Ronghua Yu

A pH dependent thermo-sensitive copolymer drug carrier incorporating 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-NH2-TEMPO) residues for electron spin resonance (ESR) labeling

The fabrication of a new amphiphilic block copolymer composed of a poly DL-lactic acid (PLA) hydrophobic backbone and pH dependent thermo-sensitive poly (N-isopropyl) methacrylamide-co-N-isopropylmaleamic acid-co-10-undecenoic acid (PNIPAAm-co-NIPMMA-co-UA) entities as hydrophilic domains as well as carrying 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) residues for electron spin resonance (ESR) labeling is reported. The lower critical solution temperature (LCST) of the copolymer was determined by optical absorbance measurements. The LCST was pH dependent and varied in a narrow practical range, 35.4 °C at pH 5.0, 37.5 °C at pH 6.5 and 39.4 °C at pH 7.4, which was below, near and above nominal physiological temperature respectively. The assembly of the copolymer into micelles in aqueous solution at temperatures below the LCST was confirmed by FT-IR, (1)H NMR and fluorescence spectroscopy. It is demonstrated that the anticancer drug, 5-fluorouracil (5-FU) can be loaded effectively within the polymeric micelles and released in response to environmental stimuli- namely, pH and temperature.

Novel ferrocenyl nitroxide nanoparticles as electron paramagnetic resonance oximetry probes in vitro and in vivo

AIMS In this article we report our recent developments in the field of electron paramagnetic resonance oximetry. MATERIALS & METHODS Novel synthesized ferrocenyl nitroxide radicals (FcN)-1-6 were evaluated to determine their electron paramagnetic resonance oxygen responsiveness and reduction resistance. The 3-ferrocenyl-N-(oxyl-2,2,6,6-tetramethylpiperidin-4-yl) butanamide radical (FcN-6), with outstanding electron paramagnetic resonance oxygen sensitivity, was encapsulated in Pluronic F-127 polymeric nanoparticles. RESULTS The nanoparticles exhibited good oxygen sensitivity, long-term stability of responsiveness, targeting to lung, liver and tumor, and low toxicity. CONCLUSION These features make this novel nanoparticle especially valuable for mapping O₂ concentrations in the body and monitoring the oxygen level inside tissues.