Tuning the corona-core ratio of polyplex micelles for selective oligonucleotide delivery to hepatocytes or hepatic immune cells

Targeted delivery of oligonucleotides or small molecular drugs to hepatocytes, the liver's parenchymal cells, is challenging without targeting moiety due to the highly efficient mononuclear phagocyte system (MPS) of the liver. The MPS comprises Kupffer cells and specialized sinusoidal endothelial cells, efficiently clearing nanocarriers regardless of their size and surface properties. Physiologically, this non-parenchymal shield protects hepatocytes; however, these local barriers must be overcome for drug delivery. Nanocarrier structural properties strongly influence tissue penetration, in vivo pharmacokinetics, and biodistribution profile. Here we demonstrate the in vivo biodistribution of polyplex micelles formed by polyion complexation of short interfering (si)RNA with modified poly(ethylene glycol)-block-poly(allyl glycidyl ether) (PEG-b-PAGE) diblock copolymer that carries amino moieties in the side chain. The ratio between PEG corona and siRNA complexed PAGE core of polyplex micelles was chemically varied by altering the degree of polymerization of PAGE. Applying Raman-spectroscopy and dynamic in silico modeling on the polyplex micelles, we determined the corona-core ratio (CCR) and visualized the possible micellar structure with varying CCR. The results for this model system reveal that polyplex micelles with higher CCR, i.e., better PEG coverage, exclusively accumulate and thus allow passive cell-type-specific targeting towards hepatocytes, overcoming the macrophage-rich reticuloendothelial barrier of the liver

Atomistic Descriptors for Machine Learning Models of Solubility Parameters for Small Molecules and Polymers

Descriptors derived from atomic structure and quantum chemical calculations for small molecules representing polymer repeat elements were evaluated for machine learning models to predict the Hildebrand solubility parameters of the corresponding polymers. Since reliable cohesive energy density data and solubility parameters for polymers are difficult to obtain, the experimental heat of vaporization ΔHvap of a set of small molecules was used as a proxy property to evaluate the descriptors. Using the atomistic descriptors, the multilinear regression model showed good accuracy in predicting ΔHvap of the small-molecule set, with a mean absolute error of 2.63 kJ/mol for training and 3.61 kJ/mol for cross-validation. Kernel ridge regression showed similar performance for the small-molecule training set but slightly worse accuracy for the prediction of ΔHvap of molecules representing repeating polymer elements. The Hildebrand solubility parameters of the polymers derived from the atomistic descriptors of the repeating polymer elements showed good correlation with values from the CROW polymer database

Mycobacterium tuberculosis PE_PGRS19 Induces Pyroptosis through a Non-Classical Caspase-11/GSDMD Pathway in Macrophages

The PE/PPE protein family commonly exists in pathogenic species, such as Mycobacterium tuberculosis, suggesting a role in virulence and its maintenance. However, the exact role of most PE/PPE proteins in host–pathogen interactions remains unknown. Here, we constructed a recombinant Mycobacterium smegmatis expressing M. tuberculosis PE_PGRS19 (Ms_PE_PGRS19) and found that PE_PGRS19 overexpression resulted in accelerated bacterial growth in vitro, increased bacterial survival in macrophages, and enhanced cell damage capacity. Ms_PE_PGRS19 also induced the expression of pro-inflammatory cytokines, such as IL-6, TNF-α, IL-1β, and IL-18. Furthermore, we demonstrated that Ms_PE_PGRS19 induced cell pyroptosis by cleaving caspase-11 via a non-classical pathway rather than caspase-1 activation and further inducing the cleavage of gasdermin D, which led to the release of IL-1β and IL-18. To the best of our current knowledge, this is the first report of a PE/PPE family protein activating cell pyroptosis via a non-classical pathway, which expands the knowledge on PE/PPE protein functions, and these pathogenic factors involved in bacterial survival and spread could be potential drug targets for anti-tuberculosis therapy