RESUMEN

Polymer-borne leachables such as formaldehyde, acetaldehyde, and N-3-(Dimethylamino)propyl)methacrylamide (DMAPMA) may interact with therapeutic proteins. In this study, the leachables were spiked into human derived coagulation factor IX (FIX) at concentrations of 1, 10, 50, 100, and 500 µg/mL, corresponding to a leachable - FIX ratio of 0.5, 5, 25, 50 and 250 %, respectively. The spiked samples were visually inspected, and pH was measured. No visual effects were observed, and pH was within the drug product's specified range. Recovery experiments were performed and no loss of leachables was identified. Protein structure analysis revealed that formaldehyde reacted with lysine contained in two different positions of FIX, in a concentration-dependent manner starting at 10 µg/mL (5 %). The clotting activity of FIX was measured. The activity of the samples spiked with 500 µg/mL (250 %) of formaldehyde dropped by more than half. The activity of the samples spiked with acetaldehyde began to drop at 50 µg/mL (25 %) and continued to decline in concentration-dependent manner. DMAPMA did not impair the activity of FIX. The findings conclude that depending on the concentration, some leachables may react with or modify therapeutic proteins, potentially causing an undesired pharmacological effect however, this is specific to each protein.

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RESUMEN

The present study was undertaken to investigate the effect of the composition of the polymerization medium and the type of drug/drug loading process on the mechanical strengths and release profiles of poly(N-isopropylacrylamide-co-N-[3-(dimethylamino)propyl] methacrylamide) P(NIPAAm-co-DMAPMAAm) hydrogels. In line with this goal firstly, the temperature- and pH-responsive hydrogels of NIPAAm and DMAPMAAm were synthesized in three different media at 60 °C: pH 7.4 phosphate-buffered saline (PBS), pH 7.4 phosphate buffer without NaCl/KCl (PB), and distilled-deionized water (pH ≈ 5.5 DDW). The result is that the presence of anionic species such as phosphate (HPO42-/H2PO4-) and chloride (Cl-) ions in the solution affects on their basic network properties such as volumetric swelling ratio and compression modulus. To evaluate their intermolecular interactions with protonated DMAPMAAm units and drug molecules, depending on composition, type of loading process and drug structure, each of the hydrogels was loaded with diclofenac sodium (DFNa) and theophylline (Thp) by using both diffusion and in situ loading methods. DFNa and Thp release profiles in pH 7.4 PBS at 37 °C were analysed by using zero-order, first-order, Higuchi, Korsmeyer-Peppas, and Peppas-Sahlin models. It has been observed that for the first 60% of DFNa and Thp releases from P(NIPAAm-co-DMAPMAAm) hydrogels synthesized in PB at 60 °C, the contribution of the chain relaxation for the copolymer hydrogels loaded during gelation process was higher than the ones loaded by diffusion process.

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RESUMEN

We highlight microgel/enzyme thin films that were deposited onto solid interfaces via two sequential steps, the adsorption of temperature- and pH-sensitive microgels, followed by their complexation with the enzyme choline oxidase, ChO. Two kinds of functional (ionic) microgels were compared in this work in regard to their adsorptive behavior and interaction with ChO, that is, poly(N-isopropylacrylamide-co-N-(3-aminopropyl)methacrylamide), P(NIPAM-co-APMA), bearing primary amino groups, and poly(N-isopropylacrylamide-co-N-[3-(dimethylamino) propyl]methacrylamide), P(NIPAM-co-DMAPMA), bearing tertiary amino groups. The stimuli-sensitive properties of the microgels in the solution were characterized by potentiometric titration, dynamic light scattering (DLS), and laser microelectrophoresis. The peculiarities of the adsorptive behavior of both the microgels and the specific character of their interaction with ChO were revealed by a combination of surface characterization techniques. The surface charge was characterized by electrokinetic analysis (EKA) for the initial graphite surface and the same one after the subsequent deposition of the microgels and the enzyme under different adsorption regimes. The masses of wet microgel and microgel/enzyme films were determined by quartz crystal microbalance with dissipation monitoring (QCM-D) upon the subsequent deposition of the components under the same adsorption conditions, on a surface of gold-coated quartz crystals. Finally, the enzymatic responses of the microgel/enzyme films deposited on graphite electrodes to choline were tested amperometrically. The presence of functional primary amino groups in the P(NIPAM-co-APMA) microgel enables a covalent enzyme-to-microgel coupling via glutar aldehyde cross-linking, thereby resulting in a considerable improvement of the biosensor operational stability.