Abstract
We describe the formation and structure of nucleolipid/dendrimer multilayer films controlled by non-covalent interactions to obtain biomaterials that exhibit molecular recognition of nucleic acids. Layers of cationic poly(amidoamine) (PAMAM) dendrimers of generation 4 and the anionic nucleolipids 1,2-dilauroyl-sn-glycero-3-phosphatidylnucleosides (DLPNs) based on uridine (DLPU) and adenosine (DLPA) were first formed at the silica-water interface. The PAMAM/DLPN layers were then exposed to short oligonucleotides, polynucleotides and single stranded DNA (ssDNA). The interfacial properties were characterized using quartz crystal microbalance with dissipation monitoring, attenuated total reflection Fourier transform infrared spectroscopy and neutron reflectometry. Both types of DLPN were found to adsorb as aggregates to preadsorbed PAMAM monolayers with a similar interfacial structure and composition before rinsing with pure aqueous solution. Nucleic acids were found to interact with PAMAM/DLPA layers due to base pairing interactions, while the PAMAM/DLPU layers did not have the same capability. This was attributed to the structure of the DLPA layer, which is formed by aggregates that extend from the interface towards the bulk after rinsing with pure solvent, while the DLPU layer forms compact structures. In complementary experiments using a different protocol, premixed PAMAM/DLPN samples adsorbed to hydrophilic silica only when the mixtures contained positively charged aggregates, which is rationalized in terms of electrostatic forces. The PAMAM/DLPA layers formed from the adsorption of these mixtures also bind ssDNA although in this case the adsorption is mediated by the opposite charges of the film and the nucleic acid rather than specific base pairing. The observed molecular recognition of nucleic acids by dendrimers functionalized via non-covalent interactions with nucleolipids is discussed in terms of biomedical applications such as gene vectors and biosensors.
Highlights
Poly(amidoamine) (PAMAM) dendrimers have, with their wellde ned hyperbranched architecture, high potential to be employed in biomedical applications such as the encapsulation aPhysical Chemistry, Department of Chemistry, Lund University, P
This was attributed to the structure of the DLPA layer, which is formed by aggregates that extend from the interface towards the bulk after rinsing with pure solvent, while the DLPU layer forms compact structures
We explored the ability of layers formed by the interactions between DLPA and preadsorbed PAMAM monolayers to exhibit molecular recognition of DNA.[44]
Summary
Poly(amidoamine) (PAMAM) dendrimers have, with their wellde ned hyperbranched architecture, high potential to be employed in biomedical applications such as the encapsulation aPhysical Chemistry, Department of Chemistry, Lund University, P. 1, 85747 Garching, Germany fJulich Centre for Neutron Science, Outstation at MLZ, Lichtenbergstr. The chemical structure of PAMAM dendrimers, as reported in 1985 by Tomalia et al.,[5] is based on an ethylenediamine or amine core and repeating units of amidoamine as branches with amine surface groups. The formed PAMAM/DNA complexes protect DNA from enzymatic degradation and they show high transfection to cells compared to other polymeric alternatives.[2] Such delivery vehicles for gene therapy have been shown to have potential for disease prevention[7] and medical treatments.[8,9] ordinary PAMAM dendrimers lack chemical affinity
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