Preparation of ferromagnetic microcapsules for hyperthermia using water/oil emulsion as a reaction field

Hyperthermia is a minimally invasive cancer treatment. As hyperthermia thermoseeds, ferromagnetic microcapsules of 20–30 μm in diameter have attracted much attention since their embolization effect cuts off the nutrition supply into cancer cells, ensuring that the microcapsules efficiently reach the tumor. In the present study, ferromagnetic microcapsules were prepared via iron hydroxide precipitation from a water/oil emulsion and subsequent hydrothermal treatment. The fundamental conditions for obtaining microcapsules of suitable size were investigated. The diameter of the obtained microcapsules tended to decrease as rotation speed increased during emulsion preparation or surfactant concentration in the oil phase. The sphericity of the microcapsules was improved at low surfactant concentration. A large amount of 20–30 μm-diameter magnetite microcapsules were obtained when the rotation speed and surfactant concentration were fixed at 1500 rpm and 0.35 mass%, respectively. The obtained microcapsules embedded in agar phantom exhibited heat generation under an alternating magnetic field.     

Direct encapsulation of water-soluble drug into silica microcapsules for sustained release applications

Direct encapsulation of water-soluble drug into silica microcapsules was facilely achieved by a sol-gel process of tetraethoxysilane (TEOS) in W/O emulsion with hydrochloric acid (HCl) aqueous solution containing Tween 80 and drug as well as cyclohexane solution containing Span 80. Two water-soluble drugs of gentamicin sulphate (GS) and salbutamol sulphate (SS) were chosen as model drugs. The characterization of drug encapsulated silica microcapsules by scanning electronic microscopy (SEM), FTIR, thermogravimetry (TG) and N₂ adsorption-desorption analyses indicated that drug was successfully entrapped into silica microcapsules. The as-prepared silica microcapsules were uniform spherical particles with hollow structure, good dispersion and a size of 5-10 μm, and had a specific surface area of about 306 m²/g. UV-vis and thermogravimetry (TG) analyses were performed to determine the amount of drug encapsulated in the microcapsules. The BJH pore size distribution (PSD) of silica microcapsules before and after removing drug was examined. In vitro release behavior of drug in simulated body fluid (SBF) revealed that such system exhibited excellent sustained release properties.     

Numerical investigations of acoustic agglomeration of liquid droplet using a coupled CFD-DEM model

Acoustic agglomeration is widely considered a potentially effective technology for application in artificial defogging and precipitation. A coupled three-dimensional Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) model was constructed to investigate the agglomeration performance of liquid droplets in the acoustic field. The acoustic field is calculated by solving the Linearized Navier-Stokes Equations (LNSEs) in the time domain, and the background flow is initially obtained using the Reynolds-averaged Navier-Stokes (RANS) equations with a k–ε turbulence model. The motion of the droplet aerosol follows Newton’s second law with fluid-particle and particle-particle interactions, including collision, agglomeration, and fragmentation. The agglomeration performance of liquid droplets under high-intensity acoustic waves was numerically investigated in terms of the effects of the acoustic properties as well as the droplet characteristics.The numerical results show that it is necessary to consider droplet fragmentation in the process of acoustic agglomeration under the action of high-speed jet. The sprayed droplets are more likely to collide and condense than those without a breakup model, which has rarely been reported in previous studies. Acoustic frequency has a significant effect on agglomeration behavior, with optimal frequencies of about 225 Hz, 150 Hz, and 125 Hz corresponding to droplets with mode diameters of 15.97 μm, 25.85 μm, and 42.88 μm, respectively. However, despite the fact that most studies favoured large acoustic intensity for agglomeration performance, the agglomeration performance of aerosol particles is not always positively correlated with acoustic intensity, especially for large droplets. The optimal intensity of droplet with d_p = 42.88 μm is in the range of 120-130 dB, which is smaller than the maximum operation pressure of 150 dB used in this study. In addition, an effective approach to increase the agglomerate size is to extend the residence time that liquid droplets are exposed in the acoustic and flow field, especially because the typical acoustic intensity of actual operation is usually not that high.     

Preparation of dendrimer-loaded microcapsules by a layer-by-layer deposition of polyelectrolytes

Poly(amidoamine) dendrimer-loaded microcapsules were prepared by a layer-by-layer deposition of poly(allylamine hydrochloride) and poly(vinyl sulfate) on the surface of calcium carbonate (CaCO₃) microparticles that contain poly(amidoamine) dendrimer, followed by dissolution of CaCO₃ core. A fluorescence spectroscopy revealed that a fluorescent dendrimer labeled with trimethylrhodamine is successfully encapsulated in the microcapsules. The leakage of the dendrimer out of the microcapsule was negligible at pH 4.0, while 7% and 25% of dendrimer were released after 6 h in the media at pH 7.0 and 9.0, respectively. The binding and release properties of the dendrimer-loaded microcapsules were evaluated using two kinds of organic dyes Rose Bengal (RB) and 1-anilinonaphthalene-8-sulfonic acid (ANS). RB was accommodated in the microcapsules and released rapidly into buffer solution at pH 8.0, while the release was suppressed at pH 7.0 probably due to binding of RB to dendrimer in the capsules. A fluorescence emission of ANS was highly enhanced in the presence of dendrimer-loaded microcapsules, suggesting a successful binding of ANS to dendrimer in the microcapsules because the fluorescence intensity was not enhanced in the presence of dendrimer-free microcapsules. The kinetic studies revealed that the rate of uptake of ANS in the dendrimer-loaded microcapsules was determined by the rate of transport of ANS across the capsule wall. On the other hand, the dissociation of ANS from PAMAM is the rate-determining step for the release of ANS from the microcapsules.     

纳米微球在生物医药领域的应用

纳米微球技术是近年来在生物技术应用中最为热门的前沿技术之一。各种微球产品的应用给生物技术研究带来了新的课题,形成了众多新的研究领域。从生物技术的发展现状和未来方向出发,对纳米微球在生物医药研究中几个重要领域的应用前案进行了综述。     

Interlaminar fracture of CF/EP composite containing a dual-component microencapsulated self-healant

We present an experimental study of the self-healing ability of carbon fibre/epoxy (CF/EP) composite laminates with microencapsulated epoxy and its hardener (mercaptan) as a healing agent. Epoxy- and hardener-loaded microcapsules (average size large: 123 μm; small: 65 μm) were prepared by in situ polymerisation in an oil-in-water emulsion and were dry-dispersed at the ratio 1:1 on the surface of unidirectional carbon fabric layer. The CF/EP laminates were fabricated using a vacuum-assisted resin infusion (VARI) process. Width-tapered double cantilever beam (WTDCB) specimens were used to measure mode-I interlaminar fracture toughness of the CF/EP composites with a pre-crack in the centre plane where the microcapsules were placed. Incorporation of the dual-component healant stored in the fragile microcapsules provided the laminates with healing capability on delamination damage by recovering as much as 80% of its fracture toughness. It was also observed that the recovery of fracture toughness was directly correlated with the amount of healant covering the fracture plane, with the highest healing efficiency obtained for the laminate with large capsules.     

Novel chitosan microsphere-templated microcapsules suitable for spontaneous loading of heparin

This report aimed to describe a novel type of core–shell-structured microcapsules suitable for spontaneous loading of anticoagulant heparin. Chitosan (CS) microspheres were fabricated by a sodium sulfate-based precipitation process. The microspheres were approximately 1 μm in size and applied as templates for microcapsules prepared by the layer-by-layer (LbL) self-assembly technique. Polyelectrolytes including polyanion poly(styrene sulfonate) and polycation CS were alternately deposited on CS microsphere templates, monitored by flow cytometry and zeta potential analysis. Scanning electron microscopy, confocal laser scanning microscopy, fluorescence microscopy, flow cytometry and laser particle size analysis were used to characterize the microcapsules. The resulted microcapsules were about 1 μm in average diameter, and allowed spontaneous loading of heparin through electrostatic interaction, with the encapsulation efficiency and loading capacity of 74.4% and 10.0%, respectively. Moreover, heparin could be released from the microcapsules in phosphate buffered saline at pH 7.4. It is suggested that the type of microcapsules may provide a new and effective system of heparin delivery for pharmaceutical use.     

Encapsulation of a pressure sensitive adhesive by spray-cooling: Optimum formulation and processing conditions

An industrial pressure sensitive adhesive (PSA) was encapsulated by spray-cooling using hydrogenated palm oil. A screening design methodology was used to evaluate the impact of some formulation and process variables on the particle properties. Six operating factors were retained and the results considered were the production yield, the particle volume-surface average diameter D₃₂, the residual humidity, the ratio of the fusion enthalpies of the polymorphs α and β′/β and the normalized peeling force. The statistical analysis of the results showed a negligible impact of the parameters related to the process. The heating temperature, the PSA and surfactant ratios were the most significant factors. It was possible to produce spherical particles with a mean size of 17.7 μm and a normalized peeling force of 0.218 N m²/g. The production yield was 70%. A duplicate test confirmed the results. Mechanical tests on unitary particles showed an increase of the rupture and adhesion forces with particle size.     

Electrical and optical properties of reduced graphene oxide and multi-walled carbon nanotubes based nanocomposites: A comparative study

Graphene and multi-walled carbon nanotubes have attracted interest for a number of potential applications. One of the most actively pursued applications uses graphene and carbon nanotubes as a transparent conducting electrode in solar cells, displays or touch screens. In this work, in situ reduced graphene oxide/Poly (vinyl alcohol) and multi-walled carbon nanotubes/Sodium Dodecyl Sulfate/Poly (vinyl alcohol) composites were prepared by water dispersion and different reduction treatments. Comparative studies were conducted to explore the electrical and optical properties of nanocomposites based on graphene and multi-walled carbon nanotubes. A thermal reduction of graphene oxide was more effective, producing films with sheet resistances as low as 10²–10³ Ω/square with 80% transmittance for 550 nm light. The percolation threshold of the thermally reduced graphene oxide composites (0.35 vol%) was much lower than that of the chemically reduced graphene oxide composites (0.57 vol%), and than that of the carbon nanotubes composites (0.47 vol%). The Seebeck coefficient of graphene oxide films changes from about 40 μV/K to −30 μV/K after an annealing of three hours at 200 °C. The optical absorption of the nanocomposites showed a high absorbance in near UV regions and the photoluminescence enhancement was achieved at 1 wt% graphene loading, while the carbon nanotubes based composite presents a significant emission at 0.7 wt% followed with a photoluminescence quenching at higher fraction of the nanofillers 1.6 wt% TRGO and 1 wt% MWCNTs.     

桉叶精油微胶囊包埋油含量测定方法的比较

目的比较3种测定桉叶精油微胶囊包埋油含量的方法,为包埋油含量的测定提供科学依据。方法采用干燥失重法、挥发油测定法和紫外分光光度法对桉叶精油微胶囊包埋油含量进行测定,并对这3种方法进行对比分析。结果 3种方法的RSD值均不超过5%,加标回收率均在90%~120%之间,均具有良好的精密度和准确度。干燥失重法测定结果偏高。紫外分光光度法操作复杂,相对成本较高,但检测速度快。挥发油测定法操作简便、成本低,但耗时较长。结论 3种方法均适合包埋油含量的测定,但挥发油测定法和紫外分光光度法精密度和准确度更高。     

Preparation and characterization of poly(o-phenylenediamine) microrods using ferric chloride as an oxidant

Microrods of poly(o-phenylenediamine) (PoPD) were synthesized by a templateless method using ferric chloride as an oxidant. The microrod morphologies of the resulting PoPD were confirmed by scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images. When the concentration of o-phenylenediamine (oPD) was 0.03 M, the microrods of PoPD had a diameter in the range of 0.5-2 μm and a length from 2 μm to 20 μm. It was found that the concentration of oPD monomer had much influence on the morphology of the obtained PoPD. When the concentration of oPD was lower than 0.03 M, long microrods could be observed. However, when the concentration of oPD monomer was higher than 0.12 M, the length of the microrods became very short and the diameter became bigger. Fourier transform infrared spectroscopy (FTIR), UV-vis absorption spectra and X-ray diffraction (XRD) were used to characterize the structure of the obtained PoPD microrods.     

Latex derived blends of poly(vinyl acetate) and natural rubber: thermal and mechanical properties

Poly(vinyl acetate) (PVAc) and natural rubber blends (NR) were prepared by low shear blending of the corresponding lattices. Thin films were cast using a doctor blade technique. SEM and DMA confirmed the essential immiscibility of the two polymers. Even when the poly(vinyl acetate) forms the matrix phase, it still contains domains encapsulated by a rubber phase where particles that resemble the original latex are visible. This incomplete droplet coalescence of the poly(vinyl acetate) is attributed to the fact that the rubber latex droplets were an order of magnitude smaller than the poly(vinyl acetate) latex droplets. Tensile testing revealed a nonlinear dependence of tensile strength and elongation on blend composition. Surprisingly good tensile yield strengths were obtained at intermediate to high PVAc contents. Thermogravimetric analysis of degradation in air and nitrogen atmospheres indicated independent degradation of the parent polymers.     

Molten-salt assisted synthesis and characterization of ZrSiO4 coated carbon core-shell structure pigment

A core-shell structure zirconium silicate encapsulated carbon (C@ZrSiO₄) pigment was synthesized by a molten-salt assisted method. The experimental results indicated that the Na₂WO₄ molten-salt associated with the synthesis of ZrSiO₄ at low temperature and controlled the morphology of the encapsulation pigment simultaneously. The encapsulated pigment prepared with the assistance of Na₂WO₄ molten-salt showed regular microcubes about 3.0 μm, while the pigment in the absence of molten-salt have serious aggregation with a particle size of 12.78 μm. Moreover, the maximum addition amount of carbon black was increased significantly from 15 wt% to 40 wt% after adding molten-salt, while the chromatic value L* of C@ZrSiO₄ pigment decreased from 68.21 to 33.08 accordingly. The pigment exhibited excellent thermal stability at high temperature, making it a promising candidate for ceramic decoration.     

The synthesis of novel NiO microsphere architectures with electrochemical behavior

Novel hierarchical precursor microsphere architectures were successfully fabricated via microwave hydrothermal process in the presence of an anion surfactant Poly(N-vinyl-2-pyrrolidone). These microspheres with diameter of 0.7-1.5 μm are composed of stacked nanoparticles. NiO with similar morphology was also obtained by a simple thermal decomposition of the as-synthesized precursor at 500 °C for 2 h in air. We observed that the pure phase NiO has been formed. And the optical absorption band gap of NiO prepared has been found to be of 3.46 eV. These NiO microspheres are also composed of stacked nanoparticles with the size from 20 to 60 nm. The specific capacitance of NiO is about 208.4 F/g. Finally, a simple formation mechanism is also discussed by a scheme.     

毒死蜱/脲醛树脂微胶囊的制备工艺优化及缓释动力学

随着人们健康与环保意识的不断加强,农药施用量大、效率低、高残留等问题日益受到人们的重视,对农药进行微胶囊化,有助于有效解决当前农药使用过程中所面临的问题。采用脲醛树脂作为壁材,以十二烷基硫酸钠为乳化剂,采用原位聚合法制备毒死蜱/脲醛树脂微胶囊。研究了乳化剂种类和用量、pH值、酸化时间对微胶囊粒径及其分布的影响,并进一步探讨微胶囊的载药量、包封率及释放动力学。结果表明,采用3%(质量分数)的十二烷基硫酸钠为乳化剂,在酸化时间为90min、酸化终点pH值为2.5、搅拌速度为1 200r/min、芯壁比为1∶3、固化温度为60℃时,所制备的毒死蜱/脲醛树脂微胶囊的粒径分布窄,平均粒径约为113μm,载药量达53%以上,包封率达62%以上。毒死蜱/脲醛树脂微胶囊的缓释性能及动力学研究结果显示,所制备的毒死蜱/脲醛树脂微胶囊的缓释效果明显,10天内能释放90%的药物,释放过程遵循Fick扩散机理。可见,制备的毒死蜱/脲醛树脂微胶囊具有较高的载药量、较好的包封率以及缓释性能,可进一步开发为新型的农药制剂,并为开发缓释农药新剂型提供理论支持与实践参考。     

Preparation and characterization of PNIPAAm-b-PLA/Fe3O4 thermo-responsive and magnetic composite micelles

Novel magnetic micelles with the flowerlike morphology were prepared with Fe₃O₄ nanoparticles and poly(N-isopropylacrylamide)-block-polylactide (PNIPAAm-b-PLA) copolymers by a dialysis method. The diameter of flowerlike micelles was about 1 μm. The core and shell of the micelles were hydrophilic, while the other area of the micelles was hydrophobic. The lower critical solution temperature (LCST) of PNIPAAm-b-PLA was about 38 °C. The magnetic intensity of Fe₃O₄ nanoparticles decreased after they were encapsulated into PNIPAAm-b-PLA micelles. Thermo-responsive and magnetic properties of the micelles would provide useful applications in the target drug delivery and release system.     

Fabrication and performances of microencapsulated paraffin composites with polymethylmethacrylate shell based on ultraviolet irradiation-initiated

In order to identify the validity of fabricating microencapsulated phase change material by ultraviolet irradiation-initiated method, the paraffin wax/polymethyl methacrylate microcapsules were prepared. The structural characteristics and thermal properties of the microcapsules were also determined by various techniques. The results of differential scanning calorimetry analyses indicate that the melting and freezing temperatures and latent heats of the microcapsules are 55.8 °C, 50.1 °C and 106.9 J g⁻¹, 112.3 J g⁻¹, respectively. Morphology and chemical characteristic analysis indicate that the spherical microcapsules were formed with average diameter of 0.21 μm and maximum microencapsulation ratio of 66 wt.% without leakage of core materials. The results of accelerated thermal cyclic test show that the microcapsules have good thermal reliability and chemical stability although they were subjected 3000 melting/freezing cycles. Based on all these results, it can be concluded that the microencapsulated paraffin composites have good potential for thermal energy storage purposes and ultraviolet irradiation-initiated method is a prominent candidate for preparing microencapsulated PCMs.     

Theoretical analysis of acoustic and turbulent agglomeration of droplet aerosols

This study meticulously explores the agglomeration mechanisms in microscale droplet aerosols, specifically focusing on acoustic and turbulent agglomeration mechanisms. Our theoretical analysis reveals a significant impact of orthokinetic and hydrodynamic processes on acoustic agglomeration. The acoustic wake effect elucidates the swift replenishment of small particles subsequent to an orthokinetic phase. An optimal frequency, varying for different droplets, was identified in orthokinetic agglomeration within the 50–250 Hz range. Hydrodynamic agglomeration remained relatively stable at an acoustic frequency exceeding 1000 Hz. The aggregation kernel function, denoted as K_ij, exhibited a significant increase with increasing sound pressure levels, reaching up to 10⁻⁸ s⁻¹. Environmental temperature had a predominantly positive effect on orthokinetic and Brownian agglomeration, although it exhibited an inhibitory effect on hydrodynamic agglomeration. For raindrops, a correlation was identified between particle spacing and K_ij; a larger particle spacing corresponded to a smaller K_ij. Despite an increase in particle spacing to 50 times the particle diameter, the hydrodynamic effect persisted. The aggregation kernel function linked to Brownian thermal motion was found to be 3–4 orders of magnitude lower than that of orthokinetic and hydrodynamic interactions. Additionally, the turbulent agglomeration kernel function for fog, cloud, and rain droplets with corresponding parent nuclei of 100 μm was of the same order of magnitude as the acoustic agglomeration kernel function.     

Preparation and characterization of a novel microcapsule-type latent curing agent for epoxy resin

A novel spherical latent curing agent microcapsule with the diameter ranging from 6 to 30 μm has been prepared by encapsulating butyl glycidyl ether modified 2-ethyl-4-methyl imidazole (BGE-M-2E4MZ) with polyetherimide (PEI) as the shell material through emulsion/solvent evaporation method. The microcapsule-type latent curing agent was characterized by a Fourier transformation infrared spectrometer, an optical microscope, and an environmental scanning electron microscope. The optimal parameters were obtained through experiments, and the influences of different process parameters on the formation of microcapsules were studied. When the prepared microcapsule-type latent curing agent was mixed with epoxy resin, there were few curing reactions occurred after storage for 100 days at 25 °C, however this latent curing agent could be released and curing reaction of the epoxy resin could be finished within 3 h at 100 °C. In the process of curing, this agent could not be released uniformly in the resin due to the restriction of microcapsule shell, so the resin could not be cured 100%, causing a sharp decrease of mechanical properties of E-51/Mic-2E4MZ casting.     

Sol–gel auto-combustion synthesis of PVP/CoFe2O4 nanocomposite and its magnetic characterization

Poly(vinyl pyrrolidone)/CoFe₂O₄ nanocomposite has been fabricated by a sol–gel auto-combustion method. Poly(vinyl pyrrolidone) was used as a reducing agent as well as a surface capping agent to prevent particle aggregation and stabilize the particles. The average crystallite size estimated from X-ray line profile fitting was found to be 20 ± 7 nm. The high field irreversibility and unsaturated magnetization behaviours indicate the presence of the core–shell structure in the sample. The exchange bias effect observed at 10 K suggests the existence of the magnetically aligned core surrounded by spin-disordered surface layer. The reduced remanent magnetization value of 0.6 at 10 K (higher than the theoretical value of 0.5) shows the PVP/CoFe₂O₄ nanocomposite to have cubic magnetocrystalline anisotropy according to the Stoner–Wohlfarth model.