Azaphosphinate Dyes: A Low Molecular Weight Near-Infrared Scaffold for Development of Photoacoustic or Fluorescence Imaging Probes.

Near-infrared (NIR) dyes are desirable for biological imaging applications including photoacoustic (PA) and fluorescence imaging. Nonetheless, current NIR dyes are often plagued by relatively large molecular weights, poor water solubility, and limited photostability. Herein, we provide the first examples of azaphosphinate dyes which display desirable properties such as low molecular weight, absorption/emission above 750 nm, and remarkable water solubility. In PA imaging, an azaphosphinate dye exhibited a 4.1-fold enhancement in intensity compared to commonly used standards, the ability to multiplex with existing dyes in whole blood, imaging depths of 2.75 cm in a tissue model, and contrast in mice. An improved derivative for fluorescence imaging displayed a >10-fold reduction in photobleaching in water compared to the FDA-approved indocyanine green dye and could be visualized in mice. This new dye class provides a robust scaffold for the development of photoacoustic or NIR fluorescence imaging agents.

Kamuvudine-9 Protects Retinal Structure and Function in a Novel Model of Experimental Rhegmatogenous Retinal Detachment.

Purpose: Rhegmatogenous retinal detachment (RRD) is a vision-threatening event that benefits from surgical intervention. While awaiting surgical reattachment, irreversible hypoxic and inflammatory damage to the retina often occurs. An interim therapy protecting photoreceptors could improve functional outcomes. We sought to determine whether Kamuvudine-9 (K-9), a derivative of nucleoside reverse transcriptase inhibitors (NRTIs) that inhibits inflammasome activation, and the NRTIs lamivudine (3TC) and azidothymidine (AZT) could protect the retina following RRD. Methods: RRD was induced in mice via subretinal injection (SRI) of 1% carboxymethylcellulose (CMC). To simulate outcomes following the clinical management of RRD, we determined the optimal conditions by which SRI of CMC induced spontaneous retinal reattachment (SRR) occurs over 10 days (RRD/SRR). K-9, 3TC, or AZT was administered via intraperitoneal injection. Inflammasome activation pathways were monitored by abundance of cleaved caspase-1, IL-18, and cleaved caspase-8, and photoreceptor death was assessed by TUNEL staining. Retinal function was assessed by full-field scotopic electroretinography. Results: RRD induced retinal inflammasome activation and photoreceptor death in mice. Systemic administration of K-9, 3TC, or AZT inhibited retinal inflammasome activation and photoreceptor death. In the RRD/SRR model, K-9 protected retinal electrical function during the time of RRD and induced an improvement following retinal reattachment. Conclusions: K-9 and NRTIs exhibit anti-inflammatory and neuroprotective activities in experimental RRD. Given its capacity to protect photoreceptor function during the period of RRD and enhance retinal function following reattachment, K-9 shows promise as a retinal neuroprotectant and warrants study in RRD. Further, this novel RRD/SRR model may facilitate experimental evaluation of functional outcomes relevant to RRD.

Synthesis and application of a ratiometric probe for hydrogen peroxide.

Molecular imaging of biological analytes provides detailed insights into signaling processes. Ratiometric probes are particularly attractive due to the ability to quantify analyte production. However, design strategies for ratiometric probes can be hindered by spectral overlap of the product and reactant species. In this chapter, we provide protocols for the synthesis and application of RF620, a ratiometric probe for H2O2 displaying dramatic changes in both excitation and emission wavelengths, designed using an approach we term chemoselective alteration of fluorophore scaffolds. The probe contains a chemoselective functional group within a fluorescent xanthene scaffold, resulting in the in situ synthesis of a new fluorophore upon reaction with H2O2. Under physiological conditions, RF620 exhibits far-red to near-infrared excitation and emission, and upon reaction with H2O2, RF620 is chemically converted into tetramethylrhodamine, producing a significant (~66nm) blue-shift in excitation and emission. RF620 can be used for ratiometric, molecular imaging of endogenous H2O2 production in living cells.

Total Synthesis and Biological Evaluation of Apratoxin E and Its C30 Epimer: Configurational Reassignment of the Natural Product.

Apratoxin E provided the inspiration for the design of apratoxin A/E hybrids under preclinical development. Through total synthesis using two different strategies, it was determined that the originally proposed configuration of the thiazoline at C30 is opposite from that in apratoxin A, in contrast to previous assumptions on biosynthetic grounds. The epimer and true natural apratoxin E were synthesized, and the biological activities were evaluated.