2. Academic Validation
  3. Graphene Quantum Dot Oxidation Governs Noncovalent Biopolymer Adsorption

Graphene Quantum Dot Oxidation Governs Noncovalent Biopolymer Adsorption

  • Sci Rep. 2020 Apr 27;10(1):7074. doi: 10.1038/s41598-020-63769-z.
Sanghwa Jeong # 1,  Rebecca L Pinals # 1,  Bhushan Dharmadhikari 2,  Hayong Song 3,  Ankarao Kalluri 4,  Debika Debnath 4,  Qi Wu 4,  Moon-Ho Ham 3,  Prabir Patra 5 6,  Markita P Landry 7 8 9 10
Affiliations

Affiliations

  • 1 Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.
  • 2 Department of Electrical and Computer Engineering & Technology, Minnesota State University, Mankato, MA, 56001, USA.
  • 3 School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea.
  • 4 Department of Biomedical Engineering, University of Bridgeport, Bridgeport, CT, 06604, USA.
  • 5 Department of Biomedical Engineering, University of Bridgeport, Bridgeport, CT, 06604, USA. ppatra@bridgeport.edu.
  • 6 Department of Mechanical Engineering, University of Bridgeport, Bridgeport, CT, 06604, USA. ppatra@bridgeport.edu.
  • 7 Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA. landry@berkeley.edu.
  • 8 Innovative Genomics Institute (IGI), Berkeley, CA, 94720, USA. landry@berkeley.edu.
  • 9 California Institute for Quantitative Biosciences, QB3, University of California, Berkeley, Berkeley, CA, 94720, USA. landry@berkeley.edu.
  • 10 Chan-Zuckerberg Biohub, San Francisco, CA, 94158, USA. landry@berkeley.edu.
  • # Contributed equally.
PMID: 32341425 DOI: 10.1038/s41598-020-63769-z
Abstract

Graphene quantum dots (GQDs) are an allotrope of carbon with a planar surface amenable to functionalization and nanoscale dimensions that confer photoluminescence. Collectively, these properties render GQDs an advantageous platform for nanobiotechnology applications, including optical biosensing and delivery. Towards this end, noncovalent functionalization offers a route to reversibly modify and preserve the pristine GQD substrate, however, a clear paradigm has yet to be realized. Herein, we demonstrate the feasibility of noncovalent polymer adsorption to GQD surfaces, with a specific focus on single-stranded DNA (ssDNA). We study how GQD oxidation level affects the propensity for polymer adsorption by synthesizing and characterizing four types of GQD substrates ranging ~60-fold in oxidation level, then investigating noncovalent polymer association to these substrates. Adsorption of ssDNA quenches intrinsic GQD fluorescence by 31.5% for low-oxidation GQDs and enables aqueous dispersion of otherwise insoluble no-oxidation GQDs. ssDNA-GQD complexation is confirmed by atomic force microscopy, by inducing ssDNA desorption, and with molecular dynamics simulations. ssDNA is determined to adsorb strongly to no-oxidation GQDs, weakly to low-oxidation GQDs, and not at all for heavily oxidized GQDs. Finally, we reveal the generality of the adsorption platform and assess how the GQD system is tunable by modifying polymer sequence and type.

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