Effects of pretreatment of needle puncture and sandpaper abrasion on the in vitro skin permeation of fluorescein isothiocyanate (FITC)-dextran

Microneedle systems have gained attention as having many advantages over transdermal patches and hypodermic needles. The procedure provides adequate skin permeation rates without pain or severe infection. To obtain information for designing a microneedle system, macroneedles were used instead of microneedles to investigate the effects of pretreatment of needle puncture in the skin barrier stratum corneum on in vitro skin permeation of fluorescein isothiocyanate (FITC)-dextrans (4.3, 9.6 and 42.0 kDa) (FD-4, FD-10 and FD-40). The effect of sandpaper abrasion was also investigated for comparison. Both pretreatments on the skin barrier significantly increased the skin permeation of FDs. Lactate dehydrogenase (LDH) leaching was measured after pretreatment of macroneedle and sandpaper abrasion on the skin to evaluate the skin damage by these pretreatment methods. Lower leaching of LDH was observed after macroneedle puncture than after sandpaper abrasion. Next, a parallel permeation-resistance model of the skin barrier was established. Skin permeation of FD-10 was predicted by the model as a function of the number of pores in the skin barrier. Our results suggest that needle puncture may provide a safe, efficient and controllable alternative for increasing transdermal drug delivery.     

Transdermal delivery of relatively high molecular weight drugs using novel self-dissolving microneedle arrays fabricated from hyaluronic acid and their characteristics and safety after application to the skin

The purpose of this study was to develop novel dissolving microneedle arrays fabricated from hyaluronic acid (HA) as a material and to improve the transdermal permeability of relatively high molecular weight drugs. In this study, fluorescein isothiocyanate-labeled dextran with an average molecular weight of 4 kDa (FD4) was used as a model drug with a relatively high molecular weight. The microneedle arrays significantly increased transepidermal water loss (TEWL) and reduced transcutaneous electrical resistance (TER), indicating that they could puncture the skin and create drug permeation pathways successfully. Both TEWL and TER almost recovered to baseline levels in the microneedle array group, and relatively small pathways created by the microneedles rapidly recovered as compared with those created by a tape stripping treatment. These findings confirmed that the microneedle arrays were quite safe. Furthermore, we found that the transdermal permeability of FD4 using the microneedle arrays was much higher than that of the FD4 solution. Furthermore, we found that the microneedle arrays were much more effective for increasing the amount of FD4 accumulated in the skin.These findings indicated that using novel microneedle arrays fabricated from HA is a very useful and effective strategy to improve the transdermal delivery of drugs, especially relatively high molecular weight drugs without seriously damaging the skin.     

Controlled transdermal delivery of model drug compounds by MEMS microneedle array

This article reports an in vitro study of microneedle-array-enhanced transdermal transport of model drug compounds dispersed in chitosan films. Each microneedle array has 400 out-of-plane, needle-shaped microstructures fabricated using micro-electro-mechanical systems (MEMS) technology to ensure adequate mechanical strength and high precision, and consistency. A nanometer coating on the microneedles ensured the biocompatibility that is important in the application of transdermal drug delivery. Model drugs selected to investigate skin permeation in vitro were calcein, a small molecule (molecular weight, 623 d) that has little skin penetration, and bovine serum albumin (BSA) (molecular weight, 66,000 d), a hydrophilic biological macromolecule. A Franz permeation cell was used to characterize the permeation rate of calcein and BSA through the rat skin. The transdermal transport behavior of BSA was investigated from solid films coated on the surface of microneedle arrays with various chitosan concentrations, film thicknesses, and BSA contents. The BSA permeation rate decreased with the increase of the chitosan concentration; the thicker the film, the slower the permeation rate. In addition, the permeation rate increased with the increase of BSA loading dose. A linear relationship existed between the permeation rate and the square root of the BSA loading dose. Results showed that the chitosan hydrophilic polymer film acts as a matrix that can regulate the BSA release rate. The controlled delivery of BSA can be achieved using the BSA-containing chitosan matrix film incorporated with the microneedle arrays. This will provide a possible way for the transdermal delivery of macromolecular therapeutic agents such as proteins and vaccines.     

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.     

难溶性多西紫杉醇的溶解微针制备及体外评价

目的:制备一种用于透皮给药的负载多西紫杉醇(DTX)的溶解微针,并进行体外评价。方法:考察不同材料及配方制备DTX溶解微针(DTX-MN),通过外观和力学性能指标对微针进行表征,测定微针针头载药量。使用猪皮肤考察微针溶解性能。剥离小鼠腹部皮肤,进行体外透皮吸收研究,初步考察DTX-MN给药后的皮肤药代动力学。结果:成功制备了针头完整、力学性能良好的DTX-MN,最佳工艺得到的微针针头载药量为(14.81±4.20)μg (n=5),微针能完整插入皮肤穿透角质层屏障,且在10 min内完全溶解。体外透皮实验显示,DTX-MN的初始透皮速率和累积透皮通量都高于药物溶液组,相比溶液组,DTX-MN在24 h后累积渗透量提高了3.27倍,其释放机制符合Fickian扩散。结论:制备的DTX-MN有良好的穿刺皮肤的性能,能够显著促进DTX的透皮递送,该类微针有望促进DTX的浅表皮肤递送,具有潜在的临床应用价值。     

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.     

Bioceramic microneedles with flexible and self-swelling substrate

To reduce the effort required to penetrate the skin and optimize drug release profiles, bioceramic microneedle arrays with higher-aspect-ratio needles and a flexible and self-swelling substrate have been developed. Swelling of the substrate can assist in separating it from the needles and leave them in the skin as a drug depot. The preparation procedures for this bioceramic microneedle are described in the paper. Clonidine hydrochloride, the model drug, was released in a controlled manner by the microneedle device in vitro. Results showed that the microneedle array with a flexible and self-swelling substrate released the drug content faster than the array with a rigid substrate. Disintegration of the needle material and diffusion of the drug molecules are believed as the main control mechanisms of the drug release from these microneedle arrays. Ex vivo skin penetration showed that they can effectively penetrate the stratum corneum without an extra device. This work represents a progression in the improvement of bioceramic microneedles for transdermal drug delivery.     

Microneedles: an emerging transdermal drug delivery system

Objectives One of the thrust areas in drug delivery research is transdermal drug delivery systems (TDDS) due to their characteristic advantages over oral and parenteral drug delivery systems. Researchers have focused their attention on the use of microneedles to overcome the barrier of the stratum corneum. Microneedles deliver the drug into the epidermis without disruption of nerve endings. Recent advances in the development of microneedles are discussed in this review for the benefit of young scientists and to promote research in the area. Key findings Microneedles are fabricated using a microelectromechanical system employing silicon, metals, polymers or polysaccharides. Solid coated microneedles can be used to pierce the superficial skin layer followed by delivery of the drug. Advances in microneedle research led to development of dissolvable/degradable and hollow microneedles to deliver drugs at a higher dose and to engineer drug release. Iontophoresis, sonophoresis and electrophoresis can be used to modify drug delivery when used in concern with hollow microneedles. Microneedles can be used to deliver macromolecules such as insulin, growth hormones, immunobiologicals, proteins and peptides. Microneedles containing ‘cosmeceuticals’ are currently available to treat acne, pigmentation, scars and wrinkles, as well as for skin tone improvement. Summary Literature survey and patents filled revealed that microneedle‐based drug delivery system can be explored as a potential tool for the delivery of a variety of macromolecules that are not effectively delivered by conventional transdermal techniques.     

Effect of microneedle on the pharmacokinetics of ketoprofen from its transdermal formulations

Non-invasive transdermal delivery using microneedle arrays was recently introduced to deliver a variety of large and hydrophilic compounds into the skin, including proteins and DNA. In this study, a microneedle array was applied to the delivery of a hydrophobic drug, ketoprofen, to determine if transdermal delivery in rats can be improved without the need for permeation enhancers. The ability of a microneedle to increase the skin permeability of ketoprofen was tested using the following procedure. A microneedle array was inserted into the lower back skin of a rat using a clip for 10 min. Subsequently, 24 mg/kg of a ketoprofen gel was loaded on the same site where the microneedle had been applied. Simultaneously, the microneedle was coated with 24 mg/kg of a ketoprofen gel, and inserted into the skin using a clip for 10 min. As a negative control experiment, only 24 mg/kg of the ketoprofen gel was applied to the shaved lower back of a rat. Blood samples were taken at the indicated times. The plasma concentration (C_p) was obtained as a function of time (t), and the pharmacokinetic parameters were calculated using the BE program. The group loaded with the microneedle coated with ketoprofen gel showed a 1.86-fold and 2.86-fold increase in the AUC and C_max compared with the ketoprofen gel alone group. These results suggest that a microneedle can be an ideal tool for transdermal delivery products.     

Touch-actuated microneedle array patch for closed-loop transdermal drug delivery

To date, only approximately 20 drugs synthesized with small molecules have been approved by the FDA for use in traditional transdermal patches (TTP) owing to the extremely low permeation rate of the skin barrier for macromolecular drugs. A novel touch-actuated microneedle array patch (TMAP) was developed for transdermal delivery of liquid macromolecular drugs. TMAP is a combination of a typical TTP and a solid microneedle array (MA). High doses of liquid drug formulations, especially heat-sensitive compounds can be easily filled and stored in the drug reservoir of TMAPs. TMAP can easily penetrate the skin and automatically retract from it to create microchannels through the stratum corneum (SC) layer using touch-actuated ‘press and release’ actions for passive permeation of liquid drugs. Comparison of subcutaneous injection, TTP, solid MA, and dissolvable MA, indicated that insulin-loaded TMAP exhibited the best hypoglycemic effect on type 1 diabetic rats. A ‘closed-loop’ permeation control was also provided for on-demand insulin delivery based on feedback of blood glucose levels (BGLs). Twenty IU-insulin-loaded TMAP maintained the type 1 diabetic rats in a normoglycemic state for approximately 11.63?h, the longest therapeutic duration among all previously reported results on microneedle-based transdermal patches. TMAP possesses excellent transdermal drug delivery capabilities.     

微针与新型经皮给药载体结合的研究进展

经皮给药系统具有给药方便、血药浓度稳定、无首过效应等优点,但皮肤的屏障作用使得药物难以透过皮肤。近年来,出现了很多新型经皮给药的药物载体,如脂质体、醇质体、囊泡等,这些能通过化学方法促进药物的经皮渗透。而微针能穿透皮肤角质层形成微孔通道,通过物理方法促进药物的渗透,将微针与新型经皮给药载体结合能显著提高药物的经皮吸收的速率。本文对微针与新型经皮给药载体结合的最新研究进行了综述,并展望了微针辅助新型药物载体经皮给药的发展前景。     

Challenges and strategies in developing microneedle patches for transdermal delivery of protein and peptide therapeutics

The birth of microneedles, an array of needles sufficiently long to penetrate epidermis but small enough to do not cause skin injury and pain feeling, has offered a highly promising solution for non-invasive delivery of protein and peptide drugs, a long-cherished desire over eighty years. However, the attempts to develop clinically feasible microneedle transdermal delivery methods encountered series of difficulties, for which a decade research efforts have yet to result in a single product. Microneedles may be incorporated into devices as skin pre-treatment tools, skin microinjectors as well as transdermal patches by their functions in drug delivery. They may also be categorized to insoluble solid microneedles, hollow microneedles, soluble/degradable solid microneedles and phase-transition microneedles by their structure and forming materials. This review article is aimed to update the progress and discuss the technical challenges raised in developing protein/peptide loaded microneedle patches.     

改装滚轮微针用于醋酸曲安奈德经皮给药的特性试验

目的:评价改装滚轮微针用于曲安奈德经皮给药的力度可控性、释药重现性和皮肤刺激性。方法:改装市售滚轮微针;石蜡切片、HE染色法观察不同微针使用力度(2.5,5.0,7.5,10.0,12.5,15.0,17.5,20.0 N)时的皮肤微孔深度,探讨改装前后其力度可控性;以离体裸鼠皮肤为屏障,Franz扩散池法考察改装前后曲安奈德经皮渗透特性;评分法测定皮肤刺激性。结果:皮肤微孔深度随微针使用力度的增加而加大,微孔深度范围由65.28~106.25 μm收窄为改装后的71.53~97.92 μm,其RSD范围由10.45%~19.69%显著下降至改装后的2.33%~9.21%。在相同微针使用力度下,曲安奈德的累积释药量RSD范围由改装前的34.75%~55.92%,显著下降至改装后的14.29%~29.73%。改装滚轮微针用药1 h时出现轻度皮肤刺激性,之后消失。结论:与市售滚轮微针相比,改装滚轮微针具有较好的力度可控性、释药重现性,以及较小的皮肤刺激性。     

The effects of calcium chloride and sodium chloride on the electroporation-mediated skin permeation of fluorescein isothiocyanate (FITC)-dextrans in vitro

We previously reported the substantial synergic effects of electroporation and electrolytes, particularly those containing CaCl(2) on the skin permeation of the model low-molecular weight compound, calcein. We then investigated the effects of electroporation (300 V, 10 msx10 times) and 150 mM NaCl or CaCl(2) on skin permeation of higher molecular weight compounds, fluorescein isothiocyanate (FITC)-dextrans (FD-4, FD-10 and FD-40; average molecular weight, 4.4, 9.6 and 35.6 kDa, respectively) using excised hairless rat skin. The observed steady state flux of FD-4 was 1.3 pmol/cm(2)/h after electroporation without NaCl or CaCl(2). The flux did not differ greatly from that without electroporation. In contrast, a much higher steady state flux was observed after electroporation with NaCl or CaCl(2) (2.5 and 8.2 pmol/cm(2)/h, respectively). For FD-10 and FD-40, no flux was detected with electroporation in water (without electrolytes) or without electroporation. On the other hand, high skin permeation was observed after electroporation in NaCl or CaCl(2) solution (FD-10: 7.5 and 18.2 pmol/cm(2)/h, FD-40: 4.5 and 9.3 pmol/cm(2)/h in NaCl and CaCl(2), respectively). The effects of CaCl(2) on FD permeation were greater than those of NaCl. The present finding suggests that electroporation application in the presence of electrolytes, particularly CaCl(2), was very effective in increasing transdermal delivery of water-soluble macromolecules.     

Bioequivalence of marketed transdermal delivery systems for tulobuterol

Tulobuterol permeation through skin from various transdermal delivery systems has been compared for the bioequivalence among devices marketed. Both the permeation profiles across the hairless mouse skin and the release profiles from the devices were measured under well-controlled in vitro conditions. The release rate of the drug from the devices was appreciably higher than the penetration rate across the intact skin, indicating the skin-controlled delivery systems. However the deviation between the release rate and the permeation rate differs depending upon the system design. The brand patch showed the least difference between the release and permeation profiles among the brand and three generic devices examined. From the in vitro permeation profiles for both intact and stripped skins, the diffusion coefficient and the partition coefficient were evaluated on the basis of bi-layer skin model. The effect of the stratum corneum thickness was then simulated by SKIN-CAD. The simulated profile has suggested that the clinical performance for transdermal tulobuterol delivery is influenced not only by the thickness of the stratum corneum but by the device design as well. This is particularly the case for the stratum corneum, thinner than about 10 microm or damaged skin with the decreased barrier capacity. For the stratum corneum thicker than 20 microm, on the other hand, the clinical performance may not be significantly influenced by the device designs investigated in this study.     

Microneedle/nanoencapsulation-mediated transdermal delivery: Mechanistic insights

A systematic study was undertaken to gain more insight into the mechanism of transdermal delivery of nanoencapsulated model dyes across microneedle (MN)-treated skin, a complex process not yet explored. Rhodamine B (Rh B) and fluorescein isothiocyanate (FITC) as model hydrophilic and hydrophobic small/medium-size molecules, respectively, were encapsulated in poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) and delivered through full thickness porcine skin pretreated with MN array. Permeation through MN-treated skin was affected by physicochemical characteristics of NPs and the encapsulated dyes. Dye flux was enhanced by smaller particle size, hydrophilicity, and negative zeta potential of NPs. Regarding encapsulated dyes, solubility at physiological pH and potential interaction with skin proteins proved to outweigh molecular weight as determinants of skin permeation. Data were verified using confocal laser scanning microscopy imaging. Findings coupled with the literature data are supportive of a mechanism involving influx of NPs, particularly of smaller size, deep into MN-created channels, generating depot dye-rich reservoirs. Molecular diffusion of the released dye across viable skin layers proceeds at a rate determined by its molecular characteristics. Data obtained provide mechanistic information of importance to the development of formulation strategies for more effective intradermal and transdermal MN-mediated delivery of nanoencapsulated therapeutic agents.     

Microinfusion Using Hollow Microneedles

Purpose The aim of the study is to determine the effect of experimental parameters on microinfusion through hollow microneedles into skin to optimize drug delivery protocols and identify rate-limiting barriers to flow. Methods Glass microneedles were inserted to a depth of 720–1080 μm into human cadaver skin to microinfuse sulforhodamine solution at constant pressure. Flow rate was determined as a function of experimental parameters, such as microneedle insertion and retraction distance, infusion pressure, microneedle tip geometry, presence of hyaluronidase, and time. Results Single microneedles inserted into skin without retraction were able to infuse sulforhodamine solution into the skin at flow rates of 15–96 μl/h. Partial retraction of microneedles increased flow rate up to 11.6-fold. Infusion flow rate was also increased by greater insertion depth, larger infusion pressure, use of a beveled microneedle tip, and the presence of hyaluronidase such that flow rates ranging from 21 to 1130 μl/h were achieved. These effects can be explained by removing or overcoming the large flow resistance imposed by dense dermal tissue, compressed during microneedle insertion, which blocks flow from the needle tip. Conclusions By partially retracting microneedles after insertion and other methods to overcome flow resistance of dense dermal tissue, protocols can be designed for hollow microneedles to microinfuse fluid at therapeutically relevant rates.     

Rapid Intradermal Delivery of Liquid Formulations Using a Hollow Microstructured Array

Purpose

The purpose of this work is to demonstrate rapid intradermal delivery of up to 1.5 mL of formulation using a hollow microneedle delivery device designed for self-application.

Methods

3M??s hollow Microstructured Transdermal System (hMTS) was applied to domestic swine to demonstrate delivery of a variety of formulations including small molecule salts and proteins. Blood samples were collected after delivery and analyzed via HPLC or ELISA to provide a PK profile for the delivered drug. Site evaluations were conducted post delivery to determine skin tolerability.

Results

Up to 1.5 mL of formulation was infused into swine at a max rate of approximately 0.25 mL/min. A red blotch, the size of the hMTS array, was observed immediately after patch removal, but had faded so as to be almost indistinguishable 10 min post-patch removal. One-mL deliveries of commercial formulations of naloxone hydrochloride and human growth hormone and a formulation of equine anti-tetanus toxin were completed in swine. With few notable differences, the resulting PK profiles were similar to those achieved following subcutaneous injection of these formulations.

Conclusions

3M??s hMTS can provide rapid, intradermal delivery of 300?C1,500 µL of liquid formulations of small molecules salts and proteins, compounds not typically compatible with passive transdermal delivery.     

曲尼司特巴布剂的研制及释放度测定

目的:制备曲尼司特巴布剂并研究其体外释药性能.方法:以水溶性高分子材料为主要基质,以巴布剂基质的成型时间为指标,考察影响巴布剂物理性状和影响因素;进行体外释放度的测定,研究巴布剂的透皮释放行为.结果:巴布剂最佳处方为:曲尼司特 0.5 g,聚乙烯醇 6 g,水溶性高分子材料 25 g,甘油 5 g,丙二醇 5 g,氮酮 5 g,蒸馏水加至 150 g;4天药物释放率大于80%.结论:曲尼司特巴布剂含水量高,皮肤水合效果好,无刺激性;符合皮肤缓释型透皮给药系统的要求.     

新型经皮传递胰岛素透明质酸微针制剂的制备及性能考察

目的证明透明质酸微针制剂在药物经皮传递系统方面的应用前景。方法通过皮肤及微针的显微照片考察微针刺入皮肤的性能和在大鼠体内的溶解性能;用皮肤刺激性实验评价透明质酸微针的安全性;以人的离体皮肤为透皮释药模型,通过体外经皮通透实验考察微针对模型药物胰岛素经皮吸收的促进作用。结果微针能够均匀刺穿角质层,在皮肤表面产生与微针一致的阵列形状,在皮肤断面可观察到直至真皮层的通道;在大鼠体内使用1 h后,针体能够完全溶解,皮肤刺激性指数为1.7,属于轻度刺激性;体外经皮实验中,微针中的胰岛素能够以活性形式释放,与同剂量的溶液相比,微针对胰岛素的体外经皮吸收具有显著的促进作用,稳态通透速率达75.33×10-6U.cm-2.h-1。结论以透明质酸为基质制备的微针具有良好的皮肤刺入性、溶解性和轻度的刺激性,对于生物大分子类药物的经皮吸收有明显的促进作用,具有良好的开发前景。