Structure of Polydopamine: A Never-Ending Story?
Abstract
Polydopamine (PDA) formed by the oxidation of dopamine is an important polymer, in particular, for coating various surfaces. It is composed of dihydroxyindole, indoledione, and dopamine units, which are assumed to be covalently linked. Although PDA has been applied in a manifold way, its structure is still under discussion. Similarities have been observed in melanins/eumelanins as naturally occurring, deeply colored polymer pigments derived from L-DOPA. Recently, an alternative structure was proposed for PDA wherein dihydroxyindoline, indolinedione, and eventually dopamine units are not covalently linked to each other but are held together by hydrogen bonding between oxygen atoms or π stacking. In this study, we show that this structural proposal is very unlikely to occur taking into account unambiguous results obtained by different analytical methods, among them (13)C CPPI MAS NMR (cross-polarization polarization-inversion magic angle spinning NMR), (1)H MAS NMR (magic angle spinning NMR), and ES-HRMS (electrospray ionization high-resolution mass spectrometry) for the first time in addition to XPS (X-ray photoelectron spectroscopy) and FTIR spectroscopy. The results give rise to a verified structural assignment of PDA wherein dihydroxyindole and indoledione units with different degrees of (un)saturation are covalently linked by C-C bonds between their benzene rings. Furthermore, proof of open-chain (dopamine) monomer units in PDA is provided. Advanced DFT calculations imply…
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PDA-assisted surface modification is strongly subjected to the formation of PDA coating on the biomaterial interface caused by the oxidation reaction of dopamine (DA) in weak alkaline solution.
“PDA-assisted surface modification is strongly subjected to the formation of PDA coating on the biomaterial interface caused by the oxidation reaction of dopamine (DA) in weak alkaline solution.”
From Polydopamine-Assisted Surface Modification for Bone Biosubstitutes (2016) · cites this paper as [38]
The "noncovalent bonding" fashion is a controversial assumption that has not been broadly acknowledged while the "covalent bonding" assumption has been partly proved via C-C bonding among the benzene rings of the dihydroxyindoline and indolinedione and open-chain monomer units.
“The “noncovalent bonding” fashion is a controversial assumption that has not been broadly acknowledged while the “covalent bonding” assumption has been partly proved via C-C bonding among the benzene rings of the dihydroxyindoline and indolinedione and open-chain monomer units [38, 50].”
From Polydopamine-Assisted Surface Modification for Bone Biosubstitutes (2016) · cites this paper as [38]
Several mechanisms of the PDA coating layer have been developed and they all consist essentially of two steps, including the autooxidation and intramolecular rearrangement of DA monomers and polymerization of DA monomers.
“Several mechanisms of the PDA coating layer have been developed and they all consist essentially of two steps as shown in Figure 1, including the autooxidation and intramolecular rearrangement of DA monomers and polymerization of DA monomers [29, 31, 38].”
From Polydopamine-Assisted Surface Modification for Bone Biosubstitutes (2016) · cites this paper as [38]
Cites
The supramolecular structure of melanin
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Corrosion properties of polydopamine coatings formed in one-step immersion process on magnesium
Singer, F., Schlesak, M., Mebert, C., Höhn, S., & Virtanen, S. (2015) · ACS Applied Materials & Interfaces · doi:10.1021/acsami.5b08760 · Cited by 128 · see citing works
Polydopamine-Assisted Surface Modification for Bone Biosubstitutes
Huang, S., Liang, N., Hu, Y., Zhou, X., & Abidi, N. (2016) · BioMed Research International · doi:10.1155/2016/2389895 · Cited by 97 · see citing works
“The “noncovalent bonding” fashion is a controversial assumption that has not been broadly acknowledged while the “covalent bonding” assumption has been partly proved via C-C bonding among the benzene rings of the dihydroxyindoline and indolinedione and open-chain monomer units [38, 50].”
Background
- Authors
- Liebscher, J., Mrówczyński, R., Scheidt, H. A., Filip, C., Hădade, N. D., Turcu, R., Bende, A., & Beck, S.
- Affiliations
- Humboldt-Universität zu Berlin (DE)
- Leipzig University (DE)
- National Institute for Research and Development of Isotopic and Molecular Technologies (RO)
- Babeș-Bolyai University (RO)
- Corresponding author
- Liebscher, Jürgen
- ORCID
- Venue
- Langmuir
- Publisher
- American Chemical Society (ACS)
- Published
- 2013-08-08
- Volume
- 29
- Issue
- 33
- Pages
- 10539-10548
- ISSN
- 0743-7463 (ISSN-L)
- 1520-5827
- OpenAlex
- W2016486725
- Cited by
- 1,058
- References
- 3
- Citations by year
- 2026: 72 · 2025: 65 · 2024: 74 · 2023: 93 · 2022: 100 · 2021: 102 · 2020: 95 · 2019: 95 · 2018: 90 · 2017: 84 · 2016: 70 · 2015: 61 · 2014: 50 · 2013: 6
- FWCI
- 24.70
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Langmuir (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Physical Sciences › Materials Science › Surfaces, Coatings and Films › Polymer Surface Interaction Studies
- Physical Sciences › Materials Science › Polymers and Plastics › Conducting polymers and applications
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › melanin and skin pigmentation
- Keywords
- polydopamine, polymer structure, covalent linkage, hydrogen bonding, π-π stacking, melanin, surface coating, DFT calculations
- MeSH terms
- Indoles, Magnetic Resonance Spectroscopy, Polymers, Photoelectron Spectroscopy
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