Authors:H. Mimura, H. Hoshi, K. Akiba and Y. Onodera
Microcapsules enclosing an extractant with strong affinity for Am were prepared by employing a biopolymer gel as an immobilization matrix. A relatively large separation factor between Am and Eu was exhibited by the microcapsule containing of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301, HA) and alginic acid (HALG). The chromatographic separation of these metal ions was accomplished by gradient elution through the column packed with HA-HALG.
The uptake behavior of Pu(IV) has been investigated by using calcium alginate gel polymer (CaALG) and TBP microcapsules (TBP-CaALG).
The characterization of CaALG and TBP-CaALG was examined by SEM and IR, and the uptake properties and distribution of Pu(IV)
ions were estimated by batch method. The uptake rate of Pu(IV) on CaALG and TBP-CaALG in the presence of 5 M HNO3 was attained within 6 and 4 h, respectively, and Kd values for CaALG and TBP-CaALG after 7 h-shaking were 50.2 and 53.2 cm3/g, respectively. Relatively large Kd values (90.3–425 cm3/g) were obtained for fresh CaALG and TBP-CaALG in the presence of 0.5–2 M HNO3. Thus CaALG and TBP-CaALG are effective for the separation of Pu(IV) in the presence of highly concentrated HNO3.
Authors:L. Zane Miller, Jeremy L. Steinbacher, Tania I. Houjeiry, Ashley R. Longstreet, Kendra L. Woodberry, B. Frank Gupton, Banghao Chen, Ron Clark and D. Tyler McQuade
Monodisperse silica microcapsules are typically fabricated using hard templating methods. Though soft templating methods are known, none yet provides a fast and easy method to produce monodisperse capsules. Herein, we describe a mesofluidic strategy whereby monodisperse droplets of reactive silica precursors are formed using a snap-off mechanism via a T junction. Both the mesofluidic system and the composition of the reactive silica formulation are critical features. Using solid- and solution-state 29Si nuclear magnetic resonance, scanning electron microscopy, and optical microscopy, we have developed models for why some formulations form exploding capsules, why some capsules contain crystalline materials, and why some capsules have thin or thick walls.
Authors:L. Zane Miller, James J. Rutowski, Jonathan A. Binns, Guillermo Orts-Gil, D. Tyler McQuade and Jeremy L. Steinbacher
We present a rapid approach for forming monodisperse silica microcapsules decorated with metal oxide nanoparticles; the silica–metal oxide composites have a hierarchical architecture and a range of compositions. The details of the method were defined using titania precursors. Silica capsules containing low concentrations of titania (<1 wt. %) were produced via an interfacial reaction using a simple mesofluidic T-junction droplet generator. Increasing the titania content of the capsules was achieved using two related, flow-based postsynthetic approaches. In the first approach, a precursor solution containing titanium alkoxides was flowed through a packed-bed of capsules. The second approach provided the highest concentration of titania (3.5 wt. %) and was achieved by evaporating titanium precursor solutions onto a capsule packed-bed using air flow to accelerate evaporation. Decorated capsules, regardless of the method, were annealed to improve the titania crystallinity and analyzed by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic properties were then compared to a commercial nanoparticulate titania, which the microcapsule-supported titania outperformed in terms of rate of degradation of an organic dye and recyclability. Finally, the generality of the flow-based surface decoration procedures was demonstrated by synthesizing several composite transition metal oxide–silica microparticle materials.
Authors:G.W. Shu, D.L. Ma, H. Chen, J.P. Meng, Y. Wang and N. Xin
The present study was to evaluate the survival rate of free and encapsulated Bifidobacterium bifidum BB28 under simulated gastrointestinal conditions and its stability during storage. Results showed that non-microencapsulated Bifidobacterium bifidum BB28 was more susceptible to simulated gastrointestinal conditions than microencapsulated bacteria. Microencapsulated Bifidobacterium BB28 exhibited a lower population reduction than free cells during exposure to simulated gastrointestinal conditions, the viable count of monolayer microcapsules, double layer microcapsules, and triple layer microcapsules decreased by nine magnitudes, four magnitudes, and one magnitude after 2 h, respectively. The enteric test showed that the microorganism cells were released from the monolayer, double layer, and triple layer microcapsules completely in 40 min. Moreover, the optimum storage times of free Bifidobacterium BB28, monolayer microcapsules, double layer microcapsules, and triple layer microcapsules were 21 days, 21 days, 28 days, and more than 35 days in orange juice, pure milk, and nutrition Express (a commercially available milk based drink), and the viable counts were maintained at 1×106 CFU g−1 or more, which means that the double layer and triple layer of microcapsules of B. bifidum BB28 have great potential in food application.
Authors:Alfonso Gañán-Calvo, Elena Castro-Hernández, María Flores-Mosquera and Lucía Martín-Banderas
Massive, nearly monodisperse, true microencapsulation of a wide variety of active ingredients within biocompatible shells can be achieved using flow focusing at moderate-high Reynolds numbers, a paradigmatic tool for highly controlled flow chemistry processes whose flexibility and physical aspects are briefly illustrated here. We show that the natural, regular capillary breakup of a laminar high-speed microjet produced by gentle mechanical means alone allows the production of true microcapsules with controlled dimensions. The process versatility is shown in a variety of examples including encapsulation of different materials as proteins and/or microorganisms in biocompatible polymers as poly-l-glutamic acid (PLGA). Microcapsules produced show nearly homogeneous size, well-centered core, and their size and structure are well predicted by simple theoretical models.
Authors:Barbara Bellich, Massimiliano Borgogna, Damiano Carnio and Attilio Cesàro
Alginate has been established as a very versatile material in the preparation of hydrogel capsules for trapping therapeutic
biomolecules and cells. The physico-chemical properties, the mechanism and the processing of gel formation are now well established.
In the frame of a project aiming at the exploitation of encapsulation of therapeutic proteins in alginate gel particles, the
procedure of preparation, characterization, gel-drying and re-hydrating has been explored for the shelf-life of the encapsulated
biomolecules. Here, the results of a calorimetric study on the freezing and dehydration process of alginate micro-capsules
is presented. The work aims at the description of water state(s) and its removal under “controlled conditions” in the presence
of bioprotectant sugars.
Authors:Jeremy L. Steinbacher, Yankai Lui, Brian P. Mason, William L. Olbricht and D. Tyler McQuade
We present and validate simple mesofluidic devices for producing monodisperse droplets and materials. The significance of this work is a demonstration that simple and complex droplet formulations can be prepared uniformly using off-the-shelf small-diameter tubing, barbed tubing adapters, and needles. With these simple tools, multiple droplet-forming devices and a new particle concentrator were produced and validated. We demonstrate that the droplet-forming devices could produce low-dispersity particles from 25 to 1200 Km and that these results are similar to results from more complicated devices. Through a study of the fluid dynamics and a dimensional analysis of the data, we have correlated droplet size with two dimensionless groups, capillary number and viscosity ratio. The flowfocusing device is more sensitive to both parameters than the T-junction geometry. The modular character of our mesofluidic devices allowed us to rapidly assemble compound devices that use flow-focusing and T-junction devices in series to create complex droplet-in-microcapsule materials. This work demonstrates that flow chemistry does not require complicated tools, and an inexpensive tool-kit can allow anyone with interest to enter the field.