Sodium selenite se

Chitosan (Cs) with 75–85% deacetylation and 310–375 kDa molecular weight, sodium selenite (Se), and tripolyphosphate (TPP) were obtained from Sigma-Aldrich Co (St Louis, MO, USA). Other chemicals used in this project were all analytical grade, and used without further purification. Deionized water (DIW) was used for this investigation. Cs–NPs were prepared according to a published method [25 (link)]. Briefly, a Cs solution was obtained by adding 0.5 g of Cs powder to 25 mL of 1% (by wgt) acetic acid with continuous stirring for 3 h at room temperature. Separately, 0.1 g of sodium selenite was added to 15 mL of DIW and dissolved by shaking vigorously. The Se solution was then added to the Cs solution. The ratio of Cs to TPP by weight was 2.5:1, so 0.2 g of TPP was dissolved in 10 mL of DIW and slowly added to the Cs-Se solution. The coagulum of TPP–crosslinked Cs was left to stir overnight at room temperature and subsequently, washed with excess DIW to remove unreacted starting materials. Lastly, the Cs–Se NPs were lyophilized.

Slices were cultured for a total of 72h at atmospheric oxygen level (21% O₂) rested on an insert (0.4 µm pore size, Millicell^®, Millipore, Ireland) placed in a culture dish containing complete culture media, as previously described (20 (link)) except the addition of diphenyl diselenide. After 24h, slices were treated during subsequent 48h of culture by replacing the culture medium with a fresh medium spiked with the following drugs and concentrations: sodium selenite (Se, Sigma-Aldrich, Darmstadt, Germany) at 5 µM, 15 µM and 30 µM, and gemcitabine at 1 µM concentration. Untreated cultured slices were used as controls (referred to as Control 72h). The different treatment conditions were tested in duplicate slices.