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A betting vice president bettingsports lotterysweepor office pool if done pool betting definition work, is a form of gamblingspecifically a variant of parimutuel betting influenced by lotterieswhere gamblers pay a fixed price into a pool from which taxes and a house "take" or "vig" are removedand then make a selection on an outcome, usually related to sport. In an informal game, the vig is usually quite small or non-existent. The pool is evenly divided between those that have made the correct selection. There are no odds involved; each winner's payoff depends simply on the number of gamblers and the number of winners. True parimutuel bettingwhich was historically referred to as pool betting, involves both odds calculations and variable wager amounts.

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Progress in Inorganic Chemistry. Volume The chemistry of transition metal complexes containing catechol and semiquinone ligands; pp. Kim E. Lynge M. Polydopamine—A nature-inspired polymer coating for biomedical science. Liu Y. Jiang J. Antifouling and antimicrobial polymer membranes based on bioinspired polydopamine and strong hydrogen-bonded poly N -vinyl pyrrolidone ACS Appl.

ACS Appl. Ryu J. Lee M. Water detoxification by a substrate-bound catecholamine adsorbent. Farnad N. Water Air Soil Pollut. Park H. Lithium purification from aqueous solutions using bioinspired redox active melanin membranes. Herlinger E. Spontaneous Autoxidation of Dopamine.

Perkin Trans. Bernsmann F. Klosterman L. Ball V. Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism. Colloid Interface Sci. Ponzio F. Different synthesis methods allow to tune the permeability and permselectivity of dopamine-melanin films to electrochemical probes.

Del Frari D. Degradation of polydopamine coatings by sodium hypochlorite: A process depending on the substrate and the film synthesis method. Della Vecchia N. Building-block diversity in polydopamine underpins a multifunctional eumelanin-type platform tunable through a quinone control point.

Proks V. Thermal-induced transformation of polydopamine structures: An efficient route for the stabilization of the polydopamine surfaces. Kim S. Stability-enhanced polydopamine coatings on solid substrates by iron III coordination. Lim C. Nanomechanics of Poly catecholamine Coatings in Aqueous Solutions. Lebedev A. Liebscher J.

Hong S. Munoz-Munoz J. Generation of hydrogen peroxide in the melanin biosynthesis pathway. Reale S. Mass Spectrom. Gracio J. ACS Nano. Watt A. The supramolecular structure of melanin. Soft Matter. Steenken S. One-electron redox potentials of phenols. Hydroxy- and aminophenols and related compounds of biological interest. Lambert C. A pulse radiolysis investigation of the oxidation of indolic melanin precursors: Evidence for indolequinones and subsequent intermediates.

Thompson A. A pulse radiolysis investigation of the oxidation of the melanin precursors 3,4-dihydroxyphenylalanine dopa and the cysteinyldopas. Craw M. Zhang F. Ascione L. Tran M. Chemical and structural disorder in eumelanins: A possible explanation for broadband absorbance. Meredith P. Korytowski W. Bleaching of melanin pigments. Role of copper ions and hydrogen peroxide in autooxidation and photooxidation of synthetic dopa-melanin. Littrell K. Structural studies of bleached melanin by synchrotron small-angle X-ray scattering.

Effect of group II metal cations on catecholate oxidation. Effect of calcium cations on acid-base properties and free radical oxidation of dopamine and pyrocatechol. Felix C. Interactions of melanin with metal ions. Electron spin resonance evidence for chelate complexes of metal ions with free radicals.

Ishimitsu T. Mostert A. Role of semiconductivity and ion transport in the electrical conduction of melanin. Rao P. Hydration-controlled X-band EPR spectroscopy: A tool for unravelling the complexities of the solid-state free radical in eumelanin. Szpoganicz B. Pigment Cell Res. Pdop layer exhibiting zwitterionicity: A simple electrochemical interface for governing ion permeability. Gao B. Ion permeability of polydopamine films revealed using a prussian blue-based electrochemical method. Gunasekaran S.

Vibrational spectra and normal coordinate analysis of adrenaline and dopamine. Indian J. Pure Appl. Colloids Surfaces A Physicochem. Richter H. Samokhvalov A. Harrington M. Ferrari A. Interpretation of Raman spectra of disordered and amorphous carbon. Capozzi V. Raman and optical spectroscopy of eumelanin films. Albano L. Novel insights on the physicochemical properties of eumelanins and their DMSO derivatives.

Sevilla M. Chemical and structural properties of carbonaceous products obtained by hydrothermal carbonization of saccharides. A Eur. John K. The production of carbon materials by hydrothermal carbonization of cellulose. Tylli H. A raman spectroscopic study of the OH and OD torsion in 1,2-dihydroxybenzene. Fujita J. Infrared Spectra of Metal Chelate Compounds. Michaud-Soret I. Resonance Raman studies of catecholate and phenolate complexes of recombinant human tyrosine hydroxylase.

Salama S. Electronic and resonance Raman spectra of iron III complexes of enterobactin, catechol, and N -methyl-2,3-dihydroxybenzamide. Que L. Hurst S. Utilizing chemical Raman enhancement: A route for metal oxide support-based biodetection.

Musumeci A. Charkoudian L. Ryou M. Mussel-inspired polydopamine-treated polyethylene separators for high-power li-ion batteries. Nikanorov A. Types and Properties of Waters. Volume II. Poh C. The effect of VEGF functionalization of titanium on endothelial cells in vitro.

Kang K. A biofunctionalization scheme for neural interfaces using polydopamine polymer. Oyane A. Preparation and assessment of revised simulated body fluids. Misawa T. Morgan B. The effect of pH on the kinetics of spontaneous Fe II oxidation by O 2 in aqueous solution—Basic principles and a simple heuristic description. Subsequent oxidation steps and intramolecular rearrangements produce various heterocyclic species [ 22 , 28 , 29 ].

H 2 O 2 generated upon oxidation of the catechol groups by O 2 — can also generate pyrrole-carboxylic acids by cleaving 5,6-dihydroxyindole units [ 22 , 30 ]. Reactive monomers produced along the dopamine oxidation pathway oligomerize observed up to the octamer level in PDA [ 22 , 28 ] or mer for solely 5,6-dihydroxyindole DHI polymerization [ 31 ] and aggregate into disordered graphite-like nanostructures [ 32 ] akin to naturally occurring melanins [ 33 , 34 ].

The resulting PDA has a stable population of free radicals ca. Freshly-synthesized PDA films and particles are partially oxidized and contain species from all stages of the dopamine oxidation pathway [ 22 , 28 ]. Therefore, the chemical composition and subsequent physical properties of PDA films may evolve continuously over their lifetime as constituent molecules are exposed to controlled conditions after film deposition or de facto post-processing conditions via the ambient environment.

The absorbance tail through the visible region is attributed to intermolecular perturbations of convoluted oligomerization products used to explain the black color of eumelanins [ 41 , 42 , 43 ]. Inset: Original spectra; b Absorbance at the designated wavelengths over time spectra recorded every 83 s. The hour long time scales for the spectral development of CaCl 2 -incubated PDA films Figure 1 b suggests an oxygen kinetic limitation, considering that the autoxidation of dopamine solutions occurs on similar time scales Figure S1 [ 15 , 18 ].

The loss of absorption and differences in temporal development of the two peaks is attributed to peroxidative degradation of species with PDA referred to as bleaching [ 44 ], which has been observed to more strongly affect absorption in the red region for synthetic melanin [ 45 ]. Aqueous solutions of redox-inactive cations can be used as post-processing buffers to control the composition of nascent PDA films. The spectra recorded from films incubated in NaCl solutions exhibit suppressed absorbance values and less-defined peaks compared to PDA films incubated in CaCl 2 , which is likely due to relatively weak interaction of monovalent cations with catechols compared to divalent cations.

There are two weak convoluted peaks at ca. Cation-mediated oxidation of PDA films is supported by cyclic voltammetry Figure 3. The midpoint between the onset of the oxidation and reduction curves in the voltammogram is approximately mV vs. The decrease in oxidation capacity in CaCl 2 -incubated films is likely not due to mass loss i.

In addition, H 2 O 2 in alkaline solutions—generated during dopamine oxidation—can transform DHI species into pyrrole scaffolds with pendant carboxylates [ 22 ]. These species also contribute negative stationary charges in PDA films that can affect ion transport within the film [ 56 , 57 ].

The aforementioned changes in features observed in IR spectra with increasing time in alkaline CaCl 2 solution are comparable to those observed in PDA created from dopamine with increasing concentrations of chemical oxidant [ 19 ]. See Figures S9 and S10 for data at 8 and 16 h and additional deconvoluted peaks.

The formation of pyrrole carboxylic acid groups as a downstream oxidation product in CaCl 2 -oxidized PDA films is supported by zeta potential measurements. Protonation of residual dopamine-semiquinone anions p K a : 4. The more negative surface charge in oxidized PDA films is therefore attributed to pyrrole carboxylic acid groups, which are known downstream products of PDA oxidation [ 22 ], and dopamine-semiquinone.

Numbers 1—3 designate unique samples. The altered molecular composition of CaCl 2 -oxidized PDA films increases iron chelation as measured by Raman spectroscopy. Raman spectroscopy can identify iron-catechol chelates in Sepia melanin [ 61 ] and mussel byssal threads [ 62 ] which contain equivalent structural components dihydroxyindoles and catecholamines to PDA. The overall spectra and individual components of the deconvoluted spectra are observed in various disordered aromatic carbon materials such as humic acids and carbonized biopolymers [ 66 , 67 , 68 , 69 ].

CaCl 2 -oxidized PDA films exhibit clear enhanced iron chelation after incubation in iron solutions. The Raman spectra of pristine films remain unchanged before and after incubation in all iron solutions. These signatures observed in PDA are also detected in Sepia melanin [ 61 ]. The two intensified bands imply that CaCl 2 -oxidized PDA films exhibit increased iron chelation capacity compared to pristine counterparts.

Elevated iron chelation capacity in CaCl 2 -oxidized films is attributed to several factors. Pristine films exhibit more positive zeta potentials compared to CaCl 2 -oxidized films which could account for the lack of detectable iron chelation in pristine films. The most significant factor affecting iron chelation is likely the difference in iron-binding affinity between dopamine and DHI units.

The generation of downstream oxidation products of dopamine e. This is in contrast to a more actively-controlled i. Post-processing of PDA films using controlled buffer solutions has advantages over electrochemical control of cation chelation because this strategy is applicable to a wider range of substrates including insulating materials. Therefore, post-processing of PDA films can potentially be used to modulate the metal sorption properties of PDA films for application specific coatings.

Prospective applications include novel ion-exchange membranes or separation layers for electrochemical storage systems [ 12 , 13 , 14 , 78 ]. Ambient application conditions may also modulate device properties over time. In addition to selective control over cation binding, post-processing techniques can also control the amount of uncyclized dopamine in PDA films. Higher surface densities of primary amines may be useful for bioconjugation techniques that are orthogonal to catechols and carboxylates [ 10 , 80 , 81 ].

Non-cyclized primary amines may also afford strategies to control the mechanical properties of PDA films through chemical crosslinking. Taken together, the post-processing capabilities afforded by multivalent cation buffers can potentially fine-tune the properties of PDA films depending upon the application of interest. Water was purified Silicon and ITO substrates were cleaned by sonication in acetone, followed by isopropyl alcohol and then rinsed with de-ionized water ddH 2 O.

Pre-cleaned substrates were incubated in dopamine solutions in ambient air and rotational agitation 65 rpm. After 24 h the substrates were rinsed and incubated in a refreshed deposition solution for another 24 h and a total 48 h deposition time. The substrates were then rinsed and placed in ddH 2 O for 24 h then dried under a stream of N 2. PDA films were incubated in 3. After incubating the PDA films for 3 min in the desired solution to allow for solution permeation and pH equilibration , the spectra of the films were recorded every 83 s for several hours.

Submerged PDA film area was 4. High resolution scans were recorded at areas of 0. Film thickness was determined by scratching the films and measuring the height profile with atomic force microscopy AFM [ 17 ]. Post-processing of PDA films using redox-inactive metal cations can bias oxidative dopamine pathways to produce downstream products.

These results emphasize the practical considerations and limitations associated with the non-equilibrium state and heterogeneity of pristine PDA films. The balance between upstream products such as uncyclized dopamine can be balanced with downstream products such as DHI.

Therefore, while the chemical evolution of PDA films during application may not be completely avoidable, their properties upon device fabrication e. This technique could improve reproducibility of specific PDA film properties and ultimately accelerate the use of PDA as a functional material.

Oxidation pathway of dopamine in alkaline solutions exposed to O 2. The proposed structure of polydopamine consists of oligomers of all species shown [ 22 , 28 , 29 ]. Supplementary materials can be found at www. Luke Klosterman and Christopher J. Bettinger conceived and designed the experiments; Luke Klosterman performed the experiments; Luke Klosterman analyzed the data; and Luke Klosterman and Christopher J.

Bettinger wrote the paper. Read article at publisher's site DOI : Sensors Basel , 21 2 , 17 Jan ACS Omega , 3 10 , 26 Oct Artif Cells Nanomed Biotechnol , 46 sup2 , 10 May Cited by: 0 articles PMID: Int J Mol Sci , 19 1 , 12 Jan This data has been text mined from the article, or deposited into data resources. To arrive at the top five similar articles we use a word-weighted algorithm to compare words from the Title and Abstract of each citation.

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Europe PMC requires Javascript to function effectively. Recent Activity. Recent history Saved searches. Abstract Free full text 1. Introduction 2. Results and Discussion 3. Materials and Methods 4. Klosterman L 1 ,. Bettinger CJ 1. Affiliations 2 authors 1. Share this article Share with email Share with twitter Share with linkedin Share with facebook. Free full text. Int J Mol Sci.

Published online Dec PMID: Luke Klosterman 1 and Christopher J. Christopher J. Author information Article notes Copyright and License information Disclaimer. Received Nov 29; Accepted Dec This article has been cited by other articles in PMC. Go to:. Keywords: polydopamine, melanin, thin film, metal cation, dopamine oxidation. Alkaline Calcium Solutions Promote Generation of Semiquinone Radicals and Oxidative Evolution of Polydopamine PDA Films Oxidative chemical synthesis of PDA films from dopamine is a complex multi-step process Scheme 1 that includes redox processes, cyclization, polymerization, and various cleavage reactions that may serve as control points for altering the composition of PDA [ 15 , 22 , 28 ].

Open in a separate window. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Scheme 1. Click here for additional data file. Lee H. Guardingo M. Single-molecule mechanics of mussel adhesion. Pierpont C. Progress in Inorganic Chemistry. Volume The chemistry of transition metal complexes containing catechol and semiquinone ligands; pp. Kim E. Lynge M. Polydopamine—A nature-inspired polymer coating for biomedical science.

Liu Y. Jiang J. Antifouling and antimicrobial polymer membranes based on bioinspired polydopamine and strong hydrogen-bonded poly N -vinyl pyrrolidone ACS Appl. ACS Appl. Ryu J. Lee M. Water detoxification by a substrate-bound catecholamine adsorbent. Farnad N. Water Air Soil Pollut. Park H.

Lithium purification from aqueous solutions using bioinspired redox active melanin membranes. Herlinger E. Spontaneous Autoxidation of Dopamine. Perkin Trans. Bernsmann F. Klosterman L. Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism. Colloid Interface Sci. Ponzio F. Different synthesis methods allow to tune the permeability and permselectivity of dopamine-melanin films to electrochemical probes.

Del Frari D.

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Christopher J. Lab Website Publications. Education Ph. Research The Laboratory for Therapeutic Biodegradable Microsystems is broadly interested in the development of biomaterials-based MEMS for use in a wide range of biomedical applications including regenerative medicine, neural interfaces, and drug delivery. Cosmos: Artificial melanin paves way for new cosmetics and biomaterials Interfacing with the brain. Academics Admissions. None of these are compatible with soft hydrogel materials.

To combat these fundamental issues, Bettinger and his team created a new way to fabricate the electronics—decoupling the fabrication processes of the electronic part and the soft substrate it's embedded in. First, they construct the electronic part on a substrate that is compatible with high temperatures, extreme solvents, and a vacuum, and create the hydrogel substrate separately.

Then, they remove the electronic piece from its original substrate and adhere it to the hydrogel substrate. The final device contains a thin layer of electronics on a soft, flexible, and sticky substrate that has mechanical properties similar to those of the nervous system. Another challenge was creating a material that was still adhesive in fluid.

For the electrode to work it needs to stick in one place for a long period of time. The researchers studied the properties of animals like the blue mussel, which sticks to rocks underwater. They applied those same chemical principles when creating the hydrogel substrate. The fact that the nodes do not injure the tissue and do not move around means that they are able to record a stronger and more accurate signal from the firing neurons.

The probes could now be used not only to record signals, but also to stimulate therapies. For example, the electrode array in the probe could block the signal that induces inflammation in people with rheumatoid arthritis. Instead of using painkillers like opiates, an electronic-based therapy that stimulates appropriate regions of the spinal cord could be more targeted and effective, while avoiding the risk of addiction when compared to pharmaceutical-based interventions.

The electrodes can also be used for long-term recording applications, such as testing how a new drug could affect the heart. A sticky, soft electrode that can bend and flex can ensconce the heart, record its contractions, and indicate which drug might be most effective.

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This is in contrast to a more actively-controlled i. Post-processing of PDA films using controlled buffer solutions has advantages over electrochemical control of cation chelation because this strategy is applicable to a wider range of substrates including insulating materials.

Therefore, post-processing of PDA films can potentially be used to modulate the metal sorption properties of PDA films for application specific coatings. Prospective applications include novel ion-exchange membranes or separation layers for electrochemical storage systems [ 12 , 13 , 14 , 78 ].

Ambient application conditions may also modulate device properties over time. In addition to selective control over cation binding, post-processing techniques can also control the amount of uncyclized dopamine in PDA films. Higher surface densities of primary amines may be useful for bioconjugation techniques that are orthogonal to catechols and carboxylates [ 10 , 80 , 81 ]. Non-cyclized primary amines may also afford strategies to control the mechanical properties of PDA films through chemical crosslinking.

Taken together, the post-processing capabilities afforded by multivalent cation buffers can potentially fine-tune the properties of PDA films depending upon the application of interest. Water was purified Silicon and ITO substrates were cleaned by sonication in acetone, followed by isopropyl alcohol and then rinsed with de-ionized water ddH 2 O.

Pre-cleaned substrates were incubated in dopamine solutions in ambient air and rotational agitation 65 rpm. After 24 h the substrates were rinsed and incubated in a refreshed deposition solution for another 24 h and a total 48 h deposition time. The substrates were then rinsed and placed in ddH 2 O for 24 h then dried under a stream of N 2.

PDA films were incubated in 3. After incubating the PDA films for 3 min in the desired solution to allow for solution permeation and pH equilibration , the spectra of the films were recorded every 83 s for several hours. Submerged PDA film area was 4.

High resolution scans were recorded at areas of 0. Film thickness was determined by scratching the films and measuring the height profile with atomic force microscopy AFM [ 17 ]. Post-processing of PDA films using redox-inactive metal cations can bias oxidative dopamine pathways to produce downstream products. These results emphasize the practical considerations and limitations associated with the non-equilibrium state and heterogeneity of pristine PDA films.

The balance between upstream products such as uncyclized dopamine can be balanced with downstream products such as DHI. Therefore, while the chemical evolution of PDA films during application may not be completely avoidable, their properties upon device fabrication e. This technique could improve reproducibility of specific PDA film properties and ultimately accelerate the use of PDA as a functional material.

Oxidation pathway of dopamine in alkaline solutions exposed to O 2. The proposed structure of polydopamine consists of oligomers of all species shown [ 22 , 28 , 29 ]. Supplementary materials can be found at www. Luke Klosterman and Christopher J. Bettinger conceived and designed the experiments; Luke Klosterman performed the experiments; Luke Klosterman analyzed the data; and Luke Klosterman and Christopher J.

Bettinger wrote the paper. National Center for Biotechnology Information , U. Int J Mol Sci. Published online Dec Luke Klosterman 1 and Christopher J. Christopher J. Author information Article notes Copyright and License information Disclaimer. Received Nov 29; Accepted Dec This article has been cited by other articles in PMC.

Associated Data Supplementary Materials ijmss Abstract The facile preparation of conformal polydopamine PDA films on broad classes of materials has prompted extensive research into a wide variety of potential applications for PDA. Keywords: polydopamine, melanin, thin film, metal cation, dopamine oxidation. Introduction The autoxidation of dopamine in alkaline aqueous solutions produces a dark insoluble material known as polydopamine PDA.

Results and Discussion 2. Alkaline Calcium Solutions Promote Generation of Semiquinone Radicals and Oxidative Evolution of Polydopamine PDA Films Oxidative chemical synthesis of PDA films from dopamine is a complex multi-step process Scheme 1 that includes redox processes, cyclization, polymerization, and various cleavage reactions that may serve as control points for altering the composition of PDA [ 15 , 22 , 28 ]. Open in a separate window. Figure 1. Figure 2. Figure 3.

Figure 4. Figure 5. Figure 6. Materials and Methods 3. Conclusions Post-processing of PDA films using redox-inactive metal cations can bias oxidative dopamine pathways to produce downstream products. Scheme 1. Supplementary Materials Supplementary materials can be found at www. Click here for additional data file. Conflicts of Interest The authors declare no conflict of interest. References 1. Lee H. Guardingo M. Single-molecule mechanics of mussel adhesion. Pierpont C.

Progress in Inorganic Chemistry. Volume The chemistry of transition metal complexes containing catechol and semiquinone ligands; pp. Kim E. Lynge M. Polydopamine—A nature-inspired polymer coating for biomedical science. Liu Y. Jiang J. Antifouling and antimicrobial polymer membranes based on bioinspired polydopamine and strong hydrogen-bonded poly N -vinyl pyrrolidone ACS Appl. ACS Appl. Ryu J. Lee M. Water detoxification by a substrate-bound catecholamine adsorbent. Farnad N.

Water Air Soil Pollut. Park H. Lithium purification from aqueous solutions using bioinspired redox active melanin membranes. Herlinger E. Spontaneous Autoxidation of Dopamine. Perkin Trans. Bernsmann F. Klosterman L. Ball V. Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism.

Colloid Interface Sci. Ponzio F. Different synthesis methods allow to tune the permeability and permselectivity of dopamine-melanin films to electrochemical probes. Del Frari D. Degradation of polydopamine coatings by sodium hypochlorite: A process depending on the substrate and the film synthesis method. Della Vecchia N. Building-block diversity in polydopamine underpins a multifunctional eumelanin-type platform tunable through a quinone control point.

Proks V. Thermal-induced transformation of polydopamine structures: An efficient route for the stabilization of the polydopamine surfaces. Kim S. Stability-enhanced polydopamine coatings on solid substrates by iron III coordination. Lim C. Nanomechanics of Poly catecholamine Coatings in Aqueous Solutions. Lebedev A. Liebscher J. Hong S. Munoz-Munoz J. Generation of hydrogen peroxide in the melanin biosynthesis pathway.

Reale S. Mass Spectrom. Gracio J. ACS Nano. Watt A. The supramolecular structure of melanin. Soft Matter. Steenken S. One-electron redox potentials of phenols. Hydroxy- and aminophenols and related compounds of biological interest. Lambert C. A pulse radiolysis investigation of the oxidation of indolic melanin precursors: Evidence for indolequinones and subsequent intermediates.

Thompson A. A pulse radiolysis investigation of the oxidation of the melanin precursors 3,4-dihydroxyphenylalanine dopa and the cysteinyldopas. Craw M. Zhang F. Ascione L. Tran M. Chemical and structural disorder in eumelanins: A possible explanation for broadband absorbance. Meredith P. Korytowski W. Bleaching of melanin pigments. Role of copper ions and hydrogen peroxide in autooxidation and photooxidation of synthetic dopa-melanin.

Littrell K. These species also contribute negative stationary charges in PDA films that can affect ion transport within the film [ 56 , 57 ]. The aforementioned changes in features observed in IR spectra with increasing time in alkaline CaCl 2 solution are comparable to those observed in PDA created from dopamine with increasing concentrations of chemical oxidant [ 19 ].

See Figures S9 and S10 for data at 8 and 16 h and additional deconvoluted peaks. The formation of pyrrole carboxylic acid groups as a downstream oxidation product in CaCl 2 -oxidized PDA films is supported by zeta potential measurements. Protonation of residual dopamine-semiquinone anions p K a : 4.

The more negative surface charge in oxidized PDA films is therefore attributed to pyrrole carboxylic acid groups, which are known downstream products of PDA oxidation [ 22 ], and dopamine-semiquinone. Numbers 1—3 designate unique samples. The altered molecular composition of CaCl 2 -oxidized PDA films increases iron chelation as measured by Raman spectroscopy.

Raman spectroscopy can identify iron-catechol chelates in Sepia melanin [ 61 ] and mussel byssal threads [ 62 ] which contain equivalent structural components dihydroxyindoles and catecholamines to PDA. The overall spectra and individual components of the deconvoluted spectra are observed in various disordered aromatic carbon materials such as humic acids and carbonized biopolymers [ 66 , 67 , 68 , 69 ].

CaCl 2 -oxidized PDA films exhibit clear enhanced iron chelation after incubation in iron solutions. The Raman spectra of pristine films remain unchanged before and after incubation in all iron solutions. These signatures observed in PDA are also detected in Sepia melanin [ 61 ].

The two intensified bands imply that CaCl 2 -oxidized PDA films exhibit increased iron chelation capacity compared to pristine counterparts. Elevated iron chelation capacity in CaCl 2 -oxidized films is attributed to several factors. Pristine films exhibit more positive zeta potentials compared to CaCl 2 -oxidized films which could account for the lack of detectable iron chelation in pristine films.

The most significant factor affecting iron chelation is likely the difference in iron-binding affinity between dopamine and DHI units. The generation of downstream oxidation products of dopamine e. This is in contrast to a more actively-controlled i. Post-processing of PDA films using controlled buffer solutions has advantages over electrochemical control of cation chelation because this strategy is applicable to a wider range of substrates including insulating materials.

Therefore, post-processing of PDA films can potentially be used to modulate the metal sorption properties of PDA films for application specific coatings. Prospective applications include novel ion-exchange membranes or separation layers for electrochemical storage systems [ 12 , 13 , 14 , 78 ]. Ambient application conditions may also modulate device properties over time. In addition to selective control over cation binding, post-processing techniques can also control the amount of uncyclized dopamine in PDA films.

Higher surface densities of primary amines may be useful for bioconjugation techniques that are orthogonal to catechols and carboxylates [ 10 , 80 , 81 ]. Non-cyclized primary amines may also afford strategies to control the mechanical properties of PDA films through chemical crosslinking. Taken together, the post-processing capabilities afforded by multivalent cation buffers can potentially fine-tune the properties of PDA films depending upon the application of interest.

Water was purified Silicon and ITO substrates were cleaned by sonication in acetone, followed by isopropyl alcohol and then rinsed with de-ionized water ddH 2 O. Pre-cleaned substrates were incubated in dopamine solutions in ambient air and rotational agitation 65 rpm. After 24 h the substrates were rinsed and incubated in a refreshed deposition solution for another 24 h and a total 48 h deposition time.

The substrates were then rinsed and placed in ddH 2 O for 24 h then dried under a stream of N 2. PDA films were incubated in 3. After incubating the PDA films for 3 min in the desired solution to allow for solution permeation and pH equilibration , the spectra of the films were recorded every 83 s for several hours. Submerged PDA film area was 4. High resolution scans were recorded at areas of 0.

Film thickness was determined by scratching the films and measuring the height profile with atomic force microscopy AFM [ 17 ]. Post-processing of PDA films using redox-inactive metal cations can bias oxidative dopamine pathways to produce downstream products. These results emphasize the practical considerations and limitations associated with the non-equilibrium state and heterogeneity of pristine PDA films.

The balance between upstream products such as uncyclized dopamine can be balanced with downstream products such as DHI. Therefore, while the chemical evolution of PDA films during application may not be completely avoidable, their properties upon device fabrication e. This technique could improve reproducibility of specific PDA film properties and ultimately accelerate the use of PDA as a functional material. Oxidation pathway of dopamine in alkaline solutions exposed to O 2.

The proposed structure of polydopamine consists of oligomers of all species shown [ 22 , 28 , 29 ]. Supplementary materials can be found at www. Luke Klosterman and Christopher J. Bettinger conceived and designed the experiments; Luke Klosterman performed the experiments; Luke Klosterman analyzed the data; and Luke Klosterman and Christopher J. Bettinger wrote the paper. Read article at publisher's site DOI : Sensors Basel , 21 2 , 17 Jan ACS Omega , 3 10 , 26 Oct Artif Cells Nanomed Biotechnol , 46 sup2 , 10 May Cited by: 0 articles PMID: Int J Mol Sci , 19 1 , 12 Jan This data has been text mined from the article, or deposited into data resources.

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Recent Activity. Recent history Saved searches. Abstract Free full text 1. Introduction 2. Results and Discussion 3. Materials and Methods 4. Klosterman L 1 ,. Bettinger CJ 1. Affiliations 2 authors 1. Share this article Share with email Share with twitter Share with linkedin Share with facebook. Free full text. Int J Mol Sci. Published online Dec PMID: Luke Klosterman 1 and Christopher J.

Christopher J. Author information Article notes Copyright and License information Disclaimer. Received Nov 29; Accepted Dec This article has been cited by other articles in PMC. Go to:. Keywords: polydopamine, melanin, thin film, metal cation, dopamine oxidation. Alkaline Calcium Solutions Promote Generation of Semiquinone Radicals and Oxidative Evolution of Polydopamine PDA Films Oxidative chemical synthesis of PDA films from dopamine is a complex multi-step process Scheme 1 that includes redox processes, cyclization, polymerization, and various cleavage reactions that may serve as control points for altering the composition of PDA [ 15 , 22 , 28 ].

Open in a separate window. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Scheme 1. Click here for additional data file. Lee H. Guardingo M. Single-molecule mechanics of mussel adhesion. Pierpont C. Progress in Inorganic Chemistry. Volume The chemistry of transition metal complexes containing catechol and semiquinone ligands; pp. Kim E. Lynge M. Polydopamine—A nature-inspired polymer coating for biomedical science. Liu Y. Jiang J. Antifouling and antimicrobial polymer membranes based on bioinspired polydopamine and strong hydrogen-bonded poly N -vinyl pyrrolidone ACS Appl.

ACS Appl. Ryu J. Lee M. Water detoxification by a substrate-bound catecholamine adsorbent. Farnad N. Water Air Soil Pollut. Park H. Lithium purification from aqueous solutions using bioinspired redox active melanin membranes. Herlinger E. Spontaneous Autoxidation of Dopamine. Perkin Trans. Bernsmann F.

Klosterman L. Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism. Colloid Interface Sci. Ponzio F. Different synthesis methods allow to tune the permeability and permselectivity of dopamine-melanin films to electrochemical probes. Del Frari D. Degradation of polydopamine coatings by sodium hypochlorite: A process depending on the substrate and the film synthesis method. Della Vecchia N.

Building-block diversity in polydopamine underpins a multifunctional eumelanin-type platform tunable through a quinone control point. Proks V. Thermal-induced transformation of polydopamine structures: An efficient route for the stabilization of the polydopamine surfaces.

Kim S. Stability-enhanced polydopamine coatings on solid substrates by iron III coordination. Lim C. Nanomechanics of Poly catecholamine Coatings in Aqueous Solutions. Lebedev A. Liebscher J. Hong S. Munoz-Munoz J. Generation of hydrogen peroxide in the melanin biosynthesis pathway.

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