Dennis M. Vriezema

Polymeric Microcapsules for Synthetic Applications

For decades scientists have been working on closed systems for transportation, catalysis and protection, which are inspired by natural cells. Only recently polymer based systems have emerged for these systems, since they are more robust, give protection from the environment and give a more stable membrane. Various methods have been developed to prepare polymer based capsules. They can be made by self-assembly, templating, in situ polymerization or precipitation. Their application has been explored in various areas e.g. drug delivery, diagnostics, sensors and nano reactors. Considering the output in this field has substantially grown, more developments can be expected from this latter application.

Biodegradable polymeric microcapsules for selective ultrasound-triggered drug release

A series of hollow biodegradable polymeric microcapsules were prepared, of which their susceptibility to ultrasound was used for triggered release. High speed imaging of the ultrasound experiments showed a strong correlation between the acoustic pressure needed to activate these microcapsules and their shell thickness to diameter ratio. Based on this information a selective triggering of capsules with two different shell thickness to diameter ratios was successfully performed. The capsules were mixed in a single system and were activated independently from each other by a differentiation in acoustic pressure levels. This application is of great interest in the field of drug delivery, since this system allows for localized multiple drug releases in a selective fashion.

Preparation of Biodegradable Liquid Core PLLA Microcapsules and Hollow PLLA Microcapsules Using Microfluidics

Biodegradable PLLA capsules with a narrow size distribution were prepared using a microfluidics platform. With this technique, an oil-in-water emulsion was produced in which the polymer, a hydrophobic non-volatile non-solvent and a hydrophobic model drug were dissolved in the organic phase. The polymer precipitated at the droplet interface, yielding a drug deliverable microcapsule of which the release of this model drug was investigated. These capsules with an organic phase in the core were also used to prepare hollow particles by conveniently removing the core phase by lyophilization. Optimal conditions for the preparation of biodegradable capsules were found with respect to the flow rate of the continuous phase and the molecular weight of the PLLA polymer. This approach of preparing biodegradable capsules is of potential interest for the field of drug delivery.