Effect of Substituents in Mussel-inspired Surface Primers on their Oxidation and Priming Efficiency

N-Alkylation of Dopamine and Its Impact on Surface Coating Properties

Surface coating with dopamine (DA) has received significant attention over the past decade due to its compatibility with other surface coating techniques and versatility, making it applicable to solid surfaces regardless of substrate and shape. Much effort has been made to elucidate the origin of its surface coating capability, and as a result, many important factors affecting the coating properties have been determined. For example, it has been reported that the length of the carbon chain between catechol and amino groups, the attachment of specific functional groups to the catechol ring and amino group, and the replacement of the amino group with another functional group can affect the surface coating properties of DA. Despite these various attempts, there are still many factors that remain unknown. In this study, we investigate the effect of N-alkylation on DA coating. N-Ethyl-DA, N-propyl-DA, and N-isopropyl-DA are newly synthesized through simple organic reactions, and the coating efficiency of DA derivatives is compared with nucleophilicity and steric bulkiness. As a result, the coating efficiency of N-ethyl-DA and N-propyl-DA is lower than for pristine DA and N-methyl-DA, but it is possible to coat solid surfaces with alkyl-functionalized DA. In contrast, the coating with sterically bulky N-isopropyl-DA is almost unsuccessful.

Endogenous Photosensitizers in Human Skin

Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.

Effect of N-Methylation on Dopamine Surface Chemistry

Dopamine (DA) surface chemistry has received significant attention because of its applicability in a wide range of research fields and the ability to graft functional molecules onto numerous solid surfaces. Various DA derivatives have been newly synthesized to identify key factors affecting the coating efficiency and to advance the coating system development. The oxidation of catechol into quinone followed by internal cyclization via the nucleophilic attack of primary amine is crucial for DA-based surface coating. Thus, it is expected that the amine group's nucleophilicity control directly affects the coating efficiency. However, it has not been systematically investigated, and most studies have been conducted with the focus on the transformation of amines into amides, despite such approaches decreasing the coating efficiency; the nitrogen in amides is less nucleophilic than that in free amines. In this study, we investigated the effect of N-alkylation on dopamine surface chemistry. N,N-Dimethyldopamine (DMDA) was newly synthesized, and the coating efficiency was systematically compared with DA and N-methyldopamine (MDA). DA N-monomethylation improved the coating rate by increasing the nitrogen nucleophilicity, whereas N,N-dimethylation dramatically decreased the DA surface coating property. In addition, MDA remained capable of universal surface coating and secondary reactions using the surface catechols. This study provides opportunities for developing coating materials with advanced functions and an improved coating rate.