Liposomal delivery is a method of packaging drugs, nutrients, or other active compounds inside tiny hollow spheres made of the same type of fat molecules that form your cell membranes. These spheres, called liposomes, protect their cargo from being broken down in the body and help shuttle it to where it needs to go. The concept dates back to the early 1960s, and today liposomal formulations are used in cancer treatment, antifungal therapy, vaccines, supplements, and skincare. The technology sounds futuristic, but the underlying principle is surprisingly simple: wrap the payload in something the body already recognizes.
How a Liposome Is Built
A liposome is a spherical vesicle made of one or more layers of phospholipids surrounding a water-filled core. Phospholipids are the same molecules that make up the outer membrane of every cell in your body. Each phospholipid has a water-loving head and a water-repelling tail. When you mix these molecules in water, they spontaneously arrange themselves into a double layer, tails facing inward, heads facing outward, forming a sealed bubble. This happens without any special equipment or chemical tricks; it is a natural behavior of these molecules, driven by the same physics that makes oil and water separate.1Angewandte Chemie. Vesicle Origami: Cuboid Phospholipid Vesicles Formed by Template‐Free Self‐Assembly
The resulting structure has two distinct compartments. The water-filled interior can hold water-soluble substances like many conventional drugs or vitamin C. The fatty bilayer itself can hold fat-soluble substances. This dual-compartment architecture is what makes liposomes so versatile as carriers: they can transport compounds that dissolve in water, compounds that dissolve in fat, or both at the same time.2Next Nanotechnology. Liposomes for drug delivery: Classification, therapeutic applications, and limitations Cholesterol is often mixed in with the phospholipids to stiffen the membrane and prevent it from leaking its contents too quickly.
Liposomes range in size from about 20 nanometers to roughly 1,000 nanometers across.3ACS Publications. Lipid Nanoparticles: From Liposomes to mRNA Vaccine Delivery, a Landscape of Research Diversity and Advancement For perspective, a human red blood cell is about 7,000 nanometers wide, so even the largest liposomes are far smaller. Single-layer liposomes are the workhorses of drug delivery because their size and simplicity make them easier to manufacture consistently. Multi-layer liposomes, which look a bit like onions with concentric shells, can carry more drug but are harder to control.
How the Body Handles Liposomes
Once injected into the bloodstream, a plain liposome faces an immediate problem: the immune system treats it as a foreign particle. Specialized white blood cells in the liver and spleen recognize the liposome’s surface and swallow it within minutes. This rapid clearance was one of the biggest early obstacles to making liposomal drugs work in practice.
The breakthrough came with PEGylation, the process of attaching chains of polyethylene glycol (PEG) to the liposome’s outer surface. PEG is a water-loving polymer that creates a kind of molecular brush around the liposome, making it slippery and harder for immune cells to grab. PEGylated liposomes, often called “stealth” liposomes, circulate in the blood far longer than uncoated ones.4PubMed Central. Stealth liposomes: review of the basic science, rationale, and clinical applications, existing and potential That extended circulation time is not just a technical curiosity; it dramatically increases the chance that the liposome reaches its target tissue before being cleared away.5PubMed. Evasion of the accelerated blood clearance phenomenon by polysarcosine coating of liposomes
Getting Inside Cells
Delivering a drug to the right neighborhood in the body is only half the job. The drug often needs to get inside cells to do its work. Liposomes enter cells through several routes, and which one dominates depends on the liposome’s surface chemistry and charge.
The most common pathway for negatively charged liposomes is endocytosis, the same process cells use to take in nutrients. The cell membrane wraps around the liposome and pulls it into a small internal compartment. Inside that compartment, the environment turns acidic, which can destabilize the liposome and release its contents into the cell.6Cell. Endocytosis of liposomes and intracellular fate of encapsulated molecules: Encounter with a low pH compartment after internalization in coated vesicles Positively charged (cationic) liposomes also enter cells through endocytosis; their fusion with the cell membrane, which was once assumed to happen at the cell surface, actually occurs mainly after the liposome has already been pulled inside.7PubMed. Fusion of cationic liposomes with mammalian cells occurs after endocytosis
There are exceptions. Researchers have engineered liposomes with special peptides on their surface that can fuse directly with the cell membrane, bypassing the endocytosis pathway almost entirely and dumping their cargo straight into the cell interior.8PubMed Central. Drug Delivery via Cell Membrane Fusion Using Lipopeptide Modified Liposomes This approach is still largely experimental, but it hints at how much control designers can exert over where and how a liposome releases its payload.
Passive and Active Targeting
One of the most clinically useful features of liposomal delivery is the ability to concentrate drugs in specific tissues rather than flooding the entire body. This happens through two broad strategies.
Passive targeting relies on a phenomenon seen in many solid tumors. Tumor blood vessels tend to be leaky and poorly formed, with gaps large enough for nanosized particles to slip through. Once inside the tumor, these particles tend to stay because the tumor’s lymphatic drainage is poor. This is called the enhanced permeability and retention (EPR) effect, and it is the reason stealth liposomes, which circulate long enough to encounter those leaky vessels, accumulate preferentially in tumors.9PubMed Central. Tumor targeting via EPR: Strategies to enhance patient responses Longer circulation from PEGylation amplifies this effect by giving the liposome more passes through the tumor’s blood supply.10PubMed Central. Stealth Liposomes (PEGylated) Containing an Anticancer Drug Camptothecin: In Vitro Characterization and In Vivo Pharmacokinetic and Tissue Distribution Study
Active targeting goes a step further. By attaching molecules like antibodies or small peptides to the liposome surface, designers can aim the particle at specific receptors found on the target cell. The antibody locks onto its matching receptor the way a key fits a lock, increasing the odds the liposome binds to the right cell rather than a bystander.11PubMed. Surface Biomodification of Liposomes and Polymersomes for Efficient Targeted Drug Delivery Surface functionalization with these targeting molecules is a major area of research aimed at overcoming biological barriers in solid tumor therapy.12PubMed Central. Surface Functionalization and Targeting Strategies of Liposomes in Solid Tumor Therapy: A Review
Triggered Release
Getting a liposome to the right tissue is one thing; getting it to release its drug at the right moment is another. Conventional liposomes leak their contents gradually, which can be a problem if you want a concentrated burst of drug at the target site. Stimuli-responsive liposomes solve this by staying stable in normal circulation but releasing their payload when they encounter a specific trigger.13PubMed. Recent advances on thermosensitive and pH-sensitive liposomes employed in controlled release
Temperature-sensitive liposomes are the best-studied example. They are made from lipids that undergo a physical transition a few degrees above normal body temperature. When a clinician applies focused heat to a tumor using radiofrequency or ultrasound, the liposome membrane suddenly becomes far more permeable and dumps its drug locally.14PubMed Central. Thermosensitive liposomes for localized delivery and triggered release of chemotherapy pH-sensitive liposomes work on a similar principle but respond to the slightly acidic environment inside tumors or inside the cell’s endosomal compartments after uptake. In both cases, the idea is the same: keep the drug locked away until conditions at the target site flip the switch.
Liposomal Doxorubicin in Cancer Treatment
The most prominent clinical success story for liposomal delivery is the reformulation of doxorubicin, a potent chemotherapy drug notorious for damaging the heart. Conventional doxorubicin circulates freely through the bloodstream and accumulates in heart muscle, where it generates oxidative stress and can cause lasting damage that sometimes leads to heart failure years after treatment ends.
Wrapping doxorubicin in a liposome changes its distribution in the body. The drug concentrates more in the tumor (via the EPR effect) and less in the heart. A meta-analysis of randomized trials found that patients receiving liposomal doxorubicin had roughly a third the risk of heart failure compared to patients on conventional doxorubicin-based therapy, and drops in heart pumping capacity were about 60% less common.15PubMed Central. Efficacy and cardiovascular safety of liposomal doxorubicin: a systematic review and meta-analysis of randomized trials Tumor response rates and overall survival were essentially the same between the two formulations. In other words, the liposomal version was not more effective at killing cancer, but it was substantially safer for the heart.
Animal studies help explain the mechanism at the tissue level. In one pig study, liposomal doxorubicin produced less scarring (fibrosis) in both sides of the heart compared to conventional doxorubicin.16Cardiovascular Research. Liposomal doxorubicin attenuates cardiotoxicity via induction of interferon-related DNA damage resistance Separately, research in breast cancer models has shown that markers of oxidative stress in heart tissue are significantly lower when the liposomal form is used.17Scientific Reports. Reducing toxicity and enhancing efficacy of doxorubicin by liposomal doxorubicin and aprepitant in breast cancer The clinical takeaway is straightforward: the liposome acts as a shield, keeping the drug away from healthy tissue while still delivering it to the tumor.
Antifungal Therapy and Kidney Safety
Cancer is not the only field where liposomes have changed the safety equation. Amphotericin B, a powerful antifungal drug, is effective against life-threatening fungal infections but infamous for damaging the kidneys. The liposomal version (often known by the brand name AmBisome) wraps the drug in a lipid shell that alters how it distributes in the body, reducing the concentration that reaches kidney cells.
Even so, kidney injury still happens in some patients on liposomal amphotericin B. A study of patients who developed kidney injury during treatment found that most eventually recovered kidney function, and that the cumulative dose of the drug did not predict whether recovery would occur.18PubMed Central. Renal Recovery following Liposomal Amphotericin B-Induced Nephrotoxicity Clinical practice generally includes giving intravenous fluids and electrolyte supplements before and after each dose to protect the kidneys further.19Journal of Antimicrobial Chemotherapy. Liposomal amphotericin B and renal safety: review of the evidence and clinical considerations The liposomal formulation has not eliminated kidney risk, but it has made a drug that was once considered too toxic for many patients into a first-line treatment for severe fungal infections.
Infusion Reactions and PEG Sensitivity
Liposomal drugs are generally safer than their free-drug counterparts, but they are not side-effect free. One well-documented issue is a reaction called complement activation-related pseudoallergy, or CARPA. Unlike a true allergy, which involves the immune system’s IgE antibodies, CARPA is triggered when the liposome’s surface activates the complement system, a cascade of blood proteins that normally helps fight infections. The result can look a lot like an allergic reaction: flushing, chest tightness, low blood pressure, and in rare cases, anaphylaxis-like shock.20PubMed. Complement activation-related pseudoallergy caused by liposomes, micellar carriers of intravenous drugs, and radiocontrast agents
The PEG coating that makes stealth liposomes possible adds its own wrinkle. Some people develop antibodies against PEG (specifically, anti-PEG IgM). In pig models, a single injection of PEGylated liposomes triggered a massive rise in anti-PEG antibodies that peaked about a week later. When the animals were given a second dose of PEGylated liposomes during that window, they experienced severe reactions within minutes, including a rapid spike in pulmonary artery pressure that tracked closely with complement activation.21ACS Nano. Pseudo-anaphylaxis to Polyethylene Glycol (PEG)-Coated Liposomes: Roles of Anti-PEG IgM and Complement Activation in a Porcine Model of Human Infusion Reactions This is one reason clinicians often give the first dose of a liposomal drug slowly, watching for signs of a reaction before increasing the infusion rate.
Liposomal Supplements and Oral Delivery
Outside of hospitals, the place you are most likely to encounter liposomal delivery is the supplement aisle. Liposomal vitamin C is probably the most popular consumer product using this technology. The pitch is that wrapping vitamin C in liposomes protects it from being broken down in the gut and helps more of it reach the bloodstream.
A double-blind, placebo-controlled trial tested this claim head-to-head. Participants took either liposomal vitamin C, standard vitamin C, or a placebo. The peak concentration of vitamin C in the blood was about 27% higher with the liposomal version, and total absorption over 24 hours was about 21% higher. Liposomal vitamin C also produced about 20% higher peak concentrations inside white blood cells, which is relevant because immune cells use vitamin C actively.22PubMed Central. Liposomal delivery enhances absorption of vitamin C into plasma and leukocytes: a double-blind, placebo-controlled, randomized trial A separate crossover trial using a liposomal vitamin C powder found a roughly 30% increase in overall absorption compared to non-encapsulated vitamin C.23Applied Sciences. Bioavailability of Liposomal Vitamin C in Powder Form: A Randomized, Double-Blind, Cross-Over Trial
Those numbers are real but worth putting in context. A 20-30% improvement in absorption is meaningful in research terms, but it is not the dramatic transformation that some supplement marketing implies. Vitamin C is already reasonably well absorbed at normal doses. The biggest absorption losses happen at very high doses, where the gut’s transporters get saturated. That is where liposomal encapsulation has its largest potential advantage: it may bypass those saturated transporters by delivering vitamin C through the lipid membrane pathway instead. For someone taking a standard daily dose, the practical difference is smaller. The evidence so far is promising, but the trials are still small in scale, and researchers have noted the need for larger studies to confirm the findings.
Skincare and Cosmetic Uses
Liposomes made the jump to skincare decades ago, and today they appear in moisturizers, anti-aging serums, and sunscreen formulations. The appeal is the same as in drug delivery: the lipid membrane of a liposome is structurally similar to the lipid layers that make up the skin’s outer barrier (the stratum corneum), so liposomes can merge with those layers and carry active ingredients deeper than a standard cream would.
Recent work has started to map exactly which liposome properties matter most for skin penetration. Liposomes with high membrane fluidity, meaning their lipid bilayer is more flexible, dramatically increased delivery of their payload into the stratum corneum, producing more than six times the penetration of a standard sample within two hours. Positively charged liposomes behaved differently: they initially stuck to the skin surface for several hours before penetrating into deeper living skin layers, eventually reaching about 2.4 times the delivery of the standard by 24 hours. When high fluidity and positive charge were combined, the effect was greater than either alone.24PubMed. Drug delivery system (DDS)-inspired cosmetic liposomes: Unveiling physicochemical determinants of skin penetration under practical application conditions For cosmetic formulators, this means a liposome’s size, charge, and membrane stiffness can be tuned to control not just how deeply an ingredient penetrates but how fast it gets there.
How Liposomes Are Made at Scale
One of the lingering challenges in liposomal delivery is manufacturing consistency. Traditional methods, like dissolving lipids in an organic solvent, evaporating it to form a thin film, and then rehydrating the film with water, work well in a lab but produce liposomes of wildly varying sizes. Since size affects how long a liposome circulates, how easily it slips through leaky blood vessels, and how quickly it releases its contents, batch-to-batch variation is a real problem for pharmaceutical-grade products.
Microfluidic manufacturing has emerged as a solution. In these systems, a narrow stream of lipid dissolved in alcohol meets a surrounding stream of water inside a tiny channel. The lipids self-assemble into liposomes right at the interface. By adjusting how fast the two streams flow relative to each other, manufacturers can dial in the liposome size with remarkable precision, producing batches that range from about 50 to 150 nanometers in diameter with very uniform size distributions.25PubMed Central. Microfluidic Methods for Production of Liposomes High-throughput versions of this approach have been developed specifically for PEGylated liposomes, producing highly reproducible particles while keeping the size spread tight.26PubMed. High throughput microfluidics-based synthesis of PEGylated liposomes for precise size control and efficient drug encapsulation
Stability after manufacture is another hurdle. Liposomes can fuse together, leak their contents, or degrade during storage. Coating the liposome surface with polymers or other stabilizing materials helps, and the choice of coating depends on the application: a pharmaceutical product destined for intravenous injection has different stability requirements than a nutraceutical powder that sits on a shelf for months.27PubMed Central. Coating Materials to Increase the Stability of Liposomes
Liposomes, Lipid Nanoparticles, and Extracellular Vesicles
If you followed any of the science around COVID-19 mRNA vaccines, you heard a lot about lipid nanoparticles (LNPs). Liposomes and LNPs are close relatives. The term “liposome” was coined in the 1960s; “lipid nanoparticle” came into use in the early 1990s. Since liposomes are made of lipids and are usually nanosized, they are sometimes described as the earliest generation of lipid nanoparticles.3ACS Publications. Lipid Nanoparticles: From Liposomes to mRNA Vaccine Delivery, a Landscape of Research Diversity and Advancement The key structural difference is that a classic liposome has a well-defined hollow aqueous core surrounded by one or more bilayer shells, while modern LNPs used for mRNA delivery tend to have a more complex internal architecture with inverted lipid structures that help package and protect nucleic acids. But functionally, the concept is the same: wrap your cargo in biocompatible lipids to get it where it needs to go.
Extracellular vesicles (EVs) are a more recent entrant. These are natural nanoparticles that cells secrete to communicate with each other. They already carry proteins and genetic material between cells in the body, which makes them appealing as drug carriers. Compared to liposomes, EVs tend to have better biocompatibility and more natural targeting ability, because they come pre-loaded with surface proteins that guide them to specific cell types. On the other hand, liposomes are far easier to produce in large quantities, can carry more drug, and are simpler to standardize.28PubMed Central. Leveraging nature’s nanocarriers: Translating insights from extracellular vesicles to biomimetic synthetic vesicles for biomedical applications Some researchers are working on hybrid systems that combine a liposome’s manufacturability with an EV’s biological sophistication, using EV membrane proteins grafted onto a liposome scaffold.29PubMed Central. Liposomes and Extracellular Vesicles as Drug Delivery Systems: A Comparison of Composition, Pharmacokinetics, and Functionalization
A Brief History
The liposome story begins in 1961 at the University of Cambridge, where the British hematologist Alec Bangham and his colleague R. W. Horne were studying phospholipids and blood clotting under an electron microscope. The images they captured turned out to be the first visual evidence that phospholipids spontaneously form closed bilayer structures in water, a finding that also helped confirm the bilayer model of cell membranes. In the early 1970s, Gregory Gregoriadis proposed that these structures could be loaded with drugs and used as delivery vehicles.30Materials Today: Proceedings. A historical perspective of liposomes-a bio nanomaterial It took another two decades of work on stability, clearance, and manufacturing before the first liposomal drug reached the market in the 1990s. Since then, the technology has expanded from a niche pharmaceutical curiosity into a platform that underpins products ranging from cancer chemotherapy to the supplement bottle on your kitchen counter.