A transdermal drug delivery system (TDDS) is a method that provides drug adsorption via the skin. TDDS could replace conventional oral administration and blood administration because it is easily accessible. However, it is still difficult to design efficient TDDS due to the high barrier property of skin covered with stratum corneum, which inhibits the permeation of drug molecules. Thus far, TDDS methods by applying physical stimuli such as microneedles and chemical stimuli such as surfactants have been actively developed. However, it has been hard to avoid inflammation at the administration site because these methods partially destroy the skin tissue. On the other hand, TDDS with nanocarriers minimizing damage to the skin tissues has emerged together with the development of nanotechnology in recent years. This review focuses on current trends in TDDS.

Peptide-based fibrous supramolecular assemblies represent an emerging class of biomaterials that can realize various bioactivities and structures. Recently, a variety of peptide fibers with attractive functions have been designed together with the discovery of many peptide-based self-assembly units. Cross-linking of the peptide fibers is a key strategy to improve the functions of these materials. The cross-linking of peptide fibers forming three-dimensional networks in a dispersion can lead to changes in physical and chemical properties. Hydrogelation is a typical change caused by cross-linking, which makes it applicable to biomaterials such as cell scaffold materials. Cross-linking methods, which have been conventionally developed using water-soluble covalent polymers, are also useful in supramolecular peptide fibers. In the case of peptide fibers, unique cross-linking strategies can be designed by taking advantage of the functions of amino acids. This review focuses on the current progress in the design of cross-linked peptide fibers and their applications.

Reactive oxygen species (ROS) are produced by cellular activities, such as metabolism and immune response, and play important roles in cell signaling and homeostasis. However, overproduced ROS causes irreversible damage to nucleic acids and membrane lipids, supporting genetic mutations and enhancing the effects of aging. Cells defend themselves against ROS using antioxidant systems based on redox-active sulfur and transition metals. Inspired by such biological redox-responsive systems, we developed methionine-containing self-assembling peptides. The Met-containing peptides formed hydrogels that underwent a gel-to-sol phase transition upon oxidation by H₂O₂, and the sensitivity of the peptides to the oxidant increased as the number of Met residues increased. The peptide containing three Met residues, the largest number of Met residues in our series of designed peptides, showed the highest sensitivity to oxidation and detoxification to protect cells from ROS damage. In addition, this peptide underwent a phase transition in response to H₂O₂ produced by an oxidizing enzyme. This study demonstrates the design of a supramolecular biomaterial that is responsive to enzymatically generated ROS and can protect cells against oxidative stress.

This article highlights the development of bioinspired supramolecular materials, i.e., synthetic extracellular matrices and membrane-deforming materials, mimicking the contact events seen at bio-interfaces for applications in injured brain regeneration and in vivo delivery.

Composite nanoparticles composed of anionic phospholipid of 1,2-dipalmitoyl- sn-glycero-3-phosphorylglycerol (DPPG) and resveratrol (Res) were successfully prepared by mixing them in water and a subsequent heating/cooling process. Small-sized DPPG-Res nanoparticles (<60 nm) could be prepared by ultrasonic fragmentation. Upon addition of size-controlled fluorescently labeled Res (^FLRes) nanoparticles stabilized with DPPG (DPPG-^FLRes) to rat skin tissue, ^FLRes molecules infiltrated into the epidermis layer permeating stratum corneum.