Far-red BODIPY-based oxime esters: photo-uncaging and drug delivery.

Far-red BODIPY-based oxime esters for photo-uncaging were designed to release molecules of interest with carboxylic acids. The low power red LED light breaks the N-O oxime ester bond and frees the caged molecules. We studied the mechanism and kinetics of the uncaging procedure using a 1H NMR spectrometer. Moreover, the drug delivery strategy to release valproic acid (VPA) on demand was tested in vitro using this far-red BODIPY photo-uncaging strategy to induce apoptosis in tumor cells.

Quantitative dynamic cellular imaging based on 3D unwrapped optically computed phase microscopy.

We investigate continuous observation of dynamic phenomena through quantitative phase microscopy. We conduct imaging studies using optically computed phase microscopy, a novel imaging technology developed in our lab, to the best of our knowledge. Inevitably, continuous phase imaging is affected by phase wrapping artifacts, which affects correct quantification of sample dynamics. To address this issue, we develop a 3D unwrapping method that exploits data correlation in space as well as in time. We validate our 3D phase unwrapping method using simulated data. We further validate 3D phase unwrapping using experimental data and demonstrate quantitative phase imaging that accurately characterizes sample dynamics. We image the nanoscale motion of the sample actuated by a piezo transducer (PZT). We calculate the displacement using 3D unwrapped phase, and the result is consistent with the known motion of the PZT. We also image live cells that were detaching from the substrate of the petri dish. The optical path length calculated using 3D unwrapped phase increases as the dry mass of the cell becomes more concentrated during the detachment process.

Optically computed phase microscopy for quantitative dynamic imaging of label-free cells and nanoparticles.

Numerous drug delivery systems based on nanoparticles have been developed, such as those used in BioNTech/Pfizer's and Moderna's Covid vaccines. Knowledge on mechanical interactions between cells and nanoparticles is critical to advance the efficiency and safety of these drug delivery systems. To quantitatively track the motion of cell (transparent) and nanoparticles (nontransparent) with nanometer displacement sensitivity, we investigate a novel imaging technology, optically computed phase microscopy (OCPM) that processes 3D spatial-spectral data through optical computation. We demonstrate that OCPM has the capability to image the motion of cells and magnetic nanoparticles that are mechanically excited by an external magnetic field, quantitatively and in the en face plane.

A BODIPY-Based Far-Red-Absorbing Fluorescent Probe for Hypochlorous Acid Imaging.

Hypochlorous acid (HClO) is produced by white blood cells to defend against injury and bacteria. However, as one of the reactive oxygen species, high intracellular HClO concentration could lead to chronic diseases that affect the cardiovascular and nervous systems. To monitor HClO concentrations in bio-samples, the fluorescent probe is preferred to have: a) absorbability in the far-red window with reduced light-toxicity and improved tissue penetration depth, b) ratiometric feature for accurate analysis. In this study, we reported a far-red ratiometric HClO fluorescence probe based on BODIPY chromophore and aldoxime sensing group. Not only the color change of the probe solution can be detected by naked eyes, but also the emission ratios (I645/I670) showed a significant increase upon the introduction of HClO. More importantly, the feasibility of HClO monitoring in bio-samples was demonstrated in vitro using a confocal microscope.

Optically computed phase microscopy to assess cellular uptake of lipid nanoparticles.

We developed a novel optically computed phase microscopy (OCPM) system, for depth-resolved phase imaging. We used OCPM to assess cellular uptake of lipid nanoparticles (LNPs), for the optimization of drug delivery systems based on LNPs.

Regulating Mitochondrial pH with Light and Implications for Chemoresistance.

Chemoresistance is one of the major challenges for cancer treatment, more recently ascribed to defective mitochondrial outer membrane permeabilization (MOMP), significantly diminishing chemotherapeutic agent-induced apoptosis. A boron-dipyrromethene (BODIPY) chromophore-based triarylsulfonium photoacid generator (BD-PAG) was used to target mitochondria with the aim to regulate mitochondrial pH and further depolarize the mitochondrial membrane. Cell viability assays demonstrated the relative biocompatibility of BD-PAG in the dark while live cell imaging suggested high accumulation in mitochondria. Specific assays indicated that BD-PAG is capable of regulating mitochondrial pH with significant effects on mitochondrial membrane depolarization. Therapeutic tests using chlorambucil in combination with BD-PAG revealed a new strategy in chemoresistance suppression.

BODIPY-Based Photoacid Generators for Light-Induced Cationic Polymerization.

Photoacid generators (PAGs) are organic compounds that can generate protons (H+) upon irradiation with certain wavelengths of light. In this work, we designed and synthesized the first BODIPY-based PAGs with D-A and D-π-A conjugation structures and achieved green and red LED light-induced acid generation. By the use of red-light absorbance, red-LED-triggered cationic polymerization was demonstrated as a proof-of-concept application of these PAGs.

Photo-uncaging of BODIPY oxime ester for histone deacetylases induced apoptosis in tumor cells.

A new class of BODIPY-based oxime ester photo-uncaging group was designed to release carboxylic acids. The mechanism and kinetics of the photo-uncaging procedure were studied. Further, we constructed a photo-uncaging drug delivery system to release valproic acid (VPA), which can inhibit the histone deacetylases and induce apoptosis in tumor cells.