Standard Operating Procedure for Formation of Solid Lipid Nanoparticles (SLNs)

1) Purpose

This SOP provides the steps for preparing solid lipid nanoparticles (SLNs), which are used in drug delivery systems for improving the bioavailability of poorly soluble drugs.

2) Scope

This SOP applies to laboratory personnel involved in the preparation of SLNs using the hot and cold homogenization methods.

3) Responsibilities

• Operators: Responsible for accurately preparing SLNs according to this SOP.
• QA: Ensures SLNs meet the required specifications for particle size, stability, and drug encapsulation.

4) Procedure

4.1 Preparation of Lipid Phase

4.1.1 Lipid Selection

• 4.1.1.1 Select a solid lipid suitable for the drug to be encapsulated (e.g., glyceryl monostearate, Compritol).

4.1.2 Melting the Lipid

• 4.1.2.1 Melt the solid lipid at a temperature 5–10°C above its melting point.

4.2 Drug Incorporation

4.2.1 Drug Loading

• 4.2.1.1 Dissolve or suspend the drug in the molten lipid phase and stir until the drug is uniformly dispersed.

4.3 Formation of SLNs

4.3.1 Emulsification

• 4.3.1.1 Add the molten lipid-drug mixture to an aqueous phase containing a surfactant (e.g., Poloxamer 188) under high-speed stirring to form an emulsion.
• 4.3.1.2 Use a high-pressure homogenizer to reduce the particle size.

4.3.2 Cooling

• 4.3.2.1 Cool the emulsion to room temperature, allowing the solid lipid to recrystallize, forming SLNs.

4.4 Washing and Collection of SLNs

4.4.1 Centrifugation

• 4.4.1.1