1
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Rolband L, Godakhindi V, Vivero-Escoto JL, Afonin KA. Demonstrating the Synthesis and Antibacterial Properties of Nanostructured Silver. JOURNAL OF CHEMICAL EDUCATION 2023; 100:3547-3555. [PMID: 37720521 PMCID: PMC10501122 DOI: 10.1021/acs.jchemed.3c00125] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 07/29/2023] [Indexed: 09/19/2023]
Abstract
Investigating and understanding novel antibacterial agents is a necessary task as there is a constant increase in the number of multidrug-resistant bacterial species. The use of nanotechnology to combat drug-resistant bacteria is an important research area. The laboratory experiment described herein demonstrates that changes in the nanostructure of a material lead to significantly different antibacterial efficacies. Silver has been known to be an effective antibacterial agent throughout history, but its therapeutic uses are limited when present as either the bulk material or cations in solution. Silver nanoparticles (AgNPs) and DNA-templated silver nanoclusters (DNA-AgNCs) are both nanostructured silver materials that show vastly different antibacterial activities when incubated with E. coli in liquid culture. This work aims to provide students with hands-on experience in the synthesis and characterization of nanomaterials and basic microbiology skills; moreover, it is applicable to undergraduate and graduate curricula.
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Affiliation(s)
- Lewis Rolband
- Department
of Chemistry, University of North Carolina
at Charlotte, Charlotte, North Carolina 28223, United States
| | - Varsha Godakhindi
- Department
of Chemistry, University of North Carolina
at Charlotte, Charlotte, North Carolina 28223, United States
| | - Juan L. Vivero-Escoto
- Department
of Chemistry, University of North Carolina
at Charlotte, Charlotte, North Carolina 28223, United States
| | - Kirill A. Afonin
- Department
of Chemistry, University of North Carolina
at Charlotte, Charlotte, North Carolina 28223, United States
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2
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Mastracco P, Copp SM. Beyond nature's base pairs: machine learning-enabled design of DNA-stabilized silver nanoclusters. Chem Commun (Camb) 2023; 59:10360-10375. [PMID: 37575075 DOI: 10.1039/d3cc02890a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Sequence-encoded biomolecules such as DNA and peptides are powerful programmable building blocks for nanomaterials. This paradigm is enabled by decades of prior research into how nucleic acid and amino acid sequences dictate biomolecular interactions. The properties of biomolecular materials can be significantly expanded with non-natural interactions, including metal ion coordination of nucleic acids and amino acids. However, these approaches present design challenges because it is often not well-understood how biomolecular sequence dictates such non-natural interactions. This Feature Article presents a case study in overcoming challenges in biomolecular materials with emerging approaches in data mining and machine learning for chemical design. We review progress in this area for a specific class of DNA-templated metal nanomaterials with complex sequence-to-property relationships: DNA-stabilized silver nanoclusters (AgN-DNAs) with bright, sequence-tuned fluorescence colors and promise for biophotonics applications. A brief overview of machine learning concepts is presented, and high-throughput experimental synthesis and characterization of AgN-DNAs are discussed. Then, recent progress in machine learning-guided design of DNA sequences that select for specific AgN-DNA fluorescence properties is reviewed. We conclude with emerging opportunities in machine learning-guided design and discovery of AgN-DNAs and other sequence-encoded biomolecular nanomaterials.
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Affiliation(s)
- Peter Mastracco
- Department of Materials Science and Engineering, University of California, Irvine, California 92697, USA.
| | - Stacy M Copp
- Department of Materials Science and Engineering, University of California, Irvine, California 92697, USA.
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
- Department of Chemical and Biomolecular Engineering, University of California, Irvine, California 92697, USA
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3
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Fredrick D, Yourston L, Krasnoslobodtsev AV. Detection of cancer-associated miRNA using a fluorescence switch of AgNC@NA and guanine-rich overhang sequences. LUMINESCENCE 2023; 38:1385-1392. [PMID: 36843363 DOI: 10.1002/bio.4471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 02/03/2023] [Accepted: 02/18/2023] [Indexed: 02/28/2023]
Abstract
DNA-templated silver nanoclusters (AgNC@DNA) are a novel type of nanomaterial with advantageous optical properties. Only a few atoms in size, the fluorescence of nanoclusters can be tuned using DNA overhangs. In this study, we explored the properties of AgNCs manufactured on a short single-stranded (dC)12 when adjacent G-rich sequences (dGN , with N = 3-15) were added. The 'red' emission of AgNC@dC12 with λMAX = 660 nm dramatically changed upon the addition of a G-rich overhang with NG = 15. The pattern of the emission-excitation matrix (EEM) suggested the emergence of two new emissive states at λMAX = 575 nm and λMAX = 710 nm. The appearance of these peaks provides an effective way to design biosensors capable of detecting specific nucleic acid sequences with low fluorescence backgrounds. We used this property to construct an NA-based switch that brings AgNC and the G overhang near one another, turning 'ON' the new fluorescence peaks only when a specific miRNA sequence is present. Next, we tested this detection switch on miR-371, which is overexpressed in prostate cancer. The results presented provide evidence that this novel fluorescent switch is both sensitive and specific with a limit of detection close to 22 picomoles of the target miR-371 molecule.
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Affiliation(s)
- Dylan Fredrick
- Department of Physics, University of Nebraska Omaha, 6001 Dodge Street, Omaha, Nebraska, USA
| | - Liam Yourston
- Department of Physics, University of Nebraska Omaha, 6001 Dodge Street, Omaha, Nebraska, USA
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4
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Gupta AK, Marshall N, Yourston L, Rolband L, Beasock D, Danai L, Skelly E, Afonin KA, Krasnoslobodtsev AV. Optical, structural, and biological properties of silver nanoclusters formed within the loop of a C-12 hairpin sequence. NANOSCALE ADVANCES 2023; 5:3500-3511. [PMID: 37383066 PMCID: PMC10295035 DOI: 10.1039/d3na00092c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Accepted: 06/04/2023] [Indexed: 06/30/2023]
Abstract
Silver nanoclusters (AgNCs) are the next-generation nanomaterials representing supra-atomic structures where silver atoms are organized in a particular geometry. DNA can effectively template and stabilize these novel fluorescent AgNCs. Only a few atoms in size - the properties of nanoclusters can be tuned using only single nucleobase replacement of C-rich templating DNA sequences. A high degree of control over the structure of AgNC could greatly contribute to the ability to fine-tune the properties of silver nanoclusters. In this study, we explore the properties of AgNCs formed on a short DNA sequence with a C12 hairpin loop structure (AgNC@hpC12). We identify three types of cytosines based on their involvement in the stabilization of AgNCs. Computational and experimental results suggest an elongated cluster shape with 10 silver atoms. We found that the properties of the AgNCs depend on the overall structure and relative position of the silver atoms. The emission pattern of the AgNCs depends strongly on the charge distribution, while all silver atoms and some DNA bases are involved in optical transitions based on molecular orbital (MO) visualization. We also characterize the antibacterial properties of silver nanoclusters and propose a possible mechanism of action based on the interactions of AgNCs with molecular oxygen.
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Affiliation(s)
- Akhilesh Kumar Gupta
- Department of Physics, University of Nebraska at Omaha Omaha NE 68182 USA +1402-554-3723
| | - Nolan Marshall
- Department of Physics, University of Nebraska at Omaha Omaha NE 68182 USA +1402-554-3723
| | - Liam Yourston
- Department of Physics, University of Nebraska at Omaha Omaha NE 68182 USA +1402-554-3723
| | - Lewis Rolband
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte Charlotte NC 28223 USA
| | - Damian Beasock
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte Charlotte NC 28223 USA
| | - Leyla Danai
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte Charlotte NC 28223 USA
| | - Elizabeth Skelly
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte Charlotte NC 28223 USA
| | - Kirill A Afonin
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte Charlotte NC 28223 USA
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5
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Hartung J, McCann N, Doe E, Hayth H, Benkato K, Johnson MB, Viard M, Afonin KA, Khisamutdinov EF. Toehold-Mediated Shape Transition of Nucleic Acid Nanoparticles. ACS APPLIED MATERIALS & INTERFACES 2023; 15:25300-25312. [PMID: 37204867 PMCID: PMC10331730 DOI: 10.1021/acsami.3c01604] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We introduce a toehold-mediated strand displacement strategy for regulated shape-switching of nucleic acid nanoparticles (NANPs) enabling their sequential transformation from triangular to hexagonal architectures at isothermal conditions. The successful shape transitions were confirmed by electrophoretic mobility shift assays, atomic force microscopy, and dynamic light scattering. Furthermore, implementation of split fluorogenic aptamers allowed for monitoring the individual transitions in real time. Three distinct RNA aptamers─malachite green (MG), broccoli, and mango─were embedded within NANPs as reporter domains to confirm shape transitions. While MG "lights up" within the square, pentagonal, and hexagonal constructs, the broccoli is activated only upon formation of pentagon and hexagon NANPs, and mango reports only the presence of hexagons. Moreover, the designed RNA fluorogenic platform can be employed to construct a logic gate that performs an AND operation with three single-stranded RNA inputs by implementing a non-sequential polygon transformation approach. Importantly, the polygonal scaffolds displayed promising potential as drug delivery agents and biosensors. All polygons exhibited effective cellular internalization followed by specific gene silencing when decorated with fluorophores and RNAi inducers. This work offers a new perspective for the design of toehold-mediated shape-switching nanodevices to activate different light-up aptamers for the development of biosensors, logic gates, and therapeutic devices in the nucleic acid nanotechnology.
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Affiliation(s)
- Jordan Hartung
- Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States
| | - Nathan McCann
- Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States
| | - Erwin Doe
- Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States
| | - Hannah Hayth
- Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States
| | - Kheiria Benkato
- Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States
| | - M Brittany Johnson
- Department of Biology, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
| | - Mathias Viard
- Laboratory of Integrative Cancer Immunology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, United States
- Basic Science Program, Leidos Biomedical Research Inc. National Cancer Institute, National Institutes of Health, Frederick, Maryland 21702, United States
| | - Kirill A Afonin
- Department of Chemistry, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
| | - Emil F Khisamutdinov
- Department of Chemistry, Ball State University, Muncie, Indiana 47306, United States
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6
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Bouanane I, Bedu F, Ozerov I, Sciacca B, Santinacci L, Duché D, Berginc G, Escoubas L, Margeat O, Le Rouzo J. Design of infrared optical absorber using silver nanorings array made by a top-down process. Sci Rep 2023; 13:7770. [PMID: 37173376 PMCID: PMC10182000 DOI: 10.1038/s41598-023-34579-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 05/02/2023] [Indexed: 05/15/2023] Open
Abstract
This paper presents the numerical simulation and fabrication of a metasurface composed of silver nanorings with a split-ring gap. These nanostructures can exhibit optically-induced magnetic responses with unique possibilities to control absorption at optical frequencies. The absorption coefficient of the silver nanoring was optimized by performing a parametric study with Finite Difference Time Domain (FDTD) simulations. The absorption and scattering cross sections of the nanostructures are numerically calculated to assess the impact of the inner and outer radii, the thickness and the split-ring gap of one nanoring, as well as the periodicity factor for a group of four nanorings. This showed full control on resonance peaks and absorption enhancement in the near infrared spectral range. The experimental fabrication of this metasurface made of an array of silver nanorings is achieved by e-beam lithography and metallization. Optical characterizations are then carried out and compared to the numerical simulations. In contrast to usual microwave split-ring resonator metasurfaces reported in literature, the present study shows both the realization by a top-down process and modelling performed in the infrared frequency range.
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Affiliation(s)
- I Bouanane
- Aix Marseille University, Université de Toulon, CNRS, IM2NP, Marseille, France.
- Thales LAS France SAS, Élancourt, France.
| | - F Bedu
- Aix Marseille University, CNRS, CINAM, AMUTECH, Marseille, France
| | - I Ozerov
- Aix Marseille University, CNRS, CINAM, AMUTECH, Marseille, France
| | - B Sciacca
- Aix Marseille University, CNRS, CINAM, AMUTECH, Marseille, France
| | - L Santinacci
- Aix Marseille University, CNRS, CINAM, AMUTECH, Marseille, France
| | - D Duché
- Aix Marseille University, Université de Toulon, CNRS, IM2NP, Marseille, France
| | - G Berginc
- Thales LAS France SAS, Élancourt, France
| | - L Escoubas
- Aix Marseille University, Université de Toulon, CNRS, IM2NP, Marseille, France
| | - O Margeat
- Aix Marseille University, CNRS, CINAM, AMUTECH, Marseille, France
| | - J Le Rouzo
- Aix Marseille University, Université de Toulon, CNRS, IM2NP, Marseille, France
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7
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Kar P, Wang CM, Liao CL, Chang TS, Liao WS. Guiding Metal Organic Framework Morphology via Monolayer Artificial Defect-Induced Preferential Facet Selection. JACS AU 2023; 3:1118-1130. [PMID: 37124286 PMCID: PMC10131197 DOI: 10.1021/jacsau.2c00692] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 02/24/2023] [Accepted: 02/24/2023] [Indexed: 05/03/2023]
Abstract
Guiding metal organic framework (MOF) morphology, especially without the need for chemical additives, still remains a challenge. For the first time, we report a unique surface guiding approach in controlling the crystal morphology formation of zeolitic imidazole framework-8 (ZIF-8) and HKUST-1 MOFs on disrupted alkanethiol self-assembled monolayer (SAM)-covered Au substrates. Selective molecule removal is applied to generate diverse SAM matrices rich in artificial molecular defects in a monolayer to direct the dynamic crystal growth process. When a 11-mercaptoundecanol alkanethiol monolayer is ruptured, the hydroxyl tail groups of surface residue molecules act as nucleating sites by coordination with precursor metal ions. Meanwhile, the exposed alkane chain backbones stabilize a particular facet of MOF nuclei in the dynamic growth by slowing down their crystal growth rates along a specific direction. The competitive formation between the [110] and [100] planes of ZIF-8 ultimately regulates the crystal shapes from rhombic dodecahedron, truncated rhombic dodecahedron, and truncated cube to cube. Similarly, changeable morphologies of HKUST-1 crystals are also achieved from cube and tetrakaidekahedron to octahedron, originating from the competitive selection between the [100] and [111] planes. In addition to the artificial matrix preferred orientation of initial nucleation, parameters such as temperature also play a crucial role in the resulting crystal morphology. Standing on the additive-free MOF crystal morphology growth control, porous architectures prepared in this approach can act as templates for ligand-free metal (Au, Ag, and Cu) nanocluster synthesis. The nanocluster-embedded MOF structures represent distinct crystal morphology-dependent optical properties, and interestingly, their fluorescence emission can be highly enhanced by facet-induced nanocluster packing alignments. These findings not only provide a unique thought on MOF crystal morphology guidance but also pave a new route for the accompanied property investigation and further application.
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8
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Gupta AK, Krasnoslobodtsev AV. DNA-Templated Silver Nanoclusters as Dual-Mode Sensitive Probes for Self-Powered Biosensor Fueled by Glucose. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1299. [PMID: 37110883 PMCID: PMC10145323 DOI: 10.3390/nano13081299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Revised: 04/04/2023] [Accepted: 04/05/2023] [Indexed: 06/19/2023]
Abstract
Nanomaterials have been extensively explored in developing sensors due to their unique properties, contributing to the development of reliable sensor designs with improved sensitivity and specificity. Herein, we propose the construction of a fluorescent/electrochemical dual-mode self-powered biosensor for advanced biosensing using DNA-templated silver nanoclusters (AgNCs@DNA). AgNC@DNA, due to its small size, exhibits advantageous characteristics as an optical probe. We investigated the sensing efficacy of AgNCs@DNA as a fluorescent probe for glucose detection. Fluorescence emitted by AgNCs@DNA served as the readout signal as a response to more H2O2 being generated by glucose oxidase for increasing glucose levels. The second readout signal of this dual-mode biosensor was utilized via the electrochemical route, where AgNCs served as charge mediators between the glucose oxidase (GOx) enzyme and carbon working electrode during the oxidation process of glucose catalyzed by GOx. The developed biosensor features low-level limits of detection (LODs), ~23 μM for optical and ~29 μM for electrochemical readout, which are much lower than the typical glucose concentrations found in body fluids, including blood, urine, tears, and sweat. The low LODs, simultaneous utilization of different readout strategies, and self-powered design demonstrated in this study open new prospects for developing next-generation biosensor devices.
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9
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Danai L, Rolband LA, Perdomo VA, Skelly E, Kim T, Afonin KA. Optical, structural and antibacterial properties of silver nanoparticles and DNA-templated silver nanoclusters. Nanomedicine (Lond) 2023; 18:769-782. [PMID: 37345552 PMCID: PMC10308257 DOI: 10.2217/nnm-2023-0082] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 06/06/2023] [Indexed: 06/23/2023] Open
Abstract
Silver nanoparticles (AgNPs) are increasingly considered for biomedical applications as drug-delivery carriers, imaging probes and antibacterial agents. Silver nanoclusters (AgNCs) represent another subclass of nanoscale silver. AgNCs are a promising tool for nanomedicine due to their small size, structural homogeneity, antibacterial activity and fluorescence, which arises from their molecule-like electron configurations. The template-assisted synthesis of AgNCs relies on organic molecules that act as polydentate ligands. In particular, single-stranded nucleic acids reproducibly scaffold AgNCs to provide fluorescent, biocompatible materials that are incorporable in other formulations. This mini review outlines the design and characterization of AgNPs and DNA-templated AgNCs, discusses factors that affect their physicochemical and biological properties, and highlights applications of these materials as antibacterial agents and biosensors.
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Affiliation(s)
- Leyla Danai
- Department of Chemistry, Nanoscale Science Program, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Lewis A Rolband
- Department of Chemistry, Nanoscale Science Program, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | | | - Elizabeth Skelly
- Department of Chemistry, Nanoscale Science Program, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Taejin Kim
- Physical Sciences Department, West Virginia University Institute of Technology, Beckley, WV 25801, USA
| | - Kirill A Afonin
- Department of Chemistry, Nanoscale Science Program, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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10
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Skelly E, Rolband LA, Beasock D, Afonin KA. Synthesis of DNA-Templated Silver Nanoclusters and the Characterization of Their Optical Properties and Biological Activity. Methods Mol Biol 2023; 2709:299-307. [PMID: 37572290 PMCID: PMC10482316 DOI: 10.1007/978-1-0716-3417-2_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/14/2023]
Abstract
DNA-templated silver nanoclusters (DNA-AgNCs) are a unique class of bioinorganic nanomaterials. The optical properties and biological activities of DNA-AgNCs are readily modulated by the minor adjustments in the sequence or structure of the templating oligonucleotide. Excitation-emission matrix spectroscopy (EEMS) enables the fluorescence of compounds to be measured in a way that examines the entirety of a material's fluorescent properties. The use of EEMS for the characterization of DNA-AgNCs allows for multiple fluorescence peaks to be readily identified while providing the excitation and emission wavelengths of each signal. To assess the antibacterial and cytotoxic activities of DNA-AgNCs, two separate experimental approaches are used. Assessing the growth of bacteria over time is accomplished by measuring the optical density of the bacterial suspension with 600 nm light, which is directly related to the number of bacteria in suspension. In order to evaluate the DNA-AgNCs for cytotoxic activity, cell viability assays which probe mitochondrial activity were used. Herein, we describe protocols for the characterization of the fluorescent, antibacterial, and cytotoxic activities of DNA-AgNCs using EEM, optical density measurements, and cell viability assays.
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11
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Li M, He J, Shang X, Yang C, Zhang Y, Zuo S, Yuan R, Xu W. A Reciprocal-Amplifiable Fluorescence Sensing Platform via Replicated Hybridization Chain Reaction for Hosting Concatenated Multi-Ag Nanoclusters as Signal Reporter. Anal Chem 2022; 94:16427-16435. [DOI: 10.1021/acs.analchem.2c03782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Mengdie Li
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Jiayang He
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Xin Shang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Chunli Yang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Yuqing Zhang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Siyu Zuo
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Ruo Yuan
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
| | - Wenju Xu
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Southwest University), Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing400715, PR China
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12
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Torres-Huerta AL, Antonio-Pérez A, García-Huante Y, Alcázar-Ramírez NJ, Rueda-Silva JC. Biomolecule-Based Optical Metamaterials: Design and Applications. BIOSENSORS 2022; 12:962. [PMID: 36354471 PMCID: PMC9688573 DOI: 10.3390/bios12110962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/21/2022] [Accepted: 10/22/2022] [Indexed: 06/16/2023]
Abstract
Metamaterials are broadly defined as artificial, electromagnetically homogeneous structures that exhibit unusual physical properties that are not present in nature. They possess extraordinary capabilities to bend electromagnetic waves. Their size, shape and composition can be engineered to modify their characteristics, such as iridescence, color shift, absorbance at different wavelengths, etc., and harness them as biosensors. Metamaterial construction from biological sources such as carbohydrates, proteins and nucleic acids represents a low-cost alternative, rendering high quantities and yields. In addition, the malleability of these biomaterials makes it possible to fabricate an endless number of structured materials such as composited nanoparticles, biofilms, nanofibers, quantum dots, and many others, with very specific, invaluable and tremendously useful optical characteristics. The intrinsic characteristics observed in biomaterials make them suitable for biomedical applications. This review addresses the optical characteristics of metamaterials obtained from the major macromolecules found in nature: carbohydrates, proteins and DNA, highlighting their biosensor field use, and pointing out their physical properties and production paths.
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Affiliation(s)
- Ana Laura Torres-Huerta
- Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Campus Estado de México, Av. Lago de Guadalupe KM 3.5, Margarita Maza de Juárez, Cd. López Mateos, Atizapán de Zaragoza 52926, Mexico
| | - Aurora Antonio-Pérez
- Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Campus Estado de México, Av. Lago de Guadalupe KM 3.5, Margarita Maza de Juárez, Cd. López Mateos, Atizapán de Zaragoza 52926, Mexico
| | - Yolanda García-Huante
- Departamento de Ciencias Básicas, Unidad Profesional Interdisciplinaria en Ingeniería y Tecnologías Avanzadas, Instituto Politécnico Nacional (UPIITA-IPN), Mexico City 07340, Mexico
| | - Nayelhi Julieta Alcázar-Ramírez
- Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Campus Estado de México, Av. Lago de Guadalupe KM 3.5, Margarita Maza de Juárez, Cd. López Mateos, Atizapán de Zaragoza 52926, Mexico
| | - Juan Carlos Rueda-Silva
- Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Campus Estado de México, Av. Lago de Guadalupe KM 3.5, Margarita Maza de Juárez, Cd. López Mateos, Atizapán de Zaragoza 52926, Mexico
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
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13
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Chandler M, Rolband L, Johnson MB, Shi D, Avila YI, Cedrone E, Beasock D, Danai L, Stassenko E, Krueger JK, Jiang J, Lee JS, Dobrovolskaia MA, Afonin KA. Expanding Structural Space for Immunomodulatory Nucleic Acid Nanoparticles (Nanps) via Spatial Arrangement of Their Therapeutic Moieties. ADVANCED FUNCTIONAL MATERIALS 2022; 32:2205581. [PMID: 37008199 PMCID: PMC10065476 DOI: 10.1002/adfm.202205581] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Indexed: 05/16/2023]
Abstract
Different therapeutic nucleic acids (TNAs) can be unified in a single structure by their elongation with short oligonucleotides designed to self-assemble into nucleic acid nanoparticles (NANPs). With this approach, therapeutic cocktails with precisely controlled composition and stoichiometry of active ingredients can be delivered to the same diseased cells for enhancing pharmaceutical action. In this work, an additional nanotechnology-based therapeutic option that enlists a biocompatible NANP-encoded platform for their controlled patient-specific immunorecognition is explored. For this, a set of representative functional NANPs is extensively characterized in vitro, ex vivo, and in vivo and then further analyzed for immunostimulation of human peripheral blood mononuclear cells freshly collected from healthy donor volunteers. The results of the study present the advancement of the current TNA approach toward personalized medicine and offer a new strategy to potentially address top public health challenges related to drug overdose and safety through the biodegradable nature of the functional platform with immunostimulatory regulation.
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Affiliation(s)
- Morgan Chandler
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Lewis Rolband
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - M Brittany Johnson
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Da Shi
- Nanotechnology Characterization Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Yelixza I Avila
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Edward Cedrone
- Nanotechnology Characterization Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Damian Beasock
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Leyla Danai
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Elizabeth Stassenko
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Joanna K Krueger
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Jiancheng Jiang
- Department of Mathematics, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Jeoung Soo Lee
- Drug Design, Development, and Delivery (4D) Laboratory, Department of Bioengineering, Clemson University, Clemson, SC 29634, USA
| | - Marina A Dobrovolskaia
- Nanotechnology Characterization Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Kirill A Afonin
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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14
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Yang T, Xie Y, Zhang S, He X. Synthesis of Dual Red‐Emitting Fluorescent Silver Nanoclusters in Aqueous Lipoic Acid‐Based Polymer Solutions and Application for Cu
2+
Detection and Cell Imaging. ChemistrySelect 2022. [DOI: 10.1002/slct.202200185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Tao Yang
- School of Chemistry and Molecular Engineering East China Normal University Shanghai 200241 China
| | - Yangchun Xie
- School of Chemistry and Molecular Engineering East China Normal University Shanghai 200241 China
| | - Sanjun Zhang
- State Key Laboratory of Precision Spectroscopy East China Normal University Shanghai 200241 China
| | - Xiaohua He
- School of Chemistry and Molecular Engineering East China Normal University Shanghai 200241 China
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15
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Zhu G, Song P, Wu J, Luo M, Chen Z, Chen T. Application of Nucleic Acid Frameworks in the Construction of Nanostructures and Cascade Biocatalysts: Recent Progress and Perspective. Front Bioeng Biotechnol 2022; 9:792489. [PMID: 35071205 PMCID: PMC8777461 DOI: 10.3389/fbioe.2021.792489] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 12/10/2021] [Indexed: 12/12/2022] Open
Abstract
Nucleic acids underlie the storage and retrieval of genetic information literally in all living organisms, and also provide us excellent materials for making artificial nanostructures and scaffolds for constructing multi-enzyme systems with outstanding performance in catalyzing various cascade reactions, due to their highly diverse and yet controllable structures, which are well determined by their sequences. The introduction of unnatural moieties into nucleic acids dramatically increased the diversity of sequences, structures, and properties of the nucleic acids, which undoubtedly expanded the toolbox for making nanomaterials and scaffolds of multi-enzyme systems. In this article, we first introduce the molecular structures and properties of nucleic acids and their unnatural derivatives. Then we summarized representative artificial nanomaterials made of nucleic acids, as well as their properties, functions, and application. We next review recent progress on constructing multi-enzyme systems with nucleic acid structures as scaffolds for cascade biocatalyst. Finally, we discuss the future direction of applying nucleic acid frameworks in the construction of nanomaterials and multi-enzyme molecular machines, with the potential contribution that unnatural nucleic acids may make to this field highlighted.
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Affiliation(s)
- Gan Zhu
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Ping Song
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Jing Wu
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Minglan Luo
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Zhipeng Chen
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Tingjian Chen
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
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16
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Hg2+ Detection with Rational Design of DNA-Templated Fluorescent Silver Nanoclusters. Processes (Basel) 2021. [DOI: 10.3390/pr9101699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Atomically precise silver nanoclusters (AgNCs) are small nanostructures consisting of only a few atoms of silver. The combination of AgNCs with cytosine-rich single-stranded oligonucleotides results in DNA-templated silver nanoclusters (DNA-AgNCs). DNA-AgNCs are highly luminescent and can be engineered with reproducible and unique fluorescent properties. Furthermore, using nucleic acids as templates for the synthesis of AgNCs provides additional practical benefits by expanding optical activity beyond the visible spectral range and creating the possibility for color tunability. In this study, we explore DNA oligonucleotides designed to fold into hairpin-loop (HL) structures which modulate optical properties of AgNCs based on the size of the loop containing different number of cytosines (HL-CN). Depending on the size of the loop, AgNCs can be manufactured to have either single or multiple emissive states. Such hairpin-loop structures provide an additional stability for AgNCs and further control over the base composition of the loop, allowing for the rational design of AgNCs’ optical properties. We demonstrate the potential of AgNCs in detecting Hg2+ by utilizing the HL-C13 design and its variants HL-T2C11, HL-T4C9, and HL-T6C7. The replacement of cytosines with thymines in the loop was intended to serve as an additional sink for mercury ions extending the detectable range of Hg2+. While AgNC@HL-T0C13 exhibits an interpretable quenching curve, AgNC@HL-T6C7 provides the largest detectable range of Hg2+. The results presented herein suggest that it is possible to use a rational design of DNA-AgNCs based on the composition of loop sequence in HL structures for creating biosensors to detect heavy metals, particularly Hg2+.
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17
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Li Y, Xi W, Hussain I, Chen M, Tan B. Facile preparation of silver nanocluster self-assemblies with aggregation-induced emission by equilibrium shifting. NANOSCALE 2021; 13:14207-14213. [PMID: 34477702 DOI: 10.1039/d1nr03445f] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Aggregation-induced emission is a promising pathway to get high photoluminescence from metal nanocluster assemblies. The self-assembly of metal nanoclusters with regular morphologies can restrict the rotation and vibration modes of capping ligands, reduce nanoclusters' non-radiative decay, and finally result in an aggregation-induced strong emission. In this study, silver nanocluster self-assemblies stabilized by thiosalicylic acid (TSA) were prepared in water by equilibrium shifting, which exhibit nanofiber-like morphologies. The resulting silver nanocluster self-assemblies exhibit aggregation-induced emission in solid or aggregated state with a decent quantum yield i.e., 13.05%. The obtained silver nanocluster self-assemblies were thoroughly characterized by fluorescence spectroscopy, UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), matrix assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF), powder X-ray diffraction (PXRD) and high-resolution transmission electron microscopy (HRTEM). These silver nanocluster self-assemblies with high photoluminescence in aggregated state may have potential use in light emitting devices and bioapplications.
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Affiliation(s)
- Yulian Li
- Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China.
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18
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Rolband L, Yourston L, Chandler M, Beasock D, Danai L, Kozlov S, Marshall N, Shevchenko O, Krasnoslobodtsev AV, Afonin KA. DNA-Templated Fluorescent Silver Nanoclusters Inhibit Bacterial Growth While Being Non-Toxic to Mammalian Cells. Molecules 2021; 26:4045. [PMID: 34279383 PMCID: PMC8271471 DOI: 10.3390/molecules26134045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/21/2021] [Accepted: 06/29/2021] [Indexed: 11/16/2022] Open
Abstract
Silver has a long history of antibacterial effectiveness. The combination of atomically precise metal nanoclusters with the field of nucleic acid nanotechnology has given rise to DNA-templated silver nanoclusters (DNA-AgNCs) which can be engineered with reproducible and unique fluorescent properties and antibacterial activity. Furthermore, cytosine-rich single-stranded DNA oligonucleotides designed to fold into hairpin structures improve the stability of AgNCs and additionally modulate their antibacterial properties and the quality of observed fluorescent signals. In this work, we characterize the sequence-specific fluorescence and composition of four representative DNA-AgNCs, compare their corresponding antibacterial effectiveness at different pH, and assess cytotoxicity to several mammalian cell lines.
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Affiliation(s)
- Lewis Rolband
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Liam Yourston
- Department of Physics, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Morgan Chandler
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Damian Beasock
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Leyla Danai
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Seraphim Kozlov
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Nolan Marshall
- Department of Physics, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Oleg Shevchenko
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | | | - Kirill A Afonin
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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19
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Gonzàlez-Rosell A, Cerretani C, Mastracco P, Vosch T, Copp SM. Structure and luminescence of DNA-templated silver clusters. NANOSCALE ADVANCES 2021; 3:1230-1260. [PMID: 36132866 PMCID: PMC9417461 DOI: 10.1039/d0na01005g] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/21/2021] [Indexed: 05/05/2023]
Abstract
DNA serves as a versatile template for few-atom silver clusters and their organized self-assembly. These clusters possess unique structural and photophysical properties that are programmed into the DNA template sequence, resulting in a rich palette of fluorophores which hold promise as chemical and biomolecular sensors, biolabels, and nanophotonic elements. Here, we review recent advances in the fundamental understanding of DNA-templated silver clusters (Ag N -DNAs), including the role played by the silver-mediated DNA complexes which are synthetic precursors to Ag N -DNAs, structure-property relations of Ag N -DNAs, and the excited state dynamics leading to fluorescence in these clusters. We also summarize the current understanding of how DNA sequence selects the properties of Ag N -DNAs and how sequence can be harnessed for informed design and for ordered multi-cluster assembly. To catalyze future research, we end with a discussion of several opportunities and challenges, both fundamental and applied, for the Ag N -DNA research community. A comprehensive fundamental understanding of this class of metal cluster fluorophores can provide the basis for rational design and for advancement of their applications in fluorescence-based sensing, biosciences, nanophotonics, and catalysis.
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Affiliation(s)
- Anna Gonzàlez-Rosell
- Department of Materials Science and Engineering, University of California Irvine California 92697-2585 USA
| | - Cecilia Cerretani
- Nanoscience Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5 2100 Copenhagen Denmark
| | - Peter Mastracco
- Department of Materials Science and Engineering, University of California Irvine California 92697-2585 USA
| | - Tom Vosch
- Nanoscience Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5 2100 Copenhagen Denmark
| | - Stacy M Copp
- Department of Materials Science and Engineering, University of California Irvine California 92697-2585 USA
- Department of Physics and Astronomy, University of California Irvine California 92697-4575 USA
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20
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de la Hoz A, Navarro A, Aviñó A, Eritja R, Gargallo R. Studies on the interactions of Ag(i) with DNA and their implication on the DNA-templated synthesis of silver nanoclusters and on the interaction with complementary DNA and RNA sequences. RSC Adv 2021; 11:9029-9042. [PMID: 35423401 PMCID: PMC8695332 DOI: 10.1039/d1ra00194a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Accepted: 02/15/2021] [Indexed: 12/22/2022] Open
Abstract
Silver nanoclusters (AgNCs) prepared by the reduction of silver ions in the presence of DNA oligonucleotides have attracted great interest as potential diagnostic tools for their tunable and high fluorescent properties. In this work, three DNA sequences that consist of a 12-nucleotide long probe sequence at the 5′-end linked to the complementary sequence to three miRNAs are studied. First, the interaction of these sequences with Ag(i) was characterized by means of circular dichroism spectroscopy. By applying multivariate methods to the analysis of spectroscopic data, two complexes with different Ag(i) : DNA ratios were resolved. Secondly, the impact of several experimental variables, such as temperature, borohydride concentration and reaction time, on the formation of AgNCs templated by these three sequences was studied. Finally, the fluorescence properties of the duplexes formed by DNA probes with complementary DNA or miRNA sequences were studied. The results presented here highlight the role of the secondary structure adopted by the DNA probe on the fluorescence properties of DNA-stabilized AgNCs which, in turn, affect the development of methods for miRNA detection. Variables affecting the fluorescent properties of DNA-stabilized silver nanoclusters are studied. The secondary structure of the AgNC-stabilizing DNA sequence dramatically affects the analytical signal behind the hybridization reaction.![]()
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Affiliation(s)
- Alejandra de la Hoz
- Dept. of Chemical Engineering and Analytical Chemistry, University of Barcelona Marti i Franquès 1 E-08028 Barcelona Spain
| | - Alba Navarro
- Dept. of Chemical Engineering and Analytical Chemistry, University of Barcelona Marti i Franquès 1 E-08028 Barcelona Spain
| | - Anna Aviñó
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN Jordi Girona 18-26 E-08034 Barcelona Spain
| | - Ramon Eritja
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN Jordi Girona 18-26 E-08034 Barcelona Spain
| | - Raimundo Gargallo
- Dept. of Chemical Engineering and Analytical Chemistry, University of Barcelona Marti i Franquès 1 E-08028 Barcelona Spain
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21
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Yourston LE, Krasnoslobodtsev AV. Micro RNA Sensing with Green Emitting Silver Nanoclusters. Molecules 2020; 25:E3026. [PMID: 32630693 PMCID: PMC7411700 DOI: 10.3390/molecules25133026] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 06/25/2020] [Accepted: 06/30/2020] [Indexed: 12/11/2022] Open
Abstract
Micro RNA (miR) are regulatory non-coding RNA molecules, which contain a small number of nucleotides ~18-28 nt. There are many various miR sequences found in plants and animals that perform important functions in developmental, metabolic, and disease processes. miRs can bind to complementary sequences within mRNA molecules thus silencing mRNA. Other functions include cardiovascular and neural development, stem cell differentiation, apoptosis, and tumors. In tumors, some miRs can function as oncogenes, others as tumor suppressors. Levels of certain miR molecules reflect cellular events, both normal and pathological. Therefore, miR molecules can be used as biomarkers for disease diagnosis and prognosis. One of these promising molecules is miR-21, which can serve as a biomarker with high potential for early diagnosis of various types of cancer. Here, we present a novel design of miR detection and demonstrate its efficacy on miR-21. The design employs emissive properties of DNA-silver nanoclusters (DNA/AgNC). The detection probe is designed as a hairpin DNA structure with one side of the stem complimentary to miR molecule. The binding of target miR-21 opens the hairpin structure, dramatically modulating emissive properties of AgNC hosted by the C12 loop of the hairpin. "Red" fluorescence of the DNA/AgNC probe is diminished in the presence of the target miR. At the same time, "green" fluorescence is activated and its intensity increases several-fold. The increase in intensity of "green" fluorescence is strong enough to detect the presence of miR-21. The intensity change follows the concentration dependence of the target miR present in a sample, which provides the basis of developing a new, simple probe for miR detection. The detection strategy is specific, as demonstrated using the response of the DNA/AgNC probe towards the scrambled miR-21 sequence and miR-25 molecule. Additionally, the design reported here is very sensitive with an estimated detection limit at ~1 picomole of miR-21.
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