多肽介导的核酸药物递送系统研究进展

核酸药物作为新型基因治疗药物备受关注,但生物学稳定性差、易被体内核酸酶降解、生物利用度低、靶组织内聚集浓度低等是制 约其发展的主要因素。新的药物递送技术的快速发展在一定程度上解决了核酸药物的稳定性及靶向递送问题,极大地推动了核酸药物的研 发进展。尤其是多肽蛋白类递送载体,已成为核酸药物递送系统研究领域的热点之一。介绍核酸药物递送载体多肽修饰的两种主要方式—— 共价缀合和非共价络合,重点综述近年来多肽缀合物和复合物以及多肽修饰的载体在核酸药物递送系统中的应用研究,探讨多肽介导的核 酸药物递送系统在应用中存在的问题,为新型核酸药物递送系统研发提供参考。     

综述与专论: 适配体功能化外泌体在肿瘤靶向治疗中的应用

传统的肿瘤治疗方法因缺乏足够的靶向性而会产生严重的毒副作用。外泌体（exosome）是一种天然的纳米囊泡,参与细胞间的信息传递,并且作为药物递送载体具有出色的性能优势,包括低免疫原性、低毒性和能够穿越天然屏障等特点。然而以外泌体为载体的药物递送系统的靶向能力仍有不足。适配体（aptamer）是一类化学合成的单链核酸分子,具有分子质量小、易于修饰和免疫原性低等特点,可作为亲和性配体与靶向分子特异性结合。通过在外泌体表面修饰适配体,药物可以被精确递送到肿瘤细胞发生部位,从而实现对肿瘤的靶向治疗,提高肿瘤治疗效果,减少毒副作用。本篇综述将重点讨论适配体功能化外泌体药物靶向递送系统在各种肿瘤治疗方面的应用,并对其未来的挑战和机遇进行阐述。     

糖类修饰的纳米递送系统

癌症的高病发率和高死亡率已经引起了人们广泛的重视。传统治疗癌症的药物分子存在水溶性较差、无靶向性、生物安全性低等问题。纳米递送系统如脂质体、聚合物纳米粒子和共聚物胶束解决了传统癌症治疗过程中药物水溶性较差的问题。但大多数纳米递送系统不具备靶向性和生物相容性,且药物包封率不高。糖类作为具有较好的靶向特异性识别能力、安全性和生物相容性的天然有机化合物能够有效修饰纳米递送系统,能包载药物分子并有效靶向到特定器官。本文将对糖类修饰的脂质体、聚合物纳米粒子和共聚物胶束三大纳米递送系统进行综述。     

外泌体靶向递药在肿瘤治疗中的进展

外泌体是由细胞分泌、粒径为30~150 nm的纳米囊泡。外泌体具有优越的生物相容性、良好的载药功能以及便于修饰的膜表面,是一种具有潜力的药物递送载体。在肿瘤治疗研究中,可利用具有靶向识别功能的外泌体来降低脱靶效应,减少不良反应,达到增强治疗效果的目的。归纳了用不同修饰方法增强外泌体靶向性的研究进展,总结了近五年来利用外泌体作为特异性药物递送载体靶向治疗肿瘤的相关研究,阐述了外泌体作为新型药物递送载体的优势与不足,为设计具有靶向识别功能的外泌体提供了可行的方向与策略。     

浅析纳米载体靶向药物递送系统:误区、壁垒与对策

纳米载体靶向药物递送系统早已受到各国的广泛关注,虽然这一研究方向的论文发表量呈指数增加,却基本没有成药性.本文基于物理化学和生物学原理分析,通过对不同材料和粒径纳米载体扩散系数的实验研究,探讨分子与纳米粒子在水介质中依数性和扩散能力的差异、纳米载体在体内的寻靶过程,从根本上剖析了纳米载体靶向药物递送系统理论中存在的种种误区,揭示了主动靶向修饰的纳米载体并不能够按照载体设计的初衷提高对肿瘤组织的靶向效率的缺陷.证明EPR效应只适用于药物分子与具有足够扩散能力的纳米载体,并提出依靠环境特异性响应的靶向释药、提高纳米载体扩散能力、利用巨噬细胞固有的吞噬作用捕获NPs实现靶向药物递送以及逐级靶向等更具有可行性的靶向递送新策略.     

肠道病原菌侵袭素在药物纳米载体中的应用

口服给药是药物递送系统中的优选途径。然而,在通过胃肠道时,肠细胞的低渗透性经常会阻碍药物的有效递送。包囊药物能够解决这一问题的关键,取决于其中的细胞侵袭性靶向基团包裹的纳米颗粒系统。这种药物递送系统的侵入特性是由细菌侵袭素的关键成分提供,这些成分具有快速调节药物穿越肠细胞的作用,从而促进宿主细胞对药物的有效吸收。此综述重点阐述细菌侵袭系统,对合适的侵袭素分别从功能和分子结构、作为靶向药物的相对价值以及在使用过程中可能存在的误区依次进行探讨。此外,对口服给药方法的改进和未来前景也进行了讨论。     

细胞/细菌驱动的药物递送系统研究进展

细胞/细菌驱动的药物传递系统是一种有前景的药物递送策略. 该策略将具有不同优异特性的活细胞/细菌与药物有机结合,能够有效克服传统纳米药物生物利用率低、靶向性能弱、组织穿透性不强等缺陷. 得益于对目标病灶特异响应,这类药物递送系统不仅能够实现药物高效的主动靶向递送,还可以降低对正常组织的毒副作用,目前已成功运用于药物呈递,在疾病诊断和治疗领域展示了广阔的应用前景. 本文初步探讨了细胞/细菌驱动的药物递送系统的研究进展,并对其未来研究进行展望.     

新型药物递送系统研发格局分析

药物递送是通过特定的手段使活性药物成分有效地递送到目的部位,以在人类或动物中实现治疗效果的方法或过程。递送系统在控速给药、靶向给药、药物稳定性、生物相容性等方面具有重要的作用。近年来,随着药学、材料学和生物医学等相关领域的进步,从纳米尺度、细胞尺度到智能靶向递送等技术的发展使药物递送系统领域发生了巨大变化,新型药物递送系统的研究投入和市场份额持续快速增长。通过对不同载药系统的递送机制及特点进行阐述,系统梳理新兴药物递送系统技术的主要研究进展及企业竞争格局,并对相关技术的临床转化潜力和应用前景进行展望,为相关企业研发方向选择及决策提供参考。     

多肽表面修饰脂质体药物递送系统

本文通过查阅并归纳近几年相关文献,较为系统地概述了靶向活性多肽、细胞穿膜肽和靶向细胞穿膜肽等多肽表面修饰脂质体药物递送系统(drug delivery system, DDS)的研究进展。经不同活性多肽表面修饰,或可增强脂质体DDS的靶向性,或可提高药物的细胞摄取率和生物利用度。总之,多肽表面修饰的脂质体在新型DDS研究及应用中具有良好的前景。     

纳米药物递送系统在前列腺癌治疗中的应用

前列腺癌（PCa）是全球最常见的男性泌尿生殖系统恶性肿瘤。手术、内分泌治疗、放疗和化疗是PCa的主要临床治疗选择。纳米药物递送系统具有良好的可控释放特性和较好的肿瘤靶向能力，并可通过增强的渗透性和保留（EPR）效应被动靶向肿瘤。通过精巧的设计组装和外表修饰赋予纳米递药系统与众不同的肿瘤治疗效果。本文介绍用于PCa治疗的先进纳米药物递送系统以及未来发展。     

Engineering Lipid Vesicles of Enhanced Intratumoral Transport Capabilities: Correlating Liposome Characteristics with Penetration into Human Prostate Tumor Spheroids

Liposomes have been widely used delivery systems, particularly relevant to the development of cancer therapeutics. Numerous liposome-based drugs are in the clinic or in clinical trials today against multiple tumor types; however, systematic studies of liposome interactions with solid or metastatic tumor nodules are scarce. This study is describing the in vitro interaction between liposomes and avascular human prostate (LNCaP-LN3) tumor spheroids. The ability of fluorescently labelled liposomal delivery systems of varying physicochemical characteristics to penetrate within multicellular tumor spheroids has been investigated by confocal laser scanning microscopy. A variety of liposome characteristics and experimental parameters were investigated, including lipid bilayer composition, duration of liposome-spheroid interaction, mean liposome size, steric stabilization of liposomes. Electrostatic binding between cationic liposomes and spheroids was very efficient; however, it impeded any significant penetration of the vesicles within deeper layers of the tumor spheroid. Small unilamellar liposomes of neutral surface character did not bind as efficiently but exhibited enhanced penetrative transport capabilities closer to the tumor core. Polymer-coated (sterically stabilised) liposomes exhibited almost no interaction with the spheroid, indicating that their limited diffusion within avascular tissues may be a limiting step for their use against micrometastases. Multicellular tumor spheroids were used as models of solid tumor interstitium relevant to delivery systems able to extravasate from the microcapillaries or as models of prevascularized micrometastases. This study illustrates that interactions between liposomes and other drug delivery systems with multicellular tumor spheroids can offer critically important information with respect to optimizing solid or micrometastatic tumor delivery and targeting strategies.     

Engineering lipid vesicles of enhanced intratumoral transport capabilities: correlating liposome characteristics with penetration into human prostate tumor spheroids

Liposomes have been widely used delivery systems, particularly relevant to the development of cancer therapeutics. Numerous liposome-based drugs are in the clinic or in clinical trials today against multiple tumor types; however, systematic studies of liposome interactions with solid or metastatic tumor nodules are scarce. This study is describing the in vitro interaction between liposomes and avascular human prostate (LNCaP-LN3) tumor spheroids. The ability of fluorescently labelled liposomal delivery systems of varying physicochemical characteristics to penetrate within multicellular tumor spheroids has been investigated by confocal laser scanning microscopy. A variety of liposome characteristics and experimental parameters were investigated, including lipid bilayer composition, duration of liposome-spheroid interaction, mean liposome size, steric stabilization of liposomes. Electrostatic binding between cationic liposomes and spheroids was very efficient; however, it impeded any significant penetration of the vesicles within deeper layers of the tumor spheroid. Small unilamellar liposomes of neutral surface character did not bind as efficiently but exhibited enhanced penetrative transport capabilities closer to the tumor core. Polymer-coated (sterically stabilised) liposomes exhibited almost no interaction with the spheroid, indicating that their limited diffusion within avascular tissues may be a limiting step for their use against micrometastases. Multicellular tumor spheroids were used as models of solid tumor interstitium relevant to delivery systems able to extravasate from the microcapillaries or as models of prevascularized micrometastases. This study illustrates that interactions between liposomes and other drug delivery systems with multicellular tumor spheroids can offer critically important information with respect to optimizing solid or micrometastatic tumor delivery and targeting strategies.     

Pros and Cons of the Liposome Platform in Cancer Drug Targeting

Coating of liposomes with polyethylene-glycol (PEG) by incorporation in the liposome bilayer of PEG-derivatized lipids results in inhibition of liposome uptake by the reticulo-endothelial system and significant prolongation of liposome residence time in the blood stream. Parallel developments in drug loading technology have improved the efficiency and stability of drug entrapment in liposomes, particularly with regard to cationic amphiphiles such as anthracyclines. An example of this new generation of liposomes is a formulation of pegylated liposomal doxorubicin known as Doxil® or Caelyx®, whose clinical pharmacokinetic profile is characterized by slow plasma clearance and small volume of distribution. A hallmark of these long-circulating liposomal drug carriers is their enhanced accumulation in tumors. The mechanism underlying this passive targeting effect is the phenomenon known as enhanced permeability and retention (EPR) which has been described in a broad variety of experimental tumor types. Further to the passive targeting effect, the liposome drug delivery platform offers the possibility of grafting tumor-specific ligands on the liposome membrane for active targeting to tumor cells, and potentially intracellular drug delivery. The pros and cons of the liposome platform in cancer targeting are discussed vis-à-vis nontargeted drugs, using as an example a liposome drug delivery system targeted to the folate receptor.     

Pros and cons of the liposome platform in cancer drug targeting

Coating of liposomes with polyethylene-glycol (PEG) by incorporation in the liposome bilayer of PEG-derivatized lipids results in inhibition of liposome uptake by the reticulo-endothelial system and significant prolongation of liposome residence time in the blood stream. Parallel developments in drug loading technology have improved the efficiency and stability of drug entrapment in liposomes, particularly with regard to cationic amphiphiles such as anthracyclines. An example of this new generation of liposomes is a formulation of pegylated liposomal doxorubicin known as Doxil or Caelyx, whose clinical pharmacokinetic profile is characterized by slow plasma clearance and small volume of distribution. A hallmark of these long-circulating liposomal drug carriers is their enhanced accumulation in tumors. The mechanism underlying this passive targeting effect is the phenomenon known as enhanced permeability and retention (EPR) which has been described in a broad variety of experimental tumor types. Further to the passive targeting effect, the liposome drug delivery platform offers the possibility of grafting tumor-specific ligands on the liposome membrane for active targeting to tumor cells, and potentially intracellular drug delivery. The pros and cons of the liposome platform in cancer targeting are discussed vis-à-vis nontargeted drugs, using as an example a liposome drug delivery system targeted to the folate receptor.     

A tumor vasculature targeted liposome delivery system for combretastatin A4: Design, characterization, and in vitro evaluation

The objective of this study was to develop an efficient tumor vasculature targeted liposome delivery system for combretastatin A4, a novel antivascular agent. Liposomes composed of hydrogenated soybean phosphatidylcholine (HSPC), cholesterol, distearoyl phosphoethanolamine-polyethylene-glycol-2000 conjugate (DSPE-PEG), and DSPE-PEG-maleimide were prepared by the lipid film hydration and extrusion process. Cyclic RGD (Arg-Gly-Asp) peptides with affinity for αvβ3-integrins expressed on tumor vascular endothelial cells were coupled to the distal end of PEG on the liposomes sterically stabilized with PEG (long circulating liposomes, LCL). The liposome delivery system was characterized in terms of size, lamellarity, ligand density, drug loading, and leakage properties. Targeting nature of the delivery system was evaluated in vitro using cultured human umbilical vein endothelial cells (HUVEC). Electron microscopic observations of the formulations revealed presence of small unilamellar liposomes of ∼120 nm in diameter. High performance liquid chromatography determination of ligand coupling to the liposome surface indicated that more than 99% of the RGD peptides were reacted with maleimide groups on the liposome surface. Up to 3 mg/mL of stable liposomal combretastatin A4 loading was achieved with ∼80% of this being entrapped within the liposomes. In the in vitro cell culture studies, targeted liposomes showed significantly higher binding to their target cells than non-targeted liposomes, presumably through specific interaction of the RGD with its receptors on the cell surface. It was concluded that the targeting properties of the prepared delivery system would potentially improve the therapeutic benefits of combretastatin A4 compared with nontargeted liposomes or solution dosage forms.     

Liposome-mediated gene delivery into plant cells

Liposomes may offer several advantages as vectors for gene delivery into plant cells: (1) enhanced delivery of encapsulated DNA by membrane fusion, (2) protection of nucleic acids from nuclease activity, (3) targeting to specific cells, (4) delivery into a variety of cell types besides protoplasts by entry through plasmodesmata, (5) delivery of intact small organelles. Realization of these advantages calls for the construction of efficient liposomes, for appropriate fusion conditions and for an understanding of the nature of liposome-cell interactions. Various characteristics and techniques of the liposome-cell system are described (mode of delivery, liposome types and composition, and means of promoting delivery of liposome contents). Data of liposome-mediated delivery of various macromolecules into plant cells, with special reference to protoplasts, calli and pollen are reviewed. This includes data obtained by the use of fluorescent probes, radioactive-labelled DNA, viral nucleic acids and expression of plasmid-DNA. Structure and characteristics of plant surfaces and plasmodesmata are discussed with respect to DNA entry. It is suggested that liposome-mediated gene delivery into plant cells, and not only protoplasts, will be advantageous in certain specific tissues and situations.     

A Liposomal Drug Platform Overrides Peptide Ligand Targeting to a Cancer Biomarker,Irrespective of Ligand Affinity or Density

One method for improving cancer treatment is the use of nanoparticle drugs functionalized with targeting ligands that recognize receptors expressed selectively by tumor cells. In theory such targeting ligands should specifically deliver the nanoparticle drug to the tumor, increasing drug concentration in the tumor and delivering the drug to its site of action within the tumor tissue. However, the leaky vasculature of tumors combined with a poor lymphatic system allows the passive accumulation, and subsequent retention, of nanosized materials in tumors. Furthermore, a large nanoparticle size may impede tumor penetration. As such, the role of active targeting in nanoparticle delivery is controversial, and it is difficult to predict how a targeted nanoparticle drug will behave in vivo. Here we report in vivo studies for α_vβ₆-specific H2009.1 peptide targeted liposomal doxorubicin, which increased liposomal delivery and toxicity to lung cancer cells in vitro. We systematically varied ligand affinity, ligand density, ligand stability, liposome dosage, and tumor models to assess the role of active targeting of liposomes to α_vβ₆. In direct contrast to the in vitro results, we demonstrate no difference in in vivo targeting or efficacy for H2009.1 tetrameric peptide liposomal doxorubicin, compared to control peptide and no peptide liposomes. Examining liposome accumulation and distribution within the tumor demonstrates that the liposome, and not the H2009.1 peptide, drives tumor accumulation, and that both targeted H2009.1 and untargeted liposomes remain in perivascular regions, with little tumor penetration. Thus H2009.1 targeted liposomes fail to improve drug efficacy because the liposome drug platform prevents the H2009.1 peptide from both actively targeting the tumor and binding to tumor cells throughout the tumor tissue. Therefore, using a high affinity and high specificity ligand targeting an over-expressed tumor biomarker does not guarantee enhanced efficacy of a liposomal drug. These results highlight the complexity of in vivo targeting.     

肝细胞靶向pH敏脂质体的制备及性质分析

为了制备具有肝细胞特异靶向性和pH敏感性的脂质体,设计并合成了四种带有半乳糖残基的导向分子,与具有pH敏感性的DC-chol/DOPE混合制备脂质体,通过质粒转染实验、受体竞争抑制实验和红细胞溶血等实验选出最佳转染活性的十八醇-半乳糖甙(18-gal)脂质体,并证明其具有肝细胞特异受体介导的靶向性和pH敏感性,且细胞毒性较小,可以作为一种潜在的肝细胞靶向转运系统得到进一步发展.     

Assessment of liposome delivery using scintigraphic imaging

Scintigraphic imaging is a valuable tool for the development of liposome-based therapeutic agents. It provides the ability to non-invasively track and quantitate the distribution of liposomes in the body. Liposomes labeled with technetium-99 m (99mTc) are particularly advantageous for imaging studies because of their favorable physical characteristics. Examples of how scintigraphic imaging studies have contributed to the evaluation and development of a variety of liposome formulations will be presented. These include liposomes for targeting processes with inflammation associated increased vascular permeability such as healing bone fractures and viral infections; liposomes for intraarticular delivery; and liposomes for delivery of agents to lymph nodes located in the extremities, the mediastinum and the peritoneum. Scintigraphic studies of liposome distribution are very informational and often suggest new drug delivery applications for liposomes.     

"Smart" drug carriers: PEGylated TATp-modified pH-sensitive liposomes

To engineer drug carriers capable of spontaneous accumulation in tumors and ischemic areas via the enhanced permeability and retention (EPR) effect and further penetration and drug delivery inside tumor or ischemic cells via the action of the cell-penetrating peptide (CPP), we have prepared liposomes simultaneously bearing on their surface CPP (TAT peptide, TATp) moieties and protective PEG chains. PEG chains were incorporated into the liposome membrane via the PEG-attached phosphatidylethanolamine (PE) residue with PEG and PE being conjugated with the lowered pH-degradable hydrazone bond (PEG-HZ-PE). Under normal conditions, liposome-grafted PEG "shielded" liposome-attached TATp moieties since the PEG spacer for TATp attachment (PEG(1000)) was shorter than protective PEG(2000). PEGylated liposomes are expected to accumulate in targets via the EPR effect, but inside the "acidified" tumor or ischemic tissues lose their PEG coating due to the lowered pH-induced hydrolysis of HZ and penetrate inside cells via the now-exposed TATp moieties. This concept is shown here to work in cell cultures in vitro as well as in ischemic cardiac tissues in the Langendorff perfused rat heart model and in tumors in experimental mice in vivo.