Polyurea microcapsules with a photocleavable shell : UV-triggered release

We report the preparation and characterization of photocleavable polyurea microcapsules. First, an isocyanate end functionalized oligomer, bearing the photolabile 6-nitroveratroyloxycarbonyl group was synthesized. This oligomer, in combination with diethylenetriamine, was then utilized in the preparation of polyurea microcapsules. Polyurea microcapsules (50-300 mm) loaded with a hydrophobic dye solution and consisting of a dense capsule shell were prepared via an interfacial polymerization in a stable oil-in-water emulsion system. Thanks to the intra-molecular photocleavage mechanism, the UV-triggered rupture of the photocleavable capsule shell occurred both in the solution and in the solid state, leading to the successful release of the encapsulated liquid core

Redox-responsive degradable PEG cryogels as potential cell scaffolds in tissue engineering

A Michael addition strategy involving the reaction between a maleimide double bond and amine groups is investigated for the synthesis of cryogels at subzero temperature. Low-molecular-weight PEG-based building blocks with amine end groups and disulfide-containing building blocks with maleimide end groups are combined to synthesize redox-responsive PEG cryogels. The cryogels exhibit an interconnected macroporous morphology, a high compressive modulus and gelation yields of around 95%. While the cryogels are stable under physiological conditions, complete dissolution of the cryogels into water-soluble products is obtained in the presence of a reducing agent (glutathione) in the medium. Cell seeding experiments and toxicologic analysis demonstrate their potential as scaffolds in tissue engineerin

In situ measurement of humidity induced changes in the refractive index and thickness of polyethylene glycol thin films

6th International Conference on PhotonicsHumidity induced changes in the refractive index and thickness of polyethylene glycol (PEG) thin films are in situ determined by optical waveguide spectroscopy. PEG brushes are covalently attached to the surface of a thin gold film on a borosilicate crown glass (BK7) using a grafting-from chemical synthesis technique. The measurements are carried out in an attenuated total internal reflection setup. At low humidity levels, both the refractive index and the thickness change gradually due to swelling of the PEG thin films upon water intake. At around 80% relative humidity, a steep decrease in the refractive index and a steep increase in the thickness are observed as a result of a phase change from a semicrystalline state to a physical gel state. The hydrogenation of PEG films causes a less pronounced phase change from a semicrystalline state to a gel state. Due to fewer ether oxygen atoms available for the water molecules to make hydrogen bonding, the polymer has a more stable structure than before and the phase change is observed to shift to higher humidity levels. It is discussed that such a humidity induced change in the index of refraction can be utilized in constructing of a PEG based humidity sensor.Czech & Slovak Soc Photonc; Act M Agcy; Czech Tech Univ; Acad Sci Czech Republic; Slovak Acad Sci; Meopta Prerov; SPIE; SPIE Europe; European Opt Soc; Opt Soc Ame

Cryogels and polymeric microcapsules with triggered degradation and release

The developments in polymeric systems containing cleavable functional groups attract much attention nowadays and serve to the design of modern materials for a wide range of applications in different disciplines ranging from medicine and biotechnology to the microelectronic industry and to the protection of the environment from plastic waste. This thesis contributes to these developments with two different polymeric systems. More specifically, both cryogels and polymeric capsules have been investigated with a main attention to their on-demand degradation mechanism. The presence of cleavable functional groups in the above mentioned systems gives the advantage of either a triggered degradation or release process in accordance with the final application. In these systems, the degradation or release process can be initiated by manipulating the splitting of the cleavable groups in their structure. In the case of cryogels, the triggered degradation of the cleavable groups causes the solubilization of the crosslinked gel system. The presence of such cleavable groups can also be used to have a spatial control in order to achieve a tailored degradation mechanism. In microcapsules, the same process destroys the microcapsule shell, liberating the encapsulated material