Novel two-photon dyes for biomedical applications Two-photon absorption is an emerging discipline with numerous biomedical applications. The development of novel dyes with two-photon excitation properties is expected to refine and expand implementation of this photophysical process. Fundamental Research Health © Vshivkova, Shutterstock Two-photon absorption is employed in various cell biology applications including microscopic bio-imaging and photo-activated drugs, photodynamic therapy and 3D microfabrication of biomedical devices. Apart from specifically tailored dyes responsive to two-photon excitation, two-photon absorption also requires the use of optimised optical sources and instrumentation. To facilitate this, the EU-funded TOPBIO project combined an array of disciplines such as synthetic chemistry, cell biology, nanotechnology and lasers. It brought experts from both the academia and the industrial sectors and contributed to the training of young researchers. Researchers worked towards a fundamental understanding of the molecular design criteria for optimising two-photon absorption. For this purpose, they employed computational methods that allowed them to examine and model the response of complicated molecules while taking into account the surrounding environment. This is a key issue for biomedical applications given the sensitivity of two-photon absorption to environmental effects. The team developed novel practical techniques and accurately characterised the two-photon absorption spectra. This provided major support for the design of second generation two-photon dyes optimised for both non-fluorescent and fluorescent applications. Fluorescent dyes that emit in the biological spectra window could find applications in high resolution in vitro and in vivo imaging, improving disease diagnosis. Furthermore, scientists explored two-photon microfabrication of medical implants or scaffolds for tissue engineering purposes by investigating the polymerisation of biodegradable materials and testing their suitability as cell support. Extensive efforts were directed towards elucidating the mechanism of two-photon induced cell death that could lead to the development of more efficient drugs for use in cancer photodynamic therapy. Overall, the activities of the TOPBIO project addressed an important challenge in the biomedical field associated with disease diagnosis. Serving as more sensitive and photostable probes, the generated TOPBIO dyes are expected to improve existing diagnostic practices and also advance future research. Keywords Dye, two-photon absorption, microfabrication, fluorescence, cellular imaging, TOPBIO, scaffold
