聚多巴胺表面修饰毛细管电色谱的研究进展

毛细管电泳（CE）具有分离时间短、分离效率高、样品消耗量低等优点,在分离分析领域有着重要应用。原始的未修饰熔融石英毛细管只能提供阴极流向的电渗流和单一的电泳分离机制,分离性能有限,重复性较差,不能满足各类复杂样品体系尤其是中性和手性样品的分离需求。因此,有必要在CE中引入各类毛细管修饰策略,以拓展其实际应用潜力。贻贝仿生聚多巴胺（PDA）及其衍生材料因其简便易行的制备过程、优异的表面黏附性、良好的生物相容性、较强的二次反应活性和化学稳定性等优点,在催化、传感、水处理、样品前处理、生物医药以及CE分离等领域得到了广泛应用。PDA涂层的制备过程与物理吸附涂层一样简便,而表面黏附涂层的稳定性又可与共价键合涂层相媲美,因此非常适用于石英毛细管柱的修饰。更重要的是,PDA涂层较强的二次反应活性使其可作为反应平台进行灵活多样的二次表面修饰,便于构建多功能PDA涂层毛细管电色谱（CEC）固定相。基于这些突出优点,PDA涂层材料在CEC中的巨大应用价值逐渐得到了研究者们的广泛关注。该文首先对近3年有关PDA形成机理及PDA快速沉积表面化学的最新研究进展进行了总结,在此基础上综述了近10年PDA涂层材料在开管毛细管电色谱（OT-CEC）和毛细管电色谱整体柱中的最新应用。此外,还对PDA涂层材料在CEC中的发展方向进行了展望。     

聚多巴胺在强负电型微球表面的形貌调控

多巴胺(DA)已被证实可在多种材料的表面进行氧化自聚而形成聚多巴胺(PDA),但其在带强负电荷的表面上的聚合机理和所形成的形貌却还不太明确。 为考察材料表面的电负性、氧化条件等对DA氧化自聚速度和聚多巴胺层形貌的影响,本文通过无皂乳液聚合制备了以聚苯乙烯(PS)为核、聚丙烯酸(PAA)为壳的纳米粒子(PS/PAA NPs),探究其表面的阴离子在不同pH缓冲液、反应时间下与DA的加入量对聚合过程及其形貌的影响。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和Zeta电势对所得纳米粒子的结构、形貌与尺寸等进行分析。 结果发现,在pH值为8.5的三羟甲基氨基甲烷(Tris)缓冲溶液中,当DA与PS/PAA NPs的质量比为1∶1时,在反应24 h后,PDA以纳米颗粒的形式存在于PS/PAA NPs的表面,即所形成的PS/PAA/PDA NPs为明显的树莓状结构。 随着DA含量的增加和反应时间的延长,所形成的树莓状粒子粒径增大;当DA远远过量时,PDA最终在微球表面形成致密、均匀的壳层。 Zeta电势结果表明树莓状结构是由于DA在PAA表面聚合过程中受到静电相互作用和电荷排斥作用间的竞争而形成的,随着DA量的增大和反应时间的延长,形成的静电作用增大,使较多的PDA粘附至PAA表面而形成较致密的均匀壳层。 同时,DA在电负性较小的PS/SDS微球和非离子的PS微球表面聚合时,均形成致密的PDA壳层。 因而,材料表面的电负性大小可以调控DA在其表面的沉积,以制备不同形貌的PDA复合材料。     

Development of Stimulus‐Responsive Degradable Film via Codeposition of Dopamine and Cystamine

Herein, we report a degradable film that can be coated on various substrates by the codeposition of dopamine and cystamine. The thickness of the resulting film (pDC) varies depending on the initial ratio of dopamine/cystamine dissolved in a solution; the thickest film (ca. 60 nm) is obtained under optimized codeposition conditions. Selective degradation of pDC occurs in the presence of tris(2‐carboxyethyl)phosphine (TCEP), the reaction kinetics of which are highly dependent on the TCEP concentration. For further application as a drug‐delivery platform, doxorubicin can be loaded within the pDC film, which is released actively under film degradation in response to TCEP. We expect that the developed pDC film will be a useful tool for developing drug delivery cargo, antibacterial surface, and cell surface coating for various biomedical applications.     

Polydopamine—An Organocatalyst Rather than an Innocent Polymer

Polydopamine (PDA) is easily available by oxidation of dopamine and is widely used for persistent coatings of various materials. It is hitherto considered to be inert in many interesting biomedical and other applications. Results presented here, reveal an unexpected behavior of polydopamine as an organocatalyst in direct aldol reactions under mild conditions. Evidence was found for dual catalysis making use of amino and phenolic hydroxy groups found in PDA. Thus scientists must be aware that PDA is not an innocent polymer and can cause unwanted side effects in important applications, such as in biomedicine or as supports in catalysis.     

Tuning the low critical solution temperature of polymer brushes grafted on single‐walled carbon nanotubes and temperature dependent loading and release properties

A nondestructive method was developed for grafting and retrieving polymer brushes from single‐walled carbon nanotubes (SWCNT)s based on mussel‐inspired chemistry. Thermo‐responsive polymer brushes were grafted on SWCNTs by coating the tubes with polydopamine as a reactive underlayer and sequential surface‐initiated atom transfer radical polymerization of oligo(ethylene glycol) methacrylate (OEGMA, M_n = 475) and 2‐(2'‐methoxyethoxy)ethyl methacrylate (MEO2MA). Copolymer brushes were retrieved from the SWCNTs using 1 M NaOH to destroy the crosslinked polydopamine coating, and after that, the pristine properties of the SWCNTs were preserved. The low critical solution temperature (LCST) and molecular weight of the copolymer were measured using a nephelometer and gel permeation chromatograph, respectively. The loading and release behavior of Rhodamine 6G on responsive polymer‐grafted SWCNTs demonstrates that the copolymer brushes confer the SWCNTs an LCST dependence. This method can accurately confirm the molecular weights and polydispersity of stimuli‐responsive polymers grafted on any other nanoparticles and predict their controlled release behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1807–1814     

Antibacterial and biocompatible surfaces based on dopamine autooxidized silver nanoparticles

A facile and green method is proposed to immobilize silver nanoparticles (AgNPs) showing antibacterial and biocompatible properties on surfaces of substrates. The adhesive and reductive polydopamine (Pdop) coating was applied on the substrates such as polyethylene, glass, poly(methyl methacrylate), and poly(lactic-co-glycolic acid) by simply dipping into dopamine solutions. AgNPs of 50–70 nm formed uniformly on the Pdop-coated surfaces after immersing in silver nitrate solution where the density of AgNPs was modulated by Pdop immobilization time. Antibacterial efficacy, lactate dehydrogenase assay, and cell morphology observed by microscopy indicated that the as-prepared AgNPs deposited on Pdop/substrates possessed effective biocidal properties and did not inhibit the growth of L-929 cells mouse fibroblasts. The proposed method can be easily applied on different substrates and revealed good biocompatibility, which could be further developed for applications in biomaterials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Inverted Quasi‐Spherical Droplets on Polydopamine–TiO2 Substrates for Enhancing Gene Delivery

Devising efficient gene delivery systems is crucial to enhancing the therapeutic efficacy of gene–cell therapy approaches. Herein, inverted quasi‐spherical (iQS) droplet systems, which enhance gene delivery efficiencies by reducing the path lengths of gene vectors, mediating motions of vectors at early stages, and raising the contact frequencies of vectors with cells, are developed by adopting the principle of 3D hanging‐drop cell culture. Micrometer‐sized polydopamine (pDA) holes are created on superhydrophobic titanium isopropoxide (TiO₂)‐coated substrates by physical scraping; droplets are loaded on the pDA holes, and inversion of the substrate generates iQS droplets with large contact angles. Both human neural stem cells (hNSCs) and adeno‐associated viral vectors are simultaneously incorporated into the iQS droplets to assess gene delivery efficiencies. The steep angles of iQS droplets and enhanced cell/vector contact frequencies facilitate the viral association with hNSCs and enhancing cell–cell interactions, thereby significantly promoting gene delivery efficiencies. Even with reduced viral quantities/exposure times and cell numbers, the iQS droplet systems elicit sufficient gene expression (i.e., interleukin‐10). The ability of the iQS droplet systems to maximize beneficial gene delivery effects with minimal materials (e.g., medium, cells, and vectors) should enable their extensive use as a platform for preparing genetically stimulated cellular therapeutics.     

The Chemistry behind Catechol‐Based Adhesion

The adhesion of some marine organisms to almost any kind of surface in wet conditions has aroused increasing interest in recent decades. Numerous fundamental studies have been performed to understand the scientific basis of this behaviour, with catechols having been found to play a key role. Several novel bio‐inspired adhesives and coatings with value‐added performances have been developed by taking advantage of the knowledge gained from these studies. To date there has been no detailed overview focusing exclusively on the complex mode of action of these materials. The aim of this Review is to present recent investigations that elucidate the origin of the strong and versatile adsorption capacities of the catechol moiety and the effects of extrinsic factors that play important roles in the overall adhesion process, such as pH value, solvent, and the presence of metal ions. The aim is to detail the chemistry behind the astonishing properties of natural and synthetic catechol‐based adhesive materials.     

Applications of polydopamine modifications in capillary electrophoretic analysis

Mussel‐inspired polydopamine has been widely used in capillary electrophoresis as a facile and universal tool for the surface modification of capillary, mainly due to its versatility, stability, strong adhesiveness, and biocompatibility properties. In this review, the recent development of mussel‐inspired surface chemistry with rapid deposition of polydopamine was introduced, and the recent applications of polydopamine in capillary electrophoresis (2011–July 2018) were summarized into four main aspects, namely, sample pretreatments, functional coatings, codeposition coatings, and intermediate coatings. Further study may be focused on clarifying the mechanisms of polydopamine formation and polydopamine‐assisted codeposition, and expanding coatings methods to plant polyphenols.     

超顺磁Fe_3O_4@PDA核-壳结构纳米粒子的制备及表征

利用多元醇高温热解法和溶液氧化法制备超顺磁四氧化三铁聚多巴胺核-壳结构纳米粒子(Fe_3O_4@PDA)。采用X射线衍射(XRD)、透射电子显微镜(TEM)、动态光散射(DLS)、傅里叶转换红外光谱(FT-IR)和热重分析(TG)等对Fe_3O_4@PDA的结构、形貌和组成进行表征。采用综合物性测试系统(PPMS)对样品的磁性能进行表征。结果表明:Fe_3O_4@PDA的尺寸可以通过氨水与多巴胺的物质的量之比和反应时间进行调控;当Fe_3O_4@PDA中Fe_3O_4的质量分数约为5%时,具有超顺磁性,磁饱和强度为3.8emu/g,比理论值高出36%。