Characteristics of the hybrid PLA NPs/MMC-SPC. (A) Particle size with particle size distribution. (B) Zeta potential. (C) SEM image. Inset: confocal laser scanning microscopy images of the hybrid PLA NPs/FITC-MMC-SPC (FITC was conjugated with MMC via a thiourea linkage). Scale bar = 500 nm. (D) TEM image. (E) In vitro stability in PBS at 37°C. Data are presented as mean ± SD (n =3).