Recent advances in gel technologies for topical and transdermal drug delivery

Transdermal drug delivery systems are a constant source of interest because of the benefits that they afford in overcoming many drawbacks associated with other modes of drug delivery (i.e. oral, intravenous). Because of the impermeable nature of the skin, designing a suitable drug delivery vehicle that penetrates the skin barrier is challenging. Gels are semisolid formulations, which have an external solvent phase, may be hydrophobic or hydrophilic in nature, and are immobilized within the spaces of a three-dimensional network structure. Gels have a broad range of applications in food, cosmetics, biotechnology, pharmatechnology, etc. Typically, gels can be distinguished according to the nature of the liquid phase, for example, organogels (oleogels) contain an organic solvent, and hydrogels contain water. Recent studies have reported other types of gels for dermal drug application, such as proniosomal gels, emulgels, bigels and aerogels. This review aims to introduce the latest trends in transdermal drug delivery via traditional hydrogels and organogels and to provide insight into the latest gel types (proniosomal gels, emulgels, bigels and aerogels) as well as recent technologies for topical and transdermal drug delivery.     

Self‐Assembly of Hyperbranched Polymers and Its Biomedical Applications

Hyperbranched polymers (HBPs) are highly branched macromolecules with a three‐dimensional dendritic architecture. Due to their unique topological structure and interesting physical/chemical properties, HBPs have attracted wide attention from both academia and industry. In this paper, the recent developments in HBP self‐assembly and their biomedical applications have been comprehensively reviewed. Many delicate supramolecular structures from zero‐dimension (0D) to three‐dimension (3D), such as micelles, fibers, tubes, vesicles, membranes, large compound vesicles and physical gels, have been prepared through the solution or interfacial self‐assembly of amphiphilic HBPs. In addition, these supramolecular structures have shown promising applications in the biomedical areas including drug delivery, protein purification/detection/delivery, gene transfection, antibacterial/antifouling materials and cytomimetic chemistry. Such developments promote the interdiscipline researches among surpramolecular chemistry, biomedical chemistry, nano­technology and functional materials.     

磷酸钙微球骨修复材料研究进展

磷酸钙微球具有良好的渗透性、高的比表面积、低致密度和较好的力学性能,在分离、催化、传感、组织工程和药物释放等方面均有应用。本文综述了近年来磷酸钙陶瓷微球在组织工程和药物释放等骨修复相关领域的研究进展, 介绍了实心、多孔、空心和花瓣状等四种不同结构磷酸钙陶瓷微球制备方法以及在骨修复领域中的应用, 并归纳总结了各类微球具有的优缺点和改进的方向, 为骨修复用磷酸钙微球的设计和制备提供较系统的参考。     

温度敏感型可生物降解高分子凝胶的研究进展

温度敏感型高分子凝胶因能随环境温度的变化发生可逆的相变或体积变化而被作为药物控释体系的载体之一,成为近年来研究的热点.但目前许多温敏型凝胶的非生物降解性限制了其在生物医学领域中的实际应用.因此,在温敏聚合物中引入生物降解性物质,使凝胶同时具有温敏和生物降解功能,将其用于药物释放体系,具有广阔的应用前景.结合近年来的研究报道,阐述了几类重要的温敏可生物降解凝胶及其在药物控制释放中的应用.     

Electrospun sandwich configuration nanofibers as transparent membranes for skin care drug delivery systems

The development of biocompatible nanocomposites for biomedical applications such as drug release has attracted increasing attention in recent years. In this work, electrospun membranes composed of polycaprolactone (PCL) and shellac were fabricated because PCL has favorable mechanical and biological properties, such as high biocompatibility and biodegradability. Meanwhile, shellac is biocompatible and non-toxic; as a result, the fabricated membranes are attractive for controlled drug delivery. Here, PCL/shellac/PCL nanofiber membranes were treated by ethanol vapor to improve their properties for use in drug delivery applications. Salicylic acid was loaded in the drug delivery system as a model drug, and three PCL/shellac/PCL membrane configurations were investigated. Ethanol vapor treatment increased the tensile strength, flexibility, and transparency of the membranes. Both the tensile strength and drug release properties of the membranes strongly depended on the ratio of PCL to shellac.     

A Preliminary Investigation of a Novel Series of Silica Gels

Silica gels may be produced by the hydrolytic polycondensation of organic silicates such as tetraethyl ortho silicate (TEOS) under appropriate conditions. These systems are of interest to the ceramic industry for making high purity silicate glasses at low temperatures. These silica gels may have application as drug delivery systems.

The gelation rates due to the hydrolytic polycondensation process depend on the concentration of TEOS and water, the temperature, and the presence of acid or base catalysts. A wide variety of polymeric silica gels having different polymeric matrices and pore sizes are possible. Of the alcohols and glycols screened for silica gel formulation, ethanol and glycerol appear to have a unique role in the gelation process although they do not appear to contribute directly to the hydrolytic polycondensation process.     

Recent advances in ocular drug delivery

Amongst the various routes of drug delivery, the field of ocular drug delivery is one of the most interesting and challenging endeavors facing the pharmaceutical scientist. Recent research has focused on the characteristic advantages and limitations of the various drug delivery systems, and further research will be required before the ideal system can be developed. Administration of drugs to the ocular region with conventional delivery systems leads to short contact time of the formulations on the epithelium and fast elimination of drugs. This transient residence time involves poor bioavailability of drugs which can be explained by the tear production, non-productive absorption and impermeability of corneal epithelium. Anatomy of the eye is shortly presented and is connected with ophthalmic delivery and bioavailability of drugs. In the present update on ocular dosage forms, chemical delivery systems such as prodrugs, the use of cyclodextrins to increase solubility of various drugs, the concept of penetration enhancers and other ocular drug delivery systems such as polymeric gels, bioadhesive hydrogels, in-situ forming gels with temperature-, pH-, or osmotically induced gelation, combination of polymers and colloidal systems such as liposomes, niosomes, cubosomes, microemulsions, nanoemulsions and nanoparticles are discussed. Novel ophthalmic delivery systems propose the use of many excipients to increase the viscosity or the bioadhesion of the product. New formulations like gels or colloidal systems have been tested with numerous active substances by in vitro and in vivo studies. Sustained drug release and increase in drug bioavailability have been obtained, offering the promise of innovation in drug delivery systems for ocular administration. Combining different properties of pharmaceutical formulations appears to offer a genuine synergy in bioavailability and sustained release. Promising results are obtained with colloidal systems which present very comfortable conditions of use and prolonged action.     

空心微球型材料的制备及应用进展

空心微球型材料由于具有特殊的空心结构而致使其具有许多独特的物理化学性质,因而具有广阔的应用前景.综述了近几年来空心微球材料的制备方法,如喷雾反应法、模板法、微乳液聚合法等,并简要介绍了空心微球型材料在药物输送系统、催化剂及建材等应用方面的研究进展.     

Starch-based microspheres produced by emulsion crosslinking with a potential media dependent responsive behavior to be used as drug delivery carriers

This paper describes the development and characterization of starch microspheres for being used as drug delivery carriers in tissue engineering applications. The developed starch microspheres can be further loaded with specific growth factors and immobilized in scaffolds, or administrated separately with scaffolds. Furthermore and due to the processing conditions used, it is expected that these microspheres can be also used to encapsulate living cells. The aim of this study was to evaluate the efficacy of this methodology for further studies with biologically active agents or living cells. The starch microspheres were prepared using an emulsion crosslinking technique at room temperature to allow for the loading of biologically active agents. A preliminary study was performed to evaluate the incorporation of a model drug (nonsteroidal anti-inflammatory drug-NSAID) and investigate its release profile as function of changes in the medium parameters, such as ionic strength and pH. The developed starch-based drug delivery system has shown to be dependent on the ionic strength of the release medium. From preliminary results, the release seems to be pH-dependent due to the drug solubility. It was found that the developed microspheres and the respective processing route are appropriate for further studies. In fact, and based in the processing conditions and characterization, the developed system present a potential for the loading of different growth factors or even living cells on future studies with these systems for improving bone regeneration in tissue engineering, especially because the crosslinking reaction of the microspheres takes place at room temperature.     

铁氧化物纳米晶自组装空心微球的制备、表征及其应用

铁氧化物纳米材料和纳米结构空心微球分别代表了材料研究中组分和结构的研究热点. 而由铁氧化物纳米晶自组装形成的空心微球的研究则是二者相结合, 具有重要的科学意义和良好的应用前景. 虽然已发展了多种方法制备各种单质及化合物的空心微球, 但铁氧化物纳米晶自组装空心微球的制备方法报道较少. 本文简要介绍了近几年发展起来的多种铁氧化物纳米晶自组装空心微球的一些制备方法, 利用上述方法, 制备出了多种不同组成单元、不同尺寸、不同空心程度的铁氧化物纳米晶自组装空心微球, 对所制备的铁氧化物纳米晶自组装空心微球进行了表征, 并初步介绍了所制备的铁氧化物纳米晶自组装空心微球在药物缓释和环境领域中的应用.     

丝素蛋白柔性电子器件材料的研究进展

丝素蛋白材料凭借良好的生物相容性、可控生物降解性、再生形貌多样性等已被制成柔性电子器件在电子领域进行了应用研究.本文首先综述不同溶解方法对蚕丝再生材料制备的影响,同时对丝素蛋白材料的(微球、膜、纤维、凝胶、支架等)制备方法、材料性能进行分析,最后总结了近年来丝素蛋白基柔性电子材料的应用研究进展.尽管已有研究表明可获得各...     

Fabrication and dissolution behavior of hollow hydroxyapatite microspheres intended for controlled drug release

Hollow hydroxyapatite (HA) microspheres were fabricated by a simple spray drying method in this study. Moreover, the dissolution behavior of these hollow HA microspheres after immersion in simulated body fluid (SBF) was also studied. The results indicated that the dissolution of the HA microspheres in SBF is not homogeneous in a layer-by-layer fashion but was preferential at different locations of the particle surface. Generically, dissolution preferentially occurs on the location with looser structure and high porosity of the microspheres. The degradable HA microspheres are expected to have potential applications in bone local drug delivery systems.     

Microemulsions as a Surrogate Carrier for Dermal Drug Delivery

Microemulsions are isotropic, thermodynamically stable transparent (or translucent) systems of oil, water, and surfactant, frequently in combination with a cosurfactant with a droplet size usually in the range of 20–200 nm. Since their discovery, they have attained increasing significance both in basic research and in industry. Due to their distinct advantages such as enhanced drug solubility, thermodynamic stability, facile preparation, and low cost, uses and applications of microemulsions have been numerous. Recently, there is a surge in the exploration of microemulsion for transdermal drug delivery for their ability to incorporate both hydrophilic (5-fluorouracil, apomorphine hydrochloride, diphenhydramine hydrochloride, tetracaine hydrochloride, and methotrexate) and lipophilic drugs (estradiol, finasteride, ketoprofen, meloxicam, felodipine, and triptolide) and enhance their permeation. Very low surface tension in conjunction with enormous increase in the interfacial area due to nanosized droplets of the microemulsion influences the drug permeation across the skin. A large number of oils and surfactants are available, which can be used as components of microemulsion systems for transdermal delivery but their toxicity, irritation potential, and unclear mechanism of action limit their use. Besides surfactants, oils can also act as penetration enhancers (oleic acid, linoleic acid, isopropyl myristate, isopropyl palmitate, etc.). The transdermal drug delivery potential of microemulsions is dependent not only on the applied constituents of the vehicle but also drastically on the composition/internal structure of the phases which may promote or hamper the drug distribution in the vehicles. This article explores microemulsion as transdermal drug delivery vehicles with emphasis on components selection for enhanced drug permeation and skin tolerability of these systems and further future directions.     

中空SiO2微球的制备及其在缓/控释应用中的新进展

中空二氧化硅(SiO₂)微球具有特殊的内部空腔、吸附渗透性好、物质传递可控等优异性能, 可储存负载并缓慢释放药物、香精、染料、菌素等客体分子, 因此在药物缓释、医学成像、环境保护以及化妆品等领域有着广阔的应用前景。根据国内外研究进展, 本文归纳对比了中空SiO₂微球几种制备方法之间的优劣差异, 着重阐述了其作为缓控释载体表现出的持久性和高效性, 以及功能化的有机/无机杂化微球在响应性控释方面的优越性。并对中空SiO₂微球作为新型缓控释载体的发展前景进行了展望。     

Cellulose acetate microspheres as floating depot systems to increase gastric retention of antidiabetic drug: formulation, characterization and in vitro-in vivo evaluation

Gastric emptying is a complex process that is highly variable and makes the in vivo performance of drug delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug delivery systems for more than 12 hours utilizing floating or hydrodynamically controlled drug delivery systems. The objective of this investigation was to develop a floating, depot-forming drug delivery system for an antidiabetic drug based on microparticulate technology to maintain constant plasma drug concentrations over a prolonged period of time for effective control of blood sugar levels. Formulations were optimized using cellulose acetate as the polymer and evaluated in vitro for physicochemical characteristics and drug release in phosphate buffered saline (pH 7.4), and evaluated in vivo in healthy male albino mice. The shape and the surface morphology of the prepared microspheres were characterized by optical microscopy and scanning electron microscopy. In vitro drug release studies were performed and drug release kinetics were calculated using the linear regression method. Effects of stirring rate during preparation and polymer concentration on the size of microspheres and drug release were observed. The prepared microspheres exhibited prolonged drug release (more than 10 hours) and remained buoyant for over 10 hours. Spherical and smooth-surfaced microspheres with encapsulation efficiency ranging from 73% to 98% were obtained. The release rate decreased and the mean particle size increased at higher polymer concentrations. Stirring speed affected the morphology of the microspheres. This investigation revealed that upon administration, the biocompatible depot-forming polymeric microspheres controlled the drug release and plasma sugar levels more efficiently than plain orally given drug. These formulations, with their reduced frequency of administration and better control over drug disposition, may provide an economic benefit to the user compared with products currently available for diabetes control.     

聚合物水凝胶研究进展

对近十几年来聚合物水凝胶的制备、凝胶网络结构、特性以及水凝胶在工业、农业和科学研究等方面的应用作了比较全面的综述．     

Tetracycline-encapsulated P(3HB) microsphere-coated 45S5 Bioglass®-based scaffolds for bone tissue engineering

Bioglass^®-based scaffolds for bone tissue engineering have been developed, which can also serve as carriers for drug delivery. For this, P(3HB) microspheres (PMSs) loaded with tetracycline were fabricated and immobilised on the scaffold surfaces by a modified slurry dipping technique. The sustained drug delivery ability in simulated body fluid was confirmed by using UV–Vis absorption spectroscopy measurements. The MTT assay using mouse fibroblast cells provided evidence that the tetracycline loaded microspheres produced in this study show limited cytotoxicity. The scaffolds developed in this work provide mechanical support, adequate 3D surface roughness, bioactivity and controlled drug delivery function, and are thus interesting candidates for bone tissue engineering applications.     

超疏水表面的制备技术及其应用

就超疏水膜的制备技术及其应用的最新成果进行了概括.利用含氟材料极低的表面能,将掺杂技术、气相沉积、溶液凝胶、等离子刻蚀、等离子沉积、碳纳米管阵列排布等技术有机结合,可获得适宜的表面粗糙度和微观构造,能显著提高材料的超疏水性能.其独特超疏水的性质,在国防、工农业生产和日常生活中有着广泛的应用前景.     

Swelling and diffusion of PNIPA-based gels for localized chemotherapy and hyperthermia

This paper presents the results of an experimental study of the swelling and diffusion of poly(N-iso-propyl-acrylamide) PNIPA-based gels with the potential for applications in bio-micro-electro-mechanical systems (BioMEMS) for localized cancer treatment that involves both chemotherapy and hyperthermia. The swelling due to the uptake of water, rhodamine dye and the cancer drug, paclitaxel, are studied using weight gain experiments that are conducted over a range of temperatures in which hyperthermia can occur during drug delivery. The release of rhodamine dye and paclitaxel is also elucidated by considering their diffusion through the gels. The underlying mechanisms of diffusion and swelling are discussed over a temperature range in which synergistic cancer treatment can be effected by the combined use of hyperthermia and chemotherapy.     

BCP ceramic microspheres as drug delivery carriers: synthesis,characterisation and doxycycline release

Resorbable ceramics such as biphasic calcium phosphates (BCP) are ideal candidates as drug delivery systems. The BCP ceramic is based on the optimum balance of the most stable hydroxyapatite (HA) phase and more soluble tricalcium phosphate phase (TCP). Doxycycline is a broad-spectrum antibiotic used for the local treatment of periodontitis. The development of BCP microspheres and its release kinetics with doxycycline have been studied. The BCP ceramic powder were prepared by microwave processing and characterised by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) methods. The BCP microspheres were formed by liquid immiscibility effect using gelatin and paraffin oil. Difference in the morphology of the microspheres as a function of gelatin content has been observed. Scanning electron microscope indicated spherical and porous morphology of the microspheres. Drug incorporation was studied at varying pH and the pH 7 was found to be optimal for drug loading. Release pattern tend to depend on the morphology of BCP microspheres. An optimum release of 80% drug has been observed for BCP microsphere with HA:TCP = 65:35 ratio. The surface area measurement results also correlate with drug release obtained.