Fabrication of novel anisotropic magnetic microparticles

We report a novel technique for fabrication of magnetically anisotropic microparticles based on “arresting” of the alignment of oleic acid coated magnetite nanoparticles (OCMNs) dispersed within the oil drops of a polymerisable oil-in-water emulsion. This was achieved by polymerising the oil drops after gelling the continuous aqueous phase in the presence of an external magnetic field. This approach allowed us to produce magnetic Janus particles with anisotropic optical and magnetic properties which form unusual zig-zag chains and structures when exposed to an external magnetic field. We studied the magnetic properties of these novel microparticles and showed that they retained remanence magnetisation with high coercivity values indicative of ferromagnetic behaviour. This indicates that the composite polymeric Janus microparticles posses a net magnetic dipole and behave like micromagnets due to the “arrested” orientation of the OCMNs in their polymeric matrix. Utilizing the same technique, magnetic Janus microparticles have been prepared based on emulsions stabilised only by OCMNs without the use of surfactants, and the effect of pH of continuous aqueous phase on the morphology of these microparticles has been investigated

Particle stabilised emulsions studied by WETSEM technique

We have developed a new simple method to study the interfacial structure of particle stabilised emulsions in situ by wet scanning electron microscopy (WETSEM) technique for the first time. Particle layer(s), particle location, aggregation and bridging interaction were clearly observed with very high resolution in a range of solid particle stabilised emulsions

Encapsulation of living cells into sporopollenin microcapsules

We demonstrate that living cells can be encapsulated inside sporopollenin microcapsules derived from Lycopodium clavatum. To encapsulate large objects like cells, the sporopollenin particles are compressed into a pellet which forces their trilite scars to open up. Our method involves exposing a sporopollenin pellet to an aqueous suspension of cells in the presence of a surface active agent which facilitates the capillary suction of the cells suspension inside the compressed sporopollenin and its “re-inflating” and closure of trilite scars. We demonstrate that the viability of the cells is preserved after the encapsulation in the sporopollenin capsules which contain a significant amount of entrapped cells and show biological activity when placed into a culture medium. Since the sporopollenin nanopores allow nutrient transport across the capsule wall, it could be used for controlling the rate of in situfermentation reactions or as bio-reactors. We also show that sporopollenin can be loaded with magnetic nanoparticles and live cultures simultaneously which would allow remote manipulation, fixation, removal or potentially targeted delivery of such bio-microreactors. The encapsulation of living cells inside sporopollenin can be used for many different purposes in the food and pharmaceutical industries, including protection of probiotics in foods and delivery of live vaccines for pharmaceutical applications

SUSTAINED IN VITRO AND IN VIVO DELIVERY OF METFORMIN FROM PLANT POLLEN-DERIVED COMPOSITE MICROCAPSULES

We developed a dual microencapsulation platform for the type 2 diabetes drug metformin (MTF), which is aimed to increase its bioavailability. We report the use of Lycopodium clavatum sporopollenin (LCS), derived from their natural spores, and raw Phoenix dactylifera L. (date palm) pollens (DPP) for MTF microencapsulation. MTF was loaded into LCS and DPP via a vacuum and a novel method of hydration-induced swelling. The loading capacity (LC) and encapsulation efficiency (EE) percentages for MTF-loaded LCS and MTF-loaded DPP microcapsules were 14.9% ± 0.7, 29.8 ± 0.8, and 15.2% ± 0.7, 30.3 ± 1.0, respectively. The release of MTF from MTF-loaded LCS microcapsules was additionally controlled by re-encapsulating the loaded microcapsules into calcium alginate (ALG) microbeads via ionotropic gelation, where the release of MTF was found to be significantly slower and pH-dependent. The pharmacokinetic parameters, obtained from the in vivo study, revealed that the relative bioavailability of the MTF-loaded LCS-ALG beads was 1.215 times higher compared to pure MTF, following oral administration of a single dose equivalent to 25 mg/kg body weight MTF to streptozotocin (STZ)-induced diabetic male Sprague-Dawley rats. Significant hypoglycemic effect was obtained for STZ-induced diabetic rats orally treated with MTF-loaded LCS-ALG beads compared to control diabetic rats. Over a period of 29 days, the STZ-induced diabetic rats treated with MTF-loaded LCS-ALG beads showed a decrease in the aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglycerides, cholesterol, and low-density lipoprotein-cholesterol (LDL-C) levels, as well as an increase in glutathione peroxidase (GPx) and a recovery in the oxidative stress biomarker, lipid peroxidation (LPx). In addition, histopathological studies of liver, pancreas, kidney, and testes suggested that MTF-loaded LCS-ALG beads improved the degenerative changes in organs of diabetic rats. The LCS-ALG platform for dual encapsulation of MTF achieved sustained MTF delivery and enhancement of bioavailability, as well as the improved biochemical and histopathological characteristics in in vivo studies, opening many other intriguing applications in sustained drug deliver

Strained arrays of colloidal nanoparticles: Conductance and magnetoresistance enhancement

Colloidal nanoparticles are very popular as building blocks of functional arrays for electronic and optical applications. However, there is a problem in achieving electrical conductivity in such nanoarrays due to their molecular shells. These shells, which are inherent to colloidal particles, physically separate the nanoparticles in an array and act as very effective insulators. Post-assembly thinning of the shells is therefore required to enhance the array conductivity to a sensible value. Here, we introduce a conceptually new approach to the thinning, using compressive stress applied to the array by the supporting matrix. The stress arises from polymerization-induced shrinkage of the matrix as an integral step during device assembly. Using arrays of oleic-acid-covered magnetite nanoparticles in conjunction with an HDDA-polymer (HDDA: 1,6-hexanediol diacrylate) matrix, we have achieved a significant steady current in the array along with an unprecedented value of the magnetoresistance. Our results serve as a proof-of-concept for other colloidal nanoparticles