A naturally occurring photosensitizer Curcumin (Cur) has already shown good in vitro bacterial phototoxicity.[1,2] However, low aqueous solubility and poor photolytic and hydrolytic stability limit the therapeutic application of Cur in antibacterial photodynamic therapy (aPDT). The concept of supersaturation was explored for enhancing the photodynamic effect of Cur. A supersaturated solution of Cur has already demonstrated phototoxic effect towards bacteria.[2] However, to be useful in the clinical practice the supersaturated solution should have a well-defined and sufficient concentration of active ingredient and maintain physical and chemical stability over the relevant time period. Cur was formulated as a solid dispersion (SD) intended for ex tempore preparation of a supersaturated solution. Due to 113 the transformation of crystalline Cur to amorphous form the desired concentration of Cur could be achieved upon rehydration of SD. The presence of appropriate excipients secured temporal stabilization of the metastable supersaturated solution. A series of SDs with different combinations and ratios of excipients were prepared and studied. UV-Vis spectroscopy was used to examine the extent of supersaturation; HPLC was applied in studies of chemical stability of Cur in the preparations. Finally, a SD with optimal properties was selected for further studies on aPDT effect on bacteria.

[1] Haukvik T, Bruzell E, Kristensen S, Tønnesen HH. Photokilling of bacteria by curcumin in different aqueous preparations. Pharmazie. 64 (2009):666-73.
[2] Hegge AB, Nielsen TT, Larsen KL, Bruzell E, Tønnesen HH. Impact of curcumin supersaturation in antibacterial photodynamic therapy (aPDT) – Effect of cyclodextrin type and amount. J Pharm Sci. 101 (2011):1524-1527

Ex tempore prepared superstaurated solutions of curcumin intended for aPDT
Vukicevic M, Hegge AB, Tønnesen HH, Bruzell E.
15th Congress of the European Society for Photobiology, Liège, Belgium, 2-6 September 2013 (A)