| Cardiovascular disease (CVD) is one of the most common causes of death worldwide. Thus, the development of drug delivery systems targeting the cardiovascular system is of great importance for the treatment of CVD. In this study, we used coenzyme Q10 (CoQ10) as a model drug to design CoQ10-loaded nanoemulsions (CoQ10-NEs). In vitro and in vivo experiments were conducted to examine the effect of D-α-tocopheryl polyethylene glycol succinate (TPGS) and its cationic amino acid derivatives on CoQ10-NE myocardial targeting. These results will lay a foundation for the application and development of myocardial-targeted CoQ10-NEs.CoQ10-NEs composed of CoQ10, caprylic/capric triglyceride (GTCC), and lecithin were prepared by melt emulsification and high-pressure homogenization. The particle size, surface potential, encapsulation efficiency, stability, and phase transition behavior of the CoQ10-NEs were evaluated, with particular emphasis on the effects of CoQ10/GTCC and particle size on the crystallinity of CoQ10. Our results indicated that CoQ10-NEs prepared by this method have a regular, spherical morphology, with an encapsulation efficiency greater than 98%. The photolysis rate of CoQ10 in the CoQ10-NEs was reduced by 80.2%, as compared to CoQ10 in solution. Particle size was shown to be a key factor influencing CoQ10 crystallinity. Thus, preparation of CoQ10-NEs without GTCC can be implemented using particle size control.Next, cationic histidine (His) and lysine (Lys) derivatives of TPGS (TPGS-His and TPGS-Lys) were prepared and verified by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF),1H nuclear magnetic resonance (NMR), and Fourier transfer infrared (FT-IR) spectral data. CoQ10-NEs (50 nm) composed of CoQ10 and lecithin were prepared by melt emulsification and high-pressure homogenization, followed by surface modification with TPGS, TPGS-His, and TPGS-Lys. In vivo experiments were performed in rats to assess the effect of TPGS, TPGS-His, and TPGS-Lys on CoQ10-NE pharmacokinetics, tissue distribution, and myocardial targeting. Our results showed that both CoQ10-NEs-TPGS and CoQ10-NEs-TPGS-His could target the myocardium, whereas CoQ10-NEs and CoQ10-NEs-TPGS-Lys did not. These data indicate that TPGS and TPGS-His can target CoQ10-NEs to the myocardium. Additionally, the effect of particle size on CoQ10 levels in the myocardial tissue was examined. Myocardial targeting of CoQ10-NEswas enhanced by reducing particle size.Finally, in vitro experiments were performed in a cardiomyocyte cell line. Fifty nanometer CM6-CoQ10-NEs, CM6-CoQ10-NEs-TPGS, CM6-CoQ10-NEs-TPGS-His, and CM6-CoQ10-NEs-TPGS-Lys were prepared with coumarin-6 (CM6) as a fluorescent tag, and their interactions with cardiomyocytes were evaluated. Kinetic analyses of cellular uptake showed that cationic TPGS-His and TPGS-Lys significantly promoted cellular uptake of CoQ10-NEs, rapidly increasing the concentration of intracellular CM6 within 30 min. Interestingly, TPGS-Lys had a stronger effect than TPGS-His. Additionally, hypoxic culture conditions significantly enhanced the uptake of cationic CM6-CoQ10-NEs-TPGS-His and CM6-CoQ10-NEs-TPGS-Lys by cardiomyocytes, whereas non-cationic TPGS had an inhibitory effect. Inhibition of endocytosis revealed that CoQ10-NEs and CoQ10-NEs-TPGS transported CM6 into the cell via the clathrin endocytic pathway, whereas CoQ10-NEs-TPGS-His and CoQ10-NEs-TPGS-Lys transported CM6 via a non-endocytic pathway. Laser confocal microscopy analyses revealed that the four CoQ10-NEs were widely distributed in the cell cytoplasm, outside the nucleus. Furthermore, CoQ10-NE uptake resulted in mitochondrial distribution of CM6 within the cell. Moreover, TPGS-His enhanced the ability of CoQ10-NEs to transport CM6 into the mitochondria, whereas TPGS and TPGS-Lys inhibited CM6 transport into the mitochondria. |
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