Copper-Catalyzed Covalent Dimerization of Near-Infrared Fluorescent Cyanine Dyes: Synergistic Enhancement of Photoacoustic Signals for Molecular Imaging of Tumors.

Photoacoustic (PA) imaging relies on the absorption of light by chromophores to generate acoustic waves used to delineate tissue structures and physiology. Here, we demonstrate that Cu(II) efficiently catalyzes the dimerization of diverse near-infrared (NIR) cyanine molecules, including a peptide conjugate. NMR spectroscopy revealed a C-C covalent bond along the heptamethine chains, creating stable molecules under conditions such as a wide range of solvents and pH mediums. Dimerization achieved >90% fluorescence quenching, enhanced photostability, and increased PA signals by a factor of about 4 at equimolar concentrations compared to the monomers. In vivo study with a mouse cancer model revealed that dimerization enhanced tumor retention and PA signal, allowing cancer detection at doses where the monomers are less effective. While the dye dimers highlighted peritumoral blood vessels, the PA signal for dimeric tumor-targeting dye-peptide conjugate, LS301, was diffuse throughout the entire tumor mass. A combination of the ease of synthesis, diversity of molecules that are amenable to Cu(II)-catalyzed dimerization, and the high acoustic wave amplification by these stable dimeric small molecules ushers a new strategy to develop clinically translatable PA molecular amplifiers for the emerging field of molecular photoacoustic imaging.

Facile iterative synthesis of 2,5-terpyrimidinylenes as nonpeptidic alpha-helical mimics.

A facile iterative synthesis of 2,5-terpyrimidinylenes that are structurally analogous to alpha-helix mimics is presented. Condensation of amidines with readily prepared alpha,beta-unsaturated alpha-cyanoketones gives 5-cyano-substituted pyrimidines. Iterative transformation of the 5-cyano group into an amidine allows synthesis of 2,5-terpyrimidinylenes with variable groups at the 4-, 4'-, and 4''-positions. These compounds are designed to mimic the i, i + 4, and i + 7 sites of an alpha-helix.

Radionuclides transform chemotherapeutics into phototherapeutics for precise treatment of disseminated cancer.

Most cancer patients succumb to disseminated disease because conventional systemic therapies lack spatiotemporal control of their toxic effects in vivo, particularly in a complicated milieu such as bone marrow where progenitor stem cells reside. Here, we demonstrate the treatment of disseminated cancer by photoactivatable drugs using radiopharmaceuticals. An orthogonal-targeting strategy and a contact-facilitated nanomicelle technology enabled highly selective delivery and co-localization of titanocene and radiolabelled fluorodeoxyglucose in disseminated multiple myeloma cells. Selective ablation of the cancer cells was achieved without significant off-target toxicity to the resident stem cells. Genomic, proteomic and multimodal imaging analyses revealed that the downregulation of CD49d, one of the dimeric protein targets of the nanomicelles, caused therapy resistance in small clusters of cancer cells. Similar treatment of a highly metastatic breast cancer model using human serum albumin-titanocene formulation significantly inhibited cancer growth. This strategy expands the use of phototherapy for treating previously inaccessible metastatic disease.

Small Molecule Inhibitors of Metabolic Enzymes Repurposed as a New Class of Anthelmintics.

The enormous prevalence of infections caused by parasitic nematodes worldwide, coupled to the rapid emergence of their resistance to commonly used anthelmintic drugs, presents an urgent need for the discovery of new drugs. Herein, we have identified several classes of small molecules with broad spectrum activity against these pathogens. Previously, we reported the identification of carnitine palmitoyltransferases (CPTs) as a representative class of enzymes as potential targets for metabolic chokepoint intervention that was elucidated from a combination of chemogenomic screening and experimental testing in nematodes. Expanding on these previous findings, we have discovered that several chemical classes of known small molecule inhibitors of mammalian CPTs have potent activity as anthelmintics. Cross-clade efficacy against a broad spectrum of adult parasitic nematodes was demonstrated for multiple compounds from different series. Several analogs of these initial hit compounds were designed and synthesized. The compounds we report represent a good starting point for further lead identification and optimization for development of new anthelmintic drugs with broad spectrum activity and a novel mechanism of action.

In Vivo Fluorescence Reflectance Imaging with Subcutaneous Mouse Tumor Models.

Optical imaging is undoubtedly one of the most versatile and widely used imaging techniques in both research and clinical practice. Among optical imaging technologies, fluorescence imaging is the most popularly used and has become an essential tool in biomedical science. A key component of fluorescence imaging is fluorescence-producing reporters, including fluorescent dyes and conjugates, as well as fluorescent proteins. For in vivo imaging applications, fluorophores with long emission at the near-infrared (NIR) region are generally preferred to overcome the photon attenuation in living tissue. Here, we describe the in vivo fluorescence imaging of an integrin αυß3 targeted NIR fluorescent probe (cRGD-ICG-Der-02) using subcutaneous mouse tumor models.

Fluorescence Imaging of Inflammation in Live Animals.

Inflammation is associated with many diseases, such as stroke, cancer, and atherosclerosis. Noninvasive in vivo monitoring of inflammation can provide deeper understanding of such diseases, which might help to develop better treatment. Inflammation normally causes neutrophils and macrophages to generate reactive oxygen species (ROS) as the destruction tool, which can be used as a biomarker for inflammation. Near-infrared (NIR) window is optimal for in vivo fluorescence imaging owing to the reduced autofluorescence and low attenuation of light in biological tissues. Among NIR fluorescent probes, activatable probes have the promise of achieving high imaging contrast. In this chapter, we describe the method for in vivo fluorescence imaging of inflammation using a ROS-activatable NIR probe.

Gradient-Based Algorithm for Determining Tumor Volumes in Small Animals Using Planar Fluorescence Imaging Platform.

Planar fluorescence imaging is widely used in biological research because of its simplicity, use of non-ionizing radiation, and high-throughput data acquisition. In cancer research, where small animal models are used to study the in vivo effects of cancer therapeutics, the output of interest is often the tumor volume. Unfortunately, inaccuracies in determining tumor volume from surface-weighted projection fluorescence images undermine the data, and alternative physical or conventional tomographic approaches are prone to error or are tedious for most laboratories. Here, we report a method that uses a priori knowledge of a tumor xenograft model, a tumor-targeting near infrared probe, and a custom-developed image analysis planar view tumor volume algorithm (PV-TVA) to estimate tumor volume from planar fluorescence images. Our algorithm processes images obtained using near infrared light for improving imaging depth in tissue in comparison with light in the visible spectrum. We benchmarked our results against the actual tumor volume obtained from a standard water volume displacement method. Compared with a caliper-based method that has an average deviation from an actual volume of 18% (204.34 ± 115.35 mm3), our PV-TVA average deviation from the actual volume was 9% (97.24 ± 70.45 mm3; P < .001). Using a normalization-based analysis, we found that bioluminescence imaging and PV-TVA average deviations from actual volume were 36% and 10%, respectively. The improved accuracy of tumor volume assessment from planar fluorescence images, rapid data analysis, and the ease of archiving images for subsequent retrieval and analysis potentially lend our PV-TVA method to diverse cancer imaging applications.

Click Reaction-Mediated Functionalization of Near-Infrared Pyrrolopyrrole Cyanine Dyes for Biological Imaging Applications.

A clickable pyrrolopyrrole cyanine (PPCy) dye was synthesized by incorporating an alkyne moiety, followed by click reaction with azide-functionalized molecules of different polarities. The clickable dyes are readily amenable to labelling diverse molecules and exhibit an exceptionally high photostability and an impressive fluorescence quantum yield.