Advances in Skin-on-a-Chip Technologies for Dermatological Disease Modeling.

Skin-on-a-chip (SoC) technologies are emerging as a paradigm shift in dermatology research by replicating human physiology in a dynamic manner not achievable by current animal models. Although animal models have contributed to successful clinical trials, their ability to predict human outcomes remains questionable, owing to inherent differences in skin anatomy and immune response. Covering areas including infectious diseases, autoimmune skin conditions, wound healing, drug toxicity, aging, and antiaging, SoC aims to circumvent the inherent disparities created by traditional models. In this paper, we review current SoC technologies, highlighting their potential as an alternative to animal models for a deeper understanding of complex skin conditions.

Single-stranded DNA probe paired aptasensor with extra dye binding sites to enhance its fluorescence response in the presence of a target compound.

The purpose of this study is to investigate the possibility of improving the performance of a DNA binding dye water quenching based aptasensor without changing or truncating the aptamer. To demonstrate the possibility of increasing the change in fluorescence of the aptasensor by pairing it with a suitable ssDNA probe, three ssDNA probes (probe 1, 2, and 3) were employed and the fluorescence from the bound dyes was measured. This showed that ssDNA probe 2 created the most additional binding sites. By varying the target compound concentration (0, 0.05, 0.5, 5, 50, and 500 mg L-1 4-n-nonylphenol), the corresponding change in the fluorescence signal of the unpaired and ssDNA probe paired aptasensors were measured and compared over a range of emission wavelengths. The response of all three ssDNA probe paired aptasensors showed good fit (R 2 = 0.88-0.92) to a logarithmic response. The sensitivity of the aptasensor paired with ssDNA probe 2 was improved by ∼60%, whereas that of the aptasensor paired with ssDNA probe 3 was only improved by a marginal ∼3%. This study is a demonstration of using an appropriate ssDNA probe to increase the number of binding sites and hence the performance of a DNA binding dye and water quenched aptasensor. It is a possibility that can be extended to similar aptasensors without having to change or truncate the aptamer.

A systematic study on the discrepancy of fluorescence properties between in solutions and in cells: super-bright, environment-insensitive benzocoumarin dyes.

The benzocoumarin dyes fluoresce negligibly in aqueous media but very strongly in cells, whereas representative conventional dyes display contrasting behaviour; the distinct emission behaviour of the fluorophores in organic solutions, in aqueous media, and in cell convinces the uniqueness of the cellular environment. The in cellulo superbright benzocoumarins also reveal an environment-insensitive emission behaviour, which is required for the reliable analysis via ratiometric imaging.

Frontiers in Probing Alzheimer's Disease Biomarkers with Fluorescent Small Molecules.

Alzheimer's disease (AD) is the most common form of dementia. The pathogenesis of the disease is associated with aggregated amyloid-ß, hyperphosphorylated tau, a high level of metal ions, abnormal enzyme activities, and reactive astrocytes. This outlook gives an overview of fluorescent small molecules targeting AD biomarkers for ex vivo and in vivo imaging. These chemical imaging probes are categorized based on the potential biomarkers, and their pros and cons are discussed. Guidelines for designing new sensing strategies as well as the desirable properties to be pursued for AD fluorescence imaging are also provided.

Detection of Nonylphenol with a Gold-Nanoparticle-Based Small-Molecule Sensing System Using an ssDNA Aptamer.

Endocrine-disrupting chemicals (EDCs) threaten many kinds of life throughout the world. These compounds function the same as sexual hormones, inducing precocious puberty, gynecomastia, etc., in the human body. To prevent excess exposure to nonylphenol (NP), a simple and rapid detection system is needed. In this study, we develop a nonylphenol-specific aptamer from a random single-stranded DNA library and test a rapid sensor system based on the aptamer and gold nanoparticles (AuNPs). The aptamer was screened by a methodology involving reduced graphene oxide (rGO). As a result of screening and sequencing, a DNA aptamer was developed that recognizes the target with high binding affinity (Kd = 194.2 ± 65.9 nM) and specificity. The sensor system developed using the aptamer and gold nanoparticles is sensitive (LOD = 2.239 nM). Circular dichroism (CD) spectrometry results show that the free aptamer binds to the target molecule. The aptamer was characterized using gold nanoparticles to measure UV absorbance. Our results suggest that the sensor system developed using this aptamer is useful for field diagnosis of small molecules.

Fluorescent Labeling of Protein Using Blue-Emitting 8-Amino-BODIPY Derivatives.

8-Amino-BODIPY (boron-dipyrromethane) dyes show bright blue fluorescence. Disclosed here are synthesis and characterization of the photophysical properties of a series of functionalized 8-Amino-BODIPY (BP1-4) for protein labeling. The compact structure and solvent-insensitive absorption property of the dye are desirable features for protein labeling. For the model protein, bovine serum albumin (BSA), the labeling proceeds under mild condition via amide bond formation or thiol-ene conjugation with maintaining the bright blue fluorescence. The chromatography and mass spectroscopy analysis clearly support the labeling of the BODIPY dye on the BSA. The protein labeling with blue-emitting BODIPY would be applicable for studying protein dynamics and fluorescence resonance energy transfer (FRET) with intrinsic biomolecules.

Close Correlation of Monoamine Oxidase Activity with Progress of Alzheimer's Disease in Mice, Observed by in Vivo Two-Photon Imaging.

Monoamine oxidases (MAOs) play an important role in Alzheimer's disease (AD) pathology. We report in vivo comonitoring of MAO activity and amyloid-ß (Aß) plaques dependent on the aging of live mice with AD, using a two-photon fluorescence probe. The probe under the catalytic action of MAO produces a dipolar fluorophore that senses Aß plaques, a general AD biomarker, enabling us to comonitor the enzyme activity and the progress of AD indicated by Aß plaques. The results show that the progress of AD has a close correlation with MAO activity, which can be categorized into three stages: slow initiation stage up to three months, an aggressive stage, and a saturation stage from nine months. Histological analysis also reveals elevation of MAO activity around Aß plaques in aged mice. The close correlation between the MAO activity and AD progress observed by in vivo monitoring for the first time prompts us to investigate the enzyme as a potential biomarker of AD.

Fluorescence sensing systems for gold and silver species.

Besides the noble physical appearance of gold and silver, their novel chemical properties attracted the modern technology for various industrial, chemical and biological uses including medical applications. The widespread use of gold and silver, however, can cause potential hazards to our environment. Therefore, suitable detection methods are a prerequisite for the evaluation of their harmful effects as well as for studying their beneficial biological properties. Due to the several advantages over the conventional analytical methods, the fluorescence detection of gold and silver has become an active research area in recent years. In this review, we provide an overview of the reported fluorescent detection systems for gold and silver species, and discuss their sensing properties with promising features. The future scope of developments in this field of research is also mentioned.