Ionic and Polyampholyte N-Isopropylacrylamide-Based Hydrogels Prepared in the Presence of Imprinting Ligands: Stimuli-Responsiveness and Adsorption/Release Properties

The conformation of the imprinted pockets in stimulus-responsive networks can be notably altered when the stimulus causes a volume phase transition. Such a tunable affinity for the template molecule finds interesting applications in the biomedical and drug delivery fields. Nevertheless, the effect that the binding of the template causes on the stimuli-responsiveness of the network has barely been evaluated. In this work, the effect of two ionic drugs used as templates, namely propranolol hydrochloride and ibuprofen sodium, on the responsiveness of N-isopropylacrylamide-based hydrogels copolymerized with acrylic acid (AAc) and N-(3-aminopropyl) methacrylamide (APMA) and on their ability to rebind and to control the release of the template was evaluated. The degree of swelling and, in some cases, energetics (HS-DSC) of the transitions were monitored as a function of temperature, pH, and concentration of drug. Marked decrease in the transition temperature of the hydrogels, accompanied by notable changes in the transition width, was observed in physiological NaCl solutions and after the binding of the drug molecules, which reveals relevant changes in the domain structure of the hydrogels as the charged groups are shielded. The ability of the hydrogels to rebind propranolol or ibuprofen was quantified at both 4 and 37 °C and at two different drug concentrations, in the range of those that cause major changes in the network structure. Noticeable differences between hydrogels bearing AAc or APMA and between imprinted and non-imprinted networks were also observed during the release tests in NaCl solutions of various concentrations. Overall, the results obtained evidence the remarkable effect of the template molecules on the responsiveness of intelligent imprinted hydrogelsThis work was financed by Ministerio de Ciencia y Tecnología (SAF2011-22771 and MIPFOOD IPT-060000-2010-14) and FEDER Spain, and by the RFBR (Project 04-03-32355) and DCMS RAS (Program “Creation and Study of Macromolecules and Macromolecular Structures of New Generations”)S

Ionic and Polyampholyte N-Isopropylacrylamide-Based Hydrogels Prepared in the Presence of Imprinting Ligands: Stimuli-Responsiveness and Adsorption/Release Properties

The conformation of the imprinted pockets in stimulus-responsive networks can be notably altered when the stimulus causes a volume phase transition. Such a tunable affinity for the template molecule finds interesting applications in the biomedical and drug delivery fields. Nevertheless, the effect that the binding of the template causes on the stimuli-responsiveness of the network has barely been evaluated. In this work, the effect of two ionic drugs used as templates, namely propranolol hydrochloride and ibuprofen sodium, on the responsiveness of N-isopropylacrylamide-based hydrogels copolymerized with acrylic acid (AAc) and N-(3-aminopropyl) methacrylamide (APMA) and on their ability to rebind and to control the release of the template was evaluated. The degree of swelling and, in some cases, energetics (HS-DSC) of the transitions were monitored as a function of temperature, pH, and concentration of drug. Marked decrease in the transition temperature of the hydrogels, accompanied by notable changes in the transition width, was observed in physiological NaCl solutions and after the binding of the drug molecules, which reveals relevant changes in the domain structure of the hydrogels as the charged groups are shielded. The ability of the hydrogels to rebind propranolol or ibuprofen was quantified at both 4 and 37 °C and at two different drug concentrations, in the range of those that cause major changes in the network structure. Noticeable differences between hydrogels bearing AAc or APMA and between imprinted and non-imprinted networks were also observed during the release tests in NaCl solutions of various concentrations. Overall, the results obtained evidence the remarkable effect of the template molecules on the responsiveness of intelligent imprinted hydrogels

The structure of j/i-hybrid carrageenans II. Coil–helix transition as a function of chain composition

This paper describes the effect of the k/i-ratio on the physical properties of k/i-hybrid carrageenans (synonyms: kappa-2, k-2, weak kappa, weak gelling kappa). To this end, a series of k/i-hybrid carrageenans ranging from almost homopolymeric k-carrageenan (98 mol% k-units) to almost homopolymeric-carrageenan (99 mol% i-units) have been extracted from selected species of marine red algae (Rhodophyta). The k/i-ratio of these k/i-hybrids was determined by NMR spectroscopy. Their rheological properties were determined by small deformation oscillatory rheology. The gel strength (storage modulus, G0) of the j/i-hybrids decreases with decreasing j-content. On the other hand, the gelation temperature of the k-rich k/i-hybrids is independent of their composition. This allows one to control the gel strength independent of the gelation or melting temperature. The conformational order–disorder transition of the k/i-hybrids was studied using optical rotation and high-sensitivity differential scanning calorimetry. High-sensitivity DSC showed that the total transition enthalpy of the k/i-hybrids goes through a minimum at 60 mol% k-units, whereas for the mixture of j- and i-carrageenan, the total transition enthalpy is a linear function of the composition. With respect to the ordering capability, the k/i-hybrid carrageenans seem to behave as random block copolymers with length sequence distributions truncated from the side of the small lengths. Intrinsic thermodynamic properties (e.g., transition temperature and enthalpy) of k- and i-sequences in these copolymers are close to those of their parent homopolymers. The critical sequence length for k-sequences is 2-fold of that for i-sequences

Agro-Morphological and Cytogenetic Characterization of Colchicine-Induced Tetraploid Plants of <i>Polemonium caeruleum</i> L. (Polemoniaceae)

Polemonium caeruleum L. (Polemoniaceae) is a valuable medicinal herb with a wide spectrum of biological activities. Under natural conditions, the productivity of this species is rather low. In this study, colchicine-induced tetraploid plants (2n = 4x = 36) of P. caeruleum were obtained, and for the first time, their morphological and cytogenetic characterization was performed. In the tetraploid plants, raw material productivity and also the content of triterpene saponins were significantly higher than in the control diploids. The analysis of chromosome behavior at meiosis and FISH chromosome mapping of 45S and 5S rDNA generally demonstrated stability of both genomes in the tetraploid plants. Based on chromosome morphology and distribution patterns of the studied molecular cytogenetic markers, all chromosome pairs in karyotypes were identified, and chromosome karyograms and idiograms of P. caeruleum were constructed. The revealed specific microdiagnostic characteristics of P. caeruleum (strongly sinuous cells and anomocytic stomata of the leaf epidermis, and also glandular hairs along the veins) could be useful for raw material identification. In the obtained tetraploids, the predominance of large stomata on the lower leaf epidermis was determined. The studied tetraploids can be used in various breeding programs to obtain high-quality pharmaceutical raw materials of P. caeruleum