Quantitative Spermidine Detection in Cosmetics using an Organic Transistor-Based Chemical Sensor.

Spermidine is an essential biomarker related to antiaging. Although the detection of spermidine levels is in high demand in life science fields, easy-to-use analytical tools without sample purification have not yet been fully established. Herein, we propose an organic field-effect transistor-based chemical sensor for quantifying the spermidine concentration in commercial cosmetics. An extended-gate structure was employed for organic field-effect transistor (OFET)-based chemical sensing in aqueous media. A coordination-bond-based sensing system was introduced into the OFET device to visualize the spermidine detection information through changes in the transistor characteristics. The extended-gate-type OFET has shown quantitative responses to spermidine, which indicates sufficient detectability (i. e., the limit of detection for spermidine: 2.3 µM) considering actual concentrations in cosmetics. The applicability of the OFET-based chemical sensor for cosmetic analysis was validated by instrumental analysis using high-performance liquid chromatography. The estimated recovery rates for spermidine in cosmetic ingredient products (108-111 %) suggest the feasibility of cosmetic analysis based on the OFET-based chemical sensor.

Tetrazolo[1,5-a]pyridine-Containing π-Conjugated Systems: Synthesis, Properties, and Semiconducting Characteristics.

The incorporation of an electron-accepting unit into π-conjugated systems is an important approach to modulate the physical properties of such molecules. To investigate the potential of tetrazolo[1,5-a]pyridine as an electron-accepting unit, a series of diarylated tetrazolo[1,5-a]pyridine derivatives was synthesized by treating the corresponding diarylated pyridine N-oxide with diphenylphosphoryl azide. Thermogravimetric analyses of these molecules indicated that they possessed good thermal stability. The bithiophene-substituted tetrazolo[1,5-a]pyridine compound showed stable transistor characteristics under repeated bias conditions.

"Chiral perturbation factor" approach reveals importance of entropy term in stereocontrol of the 2,4-pentanediol-tethered reaction.

The stereocontrol mechanism of the 2,4-pentanediol (PD)-tethered reaction was studied in detail using a reaction system consisting of phenyl and rhodium carbenoid moieties. Different tethers were examined to analyze the effects of the methyl groups on the PD tether. Among the reactions with these tethers, the PD tether achieves an unmeasurably high stereoselectivity in a diastereomeric ratio of >500. Another tether showing a high but measurable stereoselectivity in a ratio of 41 is mostly controlled by the entropy term. To clarify the role of the methyl groups on the chiral tethers, which are the origin of the stereocontrol, the "chiral perturbation factor" is introduced. This parameter is defined as the rate of a chiral reaction relative to that of an achiral reference reaction. By analyzing the temperature dependence of the chiral perturbation factors for different chiral-tethered reactions, high potentials of the PD-tethered reaction in its stereocontrol are concluded to be due to the entropy term.