*4.1. Materials*

Glucose and human insulin solutions (Sigma-Aldrich, St. Louis, MO, USA) were freshly prepared in RPMI-1640 (low glucose—5.5 mM, Biological Industries, Cromwell, CT, USA) supplemented with 2% fetal bovine serum (FBS) and 100 μg/mL penicillinstreptavidin (both from Sigma-Aldrich, St. Louis, MO, USA). Concentration ranges from 5–500 mM for glucose and 10–750 μM for insulin were chosen for the evaluation of the cytotoxicity effect. PC12 cells—pheochromocytoma cells derived from the adrenal gland of *Rattus Norvegicus*—were purchased from ATCC (Manassas, VA, USA). The differentiation was performed using human recombinant *β* nerve growth factor, NGF-*β* (Sigma-Aldrich, St. Louis, MO, USA) dissolved in PBS to a stock concentration 1 μg/mL and stored at −20 ◦C for up to 2 weeks.
