A nuclear localization signal (NLS) is a short amino acid sequence derived from eukaryotic nuclear proteins and viral proteins. Many NLS peptides can efficiently mediate the intranucleus transport of cargo molecules, so they have been widely used for non-viral gene transfer and shown potential ability to improve nuclear delivery of DNA. In order to maximally utilize NLS peptides to enhance gene transfer, several factors such as methods of incorporating NLS peptide, type and property of NLS peptide, number of NLS peptide, and spacer between NLS peptide and DNA should be considered. This review article summarizes how these factors influence the ability of NLS peptides in enhancing non-viral gene delivery and aids in defining the requirements for successful NLS-enhanced transfection.
Spiropyran (SP) shows excellent ability in light‐ or force‐triggered color and fluorescence generation. However, it has the fatal weakness of poor antithermal bleaching properties in polymers, especially when exposed to severe environments, which will shorten the life of mechanical responsive materials. Here, a strategy is reported to protect SP through incorporation of multifunctional polyhedral oligomeric silsesquioxanes (POSS) as cross‐linkers into a polyurethane network. The introduction of POSS not only improves the mechanical strength of the elastomer, but also enhances the thermal stability of the mechanophore, showing much more sensitive force‐responsive and photoresponsive properties, especially after thermal annealing. POSS contributes to the construction of a 3D network and hinders the mobility of the hard domains of molecular chains, thus enhancing the thermal stability of the mechanophore in the network. The strategy can not only extend the life of the stimuli‐responsive materials, but also promote the application temperature of the mechanically responsive polymers.
Poly(amido amine)s' (PAAs) versatility are nearly unique among stepwise polymers. Different functional groups can be easily introduced into these polymers to add functionality such as cell internalization, charge-shift, bioreducibility, "stealth" properties, and targeting moieties, while maintaining the bulk structural integrity of these polymers. The poly(amido amine)s are used as a unique research platform to elucidate their complex structure-function relationship. It is shown that guanidinium group, carboxyl group, disulfide bond, alkyl chain, branching, acetyl groups, benzoyl groups, and quaternary nicotinamide moieties can influence many steps of gene delivery, such as DNA condensation, cellular uptake, endosomal escape, nuclear entry, and finally gene expression. The authors systematically discuss the structure-function correlations of PAAs for gene delivery, and elaborate how the properties of polymers can be adjusted by changing the polymeric structure.
Previously, we synthesized a non-viral vector containing disulfide bond by polymerization of agamatine (AGM) and N,N'-cystaminebisacrylamide (CBA). In this study, we investigated the transfection efficiency of disulfide bond (SS) containing AGM-CBA polymer in gene delivery into NIH/3T3 cells, and examined the factors affecting its transfection efficiency by comparing with polyethylenimine (PEI). In addition, experiments were carried out to determine the mechanisms of cell entry pathways and intracellular behavior of AGM-CBA/pDNA polyplexes. The transfection efficiency of AGM-CBA/pDNA with different weight ratios and different amounts of pDNA was measured and the pathways mediated transfection processes were studied by using various endocytosis inhibitors. To determine the intracellular behavior of AGM-CBA/pDNA polyplexes, the transfection efficiencies of AGM-CBA/pDNA and PEI/pDNA polyplexes with different combination structures were determined by using reporter gene and fake plasmid DNA. The transfection efficiency of AGM-CBA/pDNA polyplexes was correlated with its weight ratio of AGM-CBA and pDNA, and the amount of pDNA. Both AGM-CBA/pDNA and PEI/pDNA polyplexes enter into cell by clathrin- and caveolae-mediated endocytic pathways. However, AGM-CBA/pDNA showed different intracellular behavior in NIH/3T3 cells compared to PEI/pDNA polyplexes. It was hypothesized that disulfide bond in AGM-CBA could be an important factor contributing to its intracellular behavior and better transfection efficiency. Overall, AGM-CBA demonstrated better transfection efficiency and lower cytotoxicity than PEI in NIH/3T3 cells as a gene delivery vector.
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