热敏脂质体

目的:综述热敏脂质体的原理和它作为靶向药物载体的应用。方法:论述了脂质体相变的原理和热敏脂质体的研究概况,以及携带化疗药物的热敏脂质体和肿瘤热疗结合后治疗效果的增强作用,指出了热敏脂质体的发展前景。结果:热敏脂质体有良好的热靶向性,在肿瘤治疗方面效果明显。结论:热敏脂质体是新一代热靶向药物载体,有重要的开发价值。     

主动靶向热敏脂质体在肿瘤光热治疗中的应用研究

靶向热敏脂质体是近年来新兴起的一种新型药物载体,其以低毒、靶向、高效等优点受到相关研究者们越来越多的关注。为了进一步提高抗肿瘤药物的靶向性、治疗效果和生物利用度,更多功能更多新靶点的热敏脂质体出现,且在肿瘤的光热治疗中扮演着重要角色。将其与光热治疗相结合,可进一步提高肿瘤的治疗效果。经过查阅和整理近年来国内外相关文献,综述当前主动靶向热敏脂质体的研究现状并展望其在肿瘤光热治疗中的发展前景。     

热敏靶向脂质体在肿瘤治疗中的研究进展

介绍热敏靶向脂质体在肿瘤热疗中的应用以及国内外研究的现状，并介绍热敏长循环脂质、磁性热敏脂质体、免疫热敏脂质体和多聚物热敏脂质体等新型热敏靶向脂质体的特点和应用。     

热敏脂质体的研究进展

综述以二棕榈酰磷脂酰胆碱（DPPC）等为主要膜材的常规热敏脂质体以及磁性热敏脂质体、长循环热敏脂质体、多聚物热敏脂质体、热敏免疫脂质体的研究进展。以热敏脂质体为载体包埋化疗药物,可结合热疗的优势和靶向给药的特点,提高治疗靶向性,降低全身毒性,增强抗肿瘤疗效。     

磁性热敏脂质体的研究进展

磁性热敏脂质体是近年来兴起的一种新型靶向药物载体,它可以在外加磁场的作用下随血液循环聚集到靶器官,在不加磁场或正常体温条件下应使包裹在脂质体中的药物缓慢、平稳释放并起到药品储库作用;而在体外交变磁场作用下产热达到热敏脂质体相变温度而控制包裹在脂质体中的药物迅速释放,以达到在肿瘤组织靶向、多次和脉冲式给药的效果。与普通脂质体相比,磁性热敏脂质体具有更强的组织靶向性和控释特性。本文综述了磁性热敏脂质体的制备、磁定位靶向性和热敏释药性。     

抗肿瘤热敏靶向脂质体的研究进展

脂质体具有靶向传递药物进入肿瘤部位的优势,被广泛用于肿瘤的临床治疗,但是靶向传递并不能保证药物在肿瘤部位被生物利用。为了解决此问题,热敏靶向脂质体(TTL)已经成为目前的研究热点。TTL既能提高药物在肿瘤部位的浓度,又能在加热条件下触发释放所载药物,从而显著改善所载药物的抗肿瘤效果。本文主要综述了近年来该领域的研究进展。     

脑靶向脂质体的研究进展

血脑屏障的存在使得大部分药物无法进入大脑,从而加大了中枢神经系统疾病的治疗难度。表面修饰的脂质体或一些特殊性质的脂质体可以作为特定的药物载体,将药物运输到相应组织或器官内。该文介绍了近年来脂质体脑靶向制剂,包括经表面修饰的脂质体、热敏脂质体和前阳离子脂质体等的研究进展。     

电磁波控制热敏磁性脂质体靶向给药

本文从新型靶向给药系统-热敏磁性脂质体靶向给药的几个关键之处出发，介绍了目前热敏磁性脂质体的脂质材料、磁性材料、磁定位和电磁波控释研究状况，分析讨论了电磁波在热敏磁性脂质体的磁靶向和药物控释方面的作用,并提出了测量热敏磁性脂质体的电磁参数和选择合适的电磁波频段用于药物控释的必要性。     

靶向脂质体的研究进展

随着对脂质体研究的不断深入,靶向脂质体的研究也取得了很大的进步。靶向脂质体是理想的药物载体,具有高靶向性,低毒性,长效缓释性的优点,近年来成为肿瘤靶向治疗的研究热点。本文主要围绕靶向脂质体的分类及其优缺点,综述了靶向脂质体的研究进展,为脂质体的进一步研究提供参考。     

磁性药物载体在抗肿瘤方面的研究进展

通过外加磁场的引导作用,使负载抗癌药物的磁性载体靶向定位于靶区,提高靶组织的药物浓度,有效降低药物对正常组织或细胞的毒副作用及其他不良反应。磁性药物载体还具有靶向性、缓释、控释等优点,已成为了肿瘤靶向治疗常用的新型载体系统。本文综述了磁性药物载体磁性纳米颗粒、磁性脂质体、磁性微球在肿瘤治疗与诊断中的应用进展。     

Targeted thermosensitive liposomes: an attractive novel approach for increased drug delivery to solid tumors

Introduction: Currently available chemotherapy is hampered by a lack in tumor specificity and resulting toxicity. Small and long-circulating liposomes can preferentially deliver chemotherapeutic drugs to tumors upon extravasation from tumor vasculature. Although clinically used liposomal formulations demonstrated significant reduction in toxicity, enhancement of therapeutic activity has not fully met expectations.

Areas covered: Low drug bioavailability from liposomal formulations and limited tumor accumulation remain major challenges to further improve therapeutic activity of liposomal chemotherapy. The aim of this review is to highlight strategies addressing these challenges. A first strategy uses hyperthermia and thermosensitive liposomes to improve tumor accumulation and trigger liposomal drug bioavailability. Image-guidance can aid online monitoring of heat and drug delivery and further personalize the treatment. A second strategy involves tumor-specific targeting to enhance drug delivery specificity and drug internalization. In addition, we review the potential of combinations of the two in one targeted thermosensitive-triggered drug delivery system.

Expert opinion: Heat-triggered drug delivery using thermosensitive liposomes as well as the use of tumor vasculature or tumor cell-targeted liposomes are both promising strategies to improve liposomal chemotherapy. Preclinical evidence has been encouraging and both strategies are currently undergoing clinical evaluation. A combination of both strategies rendering targeted thermosensitive liposomes (TTSL) may appear as a new and attractive approach promoting tumor drug delivery.     

A two-component drug delivery system using Her-2-targeting thermosensitive liposomes

We report on a new method for enhancing the specificity of drug delivery for tumor cells, using thermosensitive immunoliposomes. The liposomes are conjugated to the antibody trastuzumab (Herceptin^®), which targets the human epidermal growth factor receptor 2 (Her-2), a cell membrane receptor overexpressed in many human cancers. Being thermosensitive, the liposomes only release their contents when heated slightly above body temperature, allowing for the possibility of tissue targeting through localized hyperthermia. Using self-quenching calcein, we demonstrate the release of liposome contents into cell endosomes after brief heating to 42°C. To further increase targeting specificity, we incorporate the concept of a two-component delivery system that requires the interaction of two different liposomes within the same endosome for cytoplasmic delivery. Experimental evaluation of the technique using fluorescently labeled liposomes shows that a two-component delivery system, combined with intracellular disruption of liposomes by hyperthermia, significantly increases specificity for Her-2-overexpressing tumor cells.     

Heat-Induced Drug Release Rate and Maximal Targeting Index of Thermosensitive Liposome in Tumor-Bearing Mice

To evaluate the rate of drug release at the tumor and maximal drug targeting after administration of thermosensitive liposomes with hy-perthermia, a theoretical and experimental method was derived assessing the fraction of drug released from liposomes in a single pass through the heated tumor, F, and the drug targeting index when drug release occurs completely in response to heat (F = 1), DTI_max. The F and DTImax were evaluated for four types of liposomes (LUV-1 and LUV-2, thermosensitive large unilamellar liposomes; LUV-3, a nonthermosensitive large unilamellar liposome; and SUV-1, a thermosensitive small unilamellar liposome) using reported data on blood liposome levels and tumor drug levels after the liposomes were administered to tumor bearing mice. DTI_max values for LUV-1 and SUV-1 were approximately 6, while the value for LUV-2 with a relatively large systemic clearance was only 2.3. The F values for LUV-1, LUV-2, and SUV-1 with hyperthermia were 0.71, 1.17, and 0.34, respectively, whereas the values for these liposomes without hyperthermia and for LUV-3 with or without hyperthermia were nearly zero. These results confirm earlier findings that LUV-1 and LUV-2 release CDDP almost completely at the heated tumor and that the large DTI value obtained in LUV-1 (DTI = 4.6) was due to its high heat sensitivity and its small systemic clearance.     

Targeted delivery of antibiotics using liposomes and nanoparticles: research and applications

This review examines current technologies for increasing the bioavailability of antibiotics by means of liposomes or nanoparticles. The main focus is on liposomes. These carriers were preferentially developed because their composition is compatible with biological constituents. Biodegradable polymers in the form of colloidal particles have also been used and show promise for future applications in antimicrobial chemotherapy. The in vivo behaviour of both types of carriers and consequently their therapeutic potential, are determined by their route of administration. Conventional carrier strategies permit the mononuclear phagocyte system to be targeted by intravenous injection of antibiotics. Stealthy strategies avoid major uptake by these cells and extend the systemic presence of these carriers. The purpose of this review is to provide background information in antibiotic targeting gathered from papers published over the last twenty years. It seems clear that such drug carriers (liposomes, nanoparticles) allow increased drug concentration at infected sites but reduce drug toxicity.     

Anticancer therapy using glucuronate modified long-circulating liposomes

Since conventional liposomes tend to be trapped by the reticuroendothelial systems (RES), their use as drug carriers is limited when the targets are not RES cells. Therefore, many attempts have been made to avoid the RES-trapping of liposomes. Favorable results were obtained by a modification of liposomes with a glucuronic acid derivative, PGlcUA, and polyethyleneglycol. These liposomes have a long-circulating character, and showed the further advantage for passive targeting to tumor tissues, since the vasculature in tumor tissues is leaky enough for small-sized liposomes to extravasate. Thus long-circulating liposomes are useful for tumor imaging and treatment. PGlcUA-modified liposomes were actually found to accumulate effectively in tumor tissue, and showed enhanced efficacy of antitumor agents, such as adriamycin and vincristine when they were encapsulated into the liposomes. Usefulness of PGlcUA liposomes as drug carriers was also observed in photodynamic therapy and in treatment of cancer by amphiphilic novel antitumor agents.     

Increased intracellular targeting to airway cells using octaarginine-coated liposomes: in vitro assessment of their suitability for inhalation

Delivery of macromolecular drugs to airway cells after inhalation can be limited by rapid clearance, in vivo degradation, and poor intracellular targeting. Liposome carriers offer an effective method of improving drug stability, but conventional liposomes have limited intracellular targeting capacity and are cleared rapidly by the lungs. Further modification is required to improve liposome-cell interaction and intracellular targeting. Therefore, we proposed conjugating three arginine-rich membrane translocating peptides, namely, HIV-TAT, Antennapedia, and octaarginine, to neutral liposomes as a biocompatible alternative to cationic lipids for intracellular delivery of macromolecules to airway cells. Conjugation did not significantly affect liposome stability, and each system was nebulized to produce aerosols of mean aerodynamic diameter < 1.5 microm. The peptides caused a significant (p < 0.05) increase in liposome-airway cell association compared to untagged liposomes and to DOTAP liposomes. Up to 30% of the peptide-conjugated liposomes added were bound and internalized (via a temperature-dependent, endocytic process) after just 2 h. The novel carriers all delivered encapsulated dextrans rapidly and efficiently to the cytoplasm of Calu-3 cells. Once internalized by the cells, the modified carriers localize for the most part in the cytoplasm with only a small amount of nuclear localization. These peptide-conjugated liposomes were significantly (p < 0.05) less toxic than DOTAP liposomes with octaarginine-coated liposomes the least toxic. These systems, particularly octaarginine-coated liposomes, offer many advantages for drug delivery to airway epithelial cells including increased stability, improved cell binding, and cell uptake with an improved toxicity profile.     

Lymphatic targeting with nanoparticulate system

Much effort has been made to achieve lymphatic targeting of drugs using colloidal carriers. This paper reviews the recent progress in the development of biodegradable nanoparticulate systems, including nanospheres, emulsions, and liposomes. The major purpose of lymphatic targeting is to provide an effective anticancer chemotherapy to prevent the metastasis of tumor cells by accumulating the drug in the regional lymph node via subcutaneous administration. The objectives of lymph targeting also involve the localization of diagnostic agents to the regional lymph node to visualize the lymphatic vessels before surgery, and the improvement of peroral bioavailability of macromolecular drugs, like polypeptides or proteins, which are known to be selectively taken up from the Peyer's patch in the intestine. Nanocapsules, which are ultrafine oily droplet-coated polymeric substances, are probably one of the most promising candidates of colloidal carriers. Surface engineering by the interfacial deposition method can provide a suitable size distribution and necessary surface characteristics to the nanocapsules. Our recent in vivo study proved that polyisobutylcyanoacrylate nanocapsules showed enhanced accumulation of drug in the lymph node, compared with other carriers such as emulsions and liposomes.     

Development of a bone targeted thermosensitive liposomal doxorubicin formulation based on a bisphosphonate modified non-ionic surfactant

Bone is among the most common sites of metastasis in cancer patients, so it is an urgent need to develop drug delivery systems targeting tumor bone metastasis with the feature of controlled release. This study aimed to delivery of thermosensitive liposomal doxorubicin to bone for tumor metastasis treatment. First, Brij78 (polyoxyethylene stearyl ether) was conjugated with Pamidronate (Pa). By incorporating Pa-Brij78 to DPPC/Chol liposomes, we developed Pa surface functionalized liposomes. The Pa-Brij78/DPPC/Chol liposomes (PB-liposomes) exhibited a stronger binding affinity to hydroxyapatite (HA), a major component of bone, than Brij78/DPPC/Chol liposomes (B-liposomes). Doxorubicin (Dox) was then encapsulated in PB-liposomes and the results demonstrated complete release of Dox from PB-liposomes or the complex of HA/PB-liposomes within 10?min at 42?°C. Next, human lung cancer A549 cells were treated with the thermosensitive complex of HA/PB-liposomes/Dox to mimic tumor bone metastasis treatment through bone targeted delivery of therapeutic agents. Pre-incubation of HA/PB-liposomes/Dox with mild heat at 42?°C induced subsequent higher cytotoxicity to A549 cells than incubation of the same complex at 37?°C, suggesting more active drug release triggered by heat. In conclusion, we synthesized a novel surfactant Pa-Brij78 and it has the potential to be used for development of a bone targeted thermosensitive liposome formulation for treatment of tumor bone metastasis.