In vaccine development of oncology and infectious diseases, Lipid nanoparticles (LNP) are increasingly being utilized in the burgeoning fields of mRNA and replicon-based therapeutics. It has been applied for therapeutic protein replacement strategies and gene editing approaches.
The LNP used today for nucleic acid (NA) delivery is quite different from classical liposomes. Perhaps one of the most distinctive differences lies in the fact that LNP does not display a lipid bilayer surrounding an aqueous core. Additionally, the current-day LNP does not form particles with nucleic acid payloads driven by electrostatic complexation, nor do they need to balance the charges of constituent compounds for effective and efficient delivery into a cell.
Fig.1 Mechanism of action of the LNP formulation following systemic administration. (Samaridou, 2020)
The ionizable lipid is a critical component of LNP and a major determinant of LNP potency. The ionizable nature promotes the formation of particles with an encapsulated payload, as opposed to complexation.
Fig.2 Ionizable lipids of note. (Samaridou, 2020)
PEG-lipids are another important LNP component that plays several roles. Their structure consists of two domains: a hydrophilic PEG-polymer conjugated to a hydrophobic lipid anchor. They are situated at the surface of lipid particles, with the lipid domain buried down into the particle and the PEG domain extending out from the surface.
LNP have employed phospholipids and cholesterol for their helpful contributions to the structural integrity and phase transition behavior of the LNP. This in turn influences the fusogenicity of the particles. They are required to ensure appropriate encapsulation of the NA payload and stability over time. Additionally, the presence of phospholipid aids in the workup of formulation via tangential flow ultrafiltration (TFU).
Fig.3 Schematic representation of LNP structure. (Samaridou, 2020)
Laser diffractometry (LD) is performed to yield the volume distribution of the particles. The size distribution of the nanoparticle population is measured with the polydispersity index. An outstanding feature of nanoparticles is the increase in saturation solubility and consequently an increase in the dissolution velocity of the compounds.
Along with particle size, dispersity, and composition, the morphology and ultrastructure are important properties of nanoparticles and their formulations which can control properties such as encapsulation efficiency.
The surface characteristics of colloidal particles have a significant impact on their in vivo behavior and stability. Electrostatic and steric repulsion play an important role in the stabilization of colloidal systems.
The release properties of lipid nanoparticles essentially rely upon the solid-state of the particles. Crystalline solid particles are obtained when colloidal emulsion droplets are cooled below the lipid's critical crystallization temperature. The crystallization tendency of nanoparticles can be further suppressed by the incorporation of drugs.
The equilibrium of the complex colloidal system is often more fragile than the structure of the nanoparticles themselves, and therefore more commonly altered by formulation conditions such as the pre-treatment involved.
Critical quality attributes characterization plays an undoubtedly important role in lipid nanoparticle-formulated drugs development. Stable nanoparticle formulations should retain the loaded drug during their in vitro storage and in vivo circulation before delivering the drug to the target.
The lipids are known to influence drug encapsulation, particle morphology, and drug release properties, as do other excipients such as surfactants, water, and drug molecules. The stability of lipid nanoparticles and the incorporated drug ensures improved drug efficacy.
Appropriate characterization of lipid nanoparticle formulations is required to allow for the development of dispersions with the desired properties for the intended application. Creative Biolabs offers well-established and innovative one-stop-shop solutions for the delivery vehicle of mRNA. We will find a way to manage both the entire supply chain and the entire value chain to meet your needs. Please contact us for more information and a detailed quote.
Reference
