Site-specific drug delivery in the skin for the localized treatment of skin diseases

ABSTRACT

Introduction: Due to the well-organized structure and barrier function of the skin, it is generally difficult for drugs applied directly on the surface of skin to reach their expected site of action. Accordingly, site-specific drug delivery in the skin has been increasingly explored to facilitate the treatment of skin diseases and reduce the systemic toxicity.

Area covered: An overview of the generally used sites for drug delivery in the skin is herein presented. Different strategies including particle-based carriers, physical technologies, and chemical approaches are discussed with regards to their potential application in site-specific drug delivery in the skin.

Expert opinion: Particle-based carriers are of particular significance for the enhancement of drug delivery in the skin. Although no recommendation can be made regarding which type of carriers can provide better skin penetration, the lipid-based colloidal systems appear to be favored due to their compatibility. In addition, the physical technologies provide unique advantages in delivering hydrophilic macromolecules for the skin immunization. As a new class of permeation enhancers, skin penetrating peptides are gaining more attention in drug delivery to skin cells. For the design of robust site-specific drug delivery systems, the impacts of diseased state and drug properties should not be disregarded.     

Production of dissolvable microneedles using an atomised spray process: Effect of microneedle composition on skin penetration

Dissolvable microneedles offer an attractive delivery system for transdermal drug and vaccine delivery. They are most commonly formed by filling a microneedle mold with liquid formulation using vacuum or centrifugation to overcome the constraints of surface tension and solution viscosity. Here, we demonstrate a novel microneedle fabrication method employing an atomised spray technique that minimises the effects of the liquid surface tension and viscosity when filling molds. This spray method was successfully used to fabricate dissolvable microneedles (DMN) from a wide range of sugars (trehalose, fructose and raffinose) and polymeric materials (polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, hydroxypropylmethylcellulose and sodium alginate). Fabrication by spraying produced microneedles with amorphous content using single sugar compositions. These microneedles displayed sharp tips and had complete fidelity to the master silicon template. Using a method to quantify the consistency of DMN penetration into different skin layers, we demonstrate that the material of construction significantly influenced the extent of skin penetration. We demonstrate that this spraying method can be adapted to produce novel laminate-layered as well as horizontally-layered DMN arrays. To our knowledge, this is the first report documenting the use of an atomising spray, at ambient, mild processing conditions, to create dissolvable microneedle arrays that can possess novel, laminate layering.     

微针在美容整形外科应用中的进展

微针技术近几年发展迅速,在美容整形外科应用广泛且相关种类繁多.基于这种情况,通过检索近几年国内外微针在美容整形外科应用的文献,分析了微针在皮瓣及皮片存活、瘢痕、面部年轻化、局部麻醉、脱发、皮肤松弛、痤疮、色素沉着等方面的应用现状,归纳出微针在该领域的应用的机制主要基于:微针能刺激表皮细胞和胶原的增生及微针能进行物质导入两方面.总结了微针使用过程中优点突出而不良反应较少的特点,展望了微针在美容整形外科中应用的美好前景.     

Green synthesis of highly stable zero-valent iron nanoparticles for organic dye treatment using Cleistocalyx operculatus leaf extract

Zero-valent iron nanoparticles are considered promising nanomaterials for wastewater treatment. However, the use of highly toxic and expensive chemicals such as sodium borohydride during synthesis has significantly limited the broad application of zero-valent iron. In this study, zero-valent iron nanoparticles (nZVI) were facilely and friendly synthesized using Cleistocalyx operculatus leaf extract as a reducing agent. The morphology and structure of the as-prepared nanomaterials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis. The obtained product was spherical with an average diameter of approximately 100 nm. The prepared nZVI exhibited remarkably stable stability, which remained in the nZVI form for more than one month in open air. The removal efficiency of rhodamine B (RhB) by nZVI reached over 95% in 30 min, proving that the nZVI nanomaterials exhibited a high and quick degradation performance toward RhB. The RhB removal efficiency of nZVI, which was proportional to the amount of nZVI and influenced by pH conditions, was determined using the visible ultraviolet absorption spectroscopy.     

Localized delivery of a lipophilic proteasome inhibitor into human skin for treatment of psoriasis

Purpose: Pentaerythritol tetrakis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) (PTTC) is a cinnamate tetraester with proteasome inhibitor activity, which may be used as a topical treatment in psoriasis, but has a computed log?P of 23. The objective of this in vitro study was to determine the intradermal delivery, skin irritation and potential efficacy of PTTC in treating psoriasis.

Methods: Solubility studies were performed to find a suitable vehicle for PTTC. Permeation studies were performed with microneedle-treated skin. A cell culture irritation test was dosed with a positive control, negative control and PTTC. An MTT assay was performed to evaluate cell viability and irritancy. Psoriatic cell culture was also dosed with PTTC and IL-6 levels were determined by ELISA.

Results: Solubility was greatest in dimethyl sulfoxide and ethyl pyruvate, with dimethyl sulfoxide delivering a greater amount (2343.41?±?384.26?µg) into stratum corneum. PTTC alone as well as topical PTTC emulsion formulation were found to be non-irritant with cell viability of 69.0?±?5.64% and 74.6?±?5.03%, respectively. Treatment with neat PTTC slightly reduced IL-6 levels and PTTC emulsion significantly reduced IL-6 levels to 92.53?±?12.74?pg/ml compared to basal levels (141.69?±?8.41?pg/ml).

Conclusion: PTTC can be delivered intradermally to potentially treat psoriasis.     

微针治疗皮肤感染的研究进展

由真菌和细菌引起的皮肤感染很难通过传统外用的治疗药物达到完全消除,受皮肤角质层的存在或是感染生物膜的形成,药物在渗透到真皮组织时受到了极大的限制。微针因可无痛直接穿透表皮至真皮组织,提高药物的透皮率和治疗率,所以在治疗皮肤局部感染时更受关注,故本文总结了近年来微针在治疗真菌和细菌感染方面的研究,以期对皮肤局部抗菌治疗提供参考。     

Effect of permeation enhancers and organic acids on the skin permeation of indapamide

The aim of present study was to investigate the transdermal properties of indapamide and to explore the efficacy of various permeation enhancers and organic acids with regard to the percutaneous absorption of indapamide. Permeation experiments were performed in vitro, using rat abdominal skin as a barrier. In the permeation studies, 2-chamber diffusion cells were used. The results obtained indicate that N-dodecylazepan-2-one, N-methyl-2-pyrrolidone, menthol and oleic acid had a strong enhancing effect on the permeation of indapamide and N-dodecylazepan-2-one exhibited the most potent enhancing effect. All eight of the organic acids chosen had a potent enhancing effect on the permeation of indapamide across rat abdominal skin. Among the organic acids examined, lactic acid had the greatest enhancing effect. The formation of an ion-pair between indapamide and organic acids may be responsible for the enhanced skin permeation of indapamide. Although the exact reason remains unknown, it is worth carrying out further investigations.     

非洛地平-硬脂酸固体脂质纳米粒的制备及其体外透皮吸收研究

目的:以固体脂质纳米粒为栽体,通过透皮给药达到提高非洛地平透皮吸收及缓释长效的目的.方法:采用溶剂挥发-超声法制备非洛地平固体脂质纳米粒水分散体,以大鼠皮肤为渗透屏障对非洛地平固体脂质纳米粒的经皮渗透进行研究.结果:非洛地平-硬脂酸固体脂质纳米粒为类球形实体粒子,平均粒径范围在50～150 nm,包封率大于85%,栽药量大于7%,药物体外释放符合一级动力学过程.体外经皮渗透速率显著高于空白对照组.结论:非洛地平固体脂质纳米粒处方设计合理,制备工艺可靠,以纳米粒作为透皮给药载体具有广阔的发展前景.     

离子导入对降纤酶经皮渗透的影响

目的研究离子导入对降纤酶经皮渗透的影响。方法利用水平式扩散池，对降纤酶进行离子导入透过大鼠皮肤和人尸表皮的渗透性试验，对电极极性、渗透介质的pH以及离子强度等影响进行考察。结果离子导入阳极转运时，在pH 6.4的磷酸盐缓冲介质中，降纤酶的表观经皮渗透系数为（1.2±0.4）×10^-4 cm·h^-1，明显高于阴极转运［（4.3±1.4）×10^-5 cm·h^-1］；在pH 7.4磷酸盐缓冲介质中，降纤酶阳极离子导入经皮渗透量为（25±5）×10^-14 mol·cm^-2高于pH 6.4介质经皮渗透量［(15±4)×10^-14 mol·cm^-2］。结论离子导入阳极转运能够促进降纤酶的经皮渗透，电渗作用有重要影响。     

Fabrication and characterisation of self-applicating heparin sodium microneedle patches

Abstract

The aim of this study was to develop heparin sodium loaded microneedle patches using different compositions of polyvinyl alcohol polymer and sorbitol. A vacuum micromolding technique was used to fabricate microneedle patches while heparin sodium was loaded into needle tips. Physical features of patches were evaluated by measuring thickness, width, folding endurance and swelling percentage. Patches were also characterised by optical microscopy and scanning electron microscopy to determine the microneedle length and surface morphologies. A preliminary assessment of the microneedle performance was studied by examining the in-vitro insertion to the parafilm and recording the in-vitro drug release profile. In-vivo activity of patches was confirmed by measuring activated partial thromboplastin time and histological examination of the micropierced skin tissues. Prepared patches were clear, smooth; uniform in appearance; with sharp pointed microprojections and remained intact after 1000 folding. The microneedles were stiffer in nature, as they reproduce microcavities in the parafilm membrane following hand pushing without any structural loss. Insertion study results showed successful insertion of microneedles into the parafilm. Disrupted stratum corneum evident from histological examination confirmed successful insertion of the microneedle without affecting the vasculature. In-vitro release study confirmed ～92% release of the loaded drug within 120?min. A significant prolongation of activated partial thromboplastin time (4 folds as compared to negative control) was recorded following the application of heparin sodium loaded microneedle patch onto rabbit skin. In conclusion microneedles are a valuable drug delivery system, benefiting the patients with minimal skin invasion and also allowing self-administration of heparin sodium in a sustained release manner for the management of chronic ailments.     

Effect of ethanol pretreatment on skin permeation of drugs

It has been demonstrated that ethanol (EtOH) can enhance skin permeation of drugs when simultaneously applied with drugs. However, only a few studies have reported on the pretreatment effect of EtOH on skin permeations. In this study, the pretreatment effects of EtOH on skin permeation of drugs were investigated by measuring changes in skin permeation and electrical skin resistance. Permeabilities of deuterium oxide (D2O), isosorbide mononitrate (ISMN), isosorbide dinitrate (ISDN), calcein sodium (CA-Na), and fluorescein isothiocyanate-dextran 4?kDa (FD-4, 3.3-4.4?kDa) were evaluated through Yucatan micropig skin pretreated with different concentrations of EtOH solution. From the results, almost constant skin permeabilities of D2O and ISDN were observed independent of EtOH concentration. Skin permeabilities of ISMN, CA, and FD-4 increased with low concentrations of EtOH, but decreased with high concentrations of EtOH. At 99.5% EtOH pretreatment, skin permeabilities of hydrophilic compounds (ISMN, CA, and FD-4) decreased to non-detectable levels. In addition, low molecular ion transports were almost constant at any EtOH concentration. Since molecular (ion) sizes of ISMN, CA, and FD-4 are larger than Na⁺, Cl^－, and D2O, permeation pathway sizes for hydrophilic compounds in the skin barrier may be remarkably decreased by pretreatment with high concentrations of EtOH. However, the permeability coefficient of ISDN was not influenced by any EtOH concentration, since ISDN is a lipophilic, low-molecular compound that permeated through the lipophilic stratum corneum pathway. The present results show useful information for repeatedly and topically applied formulations containing EtOH, and also contribute to the effective use of alcohol formulations.     

Influence of the delivery systems using a microneedle array on the permeation of a hydrophilic molecule, calcein.

Despite the advantages of drug delivery through the skin, such as easy accessibility, convenience, prolonged therapy, avoidance of the liver first-pass metabolism and a large surface area, transdermal drug delivery is only used with a small subset of drugs because most compounds cannot cross the skin at therapeutically useful rates. Recently, a new concept was introduced known as microneedles and these could be pierced to effectively deliver drugs using micron-sized needles in a minimally invasive and painless manner. In this study, biocompatible polycarbonate (PC) microneedle arrays with various depths (200 and 500mum) and densities (45, 99 and 154ea/cm(2)) were fabricated using a micro-mechanical process. The skin permeability of a hydrophilic molecule, calcein (622.5D), was examined according to the delivery systems of microneedle, drug loading, depth of the PC microneedle, and density of the PC microneedle. The skin permeability of calcein was the highest when the calcein gel was applied to the skin with the 500mum-depth PC microneedle, simultaneously. In addition, the skin permeability of calcein was the highest when 0.1g of calcein gel was coupled to the 500mum-depth PC microneedle (154ea/cm(2)) as well as longer microneedles and larger density of microneedles. Taken together, this study suggests that a biocompatible PC microneedle might be a suitable tool for transdermal drug delivery system of hydrophilic molecules with the possible applications to macromolecules such as proteins and peptides.     

Effect of liposomes and niosomes on skin permeation of enoxacin

The skin permeation and partitioning of a fluorinated quinolone antibacterial agent, enoxacin, in liposomes and niosomes, after topical application, were elucidated in the present study. In vitro percutaneous absorption experiments were performed on nude mouse skin with Franz diffusion cells. The influence of vesicles on the physicochemical property and stability of the formulations were measured. The enhanced delivery across the skin of liposome and niosome encapsulated enoxacin had been observed after selecting the appropriate formulations. The optimized formulations could also reserve a large amount of enoxacin in the skin. A significant relationship between skin permeation and the cumulative amount of enoxacin in the skin was observed. Both permeation enhancer effect and direct vesicle fusion with stratum corneum may contribute to the permeation of enoxacin across skin. Formulation with niosomes demonstrated a higher stability after 48 h incubation compared to liposomes. The inclusion of cholesterol improved the stability of enoxacin liposomes according to the results from encapsulation and turbidity. However, adding negative charges reduced the stability of niosomes. The ability of liposomes and niosomes to modulate drug delivery without significant toxicity makes the two vesicles useful to formulate topical enoxacin.     

Effect of emulsification on the skin permeation and UV protection of catechin

Abstract

An anti-aging effect may be obtained by skin application of tea catechins (Camellia sinensis) since they have high ultraviolet (UV)-protection activity. In this study, the skin permeation of catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg) and epigallocatechin gallate (EGCg) was determined and compared, and the effect of emulsification on the skin permeation of C was measured. The UV-protective effect of C was also determined. The in vitro skin permeability of each catechin derivative was determined using side-by-side diffusion of cells. The UV-protective effect of C was determined by applying different concentrations of C to the solution or emulsion on a three-dimensional cultured human skin model or normal human epidermal keratinocytes with UV-irradiation. ECg and EGCg with gallate groups showed lower skin permeability than C, EC and EGC without gallate groups, suggesting that the skin permeability of catechin derivatives may be dependent on the existence of a gallate group. Interestingly, the skin permeation of C was increased by an o/w emulsification. In addition, the C emulsion showed a significantly higher UV-protective effect by C than that with its aqueous solution. These results suggest that the o/w emulsion of catechin derivatives is probably useful as a cosmetic formulation with anti-aging efficacy.     

Effect of counter-ions and penetration enhancers on the skin permeation of flurbiprofen

The aim of this work was to investigate the percutaneous absorption of flurbiprofen (FP) using counter-ions as enhancers as well as to compare their enhancing activity with penetration enhancers in vitro. The in vitro permeation studies of FP were performed in isopropyl myristate (IPM) solution by two-chamber diffusion cells, using rat abdominal skin as a model. Among the penetration enhancers examined, including the cosolvents of propylene glycol and ethanol (EtOH), oleic acid, menthol, laurocapram, sorbitan monooleate, and N-methyl-2-pyrrolidone (NMP), 10% (w/w) EtOH and NMP exhibited the most potent solubilization and enhancing effects of FP from IPM, with a flux of (372.60 ± 45.12) µg/cm²/h and (474.21 ± 46.64) µg/cm²/h, respectively. Ten percent (w/w) EtOH/IPM binary system was used to investigate the effect of the counter-ions, namely diethylamine (DEA), triethylamine (TEA), ethanolamine (EtA), diethanolamine (DEtA), triethanolamine (TEtA), and N-(2′-hydroxyethanol)-piperdine (HEPP). The cumulative amounts were markedly increased in the presence of the counter-ions, and the highest flux of (1297.53 ± 121.81) µg/cm²/h was obtained by DEA. This was related to the decreased lipophilicity and different physicochemical properties of the ion-pairs. In particular, we proved the formation of an FP/amine ion-pair in solution by ¹H-NMR. The results suggest that the counter-ions are more efficient than penetration enhancers. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1826–1837, 2010     

Microarrays and microneedle arrays for delivery of peptides,proteins, vaccines and other applications

Introduction: Peptide and protein microarray and microneedle array technology provides direct information on protein function and potential drug targets in drug discovery and delivery. Because of this unique ability, these arrays are well suited for protein profiling, drug target identification/validation and studies of protein interaction, biochemical activity, immune responses, clinical prognosis and diagnosis and for gene, protein and drug delivery.

Areas covered: The aim of this review is to describe and summarize past and recent developments of microarrays in their construction, characterization and production and applications of microneedles in drug delivery. The scope and limitations of various technologies in this respect are discussed.

Expert opinion: This article offers a review of microarray/microneedle technologies and possible future directions in targeting and in the delivery of pharmacologically active compounds for unmet needs in biopharmaceutical research. A better understanding of the production and use of microarrays and microneedles for delivery of peptides, proteins and vaccines is needed.