Lipid nanoparticles (LNPs) and liposomes are two of the most prevalent yet frequently confused concepts in lipid drug delivery. Many mistakenly equate the two or regard LNPs merely as an “upgraded version” of liposomes, a view that is scientifically inaccurate.
Though both belong to the family of lipid nanocarriers, they differ fundamentally in structure, composition, manufacturing processes and application scenarios. Distinguishing between these two closely related platforms is essential to understanding the evolution of nanoscale delivery technologies.
The Origins: Discovery of Liposomes
In 1964, British scientist Alec D. Bangham first observed that phospholipids spontaneously assemble into closed lipid bilayer vesicles when dispersed in aqueous media. This marked the discovery of liposomes — hollow spherical vesicles enclosed by one or multiple concentric phospholipid bilayers. The aqueous core is surrounded by a hydrophobic lipid bilayer. Thanks to this unique architecture, liposomes can encapsulate water-soluble therapeutics within the inner aqueous compartment and incorporate lipophilic agents into the lipid membrane, enabling the co-delivery of molecules with distinct polarities.
Doxil, the first FDA-approved liposomal drug, was launched in 1995 for ovarian cancer treatment. This PEGylated liposomal formulation encapsulates doxorubicin, effectively reducing the drug’s cardiotoxicity and prolonging its systemic circulation time. Over the subsequent decades, liposomes have been widely adopted in cosmetics, nutraceuticals and general drug delivery, emerging as an early flagship platform in nanomedicine.
Structural Distinction: Hollow Vesicles vs. Dense Solid Particles
The most intuitive difference between liposomes and LNPs lies in their internal structure.
A liposome is essentially a hollow vesicle bounded by phospholipid bilayers, with an aqueous lumen inside, resembling microscopic hollow bubbles. It consists of single or multiple concentric lipid bilayers: polar lipid headgroups face the aqueous phase, while hydrophobic tails aggregate inward. Liposomes vary greatly in size, ranging from tens of nanometers to hundreds of micrometers. Those with a single lipid bilayer are termed unilamellar vesicles, while multilamellar liposomes feature multiple concentric bilayers with an onion-like cross-section.
In contrast, LNPs possess no hollow aqueous core. Instead, they have a compact solid core composed of ionizable lipids and nucleic acids. Within the core, ionizable lipids arrange into inverted micelles that tightly complex negatively charged mRNA molecules.
Industrial-grade LNPs feature tightly controlled particle size, typically around 80 nm in diameter — considerably smaller than most liposomes. This dense solid core serves as a robust physical scaffold to encapsulate and protect nucleic acid payloads.
Compositional Differences: Distinct Lipid Formulations
Structure forms the framework, while lipid composition defines functional performance, creating clear boundaries for their respective applications.
Conventional liposomes are primarily formulated with natural or synthetic neutral phospholipids and cholesterol. Phospholipids constitute the main membrane structure, and cholesterol modulates membrane fluidity and stability. This simple formulation is highly biomimetic, as its lipid bilayer closely resembles natural cell membranes, endowing liposomes with excellent biocompatibility.
LNPs adopt a far more sophisticated and well-defined four-component lipid system: ionizable cationic lipids, helper phospholipids, cholesterol and PEGylated lipids. Among these, ionizable lipids are the core functional component. They become positively charged under acidic conditions, enabling strong electrostatic binding to negatively charged mRNA for high encapsulation efficiency. At physiological pH, they revert to a neutral state, minimizing cytotoxicity and non-specific interactions. The inclusion of ionizable lipids is the definitive feature that differentiates LNPs from conventional liposomes.
Cholesterol content also varies significantly. In the classic liposomal product Doxil, cholesterol accounts for approximately 20% of total lipids. By comparison, LNPs used in mainstream COVID-19 mRNA vaccines contain 38.5% to 42.7% cholesterol. The substantially higher cholesterol content enhances the structural rigidity and physical stability of LNPs.
Technical Evolution: Why the Two Platforms Are Often Confused
Given their fundamental differences, why are LNPs commonly perceived as an upgraded liposome variant? The misunderstanding stems from the historical development of lipid nanocarriers.
Liposomes were discovered in the 1960s, representing the first generation of lipid nanocarriers. The term LNP did not come into widespread use until the 1990s. Based on liposome technology, researchers further developed solid lipid nanoparticles and nanostructured lipid carriers with more complex architectures.
With the rise of nucleic acid therapeutics, traditional liposomes presented critical limitations: composed mainly of neutral lipids, they cannot efficiently encapsulate highly anionic macromolecular nucleic acids. To address this challenge, scientists optimized lipid formulations by introducing ionizable lipids, elevating cholesterol ratios and incorporating PEGylated lipids, eventually establishing the standardized four-component LNP platform. In short, LNPs are not a simple modification of liposomes, but a new-generation delivery platform systematically engineered to overcome the technical bottlenecks of nucleic acid delivery.
Manufacturing and Stability Profiles
Liposomes and LNPs also diverge greatly in production techniques and stability performance.
Liposomes are typically fabricated via sonication or extrusion to reduce particle size and narrow size distribution. The general workflow involves forming large lipid aggregates first, followed by physical fragmentation to obtain uniform vesicles.
LNPs are predominantly produced via microfluidic rapid mixing. Lipid solutions in ethanol are mixed with aqueous mRNA solutions within microchannels at millisecond-scale speed, allowing one-step self-assembly and precise particle size control.
In terms of physical stability, liposomes are thermodynamically prone to membrane fusion and payload leakage during long-term storage due to their hollow vesicular structure. The dense solid core of LNPs delivers superior physical stability. However, the compact matrix with minimal free water results in a narrower process window for stabilization techniques such as lyophilization, compared with liposomes.
Application Segmentation: Respective Strengths
Their unique physicochemical properties have led liposomes and LNPs to distinct application landscapes.
Benefiting from their simple bilayer structure and mature manufacturing processes, liposomes are widely used in cosmetics, nutraceuticals and conventional drug delivery, and are particularly well-suited for encapsulating small-molecule chemical drugs.
By virtue of pH-tunable ionizable lipids, refined multi-lipid formulations and dense solid cores, LNPs have become the gold standard for non-viral delivery of nucleic acid therapeutics. Onpattro, the first LNP-formulated siRNA drug, gained regulatory approval in 2018. During the COVID-19 pandemic, mRNA vaccines based on LNP technology achieved emergency use authorization within just one year. To date, LNPs remain the most advanced and clinically proven non-viral delivery system for nucleic acid medicines.
Conclusion
From the initial microscopic observation in 1964 to large-scale clinical deployment during the global pandemic, liposomes and LNPs have each played pivotal roles in pharmaceutical development. As members of the lipid nanocarrier family, liposomes are hollow bilayer vesicles composed of phospholipids and cholesterol, while LNPs are compact solid-core particles formulated with ionizable lipids and three other auxiliary lipids in precise ratios.
To draw an analogy: liposomes act as versatile universal carriers optimized for small-molecule drugs, whereas LNPs are precision-engineered delivery systems purpose-built to solve the unique challenges of nucleic acid delivery. The gap between the two platforms is not merely generational iteration, but a major leap in delivery science — developing novel tools to safely transport fragile macromolecular nucleic acids into target cells. Today, liposomes and LNPs continue to advance independently in their respective dominant fields, jointly shaping the full spectrum of modern lipid-based nanodelivery technology.
