Photoresponsive Liquid‐Crystalline Dendrimers Based on a Cyclotriphosphazene Core

A series of new liquid‐crystalline dendrimers is synthesized from hexa(4‐hydroxyphenyloxy)­cyclotriphosphazene as the central core and bis(MPA) as a branching agent. The dendrimers are functionalized with azobenzene mesogenic moieties. The monodisperse nature of the dendrimers is confirmed by ¹H and ³¹P{¹H} NMR and by matrix assisted laser desorption/ionization (MALDI) mass spectrometry (MS). A study of the thermal properties reveals mesomorphic behavior. All of the materials exhibit a lamellar phase and this is confirmed to be smectic A in nature by X‐ray diffraction. A nematic phase is also observed for the dendrimers that contain 4‐cyanoazobenzene. A calamitic arrangement in which the mesogenic moieties point both upwards and downwards with respect to the cyclotriphosphazene core is proposed to explain the mesomorphic properties. The introduction of photochromic moieties leads to a photoresponse for these materials. The response to linearly polarized light is studied and an order parameter of about 0.5 is measured for dendrimer G1‐Azo‐3 .

     

Pseudoexon exclusion by antisense therapy in methylmalonic aciduria (MMAuria)

Development of pseudoexon exclusion therapies by antisense modification of pre-mRNA splicing represents a type of personalized genetic medicine. Here we present the cellular antisense therapy and the cell-based splicing assays to investigate the effect of two novel deep intronic changes c.1957–898A>G and c.1957–920C>A identified in the methylmalonyl–coenzyme A (CoA) mutase (MUT) gene. The results show that the nucleotide change c.1957–898A>G is a pathological mutation activating pseudoexon insertion and that antisense morpholino oligonucleotide (AMO) treatment in patient fibroblasts leads to recovery of MUT activity to levels 25 to 100% of control range. On the contrary, the change c.1957–920C>A, identified in two fibroblasts cell lines in cis with c.1885A>G (p.R629G) or c.458T>A (p.D153V), appears to be a rare variant of uncertain clinical significance. The functional analysis of c.1885A>G and c.458T>A indicate that they are the disease-causing mutations in these two patients. The results presented here highlight the necessity of scanning the described intronic region for mutations in MUT-affected patients, followed by functional analyses to demonstrate the pathogenicity of the identified changes, and extend previous work of the applicability of the antisense approach in methylmalonic aciduria (MMAuria) for a novel intronic mutation. Hum Mutat 30:1–7, 2009. © 2009 Wiley-Liss, Inc.     

Cationic nanoparticles for cancer therapy

Importance of the field: The lack of selective delivery of therapeutic molecules to cancer cells remains a problem in cancer therapy. As a result of this non-selectivity, cytotoxic agents are delivered to both healthy and cancerous cells, resulting in severe side effects for the patient, eventually causing termination of therapy or ineffective therapy resulting in progression or recurrence of the disease. In this context, cationic polymers with net positive surface charge emerge as a promising option owing to their very strong cellular interaction properties and good cellular uptake.

Areas covered in this review: In this review, the structure, characteristics and preparation techniques for cationic nanoparticulate drug delivery systems are discussed in the light of cytotoxicity associated with cationic polymers and strong complement activation properties of cationic carrier systems on injection. In vivo behavior and biodistribution of cationic nanoparticles are also reviewed for a better understanding of biological interaction of cationic nanoparticles.

What the reader will gain: This review will give an insight to the properties of cationic polymers, including their advantages and drawbacks and drug/gene delivery systems based on cationic polymers intended for cancer therapy.

Take home message: Cationic polymer-based nanoparticles emerge as a promising group of nanosize carrier systems to the tumor cell level with a wide range of modification and application possibilities.     

Exploiting Herpes Simplex Virus Entry for Novel Therapeutics

Herpes Simplex virus (HSV) is associated with a variety of diseases such as genital herpes and numerous ocular diseases. At the global level, high prevalence of individuals who are seropositive for HSV, combined with its inconspicuous infection, remains a cause for major concern. At the molecular level, HSV entry into a host cell involves multiple steps, primarily the interaction of viral glycoproteins with various cell surface receptors, many of which have alternate substitutes. The molecular complexity of the virus to enter a cell is also enhanced by the existence of different modes of viral entry. The availability of many entry receptors, along with a variety of entry mechanisms, has resulted in a virus that is capable of infecting virtually all cell types. While HSV uses a wide repertoire of viral and host factors in establishing infection, current therapeutics aimed against the virus are not as diversified. In this particular review, we will focus on the initial entry of the virus into the cell, while highlighting potential novel therapeutics that can control this process. Virus entry is a decisive step and effective therapeutics can translate to less virus replication, reduced cell death, and detrimental symptoms.     

新型基因载体-聚酰胺-胺树状大分子聚合物

利用重组DNA技术进行疾病预防和治疗是近几年来的研究热点,如何提高重组DNA的转染效率一直是研究的难题之一,新型阳离子多聚物--聚酰胺-胺型树状大分子(Starburst PAMAM dendrimers,PAMAM-D)的出现为解决现存的难题带来希望.PAMAM-D最早由美国人Tomalia于1985年合成,目前已广泛应用于各个领域:药物载体、废水处理、催化剂、光电传感、基因载体等.由于PAMAM-D具有对称的刚性球体结构,表面带有大量正电荷,容易与带负电荷的核酸形成复合物,故作为基因载体具有许多优于其他现有转染试剂的优良特性.本文主要介绍了PAMAM-D的结构、性质、应用以及作为基因载体的优越性,并对今后的研究方向进行了概述.     

Design of clinically useful macromolecular iron chelators

Objectives In recent years, macromolecular iron chelators have received increasing attention as human therapeutic agents. The objectives of this article are: one, to discuss the factors which should be considered when designing iron binding macromolecules as human therapeutic agents, and two, to report recent achievements in the design and synthesis of appropriate macromolecular chelators that have resulted in the production of a number of agents with therapeutic potential. Key findings Macromolecular drugs exhibit unique pharmaceutical properties that are fundamentally different from their traditional small‐molecule counterparts. By virtue of their high‐molecular‐weight characteristics, many are confined to extracellular compartments, for instance, the serum and the gastrointestinal tract. In addition, they have potential for topical administration. Consequently, these macromolecular drugs are free from many of the toxic effects that are associated with their low‐molecular‐weight analogues. Summary The design and synthesis of macromolecular iron chelators provides a novel aspect to chelation therapy. 3‐Hydroxypyridin‐4‐one hexadentate‐based macromolecular chelators have considerable potential for the development of new treatments for iron overload and for topical treatment of infection.     

乙二胺为核心的PAMAM树枝状聚合物(5.0代)纳米材料溶液的遗传毒性研究

目的:研究乙二胺为核心的PAMAM树枝状聚合物(5.0代)纳米材料溶液的遗传毒性。方法:采用Ames试验平板掺入法,设3 985、797、139.4、31.88和6.376 μg/皿的5个乙二胺为核心的PAMAM树枝状聚合物(5.0代)溶液浓度组,在加与不加S9混合液的条件下观察回变菌落数。同时采用L5178Y细胞胞质分裂阻滞微核细胞组学试验,给予受试细胞终浓度分别为0.625、1.25、2.5、5、10 μg/mL的受试物,观察其微核组效应、剂量-效应和时间-效应关系。结果:受试物溶液各剂量组均未引起测试菌株回变菌落数明显增加,Ames试验结果为阴性。胞质分裂阻滞微核细胞组学试验中,与阴性对照组比较,1.25 μg/mL的受试物即可诱导受试细胞出现核芽(P<0.01);2.5 μg/mL及以上剂量可进一步诱使细胞出现总微核、Ⅰ型微核、Ⅱ型微核和核质桥效应(P<0.01),且存在明显的剂量-效应关系(除核质桥外,r值均>0.5,P均<0.05)。与阴性对照组比较,在5 μg/mL剂量下,乙二胺为核心的PAMAM树枝状聚合物(5.0代)溶液在9 h时即可诱导受试细胞的总微核、Ⅰ型微核、Ⅱ型微核和核芽增加(P<0.01);在18 h时出现核质桥数增加(P<0.01),各项指标在27 h达到峰值。结论:乙二胺为核心的PAMAM树枝状聚合物(5.0代)溶液对鼠伤寒沙门氏菌无致基因突变作用;对L5178Y细胞可诱导4类微核组效应,并有明显的剂量-效应和时间-效应关系;从剂量和时间来看,以核芽效应最为敏感。     

聚酰胺-胺PAMAM树状聚合物对灯盏花素的溶解性及其药代动力学的影响

测定聚酰胺-胺PAMAM树状聚合物对灯盏花素的增溶性能并探讨其增溶机制; 研究PAMAM树状聚合物对灯盏花素体内药代动力学的影响。测定和比较了G1、G1.5、G2、G2.5代PAMAM在不同浓度和不同pH时对灯盏花素的增溶量; 另将12只大鼠随机均分为2组, 每组6只, 分别以灯盏花素及灯盏花素-PAMAM灌胃, 采用反相高效液相色谱法检测血浆药物浓度。在pH小于7.0时, PAMAM树状聚合物对灯盏花素的增溶量随着PAMAM代数、浓度和溶液pH的增加而增大, 其增溶机制为灯盏花素的羧基与PAMAM的伯胺和叔胺发生静  电作用; 灯盏花素、灯盏花素-PAMAM口服给药的C_max分别为 (119.65 ± 9.36) 和 (518.17 ± 17.07) ng·mL^-1, AUC_{0-8 h}分别为 (370.09 ± 63.08) 和 (1 219.47 ± 201.87) ng·h·mL^-1, 两者具有极显著性差异 (P < 0.01)。说明PAMAM能显著提高灯盏花素在水中的溶解度; 大大改善灯盏花素口服给药的生物利用度。     

聚酰胺-胺树状大分子及其PEG修饰物的合成、表征与载药性能

目的合成并表征各代聚酰胺-胺(polyamide-amine,PAMAM)树状大分子及聚乙二醇(poly-ethylene glycol,PEG)修饰PAMAM,研究其对难溶性药物的包载及释放行为。方法用发散法合成1-5代PAMAM大分子及PEG化PAMAM,采用IR、NMR、端基滴定、GPC等方法对其进行表征,并以阿霉素为模型药物,比较PAMAM和PEG-PAMAM载药能力及释放效果。结果FTIR、NMR、端基滴定、GPC测定结果表明所合成的产物确为1-5代PAMAM树状大分子,IR测定结果表征PEG化PAMAM合成,PAMAM大分子及PEG-PAMAM对难溶性药物具有较强包载能力,其中PEG-PAMAM能够更好地延缓药物释放。结论PEG-PAMAM大分子具有良好的作为难溶性药物载体的潜力。     

Mechanistic studies of in vitro cytotoxicity of poly(amidoamine) dendrimers in mammalian cells

Poly(amidoamine) (PAMAM) dendrimer nanoparticles have been demonstrated to elicit a well defined cytotoxicological response from mammalian cell lines, the response increasing systematically with dendrimer generation and number of surface amino groups. In this work, using generation G4, G5, and G6 dendrimers, this systematic response is furthermore demonstrated for the generation of reactive oxygen species, lysosomal activity, and the onset of apoptosis and levels of DNA damage. The results are consistent with a pathway of localisation of PAMAM dendrimers in the mitochondria leading to ROS production causing oxidative stress, apoptosis and DNA damage. ROS production is co-located in the mitochondria, and both generated levels and timescales are systematically generation dependent (G4 < G5 < G6). Flow cytometry confirms that with increasing dose, the percentage of healthy and early apoptotic cells decreases, whereas the late apoptotic and necrotic cell populations increase. This process is again systematically generation dependent. DNA damage as measured using the TUNEL assay further demonstrates a systematic trend, G4, G5 and G6 showing 4.69%, 25.87% and 89.63% DNA breakage respectively. Increases in lysosomal activity at timescales of ~ 24 h are observed in HaCaT but not SW480 cells upon low concentration PAMAM exposure. Overall, significant differences are observed between the responses of the dermal cell line, HaCaT, and the colon cell line, SW480, and it is suggested that these can be understood in terms of differing intrinsic antioxidant levels.