Benign preparation of aqueous core poly lactic-co-glycolic acid (PLGA) microcapsules.

Poly lactic-co-glycolic acid (PLGA) has attracted considerable attention as a polymer for drug delivery carriers. However, the hydrophobic property of PLGA often leads to the use of harmful organic solvents and poor encapsulation efficiency of hydrophilic materials. To our knowledge, a preparation method of aqueous core PLGA microcapsules without using harmful organic solvents has not been proposed. In this study, we attempted to establish an encapsulation technique of hydrophilic materials in aqueous core biodegradable and biocompatible PLGA microcapsules using vegetable oil as a continuous phase. As a result, the temperature of the oil/water mixture was required to be above the glass transition temperature. In this condition, two different types of morphology were prepared. When the water volume was below the solubility limit, PLGA microcapsules with a smooth shell were formed. In contrast, when the water volume was above the solubility limit, colloidosome-like microcapsules with PLGA nanoparticles assembled at the interface were formed. The obtained microcapsules were then heated at the glass transition temperature. The result is that aqueous core PLGA microcapsules with a smooth shell were prepared using plant oil as a continuous phase. Rhodamine B used as a hydrophilic model encapsulant, was successfully encapsulated in the PLGA microcapsules

Elimination of Coffee-Ring Formation by Humidity Cycling: A Numerical Study.

Periodically switching between evaporation and condensation, or "humidity cycling", has potential for controlling the film shape that results from volatile droplets containing a nonvolatile material. It does not require adaptation of material properties nor the introduction of an external field to achieve a change in film shape. It was shown experimentally by Doi and coworkers [Kajiya et al. Langmuir 2010, 26, pp 10429-10432] that ring-shaped deposits can be removed through careful selection of the atmospheric conditions. We present a model, based on lubrication theory, that can predict the final film shape resulting from the humidity cycling process. We confirm that the refluidization of gelled regions during condensation and the subsequent inward flow is the mechanism responsible for the improved profiles. Furthermore, we find that an increase in the time spent condensing to that spent evaporating results in flatter films and that an optimal humidity cycling frequency exists.This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acs.langmuir.5b0382

Colloidal buckets formed via internal phase separation

We report the fabrication of novel hollow particles, with a hole engineered in the shell, via a coacervation technique. These particles are termed colloidal buckets. Two sets of conditions were explored: (i) lowering the operating temperature to reduce the solvent evaporation rate, and (ii) incorporation of a third component to alter the interfacial tensions between different phases. The particles were characterised by dynamic light scattering, gas adsorption and differential scanning calorimetry. The buckets had a higher surface area than spheres of the same size and the core was easily removed by washing in a suitable solvent

Release Profiles of Encapsulated Actives from Colloidosomes Sintered for Various Durations

This paper presents the formation of low temperature colloidosomes from colloidal poly(styrene-co-butyl acrylate) particles for both water-in-oil and oil-in-water systems. An investigation into the sintering conditions examines the ultimate shell morphology formed, with longer sintering times and higher sintering temperatures producing less porous microcapsules. This has been verified by the release of an encapsulated dye from the aqueous core microcapsules, in which slower release has been detected for longer sintering times. The results are subsequently fitted with a diffusion equation to give a diffusion coefficient of fluorescein through the polymeric shell of 10−17 m2/s

Salt-driven assembly of magnetic silica microbeads with tunable porosity.

HYPOTHESIS: Porous magnetic silica beads are promising materials for biological and environmental applications due to their enhanced adsorption and ease of recovery. This work aims to develop a new, inexpensive and environmentally friendly approach based on agglomeration of nanoparticles in aqueous droplets. The use of an emulsion as a geometrical constraint is expected to result in the formation of spherical beads with tunable composition depending on the aqueous phase content. EXPERIMENTS: Magnetic silica beads are produced at room temperature by colloidal destabilization induced by addition of CaCl2 to a water-in-oil emulsion containing SiO2 and Fe3O4 nanoparticles. The impact of the salt concentration, emulsification method, concentration of hydrophobic surfactant as well as silica content is presented in this paper. FINDINGS: This method enables the production of spherical beads with diameters between 1 and 9 µm. The incorporation of magnetic nanoparticles inside the bead's structure is confirmed using Energy Dispersive X-ray spectrometry (EDX) and Scanning Transmission Electron Microscopy (STEM) and results in the production of magnetic responsive beads with a preparation yield up to 84%. By incorporating the surfactant Span 80 in the oil phase it is possible to tune the roughness and porosity of the beads.W D Armstrong Studentship (internal Cambridge award

Silver-Coated Colloidosomes as Carriers for an Anticancer Drug.

Small drug molecules are widely developed and used in the pharmaceutical industry. In the past few years, loading and delivering such molecules using polymer-shell colloidosomes has attracted interest. Traditional polymer capsules fail to encapsulate low-molecular-weight materials for long times, since they are inherently porous and permeable for small molecules. In this paper, we report a method for encapsulating an anticancer drug with small molecule weight, for cell viability tests. The silver-coated colloidosomes are prepared by making an aqueous core capsule with a polymer shell and then adding AgNO3, surfactant, and l-ascorbic acid to form a second shell. The capsules are impermeable and can be triggered using ultrasound. We propose to use the capsules as drug carriers. The silver demonstrates a low cytotoxicity for up to 10 capsules per cell. After the silver shells are triggered by ultrasound, the released doxorubicin, the broken silver fragments, and the doxorubicin loading on the capsule surface all kill cells. The results demonstrate a nonpermeable silver-shell microcapsule with ultrasound sensitivity for potential medical applications

Filling of three-dimensional space by two-dimensional sheet growth.

Models of three-dimensional space filling based on growth of two-dimensional sheets are proposed. Beginning from planar Eden-style growth of sheets, additional growth modes are introduced. These enable the sheets to form layered or disordered structures. The growth modes can also be combined. An off-lattice kinetic Monte Carlo-based computer algorithm is presented and used to study the kinetics of the new models and the resulting structures. It is possible to study space filling by two-dimensional growth in a three-dimensional domain with arbitrarily oriented sheets; the results agree with previously published models where the sheets are only able to grow in a limited set of directions. The introduction of a bifurcation mechanism gives rise to complex disordered structures that are of interest as model structures for the mesostructure of calcium silicate hydrate in hardened cement paste.This research was supported by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement 264448. AFR was supported by EPSRC grant EP/H035397/1.This is the author accepted manuscript. The final version is available from APS via http://dx.doi.org/10.1103/PhysRevE.92.04210

Online Data Condensation for Digitalised Biopharmaceutical Processes

Efficient control of a bioprocess relies on the ability to systematically capture and represent the process dynamics of critical process parameters. Multivariate monitoring techniques in biopharmaceuticals has resulted in the generation of large amounts of data comprising real-time measurements of critical quality and performance attributes. If exploited efficiently, these can provide an opportunity for developing better control action. For this, it is important to have a comprehensive view of the critical process parameter landscape, which can only be achieved by integrating both online and offline data into a single data matrix that can then be subjected to standard data analysis protocols. However, owing to the difference in the number of readings available for variables recorded online and offline, there is a need for new methods to achieve condensation capability. This paper introduces a novel methodology for condensing online data into an offline data matrix, which performed better when compared to traditionally employed averaging and helped increase the number of variables available for representing the design space of the process. The method was also used to understand how error propagates through online data, so as to identify an interval of tolerance in online monitoring of bioprocesses

Pattern formation in drying blood drops

Funder: Australian Government Research Training Program (RTP) Scholarship.Funder: HaemokinesisPatterns in dried droplets are commonly observed as rings left after spills of dirty water or coffee have evaporated. Patterns are also seen in dried blood droplets and the patterns have been shown to differ from patients afflicted with different medical conditions. This has been proposed as the basis for a new generation of low-cost blood diagnostics. Before these diagnostics can be widely used, the underlying mechanisms leading to pattern formation in these systems must be understood. We analyse the height profile and appearance of dispersions prepared with red blood cells (RBCs) from healthy donors. The red cell concentrations and diluent were varied and compared with simple polystyrene particle systems to identify the dominant mechanistic variables. Typically, a high concentration of non-volatile components suppresses ring formation. However, RBC suspensions display a greater volume of edge deposition when the red cell concentration is higher. This discrepancy is caused by the consolidation front halting during drying for most blood suspensions. This prevents the standard horizontal drying mechanism and leads to two clearly defined regions in final crack patterns and height profile. This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’