Logic for Selecting Phospholipids in Liposome Formulations: Membrane State, Stability, Membrane-Surface Function, and Source Control

Overview

When selecting phospholipids for a liposome formulation, the choice should first be matched to the experimental task. The variables that most directly affect experimental performance are usually the chain-melting transition temperature (Tm), fatty acyl chain length and degree of unsaturation, the membrane-surface properties imparted by the headgroup, the cholesterol proportion, and lipid source and impurity control. Together, these factors determine the membrane phase state at the working temperature, leakage level, chemical stability, surface interactions, and the feasibility of downstream development. Marsh’s review points out that fatty acyl chain length, the number and position of double bonds, chain asymmetry, and headgroup length all affect the chain-melting transition temperature; when high-Tm lipids are combined with cholesterol, they often alter bilayer order and phase behavior, and can weaken or broaden what would otherwise be a more cooperative phase transition; with suitable compositions, they may also give rise to liquid-ordered characteristics. The FDA guidance on liposome drug products, meanwhile, includes peroxides, free fatty acids, lysophospholipids, degree of unsaturation, and source-related information within the scope of quality control and development assessment.

In liposome formulation work, phospholipid selection can usually begin with four questions: should the membrane be relatively rigid or relatively soft at the working temperature; is the system more susceptible to oxidation or to hydrolysis; does the membrane surface need to mediate specific interactions; and is the formulation being used only for current experimental validation, or does it already need to accommodate quality control and downstream development requirements. Following this sequence makes it easier to translate formulation choices into experimental objectives, stability control, and development needs.

Four Key Questions to Assess Before Selecting a Liposome Formulation

Question to assess	Key variables	Main impact
Should the membrane be relatively rigid or relatively soft at the working temperature?	Tm, chain length, degree of unsaturation, cholesterol	Membrane fluidity, leakage, extrusion difficulty, storage state
Is the system more susceptible to oxidation or hydrolysis?	Degree of unsaturation, oxygen, light, heat, pH, buffer system	Stability, impurity formation, long-term reproducibility
Does the membrane surface need to mediate specific interactions?	Headgroup type, surface charge, local chemical environment	Protein binding, cell recognition, interpretation of model membranes
Does the formulation already need to accommodate development and quality control requirements?	Source, degree of compositional definition, impurity profile, supply chain	Batch-to-batch consistency, quality control, development feasibility

1. At the Working Temperature, Should the Membrane Be More Condensed or More Fluid?

In phospholipid selection, the first question is what state the membrane is expected to adopt at the working temperature. For liposomes, the relationship between working temperature and lipid phase state directly affects leakage, structural integrity, fusion behavior, release mode, and particle-size control during preparation. Increasing chain length, lowering unsaturation, and making fatty acyl chain packing more regular will usually raise the main chain-melting transition temperature; for multicomponent systems, however, greater attention should be paid to the main phase transition range and overall phase state of the mixed membrane, rather than to the Tm of any single lipid alone.

1.1 Whether the membrane state at the working temperature matches the experimental objective

When the working temperature is below the main phase transition range of the principal lipid or mixed system, the membrane is usually more condensed, which is generally more favorable for reducing leakage and maintaining structural integrity; when the working temperature is above that range, the membrane is usually more fluid, which is more favorable for fusion, rearrangement, and partial release behavior.

1.2 Whether the current experiment needs stability more, or fluidity and responsiveness more

Systems that require long-term storage, low-leakage encapsulation, and high structural integrity are usually better served by prioritizing higher-Tm lipids, followed by cholesterol to tune membrane order and permeability. By contrast, systems that require strong fluidity, membrane fusion, or heat-triggered release should avoid placing the entire formulation in an overly condensed regime, because that will weaken membrane rearrangement and release responsiveness.

1.3 Whether the preparation conditions match the membrane state

For formulations with a high proportion of high-Tm lipids, hydration, freeze-thaw treatment, and extrusion should also usually be carried out at temperatures above the main phase transition range, so as to reduce state drift during preparation, broadening of the particle-size distribution, and batch-to-batch variation. In FDA requirements for liposome drug products, particle-size distribution, liposome integrity, and lipid component stability are also explicitly identified as key quality attributes that require attention.

1.4 What role cholesterol mainly plays in this part

Here, cholesterol is used mainly to regulate bilayer order, membrane permeability, and phase behavior. When the goal is to reduce leakage, it is often used to increase membrane compactness; when some degree of fluidity or release capability needs to be retained, its level should be controlled to avoid pushing the system into an excessively condensed state. The cholesterol ratio should therefore be considered together with the Tm of the principal lipid, fatty acyl chain composition, and the target membrane state.

1.5 Formulation decisions under different membrane-state objectives

Current experimental objective	What to examine first	Formulation direction
Reduce leakage and improve storage stability	Whether the main phase transition range of the principal lipid or mixed system is above the working temperature	Prioritize higher-Tm lipids, then fine-tune with cholesterol
Maintain good fluidity or fusogenicity	Whether the membrane is overly condensed at the working temperature	Avoid using only high-Tm components throughout the formulation
Achieve heat-triggered or mild release	Whether the formulation’s phase transition range falls near the target temperature window	Use lipid ratios to define the release window
Achieve stable processing and uniform particle size	Whether the process temperature is above the main phase transition range	Adjust process temperature in step with the phase state of the principal lipid

2. Is the Main Chemical Stability Risk in the System Oxidation or Hydrolysis?

In liposome formulations, chemical stability should generally be separated first into two major risks: fatty acyl chain oxidation and ester-bond hydrolysis. Both can alter membrane composition and experimental outcomes, but their triggers, principal impurities, and priority control points are different, so they should be evaluated separately. Reviews of oxidative stability indicate that degree of unsaturation, oxygen exposure, light, temperature, trace metals, and the interfacial environment all influence lipid oxidation; the FDA guidance on liposome products explicitly states that lipid components require attention to parameters such as peroxides, free fatty acids, lysophospholipids, and degree of unsaturation.

2.1 For systems containing a relatively high proportion of unsaturated fatty acyl chains, assess oxidation risk first

For formulations containing a relatively high proportion of unsaturated fatty acyl chains, oxidation is usually the first issue that needs to be assessed. Oxidation can cause compositional drift, reduced long-term stability, and poorer batch reproducibility. If cholesterol is also present in the system, cholesterol oxidation products should likewise be included in the assessment. A 2024 review on excipient-related impurities in liposome drug products identified lysophospholipid-related impurities and cholesterol oxidation products as two major classes of excipient-related impurities of concern; therefore, in cholesterol-containing formulations, stability assessment cannot focus only on the fatty acyl chains themselves.

2.2 For systems kept in the aqueous phase for long periods or under unusual pH conditions, assess hydrolysis risk first

Hydrolysis risk is better assessed in relation to aqueous exposure time, pH, buffer system, and storage conditions. The FDA clearly notes that both saturated and unsaturated lipids may hydrolyze to generate lysophospholipids and free fatty acids. In systems involving long incubation, long-term aqueous storage, repeated freeze-thaw cycling, or pH values deviating from neutrality, rises in free fatty acids and lysophospholipids are particularly worth monitoring first. In such formulations, buffer type, concentration, and system pH should not be treated merely as background conditions, but should instead be evaluated independently as stability variables.

2.3 Stability optimization should be handled separately according to the dominant risk

When oxidation is the dominant risk, optimization usually focuses on reducing exposure to oxygen, light, heat, and trace metals, while controlling the accumulation of unsaturated-lipid-related and cholesterol-related impurities. When hydrolysis deserves higher priority, optimization should instead shift toward pH, buffer system, aqueous exposure time, and storage conditions, so as to reduce compositional changes and drift in membrane properties.

2.4 Key points for evaluating the two types of stability risk

Risk type	Common triggering factors	Main impact	Indicators worth prioritizing
Oxidation	Unsaturated fatty acyl chains, oxygen, light, heat, trace metals	Compositional drift, decreased long-term stability, accumulation of oxidative impurities	Peroxides, cholesterol oxidation-related risk, storage conditions
Hydrolysis	pH deviation, elevated temperature, buffer effects, prolonged aqueous exposure	Increase in free fatty acids and lysophospholipids, changes in membrane properties	Free fatty acids, lysophospholipids, suitability of the buffer system

3. The Focus of Headgroup Selection: Surface Charge, Specific Recognition, or Structural Regulation

Headgroup selection should not be reduced to a simple classification of “neutral” versus “charged.” In liposomes, headgroups affect surface charge, interactions with proteins or cells, and the structural behavior of the membrane itself. In formulation design, these choices can usually be divided into four categories: tuning surface charge, introducing specific biological recognition, altering membrane structural behavior, or constructing a relatively inert carrier membrane.

3.1 When tuning dispersibility, interparticle interactions, and surface potential, examine headgroup charge first

If the main goal is to control dispersibility, interparticle interactions, adsorption behavior, or surface potential, priority should be given to headgroup charge and to the ratio between neutral and charged lipids. At this level, the main effects are on particle stability, surface adsorption, and the initial interactions with the surrounding medium.

3.2 When coagulation, phagocytosis, or cell recognition is involved, PS is a key variable

For systems involving coagulation, phagocytosis, immune regulation, or cell recognition, phosphatidylserine (PS) should be treated separately. PS is associated with interactions involving coagulation factors, phagocytic recognition, and immune processes. Accordingly, after PS is introduced, what changes is not only surface charge, but also the biological meaning of the membrane surface and the interpretation of the experiment.

3.3 In pH-sensitive or fusogenic systems, focus on PE/DOPE

In pH-sensitive, fusogenic, or easily rearranged membrane systems, the key issue is not surface charge, but membrane structural behavior. DOPE has a pronounced non-bilayer tendency and is often used as a fusogenic helper lipid; it usually needs to be combined with components that stabilize the bilayer under neutral conditions. Many pH-sensitive liposomes make use of exactly this “stable at neutral pH, destabilized under acidic conditions” design logic to achieve membrane rearrangement and payload release.

3.4 For relatively inert carrier membranes, minimize extra functional signals

If the goal is simply to construct a relatively inert carrier membrane, attention should be focused on surface inertness, dispersibility, and membrane stability, while minimizing headgroups that would significantly alter recognition behavior or membrane structural behavior.

3.5 Key considerations in headgroup selection for different tasks

Current task	Headgroup or variable to prioritize	Key consideration
Tune dispersibility, interparticle interactions, and surface potential	Headgroup charge; ratio of neutral to charged lipids	First control surface charge and dispersion behavior
Introduce specific biological recognition	Headgroups with clear biological significance, such as PS	Such headgroups directly change how the membrane surface should be interpreted
Build pH-sensitive, fusogenic, or readily rearranged membranes	Headgroups such as PE/DOPE that affect curvature and phase behavior	Focus on bilayer stability, curvature preference, and release behavior
Build a relatively inert carrier membrane	Whether additional functional headgroups can be avoided	Prioritize surface inertness and membrane stability

4. The Key Point in Lipid Source Selection: Clarity of Composition and Quality Control Requirements

Different lipid sources come with different documentation requirements and different quality control priorities. For synthetic or semisynthetic lipids, the FDA focuses on structural confirmation, fatty acid composition, acyl positional specificity, synthetic and purification processes, and related impurities. For naturally derived lipids, the focus is on composition ranges, fatty acid distribution, biological source, supplier, extraction and purification processes, as well as risk control for animal proteins, viruses, pyrogens, and bacterial endotoxins.

4.1 At the experimental validation stage, first ask whether the material is easy to obtain and can be reproduced reliably

If the current task is mainly experimental screening or method validation, source selection should first consider whether the material is readily obtainable, whether the batches are stable, and whether the material is sufficient to support the research question at hand. At this stage, the emphasis is usually not on defining lipid composition in extreme detail, but on ensuring that the formulation can be prepared reproducibly and that the experimental results are repeatable.

4.2 At the development stage, compositional clarity and quality control matter more

Once a formulation enters the development stage, the focus shifts to whether the lipid composition is clearly defined, whether impurities are clearly characterized, whether batch-to-batch consistency is stable, whether the supply chain is reliable, and whether current analytical methods and quality standards can support subsequent development. Naturally derived phospholipids often have more practical advantages in terms of scale-up, cost, and regulatory acceptance; high-purity synthetic phospholipids with more clearly defined compositions, by contrast, are better suited to systems in which quality attributes need to be clearly defined and composition-performance relationships need to be established.

4.3 Key considerations for different lipid sources

Evaluation dimension	Naturally derived lipids	Synthetic/semisynthetic lipids
How composition is expressed	Composition range, fatty acid distribution	Single-molecule structure, positional specificity, purity
Main control priorities	Biological source, extraction and purification, animal-derived risk control	Synthetic impurities, residual solvents, process-related by-products
What matters more during development	Scale-up, cost, batch-to-batch consistency	Degree of definition, structural designability, analytical identifiability
More suitable application scenarios	Early-stage screening, large-scale supply, established pharmaceutical use	Fine design, clear structure-property relationships, deeper development

5. Product Guide to Phospholipid Selection in Liposome Formulations (Choose Table 1–Table 3 by Research or Experimental Objective)

Research or experimental objective	Recommended table to consult first	Why this table should be consulted first	Recommended related table(s)	Guidance note
To first build a basic understanding of phospholipid systems and determine the respective roles of natural-source PC, synthetic PC, cholesterol, and sphingomyelin as fundamental membrane components	Table 1	Table 1 brings together the most common and most fundamental membrane components, including the core PC framework, cholesterol, and sphingomyelin, making it the best place to first understand the basic construction logic of phospholipid bilayers	Then see Table 3	Once the basic logic of “how the membrane is built” is clear, it becomes easier to judge later formulation-adjustment directions when moving on to functional lipids and surface-modifying lipids
To screen formulations around membrane rigidity, fluidity, phase transition temperature, and leakage control in liposomes	Table 1	Table 1 includes natural-source PC, saturated/unsaturated PC, mixed-chain PC, and cholesterol, making it the most suitable table for comparing how different fatty acyl chain structures and sterol-mediated membrane regulation affect bilayer properties	Then see Table 2	This type of study usually starts by establishing the basic membrane properties with neutral structural lipids, and then, as needed, adds anionic lipids to observe how membrane-surface charge and membrane properties change together
To design core formulations for conventional liposomes, long-circulating liposomes, or highly stable liposomes	Table 1	Table 1 covers typical structural components such as HSPC, DPPC, DSPC, POPC, and cholesterol, making it the most suitable starting point for building the main formulation framework of either stable or fluid liposomes	Then see Table 3	After the main structural framework has been defined, components such as DSPE and PEG-PE in Table 3 can be used to further implement surface modification and long-circulation design
To study anionic membrane surfaces, membrane-surface charge effects, or the influence of negatively charged lipids on vesicle behavior	Table 2	Table 2 focuses on anionic phospholipids such as PS, PG, PA, PI, and cardiolipin, making it suitable for comparing how different negatively charged headgroups affect membrane-surface properties and overall system behavior	Then see Table 1	Anionic lipids are usually not used alone to form membranes, but rather in combination with basic structural lipids such as PC or cholesterol, so Table 1 should be consulted together
To construct membrane-surface models related to PS externalization, apoptotic recognition, phagocytic recognition, or coagulation	Table 2	DOPS and POPS in Table 2 are the most directly relevant PS-type membrane lipids, making them suitable for building PS exposure models and studying PS-dependent protein or cell recognition processes	Then see Table 1	Such systems often require introducing a certain proportion of PS into a neutral PC-based membrane framework, so Table 1 is still needed to define the main membrane composition
To study mitochondrial membrane models, respiratory-chain-related membrane proteins, or cardiolipin-related experiments	Table 2	Table 2 includes cardiolipin, PI, PA, and other lipids more closely associated with functional membrane research, making it suitable for studies of mitochondrial membranes, inner membranes, and specific membrane-protein interactions	Then see Table 1	Functional membrane studies still usually require PC, cholesterol, or sphingomyelin to build a more complete biomimetic membrane system
To build cationic liposomes, nucleic acid delivery systems, transfection systems, or intracellular delivery systems	Table 3	DOTAP, DOPE, DSPE, and PEG-PE in Table 3 are among the most common functional and helper lipids used in delivery systems, making this the most suitable table for directly building transfection or delivery formulations	Then see Table 1	Many delivery systems do not contain functional lipids alone, but also introduce PC or cholesterol to optimize membrane stability, so Table 1 should also be consulted during selection
To study membrane fusion, endosomal escape, responsive release, or surface modification	Table 3	Table 3 focuses on components such as DOPE, DSPE, and PEGylated PE that are directly related to membrane fusion, surface anchoring, and stealth behavior, making it the most suitable table for such function-oriented studies	Then see Table 1 and Table 2	Such studies usually overlay functional lipids onto a basic structural membrane framework, and may also incorporate anionic lipids to adjust the membrane-surface environment, so all three tables often need to be consulted together
To build biomimetic membranes or model membrane systems closer to natural cellular membrane composition	Table 1 + Table 2	Table 1 provides common neutral and ordered membrane components such as PC, cholesterol, and sphingomyelin, while Table 2 provides functional anionic lipids such as PS, PI, PG, PA, and cardiolipin; taken together, they more closely reflect the compositional logic of real biological membranes	Then see Table 3	If surface PEGylation, ligand modification, or special delivery functions are also needed, Table 3 can then be consulted additionally
If the research objective is still unclear and the goal is simply to start building a selection framework from common, basic, and representative phospholipids	Table 1	Table 1 is the most suitable entry point, because it first establishes the most basic issues, including natural versus synthetic sources, saturated versus unsaturated lipids, and cholesterol-mediated membrane regulation	Then see Table 2 and Table 3	Once the basic structural lipids are understood, it becomes easier to move on to anionic functional lipids and delivery/surface-modifying lipids in a more structured way

Table 1 | Phosphatidylcholine Structural Lipids and Sterol-Type Membrane-Regulating Components

Classification	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Natural-source phosphatidylcholine mixture	97281-47-5	L130333	L-α-phosphatidylcholine (Soy)	Natural, ≥99%	A commonly used natural neutral phospholipid matrix, suitable for preparing conventional liposomes, emulsions, and biomimetic membrane systems.
Natural-source phosphatidylcholine mixture	97281-44-2	L130151	L-α-phosphatidylcholine (95%) (Egg, Chicken)	Natural, ≥95%	A classic natural PC mixture widely used in liposome preparation, membrane-property comparison, and cell-membrane biomimetic studies.
Hydrogenated natural highly saturated phosphatidylcholine	97281-48-6	P1456034	Phosphatidylcholine, hydrogenated from Non-GMO Soybean (HSPC)	Natural, ≥90%	High in saturation, with good membrane compactness and storage stability; commonly used as a structural lipid for stable or long-circulating liposomes.
Sterol-type membrane-compacting regulator	57-88-5	C432975	Cholesterol from wool fat	PharmPure™, JP, BP, Ph. Eur., NF, ultrapure grade	Regulates membrane fluidity, elasticity, and permeability; commonly co-formulated with PC, SM, and related lipids to reduce leakage and improve bilayer integrity.
Unsaturated high-fluidity PC structural lipid	4235-95-4	D130438	1,2-dioleoyl-sn-glycero-3-phosphocholine	Moligand™, ≥99%	Has a low phase transition and high membrane fluidity; commonly used in GUVs, supported membranes, fluid liposomes, and membrane-protein reconstitution models.
Lysophosphatidylcholine (Lyso-PC)	19420-57-6	S465645	1-Stearoyl-sn-glycero-3-phosphocholine	Moligand™, ≥99%, powder	A monoacyl PC commonly used to study the effects of lysophospholipids on membrane curvature, membrane stability, and liposome release behavior.
High-Tm saturated PC structural lipid	63-89-8	D130424	1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)	Moligand™, ≥99%	A classic saturated PC widely used in phase-transition studies, pulmonary surfactant-related models, and basic formulations for thermosensitive liposomes.
High-Tm saturated PC structural lipid	816-94-4	D130429	1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)	Moligand™, ≥99%	Offers high bilayer rigidity and low permeability; commonly used as a structural lipid in highly stable liposomes and long-circulating formulations.
Mixed-chain PC structural lipid	26853-31-6	P130452	1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)	≥99%	A commonly used standard neutral model membrane lipid combining good membrane-forming ability and fluidity; suitable for LUV, GUV, and supported membrane studies.
Sphingomyelin / ordered-membrane lipid	108392-10-5	N130674	N-oleoyl-D-erythro-sphingosylphosphorylcholine	≥99%	Commonly used in ordered membrane domains, raft-like systems, and membrane models related to neural membranes and erythrocyte membranes.
Medium-Tm saturated PC structural lipid	18194-24-6	D130420	1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)	≥99%	Has a moderate phase transition temperature, making it suitable for temperature-controlled bilayer property studies and liposome preparation under relatively mild conditions.
Mixed-chain asymmetric PC structural lipid	76343-22-1	M665061	1-myristoyl-2-stearoyl-sn-glycero-3-phosphocholine	≥98%	An asymmetric saturated-chain PC commonly used to study the effects of chain-length asymmetry on membrane packing, phase separation, and bilayer thickness.
Cholesterol-derived membrane-stabilizing component	1510-21-0	C132483	Cholesteryl hemisuccinate	≥97%	A carboxyl-bearing cholesterol derivative commonly used in membrane stabilization, pH-responsive liposomes, and membrane-protein solubilization/reconstitution systems.

Table 2 | Anionic Phospholipids for Membrane-Surface Function

Classification	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Anionic phosphatidylserine (PS)	90693-88-2	D130321	1,2-dioleoyl-sn-glycero-3-phospho-L-serine (sodium salt) (DOPS)	Moligand™, ≥99%	Commonly used for modeling externalized PS, apoptotic recognition, protein–membrane interactions, and highly fluid anionic liposomes.
Cardiolipin / mitochondrial membrane signature lipid	115404-77-8	B130226	1',3'-bis[1,2-dioleoyl-sn-glycero-3-phospho]-sn-glycerol (sodium salt)	≥99%	A representative lipid of the inner mitochondrial membrane, commonly used in studies of respiratory-chain complexes, membrane-protein reconstitution, and mitochondria-related membrane models.
Saturated anionic phosphatidylglycerol (PG)	200880-41-7	D130350	1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt)	≥99%	Has a well-defined negative charge and a relatively high phase transition temperature; commonly used in anionic liposomes, pulmonary surfactant-related systems, and charge-effect studies.
Unsaturated anionic phosphatidylglycerol (PG)	67254-28-8	D130353	1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt	≥99%	Highly fluid; commonly used in anionic model membranes, antimicrobial peptide/membrane-protein interaction studies, and negatively charged liposomes.
Anionic phosphatidic acid (PA)	108392-02-5	D130369	1,2-dioleoyl-sn-glycero-3-phosphate (sodium salt) (18:1 PA)	≥99%	A bioactive membrane lipid commonly used in studies of membrane curvature, membrane fusion, vesicular trafficking, and PA-binding proteins.
Mixed-chain anionic phosphatidylglycerol (PG)	268550-95-4	P130351	1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (POPG sodium salt)	≥99%	Combines negative charge with moderate fluidity; commonly used in model membranes, lipid nanoparticles, and pulmonary surfactant-related studies.
Natural-source anionic phosphatidylinositol (PI)	383907-36-6	L130328	L-α-phosphatidylinositol (Soy) (sodium salt)	≥99%	Commonly used to model eukaryotic inner-membrane composition and to study PI-related membrane-protein interactions and signaling-lipid precursor systems.
High-Tm anionic phosphatidylglycerol (PG)	200880-42-8	D130352	1,2-distearoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt)	≥97%	Forms a relatively compact bilayer and is commonly used in highly stable anionic liposomes and charge-regulation systems.
Mixed-chain anionic phosphatidylserine (PS)	321863-21-2	P130320	16:0-18:1 PS (POPS)	≥97%	Commonly used in PS models closer to natural membrane-lipid composition, and in studies of apoptotic recognition, coagulation-related membrane surfaces, and PS-binding proteins.

Table 3 | Lipids for Special Functions and Surface Modification

Classification	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Cationic transfection lipid	132172-61-3	D351073	1,2-Dioleoyl-3-trimethylammonium-propane, Chloride (DOTAP Chloride)	Moligand™, ≥99%	A classic cationic lipid commonly used in positively charged liposomes, DNA/RNA complexation, transfection, and delivery systems.
Helper phosphatidylethanolamine (PE)	4004-05-1	D155634	1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE)	≥98%	Has a tendency to form non-bilayer phases and is commonly used as a helper lipid to promote membrane fusion, post-endocytic escape, and delivery-formulation optimization.
High-Tm anchoring phosphatidylethanolamine (PE)	1069-79-0	D130471	1,2-distearoyl-sn-glycero-3-phosphoethanolamine	≥97%	Commonly used for liposome surface modification, ligand/polymer conjugation, and as a stable anchoring lipid.
PEGylated phosphatidylethanolamine (PEG-PE)	474922-77-5	M1439884	18:0 mPEG1000 PE ammonium	—	Provides steric hindrance and a hydrophilic protective layer; commonly used to reduce aggregation and protein adsorption, prolong circulation, and serve as a surface-functionalization anchor.

Note: The above are representative Aladdin products. For more product specifications, please refer to the product list at the end of the article or search the Aladdin website using the “product name/CAS/catalog number.”

References

[1] Marsh D. Structural and thermodynamic determinants of chain-melting transition temperatures for phospholipid and glycolipid membranes. Biochimica et Biophysica Acta (BBA) - Biomembranes. 2010;1798(1):40-51. doi:10.1016/j.bbamem.2009.10.010.

[2] Musakhanian J, Rodier JD, Dave M. Oxidative Stability in Lipid Formulations: A Review of the Mechanisms, Drivers, and Inhibitors of Oxidation. AAPS PharmSciTech. 2022;23(5):151. doi:10.1208/s12249-022-02282-0.

[3] U.S. Food and Drug Administration. Liposome Drug Products: Chemistry, Manufacturing, and Controls; Human Pharmacokinetics and Bioavailability; and Labeling Documentation. Guidance for Industry. Silver Spring, MD: U.S. Food and Drug Administration; 2018. FDA guidance webpage updated October 4, 2021.

[4] Wang J, Yu C, Zhuang J, Qi W, Jiang J, Liu X, Zhao W, Cao Y, Wu H, Qi J, Zhao RC. The role of phosphatidylserine on the membrane in immunity and blood coagulation. Biomarker Research. 2022;10(1):4. doi:10.1186/s40364-021-00346-0.

[5] Wang C, Gamage PL, Jiang W, Mudalige T. Excipient-related impurities in liposome drug products. International Journal of Pharmaceutics. 2024;657:124164. doi:10.1016/j.ijpharm.2024.124164.

[6] Alrbyawi H, Poudel I, Annaji M, Boddu SHS, Arnold RD, Tiwari AK, Babu RJ. pH-Sensitive Liposomes for Enhanced Cellular Uptake and Cytotoxicity of Daunorubicin in Melanoma (B16-BL6) Cell Lines. Pharmaceutics. 2022;14(6):1128. doi:10.3390/pharmaceutics14061128.

[7] Guo X, MacKay JA, Szoka FC Jr. Mechanism of pH-triggered collapse of phosphatidylethanolamine liposomes stabilized by an ortho ester polyethyleneglycol lipid. Biophysical Journal. 2003;84(3):1784-1795. doi:10.1016/S0006-3495(03)74986-8.

[8] van Hoogevest P, Wendel A. The use of natural and synthetic phospholipids as pharmaceutical excipients. European Journal of Lipid Science and Technology. 2014;116(9):1088-1107. doi:10.1002/ejlt.201400219.

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