Facile synthesis and rheological characterization of nanocomposite hyaluronan-organoclay hydrogels.

We report a facile methodology for the synthesis of inorganic-organic hydrogels based on integrative assembly of aminopropyl magnesium phyllosilicate (aminoclay) and sodium salt of hyaluronic acid. The viscoelastic materials produced by electrostatic interactions and crosslinking of hyaluronan in the presence of exfoliated synthetic organoclay results in the formation of gel-like behavior retaining a high amount of water. This was confirmed by a rheological study revealing significant dominance of the elastic response over the entire deformation frequency range used. The mechanical strength of the aminoclay-hyaluronan hydrogels was found to be higher than that for related materials based on poly(vinylpyrrolidone)-aminoclay hydrogels.

Learning and memory effects of four newly-synthesized aniracetam analogues.

Four new analogues of the pyrolidine derivative with nootropic action--aniracetam--were synthesized using classical methods. The effects of the newly-synthesized compounds were tested using the step-through method for passive avoidance with negative reinforcement and the method of habituation of exploratory activity in the Opto-Varimex apparatus. Two series of experiments were performed using the step-through method: in one series aniracetam (Anc) and its analogues p-H and p-Cl were applied twice daily in a dose of 50 mg/kg for 7 days prior to the training session; retention tests were made 3 h, 24 h and 7 days after the training session. In the other series of experiments the Anc analogues p-P (in single daily doses of 10, 50 and 250 mg/kg) and p-F (in a single daily dose of 50 mg/kg) were applied for 5 days prior to the training session; memory tests were performed 24 h and 7 days after the training session. In one of the experimental series in Opto-Varimex, after 5-min recording of the horizontal, vertical and rotatory movements of each rat, the various groups of animals received 20, 100 or 300 mg/kg from each of the agents tested (Anc, p-Cl and p-H). Tests for habituation were performed 7 days later. The other series of experiments in Opto-Varimex included groups of rats receiving 50 mg/kg Anc, p-Cl and p-H twice daily for 7 days. The three types of movement were recorded for 5 min in the Opto-Varimex after the last dose of the substances tested. All substances were administered orally. The results obtained (longer time spent by the animals in the illuminated section when the step-through method was used and enhanced habituation in the Opto-Varimex experiments) suggest that the substances tested improve the memory, mainly through improving the process of consolidation of the memory traces.