Cyclic (Alkyl)(Amino)Carbene (CAAC) Gold(I) Complexes as Chemotherapeutic Agents.

Cyclic (Alkyl)(Amino)Carbenes (CAACs) have become forceful ligands for gold due to their ability to form very strong ligand-metal bonds. Inspired by the success of Auranofin and other gold complexes as antitumor agents, we have studied the cytotoxicity of bis- and mono-CAAC-gold complexes on different cancer cell lines: HeLa (cervical cancer), A549 (lung cancer), HT1080 (fibrosarcoma) and Caov-3 (ovarian cancer). Further investigations aimed at elucidating their mechanism of action are described. This includes quantification of affinities for TrxR, evaluation of their bioavailability and determination of associated cell death process. Moreover, Transmission Electron Microscopy (TEM) was used to study morphological changes upon exposure. Noticeably, a significant reduction in non-specific binding to serum proteins was observed with CAAC complexes when compared to Auranofin. These results confirm the potential of CAAC-gold complexes in biological environments, which may result in more specific drug-target interactions and decreased side effects.

Paclitaxel-terminated peptide brush polymers.

In this paper, we report the preparation of paclitaxel-terminated peptide brush polymers wherein cell uptake and toxicity are tunable based on peptide sequence. Synthesis was enabled using a new paclitaxel-containing chain termination agent for ring-opening metathesis polymerization (ROMP). Critically, reverse phase HPLC could be used to efficiently separate peptide brush polymers consisting of one fluorophore and one terminal paclitaxel from crude polymer mixtures. These purified terminally-modified polymers showed greater potency than the original mixtures. Drug-terminated peptide brush polymers carrying positive charges exhibited enhanced cell uptake and cytotoxicity as compared to their neutral and negatively charged analogues.

Phosphorescent Pt(ii) complexes spatially arrayed in micellar polymeric nanoparticles providing dual readout for multimodal imaging.

In this paper we report phosphorescent Pt(ii) complexes as monomers which can be directly incorporated into growing polymers. Due to the amphiphilic nature of the polymers they can self-assemble into micellar nanoparticles, where the phosphorescent Pt(ii) complexes can arrange selectively in the core or shell of the nanoparticles. The complexes enable dual orthogonal imaging, made possible by the heavy metal, which enhances the contrast for these micelles in electron microscopy and facilitates spin-orbit coupling that turns on microsecond lifetime luminescence.

Tumor Retention of Enzyme-Responsive Pt(II) Drug-Loaded Nanoparticles Imaged by Nanoscale Secondary Ion Mass Spectrometry and Fluorescence Microscopy.

In nanomedicine, determining the spatial distribution of particles and drugs, together and apart, at high resolution within tissues, remains a major challenge because each must have a different label or detectable feature that can be observed with high sensitivity and resolution. We prepared nanoparticles capable of enzyme-directed assembly of particle therapeutics (EDAPT), containing an analogue of the Pt(II)-containing drug oxaliplatin, an 15N-labeled monomer in the hydrophobic block of the backbone of the polymer, the near-infrared dye Cy5.5, and a peptide that is a substrate for tumor metalloproteinases in the hydrophilic block. When these particles reach an environment rich in tumor associated proteases, the hydrophilic peptide substrate is cleaved, causing the particles to accumulate through a morphology transition, locking them in the tumor extracellular matrix. To evaluate the distribution of drug and EDAPT carrier in vivo, the localization of the isotopically labeled polymer backbone was compared to that of Pt by nanoscale secondary ion mass spectrometry (NanoSIMS). The correlation of NanoSIMS with super-resolution fluorescence microscopy revealed the release of the drug from the nanocarrier and colocalization with cellular DNA within tumor tissue. The results confirmed the dependence of particle accumulation and Pt(II) drug delivery on the presence of a Matrix Metalloproteinase (MMP) substrate and demonstrated antitumor activity. We conclude that these techniques are powerful for the elucidation of the localization of cargo and carrier, and enable a high-resolution assessment of their performance following in vivo delivery.

Mimicking Melanosomes: Polydopamine Nanoparticles as Artificial Microparasols.

A primary role of melanin in skin is the prevention of UV-induced nuclear DNA damage to human skin cells, where it serves to screen out harmful UV radiation. Melanin is delivered to keratinocytes in the skin after being excreted as melanosomes from melanocytes. Defects in melanin production in humans can cause diseases, many of which currently lack effective treatments due to their genetic origins (e.g., skin cancer, vitiligo, and albinism). The widespread prevalence of melanin-related diseases and an increasing interest in the performance of various polymeric materials related to melanin necessitates novel synthetic routes for preparing melanin-like materials. In this work, we prepared melanin-like nanoparticles (MelNPs) via spontaneous oxidation of dopamine, as biocompatible, synthetic analogues of naturally occurring melanosomes, and investigated their uptake, transport, distribution, and UV-protective capabilities in human keratinocytes. Critically, we demonstrate that MelNPs are endocytosed, undergo perinuclear aggregation, and form a supranuclear cap, or so-called microparasol in human epidermal keratinocytes (HEKa), mimicking the behavior of natural melananosomes in terms of cellular distribution and the fact that they serve to protect the cells from UV damage.

Cellular Delivery of Nanoparticles Revealed with Combined Optical and Isotopic Nanoscopy.

Direct polymerization of an oxaliplatin analogue was used to reproducibly generate amphiphiles in one pot, which consistently and spontaneously self-assemble into well-defined nanoparticles (NPs). Despite inefficient drug leakage in cell-free assays, the NPs were observed to be as cytotoxic as free oxaliplatin in cell culture experiments. We investigated this phenomenon by super-resolution fluorescence structured illumination microscopy (SIM) and nanoscale secondary ion mass spectrometry (NanoSIMS). In combination, these techniques revealed NPs are taken up via endocytic pathways before intracellular release of their cytotoxic cargo. As with other drug-carrying nanomaterials, these systems have potential as cellular delivery vehicles. However, high-resolution methods to track nanocarriers and their cargo at the micro- and nanoscale have been underutilized in general, limiting our understanding of their interactions with cells and tissues. We contend this type of combined optical and isotopic imaging strategy represents a powerful and potentially generalizable methodology for cellular tracking of nanocarriers and their cargo.

Synthesis, characterization, and in vitro antiproliferative activity of [salophene]platinum(II) complexes.

A series of methoxy- and fluorine-substituted [salophene]platinum(II) complexes (salophene=N,N'-bis(salicylidene)-1,2-phenylenediamine) were synthesized and characterized by (1) H NMR spectroscopy and mass spectrometry. The structure was confirmed on the example of [5-OCH3 -salophene]platinum(II) (4-Pt) by crystal structure analysis. The cytotoxicity of all complexes against MCF-7 cells showed strong dependence on the kind of substituent and its position on the salicylidene moiety, whereas 1-Pt (H), 3-Pt (4-OCH3 ), and 6-Pt (3-F) exhibited high antiproliferative effects (IC50 <2 µM). Drug lipophilicity and cellular accumulation were analyzed in an attempt to explain the differences in antitumor potency. To gain insight into their mode of action, DNA interaction studies were performed, in which compounds such as 1-Pt acted as non-DNA-binding platinum anticancer drugs, as neither intercalation nor DNA covalent binding were detected.

Dynamics of soft nanomaterials captured by transmission electron microscopy in liquid water.

In this paper we present in situ transmission electron microscopy of synthetic polymeric nanoparticles with emphasis on capturing motion in a solvated, aqueous state. The nanoparticles studied were obtained from the direct polymerization of a Pt(II)-containing monomer. The resulting structures provided sufficient contrast for facile imaging in situ. We contend that this technique will quickly become essential in the characterization of analogous systems, especially where dynamics are of interest in the solvated state. We describe the preparation of the synthetic micellar nanoparticles together with their characterization and motion in liquid water with comparison to conventional electron microscopy analyses.