MEMS微针阵列及其在生物医学上的应用

利用微机械技术制作的 MEMS微针阵列是 MEMS技术在生物医学上一个重要应用 ,它为生物医学领域提供了新的医疗手段。微针技术在精确药物注射、临床监测、生化检测等领域有着广泛的发展前景。本文介绍了MEMS微针阵列在生物医学领域的三个方面的重要应用 :生物医学微针电极、经皮药物传输及流体采样 ,对他们的应用原理和当前的最新技术进展进行了概述 ,说明了 MEMS微针应用的特点 ,它为患者提供了无痛、高效、安全的医疗手段 ,更符合医学研究人性化的特点。另外 ,讨论了微针阵列制作的一系列工艺方法。     

MEMS微针阵列干电极及其在生理电信号采集中的应用

生理电信号能直接反映人们的身体状况,且随着各种便携式设备、穿戴式设备的出现,生理电信号的采集得到越来越多的重视。近年来,许多研究人员致力于生理电信号采集电极的研究,因此基于MEMS技术的微针阵列干电极逐渐成熟。微针阵列干电极通过微针刺入被测者的皮肤,实现连续、长期、高效的生理电信号采集,由于其成本低、操作简单、不会使被测者感到不适、采集质量高等优点,逐渐取代传统湿电极而得到越来越广泛的应用。通过将微针阵列干电极与湿电极进行对比,突出微针阵列干电极的研究价值;结合国内外最新研究,综述微针阵列干电极的制作工艺、微针阵列干电极的改进技术、在生理电信号采集中的应用现状;讨论目前微针阵列干电极存在的不足,并对以后的发展趋势进行展望。     

微针介导的浅表肿瘤治疗研究进展

作为一种新兴的给药方式,微针透皮给药具有微创无痛、安全高效、使用方便及改善患者依从性等优点.在浅表肿瘤治疗中,微针可以有效刺穿皮肤角质层,将负载的药物高效传递并富集于肿瘤部位,从而避免肝脏首过效应,防止胃肠道副作用,可极大地提高药物的利用率.在相同剂量下,相对于静脉注射给药及肿瘤内注射给药,微针透皮给药表现出更好的治疗...     

重组金黄色葡萄球菌肠毒素B蛋白可溶性微针制备及免疫效果研究

目的建立重组金黄色葡萄球菌肠毒素B(SEB)蛋白的可溶性微针体外检测方法及体内免疫效果评价。方法通过动态光散射(DLS)检测蛋白粒径、BCA法检测单片微针的蛋白浓度、活体成像实验检测微针皮内注射后蛋白在体内的停留时间,通过DRIZE评分评价微针注射后的皮肤情况,通过动物实验评价重组SEB蛋白可溶性微针的免疫原性及免疫保护效果。结果DLS分析显示SEB蛋白可溶性微针负载的重组SEB蛋白粒径与重组SEB蛋白溶液中的SEB蛋白粒径无明显差别,单片微针中重组SEB蛋白含量为(13.2±1.4)μg,活体成像实验显示相对于肌肉注射,重组SEB蛋白可溶性微针皮内给药后荧光蛋白在体内的停留时间延长,动物实验显示13.0μg的重组SEB蛋白可溶性微针即能引发免疫反应,并且在2LD50SEB攻毒剂量下能够产生很好保护效果。结论重组SEB蛋白可溶性微针能够刺激小鼠机体产生较好的免疫原性及免疫保护效果,为发展疫苗新型免疫途径提供了新策略。     

皮肤微针辅助治疗斑秃的疗效与临床评估

目的观察1.5 mm皮肤微针辅助治疗斑秃(AA)的临床疗效以及探讨0.5 mm皮肤微针对小鼠背部毛囊生长的影响。方法招募2018年3月至2019年8月在武汉大学人民医院皮肤科门诊就诊AA患者52例,随机分为2组。对照组予以5%米诺地尔酊和0.05%卤米松乳膏外用治疗;微针组予以微针针刺皮肤联合药物治疗。此外,将C57BL/6小鼠背部脱毛后,随机分为模型组、米诺地尔组和微针组。造模后第2天分别给予相应处理,连续14 d。拍照观察生长期毛囊相关皮肤色素变化与毛发生长情况;HE染色观察毛囊的形态和数量变化;免疫组化检测毛囊上皮干细胞标记蛋白K15的表达。结果治疗12周后,微针组患者治疗总有效率优于对照组(P0.05)。微针组小鼠背部皮肤变黑时间较模型组缩短(P0.05);新生毛发长度较模型组长(P0.05);毛囊数量、K15阳性细胞数目也较模型组增多(P0.05)。结论微针可能通过激活毛囊上皮干细胞促进毛发生长,有助于提高AA疗效。     

负载尼洛替尼的甲基丙烯酰化明胶微针贴片治疗心肌梗死后心脏功能障碍的研发与应用

本研究旨在评价负载尼洛替尼的生物相容性甲基丙烯酰化明胶（GelMA）微针贴片应用于心肌梗死（简称：心梗）后对心脏功能障碍的治疗作用,为临床抗心肌纤维化治疗提供新的思路。本研究在心梗造模后10 d（疤痕成熟期）,将GelMA微针贴片贴附于心外膜表面,靶向梗死及周围区递送抗纤维化药物尼洛替尼。在心梗造模后28 d,通过超声心动图、血浆脑型利钠肽、心重/体重比等指标评价心脏功能和左室重构情况;通过小麦胚芽凝集素染色评价心肌肥大情况;通过苏木精—伊红染色、天狼星红染色评价心肌纤维化情况。结果显示,相较于心梗对照组及使用空白GelMA微针贴片治疗组,负载尼洛替尼的GelMA微针贴片可减轻心肌肥大和梗死周围区纤维化过度扩张,从而预防不良心室重构,改善心功能。本研究所提这一治疗策略是纠正心梗后心脏功能障碍的一次有益尝试,有望成为纠正心梗后心脏功能障碍的新策略,对改善心梗患者的长期预后具有重要的临床意义。     

流感病毒灭活疫苗可溶性微针制备及评价

目的初步研究负载流感全病毒灭活疫苗可溶性微针体外评价方法和经皮免疫效果。方法将流感全病毒灭活疫苗溶液与微针基质材料混匀干燥后复溶,体外血凝试验检测疫苗血凝素活性,透射电镜和动态光散射分析疫苗微针复溶后流感全病毒疫苗变化情况;选择筛选的材料羧甲基纤维素和硫酸软骨素作为主要基质与疫苗混匀制备微针溶液,滴加到微针制作模具上,抽真空使疫苗基质溶液填充针体,室温干燥、脱模,贴于猪皮肤检测微针硬度,将Cy7标记流感疫苗可溶性微针贴于小鼠腹部后活体成像检测流感疫苗皮内存留时间,动物免疫试验第2次免疫后14 d检测血抑效价。结果通过血凝试验筛选出硫酸软骨素和羧甲基纤维素为主要基质,贴片疫苗血凝活性为96%和86%,显著高于其它3种材料贴片疫苗活性;透射电镜显示PBS对照组中流感灭活病毒颗粒多呈单个散在分布,罕见聚团,2种贴片复溶后流感灭活病毒多呈聚团,罕见单个病毒颗粒;动态光散射分析显示疫苗贴片复溶后病毒颗粒粒径明显增大,高于对照组中病毒粒径;皮肤组织病理显示2种疫苗微针均可刺穿猪皮肤;活体成像显示疫苗微针刺穿小鼠皮肤并溶解于皮内,疫苗存留时间较肌肉长;Balb/c小鼠免疫后分离血清,血凝抑制试验显示2种微针均产生血抑效价且硫酸软骨素微针血抑效价高于羧甲基纤维素微针。结论可溶性疫苗微针可刺穿皮肤溶于皮内产生免疫应答,为微针疫苗的研究提供了思路。     

柔性人造触觉神经

正近日,美国斯坦福大学、韩国首尔大学与天津南开大学联合开发了一种基于柔性有机电子器件的高灵敏度仿生触觉神经系统(人造神经),发表在《科学》杂志上。柔性有机电子器件的高灵敏度仿生触觉神经系统具有良好的生物兼容性、柔性和高灵敏度,在机器人手术、义肢感触等领域具有应用前景。人造神经的关键点技术是既要实现与生物神经系统相似的工作原理,又要与生物神经信号兼容,还要有     

血液接触面的抗凝技术——肝素涂抹

在人造物质和材料表面,移植上有活性的肝素以达到抗凝作用的技术即肝素涂抹技术(HCS)。HCS技术可在不进行全身肝素化情况下防止血液凝集和血液与高分子材料接触,达到抗凝效果,可减少体外循环术中肝素用量及其副作用。本文介绍了HCS的工艺技术、HCS的生物相容性及其临床应用。目前HCS用品价格昂贵,妨碍其推广。     

新型益智药奥拉西坦的药理与临床应用进展

益智药 (ｎｏｏｔｒｏｐｉｃｓ)是一类能促进学习 ,增强记忆力的新型中枢神经系统药物。益智药选择性地作用于大脑皮层 ,具有选择性激活、保护和促进受损神经细胞功能恢复的特性。益智药与精神抑制药、抗抑郁药、抗焦虑药、精神兴奋药和致幻剂等精神药物均不同 ,它是通过对脑细胞中生物能量代谢 (如葡萄糖、ＡＴＰ、蛋白质、ＲＮＡ、类脂等 )的同化作用 ,改善与精神行为有关的脑整合机制 ,如记忆、学习、回答问题及分析问题、解决问题的能力。它不同于精神兴奋药 ,无中枢兴奋作用。益智药的作用也不象精神兴奋药物那样只有短暂的中枢兴奋作…     

Drawing lithography for microneedles: A review of fundamentals and biomedical applications

A microneedle is a three-dimensional (3D) micromechanical structure and has been in the spotlight recently as a drug delivery system (DDS). Because a microneedle delivers the target drug after penetrating the skin barrier, the therapeutic effects of microneedles proceed from its 3D structural geometry. Various types of microneedles have been fabricated using subtractive micromanufacturing methods which are based on the inherently planar two-dimensional (2D) geometries. However, traditional subtractive processes are limited for flexible structural microneedles and makes functional biomedical applications for efficient drug delivery difficult. The authors of the present study propose drawing lithography as a unique additive process for the fabrication of a microneedle directly from 2D planar substrates, thus overcoming a subtractive process shortcoming. The present article provides the first overview of the principal drawing lithography technology: fundamentals and biomedical applications. The continuous drawing technique for an ultrahigh-aspect ratio (UHAR) hollow microneedle, stepwise controlled drawing technique for a dissolving microneedle, and drawing technique with antidromic isolation for a hybrid electro-microneedle (HEM) are reviewed, and efficient biomedical applications by drawing lithography-mediated microneedles as an innovative drug and gene delivery system are described. Drawing lithography herein can provide a great breakthrough in the development of materials science and biotechnology.     

Dissolving microneedles for transdermal drug administration prepared by stepwise controlled drawing of maltose

Dissolving microneedles, three-dimensional polymer structures with microscale cross-sectional dimensions, have been introduced as a means of safe transdermal drug delivery. Most dissolving microneedles have been fabricated using a traditional micro-casting method that cures biopolymers within three-dimensional mold, nevertheless, repeated molding process may cause damage to encapsulated drugs, a critical hurdle for clinical application. Here, we describe the stepwise controlled drawing technique that can directly fabricate dissolving microneedle from maltose by precise controlling the drawing time and the viscosity of the maltose. Controlled drawing shaped the particular sharp-conical microneedles of 1200 μm length with tip diameter of 60 μm, and dissolved within 20 min in-vivo after inserting to the skin. This technique surpasses the limitations of micro-casting for dissolving microneedle. Furthermore, transdermal delivery of impermeable hydrophilic molecules such as ascorbic acid-2-glucoside and niacinamide was confirmed as inhibition of cutaneous hypermelanosis. We anticipate that controlled drawing technique will be suitable to design dissolving microneedles for use in minimally invasive transcutaneous drug delivery to patients.     

Mass producible and biocompatible microneedle patch and functional verification of its usefulness for transdermal drug delivery

The key issues in the development of a microneedle patch as a tool for transdermal drug delivery are safety and delivery performance in addition to economical production. In this paper, novel fabrication methods for an inexpensive microneedle patch made of biocompatible polymer are reported, along with functional verifications for the fabricated microneedle patch through animal models. We combined the merits of in-line microneedles, i.e., easy and economical production, with the superior performance of two-dimensionally arrayed microneedles. One-dimensionally fabricated microneedles were assembled to make two-dimensionally arrayed patches to attain our goal. First, we fabricated strips with one-dimensionally arrayed microneedles through deep X-ray lithography on polymethylmethacrylate or another negative photoresist, SU-8, with sharply reduced exposure time. Second, we assembled microneedle strips to make two-dimensionally arrayed microneedles, which we utilized further for fabrication of molding masters. Finally, we prepared microneedle patches made of polycarbonate by hot embossing with these masters. We then demonstrated the actual delivery of exogenous materials through application on skin via animal experiments, and we found no detectable side effects such as inflammation or allergic reactions at the site of application.     

Rapid fabrication method of a microneedle mold with controllable needle height and width

The main issue of transdermal drug delivery is that macromolecular drugs cannot diffuse through the stratum corneum of skin. Many studies have pursued micro-sized needles encapsulated with drugs to overcome this problem, as these needles can pierce the stratum corneum and allow drugs to enter the circulatory system of the human body. However, most microneedle fabrication processes are time-consuming and require expensive equipment. In this study, we demonstrate a rapid method for fabricating a microneedle mold using drawing lithography and a UV-cured resin. The mold was filled with a water-soluble material, polyvinylpyrrolidone (PVP), which was then demolded to produce a water-soluble microneedle array. The results of an in vitro skin insertion test using PVP microneedles and pig ear skin demonstrated the feasibility of the microneedle mold. In addition, by controlling the viscosity of the UV-cured resin through various heat treatments, microneedles with different heights and aspect ratios were produced. Compared with other methods, this technology significantly simplifies and accelerates the mold fabrication process. In addition, the required equipment is relatively simple and inexpensive. Through this technology, we can rapidly fabricate microneedle molds with controllable dimensions for various applications.     

An array of porous microneedles for transdermal monitoring of intercellular swelling

An array of porous microneedles was developed for minimally-invasive transdermal electrolytic connection through the human skin barrier, the stratum corneum. The length of microneedle was designed to be 100 μm so that it penetrates into the epidermis layer without pain. Each microneedle was supported by a thicker cylindrical post protruding from a planar substrate to realize its effective penetration even into elastic human skin. Since this support (post and substrate) was equally porous as the needles, the needle chip was entirely permeable for electrolyte. This ion-conductive porous microneedle array was applied to the transdermal conductometry with small direct current for local monitoring of intercellular swelling, edema. The porous needle-based electrode system could be a platform for various transdermal electrical diagnosis and treatments.     

Dissolving microneedles for transdermal drug delivery

Microfabrication technology has been adapted to produce micron-scale needles as a safer and painless alternative to hypodermic needle injection, especially for protein biotherapeutics and vaccines. This study presents a design that encapsulates molecules within microneedles that dissolve within the skin for bolus or sustained delivery and leave behind no biohazardous sharp medical waste. A fabrication process was developed based on casting a viscous aqueous solution during centrifugation to fill a micro-fabricated mold with biocompatible carboxymethylcellulose or amylopectin formulations. This process encapsulated sulforhodamine B, bovine serum albumin, and lysozyme; lysozyme was shown to retain full enzymatic activity after encapsulation and to remain 96% active after storage for 2 months at room temperature. Microneedles were also shown to be strong enough to insert into cadaver skin and then to dissolve within minutes. Bolus delivery was achieved by encapsulating molecules just within microneedle shafts. For the first time, sustained delivery over hours to days was achieved by encapsulating molecules within the microneedle backing, which served as a controlled release reservoir that delivered molecules by a combination of swelling the backing with interstitial fluid drawn out of the skin and molecule diffusion into the skin via channels formed by dissolved microneedles. We conclude that dissolving microneedles can be designed to gently encapsulate molecules, insert into skin, and enable bolus or sustained release delivery.     

Investigation of cell-substrate interactions by focused ion beam preparation and scanning electron microscopy

Cell-substrate interactions, which are an important issue in tissue engineering, have been studied using focused ion beam (FIB) milling and scanning electron microscopy (SEM). Sample cross-sections were generated at predefined positions (target preparation) to investigate the interdependency of growing cells and the substrate material. The experiments focus on two cell culturing systems, hepatocytes (HepG2) on nanoporous aluminum oxide (alumina) membranes and mouse fibroblasts (L929) and primary nerve cells on silicon chips comprised of microneedles. Cross-sections of these soft/hard hybrid systems cannot be prepared by conventional techniques like microtomy. Morphological investigations of hepatocytes growing on nanoporous alumina membranes demonstrate that there is in-growth of microvilli from the cell surface into porous membranes having pore diameters larger than 200 nm. Furthermore, for various cell cultures on microneedle arrays contact between the cells and the microneedles can be observed at high resolution. Based on FIB milled cross-sections and SEM micrographs cells which are only in contact with microneedles and cells which are penetrated by microneedles can be clearly distinguished. Target preparation of biological samples by the FIB technique especially offers the possibility of preparing not only soft materials but also hybrid samples (soft/hard materials). Followed by high resolution imaging by SEM, new insights into cell surface interactions can be obtained.     

Hydrogel swelling as a trigger to release biodegradable polymer microneedles in skin

Biodegradable polymeric microneedles were developed as a method for achieving sustained transdermal drug release. These microneedles have potential as a patient-friendly substitute for conventional sustained release methods. However, they have limitations related to the difficulty of achieving separation of the needles into the skin. We demonstrated that microneedle separation into the skin was mediated by hydrogel swelling in response to contact with body fluid after the needles were inserted into the skin. The hydrogel microparticles were synthesized by an emulsification method using poly-N-isopropylacrylamide (PNIPAAm). The microneedles were fabricated by micromolding poly-lactic-co-glycolic acid (PLGA) after filling the cavities of the mold with the hydrogel microparticles. The failure of microneedle tips caused by hydrogel swelling was studied in regard to contact with water, insertion of microneedles into porcine cadaver skin in vitro, stress-strain behavior, and insertion into the back skin of a hairless mouse in vivo. The drug delivery property of the hydrogel particles was investigated qualitatively by inserting polymer microneedles into porcine cadaver skin in vitro, and the sustained release property of PLGA microneedles containing hydrogel microparticles was studied quantitatively using the Franz cell model. The hydrogel particles absorbed water quickly, resulting in the cracking of the microneedles due to the difference in volume expansion between the needle matrix polymer and the hydrogel particles. The swollen particles caused the microneedles to totally breakdown, leaving the microneedle tips in the porcine cadaver skin in vitro and in the hairless mouse skin in vivo. Model drugs encapsulated in biodegradable polymer microneedles and hydrogel microparticles were successfully delivered by releasing microneedles into the skin.     

Finite element analysis of hollow out-of-plane HfO<Subscript>2</Subscript> microneedles for transdermal drug delivery applications

Transdermal drug delivery (TDD) based on microneedles is an excellent approach due to its advantages of both traditional transdermal patch and hypodermic syringes. In this paper, the fabrication method of hollow out-of-layer hafnium oxide (HfO₂) microneedles mainly based on deep reactive ion etching of silicon and atomic layer deposition of HfO₂ is described, and the finite element analysis of the microneedles based on ANSYS software is also presented. The fabrication process is simplified by using a single mask. The finite element analysis of a single microneedle shows that the flexibility of the microneedles can be easily adjusted for various applications. The finite element analysis of a 3 × 3 HfO₂ microneedle array applied on the skin well explains the “bed of nail” effect, i.e., the skin is not liable to be pierced when the density of microneedles in array increases. The presented research work here provides useful information for design optimization of HfO₂ microneedles used for TDD applications.     

Microneedle-based drug delivery: studies on delivery parameters and biocompatibility

There is a significant interest in the application of microneedles in intradermal drug delivery systems. Previous studies have demonstrated that skin permeation of drugs can be increased by orders of magnitude with microneedle insertion. In this study, emphasis is placed on the development of low cost, painless intradermal microneedle systems that can enhance the percutaneous drug permeation. Microneedles of octagonal pyramidal shape with the length of 150 mum were employed, and the capabilities of skin permeation enhancement under different delivery conditions were examined. The delivery parameters taken into account included the insertion time and the area of insertion. It was found that when solid microneedle arrays of 150 mum in length were pierced into human dermatomed skin for 5 to 60 s, microconduits with the depth of 50 to 80 mum were created to facilitate the percutaneous permeation of drugs. In percutaneous tests, it was demonstrated that the permeability coefficient of calcein (MW = 622.55) was significantly increased by 10(4) to 10(5) times compared to that on intact skin. In terms of biocompatibility, biological evaluation indicated a broad spectrum of safety for the microneedle system. These results suggest that the octagonal pyramidal microneedles can be an effective tool in developing novel intradermal drug delivery system.