Atomically precise vacancy-assembled quantum antidots

Patterning antidots, which are regions of potential hills that repel electrons, into well-defined antidot lattices creates fascinating artificial periodic structures, leading to anomalous transport properties and exotic quantum phenomena in two-dimensional systems. Although nanolithography has brought conventional antidots from the semiclassical regime to the quantum regime, achieving precise control over the size of each antidot and its spatial period at the atomic scale has remained challenging. However, attaining such control opens the door to a new paradigm, enabling the creation of quantum antidots with discrete quantum hole states, which, in turn, offer a fertile platform to explore novel quantum phenomena and hot electron dynamics in previously inaccessible regimes. Here we report an atomically precise bottom-up fabrication of a series of atomic-scale quantum antidots through a thermal-induced assembly of a chalcogenide single vacancy in PtTe2. Such quantum antidots consist of highly ordered single-vacancy lattices, spaced by a single Te atom, reaching the ultimate downscaling limit of antidot lattices. Increasing the number of single vacancies in quantum antidots strengthens the cumulative repulsive potential and consequently enhances the collective interference of multiple-pocket scattered quasiparticles inside quantum antidots, creating multilevel quantum hole states with a tunable gap from the telecom to far-infrared regime. Moreover, precisely engineered quantum hole states of quantum antidots are geometry protected and thus survive on oxygen substitutional doping. Therefore, single-vacancy-assembled quantum antidots exhibit unprecedented robustness and property tunability, positioning them as highly promising candidates for advancing quantum information and photocatalysis technologies.

Numerical package for QFT calculations of defect-induced phenomena in graphene

We introduce a computationally efficient method based on the path integral formalism to describe defect-modified graphene. By taking into account the entire Brillouin zone, our approach respects the lattice symmetry and can be used to investigate both short-range and long-range effects. The proposed method's key advantage is that the computational complexity does not increase with the system size, scaling, instead, with the number of defects. Our aim is to make the quantum-field calculations in graphene accessible to the experimental community. We demonstrate our method's capabilities by exploring the well-known graphene-mediated Ruderman-Kittel-Kasuya-Yoshida interaction and by performing a detailed study of the atomic collapse in the presence of defects.

Electronic Self-Passivation of Single Vacancy in Black Phosphorus via Ionization

We report that monoelemental black phosphorus presents a new electronic self-passivation scheme of single vacancy (SV). By means of low-temperature scanning tunneling microscopy and noncontact atomic force microscopy, we demonstrate that the local reconstruction and ionization of SV into negatively charged SV^{-} leads to the passivation of dangling bonds and, thus, the quenching of in-gap states, which can be achieved by mild thermal annealing or STM tip manipulation. SV exhibits a strong and symmetric Friedel oscillation (FO) pattern, while SV^{-} shows an asymmetric FO pattern with local perturbation amplitude reduced by one order of magnitude and a faster decay rate. The enhanced passivation by forming SV^{-} can be attributed to its weak dipolelike perturbation, consistent with density-functional theory numerical calculations. Therefore, self-passivated SV^{-} is electrically benign and acts as a much weaker scattering center, which may hold the key to further enhance the charge mobility of black phosphorus and its analogs.

Visualizing designer quantum states in stable macrocycle quantum corrals

Creating atomically precise quantum architectures with high digital fidelity and desired quantum states is an important goal in a new era of quantum technology. The strategy of creating these quantum nanostructures mainly relies on atom-by-atom, molecule-by-molecule manipulation or molecular assembly through non-covalent interactions, which thus lack sufficient chemical robustness required for on-chip quantum device operation at elevated temperature. Here, we report a bottom-up synthesis of covalently linked organic quantum corrals (OQCs) with atomic precision to induce the formation of topology-controlled quantum resonance states, arising from a collective interference of scattered electron waves inside the quantum nanocavities. Individual OQCs host a series of atomic orbital-like resonance states whose orbital hybridization into artificial homo-diatomic and hetero-diatomic molecular-like resonance states can be constructed in Cassini oval-shaped OQCs with desired topologies corroborated by joint ab initio and analytic calculations. Our studies open up a new avenue to fabricate covalently linked large-sized OQCs with atomic precision to engineer desired quantum states with high chemical robustness and digital fidelity for future practical applications.

Cosmetic benefits of a novel biomimetic lamellar formulation containing niacinamide in healthy females with oily, blemish-prone skin in a randomized proof-of-concept study

OBJECTIVE

A randomized study was designed to evaluate the potential cosmetic benefit of a biomimetic, niacinamide-containing moisturizing cream in oily, blemish-prone skin.

METHODS

Healthy adult women with oily, blemish-prone skin were randomized to one of three treatment groups: test, control, or positive control. In the test group, subjects used the test product (containing 4% niacinamide), plus the standard cleanser (Simple® Kind to Skin Moisturizing Facial Wash). In the control group, subjects received no moisturizer but used the standard cleanser. In the positive control group, subjects used Vivatinell Acnecinamide^® Gel Cream (containing 4% niacinamide) as a moisturizer and Neutrogena Visibly Clear^® Spot Clearing Facial Wash (containing 2% salicylic acid) as a cleanser. The positive control regimen was included to provide a comparison for estimates of effect size. The primary objective was to evaluate skin moisturization as a change from baseline in corneometer values at 8 h for the test regimen vs. the control regimen. Analysis of covariance was applied for the primary efficacy analysis.

RESULTS

A total of 132 subjects were randomized with 44 included in each treatment group. A significant difference was observed in the primary endpoint for the test regimen compared with the control regimen (least-squares mean difference [95% CI]: 3.12 [0.68, 5.56], P = 0.0128). A trend was observed in favour of the positive control regimen compared with the control regimen. Secondary measurements of moisturization supported the primary efficacy outcome. Assessment of blemishes showed a significant difference between the test regimen vs. the control regimen for change from baseline in mean total blemish count at Week 8 (least-squares mean difference [95% CI]: -1.80 [-3.41, -0.19], P = 0.0290). No statistical comparisons between the positive control group and the test group were performed.

CONCLUSION

This study provides proof-of-concept evidence that a novel lamellar lipid moisturizer containing niacinamide, in combination with a standard cleanser, can help moisturize the skin and provide an overall improvement in the complexion appearance of people with blemish-prone skin.

STUDY REGISTRATION

NCT03093181.

Cosmetic benefit of a biomimetic lamellar cream formulation on barrier function or the appearance of fine lines and wrinkles in randomized proof-of-concept clinical studies

Objective

Two studies were designed to evaluate the potential cosmetic benefit of a biomimetic, niacinamide‐containing moisturizing cream for the first time in humans.

Methods

In both studies, healthy women were randomized to use two treatments, one for the left side of the body and one for the right, from three options: the test cream, a positive control or no treatment (use of standard cleanser only). Treatments were applied twice daily for 4 weeks to the face and forearms (Study 1) or the face only (Study 2). Instrumental and clinical skin assessments were performed by trained technicians. Study 1 involved tape stripping and a 5‐day no‐treatment (‘regression’) period at the end of the 4 weeks. Independent lay graders were asked to grade the skin texture of subjects in Study 2 from high‐resolution photographs.

Results

In Study 1 (n = 66), the test cream significantly decreased the transepidermal water loss (TEWL) values on the forearm, and in the cheek area of the face, relative to baseline and compared to no treatment, and increased skin Corneometer values. The improvements were partially retained during a subsequent 5‐day period of no treatment. Increases in TEWL values on skin subjected to tape stripping were significantly lower after 4 weeks of using the test cream compared to no treatment. In Study 2 (n = 72 subjects with visible signs of ageing), there was a favourable trend in the change from baseline of a skin roughness parameter, R_a, for the test cream compared to no treatment. There were statistically significant improvements in the Fitzpatrick wrinkle score compared to no treatment, decreases in TEWL and increased Corneometer values and Cutometer values (R5 elasticity parameter). Grading of high‐resolution images failed to detect the improvements in skin texture (defined as pores, smoothness and unevenness) for the test cream vs. no treatment. No treatment‐related serious or severe adverse events were reported.

Conclusion

Twice daily application of the test cream over 4 weeks had beneficial effects on skin barrier function, moisturization, wrinkle dimensions and elasticity compared to no treatment. These studies provide proof‐of‐concept evidence and highlight the cosmetic benefit of the biomimetic lamellar cream formulation. Study registration: NCT03216265, NCT03180645.

Variation in melanin content and composition in type V and VI photoexposed and photoprotected human skin: the dominant role of DHI

A combination of techniques, including high-performance liquid chromatography (HPLC), spectrophotometric measurements, and a novel method for quantifying melanosome morphology, were applied to the analysis of melanin content and composition in highly pigmented (Fitzpatrick type V and VI) human skin. We found that total epidermal melanin content is significantly elevated in photoexposed type V and VI skin (approximately 1.6 x), while analysis of individual melanin components suggests that pheomelanin content increases only slightly, whereas 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-eumelanin and to a greater extent 5,6-dihydroxyindole (DHI)-eumelanin content are both markedly elevated. Analysis of the relative composition of epidermal melanin in these subjects revealed that DHI-eumelanin is the largest single component (approximately 60-70%), followed by DHICA-eumelanin (25-35%), with pheomelanin being a relatively minor component (2-8%). Moreover, there was a comparative enrichment of DHI-eumelanin at photoexposed sites, with a corresponding decline in the relative contributions from DHICA-eumelanin and pheomelanin. There was also a good correlation and close agreement between the concentration of spheroidal melanosomes determined by morphological image analysis and the concentration of pheomelanin determined by a combination of HPLC and spectrophotometric analysis (r = 0.89, P < 0.02). This study demonstrates the usefulness of melanosome morphology analysis as a sensitive new method for the quantification of melanin composition in human skin. The data also suggest that DHI-eumelanin formation is the dominant pathway for melanin synthesis in heavily pigmented (Fitzpatrick V and VI) skin types in vivo, and is the favoured pathway when melanin production is increased in chronically photoexposed skin.

Characterization of density-dependent regulation of the tyrosinase gene promoter: role of protein kinase C

The rate-limiting step in melanogenesis is catalyzed by tyrosinase, a multifunctional enzyme encoded by the albino locus. We have previously reported that depletion of protein kinase C by long-term treatment of B16 mouse melanoma cells with phorbol dibutyrate (PDBu) prevented cell density-dependent melanogenesis. This was accompanied by a lack of induction of tyrosinase protein and mRNA. We report here the effect of PDBu on the functional activity of the mouse tyrosinase promoter by reporter gene assay and its effect on the binding of nuclear proteins from B16 cells to the "M-box" region of the mouse tyrosinase promoter. Short-term PDBu treatment of B16 cells transfected with a mouse tyrosinase promoter-luciferase construct resulted in increased reporter gene activity, while long-term PDBu treatment inhibited reporter gene activity. Using an oligonucleotide containing the M-box and its flanking residues in electrophoretic mobility shift assays, we found a density-dependent change in the pattern of DNA-protein complexes. One complex was found to be negatively regulated by long-term PDBu treatment. Competition experiments with various mutated oligonucleotides demonstrated that both the M-box and flanking residues are important for nuclear protein binding. The complex whose formation was inhibited by long-term PDBu treatment was shown to contain the basic helix-loop-helix leucine zipper protein microphthalmia-associated transcription factor (MITF). These results suggest that chronic PDBu treatment might inhibit tyrosinase expression (and subsequent melanogenesis) by affecting the amount or function of MITF.

Regulation of melanogenesis in B16 mouse melanoma cells by protein kinase C

Melanogenesis is regulated by a variety of environmental and hormonal factors. In this study, we showed that protein kinase C (PKC) plays a major role in regulating melanogenesis in B16 mouse melanoma cells. Chronic treatment of B16 cells with phorbol dibutyrate resulted in a concentration-dependent loss of density-dependent induction of tyrosinase activity, which correlated positively with a concentration-dependent loss of PKC enzyme activity. In contrast, B16 clones overexpressing PKC alpha had increased tyrosinase activity. Different phorbol derivatives inhibited tyrosinase activity and depleted cellular PKC alpha in a manner that reflected their reported tumor-promoting activity. Western blotting analysis showed that phorbol dibutyrate decreased the amount of the brown locus gene product (TRP-1) by 50% and lowered the amount of the albino locus gene product (tyrosinase) to undetectable levels. None of the phorbol derivatives affected the level of the slaty locus protein (TRP-2). The decrease in tyrosinase and TRP-1 protein levels was found to be due to a decrease in the mRNA encoded by these genes. In addition to inhibiting the density-dependent increase in tyrosinase activity, phorbol dibutyrate inhibited some, but not all, of the 8-bromocyclic AMP-induced increase in tyrosinase activity. This was accompanied by a decrease in the amount of tyrosinase protein induced by 8-bromocyclic AMP. Although 8-bromocyclic AMP did not change the level of TRP-1, it did reverse the decrease in the amount of this protein induced by phorbol dibutyrate. The amount of TRP-2 was not altered by any of these agents. These data suggest that PKC regulates melanogenesis primarily by controlling the constitutive expression of tyrosinase and, to a lesser extent, TRP-1.

Transcriptional activation of the melanocyte-specific genes by the human homolog of the mouse Microphthalmia protein

Mi protein encoded at the mouse microphthalmia (mi) locus is a transcription factor with a basic helix-loop-helix/leucine zipper structure. To assess the function of the human homolog of Mi protein, termed microphthalmia-associated transcription factor (MITF), we analyzed the effects of MITF on the promoter function of the mouse tyrosinase and tyrosinase-related protein 1 (TRP-1) genes. These two gene promoters are able to direct transcription preferentially in melanin-producing cells, and an enhancer element M box of 11 bp, containing a CATGTG motif, is conserved in both promoters. By transient expression assays, we have localized the cis-acting element of the tyrosinase gene responsible for pigment cell-specific expression to the proximal 82-bp region, which contains a CATGTG motif (positions -12 to -7) but lacks the M box (positions -107 to -97). We also provide evidence that the 82-bp region and the M box are involved in the transactivation of the tyrosinase promoter by MITF and that the M box is bound by MITF in vitro. Furthermore, MITF activated the TRP-1 gene promoter possibly through the M box (positions -44 to -34). These results suggest that MITF is a common factor regulating transcription of the pigment cell-specific genes.