Based on the last paragraph, it is safe to say that the current strategy for improving the efficiency of drug delivery systems is to figure out how the structural parameters of CSHNs affect the performance of drug delivery systems. An excellent example of this idea is the research conducted by Leng et al . In it, researchers recognized that corticosteroids, which are effective therapeutics for chronic inflammation, are unable to reduce the number of inflammatory cells and cytokines in chronic obstructive pulmonary disease. To overcome this limitation, it was hypothesized that co-administration of budesonide (a corticosteroid) with a second anti-inflammatory agent (e.g., siRNA) might increase therapeutic efficacy because they can simultaneously target different sites. Therefore, the researchers prepared LPNs from PLGA and the cationic lipid dioleyltrimethylammonium propane (DOTAP) and used a quality-bydesign (QbD) approach to determine the optimal formulation parameters. Their results showed that the critical formulation parameters (CFPs) were the theoretical budesonide loading and the theoretical DOTAP loading and that these two parameters were related to two structural parameters: the hydrodynamic particle diameter (z-mean) and the polydispersity index (PDI).