Liposome & Nanoliposome Encapsulation: Particle Size, Entrapment Efficiency & Stability

Overview #

Particle size is not a marketing number. It determines whether your active crosses the stratum corneum, sits on top of it, or degrades before it gets the chance. When brand partners come to us with a liposome brief, the first question we ask is: what are you actually trying to deliver, and where does it need to go? A 400 nm conventional liposome and an 80 nm nanoliposome are not interchangeable — they behave differently in the skin, in the bottle, and on the stability shelf. This is the article we wish every brand owner had read before their first formulation brief.

Liposome Types: What We Actually Work With #

Not all liposomes are the same, and the naming in supplier datasheets is inconsistent enough to cause real problems. Here is how we categorize them internally.

Conventional liposomes (MLV/SUV): Multilamellar vesicles typically run 200–1000 nm. They are the workhorse — relatively easy to manufacture, good entrapment efficiency for lipophilic actives (often 70–85%), and cost-effective at scale. The limitation is skin penetration. At 400 nm and above, most of the payload stays in the upper epidermis. That is fine for barrier actives like ceramides or cholesterol. It is not fine if you are trying to deliver retinol to the viable epidermis.

Small unilamellar vesicles (SUV) / nanoliposomes: We define nanoliposomes as sub-200 nm, typically 50–150 nm. These are harder to make consistently. High-pressure homogenization or microfluidics — both require tight process control. Entrapment efficiency for hydrophilic actives drops to 30–50% in our experience, which is the number most suppliers quietly omit from their pitch decks.

Transfersomes and elastic liposomes: Deformable vesicles with edge activators (typically sodium cholate at 0.5–1.5% w/w or Tween 80). They squeeze through tight junctions. We have seen transdermal flux data that is genuinely impressive — but the formulation window is narrow and they are sensitive to drying. Do not put them in a jar.

Archaeosomes and stealth liposomes (PEGylated): Mostly pharmaceutical territory. We get briefs for these occasionally from brands crossing into cosmeceutical positioning. Honest answer: the regulatory pathway in cosmetics is unclear, and we push back on these unless the brand has a very specific clinical claim strategy.

The table below is the reference we use internally when scoping a new encapsulation brief.

Cost index is relative to a standard MLV batch at 200 kg scale. These are not supplier quotes — they reflect our actual COGS across projects over the past three years.

For deeper context on how encapsulation interacts with active ingredient selection, see our Encapsulation Technology formulation library.

Particle Size: The Number That Actually Matters #

We measure particle size by dynamic light scattering (DLS) on every batch. The target range depends on the application, but the number we watch most closely is the PDI — polydispersity index. A mean particle size of 120 nm with a PDI of 0.35 is not the same product as 120 nm at PDI 0.12. The first one has a wide size distribution that will behave unpredictably in stability. The second is what we aim for.

Below 200 nm, nanoliposomes show measurably better penetration into the stratum corneum lipid matrix. The mechanism is reasonably well understood — smaller vesicles interact more efficiently with the intercellular lipid lamellae. Above 400 nm, you are largely relying on follicular penetration pathways, which are real but limited in surface area.

One clinical study worth citing directly: a randomized, double-blind, vehicle-controlled trial (n=42, 12 weeks) comparing nanoliposomal vitamin C (80 nm, 10% ascorbic acid) against free ascorbic acid at the same concentration found a 34% greater improvement in skin luminance score (colorimetry, L* value) in the nanoliposome arm. Tolerability was also better — 6 subjects in the free acid arm reported transient stinging versus 1 in the nanoliposome arm. The study design was solid. What it does not tell you is whether the improvement was from better penetration, better stability in the formula, or both. We suspect both.

The regulatory position on nanoparticles in cosmetics is worth knowing before you finalize a brief. The EU Cosmetics Regulation 1223/2009 requires mandatory notification for nanomaterials, with a specific definition: insoluble or biopersistent particles with at least 50% of the size distribution at 1–100 nm. Liposomes are generally considered soluble/biodegradable and have historically been excluded from this definition — but the SCCS has been tightening its guidance. Check the latest SCCS Scientific Opinion before you finalize your EU launch strategy. This is still evolving, and what is acceptable today may shift.

Entrapment Efficiency: Where the Supplier Data Gets Optimistic #

Entrapment efficiency (EE%) is the percentage of active ingredient successfully encapsulated versus total active added. Suppliers report it. We verify it. The numbers do not always agree.

The standard method is ultracentrifugation followed by HPLC quantification of the supernatant. Some suppliers use dialysis, which gives systematically higher EE% values because the separation is less complete. When we onboard a new liposome supplier, we run both methods and compare. We have seen discrepancies of 15–20 percentage points. That matters when you are dosing a retinol formula at 0.3% and expecting 0.25% to be encapsulated.

For hydrophilic actives like niacinamide or vitamin C, EE% in SUVs typically runs 30–50% in our lab. Lipophilic actives like retinol, CoQ10, and bakuchiol encapsulate more efficiently — 65–80% in MLVs, somewhat lower in SUVs due to the reduced membrane volume. Amphiphilic actives are the most variable. We have had batches of encapsulated resveratrol swing between 45% and 72% EE depending on the phospholipid-to-active ratio and the hydration temperature.

Honestly, most brands underestimate how much EE% variation affects their label claim strategy. If you are claiming “encapsulated retinol 0.5%,” you need to know whether that is 0.5% total retinol or 0.5% encapsulated retinol. The difference is significant, and regulators in some markets are starting to ask.

Stability: Where Most Projects Actually Fail #

This is usually where projects go sideways. A liposome formula that looks perfect at lab scale — clear, elegant, stable at 40°C/75% RH for 4 weeks — can behave very differently at production scale.

We had one project: a nanoliposomal peptide serum, 150 nm target particle size, looked excellent through 8 weeks of accelerated stability at 500 g lab scale. At 180 kg production scale, we saw particle size drift from 148 nm to 310 nm by week 6 of real-time stability at 25°C. The emulsification shear profile was different at scale — the high-pressure homogenizer we use at production runs a different pressure cycle than the lab unit. We had to reformulate the phospholipid ratio and add 0.3% cholesterol as a membrane stabilizer. It added six weeks to the timeline. We now require a 20 kg pilot batch as a mandatory step before full production on any nanoliposome project.

The main physical degradation pathways we monitor are: vesicle aggregation (tracked by DLS), membrane oxidation (tracked by peroxide value on the phospholipid fraction), and active leakage (tracked by EE% at T0, 4 weeks, 8 weeks, 12 weeks under ICH conditions). For oxidation-sensitive actives like retinol or CoQ10, we run stability under nitrogen headspace. The ICH Stability Guidelines define the standard conditions — 40°C/75% RH for accelerated, 25°C/60% RH for long-term — and we follow them, but we also add a 50°C/ambient RH stress condition for liposome projects specifically because it catches membrane fusion events that the standard conditions miss.

Preservative efficacy is the other stability dimension that catches brands off guard. Liposome membranes can sequester preservatives — particularly parabens and phenoxyethanol — reducing the free preservative concentration in the aqueous phase. We have seen phenoxyethanol EE into liposome membranes of 20–35% depending on membrane composition. That means a formula passing challenge test at 0.8% phenoxyethanol in a simple aqueous system may fail when the same concentration is used in a liposome formula. We typically run a full ISO Standards ISO 11930 preservative efficacy test on the final liposome formula, not just the base.

Phospholipid Selection and Membrane Engineering #

The phospholipid is the structural material of the vesicle. The choice matters more than most briefs acknowledge.

Soy-derived phosphatidylcholine (PC) is the standard — cost-effective, well-characterized, and available at cosmetic grade. Hydrogenated PC (HSPC) gives a higher phase transition temperature (Tm ~55°C versus ~-15°C for unsaturated PC), which means better membrane rigidity at room temperature and better stability in warm climates. We use HSPC for products targeting Southeast Asian markets where supply chain temperatures are unpredictable.

Cholesterol is almost always added at 20–40 mol% to modulate membrane fluidity and reduce permeability. Below 20 mol%, membranes are too fluid and leakage increases. Above 40 mol%, you start to see cholesterol crystallization in some formulas. The sweet spot in our lab is 30–35 mol% for most applications.

Lyso-PC and lysophosphatidylserine are used in smaller amounts as edge activators for elastic liposomes. The formulation window is genuinely narrow. We almost always push back on elastic liposome briefs from brands who want to use them in a standard emulsion base — the deformability is compromised by the continuous phase viscosity.

For retinoid-containing liposomes specifically, see our Retinoid Technology formulation notes — the pH and antioxidant requirements interact with membrane composition in ways that are not obvious from the phospholipid datasheet alone.

Manufacturing Scale-Up: What the Lab Doesn’t Tell You #

Three methods dominate at our scale: thin-film hydration followed by extrusion, high-pressure homogenization (HPH), and microfluidics.

Thin-film hydration with extrusion is the most controllable for small batches. At 200 kg scale, it becomes impractical — the extrusion step is a bottleneck and membrane fouling is a real issue above 50 kg. We use it for pilot batches and for very high-value actives where yield loss matters.

HPH is our production workhorse. We run a two-stage homogenizer at 800–1200 bar for nanoliposome production. The number of passes matters — typically 5–8 passes to reach target particle size, with DLS measurement between passes. Temperature control during HPH is critical for oxidation-sensitive actives. We chill the feed to 4–8°C before processing.

Microfluidics gives the tightest PDI values we have seen — consistently below 0.15 — but throughput is limited. At our current microfluidics capacity, maximum batch size is around 15 kg. For indie brands at MOQ 500–1000 units, that is workable. For a 50,000-unit launch, it is not.

Cost reality: nanoliposome manufacturing adds $0.60–$1.80 per unit to COGS depending on the active, the target particle size, and the batch size. At MOQ 1000 units, that is meaningful. At MOQ 10,000 units, it is usually justifiable if the encapsulation is doing real work. Encapsulation for marketing purposes alone — where the active would be stable and effective without it — is a cost we try to talk brands out of.

Formulation Notes for Brand Partners #

What market? What are you expecting on-pack? Those are the first two questions. A “nanoliposome serum” for the EU market has a different regulatory and stability brief than the same product for the US or China NMPA pathway. Under NMPA Cosmetic Regulation, new raw materials with novel delivery mechanisms may require additional safety dossiers — we have navigated this and it adds 3–6 months to the timeline if not planned for.

If you are coming to us with a liposome brief, here is what we need to scope the project properly: the target active (identity, concentration, and whether you have a preferred supplier), the intended market and any existing regulatory commitments, the product format (serum, cream, essence — this affects the continuous phase and therefore the liposome stability), and your stability expectation (24-month shelf life at 25°C is standard; some markets require 30 months).

We will tell you honestly if encapsulation adds value for your specific active and concentration. For some actives — stable, well-penetrating molecules like niacinamide at 5% — it does not. For others — retinol above 0.1%, unstable vitamin C derivatives, sensitive peptides — it genuinely does. The FDA Cosmetics Guidelines do not regulate encapsulation technology specifically, but they do govern label claims, and we will flag anything that creates a drug claim risk before it becomes your problem.

Budget for a 20 kg pilot batch. It is not optional on nanoliposome projects. We learned that the hard way.

Frequently Asked Questions #

Q: We want to say “nanoliposome technology” on pack for the EU — do we need to notify it as a nanomaterial?

Liposomes are generally classified as biodegradable and soluble, which historically exempts them from the EU nanomaterial notification requirement under Regulation 1223/2009. But if your vesicles are sub-100 nm and you are making a penetration claim, the SCCS may take a different view. We recommend confirming with your EU responsible person before finalizing the claim — the guidance has shifted twice in the last four years.

Q: What concentration of retinol can you actually stabilize inside a liposome?

In our standard nanoliposome system (HSPC/cholesterol, 30 mol% cholesterol, nitrogen headspace), we routinely stabilize retinol at 0.3–0.5% with less than 10% degradation at 12 months real-time. Above 0.5%, membrane saturation becomes an issue and EE% drops sharply. If a brand wants to label “retinol 1% encapsulated,” we will have a frank conversation about what that actually means for stability.

Q: How much does liposome encapsulation add to the unit cost?

Roughly $0.60–$1.80 per unit at MOQ 1000, depending on the active and target particle size. Microfluidics-produced nanoliposomes at the high end, standard MLV at the low end. At MOQ 10,000 the range compresses to $0.40–$1.20. These are COGS additions — packaging and margin are separate.

Q: Can we combine two actives in the same liposome?

Sometimes. Co-encapsulation works well when both actives have similar polarity and compatible stability profiles — retinol and tocopherol, for example, co-encapsulate cleanly in our lipophilic membrane system. Combining a hydrophilic and a lipophilic active in the same vesicle is technically possible but EE% for the hydrophilic component typically drops to 25–35%, which may not justify the complexity. We have run 14 co-encapsulation projects in the past two years — about half delivered the expected EE% for both actives.

Q: What stability testing do you run on liposome batches before release?

Minimum release criteria on every batch: particle size by DLS (mean and PDI), EE% by HPLC, pH, viscosity, and visual appearance. For the stability program, we follow ICH Q1A conditions — 40°C/75% RH accelerated (6 months) and 25°C/60% RH long-term (up to 24 months). We add a 50°C stress condition and a freeze-thaw cycle (3× cycles, -20°C to 25°C) for all nanoliposome projects. Preservative efficacy per ISO 11930 is run at T0 and at 12 months.

Have a product concept in mind? Contact our formulation team to request a complimentary brief review.