Cationic liposomes,as non-viral vectors,are widely used in gene therapy and gene silencing.Although numerous cationic liposomes have various structures,they can all improve the per-formance of gene delivery.As gene therapy is increasingly studied,it may be foreseen that new cationic lipoplexes will be explored.In this review,we aim to discuss four constituent domains of cationic lipids(headgroup,hydrophobic domain,linker and helper lipids)in gene delivery.This article attempts to demonstrate that various lipid structures show different transfection efficiency and cytotoxicity by sum-marizing the similarities and differences between the four parts of cationic lipids.Furthermore,their major influencing factors are covered.Finally,three clinical cases of ionizable lipids are described to reveal their characteristics and differences from cationic lipids.This paper is intended to provide a conceptual framework for the design of cationic liposomes and for the selection of cationic lipids.

Over the past 30 years,nano-drug delivery systems(NDDS)have become a promising field of drug research.However,a poor knowledge of the in vivo process of NDDS,the limited methods of pharmacokinetic correlation,and the inability to effectively provide strong support for the construction of upstream drug as well as the evaluation of downstream pharmacology and toxicology have become the technical bottleneck for their clinical transformation.Lipid nanodrug(LND)is the most successful NDDS for industrial transformation with great biocompatibility.Taking LND as an example,this paper reviewed the delivery process and influencing factors in vivo,and summarized the regulatory mecha-nism of biological environments on drug release in vivo.Based on advanced spectroscopy and mass spectrometry techniques,the spatial and temporal distribution of the dynamic carrier particle/depolymer-ized molecule ratio and dynamic free/encapsulated drug ratio of LND in biological matrix were ana-lyzed.Finally,the existing problems and future developments in this field were summarized to provide references for the analysis of NDDS in vivo,and stimulate readers'interest in nanomedical research and development.