Immunotargeted photodynamic therapy for cholesteatoma: in vitro results with anti-EGFR-coated indocyanine green nanocapsules.

Michael B Gluth, Yihong C Kaufmann, John L Dornhoffer, Scott Ferguson

Index: Otol. Neurotol. 36(1) , 76-81, (2014)

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Abstract

The objective was to test the hypothesis that immunotargeted photodynamic therapy (IT-PDT) using anti-epithelial growth factor receptor (EGFR)-coated indocyanine green (ICG) nanocapsules would selectively kill cholesteatoma-derived keratinocytes while sparing middle ear-derived mucosa cells in vitro.Rates of residual cholesteatoma caused by incomplete microsurgical removal are unacceptably high; thus, development of an adjuvant therapy to safely destroy undetected residual cholesteatoma cells would be desirable. IT-PDT is a possible means to achieve this end.ICG nanocapsules coated with anti-EGFR were synthesized and applied to cholesteatoma-derived keratinocytes and middle ear mucosa cells in vitro. Selective binding to keratinocytes was evaluated by fluorescence microscopy. Activation of ICG was undertaken by applying near-infrared light (810 nm) at an applied energy dose of 1,080 J/cm. Cell death was evaluated 2 hours after treatment with trypan blue staining.Selective and robust nanocapsule binding to keratinocytes, but not mucosa cells, was confirmed by preapplication and postapplication fluorescence measurements. A keratinocyte cell death rate of 70.12% ± 2.50% was achieved, whereas negligible mucosa cell death was observed. Negligible cell death was also observed for both cell types with application of the nanocapsules alone or with application of near-infrared light alone.Anti-EGFR ICG nanocapsules applied topically and activated as part of an IT-PDT scheme results in a high rate of cholesteatoma-derived keratinocyte cell death while negligibly affecting middle ear mucosal cells in vitro. These preliminary findings suggest that this is a feasible concept and that further investigation is warranted.