Developing tamoxifen-based chemical probes for use with a dual-modality fluorescence and optical coherence tomography imaging needle

Fluorescent small molecules based on the chemotherapeutic tamoxifen have been synthesised for use with an imaging needle capable of acquiring simultaneous fluorescence and optical coherence tomography (OCT) images. The chemical probes are based on the active metabolite of the drug, 4-hydroxytamoxifen that is coupled with a diamine linker to commercially available Alexa Fluor or 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes. The tamoxifen derivatives were then added to cultures of live oestrogen receptor positive MCF-7 human breast cancer cells and imaged using the miniaturised fibre-optic device enclosed within a 23-gauge needle (outer diameter 640 μm). The OCT images showed the micro-architecture of the cell culture, while the fluorescence identified oestrogen receptor positive cells. Both dyes were found to have suitable excitation and emission properties and are good candidates to further develop as probes for fluorescence-guided surgery.