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ABSTRACT In this work, four polymerization mechanisms with flow are proposed where sustained oscillation can be present: (1) Polyaddition initiated by radicals produced by initiator decomposition, which is catalyzed by the polymer, first-order termination, a polymer disappears by a reaction with a third substance and by leaving the system in the exit flow. (2) Polycondensation where the polymer has catalytic activity upon H to produce a monomer, first-order termination and a monomer disappears by a reaction with a third substance, and there is exit flow for all the species. (3) Polycondensation with catalytic activity of the polymer upon A to produce a monomer, first-order termination, conformational transitions of the polymers, one of the polymer conformations disappears by a reaction with a monomer and exit flow for all the species. (4) Polycondensation combined with polyaddition where the polycondensation polymer product has catalytic activity on the monomer, first-order termination and exit flow of all the species. [ABSTRACT FROM AUTHOR]

Chitosan nanogels functionalized with folic acid and crosslinked with PEG diacid or tartaric acid have been prepared by inverse microemulsion method for targeted delivery into cancer cells. Nanogels with varying degrees of crosslinking (4.5–10 mol% of crosslinker) have been obtained. The particle sizes determined by TEM are below 50 nm with narrow size distributions. Nanogels show a clear improvement in solubility compared with pure chitosan. Their swelling ability is pH sensitive, due to the protonation of the free amino groups when the pH is varied from 10 to 4. The nanogels have been loaded with 5-fluorouracil, which is retained at pHs greater than 7.4 and released at pH = 5.5. These nanoparticles are degraded by lysozyme at physiological pH in a period of 20 days and are easily labeled with fluorescein isothiocyanate. All these features make them promising materials for the controlled release of anticancer drugs. [ABSTRACT FROM AUTHOR]

In order to evaluate the influence of some body fluids on the hydrogels (HG) properties, in this work was studied the absorption properties of semi-interpenetrating (IPN) HG obtained from acrylamide (AAm) and chitosan (Q). To achieve this objective we employment a Hanks balanced salt solution, which is a physiological fluid that simulates the blood plasma. The semi-IPN hydrogels synthesized from AAm and Q, were subjected to absorption studies by gravimetric analysis, both in deionized water as in Hanks solution. The results of kinetic parameters indicated that the addition of Q to polyacrylamide (PAAm) hydrogel slightly increases the absorption capacity of the fluid and the Q confers greater affinity with Hanks solution. The X-rays diffraction analysis showed interaction between HG and the constituent elements of the Hanks solution. The results obtained confirm that the HG exhibit good affinity with the simulated body fluid, and therefore have great potential for medical applications. [ABSTRACT FROM AUTHOR]