Production of model drug carried liposomes by means of a SDR for dermatology applications

An interest in the production of unilamellar liposomes (ULs) as a drug carrier vector for a wide range of different substances is increasing, in particular for dermatology applications. Formulations of concentrated unilamellar liposomes (ULs) with controlled size below 400 nm enhance the efficiency of drug delivery in topical skin applications, primarily by improving local deposition and retention of the encapsulated compound, rather than penetration of intact vesicles. In a recent work, a spinning disk reactor (SDR) was used to produce UL suspensions. The same method of production was here applied, focusing on encapsulation of Rhodamine as a drug model substance. The production protocol was optimized for dermatological applications, targeting a modal size of 180 nm with a narrow polydispersity index (PDI), chosen to balance stability, payload, and dermal deposition efficiency. After the suspension production, the ULs were concentrated and recovered from the solution by adopting a membrane separation process. The obtained results validate the suggested approach, demonstrating that the adopted SDR is capable of producing ULs of the desired size of 180 nm with a PDI of 0.28, encapsulating 65 % of the Rhodamine at a rate of 14.4 L day⁻¹. Liposomes as small as 60 nm were also produced, but were not selected for dermatological applications due to lower payload and reduced deposition in deeper skin layers. Using ultrafiltration (UF), it was possible to separate the ULs from the bulk liquid, allowing recycling of unencapsulated drug and obtaining concentrated liposomes containing 1.12 µg mL⁻¹ Rhodamine for topical formulations. Finally, a process scheme is proposed as an example of a possible industrial production of drug-loaded liposomes.