Three poly(amidoamine)s with pendant primary amines were synthesized by Michael polyaddition of a diamine to N,N‐methylenebis(acrylamide). The poly(amidoamine)s with primary and tertiary amines possess a high buffer capacity between pH = 5 and 7, which facilitates the escape of polymer/DNA complexes from endosomes according to the ‘proton sponge hypothesis’. In vitro cytotoxicity of poly(amidoamine)s depends on the side‐chain structure of the polymer. Polymers 1a – 1c can condense plasmid DNA by electrostatic interactions to form nanosized polyelectrolyte complexes with a positive surface charge. In vitro transfection results indicate that the transfection efficiency of polymer 1b under optimized conditions is comparable to that of commercial branched PEI 25 000.
This paper reports on the synthesis and physico‐chemical, mechanical, and biological characterization of two sets of poly(amidoamine) (PAA) hydrogels with potential as scaffolds for in vivo peripheral nerve regeneration. They are obtained by polyaddition of piperazine with N,N′‐methylenebis(acrylamide) or 1,4‐bis(acryloyl)piperazine with 1,2‐diaminoethane as cross‐linking agent and exhibit a combination of relevant properties, such as mechanical strength, biocompatibility, biodegradability, ability to induce adhesion and proliferation of Schwann cells (SCs) preserving their viability. Moreover, the most promising hydrogels, that is those deriving from 1,4‐bis(acryloyl)piperazine, allow the in vitro growth of the sensitive neurons of the dorsal root ganglia, thus getting around a critical point in the design of conduits for nerve regeneration.
The applicability of CMCht/PAMAM dendrimer nanoparticles for CNS applications was investigated. AFM and TEM observations revealed that the nanoparticles possessed a nanosphere‐like shape with a size from 22.0 to 30.7 nm. The nanoparticles could be bound to fluorescent‐probe FITC for tracing purposes. Post‐natal hippocampal neurons and cortical glial cells were both able to internalize the FITC‐labeled CMCht/PAMAM dendrimer nanoparticles with high efficiency. The percentage of positive cells internalizing the nanoparticles varied, reaching a peak after 48 h of incubation. Further experiments for periods up to 7 d revealed that the periodical addition of FITC‐labelled CMCht/PAMAM dendrimer nanoparticles was needed to maintain the overall percentage of cells internalizing them. Finally, it was also observed that cell viability was not significantly affected by the incubation of dendrimer nanoparticles.
The preparation of a novel peptide/dendrimer hybrid is reported in which an elastin‐like oligopeptide is successfully assembled onto a poly(amidoamine) dendrimer surface (G4‐ELP), and its unique thermo‐responsive behavior is discussed. As a result, the G4‐ELP is found to exhibit LCST behavior in the pH range 3–10 including physiological temperature range under neutral‐pH conditions. Moreover, cooperative interplay between the folding state of the ELP shell and the ionization state of the dendrimer core enables the G4‐ELP to control its LCST widely by pH variation. This achievement provides a new insight for the design of dual‐responsive materials with a potential in biological applications.
Stereo multiblock PLAs with different block lengths are synthesized by melt polycondensation of low‐molecular‐weight poly(L ‐lactic acid)/poly(D ‐lactic acid) blends with a wide variety of $\overline {M} _{{\rm w}} $ in the range of 1.1–5.2 × 103 g · mol–1. The average block length (νav) of the stereo multiblock PLAs increases with increasing $\overline {M} _{{\rm w}} $ of the blend and with the reaction temperature, whereas $\overline {M} _{{\rm w}} $ and PDI of the stereo multiblock PLAs increases with increasing $\overline {M} _{{\rm w}} $ of the blend, the reaction time, and the temperature. Stereo multiblock PLAs with νav > 7 are crystallizable to form stereocomplex crystallites, and the crystallinity and melting temperature of the stereo multiblock PLAs increases with increasing νav and $\overline {M} _{{\rm w}} $ of the stereo multiblock PLAs.
