Strategies for further stabilization of lipid-based delivery systems with a focus on solidification by spray-drying

Background: Today, lipid-based delivery systems (LBDS: emulsions, nanostructured lipid carriers, solid lipid nanoparticles, lipid-polymer hybrid nanoparticles, and nanoliposomes) are widely used for stabilization, bioavailability improvement, controlled and targeted delivery of bioactive compounds and drugs. However, challenges such as structural, physicochemical, and thermodynamic instabilities, microbial and oxidative reactions, leakage/fusion and unwanted release of loaded bioactives have reduced the stability and usability of these systems. Therefore, many efforts have been made to stabilize these systems. Scope and approach: In this review, various methods for stabilizing LBDS such as membrane modifications, changes in formulation, addition of stabilizers, emulsifiers or biopolymers as coating agents have been discussed. Also, the most important advantages and results obtained from spray-drying of LBDS (e.g., physicochemical characteristics, oxidative stability, chemical structure, morphological changes and retention of loaded bioactives) are investigated. Hence, some challenges related to process parameters (such as shear stresses during atomization, structural and membrane destruction of particles and problems of their reconstitution) have been described. Key findings and conclusions: Maintaining the biological activity of loaded bioactives and the stability of LBDS during storage are still among the most important challenges associated with these carriers. Long-term stabilization of LBDS through solidification by spray-drying has been associated with many advantages. Today, significant results have been achieved in the field of maintaining the physical structure of lipid membrane and nanoparticles (especially retention of the encapsulation efficiency after reconstitution) during shear and thermal stresses through stabilizers or biopolymeric coatings. However, maintaining the system's bioavailability and biological activity of loaded compounds, especially in food/drug formulations and in vivo conditions, requires further research.