We have developed a few new near-infrared fluorescent probes with single-photon frequency upconversion fluorescence (FUCL) properties for sensitive detection of pH changes in live cells by taking advantages of upconversion fluorescence imaging such as extremely low photo-damage to living organisms, low auto-fluorescence from biological samples, and deep tissue penetration under excitation at 800 nm.  The water solubility and biocompatibility of these probes were achieved by introducing mannose residues to near-infrared hemicyanine and rhodamine dyes. Under neutral and basic conditions, the probes maintain non-fluorescent closed spirolactam ring structures. However, the probes respond to pH changes from 7.0 to 2.0 with high sensitivity and significant increases in both conventional and upconversion fluorescence under excitation at 700 nm and 800 nm, respectively. The probes show good biocompatibility, excellent photostability, and highly selective and sensitive responses to pH changes.

Near-infrared fluorescent probes with single-photon frequency upconversion fluorescence for detection in live cells

256th National Meeting (2018)

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