The synthesis and characterization of a novel two-photon-absorbing fluorene derivative, LT1, selective for the lysosomes of HCT 116 cancer cells, is reported. Linear and nonlinear photophysical and photochemical properties of the probe were investigated to evaluate the potential of the probe for two-photon fluorescence microscopy (2PFM) lysosomal imaging. The cytotoxicity of the probe was investigated to evaluate the potential of using this probe for live two-photon fluorescence biological imaging applications. Colocalization studies of the probe with commercial Lysotracker Red in HCT 116 cells demonstrated the specific localization of the probe in the lysosomes with an extremely high colocalization coefficient (0.96). A figure of merit was introduced to allow comparison between probes. LT1 has a number of properties that far exceed those of commercial lysotracker probes, including higher two-photon absorption cross sections, good fluorescence quantum yield, and, importantly, high photostability, all resulting in a superior figure of merit. 2PFM was used to demonstrate lysosomal tracking with LT1.

We demonstrate the use of high-speed, multiphoton absorption polymerization (MAP) for the fabrication of large-area microfluidic master structures. High-speed fabrication in SU8 without laser-induced damage is made possible by the use of a novel photoacid generator with a high two-photon-absorption cross-section. Master structures fabricated with MAP can be used to produce polydimethylsiloxane microchannels with high aspect ratios and/or arbitrary cross-sections. Microchannels with different cross-sections and heights can be combined readily in a single device. This fabrication technique significantly increases the diversity of channel architectures available for microfluidic devices.

Singlet oxygen sensitized photodynamic therapy (PDT) relies on the concentration of oxygen in the tissue to be treated. Most cancer lesions, however, have poor vasculature and, as a result, are hypoxic, significantly hindering PDT efficacies. An oxygen-independent PDT method may circumvent this limitation. To address this, we prepared sulfonium salts that produced a pH drop within HCT 116 cells via the generation of photoacid within the cytosol. This process was driven by one- or two-photon absorption (1PA or 2PA) of the endocytosed photoacid generators (PAGs). One of these PAGs, which had a significantly lower dark cytotoxicity and was more efficient in generating photoacid, effectively induced necrotic cell death in the HCT 116 cells. The data suggests that PAGs may be an attractive alternative PDT modality to selectively induce cell death in oxygen-deprived tissue such as tumors.

Microwave-assisted synthesis of triarylsulfonium salt photoacid generators (PAGs) afforded reaction times 90 to 420 times faster than conventional thermal conditions, with photoacid quantum yields of new sulfonium PAGs ranging from 0.01 to 0.4.