm is shown to be an excellent SERS substrate with good stability and biocompatibility. As the fabrication process of this SERS substrate is simple and inexpensive, this method may be used in large-scale preparation of substrates that have been widely applied in Raman analysis. In addition, this SERS-active Ag nanofilm can serve as a novel SERS substrate in biochemical analysis due to the biocompatibility.

Synthesis, characterization, and field-effect transistor properties of carbazolenevinylene oligomers: from linear to cyclic architectures.

Two cyclic carbazolenevinylene dimers 1 and 2 were synthesized by McMurry coupling reactions. A linear compound 3 was also prepared for comparison. Compounds 1-3 were fully characterized by means of NMR spectroscopy, HRMS, elemental analysis, and UV/Vis absorption spectroscopy. Quantum chemical simulations showed that the cyclic compounds possessed smaller HOMO-LUMO gaps and more extended conjugation. The UV/Vis absorption spectra of the cyclic compounds showed blueshifts compared with that of the linear compound 3. Time-dependent DFT (TD-DFT) analysis revealed that this was due to the different selection rules for molecules with cyclic and linear architectures. The cyclic conformation also significantly affected the molecular ordering in the solid state. The X-ray crystal structure of 1 showed partial pi-pi overlapping between the adjacent molecules. Thin films of 1-3 were fabricated by the vacuum-deposition method on Si/SiO(2) substrates. Multicrystalline thin films were obtained from compounds 1 and 2, but only amorphous thin films could be obtained for the linear compound 3. Another important difference between the cyclic and linear compounds was the reduced reorganization energy for the cyclic compounds. These two facts have resulted in improved field-effect transistor (FET) mobilities for the cyclic compounds compared with the linear compound. In addition, as the substrate temperature has a significant influence on the morphology and the degree of crystallinity of the thin films deposited, the device performance could be optimized by varying the substrate temperature. The FET devices based on 2 gave the highest mobility of 0.013 cm(2) V(-1) s(-1). The results showed that carbazole derivatives with cyclic structures might make better FETs.