原位凝聚法制备聚电解质微胶囊——模板中掺杂聚电解质量对微胶囊结构与性能的影响

通过在CaCO3制备过程中加入不同浓度聚苯乙烯磺酸钠(PSS)的方法来控制掺杂进CaCO3粒子中的PSS含量,得到了PSS掺杂量为4%～11%,尺寸均匀的CaCO3球形微粒.在微粒表面仅吸附一层聚烯丙基胺盐酸盐(PAH)后,用乙二胺四乙酸二钠(EDTA)使碳酸钙溶解;释放出的PSS与PAH原位凝聚制备得到了分散良好且完整的聚电解质复合物微胶囊.在所研究的范围内,模板微粒中PSS的含量对微胶囊的形态结构和性能没有明显影响.与传统的层层组装微胶囊相比,聚电解质复合物微胶囊有较好的热稳定性,但在高盐浓度下尺寸收缩程度较大.由于和层层组装微胶囊相比缺乏结合紧密的有序结构,原位凝聚法制备的微胶囊囊壁的截留分子量较大.     

胶束增强型聚电解质微胶囊的制备

采用杂化碳酸钙微球作为模板, 利用LbL技术, 选择聚苯乙烯磺酸钠(PSS), 烯丙基胺的盐酸盐(PAH)和二烯丙基二甲基胺盐酸盐(PADA)聚电解质, 分别组装了PAH/PSS(弱/强)聚电解质胶囊和PADA/PSS(强/强)聚电解质微胶囊. 除去模板后得到了球形良好、分散均匀的聚电解质微胶囊. 研究结果表明, 利用杂化碳酸钙微球作为聚电解质微胶囊的模板, 得到的微胶囊的囊壁厚而致密, 同时, 由于组装采用的聚电解质的种类不同, 囊壁的微观形貌有较大差异.     

基于碳酸钙模板的特殊形状层层组装微胶囊的制备

以Na_2CO_3和CaCl_2为原料,聚烯丙基胺盐酸盐(PAH)为添加剂,通过磁力搅拌和超声混合的方式分别制备了两面凸碟形仿血小板形状和纺锤形的碳酸钙微粒.仿血小板形状的碳酸钙微粒为球霰石晶相,而纺锤形碳酸钙微粒为文石晶相.模板微粒中均掺杂了少量PAH.溶液混合方式和PAH添加剂的协同作用导致了特殊形状碳酸钙微粒的形成.以这2种粒子为模板通过层层组装技术分别制备了仿血小板形状和纺锤形微胶囊.得到的微胶囊能够在水中分散良好并保持模板的特殊形状.     

层层组装微胶囊的制备及其智能响应与物质包埋释放性能

在胶体微粒模板上进行聚合物间或聚合物和小分子间的交替层层(LBL)组装, 得到核壳微粒, 然后去除胶体微粒得到层层组装微胶囊. 综述了层层组装微胶囊在组装驱动力、智能响应性能和物质包埋与释放等方面的最新研究进展. 首先从组装驱动力和微胶囊结构调控出发, 简述了基于静电和氢键作用的LBL微胶囊的交联方法及交联所引起的微胶囊结构和性能的变化, 介绍了基于新驱动力如共价键作用、 碱基对作用和主客体作用制备LBL微胶囊的技术. 讨论了LBL微胶囊的智能响应性, 包括pH、 温度、 电荷、 光电磁和化学物质响应等. 详细介绍了LBL微胶囊包埋与释放功能物质尤其是药物、 蛋白和酶的方法及其特色, 包括LBL直接包埋与释放、 预吸附或共沉淀包埋与释放、 电荷选择性自沉积包埋与释放及爆释等. 最后, 着眼于微胶囊的靶向传递和功能器件, 介绍了采用静电作用和生物识别作用制备得到的微胶囊阵列.     

含乳糖聚电解质靶向微胶囊的层层自组装构筑

设计合成了己二酸乳糖乙烯酯/对苯乙烯磺酸钠共聚物（PLESS）,通过层层自组装技术构筑聚烯丙基胺盐酸盐（PAH）与含乳糖聚电解质PLESS的靶向微胶囊。以紫外-可见吸收光谱监测了PAH与PLESS在平面的石英片进行层层自组装过程,研究了不同实验条件（聚电解质浓度、溶液盐度、盐种类）对PAH/PLESS多层膜自组装的影响;PAH与PLESS在球形碳酸钙微球模板上层层自组装,去除模板后得到层状结构的微胶囊,用透射电镜（TEM）等方法观察其形态形貌;通过花生凝集素识别考察其潜在靶向性;通过细胞MTT活性试验评价其生物相容性。     

基于脲醛原位聚合制备聚硫密封剂微胶囊

设计了以脲醛树脂为壁材,聚硫橡胶密封剂为囊芯的微胶囊.在弱酸性条件下,尿素和甲醛在经乳化分散后的聚硫橡胶密封剂微粒表面发生原位聚合,制备了颗粒均匀、形貌规整、分散性好的密封剂微胶囊.通过红外光谱和表面观察技术对微胶囊进行了表征,并且对微胶囊中密封剂含量进行测定.通过对不同物料和反应影响因素(乳化剂浓度、搅拌速度、反应温度和p H值等)进行了系统考察,获得了优化的微胶囊制备工艺条件.为进一步拓展聚硫橡胶密封剂预涂敷技术和工程化应用提供了有益参考.     

通过可控沉积和交联制备蛋白质微胶囊

通过加入反溶剂控制牛血清白蛋白(BSA)在碳酸锰微粒表面的沉积, 形成连续薄膜后交联, 去除模板后得到了尺寸均匀和分散良好的BSA中空微胶囊. 囊壁厚度可以通过滴加乙醇控制; 囊壁的截留分子量在70000—155000之间. 由于BSA含有丰富的自由羧基, 得到的微胶囊表现出pH响应性. 这种快速简便制备微胶囊的方法也可以应用于其它蛋白质及酶, 得到的生物相容的微胶囊将在药物控制释放等领域具有潜在的应用价值.     

聚（异丙基甲基丙烯酰胺）@聚（N-异丙基丙烯酰胺）中空微凝胶合成过程的形态学表征

研究了聚（异丙基甲基丙烯酰胺）(PNIPMAM)@聚（N-异丙基丙烯酰胺）(PNIPAM)中空双壳微凝胶的合成过程. 结合扫描电子显微镜、透射电子显微镜的形态学表征方法可简捷直观获得核壳结构微凝胶的粒径尺寸、三维立体及内部超微结构,进而揭示PNIPMAM@PNIPAM中空同心双壳结构微凝胶合成过程的形态学特征.     

三维有序多孔图案化SiC陶瓷的制备

结合毛细管微模塑技术、模板技术和先驱体转化技术, 以图案化聚二甲基硅氧烷(PDMS)弹性体为模具,以氧化硅凝胶小球为模板, 以液态聚碳硅烷(PCS)为先驱体, 经过氧化硅凝胶小球图案化模板的形成, 先驱体的渗入, 模板中先驱体的交联, 弹性模具的去除, 图案化先驱体的无机化和模板的去除, 制备了图案化多孔SiC 陶瓷.研究结果表明：所制备的图案化多孔陶瓷中, 图案的尺寸受图案化PDMS 弹性模具的控制, 球形孔的孔径可由氧化硅凝胶小球来调节. 图案化陶瓷中球形孔不仅三维有序排列, 而且由于模板中小球的相互接触形成的“窗 口”使球形孔三维贯通.     

新型聚硅氧烷空心微胶囊的模板合成方法

在O/W型聚二甲基硅氧烷微乳模板核上，加入一定比例的二甲氧基硅烷(D型官 能团)和甲基三甲氧基硅烷(T型官能团)的有机硅单体，使之围绕在模板核表面聚合 交联形成核壳结构的聚硅氧烷微胶囊，然后用溶解透析的方法去除模板核而得到空 心微胶囊。TEM和AFM测定结果表明，合成的聚硅氧烷空心微胶囊结构完整，尺寸分 布约为200nm。成膜干燥后测试发现，空心微胶囊已完全崩塌成为薄煎饼型状态， 这与其内部的空心特征密切相关。     

Charge-controlled permeability of polyelectrolyte microcapsules

Multilayer microcapsules showing unique charge-controlled permeability have been successfully fabricated by employing poly(styrene sulfonate) (PSS)-doped CaCO3 particles as templates. Encapsulation of the PSS molecules is thus achieved after core removal. Scanning force microscopy (SFM), UV-vis, Raman spectroscopy, and zeta-potential confirm the existence of the PSS molecules in the CaCO3 particles and the resultant microcapsules, which are initially incorporated during the core fabrication process. A part of these additionally introduced PSS molecules interacts with PAH molecules residing on the inner surface of the multilayer wall to form a stable complex, while the other part is intertwined in the capsule wall or in a free state. Capsules with this structure possess many special features, such as highly sensitive permeability tuned by probe charge and environmentally controlled gating. They can completely reject negatively charged probes, but attract positively charged species to form a higher concentration in the capsule interior, as evidenced by confocal microscopy. For example, the capsules completely exclude dextran labeled with fluorescein isothiocyanate (FITC-dextran), but are permeable for dextran labeled with tetramethylrhodamine isothiocyanate (TRITC-dextran) having similar molecular mass (from 4 to 70 kDa), although there are only few charged dyes in a dextran chain. By reversing the charge of the probes through pH change, or by suppressing charge repulsion through salt addition, the permeation can be readily switched for proteins such as albumin or small dyes such as fluorescein sodium salt.     

Avidin/PSS membrane microcapsules with biotin-binding activity

Polyelectrolyte microcapsules with avidin-poly(styrene sulfonate) (PSS) membrane were prepared by a layer-by-layer deposition technique. The uptake and release of biotin-labeled fluorescein (b-FITC) as well as immobilization of biotin-labeled glucose oxidase (b-GOx) to the microcapsule were studied. The polyelectrolyte microcapsules were prepared by coating the surface of calcium carbonate (CaCO(3)) microparticles with an avidin/PSS multilayer membrane, followed by dissolution of CaCO(3) core in an ethylenediaminetetraacetic acid solution. Inner and outer poly(allylamine)/PSS films were required to isolate the microcapsules, whereas microcapsules could not be formed without the support. The uptake of b-FITC into the microcapsule was highly enhanced through a strong binding of b-FITC to avidin as compared with the uptake of biotin-free FITC. Release of b-FITC from the microcapsule was accelerated upon addition of biotin due to a competitive binding of the added biotin to the binding site of avidin. Similarly, the surface of microcapsule was modified with b-GOx with retaining its catalytic activity.     

Preparation and redox-controlled reversible response of ferrocene-modified poly(allylamine hydrochloride) microcapsules

Single-component microcapsules were fabricated by the in situ reaction of ferrocenecarboxaldehyde (Fc-CHO) with poly(allylamine hydrochloride) (PAH) doped inside CaCO(3) microparticles, followed by core removal. The PAH-Fc microcapsules had very thick shells with remnant PAH-Fc inside, leading to a robust capsule structure that is less collapsed in the dry state. This single-component microcapsule is stabilized by the hydrophobic aggregation of Fc moieties and the protection of hydrophilic PAH backbones. Because of the excellent redox properties of Fc, the PAH-Fc microcapsules showed redox sensitivity to oxidation and reduction, as confirmed by UV-vis absorption spectroscopy and confocal laser scanning microscopy, resulting in reversible swelling and shrinking (11.7 vs 5.5 μm) in their size. Consequently, the permeability was also reversibly tuned, leading to the controlled loading and release of desired substances such as dextran.     

Assembly and mechanical properties of phosphorus dendrimer/polyelectrolyte multilayer microcapsules

We report the preparation, characterization, and mechanical properties of polyelectrolyte/phosphorus dendrimer multilayer microcapsules. The shells of these microcapsules are composed either by alternating poly(styrenesulfonate) (PSS) and positively charged dendrimer G4(NH+Et2Cl-)96 or by alternating poly(allylamine hydrochloride) (PAH) and negatively charged dendrimer G4(CH-COO-Na+)96. The same multilayers were constructed on planar support to examine their layer-by-layer growth and to measure the multilayer thickness. Surface plasmon resonance spectroscopy (SPR) showed regular linear growth of the assembly upon each bilayer deposited. We probe the mechanical properties of these polyelectrolyte/dendrimer microcapsules by measuring force-deformation curves with the atomic force microscope (AFM). The experiment suggests that they are much softer than PSS/PAH microcapsules studied before. This softening is attributed to an enhanced permeability of the polyelectrolyte/dendrimer multilayer shells as compared with multilayers formed by linear polyelectrolytes. In contrast, Young's modulus of both dendrimer-based multilayers was found to be on the same order as that of PSS/PAH multilayers.     

Incorporation of Carbon Nanotubes into Hollow Microcapsules Using a Removable Template Assembly

Summary: Carboxylated multiwalled carbon nanotubes (MWNTs) were assembled with poly(allylamine hydrochloride) (PAH) onto decomposable colloidal particles, to subsequently yield hollow microcapsules after core removal. A sandwich structure with MWNTs layer embedded in poly(styrenesulfonate sodium salt) (PSS)/PAH multilayers was designed and constructed on melamine formaldehyde particles. Transmission electron microscopy and confocal microscopy revealed the hollow structure and good dispersity of the resultant microcapsules. The MWNTs were uniformly distributed on the capsule walls.

TEM images of (PSS/PAH)₅/MWNT/(PAH/PSS)₂ microcapsules templated on MF microparticles, after core decomposition (main). They still preserve their continuous and intact structure with no signs of rupture. Inset: magnified surface.     

Assembly of polymeric micelles into hollow microcapsules with extraordinary stability against extreme pH conditions

Hollow microcapsules containing polymeric micelles in their walls were fabricated by alternating assembly of poly(allylamine hydrochloride) (PAH) and poly(styrene- b-acrylic acid) (PS- b-PAA) micelles on MnCO(3) microparticles followed by sacrificing the templates in acid solution. The successful formation of PAH/micelle multilayers on both planar and curved substrates was confirmed by UV-vis spectroscopy, ellipsometry, and xi-potential measurements. The PS- b-PAA micelles retained their structure during the whole assembly process. The as-prepared microcapsules showed extraordinary stability against concentrated HCl (37%) and 0.1 M NaOH solutions. No variation in capsule size or shape was observed in acidic solution, while slight swelling and distortion of the capsules took place in alkaline solution. However, these capsules completely recovered their original size and morphology after being incubated in acidic solution again. The microcapsules, in which large voids exist between the micelle grains on the walls, were totally permeable to fluorescein-tagged dextran with an M(w) of 2000 kDa. Assembly of additional PAH/poly(sodium 4-styrenesulfonate) multilayers could substantially reduce the permeation of the same molecules. These multicompartmental capsules combine polymeric micelles with multilayer polyelectrolyte microcapsules and could possibly be imparted with multifunctions, thus possibly finding diverse applications in the fields of drug delivery, biosensing, and nanobiotechnology.     

Dynamics of counterions in polyelectrolyte multilayers studied by electro-optics

The electro-optical behavior of a multilayer constructed via layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) onto ellipsoidal β-FeOOH particles is examined using electric light scattering method. For fully charged polymers (at pH 4.5), the electro-optical effect is found to increase with polyelectrolyte layer number, showing a tendency to saturation in the linear growth regime. The effect is greater and of lower frequency of relaxation for the films ending with PAH in comparison to those with top PSS layer. Evidence is given that polarization of “condensed” counterions along the chains of the last-adsorbed polymer is mainly responsible for the observed electro-optical behavior of the polyelectrolyte multilayer. Although incorporation of “condensed” small ions into the film bulk seems probable for the PSS/PAH multilayer, their participation in the electro-optical effect is found negligible. The structural changes in the PSS/PAH multilayer due to the PAH deprotonation at pH 7.5 and the corresponding changes in the electro-optical effect confirm the key role of the last-adsorbed polymer for the behavior of the entire PSS/PAH film.     

Multilayer assembly of hyaluronic acid/poly(allylamine): control of the buildup for the production of hollow capsules

The objective of this work was to investigate the formation of hollow microcapsules composed of hyaluronic acid (HA) and poly(allylamine) (PAH) by layer-by-layer adsorption on CaCO 3 microparticles and subsequent core removal by addition of chelating agents for calcium ions. We found that the molecular weight of HA as well as the HA solution concentration used during deposition are crucial parameters influencing the multilayer structure. Whereas the effect of molecular weight of HA was mainly attributed to the porous structure of the template which allows penetration of polyelectrolytes when their size is below the maximum pore size of the template ( approximately 60 nm), that of the concentration of the HA solution was related to the intrinsic properties of the polysaccharide. Indeed, as shown by quartz crystal microbalance with dissipation monitoring as well as electron microscopy techniques, the latter leads to dense structures for concentrations from five to ten times the critical overlap concentration during adsorption. Such conditions were found to be favorable for the formation of hollow shells. Regarding conditions for core dissolution, we demonstrated the possibility to use either ethylenediaminetetraacetic acid (EDTA) or citric acid as chelating agents. However, in some cases, it was necessary to chemically cross-link the shell to maintain its integrity.     

Polyelectrolyte microcapsules templated on poly(styrene sulfonate)-doped CaCO3 particles for loading and sustained release of daunorubicin and doxorubicin

A strategy to incorporate and release anti-cancer drugs of daunorubicin (DNR) and doxorubicin (DOX) in preformed microcapsules is introduced, which is based on charge interaction mechanism. Oppositely charged poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) were assembled onto PSS doped-CaCO₃ colloidal particles in a layer-by-layer manner to yield core-shell particles. After removal of the carbonate cores, hollow microcapsules with entrapped PSS were fabricated, which showed spontaneous loading ability of positively charged DNR and DOX. The drug loading was confirmed quantitatively by observations under confocal laser scanning microscopy, transmission electron microscopy and scanning force microscopy. Quantification of the drug loading was performed under different conditions, revealing that a larger amount of drugs could be incorporated at higher drug feeding concentrations and higher salt concentrations. However, putting additional polyelectrolyte layers on the microcapsules after core removal resulted in weaker drug loading efficiency. The drug release behaviors from the microcapsules with different layer numbers were studied too, revealing a diffusion controlled release mechanism at the initial stage (4 h).