Facile Fabrication of Natural Polyelectrolyte-Nanoclay Composites: Halloysite Nanotubes, Nucleotides and DNA Study

Abstract

Complexation of biopolymers with halloysite nanotubes (HNTs) can greatly affect their applicability as materials building blocks. Here we have performed a systematic investigation of fabrication of halloysite nanotubes complexes with nucleotides and genomic DNA. The binding of DNA and various nucleotide species (polyAU, UMP Na2, ADP Na3, dATP Na, AMP, uridine, ATP Mg) by halloysite nanotubes was tested using UV-spectroscopy. The study revealed that binding of different nucleotides to the nanoclay varied but was low both in the presence and absence of MgCl2, while MgCl2 facilitated significantly the binding of longer molecules such as DNA and polyAU. Modification of the nanotubes with DNA and nucleotide species was further confirmed by measurements of ζ-potentials. DNA-Mg-modified nanotubes were characterized using transmission electron (TEM), atomic force (AFM) and hyperspectral microscopies. Thermogravimetric analysis corroborated the sorption of DNA by the nanotubes, and the presence of DNA on the nanotube surface was indicated by changes in the surface adhesion force measured by AFM. DNA bound by halloysite in the presence of MgCl2 could be partially released after addition of phosphate buffered saline. DNA binding and release from halloysite nanotubes was tested in the range of MgCl2 concentrations (10–100 mM). Even low MgCl2 concentrations significantly increased DNA sorption to halloysite, and the binding was leveled off at about 60 mM. DNA-Mg-modified halloysite nanotubes were used for obtaining a regular pattern on a glass surface by evaporation induced self-assembly process. The obtained spiral-like pattern was highly stable and resisted dissolution after water addition. Our results encompassing modification of non-toxic clay nanotubes with a natural polyanion DNA will find applications for construction of gene delivery vehicles and for halloysite self-assembly on various surfaces (such as skin or hair).

Infrared Nanospectroscopy Reveals DNA Structural Modifications upon Immobilization onto Clay Nanotubes

“…Thus, according to our results, DNA adsorption on HNs involves charges located in the minor groove of DNA that interact with the surface of the nanotube through electrostatic interactions. In light of a recent experiment obtained on DNA oligomers [ 20 ] and the possible chemical specificity of the DNA–HNs absorbtion we observe with the nano-FTIR technique on lateral chains (i.e., Adenine and Thymine), our results open the way for future experiments to assess the role played by specific DNA sequences in the interaction with HNs. Our research also suggests a partial covering of nanotubes by DNA molecules, and this evidence was enlightened with the unique power of nanoresolved FTIR spectroscopy, which allows us to simultaneously probe morphological nanoscale features and chemical bond vibrations.…”

“…Although EM can probe the spatial distribution of immobilized molecules on nanoclay surfaces, the very complicated data analysis and sample damaging due to the e-beam exposure make the techniques not optimal for the study of these systems [ 19 ]. Interestingly, non-destructive high-resolution atomic force microscopy coupled to force spectroscopy investigation has proven useful for revealing DNA molecules adsorbed onto nanotubes [ 20 ] and paved the way for taking advantage of combined AFM with nanoscale-resolved spectroscopic mode. The coupling of spectroscopies and microscopies represents the best approach to studying HNs nanocarriers, allowing one to probe the system from two distinct points of view: chemico-physical and morphological.…”

Comparative Toxicity of Fly Ash: An In Vitro Study

“…Then, hyperspectral images of the Jurkat and HeLa cell lines treated with coal fly ash particles were obtained for determining the distribution of particles at different time points. The internal spectral mapping algorithm was used to confirm spectral coincidence between image pixels in hyperspectral datacube of cells and spectral libraries of pure particles [ 63 , 64 , 65 , 66 ]. The spectral angle coefficient for HeLa cells treated with particles for 1 h was 0.6 (Rockdale, Dolet Hills), 0.5 (Rockport), and 0.2 (Muskogee, Chelyabinsk) rad.…”

DNA interfaces with dimensional materials for biomedical applications

“…56 The p-p interaction between the two materials can improve in presence of Mg 2+ ions by reducing repulsion between negatively charged HNTs and the DNA phosphate backbone. 71 However, there were also reports of polymer mediated interactions (e.g. polyethyleneimine or PEI, g-aminopropyltriethoxysilane or APTES) 68,72,73 for gene delivery with a non-viral gene vector.…”