Release characteristics of cisplatin chitosan microspheres and effect of containing chitin

To increase cisplatin (CDDP) content, to suppress burst effect during the initial phase of drug release, and to improve the capacity of the system for sustained release, we prepared various types of CDDP chitosan microspheres incorporating chitin and investigated the content of CDDP and its in vitro release kinetics from these microspheres. The results of this study showed that the CDDP content increased with increasing chitosan concentration and that the incorporation of chitin in the carrier matrix produced a more pronounced increase in drug content. The addition of chitin also led to inhibition of the initial burst effect. The rate of CDDP release reduced with increasing concentration of chitosan: that is, the 50% CDDP release time was about 0.5 h with the microspheres prepared with 1.0% of chitosan and about 4.5 h with those prepared with 5.0% of chitosan, indicating about nine-fold prolongation. The addition of chitin further resulted in retardation of the rate of CDDP release. Meanwhile, our chitosan microspheres were shown to undergo enzymatic degradation by lysozymes.     

Thermally Stable Super Ionic Conductor from Carbon Sphere Oxide

A highly stable proton conductor has been developed from carbon sphere oxide (CSO). Carbon sphere (CS) generated from sucrose was oxidized successfully to CSO using Hummers’ graphite oxidation technique. At room temperature and 90 % relative humidity, the proton conductivity of thin layer CSO on microsized comb electrode was found to be 8.7×10^?3 S cm^?1, which is higher than that for a similar graphene oxide (GO) sample (3.4×10^?3 S cm^?1). The activation energy (E_a) of 0.258 eV suggests that the proton is conducted through the Grotthuss mechanism. The carboxyl functional groups on the CSO surface are primarily responsible for transporting protons. In contrast to conventional carbon‐based proton conductors, in which the functional groups decompose around 80 °C, CSO has a stable morphology and functional groups with reproducible proton conductivity up to 400 °C. Even once annealed at different temperatures at high relative humidity, the proton conductivity of CSO remains almost unchanged, whereas significant change is seen with a similar GO sample. After annealing at 100 and 200 °C, the respective proton conductivity of CSO was almost the same, and was about ～50 % of the proton conductivity at room temperature. Carbon‐based solid electrolyte with such high thermal stability and reproducible proton conductivity is desired for practical applications. We expect that a CSO‐based proton conductor would be applicable for fuel cells and sensing devices operating under high temperatures.     

Organocatalytic Enantioselective Nucleophilic Alkynylation of Allyl Fluorides Affording Chiral Skipped Ene‐ynes

Asymmetric methods for preparation of chiral alkynyl‐containing compounds are in extremely high demand in many sectors of chemical research. In this work, we report the discovery of a general organocatalytic enantioselective alkynylation based on the idea of Si/F activation of the allylic C?F bond. This approach features reasonably broad substrate scope, functional group tolerance, and relatively neutral, mild, and operationally convenient reaction conditions; all of which bode well for the synthetic value of the discovered method. In particular, this method provides unique chiral skipped 1,4‐ene‐ynes having two kinds of versatile functional groups.     

Thermodynamic Control of Intramolecular Singlet Fission and Exciton Transport in Linear Tetracene Oligomers

We newly synthesized a series of homo- and hetero-tetracene (Tc) oligomers to propose a molecular design strategy for the efficient exciton transport in linear oligomers by promoting correlated triplet pair (TT) dissociation and controlling sequential exciton trapping process of individual doubled triplet excitons (T+T) by intramolecular singlet fission. First, entropic gain effects on the number of Tc units are examined by comparing Tc-homo-oligomers [(Tc)_n: n=2, 4, 6]. Then, a comparison of (Tc)_n and Tc-hetero-oligomer [TcF₃-(Tc)₄-TcF₃] reveals the vibronic coupling effect for entropic gain. Observed entropic effects on the T+T formation indicated that the exciton migration is rationalized by number of possible TT states increased both by increasing the number of Tc units and by the vibronic levels at the terminal TcF₃ units. Finally, we successfully observed high-yield exciton trapping process (trapped triplet yield: Φ_TrT=176 %).     

Conformer-selective Photodynamics of TrpH+−H2O

The photodynamics of protonated tryptophan and its mono hydrated complex TrpH⁺−H₂O has been revisited. A combination of steady-state IR and UV cryogenic ion spectroscopies with picosecond pump-probe photodissociation experiments sheds new lights on the deactivation processes of TrpH⁺ and conformer-selected TrpH⁺−H₂O complex, supported by quantum chemistry calculations at the DFT and coupled-cluster levels for the ground and excited states, respectively. TrpH⁺ excited at the band origin exhibits a transient of less than 100 ps, assigned to the lifetime of the excited state proton transfer (ESPT) structure. The two experimentally observed conformers of TrpH⁺−H₂O have been assigned. A striking result arises from the conformer-selective photodynamics of TrpH⁺−H₂O, in which a single water molecule inserted in between the ammonium and the indole ring hinders the barrierless ESPT reaction responsible for the ultra-fast deactivation process observed in the other conformer and in bare TrpH⁺.     

Salt-induced thickening and gelation of a poly(carboxylate) having three kinds of hydroxyl groups

A salt-induced physical gelation was found for the aqueous solution of poly(carboxylate)s having three kinds of hydroxyl groups, i.e., primary, tertiary and one on a hemiacetal ring. The gelation point (critical salt concentration) was positively correlated with the content of the hemiacetal component, while the previously confirmed hydrogen bond between the hemiacetal OH and –COO⁻ group does not seem to essentially contribute to the physical gelation. Above a critical polymer concentration, the solution viscosity was first decreased and then increased with increasing NaCl concentration, leading to gelation. However, below the critical polymer concentration, the viscosity decreased. These different behaviors of the solution viscosity depending on the polymer concentration were ascribed to a preferential promotion of intermolecular or intramolecular hydrogen bonds among the hemiacetal OH groups above and below the critical polymer concentration, respectively.     

Self-assembly of ionic liquid (BMI-PF6)-stabilized gold nanoparticles on a silicon surface: chemical and structural aspects

Ultrafine monodisperse gold nanoparticles (AuNPs) were synthesized by an elegant sputtering of gold onto 1- n-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF(6)) ionic liquid. It was found that the BMI-PF(6) supramolecular aggregates were loosely coordinated to the gold nanoparticles and were replaceable with thiol molecules. The self-assembly of BMI-PF(6)-stabilized AuNPs onto a (3-mercaptopropyl)trimethoxysilane (MPS)-functionalized silicon surface in 2D arrays, followed by dodecanethiol (DDT) treatment, have been demonstrated using X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and contact angle measurements. DDT treatment of tethered AuNPs revealed two types of interactions between AuNPs and the MPS-functionalized surface: (a) AuNPs anchor through Au-S chemisorption linkage resulting in strong immobilization and (b) some of the AuNPs are supported by physisorption, driven by BMI-PF(6). The attachment of these particles remains unchanged with sonication. The replacement of BMI-PF(6) aggregates from physisorbed AuNPs with DDT molecules advances the dilution of their interaction with the MPS-functionalized surface, and they subsequently detach from the silicon surface. The present finding is promising for the immobilization of ionic liquid-stabilized nanoparticles, which is very desirable for electronic and catalytic device fabrication. Additionally, these environmentally friendly AuNPs are expected to replace conventional citrate-stabilized AuNPs.     

Downregulation of two isoforms of ubiquitin carboxyl-terminal hydrolase isozyme L1 correlates with high metastatic potentials of human SN12C renal cell carcinoma cell clones

Proteomic differential display analysis was performed on human renal cell carcinoma cell SN12C clones having different metastatic potentials by using 2-DE and LC-MS/MS. The SN12C cell clones were SN12C parent cell line, SN12C-clone 2, SN12C-clone 4, and SN12C-PM6. The SN12C parent cell line was established from an HRCC surgical specimen. SN12C-clone 4 has lower, and SN12C-clone 2 and SN12C-PM6 have higher metastatic potential than SN12C parent cells. We found eight protein spots whose expression level was different between low metastatic clones and high metastatic clones. The protein expression of three appeared to be higher in high metastatic clones than low metastatic clones, and that of other five protein spots appeared to be lower in high metastatic clones than low metastatic clones. These spots were selected, digested and analyzed by LC-MS/MS analysis, and they were identified by peptide sequencing tag. In high metastatic potential clones, two isoforms of ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCH-L1) were downregulated. These results suggest that UCH-L1 expression seems to be associated with the metastatic potential of HRCC SN12C cell clones.