PK NPs with carboxyl groups on the surface showed the lowest zeta potential (-9.7 ± 1.1 mV) among all NPs. Compared to PK NPs, LPK– NPs exhibited positively shifted zeta potential, which might be attributed to the shielding effect of selleck chemicals DSPE-PEG (2000) and the small amount of amine groups on PEG molecules [17]. The positive zeta potentials of LPK++ and LPK+ NPs are probably attributed to the positive charges carried by DOTAP. The results from zeta potential measurement demonstrated that the surface charges of hybrid NPs can be flexibly controlled by modulating the lipid composition. Figure 1 Schematic illustration and TEM images of the

NPs. (A) Schematic illustration of PK NPs. (B) Schematic illustration of LPK NPs. (C) TEM image of PK NPs, which highlights the uniform size and spherical shape of PK NPs. (D) TEM image of hybrid LPK NPs, which shows the lipid-bilayer-enclosed Ilomastat PK NPs. The scale bars represent 200 nm. Table 1 Components, physicochemical properties, and KLH content of various NPs Group Components of NPs (mg) Size (dm. nm) Polydispersity Zeta potential (mV) KLH content (%)   PLGA KLH DOTAP DOPC DSPE-PEG   PK 200 3 0 0 0 191.0 ± 15.3 0.199 ± 0.012 -9.7 ± 1.1 1.12 ± 0.21 LPK ++ 200 3 16 0 4 213 ± 38.7 0.231 ± 0.022 13.9 ± 1.3 1.11 ± 0.22 LPK – 200 3 2 14 4 232.4 ± 34.5 0.248 ± 0.018 -3.6 ± 1.4 1.05 ± 0.10 LPK + 200 3 14 2 4 222.6 ± 21.0 0.240 ± 0.019

6.4 ± 1.1 0.92 ± 0.15 LPK — 200 3 0 16 4 208.0 ± 12.0 0.219 ± 0.023 -5.5 ± 0.9 0.84 ± 0.03 Incorporation of long-chain PEG https://www.selleckchem.com/products/bmn-673.html molecules on the surface of NPs is of significant importance as they can not only

protect NPs O-methylated flavonoid from degradation by enzymes during in vivo circulation [18], increasing the stability of NPs and prolonging circulation time [19], but also allow the inclusion of reactive groups in PEG molecules to offer flexible conjugation of various antigens [20]. For targeted delivery purposes, antibodies or affinity ligands against receptors of target cells or tissues may be conjugated to the surface of NPs via PEG chains [21, 22]. The morphology of NPs was studied using TEM. Consistent with the particle size measured using dynamic light scattering (DLS) (Table 1), both PK NPs (Figure 1C) and LPK NPs (Figure 1D) displayed a highly uniform particle size (around 200 nm) and narrow size distribution. Most of the NPs showed a smooth surface and were of a spherical shape. Compared to PK NPs, there is a gray membrane covering LPK NPs (Figure 1D), demonstrating the successful hybridization of PK NPs and liposomes. The thickness of the membrane is around 20 nm, which is equal to the thickness of a lipid bilayer [15]. To further confirm that PK NPs were successfully hybridized with lipids, LPK NPs comprising PK NPs (KLH was labeled with rhodamine B (red color)) and lipid layers (lipids were labeled with nitro-2-1,3-benzoxadiazole (NBD) (green color)) were examined using confocal LSM.