Novel biocompatible and biodegradable amphoteric poly(amidoamine) (PAA) hydrogels were designed for applications as scaffolds for tissue engineering. These hydrogels (PAA-AG1 and PAA-AG2) were obtained by polyaddition of 2,2-bisacrylamidoacetic acid with 2-methylpiperazine and 4-aminobutyl guanidine, a bioactive molecule with a known ability to induce adhesion to cell membranes. They contain carboxylic functions in their main chain and interchain connections deriving from two different cross-linking agents: for PAA-AG1, a multifunctional primary amine, that is, 1,10-decanediamine; for PAA-AG2, a purposely synthesized PAA (PAA-NH(2)) containing pendant NH(2). Both PAA-AG1 and PAA-AG2 proved noncytotoxic and adhesive to cell membranes, as ascertained by means of cytotoxicity and proliferation tests carried out on fibroblast cell lines. Good apparent mechanical strength was also observed in the case of PAA-AG2, cross-linked with the PAA-NH(2). Both PAA-AG1 and PAA-AG2 underwent degradation tests under controlled conditions simulating the biological environments, that is, Dulbecco medium at pH 7.4 and 37 degrees C. They completely dissolved within 10 and about 40 days, respectively. In both cases, the degradation products were completely noncytotoxic. All the results of this paper point to the conclusion that agmatine-based PAA hydrogels are excellent substrates for cell proliferation.

Biodegradable and biocompatible amphoteric poly(amido-amine) (PAA)-based hydrogels, containing carboxyl groups along with amino groups in their repeating unit, were considered as scaffolds for tissue engineering applications. These hydrogels were obtained by co-polymerising 2,2-bisacrylamidoacetic acid with 2-methylpiperazine with or without the addition of different mono-acrylamides as modifiers, and in the presence of primary bis-amines as crosslinking agents. Hybrid PAA/albumin hydrogels were also prepared. The polymerisation reaction was a Michael-type polyaddition carried out in aqueous media. The PAA hydrogels were soft and swellable materials. Cytotoxicity tests were carried out by the direct contact method with fibroblast cell lines on the hydrogels both in their native state (that is, as free bases) and as salts with acids of different strength, namely hydrochloric, sulfuric, acetic and lactic acid. This was done in order to ascertain whether counterion-specific differences in cytotoxicity existed. It was found that all the amphoteric PAA hydrogels considered were cytobiocompatible both as free bases and salts. Selected hydrogels samples underwent degradation tests under controlled conditions simulating biological environments, i.e. Dulbecco medium at pH 7.4 and 37 degrees C. All samples degraded completely and dissolved within 10 d, with the exception of hybrid PAA/albumin hydrogels that did not dissolve even after eight months. The degradation products of all samples turned to be non-cytotoxic. All these results led us to conclude that PAA-based hydrogels have a definite potential as degradable matrices for biomedical applications.

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An amphoteric polyamidoamine (PAA)‐based hydrogel, named INT‐PAA1, with a novel molecular architecture was prepared and studied as a Co2+‐, Ni2+‐, and Cu2+‐sorbing material. This hydrogel was obtained by the synthesis of a PAA in the presence of a second presynthesized PAA carrying many primary amino groups as side substituents, which acted as a macromolecular crosslinking agent. Therefore, it had an intersegmented structure. INT‐PAA1 exhibited a remarkable sorption capacity and sorption rate for Co2+, Ni2+, and Cu2+ that were advantageously in situ monitored by cyclic voltammetry. An extended X‐ray absorption fine structure spectroscopy characterization of the Co2+/INT‐PAA1 complex was also performed. The very fast and quantitative metal‐ion uptake, made apparent by an intense coloring of the hydrogel, showed remarkable potential for environmental applications such as heavy‐metal detection, recovery, and elimination. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2316–2327, 2006