NANOSPHERE AND MICROSPHERE UPTAKE VIA PEYER PATCHES - OBSERVATION OF THE RATE OF UPTAKE IN THE RAT AFTER A SINGLE ORAL DOSE

Polystyrene latex particles of diameter 50 nm, 500 nm and 1 mum were fed by oral gavage as a single dose to female Sprague-Dawley rats. At intervals following administration, histological examination of tissues allowed the uptake and movement of the particles to be monitored, at least semiquantitatively. Uptake is relatively rapid. At 6 h, 50 nm particles were seen in considerable numbers in Peyer's patches. The rate of uptake is particle-size dependent, smaller particles gaining access to all tissues more rapidly. At 6 h, 50 nm particles can also be detected in the mesentery, while 1 mum particles cannot be observed until about 12 h after administration. Peak concentrations of 500 nm and 1 mum particles occur in the Peyer's patches at 18 h and in the lymph nodes at 12 and 24 h, respectively. Particles of 500 nm and 1 mum appear in the liver after 18 h, 50 nm particles reaching this organ in small quantities in 12 h.