228 research outputs found
Review of structural design guiding the development of lipid nanoparticles for nucleic acid delivery
Lipid nanoparticles (LNPs) are the most versatile and successful gene delivery systems, notably highlighted by their use in vaccines against COVID-19. LNPs have a well-defined core-shell structure, each region with its own distinctive compositions, suited for a wide range of in vivo delivery applications. Here, we discuss how a detailed knowledge of LNP structure can guide LNP formulation to improve the efficiency of delivery of their nucleic acid payload. Perspectives are detailed on how LNP structural design can guide more efficient nucleic acid transfection. Views on key physical characterization techniques needed for such developments are outlined including opinions on biophysical approaches both correlating structure with functionality in biological fluids and improving their ability to escape the endosome and deliver they payload
Nucleic Acid-Loaded Lipid Nanoparticle Interactions with Model Endosomal Membranes
[Image: see text] Lipid nanoparticles (LNPs) are important delivery systems for RNA-based therapeutics, yet the mechanism of their interaction with endosomal membranes remains unclear. Here, the interactions of nucleic acid-loaded LNPs that contain an ionizable lipid with models of the early and late endosomal membranes are studied, for the first time, using different reflectometry techniques. Novel insight is provided with respect to the subphase pH, the stage of the endosome, and the nature of the nucleic acid cargo. It is found that the insertion of lipids from the LNPs into the model membrane is greatest at pH 6.5 and 5.5, whereas at higher pH, lipid insertion is suppressed with evidence instead for the binding of intact LNPs, demonstrating the importance of the pH in the fusion of LNPs undergoing the endosomal pathway. Furthermore, and independently of the pH, the effect of the early- versus late-stage endosomal models is minimal, suggesting that the increased fluidity and anionic nature of the late endosome has little effect on the extent of LNP interaction. Last, there is greater nucleic acid delivery from LNPs containing mRNA than Poly(A), indicating that the extent of interaction can be tuned according to the nature of the nucleic acid cargo. Such new information on the relative impact of factors influencing nucleic acid delivery by LNP interactions with endosomal membranes is important in the design and tuning of vehicles with improved nucleic acid delivery capacities
Understanding and optimising the transfection of lipopolyplexes formulated in saline: the effects of peptide and serum
Lipopolyplexes (LPDs) are of considerable interest for use as gene delivery vehicles. Here LPDs have been prepared from cationic vesicles (composed of a 1 : 1 molar ratio of DOTMA with the neutral helper lipid, DOPE), singly branched cationic peptides and plasmid DNA. All peptides contained a linker sequence (cleaved by endosomal furin) attached to a targeting sequence selected to bind human airway epithelial cells and mediate gene delivery. The current study investigates the effects of novel Arg-containing cationic peptide sequences on the biophysical and transfection properties of LPDs. Mixed His/Arg cationic peptides were of particular interest, as these sequences have not been previously used in LPD formulations. Lengthening the number of cationic residues in a homopolymer from 6 to 12 in each branch reduced transfection using LPDs, most likely due to increased DNA compaction hindering the release of pDNA within the target cell. Furthermore, LPDs containing mixed Arg-containing peptides, particularly an alternating Arg/His sequence exhibited an increase in transfection, probably because of their optimal ability to complex and subsequently release pDNA. To confer stability in serum, LPDs were prepared in 0.12 M sodium chloride solution (as opposed to the more commonly used water) yielding multilamellar LPDs with very high levels of size reproducibility and DNA protection, especially when compared to the (unilamellar) LPDs formed in water. Significantly for the clinical applications of the LPDs, those prepared in the presence of sodium chloride retained high levels of transfection in the presence of media supplemented with fetal bovine serum. This work therefore represents a significant advance for the optimisation of LPD formulation for gene delivery, under physiologically relevant conditions, in vivo
Polyelectrolyte/surfactant films: from 2D to 3D structural control
Reversible control of the 3D structure of polyelectrolyte/surfactant films at the air/water interface is showcased. A recently discovered mechanism is exploited to form highly efficient, stable and biocompatible films by spreading aggregates composed of poly-L-lysine and sodium dodecyl sulfate on the surface of water. Reversible control of: (1) the surface monolayer coverage, (2) the switching on or off discrete extended structures, and (3) the extended structure coverage is demonstrated for the first time. The intricacy by which the film structures can be controlled is unprecedented and opens exciting potential to optimize film properties by chemical design for novel biomedical transfer applications.We thank the Institut Laue-Langevin for beam time on FIGARO (DOIs: https://doi.org/10.5291/ILL-DATA.9-12-614 and https://doi.org/10.5291/ILL-DATA.9-12-631), Simon Wood for technical assistance and the Partnership for Soft Condensed Matter (PSCM) for lab support. IV acknowledges the financial support from the Hungarian National Research, Development and Innovation Office (NKFIH K116629). AM acknowledges the financial support from MICINN under grant PID2021-129054NA-I00 and the IKUR Strategy of the Basque Government.Peer reviewe
Assessing molecular simulation for the analysis of lipid monolayer reflectometry
Using molecular simulation to aid in the analysis of neutron reflectometry
measurements is commonplace. However, reflectometry is a tool to probe
large-scale structures, and therefore the use of all-atom simulation may be
irrelevant. This work presents the first direct comparison between the
reflectometry profiles obtained from different all-atom and coarse-grained
molecular dynamics simulations. These are compared with a traditional model
layer structure analysis method to determine the minimum simulation resolution
required to accurately reproduce experimental data. We find that systematic
limits reduce the efficacy of the MARTINI potential model, while the Berger
united-atom and Slipids all-atom potential models agree similarly well with the
experimental data. The model layer structure gives the best agreement, however,
the higher resolution simulation-dependent methods produce an agreement that is
comparable. Finally, we use the atomistic simulation to advise on possible
improvements that may be offered to the model layer structures, creating a more
realistic monolayer model.Comment: Electronic Supplementary Information (ESI) available: All
analysis/plotting scripts and figure files, allowing for a fully
reproducible, and automated, analysis workflow for the work presented is
available at \url{https://github.com/arm61/sim_vs_trad} (DOI:
10.5281/zenodo.2600729) under a CC BY-SA 4.0 licens
The Community Climate System Model version 4
Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 24 (2011): 4973–4991, doi:10.1175/2011JCLI4083.1.The fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all CCSM components, and documents fully coupled preindustrial control runs compared to the previous version, CCSM3. Using the standard atmosphere and land resolution of 1° results in the sea surface temperature biases in the major upwelling regions being comparable to the 1.4°-resolution CCSM3. Two changes to the deep convection scheme in the atmosphere component result in CCSM4 producing El Niño–Southern Oscillation variability with a much more realistic frequency distribution than in CCSM3, although the amplitude is too large compared to observations. These changes also improve the Madden–Julian oscillation and the frequency distribution of tropical precipitation. A new overflow parameterization in the ocean component leads to an improved simulation of the Gulf Stream path and the North Atlantic Ocean meridional overturning circulation. Changes to the CCSM4 land component lead to a much improved annual cycle of water storage, especially in the tropics. The CCSM4 sea ice component uses much more realistic albedos than CCSM3, and for several reasons the Arctic sea ice concentration is improved in CCSM4. An ensemble of twentieth-century simulations produces a good match to the observed September Arctic sea ice extent from 1979 to 2005. The CCSM4 ensemble mean increase in globally averaged surface temperature between 1850 and 2005 is larger than the observed increase by about 0.4°C. This is consistent with the fact that CCSM4 does not include a representation of the indirect effects of aerosols, although other factors may come into play. The CCSM4 still has significant biases, such as the mean precipitation distribution in the tropical Pacific Ocean, too much low cloud in the Arctic, and the latitudinal distributions of shortwave and longwave cloud forcings.National
Science Foundation, which sponsors NCAR and the
CCSM Project. The project is also sponsored by the U.S.
Department of Energy (DOE). Thanks are also due to
the many other software engineers and scientists who
worked on developing CCSM4, and to the Computational
and Information Systems Laboratory at NCAR,
which provided the computing resources through the
Climate Simulation Laboratory. Hunke was supported
within theClimate, Ocean and Sea Ice Modeling project at
Los Alamos National Laboratory, which is funded by the
Biological and Environmental Research division of the
DOE Office of Science. The Los Alamos National Laboratory
is operated by theDOENationalNuclear Security
Administration under Contract DE-AC52-06NA25396.
Raschwas supported by theDOEOffice of Science, Earth
System Modeling Program, which is part of the DOE
Climate Change Research Program. The Pacific Northwest
National Laboratory is operated forDOEbyBattelle
Memorial Institute under Contract DE-AC06-76RLO
1830. Worley was supported by the Climate Change Research
Division of the Office of Biological and Environmental
Research and by the Office ofAdvanced Scientific
Computing Research, both in the DOE Office of Science,
under Contract DE-AC05-00OR22725 with UT-Batelle,
LLC
Tuning a gene delivery vector: the role of peptide sequence and peptide branching in delivering of DNA and siRNA to the cytoplasm
Tuning a gene delivery vector: the role of peptide sequence and peptide branching in delivering of DNA and siRNA to the cytoplas
Novel cationic lipopolyplexes as gene therapy vectors
A major obstacle in the development of gene therapy is delivery of therapeutic genes to the desired cell/tissue. The objective of our study is to use a non-viral ternary system (lipopolyplexes) to encapsulate and deliver therapeutic DNA. Our lipopolyplexes comprise a glycerol-based cytofectin, a targeting peptide and plasmid DNA. Novel derivatives of the cationic lipids DOTMA and DOTAP have been synthesized and tested in a breast cancer cell line. A range of branched cationic peptides varying in number of residues, composition and linker to a targeting head group were also designed and prepared. The bio-physical studies demonstrated that all LPD complexes were positively charged, small (60-80 nm) and were shown to effectively condense DNA. Gel assays showed which peptides were able to protect DNA more effectively and gave high transfection efficiency. Further studies are underway investigating these systems in siRNA delivery
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