Tatsuo Maruyama

Predicting the surface wettability of copolymers remains challenging because interfacial properties are governed not only by bulk composition but also by physicochemical phenomena such as surface segregation and molecular reorientation. In this study, machine learning models were developed to predict the water contact angle (WCA) of dip‐coated methyl methacrylate (MMA)‐based copolymer surfaces using composition‐weighted molecular descriptors. A dataset of 135 copolymers prepared from 82 monomers under unified experimental conditions was constructed. Linear regression provided chemically interpretable relationships between molecular descriptors and WCA, whereas XGBoost achieved higher predictive accuracy. Chemical‐space visualization using uniform manifold approximation and projection (UMAP) enabled assessment of model applicability by distinguishing interpolation and extrapolation regions. Validation using newly synthesized copolymers showed that predictions were reliable within well‐represented chemical space, whereas systematic deviations were consistent with physicochemical phenomena such as surface segregation and molecular reorganization. These findings demonstrate that combining machine learning with chemical‐space analysis not only enables assessment of model applicability but also provides insight into the physicochemical limitations of descriptor based models for polymer surface design.

Some peptide sequences are known to interact with their enantiomers to form stereocomplexes. However, the sequence‐dependent conditions required for stereocomplexation have not been thoroughly elucidated. Here, we present a systematic investigation of peptide stereocomplexation using short tripeptides and their enantiomers. Stereocomplexation was evaluated by aggregate formation in mixed aqueous solutions, and single‐crystal X‐ray diffraction revealed racemic crystals. Stereocomplexation was driven by hydrophobic interactions between phenylalanine residues and electrostatic interactions involving lysine and the C‐terminus. Thermodynamic and structural features of the complexation were further elucidated by calorimetry, simulations, and fluorescence assays. On the basis of these insights, a D‐peptide (Ac‐fffakr5‐NH ₂ ) was rationally designed to target the –FFAE– motif of amyloid β42 (Aβ42), a pathological intrinsically disordered protein. This D‐peptide inhibited the fibrillization and cytotoxicity of Aβ42 in neuronal‐like cells, outperforming a clinical candidate, peptide drug RD2. These findings establish peptide stereocomplexation as a viable strategy for constructing sequence‐targeting ligands even against intrinsically disordered proteins.

The reducing capacity of biological and environmental aqueous samples is a key indicator of oxidative stress and redox balance. Thiol-containing compounds (biothiols) are essential in maintaining this balance within biological systems. In this study, we developed a paper-based analytical device (PAD) for the rapid and quantitative detection of biothiols in aqueous solutions and cell homogenates. The PAD uses a cysteine-specific fluorescent probe that generates a signal proportional to the biothiol concentration. Assay conditions and reaction kinetics were optimized to expand the dynamic range and lower the detection limit for cysteine (Cys). By incorporation of cystine, PAD enabled accurate quantification of other biothiols with high reproducibility and sensitivity. We validated the PAD using standard reducing agents and complex biological samples, demonstrating a strong correlation with the conventional spectroscopic method using 5,5'-dithiobis(2-nitrobenzoic acid). This cost-effective, portable, and user-friendly PAD offers a versatile solution for on-site and real-time redox monitoring, with potential applications in biomedical research, diagnostics, and environmental monitoring.

Organelle targeting is a useful approach in drug development for cancer therapy. Peptide amphiphiles are good candidates for targeting specific organelles because they can be engineered into a wide range of molecular structures, enabling customization for specific functional needs. We have developed a peptide amphiphile, C16‐(EY)3, that can respond to tyrosine kinase activity and undergo phosphorylation inside cancer cells. C16‐(EY)3 selectively induced apoptosis in cancer cells that overexpressed tyrosine kinase. The self‐assembly of peptide amphiphiles on the endoplasmic reticulum (ER) membrane reduced the ER membrane fluidity and triggered ER stress. The mechanism of the cancer cell death induced by C16‐(EY)3 was shown to involve phosphorylation by tyrosine kinase, ER stress induction, and the subsequent activation of caspase‐4, −12, and −9, which ultimately triggered apoptosis through the activation of caspase‐3 and −7. In vivo studies further validated the antitumor efficacy of C16‐(EY)3, as transcutaneous administration of the peptide amphiphile inhibited tumor growth in mice. This study elucidated the mechanism of apoptosis induced by the peptide amphiphile, indicating the potential of peptide amphiphiles as organelle‐targeting cancer therapeutics and providing a novel strategy for the development of selective and potent anticancer drugs.

Here, “direct click bonding” of solid materials is proposed, which is the direct bonding of solid surfaces via the formation of covalent bonds without any adhesive. The present study shows that the Cu‐free Huisgen 1,3‐dipolar cycloaddition reaction proceeds between solid surfaces displaying cyclooctyne and azide groups, and it achieved the strong bonding of dissimilar solid materials as a macroscopic reaction. The bonding strength obtained is sufficiently high for practical use, and the strength can be controlled by the surface density of the cyclooctyne groups. The click bonding reaction proceeds at ambient temperature in water, an organic solvent, air, and vacuum without a catalyst or a byproduct. The bonding strength is kept more than 2 years. The click bonding works for different types of substrate materials as long as alkyne and azide groups are displayed on their surfaces. The X‐ray photoelectron spectroscopy (XPS) measurements provide an evidence that the Cu‐free Huisgen 1,3‐dipolar cycloaddition reaction proceeds between the solid surfaces through the click bonding.

This study investigates the surface functionalization of plastic substrates through dip‐coating in azide‐functionalized polymer solutions, followed by a click reaction (i.e., strain‐promoted azide–alkyne cycloaddition). Acrylic, poly(ethylene terephthalate) (PET), and nylon substrates are dip‐coated with a series of polymers containing various azide groups grafted onto the poly(methyl methacrylate‐co‐hydroxyethyl methacrylate) backbone to examine structural effects on the surface density of clickable azide groups. X‐ray photoelectron spectroscopy and fluorescence spectroscopy confirm the subsequent click‐immobilization of cycloalkyne‐tagged fluorescein, which is quantified to calculate the surface density of clickable azide groups. Further investigations demonstrate that the surface density of azide groups can be controlled by manipulating the polymer ratio during dip‐coating, thus enabling the preparation of a linear surface gradient in terms of azide group density. Finally, the microcontact printing (µCP) method is employed to pattern the functionalized surfaces and quantify the functional molecules immobilized on the surface by µCP. This study highlights the adaptability of click chemistry and polymer coating techniques for the advanced functionalization of plastic surfaces for materials science and engineering applications.