Highly stable and fast-dissolving ascorbic acid-loaded microneedles.

OBJECTIVES: Ascorbic acid has many benefits to the skin. Numerous attempts to promote its topical delivery show great challenges since its chemical instability and poor skin impermeability. Microneedle delivery is a simple, safe, painless and effective means to deliver therapeutic or nourishing molecules into the skin. The purpose of this study was twofold: (a) to develop a new formulation of ascorbic acid-loaded microneedles to enhance ascorbic acid stability by investigating an optimal amount of polyethyleneimine as an additive to the dextran-based microneedle formulation and (b) to assess microneedle properties in terms of dissolving rate, skin penetration ability, biocompatibility and antimicrobial activity. METHODS: The microneedles formulated with ascorbic acid and varied polyethyleneimine concentrations were fabricated and subsequently tested for ascorbic acid stability using 2,2-diphenyl-1-picrylhydrazyl assay. The dissolution rate and skin penetration depth were investigated in porcine skin and the reconstructed human full-thickness skin model respectively. The skin irritation tests were done according to the Organisation for Economic Co-operation and Development Test Guideline No. 439. An antimicrobial disc susceptibility test was performed against Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis. RESULTS: Among varied amounts of 0%, 1.5%, 3.0% and 4.5% (w/v), the 3.0% polyethyleneimine showed the most desirable characteristics, including well-preserved shape integrity after demoulding, significantly improved stability of ascorbic acid (p < 0.001) from 33% to 96% antioxidant activity after 8 weeks of storage at 40°C, increased dissolving rate (p < 0.001) by being completely dissolved within 2 min after the skin insertion, passing skin penetration and biocompatibility tests as well as having a broad spectrum of antimicrobial property. CONCLUSION: With a safety profile and enhanced properties, the new formulation of ascorbic acid-loaded microneedles shows outstanding potential as commercially available cosmetics and healthcare products.

OBJECTIFS: L'acide ascorbique présente de nombreux avantages pour la peau. De nombreuses tentatives pour promouvoir sa délivrance topique présentent de grands défis en raison de son instabilité chimique et de sa faible imperméabilité cutanée. L'administration de micro-aiguilles est un moyen simple, sûr, indolore et efficace d'administrer des molécules thérapeutiques ou nourrissantes dans la peau. Le but de cette étude était double : a) développer une nouvelle formulation de microaiguilles chargées d'acide ascorbique pour améliorer la stabilité de l'acide ascorbique en étudiant une quantité optimale de polyéthylèneimine comme additif à la formulation de microaiguilles à base de dextrane ; et b) évaluer les propriétés des micro-aiguilles en termes de vitesse de dissolution, de capacité de pénétration cutanée, de biocompatibilité et d'activité antimicrobienne. MÉTHODES: Les microaiguilles formulées avec de l'acide ascorbique et des concentrations variées de polyéthylèneimine ont été fabriquées et ensuite testées pour la stabilité de l'acide ascorbique à l'aide d'un dosage de 2,2-diphényl-1-picrylhydrazyle. Le taux de dissolution et la profondeur de pénétration de la peau ont été étudiés dans la peau de porc et le modèle de peau humaine reconstruite de pleine épaisseur, respectivement. Les tests d'irritation cutanée ont été effectués conformément à la ligne directrice n° 439 de l'Organisation de coopération et de développement économiques. Un test de sensibilité du disque antimicrobien a été réalisé contre Escherichia coli, Staphylococcus aureus et Staphylococcusepidermidis. RÉSULTATS: Parmi des quantités variées de 0, 1,5, 3,0 et 4,5 % (p/v), la polyéthylèneimine à 3,0 % a montré les caractéristiques les plus souhaitables, notamment une intégrité de forme bien préservée après démoulage, une stabilité significativement améliorée de l'acide ascorbique (p ⟨ 0,001) de 33 % à 96 % d'activité antioxydante après 8 semaines de stockage à 40 °C, augmentation du taux de dissolution (p ⟨ 0,001) en étant complètement dissous dans les2 minutes suivant l'insertion de la peau, en passant les tests de pénétration cutanée et de biocompatibilité, ainsi qu'en ayant un large spectre de propriétés antimicrobiennes. CONCLUSION: Avec un profil d'innocuité et des propriétés améliorées, la nouvelle formulation de micro-aiguilles chargées d'acide ascorbique présente un potentiel exceptionnel en tant que produits cosmétiques et de soins de santé disponibles dans le commerce.

Highly Sensitive and Exceptionally Wide Dynamic Range Detection of Ammonia Gas by Indium Hexacyanoferrate Nanoparticles Using FTIR Spectroscopy.

Ammonia gas is useful but caustic; thus, its concentration is monitored depending on applications. We prepared indium hexacyanoferrate nanoparticles (InHCF-NPs, HCF = [FeII(CN)6]4-) with average diameter around 8 nm by simple reaction at room temperature between In cations and HCF anions, and we found the unique functionality of InHCF-NPs which were capable of highly sensitive (16 ppb) and exceptionally wide range (190000, 16 ppb -0.3%) detection of ammonia gas within 6 min by IR measurements. Slope changes of the IR peak ratio of adsorbed ammonium over CN moieties in the InHCF framework indicated a good log-log linear correlation along gas concentrations, in which a wide dynamic range over 105 was realized for the first time in the field of ammonia gas detection.

Colorimetric determination of trace orthophosphate in water by using C18-functionalized silica coated magnetite.

In this study, we customized magnetic sorbents by functionalizing silica coated magnetite with octadecyl(C18)silane (Fe3O4@SiO2@C18). This sorbent was intended for the determination of trace orthophosphate (o-PO43-) in unpolluted freshwater samples. The o-PO43- was transformed to phosphomolybdenum blue (PMB), a known polyoxometalate ion. Then the PMB were coupled with cetyl trimethyl ammonium bromide (CTAB), cationic surfactant, in order to hydrophobically bound with the Fe3O4@SiO2@C18 particles through dispersive magnetic solid-phase extraction (d-MSPE) as part of sample preconcentration. The PMB-CTAB-magnetic particles are simply separated from the aqueous solution by the external magnet. The acidified ethanol 0.5 mL was used as PMB-CTAB eluent to produce an intense blue solution, which the absorbance was measured using a UV-Vis spectrophotometer at 800 nm. The proposed method (employing 2 mg of Fe3O4@SiO2@C18) yielded an enhancement factor of 32 with a linear range of 1.0-30.0 µg P L-1. Precision at 6.0 µg P L-1 and 25.0 µg P L-1 were 3.70 and 2.49% (RSD, n = 6) respectively. The lower detection limit of 0.3 µg P L-1 and quantification limit of 1.0 µg P L-1 allowed trace levels analysis of o-PO43- in samples. The reliability and accuracy of the proposed method were confirmed by using a certified reference material. Our method offers highly sensitive detection of o-PO43- with simple procedures that can be operated at room temperature and short analysis time.

Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting.

We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10(-6) W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible.