Mihai Lomora

Does Membrane Thickness Affect the Transport of Selective Ions Mediated by Ionophores in Synthetic Membranes

Biomimetic polymer nanocompartments (polymersomes) with preserved architecture and ion-selective membrane permeability represent cutting-edge mimics of cellular compartmentalization. Here it is studied whether the membrane thickness affects the functionality of ionophores in respect to the transport of Ca2+ ions in synthetic membranes of polymersomes, which are up to 2.6 times thicker than lipid membranes (5 nm). Selective permeability toward calcium ions is achieved by proper insertion of ionomycin, and demonstrated by using specific fluorescence markers encapsulated in their inner cavities. Preservation of polymersome architecture is shown by a combination of light scattering, transmission electron microscopy, and fluorescence spectroscopy. By using a combination of stopped-flow and fluorescence spectroscopy, it is shown that ionomycin can function and transport calcium ions across polymer membranes with thicknesses in the range 10.7-13.4 nm (7.1-8.9 times larger than the size of the ionophore). Thicker membranes induce a decrease in transport, but do not block it due to the intrinsic flexibility of these synthetic membranes. The design of ion selective biomimetic nanocompartments represents a new path toward the development of cellular ion nanosensors and nano-reactors, in which calcium sensitive biomacromolecules can be triggered for specific biological functions.

Antioxidant functionalized polymer capsules to prevent oxidative stress

Polymeric capsules exhibit significant potential for therapeutic applications as microreactors, where the bio-chemical reactions of interest are efficiently performed in a spatial and time defined manner due to the encapsulation of an active biomolecule (e.g., enzyme) and control over the transfer of reagents and products through the capsular membrane. In this work, catalase loaded polymer capsules functionalized with an external layer of tannic acid (TA) are fabricated via a layer-by-layer approach using calcium carbonate as a sacrificial template. The capsules functionalised with TA exhibit a higher scavenging capacity for hydrogen peroxide and hydroxyl radicals, suggesting that the external layer of TA shows intrinsic antioxidant properties, and represents a valid strategy to increase the overall antioxidant potential of the developed capsules. Additionally, the hydrogen peroxide scavenging capacity of the capsules is enhanced in the presence of the encapsulated catalase. The capsules prevent oxidative stress in an in vitro inflammation model of degenerative disc disease. Moreover, the expression of matrix metalloproteinase-3 (MMP-3), and disintegrin and metalloproteinase with thrombospondin motif-5 (ADAMTS-5), which represents the major proteolytic enzymes in intervertebral disc, are attenuated in the presence of the polymer capsules. This platform technology exhibits potential to reduce oxidative stress, a key modulator in the pathology of a broad range of inflammatory diseases. STATEMENT OF SIGNIFICANCE Oxidative stress damages important cell structures leading to cellular apoptosis and senescence, for numerous disease pathologies including cancer, neurodegeneration or osteoarthritis. Thus, the development of biomaterials-based systems to control oxidative stress has gained an increasing interest. Herein, polymer capsules loaded with catalase and functionalized with an external layer of tannic acid are fabricated, which can efficiently scavenge important reactive oxygen species (i.e., hydroxyl radicals and hydrogen peroxide) and modulate extracellular matrix activity in an in vitro inflammation model of nucleus pulposus. The present work represents accordingly, an important advance in the development and application of polymer capsules with antioxidant properties for the treatment of oxidative stress, which is applicable for multiple inflammatory disease targets.

Artificial Organelles: Reactions inside Protein-Polymer Supramolecular Assemblies.

Reactions inside confined compartments at the nanoscale represent an essential step in the development of complex multifunctional systems to serve as molecular factories. In this respect, the biomimetic approach of combining biomolecules (proteins, enzymes, mimics) with synthetic membranes is an elegant way to create functional nanoreactors, or even simple artificial organelles, that function inside cells after uptake. Functionality is provided by the specificity of the biomolecule(s), whilst the synthetic compartment provides mechanical stability and robustness. The availability of a large variety of biomolecules and synthetic membranes allows the properties and functionality of these reaction spaces to be tailored and adjusted for building complex self-organized systems as the basis for molecular factories.

Bionanoreactors: From Confined Reaction Spaces to Artificial Organelles

Inspired by natural compartments, polymer-based supramolecular assemblies (dendrimers, polymersomes, PICsomes, LBL capsules) have been engineered with a variety of sizes and properties to host biomolecules and thereby yield functional hybrid materials/systems. We present bionanoreactors that are designed by encapsulation/insertion of active compounds (proteins, enzymes, mimics) within the confined space of the assemblies, where these compounds are protected and act in situ. Accessibility to the inner space of the bionanoreactors is a key factor to enable catalytic reactions. For successful biomedical applications, a complex set of requirements regarding bionanoreactors is imposed. Relevant examples of nanoreactors used for the detection and treatment of pathologic conditions are provided, even though they are still in the early stage of research. An overview of this emerging nanoscience-based field and its potential for improved solutions in domains such as medicine are presented.

Therapeutic Applications of Phytoplankton, with an Emphasis on Diatoms and Coccolithophores

Phytoplankton are complex living organisms that have attracted significant interest in the field of biomedicine. One subclass of phytoplankton, the diatoms, produce elegant self‐assembled siliceous architectural features with a complex 3D porous structure. Diatoms are characterized by a distinct 3D architecture of silica cell walls called frustules with a highly ordered nano‐/micropore structure and pattern. Another phytoplankton subclass of interest is the coccolithophore, which produces unique calcium carbonate plates with distinct architectural features called coccoliths. The unique morphological characteristics of coccoliths resembling the shape of a wagon wheel allows a higher surface area, thus an increased amount of immobilized therapeutic agent on their surface compared to a synthetic calcium carbonate microparticle. This review offers a summary of phytoplankton (microalgae) and their potential for application in drug delivery, diagnostics, drug discovery, as molecular factories, and as scaffolds for various therapeutic applications.