树状多肽的合成及应用

树状多肽作为树枝状大分子的一种,具有不同于链状多肽的独特理化特性,在生物学领域中具有广泛的应用.本文简要综述了树状多肽的合成方法,及其在诱导免疫反应、生物分子模拟、免疫诊断试剂、人工酶、药物及基因载体等方面的应用.     

多肽分子自组装

源于自然界中广泛存在的蛋白质自组装现象,近年来多肽的自组装逐渐成为材料学和生物医学等领域的研究热点.通过合理调控多肽的分子结构以及改变外界的环境,多肽分子可以利用氢键、疏水性作用、π-π堆积作用等非共价键力自发或触发地自组装形成形态与结构特异的组装体.由于多肽自身具有良好的生物相容性和可控的降解性能,利用多肽自组装技术构建的各种功能性材料在药物控制释放、组织工程支架材料以及生物矿化等领域内有着巨大的应用前景.本文总结了近年来多肽自组装研究的进展,介绍了多肽自组装技术常见的几种结构模型,概括了多肽自组装的机理,并进一步阐述多肽自组装形成的组装体形态及其在材料学和生物医学等领域里的应用.     

多肽纳米管

环状多肽是构成多肽纳米管的主要子结构,它的结构形式和骨架分子构象直接影响多肽纳米管的特性。作为有特殊电子和光学性质的多肽纳米管,它在化学、生物、材料和医学等方面有潜在的应用。本文就自组装多肽纳米管的结构和应用作了介绍。     

多肽及蛋白质的化学合成研究

多肽与蛋白质作为生物体内的活性物质和生命活动的物质基础,在信号传递、能量利用、免疫应答等基础生理过程发挥着至关重要的作用,并与多种疾病的发生密切相关。获得一定数量高纯度的多肽和蛋白质是研究其结构、生物学功能以及开发相关药物的重要前提。天然多肽与蛋白质的来源主要有动植物的组织器官、微生物的次级代谢产物等。目前,自然提取、重组技术和化学合成是多肽与蛋白质的主要获得途径。相较于从天然产物中提取分离和基因重组表达,化学合成能够方便地在多肽与蛋白质的任意位点引入非天然氨基酸或特定类型的翻译后修饰基团,如糖基化、磷酸化、荧光团及光交联反应基团等,极大地促进了多肽与蛋白质在基础医学及生物医药研究领域的应用发展。本综述全面介绍了多肽与蛋白质的各种化学合成研究策略,并讨论了这些策略的基本原理、优缺点及应用价值,旨在为多肽及蛋白质的合成研究提供参考。     

多肽自组装技术及其在生物医学上的应用

多肽分子自组装广泛存在于自然界中。多肽具有良好的生物相容性和可调控的降解性能,并且利用多肽自组装技术,可以在分子水平上设计并调控聚集态的形状和结构,这在生物医学材料方面具有巨大的应用潜力。近年来关于多肽自组装的研究成为材料学、医学等领域中研究热点之一,并且在药物缓释载体、组织工程支架研究方面取得进展。本文介绍多肽分子自组装技术的概念,综述了多肽自组装技术在药物缓释载体材料、组织工程支架材料方面的应用。     

功能多肽在肿瘤治疗中的应用及研究进展

多肽具有生物相容性好,功能多样化,生物体内响应性高及合成修饰方法简单易行等优点,已被广泛用于构建靶向药物传递系统。以具有靶向功能和刺激响应性的多肽为基础构建的药物传递系统,能够将药物定向地运送到肿瘤区域。药物传递系统到达肿瘤组织后,在肿瘤组织特殊微环境或外源刺激下,实现药物的精准释放。这种具有特异性肿瘤靶向和刺激响应型的多肽载体可以最大程度地提高药物的抗肿瘤效果,降低药物的毒副作用。本文简要介绍了常用的靶向多肽和刺激响应型多肽,并讨论了基于功能型多肽的药物载体在肿瘤治疗方面的应用。     

多肽酰肼法合成Nesiritide

Nesiritide是一类重要的多肽类血管扩张药物,在维持心血管和肾脏的体内平衡方面发挥着重要的作用.目前,Nesiritide的合成主要是通过基因重组表达法获得,该方法操作较为复杂且存在一定的限制.本研究运用多肽固相合成及酰肼连接策略,通过3片段连接高效合成了Nesiritide,为大批量工业化生产该类多肽药物打下基础.     

环境响应性多肽自组装研究进展

分子自组装广泛存在于自然界中,参与生物体的各项生命活动,从而确保生物体相关生理功能的实现和生化反应的有序进行.多肽自组装作为分子自组装的重要组成部分,其良好的生物相容性为构建具有重要应用价值的生物医用材料提供了新的思路.本文总结了多肽自组装过程中主要的驱动作用力;简述了多肽自组装形成的主要结构;详细介绍了自组装过程中环境变化,包括pH、温度、离子强度、特殊离子、氧化还原态以及光照等,对于环境响应性多肽自组装结构和性质的影响;并且阐述了多肽自组装生物材料的应用方向和前景,希望为该领域的进一步研究提供参考.     

基于多肽识别的电化学生物传感技术

多肽具有分子量小、易于合成、生物兼容性好、稳定性高及序列灵活多样等优点。因此,多肽作为新型生物识别元件,已被广泛应用于生物传感器的构建。电化学分析灵敏度高、准确度好、设备简单、检测范围广且易于操作。本文介绍了基于多肽识别的电化学生物传感器技术,包括多肽的修饰与固定化、多肽与待测物的识别及检测原理;综述了近五年多肽电化学生物传感器对重金属离子、小分子、蛋白质、细菌和病毒的检测;展望了肽基电化学生物传感器的发展趋势。     

基于多肽的纳米药物递送系统的研究

构建纳米药物递送系统改善药物的理化性质和生物学性质已经成为现代药物设计研究的热点和重要方向。其中,多肽作为新兴的纳米药物的构筑基元具有良好生物相容性、自组装性与化学可变性等性质,激起了广泛的研究兴趣,为构建新型纳米递送系统提供了崭新的研究方向。本文阐述了自组装多肽在疏水作用、氢键、静电作用、π-π堆积等非共价作用力的综合作用下构建胶束、囊泡、球、纤维等不同形貌的纳米材料;进一步介绍了多肽药物结合物的基本概念以及高载药量、高生物利用度的优势,总结了近年来基于功能性多肽构建纳米药物递送系统的研究;重点介绍了近五年来报道的具有自组装性、增强溶解性、长效性、靶向性、刺激响应性、细胞跨膜性等多种功能的智能多肽纳米药物递送系统。     

Effective Drug Therapies from Functional,Macromolecular Building Blocks with a Biomimetic Design

Summary: The development of suitable delivery systems for intracellular delivery of proteins, peptides and other bioactive materials opens the possibility to establish refined strategies for small drug delivery, gene delivery and vaccination. We present the assembly of advanced drug delivery systems from tailored building blocks to scaffolds and bioactive cargos to afford targeting and transport across biological barriers. In particular, the utilization of novel molecular transporter will advance the bioavailability of small and macromolecular drugs that show targeted intracellular delivery.     

Effects of acidic catalysts on the microstructure and biological property of sol–gel bioactive glass microspheres

Sol–gel bioactive glasses have been developed for bone tissue regeneration and drug delivery systems as they have the unique mesoporous structure and high bioactivity in vitro. To develop more reliable drug delivery and bone tissue repair systems, it is necessary to control the morphology and microstructure of bioactive glasses. For this purpose, bioactive glass microspheres (BGMs) were prepared by a sol–gel co-template technology using acids as catalysts. We studied the effects of different acids (citric acid, lactic acid and acetic acid) on the microstructure and apatite-forming bioactivity of BGM. The apatite-forming bioactivity was carried out in simulated body fluid (SBF). The microstructure and apatite-forming bioactivity of BGMs were characterized by various methods. Results showed that acetic acid had little effect on the structure and bioactivity of BGMs. Differently, the morphology and microstructure of BGMs could be controlled by changing citric acid and lactic acid concentrations. In vitro bioactivity test indicated that citric acid and lactic acid derived BGMs possessed the better apatite-forming capacity than that derived by acetic acid.     

Tunable growth factor delivery from injectable hydrogels for tissue engineering

Current sustained delivery strategies of protein therapeutics are limited by the fragility of the protein, resulting in minimal quantities of bioactive protein delivered. In order to achieve prolonged release of bioactive protein, an affinity-based approach was designed which exploits the specific binding of the Src homology 3 (SH3) domain with short proline-rich peptides. Specifically, methyl cellulose was modified with SH3-binding peptides (MC-peptide) with either a weak affinity or strong affinity for SH3. The release profile of SH3-rhFGF2 fusion protein from hyaluronan MC-SH3 peptide (HAMC-peptide) hydrogels was investigated and compared to unmodified controls. SH3-rhFGF2 release from HAMC-peptide was extended to 10 days using peptides with different binding affinities compared to the 48 h release from unmodified HAMC. This system is capable of delivering additional proteins with tunable rates of release, while maintaining bioactivity, and thus is broadly applicable.     

Integration of Mesoporous Bioactive Glass Nanoparticles and Curcumin into PHBV Microspheres as Biocompatible Composite for Drug Delivery Applications

Bioactive glasses (BGs) are being increasingly considered for biomedical applications. One convenient approach to utilize BGs in tissue engineering and drug delivery involves their combination with organic biomaterials in order to form composites with enhanced biocompatibility and biodegradability. In this work, mesoporous bioactive glass nanoparticles (MBGN) have been merged with polyhydroxyalkanoate microspheres with the purpose to develop drug carriers. The composite carriers (microspheres) were loaded with curcumin as a model drug. The toxicity and delivery rate of composite microspheres were tested in vitro, reaching a curcumin loading efficiency of over 90% and an improving of biocompatibility of different concentrations of MBGN due to its administrations through the composite. The composite microspheres were tested in terms of controlled release, biocompatibility and bioactivity. Our results demonstrate that the composite microspheres can be potentially used in biomedicine due to their dual effects: bioactivity (due to the presence of MBGN) and curcumin release capability.     

Nanovesicles based on self-assembly of conformationally constrained aromatic residue containing amphiphilic dipeptides

Peptide-based vesicular structures have been the focus of research in the past decade for their potential application as drug delivery agents. We here report the self-assembly of amphiphilic dipeptides containing conformation-constraining alpha,beta-dehydrophenylalanine into nanovesicles. The vesicles can encapsulate small drug molecules such as riboflavin and vitamin B(12), bioactive peptides, and small protein molecules. The nanovesicles are resistant to treatment of a nonspecific protease, proteinase K, and are stable at low concentrations of monovalent and divalent cations. The vesicles are effectively taken up by actively growing cells in culture and show no observable cytopathic effects. These peptide-based nanostructures can be considered as models for further development as delivery agents for different biomolecules.     

The concept of functional peptidomics for the discovery of bioactive peptides in cell culture models

Detection and purification of novel bioactive peptides from biological sources is a scientific task that led to a substantial number of important discoveries. One major laborious approach used is the repetitive stepwise separation of the test sample into several fractions followed by the determination of their bioactivity, until purity allows for sequence identification. We tested whether functional peptidomics, a combination of biological read-outs with differential peptide display (DPD) is a suitable strategy to isolate bioactive peptides at lower workload and with improved success. Additionally, we evaluated the use of DPD to monitor the processing status of proinsulin by inhibition of the insulin processing pathway. The rat insulinoma cell line INS-1 stimulated either with 2 mmol/l or 10 mmol/l glucose was used as model to generate differential peptide displays. In parallel, the bioactivity of the supernatants from the INS-1 cells was measured by glucose uptake and lipolysis assays using the adipocyte cell line 3T3-L1. We were able to quickly and elegantly trace the known activity of insulin to increase glucose uptake and inhibit lipolysis. Following re-chromatography of selected fractions, relevant peptides were identified by DPD and bioassays: the rat insulin-1 precursor and two different insulin peptides. We demonstrated in a semi-quantitative fashion that inhibition of proinsulin processing leads to accumulation of the insulin precursor, and reduced secretion of insulin-1. Thus, we conclude that DPD is an attractive support technology in peptide purification strategies aiming to identify bioactive compounds, and is superior to ELISA in discriminating between the processing status of insulin and its precursor.     

Synthesis and characterization of europium-containing luminescent bioactive glasses and evaluation of in vitro bioactivity and cytotoxicity

Luminescent europium-containing bioactive glasses (EuBG) based on the 58 %SiO₂–33 %CaO–9 %P₂O₅ (in mass, %) system were synthesized using sol–gel technique by adding Eu₂O₃ in silica network. The structural, textural and optical properties, as well as in vitro bioactivity and biocompatibility of the material were characterized using various methods. The results show that all the Eu-containing bioactive glass materials exhibit an amorphous structure, large specific surface area, relatively uniform pore size distribution and high in vitro bioactivity, similar to the conventional sol–gel bioactive glass. More importantly, the addition of Eu₂O₃ endow the material with a luminescent property even after immersion in aqueous solution and the luminescent intensity increases with the increase of Eu₂O₃ content. The cytotoxicity assay indicates that pure EuBG extract significantly inhibit the growth of rat marrow mesenchymal stem cells (rMSCs), while 25 % concentration of the extract diluted by culture medium could significantly improve the proliferation of rMSCs in comparison with pure medium. According to the above results, the material presents excellent apatite-forming activity, luminescent property and biocompatibility, demonstrating their potential applications in the fields of bone regeneration and drug delivery system.     

Encapsulation of proteinase K in PELA ultrafine fibers by emulsion electrospinning: preparation and in vitro evaluation

The aims of this study were to encapsulate water-soluble bioactive agents into biodegradable hydrophobic polymers via emulsion electrospinning for drug delivery and tissue engineering applications and propose a simple and facile method to evaluate the bioactivity of the encapsulated protein. Proteinase K was selected as a model protein to be incorporated into poly(ethylene glycol)-poly(l-lactide) (PELA) ultrafine fibers. Core–shell structured fibers with single core or multi-core were observed. In vitro release study showed that after a burst release at the early stage, a sustained release was achieved, indicating that proteinase K was incorporated inside ultrathin fibers successfully. Results of in vitro incubation in Tris–HCl buffer at pH?8.6 and 37?°C revealed that electrospun PELA membranes containing proteinase K (PELA-P) showed obvious morphological changes, large mass loss, and slight decreases in melting temperature, melting enthalpy and relative molecular mass in 7 days. Additionally, a significant drop in pH value of the buffer after incubation of the PELA-P membrane was also observed. These findings clearly showed that encapsulation of water-soluble bioactive agents inside hydrophobic polymers could be achieved by emulsion electrospinning without compromising their bioactivity.     

Nanofilm biomaterials: localized cross-linking to optimize mechanical rigidity and bioactivity

Nanofilm biomaterials, formed by the layer-by-layer assembly of charged macromolecules, are important systems for a variety of cell-contacting biomedical and biotechnological applications. Mechanical rigidity and bioactivity are two key film properties influencing the behavior of contacting cells. Increased rigidity tends to improve cells attachment, and films may be rendered bioactive through the incorporation of proteins, peptides, or drugs. A key challenge is to realize films that are simultaneously rigid and bioactive. Chemical cross-linking of the polymer framework--the standard means of increasing a film's rigidity--can diminish bioactivity through deactivation or isolation of embedded biomolecules or inhibition of film biodegradation. We present here a strategy to decouple mechanical rigidity and bioactivity, potentially enabling nanofilm biomaterials that are both mechanically rigid and bioactive. Our idea is to selectively cross-link the outer region of the film, resulting in a rigid outer skin to promote cell attachment, while leaving the film interior (with any embedded bioactive species) unaffected. We propose an approach whereby an N-hydroxysulfosuccinimide (sulfo-NHS) activated poly(L-glutamic acid) is added as the terminal layer of a multilayer film and forms (covalent) amide bonds with amino groups of poly(L-lysine) placed previously within the film. We characterize film assembly and cross-linking extent via quartz crystal microbalance with dissipation monitoring (QCMD), Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), and laser scanning confocal microscopy (LSCM) and measure the attachment and metabolic activity of preosteoblastic MC3T3-E1 cells. We show cross-linking to occur primarily at the film surface and the subsequent cell attachment and metabolic activity to be enhanced compared to native films. Our method appears promising as a means to realize films that are simultaneously mechanically rigid and bioactive.