Ultrathin and Smooth Pheomelanin-like Photoconductive Film.

This study introduces a facile method for the substrate-independent deposition of pheomelanin-like films, revealing unique and promising electrical characteristics. The conventional darkening of a dopamine solution at a basic pH was significantly delayed by the addition of l-cysteine, resulting in a distinctive temporal pattern: an initial quiescent period without apparent color change followed by an abrupt and explosive burst. Surprisingly, within the quiescent period, the deposition of ultrathin and smooth pheomelanin-like films was observed, in addition to rough and thick films formed after the burst. Regardless of thickness or texture, these films exhibited common chemical properties, including moisture-capturing capability and dark- and bright-state conductivities. Particularly noteworthy were consistent photocurrent responses under bias voltage across various pheomelanin-like films, which were not observed in polydopamine films, highlighting the influential role of l-cysteine addition. These findings present a novel avenue for the potential application of pheomelanin-like films in bioelectronics, emphasizing their distinct electrical characteristics and prompting further exploration into their intricate conductive mechanisms. The study contributes to advancing our understanding of melanin-based materials and their potential in diverse scientific and technological domains.

Fe-Catalyzed C-H Alkenylation of Dialkyl Anilines with Disulfonylethenes.

The oxidative alkenylation reaction of α-aminoalkyl C(sp3)-H bonds has been investigated with (E)-1,2-bis(sulfonyl)ethenes. The catalytic process of iron-polypyridyl complexes drives the single-electron oxidation of dialkyl anilines, resulting in the formation of α-aminoalkyl radical species. Subsequent cascades of radical addition and elimination reactions ensue, ultimately leading to the generation of sulfonylated allylic amine products. The utility of these products extends further, enabling the synthesis of multisubstituted heterocycles like pyrroles, pyrazines, and triazoles.

Catechol-Amyloid Interactions.

This review introduces multifaceted mutual interactions between molecules containing a catechol moiety and aggregation-prone proteins. The complex relationships between these two molecular species have previously been elucidated primarily in a unidirectional manner, as demonstrated in cases involving the development of catechol-based inhibitors for amyloid aggregation and the elucidation of the role of functional amyloid fibers in melanin biosynthesis. This review aims to consolidate scattered clues pertaining to catechol-based amyloid inhibitors, functional amyloid scaffold of melanin biosynthesis, and chemically designed peptide fibers for providing chemical insights into the role of the local three-dimensional orientation of functional groups in manifesting such interactions. These orientations may play crucial, yet undiscovered, roles in various supramolecular structures.

Rod-to-sphere elemental reconstruction of biocompatible Ag2Te-Ag4.53-Te3 nanoparticles for triple negative breast cancer photo-nano-therapy.

Silver nanoparticles (AgNPs) continue to be applied to agricultural and medical applications because of their antibacterial and antifungal effects. However, AgNPs are vulnerable to poisoning by oxidation or sulfidation, and unintentional toxicity can occur via leaching. Therefore, ensuring the stability of AgNPs for practical applications is considered an important requirement. In this study, we propose the solvothermal galvanic replacement of a Te nanorod (TeNR) template with a Ag precursor to manufacture highly stable and biocompatible Ag-Te nanoparticles (AgTeNPs). In addition to their high stability, AgTeNPs composed of Ag2Te-Ag4.53Te3 were evaluated as a nanotherapeutic agent enabled by their selective toxicity through metabolic degradation in breast cancer cells. It has been demonstrated that combinatorial treatment with hyperthermic cancer-cell ablation through photothermal conversion provides an effective cancer treatment in vitro and in vivo. The discovered new biocompatible Ag nanomaterials with innate anticancer effects are expected to be applied to various application fields.

Iron Catalysis of C(sp3)-H Azidation Using a Heteroarene Radical Cation Strategy.

The FeIII(phen)3 catalysis of the benzylic C(sp3)-H azidation of indoles has been investigated. The Fe(III) complex can selectively oxidize indoles to form arene radical cations, which are transformed into benzylic C(sp3) radical intermediates. This strategy exhibits a difference in reactivity between N-heteroarenes and benzene, which is difficult to achieve via direct hydrogen abstraction approaches. Various biorelevant azide precursors were constructed, highlighting the utility of this mild first-row transition-metal catalyst system.

Surface-facilitated formation of polydopamine and its implications in melanogenesis.

This manuscript examines influences of differently functionalized surfaces on the formation of solution-dispersed polydopamine (pDA). Glass vials functionalized with different functional groups provided a set of conditions with which the relationship between the area of active surface and the rate of pDA formation could be systematically studied. The results suggest that charged and polar surfaces accelerate pDA formation in solution, with the effect of -NH2 surfaces being exceptionally strong. In the vials, pDA formed as both forms of dispersions in solution and films at solid-liquid interface. Further analyses confirmed that both forms of pDA formed with -NH2 surfaces were chemically similar to conventional pDA synthesized without help of functional surfaces. Among short peptide-based amyloid fibers with defined surface functional groups, and those displaying lysines (-NH2) greatly accelerated the formation of pDA, consistent with the results of -NH2-functionalized vials. The results suggest that pDA formation may be facilitated by surface functional groups of solid-liquid interfaces, and have implications for the overlooked roles of amyloid fibers in biological melanogenesis.

Designed Amyloid Fibers with Emergent Melanosomal Functions.

Short peptides designed to self-associate into amyloid fibers with metal ion-binding ability have been used to catalyze various types of chemical reactions. This manuscript demonstrates that one of these short-peptide fibers coordinated with CuII can exhibit melanosomal functions. The coordinated CuII and the amyloid structure itself are differentially functional in accelerating oxidative self-association of dopamine into melanin-like species and in regulating their material properties (e.g., water dispersion, morphology, and the density of unpaired electrons). The results have implications for the role of functional amyloids in melanin biosynthesis and for designing peptide-based supramolecular structures with various emergent functions.

Intrinsic Peroxidase-Mimicking Ir Nanoplates for Nanozymatic Anticancer and Antibacterial Treatment.

The study of inorganic nanozymes to overcome the disadvantages of bio-enzymes, such as the requirement of optimized reaction conditions and lack of durability against environmental factors, is one of the most significant research topics at present. In this work, we comprehensively analyzed the intrinsic peroxidase-like activity of Ir-based nanoparticles, the biological and nanozymatic potentials of which have not yet been explored. These particles were synthesized by the galvanic replacement of Ag nanoplates with Ir. Through the confirmed peroxidase-like activity and hydrogen peroxide decomposition with free radical generation facilitated by these particles, the antibacterial and anticancer effects were successfully verified in vitro. The nanozyme-based therapeutic effect observed at concentrations at which these nanoparticles do not show cytotoxicity suggests that it is possible to achieve more precise and selective local treatment with these particles. The observed highly efficient peroxidase-like activity of these nanoparticles is attributed to the partially mixed composition of Ir-Ag-IrO2 formed through the galvanic replacement reaction in the synthetic process.

Antibacterial nanoparticles: enhanced antibacterial efficiency of coral-like crystalline rhodium nanoplates.

This paper deals with the newly found antibacterial efficiency of coral-like crystalline Rh nanoplates. Rh nanoplates with rough surface morphology synthesized by inverse-directional galvanic replacement exhibited highly enhanced antibacterial efficiency compared to Rh3+ ion and Rh nanospheres. The observed antibacterial efficiency was comparable to Ag nanoplates, a well-known anticancer nano-agent. Results clearly demonstrate that the composition and morphology of a nanostructure play significant roles in antibacterial effects.

Real-time tracking of the autophagy process in living cells using plasmonically enhanced Raman spectroscopy of fucoidan-coated gold nanoparticles.

To date, a variety of biological assays such as immunostaining, western blotting, enzyme-linked immunosorbent assay (ELISA), and flow cytometry have been used to analyze and trace important biological events and therapies. In addition to these techniques, the application of microscopic analytical techniques such as matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) mass spectrometry and Raman spectroscopy is increasing, allowing information to be obtained at the molecular level. In this study, we have conducted real-time tracking of autophagy, a cellular process that has recently been attracting significant attention. To achieve this purpose, we performed Raman spectroscopy on human oral squamous carcinoma cells (HSC3) incubated with bioactive molecule-modified plasmonic gold nanoparticles. The bioactive molecule-nanoparticle complexes were synthesized using fucoidan, a biopolymer that induces autophagy. By using this platform, it was possible to trace the entire autophagic process successively from cell introduction to autophagic apoptosis. This fusion of nanocomposites and spectroscopic techniques is expected to enable more complex biological processes to be pursued at the molecular level in the future.

Anomalously Rapid Tunneling: Charge Transport across Self-Assembled Monolayers of Oligo(ethylene glycol).

This paper describes charge transport by tunneling across self-assembled monolayers (SAMs) of thiol-terminated derivatives of oligo(ethylene glycol) (HS(CH2CH2O)nCH3; HS(EG)nCH3); these SAMs are positioned between gold bottom electrodes and Ga2O3/EGaIn top electrodes. Comparison of the attenuation factor (ß of the simplified Simmons equation) across these SAMs with the corresponding value obtained with length-matched SAMs of oligophenyls (HS(Ph)nH) and n-alkanethiols (HS(CH2)nH) demonstrates that SAMs of oligo(ethylene glycol) have values of ß (ß(EG)n = 0.29 ± 0.02 natom-1 and ß = 0.24 ± 0.01 Å-1) indistinguishable from values for SAMs of oligophenyls (ß(Ph)n = 0.28 ± 0.03 Å-1), and significantly lower than those of SAMs of n-alkanethiolates (ß(CH2)n = 0.94 ± 0.02 natom-1 and 0.77 ± 0.03 Å-1). There are two possible origins for this low value of ß. The more probable involves hole tunneling by superexchange, which rationalizes the weak dependence of the rate of charge transport on the length of the molecules of HS(EG)nCH3 using interactions among the high-energy, occupied orbitals associated with the lone-pair electrons on oxygen. Based on this mechanism, SAMs of oligo(ethylene glycol)s are good conductors (by hole tunneling) but good insulators (by electron and/or hole drift conduction). This observation suggests SAMs derived from these or electronically similar molecules are a new class of electronic materials. A second but less probable mechanism for this unexpectedly low value of ß for SAMs of S(EG)nCH3 rests on the possibility of disorder in the SAM and a systematic discrepancy between different estimates of the thickness of these SAMs.

Facile size-controlled synthesis of fucoidan-coated gold nanoparticles and cooperative anticancer effect with doxorubicin.

To conquer cancer, one of the most dangerous and common diseases faced by humanity, many therapeutic approaches have been researched and developed. Discovery of highly effective therapeutic molecules without side effects and novel strategies for their effective delivery are areas receiving recent global interest. Here, we describe a facile one-pot synthetic method for making gold nanoparticles coated with fucoidan, a natural product extracted from brown seaweed and a promising anticancer biopolymer. This nanoparticle formulation with well-controlled size distribution shows promise in enhancing the therapeutic and delivery efficacy. Moreover, stable surface modification of fucoidan coating followed by conjugation of doxorubicin through cleavable linkage significantly improved the anticancer effect. Fucoidan-coated gold nanoparticles containing doxorubicin exhibited more greatly enhanced anticancer effect than any other related platform following fucoidan-based cancer treatment adopting the nanoparticle integrated system.

Magnetotactic molecular architectures from self-assembly of ß-peptide foldamers.

The design of stimuli-responsive self-assembled molecular systems capable of undergoing mechanical work is one of the most important challenges in synthetic chemistry and materials science. Here we report that foldectures, that is, self-assembled molecular architectures of ß-peptide foldamers, uniformly align with respect to an applied static magnetic field, and also show instantaneous orientational motion in a dynamic magnetic field. This response is explained by the amplified anisotropy of the diamagnetic susceptibilities as a result of the well-ordered molecular packing of the foldectures. In addition, the motions of foldectures at the microscale can be translated into magnetotactic behaviour at the macroscopic scale in a way reminiscent to that of magnetosomes in magnetotactic bacteria. This study will provide significant inspiration for designing the next generation of biocompatible peptide-based molecular machines with applications in biological systems.

Tissue-based metabolic labeling of polysialic acids in living primary hippocampal neurons.

The posttranslational modification of neural cell-adhesion molecule (NCAM) with polysialic acid (PSA) and the spatiotemporal distribution of PSA-NCAM play an important role in the neuronal development. In this work, we developed a tissue-based strategy for metabolically incorporating an unnatural monosaccharide, peracetylated N-azidoacetyl-D-mannosamine, in the sialic acid biochemical pathway to present N-azidoacetyl sialic acid to PSA-NCAM. Although significant neurotoxicity was observed in the conventional metabolic labeling that used the dissociated neuron cells, neurotoxicity disappeared in this modified strategy, allowing for investigation of the temporal and spatial distributions of PSA in the primary hippocampal neurons. PSA-NCAM was synthesized and recycled continuously during neuronal development, and the two-color labeling showed that newly synthesized PSA-NCAMs were transported and inserted mainly to the growing neurites and not significantly to the cell body. This report suggests a reliable and cytocompatible method for in vitro analysis of glycans complementary to the conventional cell-based metabolic labeling for chemical glycobiology.

Generation of patterned neuronal networks on cell-repellant poly(oligo(ethylene glycol) methacrylate) films.

The utilization of non-biofouling poly(oligo(ethylene glycol) methacrylate) (pOEGMA) films as a background material for the generation of neuronal patterns is reported here. Our previously reported method, which was surface-initiated, atom transfer radical polymerization of OEGMA, and subsequent activation of terminal hydroxyl groups of pOEGMA with disuccinimidyl carbonate, was employed for the generation of activated pOEGMA films on glass. Poly-L-lysine was then microcontact-printed onto the activated polymer films, followed by backfilling with poly(ethylene glycol) moieties. E18 hippocampal neurons were cultured on the chemically patterned substrate, and the resulting neuronal networks were analyzed by phase-contrast microscopy and whole-cell patch clamp method. The results indicated that the pOEGMA films played an important role in the generation of good-quality neuronal patterns for up to two weeks without any negative effects to neurons.