Selective Formation of Small and Large Coordination Cages and Their Catalytic Differences.

Self-assembly of CuX2 (X- = BF4-, ClO4-, and CF3SO3-) with a new tridentate 5,5',5″-(((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(oxy))triisoquinoline (L) gives rise to single-crystal pairs consisting of small and large cages, [X@Cu2X2L4]X and [Cu6X12L8], respectively, via selection of solvents. In particular, the large cage is transformed into a small cage in acetonitrile above 50 °C. A significant difference in heterogeneous catechol oxidation catalysis between the small and large cages is observed. Such notable catechol-oxidation-catalytic effects can be explained by maintenance of the Cu···Cu distance at the catalytic center. This research is a direct systematic example of both cage-size control via solvent selection and the significance of the Cu···Cu distance in catechol oxidation catalysis with copper (Cu).

Crystals of Ni6L12 Ellipsoidal Tubes as Single-Crystal-to-Single-Crystal Adsorption Matrix: Penetrative Study of Self-Assembled Crystals vs Guest-Exchanged Crystals.

Informative similarities/differences between self-assembled and single-crystal-to-single-crystal (SCSC) guest-exchanged crystals based on both the molecular structure and adsorption nature are observed. The self-assembly of Ni(ClO4)2 with a dicyclopentyldi(pyridine-3-yl)silane bidentate ligand (L) in a mixture of toluene and acetonitrile gives rise to purple crystals consisting of double-stranded ellipsoidal tubes, [Ni6(ClO4)4(CH3CN)8L12]·8ClO4·4CH3CN·5C7H8. The coordinated acetonitriles as well as the solvates are removed at 170 °C to transform the purple crystals into blue crystals of [Ni(ClO4)2L2]n that return to the original crystals in the mixture of toluene and acetonitrile. Further, the toluene and acetonitrile solvates of the original crystals are replaced by o-, m-, and p-xylene isomers within 5 min in a SCSC manner. In the present study, SCSC xylene-exchanged crystals were compared with crystals obtained from direct self-assembly in a mixture of each xylene isomer and acetonitrile.

Directed Evolution of Near-Infrared Serotonin Nanosensors with Machine Learning-Based Screening.

In this study, we employed a novel approach to improve the serotonin-responsive ssDNA-wrapped single-walled carbon nanotube (ssDNA-SWCNT) nanosensors, combining directed evolution and machine learning-based prediction. Our iterative optimization process is aimed at the sensitivity and selectivity of ssDNA-SWCNT nanosensors. In the three rounds for higher serotonin sensitivity, we substantially improved sensitivity, achieving a remarkable 2.5-fold enhancement in fluorescence response compared to the original sequence. Following this, we directed our efforts towards selectivity for serotonin over dopamine in the two rounds. Despite the structural similarity between these neurotransmitters, we achieved a 1.6-fold increase in selectivity. This innovative methodology, offering high-throughput screening of mutated sequences, marks a significant advancement in biosensor development. The top-performing nanosensors, N2-1 (sensitivity) and L1-14 (selectivity) present promising reference sequences for future studies involving serotonin detection.

Coordinating nature of M6L12 double-stranded macrocycles: co-ligand competition of perchlorate, water, and acetonitrile depending on metal(II) ions.

Self-assembly of M(ClO4)2 (M(II) = Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) with dicyclopentyldi(pyridine-3-yl)silane (L) as a donor in a mixture of acetonitrile and toluene produces crystals consisting of M6L12 double-stranded macrocycles. The geometry around the M(II) cations is a typical octahedral arrangement, but the metallamacrocycles' outer axial coordination environment is sensitive to the M(II) cations. The conformation of the unique metallamacrocycles is informatively dependent on the nature of the coordination around the M(II) cations via subtle co-ligand competition among perchlorate anions, water, and acetonitrile. Both the coordinated acetonitriles and the solvate molecules of the crystals are removed at 170 °C, thereby transforming the crystals into new crystals that return to their original form in the mixture of toluene and acetonitrile. Catalytic oxidation of 3,5-di-tert-butylcatechol using [Cu6(ClO4)8(CH3CN)4L12]4ClO4·5C7H8 is much faster than those using the transformed product, [Cu(ClO4)2L2], and a simple mixture of Cu(ClO4)2 + L.

Antimicrobial Activities of Propolis in Poloxamer Based Topical Gels.

Propolis contains a group of compounds with various activities. However, their low solubility is a drawback for the development of pharmaceutical formulations. In this study, poloxamers as a solubilizer and gelling agent were evaluated to develop a topical antimicrobial formulation of propolis. The effects of poloxamer type and concentration on the propolis solubility, release rate, and antimicrobial activities were investigated. Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were the representative bacteria and fungi, respectively. At 5%, poloxamer 407 (P407) and poloxamer 188 (P188) enhanced the propolis solubility by 2.86 and 2.06 folds, respectively; at 10%, they were 2.81 and 2.59 folds, respectively. The micelle size in the P188 formulation increased in the presence of propolis, whereas there was no change in the P407 formulation. Release rates of propolis decreased with the P188 concentration increase, which was attributed to viscosity increase. Both P188 and P407 formulations showed antimicrobial activity against S. aureus in a time-kill kinetics assay. However, only the P188 formulation reduced the cell's numbers significantly against C. albicans, compared to the control. We speculate that P188 mixed micelles were more effective in releasing free active compounds to exhibit anti-microbial activity compared to the P407 micelles encapsulating the hydrophobic compounds in their cores. Propolis in P188 formulation is proposed as a potential topical antimicrobial agent based on its activity against both S. aureus and C. albicans.