Phospholipids: Derived from natural sources such as egg or soy lecithin. These phospholipids are commonly used in liposome formulations for their biocompatibility and natural membrane-like properties.

Synthetic Phospholipids: Chemically modified phospholipids such as hydrogenated or pegylated phospholipids. These phospholipids are often used to enhance liposome stability and control drug release.

Charged Phospholipids: Phospholipids like dimyristoylphosphatidylcholine (DMPC) or dipalmitoylphosphatidylcholine (DPPC) that can impart either a positive or negative charge to the liposome, affecting its interaction with target tissues or cells.

4.1.2 Selection Criteria

• 4.1.2.1 Select phospholipids based on the desired liposome characteristics (e.g., stability, particle size, encapsulation efficiency).
• 4.1.2.2 Ensure compatibility of the phospholipid with the drug or active ingredient being encapsulated in the liposome.
• 4.1.2.3 Consult the formulation protocol or batch manufacturing record (BMR) for the specific type and quantity of phospholipid to be used.
• 4.1.2.4 Choose phospholipids with a suitable phase transition temperature (Tm) based on the temperature conditions of the intended application.

4.2 Handling and Preparation of Phospholipids

Phospholipids are sensitive to oxidation and must be handled with care to prevent degradation. The following steps outline the proper handling and preparation of phospholipids for liposome formulations:

4.2.1 Storage of Phospholipids

• 4.2.1.1 Store phospholipids in airtight containers at low temperatures (typically -20°C or lower) to prevent oxidation and degradation.
• 4.2.1.2 Protect phospholipids from light exposure by using opaque or amber-colored containers.
• 4.2.1.3 Label all containers with the phospholipid name, batch number, date of manufacture, and expiration date.

4.2.2 Preparation of Phospholipids

• 4.2.2.1 Before use, allow phospholipids to equilibrate to room temperature in a desiccator to prevent moisture absorption.
• 4.2.2.2 Weigh the required amount of phospholipids using an analytical balance. Record the weight in the Batch Manufacturing Record (BMR).
• 4.2.2.3 Dissolve the phospholipids in an appropriate organic solvent (e.g., chloroform, methanol) as per the formulation protocol. Use a magnetic stirrer to ensure complete dissolution.
• 4.2.2.4 Evaporate the solvent to form a thin lipid film, which can then be hydrated with the aqueous phase during liposome preparation.

4.3 Incorporation of Phospholipids into Liposome Formulations

Phospholipids are incorporated into liposome formulations by hydration of the lipid film or by direct mixing with the aqueous phase, depending on the formulation method used.

4.3.1 Lipid Film Hydration Method

• 4.3.1.1 Once the lipid film is formed, hydrate the film by adding the pre-warmed aqueous phase (e.g., buffer or drug solution) to the flask containing the lipid film.
• 4.3.1.2 Vortex the solution or stir gently to ensure that the lipid film is fully hydrated and that liposomes form spontaneously.
• 4.3.1.3 The hydrated liposomes may require further processing (e.g., sonication or extrusion) to achieve the desired size and uniformity.

4.3.2 Direct Solvent Injection Method

• 4.3.2.1 For some formulations, phospholipids can be directly mixed with the aqueous phase by injecting the lipid solution into the aqueous phase under controlled conditions.
• 4.3.2.2 The mixture should be stirred vigorously to ensure even distribution of lipids throughout the aqueous phase.
• 4.3.2.3 Use filtration or centrifugation to remove any large aggregates or unencapsulated material.

4.4 Quality Control of Phospholipids

Phospholipids must meet certain quality specifications before being used in liposome formulations. The following quality control (QC) tests should be performed:

• 4.4.1 Purity testing by thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC).
• 4.4.2 Identity testing using infrared (IR) spectroscopy to confirm the phospholipid structure.
• 4.4.3 Functional testing by measuring the encapsulation efficiency and liposome stability of the phospholipid in test formulations.

5) Abbreviations, if any

• DMPC: Dimyristoylphosphatidylcholine
• DPPC: Dipalmitoylphosphatidylcholine
• QA: Quality Assurance
• QC: Quality Control

6) Documents, if any

• Batch Manufacturing Record (BMR)
• Phospholipid Purity and Identity Test Reports
• Equipment Calibration Logs

7) References, if any

• FDA Guidelines for Liposome Drug Products
• International Conference on Harmonisation (ICH) Q7: Good Manufacturing Practice Guide

8) SOP Version

Version 1.0

Annexure

Annexure 1: Batch Manufacturing Record Template

Batch No.	Phospholipid Name	Weight	Solvent	Method of Incorporation	Operator Initials	QA Signature
Batch Number	Phospholipid Name	Weight in grams	Solvent Name	Lipid Film Hydration/Direct Injection	Operator Name	QA Name