Aldehyde dehydrogenases (ALDHs) catalyze the oxidation of an aldehyde to a carboxylic acid and are implicated in the etiology of numerous diseases. However, despite their importance, imaging ALDH activity in cells is challenging due to a lack of fluorescent imaging probes. In this report, we present a new family of fluorescent probes composed of an oligothiophene flanked by an aldehyde and an electron donor, termed thiophene-bridged aldehydes (TBAs), which can image ALDH activity in cells. The TBAs image ALDH activity via a fluorescence sensing mechanism based on the modulation of intramolecular charge transfer (ICT) and this enables the TBAs and their ALDH-mediated oxidized products, thiophene-bridged carboxylates (TBCs), to have distinguishable fluorescence spectra. Herein, we show that the TBAs can image ALDH activity in cells via fluorescence microscopy, flow cytometry, and in a plate reader. Using TBA we were able to develop a cell-based high throughput assay for ALDH inhibitors, for the first time, and screened a large, 1460-entry electrophile library against A549 cells. We identified α,β-substituted acrylamides as potent electrophile fragments that can inhibit ALDH activity in cells. These inhibitors sensitized drug-resistant glioblastoma cells to the FDA approved anti-cancer drug, temozolomide. The TBAs have the potential to make the analysis of ALDH activity in cells routinely possible given their ability to spectrally distinguish between an aldehyde and a carboxylic acid.

Hydrocyanines are a class of commonly used reactive oxygen species (ROS) fluorescent imaging probes, which can image ROS in cell culture, organ culture, and in vivo. However, despite their widespread use, hydrocyanines have several drawbacks that limit their effectiveness, such as a high rate of auto-oxidation, a small Stokes shift, and poor water solubility. In addition, the hydrocyanines oxidize into cyanine dyes, which themselves decompose in the presence of ROS, and this further lowers their sensitivity towards detecting ROS. In this report, we present a new hydrocyanine analog, termed as thiophene-bridged hydrocyanine (TBHC), which has its double bonds replaced with a bisthiophene. TBHC is 8.06-fold more stable to auto-oxidation than the hydrocyanine hydro-Cy5 and is significantly better at imaging ROS in cell culture.

The hydrocyanines are a class of dyes that can detect reactive oxygen species (ROS) in cell culture, tissue explants, and in vivo. The hydrocyanines selectively react with radical oxidants, such as superoxide via an amine oxidation mechanism to generate cyanine dyes, thereby imaging ROS. The hydrocyanines can detect nanomolar levels of cellular ROS with tunable emission wavelengths between 560–830 nm. The hydrocyanine dyes have excellent stability against auto-oxidation and can be easily synthesized, and this enabled their rapid commercialization. Herein, we discuss in detail the properties of the hydrocyanine dyes and their current applications across biology and medicine.

In this report we present a polyketal, termed pADK, which has adamantane groups embedded in its backbone, and degrades into neutral excretable compounds. pADK was synthesized via click chemistry and had a MW of 49472 and a PDI of 1.74. We demonstrate here that pADK can increase the transfection efficiency of CD1800 (PEI of 1800 modified β-cyclodextrin) 60 fold, yet cause no increase in toxicity.

Enterobacteriaceae, a type of highly virulent Gram-negative bacteria, can be imaged in vivo via positron emission tomography with ¹⁸F-sorbitol.

The low detection sensitivity of enzyme linked immunosorbent assays (ELISAs) is a central problem in science and limits progress in multiple areas of biology and medicine. In this report we demonstrate that the hydrocyanines, a family of fluorescent reactive oxygen species (ROS) probes, can act as turn on fluorescent horseradish peroxidase (HRP) probes and thereby increase the sensitivity of conventional ELISAs by two orders of magnitude.

In this report, we present a new strategy for targeting chemotherapeutics to tumors, based on targeting extracellular DNA. A gemcitabine prodrug was synthesized, termed H-gemcitabine, which is composed of Hoechst conjugated to gemcitabine. H-gemcitabine has low toxicity because it is membrane-impermeable; however, it still has high tumor efficacy because of its ability to target gemcitabine to E-DNA in tumors. We demonstrate here that H-gemcitabine has a wider therapeutic window than free gemcitabine.

Ultrasound contrast agents (UCAs) have tremendous potential for in vivo molecular imaging because of their high sensitivity. However, the diagnostic potential of UCAs has been difficult to exploit because current UCAs are based on pre-formed microbubbles, which can only detect cell surface receptors. Here, we demonstrate that chemical reactions that generate gas forming molecules can be used to perform molecular imaging by ultrasound in vivo. This new approach was demonstrated by imaging reactive oxygen species in vivo with allylhydrazine, a liquid compound that is converted into nitrogen and propylene gas after reacting with radical oxidants. We demonstrate that allylhydrazine encapsulated within liposomes can detect a 10 micromolar concentration of radical oxidants by ultrasound, and can image oxidative stress in mice, induced by lipopolysaccharide, using a clinical ultrasound system. We anticipate numerous applications of chemically-generated microbubbles for molecular imaging by ultrasound, given ultrasound’s ability to detect small increments above the gas saturation limit, its spatial resolution and widespread clinical use.

The low detection sensitivity of enzyme linked immunosorbent assays (ELISAs) is a central problem in science and limits progress in multiple areas of biology and medicine. In this report we demonstrate that the hydrocyanines, a family of fluorescent reactive oxygen species (ROS) probes, can act as turn on fluorescent horseradish peroxidase (HRP) probes and thereby increase the sensitivity of conventional ELISAs by two orders of magnitude.

In this report we present a polyketal, termed pADK, which has adamantane groups embedded in its backbone, and degrades into neutral excretable compounds. pADK was synthesized via click chemistry and had a MW of 49472 and a PDI of 1.74. We demonstrate here that pADK can increase the transfection efficiency of CD1800 (PEI of 1800 modified β-cyclodextrin) 60 fold, yet cause no increase in toxicity.