Abstract
Poly(amidoamine) dendrimers are the most recognized class of dendrimer. Amino-terminated (PAMAM-NH2) and hydroxyl-terminated (PAMAM-OH) dendrimers of generation 4 are widely used, since they are commercially available. Both have different properties, mainly based on their different overall charges at physiological pH. Currently, an important function of dendrimers as carriers of short single-stranded DNA has been applied. These molecules, known as antisense oligonucleotides (asODNs), are able to inhibit the expression of a target mRNA. Whereas PAMAM-NH2 dendrimers have shown to be able to transfect plasmid DNA, PAMAM-OH dendrimers have not shown the same successful results. However, little is known about their interaction with shorter and more flexible molecules such as asODNs. Due to several initiatives, the use of these neutral dendrimers as a scaffold to introduce other functional groups has been proposed. Because of its low cytotoxicity, it is relevant to understand the molecular phenomena involving these types of dendrimers. In this work, we studied the behavior of an antisense oligonucleotide in presence of both types of dendrimers using molecular dynamics simulations, in order to elucidate if they are able to form stable complexes. In this manner, we demonstrated at atomic level that PAMAM-NH2, unlike PAMAM-OH, could form a well-compacted complex with asODN, albeit PAMAM-OH can also establish stable interactions with the oligonucleotide. The biological activity of asODN in complex with PAMAM-NH2 dendrimer was also shown. Finally, we revealed that in contact with PAMAM-OH, asODN remains outside the cells as TIRF microscopy results showed, due to its poor interaction with this dendrimer and cell membranes.
Highlights
Dendrimers, a class of hyperbranched polymer explored in nanomedicine applications, were first described by Tomalia [1] and Newkome [2]—separately—as core-shell structures, built in a layer-by-layer way, forming generations
In order to elucidate the molecular phenomena associated with complexation of amine-terminated and hydroxyl-terminated dendrimers and asODN, at atomiclevel scale, and to determine effectively if PAMAM-OH is unable to interact with asODNs, we studied the behavior of an asODN that inhibits Survivin messenger RNA (mRNA) expression [20], in presence of both types of dendrimers, using molecular dynamics simulations
Molecular dynamics simulations studies have been performed in order to understand how different functional groups of a dendrimer, with different surface charge, could affect the complexation with antisense oligonucleotides
Summary
Dendrimers, a class of hyperbranched polymer explored in nanomedicine applications, were first described by Tomalia [1] and Newkome [2]—separately—as core-shell structures, built in a layer-by-layer way, forming generations. Dendrimers have promoted high interest in the field of biology and nanomedicine due to their multivalent and monodisperse properties, which favor reproducible In this sense, PAMAM-NH2 dendrimer have been described first by Haensler and Szoka [6] and by Kukowska-Latallo et al [7] as efficient carriers for nucleic acids, due to their positive charge at physiological pH [8]. PAMAM dendrimers have been described as carriers of antisense oligonucleotides (asODN) [13,14,15,16,17] These molecules consist in a short single-stranded DNA, 8–50 nucleotides length, which targets a specific receptor messenger RNA (mRNA) preferentially through Watson– Crick base pairing, inhibiting its transcription [18]. Carrasco et al [20] and more recently Vidaurre et al [21], have identified antisense oligonucleotides that downregulate the expression of RNA involved in cancer proliferation
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