Surface Modification of Lipid-Based Nanoparticles.

There is a growing interest in the development of lipid-based nanocarriers for multiple purposes, including the recent increase of these nanocarriers as vaccine components during the COVID-19 pandemic. The number of studies that involve the surface modification of nanocarriers to improve their performance (increase the delivery of a therapeutic to its target site with less off-site accumulation) is enormous. The present review aims to provide an overview of various methods associated with lipid nanoparticle grafting, including techniques used to separate grafted nanoparticles from unbound ligands or to characterize grafted nanoparticles. We also provide a critical perspective on the usefulness and true impact of these modifications on overcoming different biological barriers, with our prediction on what to expect in the near future in this field.

Impact of anti-PDGFRα antibody surface functionalization on LNC uptake by oligodendrocyte progenitor cells.

Impairment of oligodendrocyte progenitor cell (OPC) differentiation into oligodendrocytes and chronic inflammation are key determinants of poor remyelination observed in diseases such as multiple sclerosis. For many pro-myelinating molecules, the therapeutic potential is hindered by poor solubility or limited access to the targeted cells. A promising approach to improve the delivery of those molecules to OPC is to encapsulate them in functionalized Lipid Nanocapsules (LNC). We aimed to develop the first OPC-targeting LNC, by grafting an anti-PDGFRα antibody on the surface of the LNC using several strategies and evaluating the interaction with PDGFRα via ELISA. We found that only site-selective click-chemistry grafting maintained anti-PDGFRα/PDGFRα association, which was confirmed in vitro on primary rat OPC. In conclusion, we demonstrated that it was possible to produce anti-PDGFRα functionalized LNC, we confirmed the antibody's ability to recognize its receptor after grafting and we optimized techniques to characterize antibody functionalized LNC.

Extracellular vesicles for the treatment of central nervous system diseases.

The interest in extracellular vesicles (EVs) increased during the last decade. It is now established that these vesicles play a role in the pathogenesis of central nervous system diseases (CNS), which explains why they are studied as biomarkers in these pathologies. On the other hand, EVs can also present therapeutic properties, often similar to their parent cells, as observed with mesenchymal stem cell-derived EVs. They can then be used as therapeutics, alone or combined with a bioactive molecule, for the treatment of CNS diseases, as they can cross the blood-brain barrier more easily than synthetic nanomedicines and are less immunogenic. A few clinical trials are currently on-going but there are still challenges to overcome for further clinical translation such as the scale-up of the production, the lack of standardization for isolation and characterization methods and the low encapsulation efficiency.

Retinoic acid-loaded NFL-lipid nanocapsules promote oligodendrogenesis in focal white matter lesion.

Neural stem cells (NSC) are located in restricted areas of the central nervous system where they self-renew or differentiate into neurons, astrocytes or oligodendrocytes. The stimulation of endogenous NSC differentiation is one of the most promising therapeutic approaches to restore neurological function in patients affected by neurodegenerative diseases. Endogenous NSC of the subventricular zone (SVZ) can be selectively targeted by lipid nanocapsules (LNC) coated with the peptide NFLTBS.40-63 (NFL-LNC) after intra-lateral ventricular injection in the brain. NFL-LNC can potentially deliver active compounds to SVZ-NSC and thus promote their differentiation to treat neurodegenerative diseases. The aim of this work was to induce endogenous NSC differentiation by specifically delivering retinoic acid (RA) to SVZ-NSC via NFL-LNC. RA was successfully encapsulated into NFL-LNC and RA-NFL-LNC were incubated with primary rat SVZ-NSC. In vitro, RA-NFL-LNC decreased the number of nestin+ (NSC marker) cells and neurospheres compared to controls and increased the number of GalC+ (oligodendrocytic marker) cells. Then, RA-NFL-LNC were injected in the right lateral ventricle of a lysolecithin-induced rat focal white matter lesion model to evaluate their impact on oligodendrocyte repopulation and remyelination. RA-NFL-LNC significantly increased the percentage of mature oligodendrocytes, stimulating oligodendrogenesis, nearly to the pre-lesion levels. Thus, RA-NFL-LNC represent a promising nanomedicine to be further investigated in the treatment of demyelinating diseases.

Central nervous system regeneration is driven by microglia necroptosis and repopulation.

Failed regeneration of CNS myelin contributes to clinical decline in neuroinflammatory and neurodegenerative diseases, for which there is an unmet therapeutic need. Here we reveal that efficient remyelination requires death of proinflammatory microglia followed by repopulation to a pro-regenerative state. We propose that impaired microglia death and/or repopulation may underpin dysregulated microglia activation in neurological diseases, and we reveal therapeutic targets to promote white matter regeneration.