Microneedles for transdermal drug delivery

The success of transdermal drug delivery has been severely limited by the inability of most drugs to enter the skin at therapeutically useful rates. Recently, the use of micron-scale needles in increasing skin permeability has been proposed and shown to dramatically increase transdermal delivery, especially for macromolecules. Using the tools of the microelectronics industry, microneedles have been fabricated with a range of sizes, shapes and materials. Most drug delivery studies have emphasized solid microneedles, which have been shown to increase skin permeability to a broad range of molecules and nanoparticles in vitro. In vivo studies have demonstrated delivery of oligonucleotides, reduction of blood glucose level by insulin, and induction of immune responses from protein and DNA vaccines. For these studies, needle arrays have been used to pierce holes into skin to increase transport by diffusion or iontophoresis or as drug carriers that release drug into the skin from a microneedle surface coating. Hollow microneedles have also been developed and shown to microinject insulin to diabetic rats. To address practical applications of microneedles, the ratio of microneedle fracture force to skin insertion force (i.e. margin of safety) was found to be optimal for needles with small tip radius and large wall thickness. Microneedles inserted into the skin of human subjects were reported as painless. Together, these results suggest that microneedles represent a promising technology to deliver therapeutic compounds into the skin for a range of possible applications.     

空心微针透皮给药技术的研究进展

空心微针类似于微米级的注射针,具有注射给药和透皮给药的双重特点.作为一种新型的透皮给药技术,空心微针近年来在疫苗和胰岛素等生物大分子药物的递送方面显示出极大的潜力.笔者根据近年来国内外相关的研究报道,对空心微针的促透机制、常用制备材料及工艺和在透皮给药中的应用等进行归纳总结,以期为空心微针技术的研究和发展提供参考借鉴.     

微针技术在经皮给药中的应用

微针是经皮给药的物理促渗方法之一,有着很好的市场前景。本文介绍微针的透皮促渗机制、促进药物经皮渗透的因素、复合技术以及微针在大分子经皮促渗中的应用。     

Biomedical applications of microneedles in therapeutics: recent advancements and implications in drug delivery

Introduction: The skin, as the largest organ, is a better option for drug delivery in many diseases. However, most transdermal delivery is difficult due to the low permeability of therapeutics across the various skin layers. There have been many innovations in transdermal drug delivery to enhance the therapeutic efficacy of the drugs administered. Microneedles (MN), micron sized needles, are of great interest to scientists as a new therapeutic vehicle through transdermal routes, especially for vaccines, drugs, small molecules, etc.

Areas covered: This review covers new insights into different types of MNs such as solid, hollow, coated and dissolving MNs (SMNs, HMNs, CMNs, and DMNs) for selected biomedical applications in detail. Specific focus has been given to CMNs and DMNs for vaccine and drug delivery applications with recent developments in new MNs covered.

Expert opinion: This review explores the feasibility of innovative MNs used as a drug delivery carrier. Because most of the SMNs and HMNs have many limitations, it is difficult to achieve therapeutic efficacy. Therefore, many scientists are investigating functional modifications of MNs through covalent and non-covalent methods, especially for CMNs and DMNs. The biomedical applications of MNs are growing and new exciting improvements could be achieved, thus resulting in better micro/nano technologies in the near future.     

Microneedles: a valuable physical enhancer to increase transdermal drug delivery

Transdermal drug delivery offers an attractive alternative to the conventional drug delivery methods of oral administration and injection. However, the stratum corneum acts as a barrier that limits the penetration of substances through the skin. Recently, the use of micron-scale needles in increasing skin permeability has been proposed and shown to dramatically increase transdermal delivery. Microneedles have been fabricated with a range of sizes, shapes, and materials. Most in vitro drug delivery studies have shown these needles to increase skin permeability to a broad range of drugs that differ in molecular size and weight. In vivo studies have demonstrated satisfactory release of oligonucleotides and insulin and the induction of immune responses from protein and DNA vaccines. Microneedles inserted into the skin of human subjects were reported to be painless. For all these reasons, microneedles are a promising technology to deliver drugs into the skin. This review presents the main findings concerning the use of microneedles in transdermal drug delivery. It also covers types of microneedles, their advantages and disadvantages, enhancement mechanisms, and trends in transdermal drug delivery.     

微针经皮给药应用的新进展

微针有助于改善患者的用药依从性,提高药物的生物利用度.近年来,微针在疫苗接种、蛋白质和多肽给药、DNA给药、皮肤美容、眼科用药、局部麻醉、微量取样等领域均有应用.微针在胰岛素给药和局部麻醉中的研究已进入临床试验阶段,在皮肤美容、疫苗接种和蛋白质给药方面已有上市产品.     

Colloidosomes: an emerging vesicular system in drug delivery

The application of colloidal and nanoparticulate carrier systems in the biomedical field has changed the definitions of diagnosis, treatment, and disease management. Carrier systems such as liposomes, polymeric particles, and micro-emulsion droplets are used for the sustained release of drugs, pesticides, fragrances, and other substances. Although such delivery systems are widely employed in specialized areas such as gene delivery, targeting to brain, tumor targeting, and oral vaccine formulations, problems associated with their stability and permeability are often encountered, thereby limiting their general application. In the series of vesicular systems, colloidosomes are emerging as a potential tool for controlled delivery of drugs as well as of cosmetics and food supplements. Colloidosomes are solid microcapsules formed by the self-assembly of colloidal particles at the interface of emulsion droplets. Colloidosomes offer precise control over their size, permeability, compatibility, and mechanical strength and can be prepared with an aqueous, aqueous gel, or oily core. This review focuses on the types, fabrication techniques, and stability of colloidosomes.     

微乳在经皮给药系统中的应用

微乳经皮给药是目前国内外药学工作者研究的重点,也是目前药物制剂研发热点之一。本文主要从微乳的组成、促渗机制、微乳在经皮给药中的应用3个方面进行了综述。微乳经皮给药具有很好的应用前景。     

经皮给药的研究进展

药物的透皮给药主要受到皮肤障碍、药物的分子量和亲水/油性等因素的影响.利用物理和化学方法,同时,辅以载体方法可有效提高药物(尤其是生物大分子药物和复方中药)经皮给药效率.随着透皮给药的不断发展改进,经皮给药系统一定会发挥更大的潜力.     

Development of mesophasic microreservoir-based transdermal drug delivery system of propranolol

The mesophasic microreservoir comprises lyotrophic liquid crystals. The liquid crystals were prepared of Brij-35, cetosteryl alcohol and propranolol and evaluated for parameters viz. anisotropy, size and size distribution and drug entrapment efficiency. Subsequent to this liquid crystals based transdermal drug delivery system (TDS) was prepared by incorporating liquid crystals in previously prepared matrix based transdermal patch and evaluated for stability studies like temperature, humidity and aging. The system was also studied for tensile strength, moisture content, water vapor transmission, drug content, anisotropy and In vitro drug release studies.     

Skin permeabilization for transdermal drug delivery: recent advances and future prospects

Introduction: Transdermal delivery has potential advantages over other routes of administration. It could reduce first-pass metabolism associated with oral delivery and is less painful than injections. However, the outermost layer of the skin, the stratum corneum (SC), limits passive diffusion to small lipophilic molecules. Therefore, methods are needed to safely permeabilize the SC so that ionic and larger molecules may be delivered transdermally.

Areas covered: This review focuses on low-frequency sonophoresis, microneedles, electroporation and iontophoresis, and combinations of these methods to permeabilize the SC. The mechanisms of enhancements and developments in the last 5 years are discussed. Potentially high-impact applications, including protein delivery, vaccination and sensing are presented. Finally, commercial interest and clinical trials are discussed.

Expert opinion: Not all permeabilization methods are appropriate for all applications. Focused studies into applications utilizing the advantages of each method are needed. The total dose and kinetics of delivery must be considered. Vaccination is one application where permeabilization methods could make an impact. Protein delivery and analyte sensing are also areas of potential impact, although the amount of material that can be delivered (or extracted) is of critical importance. Additional work on the miniaturization of these technologies will help to increase commercial interest.     

Microneedles as transdermal delivery systems: combination with other enhancing strategies

Transdermal drug delivery has exhaustively been studied over the past decades due to its multiple advantages over other administration routes; however, drugs that can be administered by this via are few owe to the stratum corneum permeability properties. Recently, several strategies to bypass the upper-layer skin barrier have been developed. One of the latest advances in this area has been the use of micro-scale needles, which painlessly pierce skin, increasing the passage of drugs with unfavourable skin permeability (i.e., low potent, hydrophilic, high molecular drugs) by several orders of magnitude, by bypassing the stratum corneum. Microneedles have shown to be safe and easy-to-use for drug administration, a nouvelle alternative to hypodermic needle injections, and an array in which drugs can be included to attain a controlled release as to achieve a higher drug delivery. Several works have demonstrated that such devices dramatically increase transdermal delivery of large molecules, thus nowadays microneedles have been regarded as a potential technology approach to be employed alone or with other enhancing methods such as electroporation and iontophoresis, as well as with different drug carriers (e.g., lipid vesicles, micro- and nanoparticles). Hence, this review is mainly focused on presenting the results obtained when combining microneedles with a variety of strategies to ease drug diffusion through skin, including physical enhancers and drug carrier systems.     

微针透皮给药系统应用研究进展

微针透皮给药系统是近年来透皮给药系统研究的热点。微针透皮给药系统具有注射给药和透皮给药的双重优势,具有快速、方便、无痛等众多优点,研究表明可以显著提高药物透皮速率和吸收量,特别是在蛋白质、多肽、DNA和RNA等大分子物质的透皮制剂研究领域表现出良好的效果和应用前景,本文对微针透皮给药系统应用研究的最新进展进行了综述。随着微针加工技术、载药技术和应用研究的不断深入,微针透皮技术在临床领域将会有更广泛的应用。     

Microneedles for drug delivery: trends and progress

In recent years, there has been a surge in the research and development of microneedles (MNs), a transdermal delivery system that combines the technology of transdermal patches and hypodermic needles. The needles are in the hundreds of micron length range and therefore allow relatively little or no pain. For example, biodegradable MNs have been researched in the literature and have several advantages compared with solid or hollow MNs, as they produce non-sharp waste and can be designed to allow rapid or slow release of drugs. However, they also pose a disadvantage as successful insertion into the stratum corneum layer of the skin relies on sufficient mechanical strength of the biodegradable material. This review looks at the various technologies developed in MN research and shows the rapidly growing numbers of research papers and patent publications since the first invention of MNs (using time series statistical analysis). This provides the research and industry communities a valuable synopsis of the trends and progress being made in this field.     

丹皮酚经皮给药系统的研究

目的 以脂溶性药物丹皮酚为模型药物,制备载药传递体,评价其质量并进行小鼠经皮渗透体外研究.方法 采用薄膜分散-超声法制备丹皮酚传递体;以改进的Franz扩散池进行体外小鼠经皮渗透实验,比较不同处方组成对丹皮酚经皮渗透的影响.结果 丹皮酚传递体为乳白色、近透明的胶体溶液.脂质传递体、普通脂质体和丹皮酚水醇混悬液8 h时的累积渗透率分别为81.22%、49.66%、42.22%.结论 丹皮酚传递体制备工艺简单可行,所制传递体的粒径较小且均匀,并可促进丹皮酚的经皮转运.     

抗抑郁药透皮给药系统研究进展

抗抑郁药的传统给药途径如口服给药往往存在生物利用度低、用药成本高、患者依从性较差等缺陷。抗抑郁药透皮给药系统（TDDS）研制可以极大提高药效,减少其不良反应,已成为国内外研究的热点。本文综述抑郁症的发病机制、抗抑郁药类型以及TDDS在抗抑郁药开发中的应用。     

上市新型经皮递药系统的研究进展

对近几年来上市的经皮制剂进行文献整理和归纳，通过查阅相关文献，对贴剂、软膏剂、凝胶剂、乳膏剂、泡沫剂、洗剂等经皮给药制剂的特点、上市时间、作用、不良反应等进行总结。经皮制剂是药物通过皮肤吸收的一类外用递药给药系统，可以局部给药也可以全身给药，具有安全性高、毒副作用小、使用方便的优点，是目前国内外研究的热点。