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).
Highlights
Clay-based composite materials have found numerous applications in recent years, opening new opportunities in materials science and biomedicine [1] Tailoring various biopolymers to clay particlesMolecules 2020, 25, 3557; doi:10.3390/molecules25153557 www.mdpi.com/journal/moleculesMolecules 2020, 25, 3557 allows for controllable self-assembly on planar and three-dimensional surfaces and fabrication of porous clay-doped polymer composites, which can be utilised in tissue engineering [2], artificial cell shellization [3] and hair surface engineering [4]
Our study revealed that halloysite only slightly bound nucleotides x FOR PEER REVIEW
Compared to previous reports, where DNA was combined with halloysite through high speed vibration milling process, the binding of DNA to halloysite in solution in the presence of MgCl2 is a less destructive and more controllable way for obtaining DNA modified halloysite nanotubes
Summary
Clay-based composite materials have found numerous applications in recent years, opening new opportunities in materials science and biomedicine [1] Tailoring various biopolymers to clay particlesMolecules 2020, 25, 3557; doi:10.3390/molecules25153557 www.mdpi.com/journal/moleculesMolecules 2020, 25, 3557 allows for controllable self-assembly on planar and three-dimensional surfaces and fabrication of porous clay-doped polymer composites, which can be utilised in tissue engineering [2], artificial cell shellization [3] and hair surface engineering [4]. Non-viral vectors hold promise as a less dangerous and potentially more effective alternative, and various vectors based on liposomes, polycations, metal nanoparticles, copolymers, etc., have been developed [7]. A transfection vector based on thiolated poly(ethylene glycol)-poly(l-lysine) block copolymer (PEG-PLL) was developed, which responded to the reductive condition mimicking the intracellular environment [8]. All these systems have specific advantages and disadvantages, but one of the main problems is that the efficiency of existing ways for non-viral DNA delivery is still low. The search for new non-toxic and potent non-viral candidates capable of DNA delivery into mammalian cells continues, while clay nanoparticles are considered as candidates for DNA delivery
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