Hypericin-bearing magnetic iron oxide nanoparticles for selective drug delivery in photodynamic therapy.

Combining the concept of magnetic drug targeting and photodynamic therapy is a promising approach for the treatment of cancer. A high selectivity as well as significant fewer side effects can be achieved by this method, since the therapeutic treatment only takes place in the area where accumulation of the particles by an external electromagnet and radiation by a laser system overlap. In this article, a novel hypericin-bearing drug delivery system has been developed by synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) with a hypericin-linked functionalized dextran coating. For that, sterically stabilized dextran-coated SPIONs were produced by coprecipitation and crosslinking with epichlorohydrin to enhance stability. Carboxymethylation of the dextran shell provided a functionalized platform for linking hypericin via glutaraldehyde. Particle sizes obtained by dynamic light scattering were in a range of 55-85 nm, whereas investigation of single magnetite or maghemite particle diameter was performed by transmission electron microscopy and X-ray diffraction and resulted in approximately 4.5-5.0 nm. Surface chemistry of those particles was evaluated by Fourier transform infrared spectroscopy and ζ potential measurements, indicating successful functionalization and dispersal stabilization due to a mixture of steric and electrostatic repulsion. Flow cytometry revealed no toxicity of pure nanoparticles as well as hypericin without exposure to light on Jurkat T-cells, whereas the combination of hypericin, alone or loaded on particles, with light-induced cell death in a concentration and exposure time-dependent manner due to the generation of reactive oxygen species. In conclusion, the combination of SPIONs' targeting abilities with hypericin's phototoxic properties represents a promising approach for merging magnetic drug targeting with photodynamic therapy for the treatment of cancer.

Luminescence from Bi2+-activated alkali earth borophosphates for white LEDs.

Bi(2+)-doped MBPO(5) (M = Ba(2+), Sr(2+), Ca(2+)), synthesized in air via solid state reaction, are considered as novel orange and red phosphors for white light emitting diodes with improved colour quality. Absorption of Bi(2+) due to (2)P(1/2)-->(2)S(1/2) and (2)P(1/2)-->(2)P(3/2) could be observed and quantified. Excitation to (2)P(3/2) is accompanied by vibronic sidebands, and corresponding emission behaviour is found. The electron-phonon coupling strength increases in the order M = Ba(2+)-->Sr(2+)-->Ca(2+). In the case of MBPO(5):Bi(2+), one-, two- and even three-phonon sidebands could clearly be observed. The crystal structure of all three compounds belongs to space group P3(1)21. Bi(2+) is incorporated on M(2+) sites, and reduction of Bi(3+) to Bi(2+) occurs for reasons of charge compensation. In accordance with crystallographic data, fluorescence decay behaviour indicates that only one type of Bi(2+)-emission centers is present.