FURTHER HISTOLOGICAL EVIDENCE OF THE GASTROINTESTINAL ABSORPTION OF POLYSTYRENE NANOSPHERES IN THE RAT

Further histological evidence of the oral absorption of fluorescent polystyrene nanospheres is presented. Fluorescent polystyrene microspheres of diameter ranging from 50 nm to 3-mu-m were administered daily for 10 days by oral gavage (2.5% w/v; 12.5 mg kg-1) to female Sprague Dawley rats. All except the 3-mu-m non-ionic fluorescent polystyrene nanospheres and microspheres were concentrated in the serosal layer of Peyer's patches and could be seen thereafter traversing the mesentery lymph vessels. The migrating particles were subsequently found in the lymph nodes and liver tissues. No particles were found in the lung or heart. We have previously shown that uptake and translocation is size dependent, increasing with decreasing size. Special emphasis is placed on the fate of the smallest particles investigated - 50 nm non-ionic polystyrene microspheres - which were seen in kidney and were also present in the villi and GI crypts.