Preparation of Lycopene Micelles with Different Block Ratios of mPEG-PLA as Carriers and the Solubilization and Controlled Release of Lycopene Isomers

By applying three different block ratios of polyethylene glycol monomethyl ether-polylactic acid (mPEG-PLA) copolymers as carriers, the lycopene micelles (M-LYC) were created by emulsification-solvent evaporation method. The content of each isomer of lycopene (LYC) in M-LYC was determined by high performance liquid chromatography (HPLC), and the encapsulation rate (EE) and drug loading capacity (DL) of micelles were calculated. To screen the mPEG-PLA copolymers for the ideal block ratio of encapsulating LYC, the particle size and zeta potential were evaluated using a dynamic light scattering nano-particle size analyzer, and the in vitro release of M-LYC in different release media was assessed using dialysis method. The results showed that the EE of Total LYC in mPEG₄₅-PLA₃₆-M-LYC, mPEG₁₁₄-PLA₉₀-M-LYC, and mPEG₁₁₄-PLA₁₈₀-M-LYC were 65.04%, 71.73% and 23.62%, respectively, with DL of 3.96%, 4.43% and 1.39%, particle sizes of 164.6, 190.1 and 210.3 nm, and zeta potential of −15.38, −9.43 and −10.96 mV, respectively. The EE of each isomer and Total-LYC in mPEG₁₁₄-PLA₉₀-M-LYC was the highest, followed by mPEG₄₅-PLA₃₆-M-LYC. The order of encapsulation rate of each cis-isomer in the three micelles was 5Z>9Z>13Z. The mPEG₄₅-PLA₃₆-M-LYC had the smallest particle size and the largest absolute value of zeta potential among the three micelles, indicating that it had the best stability. The release of LYC in LYC feedstock was not detected in different release media. Among the three micelles, the mPEG₄₅-PLA₃₆-M-LYC had the highest cumulative release percentage of Total LYC within 72 h in different release media, with 42.35% (pH6.8) and 60.82% (pH7.4), respectively. The cumulative release percentages of all three micelles in the pH7.4 release medium were higher than those in the pH6.8 condition, and the cumulative release percentages of all-trans lycopene (All-E) were slightly higher than those of Total LYC within 72 h. 5Z had the higher cumulative release percentages than All-E after 72 h, with no initial release. In conclusion, the mPEG₄₅-PLA₃₆ has a better effect on the encapsulation of LYC than other copolymers. The M-LYC prepared with its carrier has the smallest particle size, the largest absolute zeta potential, the best stability and the highest cumulative release percentage of 72 h Total LYC among the three micelles, which is a promising polymeric carrier material for encapsulating LYC and is expected to improve the in vivo bioavailability of fat-soluble nutrients.