Melanoma is visible unlike other types of cancer, but it is still challenging to diagnose correctly because of the difficulty in distinguishing between benign nevus and melanoma. We conducted a robust investigation of melanoma, identifying considerable differences in local elastic properties between nevus and melanoma tissues by using atomic force microscopy (AFM) indentation of histological specimens. Specifically, the histograms of the elastic modulus of melanoma displayed multimodal Gaussian distributions, exhibiting heterogeneous mechanical properties, in contrast with the unimodal distributions of elastic modulus in the benign nevus. We identified this notable signature was consistent regardless of blotch incidence by sex, age, anatomical site (e.g., thigh, calf, arm, eyelid, and cheek), or cancer stage (I, IV, and V). In addition, we found that the non-linearity of the force-distance curves for melanoma is increased compared to benign nevus. We believe that AFM indentation of histological specimens may technically complement conventional histopathological analysis for earlier and more precise melanoma detection.

Applications of nano-sized cellulose, such as use in tissue bio-scaffolds and drug delivery, have gained much attention in medical research. However, there are only a few studies reporting the skin toxicity of nano-sized cellulose. Here, we investigated the skin toxicity of plasma-induced nanostructured cellulose (PINC) in vitro and in vivo. Morphology of the PINC as well as that of human foreskin fibroblast (Hs27) and immortalized human keratinocyte (HaCaT) cell lines cultured on PINC were analyzed by scanning electron microscopy. The in vitro cytotoxicity of the material was evaluated using Hs27 and HaCaT cell lines and a reconstructed human epidermis model. For in vivo skin toxicity testing, after attaching the PINC to the dorsal skin of Sprague–Dawley rats, skin irritation was evaluated visually and histologically. Our results showed no cytotoxicity of PINC, which did not induce apoptosis or necrosis in either type of cells tested. PINC also did not stimulate irritation on rats in vivo, and no significant inflammatory responses were observed by histological analysis. These results indicate that PINC has no significant skin toxicity in vitro or in vivo. The absence of skin toxicity in PINC suggests that it can be used for skin-related applications without any harm.

Although many methods to assess sensitization have been investigated to replace animal testing, it is still imperative to develop an in vitro method to minimize the use of animals and to classify sensitizers. Recently, an assay using the human keratinocyte cell line (HaCaT) was developed as an alternative method. Our aim was to optimize this method and validate its ability to assess sensitization. The highest dose that resulted in 75% cell viability was determined for each test substance. Then, serial dilutions of the dose were applied to measure the levels of secreted proinflammatory cytokines. To optimize the assay, statistical analyses were performed to determine whether all of the doses tested were necessary to maintain the predictive values. Exclusion of the 0.5× dose did not change the predictive values drastically. To validate the optimized method, 22 substances were evaluated without the 0.5× dose, resulting in overall predictive values of 83.3% for sensitivity, 80.0% for specificity, and 81.8% for accuracy, which are comparable to results from other validated assays. These results suggest that statistical analysis can assist in development of alternative in vitro methods and that the optimized HaCaT cell assay is reproducible.

Extremely small amounts of fatty acids detected in latent fingerprints are important for studying fingerprint visualization and age determination through changes in composition over time. However, methods for efficiently extracting or recovering fatty acids from fingerprints have not been extensively studied. If accurate and stable quantitative estimations are established, age estimates will be possible through a better understanding of the fatty acid composition. The extraction solvent and treatment method are essential factors for achieving a reliable analysis of fatty acids. There have been few previous studies that efficiently compared fatty acids. In this study, fatty acids from sebaceous fingerprint residues were quantified with various extraction solvents and treatment methods and were evaluated with gas chromatography flame ionization detection (GC-FID). All data were analyzed using a statistical method.