Fig. 5

Representative TEM images of human endothelial cells exposed to HA particles (50 μg/mL). The cytoplasm contained a variable number and size of vesicles loaded with the particles (a–c, HAp1; f–h, HAp2). High magnification images showed a close interaction of the particles with the cell membrane (d, HAp1). Particles did not enter the nucleus (e, HAp1), maintained their characteristic size and shape inside the vesicles (i, HAp2; j, HAp1) and evidence of particle dissolution was attained (j, HAp1; l, HAp2). In the cell vicinity, particles are seen mostly as aggregates (m, HAp1) and close to these structures, cell membrane exhibits a characteristic morphology with the emission of abundant and large pseudopodia extensions (m, HAp1) that appear very efficient in entrapment (n, HAp2). Insets: extracellular aggregates, HAp1 (a) and HAp2 (f). Bar: a–c, f, g = 1 μm; e, m, n = 500 nm; d, h; i = 200 nm; j, l = 50 nm