DNA-Encoded Tuning of Geometric and Plasmonic Properties of Nanoparticles Growing from Gold Nanorod Seeds

Growth Reaction of Gold Nanorods in the Presence of Mutated Peptides and Amine-Modified Single-Stranded Nucleic Acids

Conformation of biomolecules like DNA, peptides and amino acids play vital role during nanoparticle growth. Herein, we have experimentally explored the effect of different noncovalent interaction between a 5'-amine modified DNA sequence (NH₂ -C₆ H₁₂ -5'-ACATCAGT-3', PMR) and arginine during the seed-mediated growth reaction of gold nanorods (GNRs). Amino acid-mediated growth reaction of GNRs results in a snowflake-like gold nanoarchitecture. However, in case of Arg, prior incubation of GNRs with PMR selectively produces sea urchin-like gold suprastructures, via strong hydrogen bonding and cation-π interaction between PMR and Arg. This distinctive structure formation strategy has been extended to study the structural modulation caused by two structurally close α-helical RRR (Ac-(AAAAR)₃ A-NH₂ ) peptide and the lysine mutated KKR (Ac-AAAAKAAAAKAAAARA-NH₂ ) peptide with partial helix at the amino terminus. Simulation studies confirm that a greater number of hydrogen bonding and cation-π interaction between the Arg residues and PMR resulted in the gold sea urchin structure for RRR peptide against KKR peptide.

Identifying and Differentiating Topological G-Quadruplex Structures with DNA-Encoded Plasmonic Gold Nanoparticles

DNA G-quadruplexes (G4s) have been identified as critical elements in modulating genomic functions and many other biological processes. Their functions are highly dependent on the primary nucleotides and secondary folding structures. Therefore, to understand their functions, methods to identify and differentiate structures of G4 with speed and accuracy are required but limited. In this report, we have applied a synthetic G4 DNA-encoded nanoparticle approach to identify and differentiate G4 DNA molecules with different topologies and nucleotide residues. We found that the resulting plasmonic properties of the gold nanoparticles, monitored by UV/Vis spectroscopy, are quite sensitive to different G4 structures, including stacking layers, loop sequences, capping bases on G4s, and topological structures. Through these systematic investigations, we demonstrate that this G4-encoded gold nanoparticle approach can be used to profile the G4 structures and distinguish G4s from human telomeres. Such a method may have wide applications in G4 research.

Nanogold Flower-Inspired Nanoarchitectonics Enables Enhanced Light-to-Heat Conversion Ability for Rapid and Targeted Chemo-Photothermal Therapy of a Tumor

Chemo-photothermal therapy has become a promising tool for clinical noninvasive tumor therapy, which is able to efficiently avoid drug resistance and other side effects from chemical anticarcinogenic drugs. The ability to selectively fast-heat tumor tissues over surrounding compartments is of fundamental importance and makes effective treatment of tumor margins and complex tumor geometries. Currently existing chemo-photothermal methods mainly show slow light-to-heat conversion with increased temperature up to around 45-57 °C for 5-20 min or a longer time in vitro under regular near-infrared laser irradiation, and during tumor therapy, worse performance in temperature changes are obtained due to the much longer penetration distance in vivo. Herein, nanoarchitectonics with excellent chemo-photothermal performance are first proposed for tumors via in situ decoration of nanogold flowers on graphene oxide surface with further modification of the aptamer molecule. Even with simple synthesis processes, these nanoarchitectonics demonstrate impressive increased temperatures up to 85 °C in just 2 min under 808 nm laser irradiation with regular power density. Due to the fast light-to-heat conversion ability and specific binding effect between the aptamer and tumor cells, the designed nanocarrier shows a rapid and target therapy system with a targeted chemo-photothermal tumor treatment.

Selection and Screening of DNA Aptamers for Inorganic Nanomaterials

Searching for DNA sequences that can strongly and selectively bind to inorganic surfaces is a long-standing topic in bionanotechnology, analytical chemistry and biointerface research. This can be achieved either by aptamer selection starting with a very large library of ≈10¹⁴ random DNA sequences, or by careful screening of a much smaller library (usually from a few to a few hundred) with rationally designed sequences. Unlike typical molecular targets, inorganic surfaces often have quite strong DNA adsorption affinities due to polyvalent binding and even chemical interactions. This leads to a very high background binding making aptamer selection difficult. Screening, on the other hand, can be designed to compare relative binding affinities of different DNA sequences and could be more appropriate for inorganic surfaces. The resulting sequences have been used for DNA-directed assembly, sorting of carbon nanotubes, and DNA-controlled growth of inorganic nanomaterials. It was recently discovered that poly-cytosine (C) DNA can strongly bind to a diverse range of nanomaterials including nanocarbons (graphene oxide and carbon nanotubes), various metal oxides and transition-metal dichalcogenides. In this Concept article, we articulate the need for screening and potential artifacts associated with traditional aptamer selection methods for inorganic surfaces. Representative examples of application are discussed, and a few future research opportunities are proposed towards the end of this article.

Systematic study of interdependent relationship on gold nanorod synthesis assisted by electron microscopy image analysis

Here, we systematically investigated the independent, multiple, and synergic effects of three major components, namely, ascorbic acid (AA), seed, and silver ions (Ag⁺), on the characteristics of gold nanorods (GNRs), i.e., longitudinal localized surface plasmon resonance (LSPR) peak position, shape, size, and monodispersity. To quantitatively assess the shape and dimensions of GNRs, we used an automated transmission electron microscopy image analysis method using a MATLAB-based code developed in-house and the concept of solidity, which is the ratio between the area of a GNR and the area of its convex hull. The solidity of a straight GNR is close to 1, while it decreases for both dumbbell- and dogbone-shaped GNRs. We found that the LSPR peak position, shape, and monodispersity of the GNRs all altered simultaneously with changes in the amounts of individual components. For example, as the amount of AA increased, both the LSPR peak and solidity decreased, while the polydispersity increased. In contrast, as the amount of seeds increased, both the LSPR and solidity increased, while the monodispersity improved. More importantly, we found that the influence of each component can actually change depending on the composition of the GNR growth solution. For instance, the LSPR peak position red-shifted as the amount of AA increased when the seed content was low, whereas it blue-shifted when the seed content was high.