Investigating stimuli-responsive liposomes for cutaneous applications: a guide to stimuli recognition and characterization

In recent years, stimuli-responsive liposomes have been proposed as advanced nanocarriers for cutaneous drug delivery. These liposomes are designed to release their cargo in response to specific triggers. A critical challenge in their development is the robust characterization of this responsive behavior to validate their performance. This review provides a methodological guide for comprehensively characterizing stimuli-responsive liposomes. The proposed guide systematically discusses experimental and computational characterization techniques based on the evidence they provide regarding structural transformation, functional outcomes and molecular mechanisms, and focuses on recent studies in cutaneous applications published within the last decade. A multifaceted characterization approach is essential as no single technique is sufficient. Structural techniques such as small angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM) provide direct evidence of stimuli-induced physical changes, that need to be correlated with functional data obtained using analytical techniques such as high-performance liquid chromatography (HPLC) to quantitatively determine drug release. Complementary computational simulations can elucidate molecular-level mechanisms, supporting rational formulation design. A comprehensive characterization framework is therefore essential for effective design and clinical application of stimuli-responsive liposomal formulations, facilitating the development of safer and more efficient cutaneous therapies.