Hypericin fluorescence kinetics in the presence of low density lipoproteins: study on quail CAM assay for topical delivery.

There has been increasing interest in fluorescence-based imaging techniques in clinical practice, with the aim to detect and visualize the tumour configuration and the border with healthy tissue. Strong photodynamic activity of hypericin (Hyp) can be improved by various molecular transport systems (e.g. LDL). Our aim was to examine pharmacokinetics of Hyp in the presence of LDL particles on ex ovo chorioallantoic membrane (CAM) of Japanese quail with implanted TE1 tumour spheroids (human squamocellular carcinoma). Spheroids were implanted on CAM surface on embryonal day 7 and after 24 hours formulations of free Hyp and Hyp:LDL 100:1 and 200:1 were topically applied. All experimental formulations in the fluorescent image very well visualized the tumour spheroid position, with gradual increase of fluorescence intensity in 6-h observation period. LDL transportation system exhibited clear superiority in fluorescence pharmacokinetics than free Hyp formulation by increasing tumour-normal difference. Our experimental results confirm that Hyp and Hyp:LDL complex is potent fluorophore for photodynamic diagnosis of squamocellular carcinoma.