Novel poly(amidoamine)s (PAAs) containing disulfide linkages regularly arranged along their backbones were synthesized by the stepwise polyaddition of 2-methylpiperazine to N,NЈ-bis(acryloyl)cystamine (BACy1) or N,NЈ-bis(acryloyl)-(L)cystine (BACy2). Both bisacrylamides had, in turn, been obtained by the reaction of acryloyl chloride with the corresponding amines. All the products were characterized with 1 H and 13 C NMR spectroscopy, and the average molecular weights of the polymers were determined by size exclusion chromatography. Both PAAs showed different solubility properties. In particular, PAA-Cy1, derived from BACy1, was sparingly soluble in water, whereas PAA-Cy2, derived from BACy2, was very soluble in aqueous media. The polymerization rates were investigated with 1 H NMR spectroscopy. In both cases, the experimental data were consistent with pseudo-second-order kinetics. The calculated kinetic constants were 5.96 ϫ 10 Ϫ3 and 5.90 ϫ 10 Ϫ2 min Ϫ1 L mol Ϫ1 for the polyaddition of BACy1 and BACy2, respectively. The observed hydrolytic degradation rate of PAA-Cy2 in a pH 7.4 tris(hydroxymethyl)aminomethane (TRIS) buffer was comparable to that of conventional amphoteric PAAs, that is, PAAs containing carboxyl groups in their repeating unit. Degradation experiments carried out in the presence of 2-mercaptoethanol with both PAAs demonstrated that the disulfide groups contained in its repeating units were susceptible to reductive cleavage in the presence of thiols.
BackgroundPoly(amidoamine)s (PAAs) are synthetic polymers endowed with many biologically interesting properties, being highly biocompatible, non toxic and biodegradable. Hydrogels based on PAAs can be easily modified during the synthesis by the introduction of functional co-monomers. Aim of this work is the development and testing of novel amphoteric nanosized poly(amidoamine) hydrogel film incorporating 4-aminobutylguanidine (agmatine) moieties to create RGD-mimicking repeating units for promoting cell adhesion.ResultsA systematic comparative study of the response of an epithelial cell line was performed on hydrogels with agmatine and on non-functionalized amphoteric poly(amidoamine) hydrogels and tissue culture plastic substrates. The cell adhesion on the agmatine containing substrates was comparable to that on plastic substrates and significantly enhanced with respect to the non-functionalized controls. Interestingly, spreading and proliferation on the functionalized supports are slower than on plastic exhibiting the possibility of an easier control of the cell growth kinetics. In order to favor the handling of the samples, a procedure for the production of bi-layered constructs was also developed by means the deposition via spin coating of a thin layer of hydrogel on a pre-treated cover slip.ConclusionThe obtained results reveal that PAAs hydrogels can be profitably functionalized and, in general, undergo physical and chemical modifications to meet specific requirements. In particular the incorporation of agmatine warrants good potential in the field of cell culturing and the development of supported functionalized hydrogels on cover glass are very promising substrates for applications in cell screening devices.
Novel poly(amidoamine)s (PAAs) containing disulfide linkages regularly arranged along the polymer chain, namely BP−CY and BAC−CY, were synthesized by stepwise polyaddition of l-cystine to 1,4-bis(acryloyl)piperazine (BP) and 2,2-bis(acrylamido)acetic acid (BAC), respectively. Even if l-cystine contains four acid hydrogens, no evidence of cross-linking was found. All products were characterized by 1H and 13C NMR spectroscopy, and their average molecular weight determined by size exclusion chromatography. The polymerization rates were investigated by means of 1H NMR spectroscopy. In both cases, the experimental data were consistent with pseudo-second-order kinetics. The calculated kinetic constants were k c,BP = 8.10 × 10-3 min-1 L mol-1 and k c,BAC = 1.41 × 10-3 min-1 L mol-1 for the polyaddition of l-cystine to BP and BAC, respectively. A potentiometric study was carried out of BP−CY and BAC−CY speciation as a function of pH, and the electrochemical activity of their disulfide bonds as a function of pH was investigated by cyclic voltammetry on hanging drop mercury electrode, revealing many analogies with parent l-cystine. BP−CY and BAC−CY degraded in aqueous systems at a rate similar to that usually reported for PAAs. In the presence of reducing agents, however, they degraded completely in a few minutes. Preliminary biocompatibility in vitro tests showed that both BP−CY and BAC−CY are devoid of appreciable toxicity.
Structural colors are the object of a wide scientific interest, not only for the potential technical applications of their intriguing optical properties but also for the need of coloring agents to replace toxic and carcinogenic dyes. We present a simple methodology to obtain polymer opal surfaces of self-assembled core-shell nanoparticles with different degree of order for structural color applications. Polymer nanospheres prepared by surfactant-free emulsion radical copolymerization of an hydrophobic and an hydrophilic comonomer (styrene and methacrylic acid) spontaneously assemble into core-shell particles. Nanoparticles with identical composition and different diameters were prepared by modulating the degree of ionization of the weakly acidic comonomer. We report experimental results revealing how the synthesis parameters affect the properties of the core-shell particles and their influence on the optical properties of the final polymer opal surfaces, which depend on size, charge, and packing arrangement of the constituent nanoparticles.
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