Artificial Melanogenesis by Confining Melanin/Polydopamine Production inside Polymersomes

Melanin and polydopamine are potent biopolymers for the development of biomedical nanosystems. However, applications of melanin or polydopamine-based nanoparticles are limited by drawbacks related to a compromised colloidal stability over long time periods and associated cytotoxicity. To overcome these hurdles, a novel strategy is proposed that mimics the confinement of natural melanin in melanosomes. Melanosome mimics are developed by co-encapsulating the melanin/polydopamine precursors L-DOPA/dopamine with melanogenic enzyme Tyrosinase within polymersomes. The conditions of polymersome formation are optimized to obtain melanin/polydopamine polymerization within the cavity of the polymersomes. Similar to native melanosomes, polymersomes containing melanin/polydopamine show long-term colloidal stability, cell-compatibility, and potential for cell photoprotection. This novel kind of artificial melanogenesis is expected to inspire new applications of the confined melanin/polydopamine biopolymers.

DNA-tethered Polymersome Clusters as Nanotheranostic Platform

Nanotheranostics combine the use of nanomaterials and biologically active compounds to achieve diagnosis and treatment at the same time. To date, severe limitations compromise the use of nanotheranostic systems as potent nanomaterials are often incompatible with potent biomolecules. Herein we emphasize how a novel type of polymersome clusters loaded with active molecules can be optimized to obtain an efficient nanotheranostic platform. Polymersomes loaded with enzymes and specific dyes, respectively and exposing complementary DNA strands at their external surface formed clusters by means of DNA hybridization. We describe factors at the molecular level and other conditions that need to be optimized at each step of the cluster formation to favor theranostic efficiency.

Combinatorial Strategy for Studying Biochemical Pathways in Double Emulsion Templated Cell-Sized Compartments

Cells rely upon producing enzymes at precise rates and stoichiometry for maximizing functionalities. The reasons for this optimal control are unknown, primarily because of the interconnectivity of the enzymatic cascade effects within multi-step pathways. Here, an elegant strategy for studying such behavior, by controlling segregation/combination of enzymes/metabolites in synthetic cell-sized compartments, while preserving vital cellular elements is presented. Therefore, compartments shaped into polymer GUVs are developed, producing via high-precision double-emulsion microfluidics that enable: i) tight control over the absolute and relative enzymatic contents inside the GUVs, reaching nearly 100% encapsulation and co-encapsulation efficiencies, and ii) functional reconstitution of biopores and membrane proteins in the GUVs polymeric membrane, thus supporting in situ reactions. GUVs equipped with biopores/membrane proteins and loaded with one or more enzymes are arranged in a variety of combinations that allow the study of a three-step cascade in multiple topologies. Due to the spatiotemporal control provided, optimum conditions for decreasing the accumulation of inhibitors are unveiled, and benefited from reactive intermediates to maximize the overall cascade efficiency in compartments. The non-system-specific feature of the novel strategy makes this system an ideal candidate for the development of new synthetic routes as well as for screening natural and more complex pathways.

Segregated Nanocompartments Containing Therapeutic Enzymes and Imaging Compounds within DNA-Zipped Polymersome Clusters for Advanced Nanotheranostic Platform

Nanotheranostics is an emerging field that brings together nanoscale-engineered materials with biological systems providing a combination of therapeutic and diagnostic strategies. However, current theranostic nanoplatforms have serious limitations, mainly due to a mismatch between the physical properties of the selected nanomaterials and their functionalization ease, loading ability, or overall compatibility with bioactive molecules. Herein, a nanotheranostic system is proposed based on nanocompartment clusters composed of two different polymersomes linked together by DNA. Careful design and procedure optimization result in clusters segregating the therapeutic enzyme human Dopa decarboxylase (DDC) and fluorescent probes for the detection unit in distinct but colocalized nanocompartments. The diagnostic compartment provides a twofold function: trackability via dye loading as the imaging component and the ability to attach the cluster construct to the surface of cells. The therapeutic compartment, loaded with active DDC, triggers the cellular expression of a secreted reporter enzyme via production of dopamine and activation of dopaminergic receptors implicated in atherosclerosis. This two-compartment nanotheranostic platform is expected to provide the basis of a new treatment strategy for atherosclerosis, to expand versatility and diversify the types of utilizable active molecules, and thus by extension expand the breadth of attainable applications.

Biomolecule–polymer hybrid compartments: combining the best of both worlds

Recent advances in bio/polymer hybrid compartments in the quest to obtain artificial cells, biosensors and catalytic compartments.

Expression of the inhibitory receptor NKG2A correlates with increased liver and splenic NK cell response to activating receptor engagement

Introduction

Natural killer (NK) cells play a critical role in the innate immune response to viruses and tumors, and comprise a large proportion of the hepatic lymphocyte population. They must remain tolerant to non‐pathogenic antigens while protecting the host from harmful agents. Herein, we investigate how the NK cell response to activation receptor engagement is altered in the liver.

Methods

In this study, we assess IFN‐γ production and degranulation of splenic NK cells and selected subsets of liver NK cells. Flow cytometry (FCM) was used to asses IFN‐γ production and degranulation following stimulation of the NK cells with plate bound antibodies to activating receptors.

Results

We show that smaller percentages of hepatic NK cells produce interferon (IFN)–γ and/or degranulate than do splenic NK cells upon stimulation through activating receptors. We also found that smaller percentages of the circulating NK (cNK) cells in the liver produce IFN‐γ and/or degranulate, compared to the liver tissue resident NK (trNK) cells. In addition, IFN‐γ production by liver cNK cells is not increased in IL‐10 deficient mice, suggesting that their hyporesponsiveness is not mediated by the presence of this anti‐inflammatory cytokine in the hepatic microenvironment. On the other hand, liver trNK cells express higher levels of the inhibitory receptor NKG2A than do cNK cells, correlating with their increased IFN‐γ production and degranulation.

Conclusions

Liver cNK cells’ hyporesponsiveness to stimulation through activating receptors is independent of IL‐10, but correlates with decreased NKG2A expression compared to trNK cells. In addition, we demonstrate that liver NK cells become further hyporesponsive upon continuous engagement of an activating receptor on their cell surface.

Acquisition of activation receptor ligand by trogocytosis renders NK cells hyporesponsive

Because NK cells secrete cytotoxic granules and cytokines that can destroy surrounding cells and help shape the subsequent immune response, they must be kept under tight control. Several mechanisms, at different levels, are in place to control NK cell function. In this study, we describe a novel mechanism regulating NK cell function in which NK cells acquire ligands for activating receptors from target cells by trogocytosis, rendering the NK cells hyporesponsive. In this model, murine NK cells acquire m157, the murine CMV-encoded ligand for the Ly49H-activating receptor, from target cells both in vitro and in vivo. Although acquisition of m157 requires cell-to-cell contact, it does not require the expression of the Ly49H receptor by the NK cell. Acquired m157 protein is expressed on the NK cell surface with a glycosylphosphatidylinisotol linkage and interacts with the Ly49H receptor expressed on the NK cell. This interaction results in blocking the Ly49H receptor that prevents the NK cells from recognizing m157-expressing targets and continuous engagement of the Ly49H-activating receptor, which results in the hyporesponsiveness of the Ly49H(+) NK cell to stimulation through other activating receptors. Thus, NK cell acquisition of a ligand for an activation receptor by trogocytosis renders them hyporesponsive. This mechanism, by which mature NK cell function can be altered, has important implications in regard to how NK cells respond to tumors in specific microenvironments as well as the use of expanded NK cells in treating various malignancies.

U-21,963, a new antibiotic. II. Isolation and characterization

The isolation and characterization of antibiotic U-21,963 are discussed. This compound is a highly unsaturated monobasic acid with the molecular formula C(9)H(7)NO(3). The molecular weight is 177. It is dextrorotatory, [alpha](D) = +138 degrees , and has a pK(a) of 5.1. The ultraviolet absorption spectrum, which showed a maximum at 223 mmu (epsilon = 15,115), indicates unsaturation alpha-beta to the carboxyl group, and the infrared spectrum suggests the presence of an acetylenic group. Explosive decomposition of U-21,963 at 97 C conforms with the latter. U-21,963 is relatively insoluble in water, but readily soluble in ethyl alcohol, acetone, and halogenated hydrocarbons.