35^th Australasian Polymer Symposium, Gold Coast, Queensland, Australia.

Fluorine-19 has become a nuclei of interest for MRI due to a 100% natural abundance, zero background in vivo, and a high nuclear magnetic resonance sensitivity. Its poor sensitivity in vivo, however; is a main hurdle for its effective use in clinical systems requiring highly fluorinated species to obtain a signal. Hyperbranched polymers provide a biocompatible and customisable platform for selectively localising polyfluorinated ¹⁹F-MRI agents and have been shown to be successful in a myriad of applications, both by us1 and others². The use of gadolinium for contrast enhancement has also been shown to significantly shorten the T1 and T2 relaxation times of not only ¹H but ¹⁹F nuclei as well.^2–4 By combining these two techniques we report a gadolinium enhanced polyfluorinated stimuli responsive hyperbranched polymer capable of changing its ¹⁹F and ¹H contrast upon action by external stimuli. To test this method a disulphide bond was utilized as it is well known to cleave in the presence of glutathione, an antioxidant upregulated in tumour cells. Upon release of the DOTA-Gd complex the 19F-MR signal intensity increases, thus creating an on/off switch that is dependent upon successful tumour cell internalization.

References:
1 Thurecht, K. J.; Blakey, I.; Peng, H.; Squires, O.; Hsu, S.; Alexander, C.; Whittaker, A. K. J. Am. Chem. Soc. 2010, 132, 5336–5337.
2 Li, Y.; Laurent, S.; Esser, L.; Elst, L. Vander; Muller, R. N.; Lowe, A. B.; Boyer, C.; Davis, T. P. Polym. Chem. 2014, 5, 2592.
3 De Vries, A.; Moonen, R.; Yildirim, M.; Langereis, S.; Lamerichs, R.; Pikkemaat, J. a; Baroni, S.; Terreno, E.; Nicolay, K.; Strijkers, G. J.; Grüll, H. Contrast Media Mol. Imaging 2014, 9, 83–91.
4 Ratner, a V; Quay, S.; Muller, H. H.; Simpson, B. B.; Hurd, R.; Young, S. W. 19F relaxation rate enhancement and frequency shift with Gd-DTPA. Investigative radiology, 1989, 24, 224–227.