微乳中纳米胶囊的复凝聚法制备

在O/W型APG微乳液模板上, 以明胶和阿拉伯树胶作为包裹材料, 用复凝聚的方法制备纳米胶囊, 对影响纳米胶囊的合成条件进行了分析. 用粒度仪测定产物的粒径及其分布, 用透射电镜观察产物的形貌. 结果表明, 用复凝聚法在微乳中合成了粒度均匀、粒径30～100 nm的球性纳米胶囊. 考察了微乳液的组成、高分子的浓度和复凝聚的条件对纳米胶囊性质的影响. 纳米胶囊对氯氰菊酯的包裹率较高, 在60%以上. 本方法条件温和, 操作简单, 是一种新型的纳米胶囊合成技术.     

Microplastic-Free Microcapsules to Encapsulate Health-Promoting Limonene Oil

Fast-moving consumer goods (FMCG) industry has long included many appealing essential oils in products to meet consumers’ needs. Among all, the demand for limonene (LM) has recently surged due to its broad-spectrum health benefits, with applications in cosmetic, detergent, and food products. However, LM is extremely volatile, hence has often been encapsulated for a longer shelf-life. To date, mostly non-biodegradable synthetic polymers have been exploited to fabricate the microcapsule shells, and the resulting microcapsules contribute to the accumulation of microplastic in the environment. So far, information on LM-entrapping microcapsules with a natural microplastic-free shell and their mechanism of formation is limited, and there is lack of an in-depth characterisation of their mechanical and adhesive properties, which are crucial for understanding their potential performance at end-use applications. The present research aims towards developing safe microcapsules with a core of LM fabricated via complex coacervation (CC) using gum Arabic (GA) and fungally sourced chitosan (fCh) as shell precursors. The encapsulation efficiency (EE) for LM was quantified by gas chromatography (GC) separation method. The morphology of microcapsules was investigated via bright-field optical microscopy and scanning electron microscopy, and their mechanical properties were characterised using a micromanipulation technique. Moreover, the adhesive properties of the resulting microcapsules were studied via a bespoke microfluidic device fitted with a polyethylene-terephthalate (PET) substrate and operating at increasingly hydrodynamic shear stress (HSS). Spherical core-shell microcapsules (EE ~45%) with a mean size of 38 ± 2 μm and a relatively smooth surface were obtained. Their mean rupture force and nominal rupture stress were 0.9 ± 0.1 mN and 2.1 ± 0.2 MPa, respectively, which are comparable to those of other microcapsules with synthetic shells, e.g., urea- and melamine-formaldehyde. It was also found that the fCh-GA complexed shell provided promising adhesive properties onto PET films, leading to a microcapsule retention of ~85% and ~60% at low (≤50 mPa) and high shear stress (0.9 Pa), respectively. Interestingly, these values are similar to the adhesion data available in literature for microplastic-based microcapsules, such as melamine-formaldehyde (50–90%). Overall, these findings suggest that microplastics-free microcapsules with a core of oil have been successfully fabricated, and can offer a potential for more sustainable, consumer- and environmentally friendly applications in FMCGs.     

Synthesis and Properties Research on the Nanocapsulated Capsaicin by Simple Coacervation Method

A new nanoencapsulation was established in which small nanocapsules with a natural polymeric wall could be fabricated, capsulizing the capsaicin having pungent odor. The new nanoencapsulation is based on a simple coacervation process. In this technique, gelatin was used as the wall material of the nanocapsules, and an insoluble polymer film was formed after cross‐linking reaction. The shell formation mechanism and the effects of the process conditions such as shearing force, the gelatin viscosity, cross‐linking time, and so on, on the particle size of the nanocapsulated capsaicin (NC) agents were discussed. Meanwhile, the morphology and size distribution of the nanocapsules prepared by the most suitable conditions, were analyzed by Fourier transform infrared (FTIR) spectroscopy, laser particle size analyzer, transmission electron microscopy (TEM), and atomic force microscopy (AFM). The NC agents had a mean particle size of about 100 nm. Moreover, the thermal properties of the NC agents were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was demonstrated that the melting point and thermal pyrolysis temperature of the NC agents were improved from 75 to 100°C, 230 to 240°C, 310 to 320°C, and from 450 to 540°C compared with that of the uncovered capsaicin, which were caused by the encapsulation of the cross‐linked gelatin over the surface of the capsaicin.     

Study of Complex Coacervation of Gelatin A and Sodium Alginate for Microencapsulation of Olive Oil

Complex coacervation of gelatin A and sodium alginate was carried out to obtain the maximum coacervate yield. Turbidity and coacervate yield (%) measurements were carried out to support the ratio of the two polymers and pH that produced maximum coacervation. The optimum ratio between gelatin A-sodium alginate and pH to form the maximum coacervate complex was found to be 3.5:1 and 3.5–3.8, respectively. Olive oil microencapsulation was carried out at the optimized ratio and pH. Microcapsules were crosslinked by using glutaraldehyde. Scanning electron microscopy studies confirmed the formation of free flowing spherical microcapsules of different sizes. The size of microcapsules increased with the increase in the concentration of the polymer. The encapsulation efficiency and the release rates of olive oil were dependent on the amount of crosslinker, oil loading and polymer concentration. Thermogravimetric study revealed improvement of thermal stability with crosslinking. Fourier Transform Infrared Spectroscopy study showed that there was no significant interaction between olive oil and gelatin-alginate complex.     

昆虫激素十二醇微胶囊的制备与释放行为研究

利用昆虫雌性激素对昆虫进行干扰交配是近年来使用的一种新技术,可替代农药杀虫剂达到高选择性无毒无药灭害的目的。迄今为止的相关研究及应用技术都是使用载有昆虫激素的棉条、纸片、塑胶管等装置,以一定密度置于果园或农田。十二醇是较为简单的一个存在于多种昆虫的雌性激素中化合物。本文首次探索使用聚合物微球水分散体系将昆虫激素十二醇(C12OH)包覆在聚合物微球中,通过改变水分散体系的制备方法、复合微球壁的交联度等探讨了此类体系对C12OH的可控释放。本工作首先通过测定阿拉伯胶明胶复凝聚过程的透光率、ζ电位,确定了阿拉伯胶-明胶的重量配比为1时可达最大复凝聚。在此基础上,制备了一系列不同交联剂戊二醛含量的复合微胶囊。结果表明微胶囊壁材的交联度随交联剂量明显上升,其对C12OH的包覆率经1%戊二醛交联后即提高至未交联体系的约三倍。但进一步提高戊二醛的含量,虽然胶囊的交联度仍明显上升,但对C12OH的包覆率基本保持恒定。使用同样量的甲醛可达同样交联效果,但对C12OH的包覆率有明显提高。在恒温恒湿条件下对各胶囊的C12OH释放行为进行了表征,结果显示交联胶囊可明显提高C12OH的恒速释放时间,交联度越高,恒速释放越稳定。本工作表明通过本方法确实可以达到将昆虫激素包覆在聚合物颗粒中并达到可控释放。     

Polyelectrolyte complexation between poly(methacrylic acid,sodium salt) and poly(diallyldimethylammonium chloride) or poly[2‐(methacryloyloxyethyl) trimethylammonium chloride]

Polyelectrolyte complexes between poly(methacrylic acid, sodium salt) and poly(diallyldimethylammonium chloride) (PDADMAC) or poly[2‐(methacryloyloxyethyl)trimethylammonium chloride] (PMOETAC) form gels, liquid phases, or soluble complexes depending on charge ratio, total polymer loading, polymer molecular weight, and ionic strength. Increasing the ionic strength of the medium led most polyelectrolyte pairs to transition from gel through liquid complexes (complex coacervate) to soluble complexes. These transitions shift to higher ionic strengths for higher molecular weight polymers, as well as for PMOETAC compared to PDADMAC. The complex phases swelled with increasing polymer loading, ultimately merging with the supernatant phase at a critical polymer loading. The isolated liquid complex phases below and above this critical loading were temperature‐sensitive, showing cloud points followed by macroscopic phase separation upon heating. Incorporating 5 mol % lauryl methacrylate into the polyanion led to increased complex yield with PDADMAC, and increased resistance to ionic strength. In contrast, incorporating 30 mol % of oligo(ethylene glycol) methacrylate into the polyanion led to decreased complex yield, and to lower resistance to ionic strength. Two polyelectrolyte systems that produced liquid complexes were used to encapsulate hydrophobic oils, and in one case were used to demonstrate the feasibility of crosslinking the resulting capsule walls. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4129–4143, 2007     

Monodisperse gelatin microspheres as a drug delivery vehicle: release profile and effect of crosslinking density

Uniform gelatin microspheres (GMS) of a wet size of 100 microm in diameter were fabricated by the electric field assisted precision particle fabrication (E-PPF) method and crosslinked with different glutaraldehyde (GA) concentrations to study the effect of the crosslinking density on drug release. The drug release profiles of the crosslinked GMS were studied along with the intraparticle drug distribution and the particle degradation characteristics. Due to the concentration gradient of GA along the diffusion path into the GMS, the crosslinking density is higher on the GMS surface, making it less susceptible to degradation. As a result, the GMS with higher GA concentrations (0.375-0.875%) exhibited a highly resistant surface toward enzymatic degradation. On the other hand, the amount of drug complexation at the surface decreases as the GA concentration increases, which can be attributed to the lowered basicity of gelatin caused by the increased crosslinking density. These factors collectively affect the drug release kinetics and give rise to similar release profiles for GMS above a GA concentration of 0.375%.     

明胶与AgBr晶体颗粒相互作用的研究

It was found that IR absorption band at 1383 cm - 1 was stronger for AgBr crystal particles . This band was not observed but there was an amide I band at 1630 cm - 1 or 1640 cm - 1 for gelatin-AgBr emulsion after ensymolysis. This variation meant that gelatin was adsorbed on the AgBr crystal particles. The IR analysis was performed for gelatin with added Br- to show the possible interaction between gelatin and AgBr particles. The frequence of NH3+ absorption band for gelatins with added Br- was lower than that for gelatins without added Br-. The frequence shift of NH3+ band around 3300 cm-1 in the spectrum of gelatins indicated that gelatin could be adsorbed by AgBr with NH3+ and Br- in addition to chemical interaction between Ag+ and N atom or/and between Ag+ and S atom. Moreover,there was probably a kind of force between the hydrophobic parts of AgBr crystal surface and the hydrophobic side-chain groups of gelatin. It may be the van der Walls force. It had influence on IR spectrum of emulsion from 1000 cm-1 to 1200 cm-1 . Because there was a difference in photographic characters or crystal particle size between fish gelatin emulsion and bovine gelatin emulsion,their interactions were compared. In general,IR study suggested that gelatin was adsorbed on AgBr crystal particles . This adsorption could be caused by coulombic and van der Walls forces apart from the chemical affinity between gelatin and AgBr crystal particles.     

A Way to Prepare Core‐Shell Biocompatible Polymeric Nano‐Particles from Gelatin and Acrylic Acid

Narrowly distributed core‐shell nano‐particles at relatively high concentration (30 mg/mL) were prepared via in situ polymerization of acrylic acid in an aqueous solution of biocompatible gelatin. These polymeric nano‐particles, in aqueous solution, had cores mainly comprised of an insoluble inter‐polymer complex of poly(acrylic acid, PAA) and gelatin and shells comprised of soluble gelatin (denoted as gelatin/PAA nano‐particles). Dynamic light scattering and electrophoretic light scattering techniques were used to trace the in situ polymerization process. The structure of the gelatin/PAA nano‐particle was further locked‐in via shell crosslinking; i.e., the reaction between glutaraldehyde and gelatin. Scanning force microscopy (SFM) was used to observe the morphologies of the particles before and after cross‐linking. Furthermore, the pH responsive behaviors of the gelatin/PAA nano‐particles before and after shell crosslinking were studied.     

Catalytic behaviors of silica‐supported natural biopolymer–oxalic acid–Pt complexes in hydrogenation

Three kinds of natural biopolymers, gelatin, alginic acid and sodium carboxymethylcellulose (NaCMC), were reacted with oxalic acid in the presence of silica to yield complexes on the surface of silica, followed by reaction with H₂PtCl₆ 6H₂O to form Pt complexes, SiO₂–gelatin–(COOH)₂–Pt, SiO₂–alginic acid–(COOH)₂–Pt, and SiO₂–NaCMC–(COOH)₂–Pt, respectively. These complexes were able to catalyze the hydrogenation of 1‐heptene to give n‐heptane and that of nitrobenzene to give aniline at 25 °C and under 1 atm H₂ in 100% yields. Experimental data show that the catalysts were very stable and could be reused without any remarkable change in catalytic activity. Copyright © 2000 John Wiley & Sons, Ltd.     

明胶大分子中的正电子湮没行为

The microstructural properties of gelatin samples derived from the bovine bone as well as skin of fish which inhabit in the cold sea were examined at molecular scale by using the positron annihilation lifetime spectroscopy（PALS）. The longest-lived component of PALS provides information about the free-volume holes in gelatin macromolecules. The results show that both average size and number of free-volume holes in the fish gelatin macromolecules are lower than those in the bovine gelatin macromolecules. Silver halide emulsions were also precipitated by using the balanced double-jet technique,for which two types of media containing fish gelatin and bone gelatin were used in the stage of nucleus formation,respectively. The monodispersibility of silver halide crystallites can be improved and the growth and coalescence of nucleus grains can be restricted when the fish gelatino-peptizer was used as dispersion medium at the nucleus formation. It thus suggested that the function of gelatino-peptizers as protective colloid is correlated with the microstructure character of gelatin macromolecules established by PALS. The gelatino-peptizer derived from the fish skin possesses stronger power governing nucleation and growth of silver halide grains compared with that made from the bovine bone.     

Microencapsulation of dichromate and paracetamol with Eudragit Retard polymers using phase separation by nonsolvent addition

A coacervation technique for microencapsulation using Eudragit Retard polymers [poly(methyl methacrylates) substituted by quaternary ammonium groups] as wall material is described, based upon phase separation using a cold chloroform-cyclohexane mixture together with polyisobutylene as a stabilizer. The effect of various parameters on the nature and properties of the microcapsules of potassium dichromate and paracetamol has been studied, in particular the alteration in wall content and structure and release rate of contents. The microcapsules are discrete, their properties are reproducible, and various degrees of sustained release are obtained.     

复凝聚法制备昆虫激素模拟物十二醇微胶囊及其释放性能

以明胶(GE)和阿拉伯胶(AG)为壁材, 通过复凝聚法将昆虫激素模拟物十二醇(C12OH)包覆在微胶囊中, 改变微胶囊壁材的浓度和交联度, 探讨了体系中C12OH的可控释放性能. 通过对壁材质量比为1及不同pH条件下的壁材凝聚率测试确定最佳复凝聚的pH为4.0; 考察了不同分散剂对微胶囊及其分散液性能的影响, 确定以Tween 20/Span 80(质量比1∶1)作为复凝聚法包覆C12OH体系的分散剂. 在壁材质量分数大于或等于3%条件下制备的微胶囊粒径大于壁材质量分数为2%的微胶囊, 胶囊的载药量和C12OH包覆率明显高于后者. 增加交联剂的用量, 壁材交联度、胶囊的载药量和C12OH包覆率都显著提高. 在相同用量的情况下, 用甲醛作交联剂时得到的微胶囊的交联度比用戊二醛作交联剂时的要低, 但其对C12OH的包覆率更高. 通过扫描电镜对微胶囊进行了分析, 认为GE与AG通过复凝聚能够将C12OH包覆在微胶囊内部. 对胶囊中C12OH在恒温恒湿条件下的释放研究结果表明, 3%与4%壁材含量下1%戊二醛交联的微胶囊和5%壁材含量下4%戊二醛交联的微胶囊中C12OH的释放行为有明显的可控性. 通过调节微胶囊的壁材含量和交联度可以达到昆虫激素可控释放的目的.     

Sequestration of Methylene Blue into Polyelectrolyte Complex Coacervates

Polyelectrolyte complex coacervation is a process that has been proposed as a model for protocell formation due to its ability to compartmentalize chemicals in solution without a membrane. During the liquid–liquid phase separation that results in water rich and polyelectrolyte rich phases, small molecules present in solution selectively partition to one phase over the other. This sequestration is based on relative affinities. Here, a study of the sequestration of methylene blue (MB) into the complex coacervate phase of three pairs of synthetic polyelectrolytes is presented; branched polyethylene imine with polyacrylic acid, polyvinyl sulfonate, or poly(4‐styrenesulfonic acid). These materials are characterized with UV–vis, zeta potential measurements, and dynamic light scattering. The branched polyethylene imine/poly(4‐styrenesulfonic acid) system is shown to have a significantly higher sequestration capacity for the MB as compared to either of the other two systems, based on π–π interactions which are not possible in the other systems.

     

A Water‐Borne Adhesive Modeled after the Sandcastle Glue of P. californica

Polyacrylate glue protein analogs of the glue secreted by Phragmatopoma californica, a marine polycheate, were synthesized with phosphate, primary amine, and catechol sidechains with molar ratios similar to the natural glue proteins. Aqueous mixtures of the mimetic polyelectrolytes condensed into liquid complex coacervates around neutral pH. Wet cortical bone specimens bonded with the coacervates, oxidatively crosslinked through catechol sidechains, had bond strengths nearly 40% of the strength of a commercial cyanoacrylate. The unique material properties of complex coacervates may be ideal for development of clinically useful adhesives and other biomaterials.

     

Microencapsulation of Calcium Using Water-in-Oil-in-Water Double Emulsion Method

Calcium in the form of tricalcium phosphate was encapsulated in the inner water phase of water-in-oil-in-water emulsion. Efficiency and payload of microcapsules were optimized using a D-optimal mixture design with four components (gelatin, agar, primary water-in-oil emulsion, and water in outer phase). Release profiles of calcium from microcapsules were determined at 4°C over 12 days. It was found that microencapsulation efficiency increased by increasing of water-in-oil emulsion to 45% and then decreased at higher contents of this portion. However, payload increased continuously with increase of water-in-oil fraction. Less calcium was released when both biopolymers and water-in-oil emulsion contents were increased.     

UCST‐type phase transition driven by protein‐derived polypeptide employing gelatin and chitosan

Here, we describe the thermosensitive reversible phase transition behaviors of polyelectrolyte complex composed of gelatin and chitosan (G/C complex). An aqueous dispersion of the G/C complexes showed a clear upper critical solution temperature (UCST) at around 30°C. The thermosensitive phase transition behavior showed excellent reversibility and large thermal hysteresis as a usual phenomenon based on the intra‐ and inter‐molecular interaction change. A high correlation was observed between the UCST of the G/C complex and the helix‐melting temperature of gelatin by circular dichroism, which suggested that the phase transition of the G/C complex corresponded to the secondary structure (helix‐coil) transition of gelatin. Notably, the UCST of the G/C complex shifted to lower temperatures in the presence of urea, which is well known to destabilize gelatin, whereas the addition of salt led to the dissolution of the G/C complex. It is envisaged that the results of this study will have a significant impact on the fabrication of UCST‐type thermosensitive materials, which can be utilized under aqueous physiological conditions using well‐known biopolymers. This protein‐derived functional material, which responds to the secondary structure transition, could also be used for the development of novel UCST‐type thermosensitive biomaterials. Copyright © 2017 John Wiley & Sons, Ltd.