Entrapment efficiency methodology for lipid nanoparticles – a literature review

• Review of status quo for the use and description of lipid nanoparticles’ entrapment efficiency methods • Overview on applied methodologies and their challenges • practical insight recommendations for formulation scientists in addressing different challenges • Proposal for the design and reporting of entrapment efficiency analytical methods to facilitate reproducibility Lipid nanoparticles have been used for decades to deliver lipophilic drugs. The success of particle formation and drug loading is determined by excipient selection and the production process. Entrapment efficiency (EE) as a measure for process effectiveness and drug load are critical quality attributes of lipid nanoparticles. To determine EE, the nanodispersion must be separated to determine the amount of drug inside the nanoparticles or to measure the amount of un-encapsulated drug in the medium. This review systematically analyses opportunities and challenges of different EE methods. 109 studies were included. The methodology used for EE appears to be chosen on a case-by-case basis and is often reported without a thorough method description. 78 studies (72%) reported the EE method with enough detail to readily attempt experimental reproduction. This review underlines the need for thorough reporting of the principles and method used to determine entrapment efficiency to allow data interpretation.