Live-cell fluorescent microscopy platforms for real-time monitoring of polyplex–cell interaction: Basic guidelines

Applications of Intravital Imaging in Cancer Immunotherapy

Currently, immunotherapy is one of the most effective treatment strategies for cancer. However, the efficacy of any specific anti-tumor immunotherapy can vary based on the dynamic characteristics of immune cells, such as their rate of migration and cell-to-cell interactions. Therefore, understanding the dynamics among cells involved in the immune response can inform the optimization and improvement of existing immunotherapy strategies. In vivo imaging technologies use optical microscopy techniques to visualize the movement and behavior of cells in vivo, including cells involved in the immune response, thereby showing great potential for application in the field of cancer immunotherapy. In this review, we briefly introduce the technical aspects required for in vivo imaging, such as fluorescent protein labeling, the construction of transgenic mice, and various window chamber models. Then, we discuss the elucidation of new phenomena and mechanisms relating to tumor immunotherapy that has been made possible by the application of in vivo imaging technology. Specifically, in vivo imaging has supported the characterization of the movement of T cells during immune checkpoint inhibitor therapy and the kinetic analysis of dendritic cell migration in tumor vaccine therapy. Finally, we provide a perspective on the challenges and future research directions for the use of in vivo imaging technology in cancer immunotherapy.

Labelling of DNA and RNA in the cellular environment by means of bioorthogonal cycloaddition chemistry

Labelling of nucleic acids as biologically important cellular components is a crucial prerequisite for the visualization and understanding of biological processes. Efficient bioorthogonal chemistry and in particular cycloadditions fullfill the requirements for cellular applications. The broadly applied Cu(i)-catalyzed azide-alkyne cycloaddition (CuAAC), however, is limited to labellings in vitro and in fixed cells due to the cytotoxicity of copper salts. Currently, there are three types of copper-free cycloadditions used for nucleic acid labelling in the cellular environment: (i) the ring-strain promoted azide-alkyne cycloaddition (SPAAC), (ii) the "photoclick" 1,3-dipolar cycloadditions, and (iii) the Diels-Alder reactions with inverse electron demand (iEDDA). We review only those building blocks for chemical synthesis on solid phase of DNA and RNA and for enzymatic DNA and RNA preparation, which were applied for labelling of DNA and RNA in situ or in vivo, i.e. in the cellular environment, in fixed or in living cells, by the use of bioorthogonal cycloaddition chemistry. Additionally, we review the current status of orthogonal dual and triple labelling of DNA and RNA in vitro to demonstrate their potential for future applications in situ or in vivo.

PEI-NIR Heptamethine Cyanine Nanotheranostics for Tumor Targeted Gene Delivery

Polymer-based nanotheranostics are appealing tools for cancer treatment and diagnosis in the fast-growing field of nanomedicine. A straightforward preparation of novel engineered PEI-based nanotheranostics incorporating NIR fluorescence heptamethine cyanine dyes (NIRF-HC) to enable them with tumor targeted gene delivery capabilities is reported. Branched PEI-2 kDa (b2kPEI) is conjugated with IR-780 and IR-783 dyes by both covalent and noncovalent simple preparative methodologies varying their stoichiometry ratio. The as-prepared set of PEI-NIR-HC nanocarriers are assayed in vitro and in vivo to evaluate their gene transfection efficiency, cellular uptake, cytotoxicity, internalization and trafficking mechanisms, subcellular distribution, and tumor specific gene delivery. The results show the validity of the approach particularly for one of the covalent IR783-b2kPEI conjugates that exhibit an enhanced tumor uptake, probably mediated by organic anion transporting peptides, and favorable intracellular transport to the nucleus. The compound behaves as an efficient nanotheranostic transfection agent in NSG mice bearing melanoma G361 xenographs with concomitant imaging signal and gene concentration in the targeted tumor. By this way, advanced nanotheranostics with multifunctional capabilities (gene delivery, tumor-specific targeting, and NIR fluorescence imaging) are generated in which the NIRF-HC dye component accounts for simultaneous targeting and diagnostics, avoiding additional incorporation of additional tumor-specific targeting bioligands.

Live-cell imaging to compare the transfection and gene silencing efficiency of calcium phosphate nanoparticles and a liposomal transfection agent

The processing of DNA (for transfection) and short interfering RNA (siRNA; for gene silencing), introduced into HeLa cells by triple-shell calcium phosphate nanoparticles, was followed by live-cell imaging. For comparison, the commercial liposomal transfection agent Lipofectamine was used. The cells were incubated with these delivery systems, carrying either enhanced green fluorescent protein (eGFP)-encoding DNA or siRNA against eGFP. In the latter case, HeLa cells that stably expressed eGFP were used. The expression of eGFP started after 5 h in the case of nanoparticles and after 4 h in the case of Lipofectamine. The corresponding times for gene silencing were 5 h (nanoparticles) and immediately after incubation (Lipofectamine). The expression of eGFP was notably enhanced 2-3 h after cell division (mitosis). In general, the transfection and gene silencing efficiencies of the nanoparticles were lower than those of Lipofectamime, even at a substantially higher dose (factor 20) of nucleic acids. However, the cytotoxicity of the nanoparticles was lower than that of Lipofectamine, making them suitable vectors for in vivo application.

Polycation-mediated integrated cell death processes

One of the major challenges in the field of nucleic acid delivery is the design of delivery vehicles with attributes that render them safe as well as efficient in transfection. To this end, polycationic vectors have been intensely investigated with native polyethylenimines (PEIs) being the gold standard. PEIs are highly efficient transfectants, but depending on their architecture and size they induce cytotoxicity through different modes of cell death pathways. Here, we briefly review dynamic and integrated cell death processes and pathways, and discuss considerations in cell death assay design and their interpretation in relation to PEIs and PEI-based engineered vectors, which are also translatable for the design and studying the safety of other transfectants.

Bioactive cembrane derivatives from the Indian Ocean soft coral, Sinularia kavarattiensis

Marine organisms and their metabolites represent a unique source of potential pharmaceutical substances. In this study, we examined marine-derived substances for their bioactive properties in a cell-based Chikungunya virus (CHIKV) replicon model and for in vitro anti-inflammatory activity. In the screening of a marine sample library, crude extracts from the Indian soft coral, Sinularia kavarattiensis, showed promising activity against the CHIKV replicon. Bioassay-guided chemical fractionation of S. kavarattiensis resulted in the isolation of six known norcembranoids (1-6) and one new compound, named kavaranolide (7). The structures were elucidated on the basis of NMR and MS spectroscopic data. Compounds 1-3 and 5-7 were evaluated for their replicon-inhibiting potential in the CHIKV model by using a luminescence-based detection technique and live cell imaging. Compounds 1 and 2 showed moderate inhibition of the CHIKV replicon, but imaging studies also revealed cytotoxic properties. Moreover, the effects of the isolated compounds on primary microglial cells, an experimental model for neuroinflammation, were evaluated. Compound 2 was shown to modulate the immune response in microglial cells and to possess potential anti-inflammatory properties by dose-dependently reducing the release of pro- and anti-inflammatory cytokines.