Krystyna Kijewska

Photopolymerized polypyrrole microvessels.

We report on the preparation of water-filled polymer microvessels through the photopolymerization of pyrrole in a water/chloroform emulsion. The resulting structures were characterized by complementary spectroscopic and microscopic techniques, including Raman spectroscopy, XPS, SEM, and TEM. The encapsulation of fluorescent, magnetic, and ionic species within the microvessels has been demonstrated. Confocal microscopy and fluorescence anisotropy measurements revealed that the encapsulated chromophore (Rhodamine 6G) resides within voids in the capsules; however, strong interaction of the dye with polypyrrole results in a measurable decrease in its rotational dynamics. Microvessels loaded with ferrofluid exhibit magnetic properties, and their structures can be directed with an external magnetic field. TEM measurements allowed imaging of individual nanoparticles entrapped within the vessels. The application of Cu(2+)-loaded microvessels as a transducer layer in all-solid-state ion-selective electrodes was also demonstrated.

Magnetic-nanoparticle-decorated polypyrrole microvessels: toward encapsulation of mRNA cap analogues.

Many phosphorylated nucleoside derivatives have therapeutic potential, but their application is limited by problems with membrane permeability and with intracellular delivery. Here, we prepared polypyrrole microvessel structures modified with superparamagnetic nanoparticles for use as potential carriers of nucleotides. The microvessels were prepared via the photochemical polymerization of the monomer onto the surface of aqueous ferrofluidic droplets. A complementary physicochemical analysis revealed that a fraction of the nanoparticles was embedded in the microvessel walls, while the other nanoparticles were in the core of the vessel. SQUID (superconducting quantum interference device) measurements indicated that the incorporated nanoparticles retained their superparamagnetic properties; thus, the resulting nanoparticle-modified microvessels can be directed by an external magnetic field. As a result of these features, these microvessels may be useful as drug carriers in biomedical applications. To demonstrate the encapsulation of drug molecules, two labeled mRNA cap analogues, nucleotide-derived potential anticancer agents, were used. It was shown that the cap analogues are located in the aqueous core of the microvessels and can be released to the external solution by spontaneous permeation through the polymer walls. Mass spectrometry analysis confirmed that the cap analogues were preserved during encapsulation, storage, and release. This finding provides a foundation for the future development of anticancer therapies and for the delivery of nucleotide-based therapeutics.

Pyrene-loaded polypyrrole microvessels.

The encapsulation of guest molecules within polymeric hollow nano- or microscale structures is a rapidly developing field of interdisciplinary research due to a variety of applications ranging from drug delivery and sensor fabrication to nanoscale synthesis and bioinspired mineralization. We report on the encapsulation of pyrene within three-dimensional polypyrrole microvessels synthesized by precipitation polymerization of pyrrole onto toluene droplets that contain pyrene. Steady state and time-resolved fluorescence measurements show that the optical response and dynamics of encapsulated pyrene is significantly different from that in the free solution, likely due to interactions with oligomeric species generated during the polymerization process that partition into the organic core of the microvessel. Our results indicate that the encapsulation process can have a significant influence on the local environment of encapsulated species, an issue that is critical from the perspective of potential synthetic or medical applications.

Solid-core and hollow magnetic nanostructures: Synthesis, surface modifications and biological applications.

In the need of development of versatile and flexible platforms for sensing, nanostructured particles are one of the systems of choice. Additionally, the state-of-the-art, controlled surface modifications of these structures offer broad possibilities of using such systems for diagnostics and therapy, often referred to as thera(g)nostics. In this brief review we will focus on the synthesis and surface modifications of solid-core magnetic nanostructures and polymeric capsules containing nanoferrites modified with anti-cancer drug--doxorubicin, designed for magnetic field-driven drug delivery for cancer therapy. We will also outline some problems related to the usage of such structures. The encapsulation and distribution of magnetic iron oxide nanoparticles modified with doxorubicin will be demonstrated in the polypyrrole spherical microvessels.

Incorporation of pyrene in polypyrrole/polystyrene magnetic beads.

Pyrene, a fluorescent dye, was incorporated into polystyrene particles coated with polypyrrole. The incorporation was achieved by treating the polypyrrole/polystyrene (PPy/PS) beads in a tetrahydrofuran (THF) solution of the pyrene fluorophore followed by rinsing with methanol. The polystyrene cores of the beads swell in THF, allowing penetration of pyrene molecules into the polystyrene structure. The addition of methanol causes contraction of the swollen polystyrene, which encapsulates the dye molecules inside the beads. It is shown that the polypyrrole coating is permeable with respect to both the dye and the solvent, allowing the transport of molecules between the polystyrene cores and the contacting solution. The polypyrrole adlayer can be used as a matrix for the incorporation of magnetic nanoparticles. Embedded particles provide magnetic functionality to the PPy/PS beads. It is demonstrated that the pyrene-loaded beads can be manipulated with an external magnetic field.

Magnetic polymer microcapsules loaded with Nile Red fluorescent dye

Fabrication of multifunctional smart vehicles for drug delivery is a fascinating challenge of multidisciplinary research at the crossroads of materials science, physics and biology. We demonstrate a prototypical microcapsule system that is capable of encapsulating hydrophobic molecules and at the same time reveals magnetic properties. The microcapsules are prepared using a templated synthesis approach where the molecules to be encapsulated (Nile Red) are present in the organic droplets that are suspended in the polymerization solution which also contains magnetic nanoparticles. The polymer (polypyrrole) grows on the surface of organic droplets encapsulating the fluorescent dye in the core of the formed microcapsule which incorporates the nanoparticles into its wall. For characterization of the resulting structures a range of complementary physicochemical methodology is used including optical and electron microscopy, magnetometry, 1H NMR and spectroscopy in the visible and X-ray spectral ranges. Moreover, the microcapsules have been examined in biological environment in in vitro and in vivo studies.

Using Diffusion To Characterize Interfacial Heterogeneity

We report on the use of molecular diffusional motion over a range of length scales to characterize compositional heterogeneity in monolayer structures. This work focuses on the diffusional motion of perylene in two types of films supported on functionalized silica surfaces: single-component (stearic acid) and two-component (hydrocarbon/fluorocarbon) films. Langmuir-Blodgett (LB) monolayers were deposited directly on silica or were bound to surface-modified silica by means of metal ion complexation. The LB films were characterized by their π-A isotherms and by Brewster angle microscopy (BAM) during formation and deposition. Chromophore mobility and monolayer structural heterogeneity were evaluated by comparing rotational diffusion data (fluorescence anisotropy decay imaging) and translational diffusion data (fluorescence recovery after photobleaching) on the same LB films. Our results indicate that the mobility of the chromophore depends sensitively on both metal ion identity and film composition.