Poly(N-isopropylacrylamide)-coated thermo-responsive nanoparticles for controlled delivery of sulfonated Zn-phthalocyanine in Chinese hamster ovary cells in vitro and zebra fish in vivo

Poly( N- isopropylacrylamide) ( PNIPAM)- coated Fe3O4@ SiO2@ CdTe multifunctional nanoparticles with photoluminescent ( PL), thermosensitive and magnetic properties, were investigated as carriers to deliver water- soluble, fluorescent sulfonated Zn- phthalocyanine ( ZnPcS), a photosensitizing drug for photodynamic therapy of cancer, in Chinese hamster ovary ( CHO) cells in vitro and zebra fish in vivo. PNIPAM is a well- known thermo- responsive polymer with a volume phase transition temperature. This property allows it to be swollen in water at temperatures lower than 32 - 34 degrees C to take up ZnPcS and shrunken to expel the drug at higher temperatures. Since the PL band of CdTe quantum dots ( QDs) as indicators for the nanoparticles is at 585 nm and the emission band of ZnPcS is at 680 nm, it is possible to study the temperature- dependent release of ZnPcS from the nanoparticles by fluorescence measurements. ZnPcS was embedded in the PNIPAM of the nanoparticles at 25 degrees C in phosphate buffered saline ( PBS) solution and released at 37 degrees C, measured with a spectrophotometer. When CHO cells had been incubated with the ZnPcS- loaded nanoparticles at 27 degrees C, a similar intracellular localization pattern of CdTe QDs and ZnPcS was seen by multichannel measurements in confocal laser scanning microscopy ( CLSM), but a diffuse pattern of only ZnPcS fluorescence was detected in the cytoplasm of the cells at 37 degrees C, indicating a release of ZnPcS from the nanoparticles. Similar results were also found in the intestinal tract of zebra fish in vivo after intake of the nanoparticles. Since the nanoparticles contain magnetic ( Fe3O4) material, the nanoparticles could also be manipulated to change their location in the intestinal tract of the zebra fish with an external magnetic field gradient of 300 G mm(-1). The results presented suggest that such multifunctional nanoparticles may have combined potential for temperature- dependent drug delivery, QD photodetection and magnetic manipulation in diagnosis and therapy of diseases.