Taihong Liu

Novel BODIPY-Based Fluorescence Turn-on Sensor for Fe3+ and Its Bioimaging Application in Living Cells

A novel boron-dipyrromethene (BODIPY) based fluorescence turn-on sensor for detecting Fe(3+) in aqueous media is reported with 23-fold fluorescence enhancement. The sensor is comprised of a combination of BODIPY fluorophore and a new Fe(3+)-recognizing cryptand that exhibits high selectivity, sensitivity, and reversibility toward Fe(3+) detection. Cell imaging studies demonstrate that this sensor is capable of sensing Fe(3+) in living cells.

Chromophoric materials derived from a natural azulene: syntheses, halochromism and one-photon and two-photon microlithography

In addition to their use as colorants in food and cosmetics, various natural dyes possess photophysical properties that could enable their use as modular building blocks for preparing eco-friendly and non-toxic chromophores. Among the natural pigments, guaiazulene holds great potential due to its unique optical and electronic properties. Thus, in order to explore and understand the properties of guaiazulene-containing chromophores, a series of 4-styrylguaiazulenes 3a–l were prepared by condensation of the C-4 methyl group of naturally-occurring guaiazulene 1 with various aromatic carboxaldehydes 2a–l. Treatment of these analogs 3a–l with a strong acid protonates the electron-rich C-3 position and reveals a reversible halochromic behavior where the optical energy gap responds predictably to the electron-donor strength and the degree of π-conjugation. Additionally, acid-doping is accompanied by efficient fluorescence switch-on, where 3e(H+) and 3g(H+) exhibited considerably higher fluorescence quantum yields than the neutral precursor. These properties facilitated the design of a new non-erasable 3D fluorescence readout (permanent or write-once read-many, WORM) system, which is comprised of a switch-on fluorescent guaiazulene-containing chromophore 3e and a commercially available iodonium photo-acid generator (PAG) in thin polymethyl methacrylate (PMMA) films.

Fluorenyl-Loaded Quatsome Nanostructured Fluorescent Probes

Delivery of hydrophobic materials in biological systems, for example, contrast agents or drugs, is an obdurate challenge, severely restricting the use of materials with otherwise advantageous properties. The synthesis and characterization of a highly stable and water-soluble nanovesicle, referred to as a quatsome (QS, vesicle prepared from cholesterol and amphiphilic quaternary amines), that allowed the nanostructuration of a nonwater soluble fluorene-based probe are reported. Photophysical properties of fluorenyl–quatsome nanovesicles were investigated via ultraviolet–visible absorption and fluorescence spectroscopy in various solvents. Colloidal stability and morphology of the nanostructured fluorescent probes were studied via cryogenic transmission electronic microscopy, revealing a “patchy” quatsome vascular morphology. As an example of the utility of these fluorescent nanoprobes, examination of cellular distribution was evaluated in HCT 116 (an epithelial colorectal carcinoma cell line) and COS-7 (an African green monkey kidney cell line) cell lines, demonstrating the selective localization of C-QS and M-QS vesicles in lysosomes with high Pearson’s colocalization coefficient, where C-QS and M-QS refer to quatsomes prepared with hexadecyltrimethylammonium bromide or tetradecyldimethylbenzylammonium chloride, respectively. Further experiments demonstrated their use in time-dependent lysosomal tracking.