Capillary electrophoresis method to determine siRNA complexation with cationic liposomes

Poly(N-methyl-N-vinylacetamide): A Strong Alternative to PEG for Lipid-Based Nanocarriers Delivering siRNA

Lipid-based nanocarriers have demonstrated high interest in delivering genetic material, exemplified by the success of Onpattro and COVID-19 vaccines. While PEGylation imparts stealth properties, it hampers cellular uptake and endosomal escape, and may trigger adverse reactions like accelerated blood clearance (ABC) and hypersensitivity reactions (HSR). This work highlights the great potential of amphiphilic poly(N-methyl-N-vinylacetamide) (PNMVA) derivatives as alternatives to lipid-PEG for siRNA delivery. PNMVA compounds with different degrees of polymerization and hydrophobic segments, are synthesized. Among them, DSPE (1,2-distearoyl-sn-glycero-3-phosphoethanolamine)-PNMVA efficiently integrates into lipoplexes and LNP membranes and prevents protein corona formation around these lipid carriers, exhibiting stealth properties comparable to DSPE-PEG. However, unlike DSPE-PEG, DSPE-PNMVA24 shows no adverse impact on lipoplexes cell uptake and endosomal escape. In in vivo study with mice, DSPE-PNMVA24 lipoplexes demonstrate no liver accumulation, indicating good stealth properties, extended circulation time after a second dose, reduced immunological reaction, and no systemic pro-inflammatory response. Safety of DSPE-PNMVA24 is confirmed at the cellular level and in animal models of zebrafish and mice. Overall, DSPE-PNMVA is an advantageous substitute to DSPE-PEG for siRNA delivery, offering comparable stealth and toxicity properties while improving efficacy of the lipid-based carriers by minimizing the dilemma effect and reducing immunological reactions, meaning no ABC or HSR effects.

Poly(vinyl pyrrolidone) derivatives as PEG alternatives for stealth, non-toxic and less immunogenic siRNA-containing lipoplex delivery

The recent approval of Onpattro® and COVID-19 vaccines has highlighted the value of lipid nanoparticles (LNPs) for the delivery of genetic material. If it is known that PEGylation is crucial to confer stealth properties to LNPs, it is also known that PEGylation is responsible for the decrease of the cellular uptake and endosomal escape and for the production of anti-PEG antibodies inducing accelerated blood clearance (ABC) and hypersensitivity reactions. Today, the development of PEG alternatives is crucial. Poly(N-vinyl pyrrolidone) (PNVP) has shown promising results for liposome decoration but has never been tested for the delivery of nucleic acids. Our aim is to develop a series of amphiphilic PNVP compounds to replace lipids-PEG for the post-insertion of lipoplexes dedicated to siRNA delivery. PNVP compounds with different degrees of polymerization and hydrophobic segments, such as octadecyl, dioctadecyl and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE), were generated. Based on the physicochemical properties and the efficiency to reduce protein corona formation, we showed that the DSPE segment is essential for the integration into the lipoplexes. Lipoplexes post-grafted with 15% DSPE-PNVP30 resulted in gene silencing efficiency close to that of lipoplexes grafted with 15% DSPE-PEG. Finally, an in vivo study in mice confirmed the stealth properties of DSPE-PNVP30 lipoplexes as well as a lower immune response ABC effect compared to DSPE-PEG lipoplexes. Furthermore, we showed a lower immune response after the second injection with DSPE-PNVP30 lipoplexes compared to DSPE-PEG lipoplexes. All these observations suggest that DSPE-PNVP30 appears to be a promising alternative to PEG, with no toxicity, good stealth properties and lower immunological response.

Characterization of the Interaction of Polymeric Micelles with siRNA: A Combined Experimental and Molecular Dynamics Study

The simulation of large molecular systems remains a daunting challenge, which justifies the exploration of novel methodologies to keep computers as an ideal companion tool for everyday laboratory work. Whole micelles, bigger than 20 nm in size, formed by the self-assembly of hundreds of copolymers containing more than 50 repeating units, have until now rarely been simulated, due to a lack of computational power. Therefore, a flexible amphiphilic triblock copolymer (mPEG45-α-PLL10-PLA25) containing a total of 80 repeating units, has been emulated and synthesized to embody compactified nanoconstructs of over 900 assembled copolymers, sized between 80 and 100 nm, for siRNA complexing purposes. In this study, the tailored triblock copolymers containing a controlled number of amino groups, were used as a support model to address the binding behavior of STAT3-siRNA, in the formation of micelleplexes. Since increasingly complex drug delivery systems require an ever more optimized physicochemical characterization, a converging description has been implemented by a combination of experimentation and computational simulations. The computational data were advantageous in allowing for the assumption of an optimal N/P ratio favoring both conformational rigidifications of STAT3-siRNA with low competitive phenomena at the binding sites of the micellar carriers. These calculations were consistent with the experimental data showing that an N/P ratio of 1.5 resulted in a sufficient amount of complexed STAT3-siRNA with an electrical potential at the slipping plane of the nanopharmaceuticals, close to the charge neutralization.

Analysis of therapeutic nucleic acids by capillary electrophoresis

Nucleic acids are getting increased attention to fulfill unmet medical needs. The past five years have seen more than ten FDA approvals of nucleic acid based therapeutics. New analytical challenges have been posed in discovery, characterization, quality control and bioanalysis of therapeutic nucleic acids. Capillary electrophoresis (CE) has proven to be an efficient separation technique and has been widely used for analyzing oligonucleotides and nucleic acids. This review discusses the recent technical advances of CE in nucleic acid analysis such as polymeric matrices, separation conditions and detection methods, and the applications of CE to various therapeutic nucleic acids including antisense oligonucleotide (ASO), small interfering ribonucleic acid (siRNA), messenger RNA (mRNA), gene editing tools such as clustered regularly interspaced short palindromic repeats (CRISPR)-based gene and cell therapy, and other nucleic acid related therapeutics.

Moment theory for the analytical determination of rate constants for solute permeation at the interface of spherical molecular aggregates

Moment equations were developed on the basis of the Einstein equation for diffusion and the random walk model to analytically determine the rate constant for the interfacial solute permeation from a bulk solvent into molecular aggregates (k_in ) and the inverse rate constant from the molecular aggregates to the bulk solvent (k_out ). The moment equations were in good agreement with those derived in a different manner. To demonstrate their effectiveness in one concrete example, the moment equations were used to analytically determine the values of k_in and k_out of three electrically neutral solutes, i.e. resorcinol, phenol, and nitrobenzene, from the first absolute (μ_1A ) and second central (μ_2C ) moments of their elution peaks, as measured by electrokinetic chromatography (EKC), in which the sodium dodecyl sulfate (SDS) micelles were used as a pseudostationary phase. The values of k_in and k_out should be determined with no chemical modifications and no physical action with the molecular aggregates because they are dynamic systems formed through weak interactions between the components. The moment analysis of the elution peak profiles measured by EKC is effective to unambiguously determine k_in , k_out , and the partition equilibrium constant (k_in /k_out ) under appropriate experimental conditions.

Moment analysis for mass transfer kinetics at the interface of spherical molecular aggregates

New moment equations were developed on the basis of the principle of relativity for explaining some characteristics of elution peaks measured by electrokinetic chromatography (EKC) using spherical molecular aggregates. Basic equations representing mass balance and mass transfer kinetics in EKC system in a Galilean coordinate system S were transformed to those in another coordinate system S', which imaginarily moved with respect to S. Moment equations for EKC peaks in S' in the time domain were derived from the analytical solution of the modified basic equations in the Laplace domain. Moment equations for EKC peaks in S were derived from those in S' by the inverse Galilean transformation. The moment equations were used to the re-analysis of EKC data previously measured. The values of permeation rate constants of thymol at the interface of sodium dodecylsulfate micelles were fairly in agreement with those determined in a previous study. The moment equations were also used to the numerical simulation of elution peaks in EKC systems. The influence of some experimental parameters on elution peak profiles was quantitatively analyzed. The moment equations are useful for determining the rate constants of interfacial solute permeation from elution peak profiles measured by EKC.