Evaluation and activity of new porphyrin-peptide cage-type conjugates for the photoinactivation of Mycobacterium abscessus.

Mycobacterium abscessus is increasingly recognized as an emerging opportunistic pathogen causing severe lung diseases and cutaneous infections. However, treatment of M. abscessus infections remains particularly challenging, largely due to intrinsic resistance to a wide panel of antimicrobial agents. New therapeutic alternatives are urgently needed. Herein, we show that, upon limited irradiation with a blue-light source, newly developed porphyrin-peptide cage-type photosensitizers exert a strong bactericidal activity against smooth and rough variants of M. abscessus in planktonic cultures and in biofilms, at low concentrations. Atomic force microscopy unraveled important morphological alterations that include a wrinkled and irregular bacterial surface. The potential of these compounds for a photo-therapeutic use to treat M. abscessus skin infections requires further evaluations.IMPORTANCEMycobacterium abscessus causes persistent infections and is extremely difficult to eradicate. Despite intensive chemotherapy, treatment success rates remain very low. Thus, given the unsatisfactory performances of the current regimens, more effective therapeutic alternatives are needed. In this study, we evaluated the activity of newly described porphyrin-peptide cage-type conjugates in the context of photodynamic therapy. We show that upon light irradiation, these compounds were highly bactericidal against M. abscessus in vitro, thus qualifying these compounds for future studies dedicated to photo-therapeutic applications against M. abscessus skin infections.

Self-assembled porphyrin-peptide cages for photodynamic therapy.

The development of photodynamic therapy requires access to smart photosensitizers which combine appropriate photophysical and biological properties. Interestingly, supramolecular and dynamic covalent chemistries have recently shown their ability to produce novel architectures and responsive systems through simple self-assembly approaches. Herein, we report the straightforward formation of porphyrin-peptide conjugates and cage compounds which feature on their surface chemical groups promoting cell uptake and specific organelle targeting. We show that they self-assemble, in aqueous media, into positively-charged nanoparticles which generate singlet oxygen upon green light irradiation, while also undergoing a chemically-controlled disassembly due to the presence of reversible covalent linkages. Finally, the biological evaluation in cells revealed that they act as effective photosensitizers and promote synergistic effects in combination with Doxorubicin.

Supramolecular self-assembly of triazine-based small molecules: targeting the endoplasmic reticulum in cancer cells.

The endoplasmic reticulum (ER) is one of the most important organelles controlling myriads of cellular functions including protein folding/misfolding/unfolding, calcium ion homeostasis and lipid biosynthesis. Subsequently, due to its functional dysregulation in cancer cells, it has emerged as an interesting target for anti-cancer therapy. However, specific targeting of the ER in cancer cells remains a major challenge due to the lack of ER-selective chemical tools. Furthermore, for performing multiple cellular functions the ER is dependent on the nucleus through complicated cross-talk. Herein, we have engineered a supramolecular self-assembled hexameric rosette structure from two small molecules: tri-substituted triazine and 5-fluorouracil (5-FU). This rosette structure consists of an ER-targeting moiety with a fluorescence tag, an ER-stress inducer and a nuclear DNA damaging drug simultaneously, which further self-assembled into an ER-targeting spherical nano-scale particle (ER-NP). These ER-NPs internalized into HeLa cervical cancer cells by macropinocytosis and specifically localized into the ER to induce ER stress and DNA damage leading to cell death through apoptosis. Interestingly, ER-NPs initiated autophagy, inhibited by a combination of ER-NPs and chloroquine (CQ) to augment cancer cell death. This work has the potential to exploit the concept of supramolecular self-assembly into developing novel nano-scale materials for specific sub-cellular targeting of multiple organelles for future anti-cancer therapy.

Lipid Nanoparticle-Mediated Induction of Endoplasmic Reticulum Stress in Cancer Cells.

The endoplasmic reticulum (ER) primarily guides protein synthesis, folding, transport, and lipid biosynthesis inside the cells. As a result, dysregulation in those cellular functions leading to ER stress has recently emerged as one of the hallmarks of cancer. Yet, precise navigation in the ER in cancer cells has continued to be a formidable task. Herein, we engineered a lipid nanoparticle (17AAG-ER-NP) containing (a) ER targeting moiety (Tosyl), (b) fluorescent tag with DNA damaging capability (1,8-naphthalimide), and (c) ER stress inducer (17AAG, Hsp90 inhibitor). These lipidic nanoparticles were confined in the ER of HeLa cells over 6 h through caveolin-controlled endocytosis confirmed by confocal microscopy. Western blot analysis, fluorescent microscopy, and flow cytometry studies confirmed that 17AAG-ER-NPs can concurrently activate ER stress and nuclear DNA impairment for arresting the cell cycle in the G2-M phase to elicit late apoptosis, followed by cell death, in a greatly augmented manner compared to free drugs. Interestingly, this nanoparticle-mediated ER stress activated autophagy, which was suppressed through a cocktail treatment with 17AAG-ER-NPs and chloroquine (autophagy inhibitor), prompted remarkable HeLa cell killing at submicromolar concentration. This nanoplatform can support new tools to impair multiple targets in the ER for future cancer therapy.

Polymer conjugated graphene-oxide nanoparticles impair nuclear DNA and Topoisomerase I in cancer.

Cancer chemotherapy had been dominated by the use of small molecule DNA damaging drugs. Eventually, the emergence of DNA damage repair machinery in cancer cells has led to combination therapy with the DNA topology controlling enzyme, topoisomerase I inhibitor along with DNA impairing agents. However, integrating multiple drugs having diverse water solubility and hence bio-distribution effectively for cancer treatment remains a significant challenge, which can be addressed by using suitable nano-scale materials. Herein, we have chemically conjugated graphene oxide (GO) with biocompatible and hydrophilic polymers [polyethylene glycol (PEG) and ethylene-diamine modified poly-isobutylene-maleic anhydride (PMA-ED)], which can encompass highly hydrophobic topoisomerase I inhibitor, SN38. Interestingly, these sheet structured GO-polymer-SN38 composites self-assembled into spherical nanoparticles in water after complexing with a hydrophilic DNA damaging drug, cisplatin. These nanoparticles showed much improved colloidal stability in water compared to their drug-loaded non-polymeric counterpart. These SN38 and cisplatin laden GO-polymer nanoparticles were taken up by HeLa cancer cells through clathrin-dependent endocytosis to home into lysosomes within 6 h, as confirmed by confocal microscopy. A combination of gel electrophoresis, flow cytometry, and fluorescence microscopy showed that these nanoparticles damaged nuclear DNA and induced topoisomerase I inhibition leading to apoptosis and finally improved HeLa cell death. These self-assembled GO-polymer nanoparticles can be used for strategic impairment of multiple cellular targets involving hydrophobic and hydrophilic drugs for effective combination therapy.

Self-Assembled Glycosylated Chalcone-Boronic Acid Nanodrug Exhibits Anticancer Activity through Mitochondrial Impairment.

Chalcone and boronic acids are important privileged structures in myriads of natural and synthetic products having diverse biological activities. However, their therapeutic window is highly narrow due to their hydrophobic nature affecting unpredictable biodistribution. To address this, we herein have synthesized a novel hybrid glycosylated chalcone-boronic acid library. Cell viability, flow cytometry, confocal microscopy, and gel electrophoresis assays demonstrated that one of the library members induces cell cycle arrest in the G2/M phase through the activation of p21 and decrease levels of cyclin B1 and CDK1. In addition, it also induces apoptosis, primarily due to the inhibition of Bcl-2/Bcl-xl and the augmentation of BAX to prompt mitochondrial damage and reactive oxygen species generation. Most interestingly, the lead cytotoxic glycosylated chalcone-boronic acid self-assembled in water into a spherical nanodrug that can further entrap another anticancer drug (doxorubicin) to show remarkably improved efficacy in breast cancer cells. This novel lead compound has prospective as a vector-free nanodrug for combination cancer therapy.