“…52 The reactivity between catechols and amines is exploited in the development of multifunctional coatings through a reaction between a catechol and diamine species. 28,30,53,54 One should consider the possibility of intermolecularly, N-to-C, bonded units of catecholamines when evaluating the structure of melanins, polydopamines, etc.…”
Section: Scheme 2: Comparison Between the Intra-and Intermolecular Sumentioning
<p>We investigated the
synthesis of melanin-like materials from DOPA, dopamine, norepinephrine and
epinephrine in the presence of L-cysteine. We observed that L-cysteine delayed
the formation of pigment from these catecholamines and that the presence of
L-cysteine yielded darker-colored reaction mixtures. No reddish pigment was
observed that would indicate the synthesis of pheomelanin-like material. The
reactions were performed in the presence of Na<sub>2</sub>CO<sub>3</sub> and
through the addition of CaCl<sub>2</sub> at the end of the reaction; the black,
eumelanin-like material was co-precipitated with CaCO<sub>3</sub>. The
remaining supernatant solutions were observed to be light-yellow to
rusty-orange in color depending on the catecholamine used in the reaction. Size
exclusion chromatography (SEC) analyses indicated that the removal of the black
pigment left behind an oligomeric material that exhibited a strong absorbance
band around 280nm. Our experimental and analytical observations prompt us to
raise a number of points of discussion or hypotheses. 1) The
presence of L-cysteine during the air-mediated oxidation of catecholamines
leads to darker-colored pigments; not reddish or lighter-colored pigments that
would visually resemble pheomelanin-like pigments, 2) SEC analyses suggested
that the black pigment generated during the air-mediated oxidation of
catecholamines is not necessarily the main reaction product, 3) The pre-formed,
dark-colored pigments obtained through the air-mediated oxidative melanogenesis
process can readily be deposited on insoluble mineral surfaces using an <i>in situ</i> co-precipitation procedure, 4)
The air-mediated oxidation of catecholamines leads to a binary product that
contains an insoluble, melanin-like substance and a soluble, oligo- or
polymeric substance containing unoxidized precursor units, 5) The melanogenesis
process leads to a binary product involving a non-covalently bonded combination
of dark-colored pigment and a lighter-colored or colorless substance; the
latter being understudied or ignored in the <i>in
vitro</i> or <i>in vivo</i> studies of the
melanogenesis process, 6) The kinetics of the melanogenesis process may
determine the balance between insoluble and soluble components of the binary
product generated; the slower the reaction the more dark-colored, insoluble
pigment generated, 7) One should consider the possibility of intermolecularly,
N-to-C, bonded units of catecholamines when evaluating the structure of
melanins, polydopamines, etc. and 8) There is a need for a systematic study of
the effect of amino acids (beyond just L-cysteine) and amines in general on the
melanogenesis process.</p>
“…52 The reactivity between catechols and amines is exploited in the development of multifunctional coatings through a reaction between a catechol and diamine species. 28,30,53,54 One should consider the possibility of intermolecularly, N-to-C, bonded units of catecholamines when evaluating the structure of melanins, polydopamines, etc.…”
Section: Scheme 2: Comparison Between the Intra-and Intermolecular Sumentioning
<p>We investigated the
synthesis of melanin-like materials from DOPA, dopamine, norepinephrine and
epinephrine in the presence of L-cysteine. We observed that L-cysteine delayed
the formation of pigment from these catecholamines and that the presence of
L-cysteine yielded darker-colored reaction mixtures. No reddish pigment was
observed that would indicate the synthesis of pheomelanin-like material. The
reactions were performed in the presence of Na<sub>2</sub>CO<sub>3</sub> and
through the addition of CaCl<sub>2</sub> at the end of the reaction; the black,
eumelanin-like material was co-precipitated with CaCO<sub>3</sub>. The
remaining supernatant solutions were observed to be light-yellow to
rusty-orange in color depending on the catecholamine used in the reaction. Size
exclusion chromatography (SEC) analyses indicated that the removal of the black
pigment left behind an oligomeric material that exhibited a strong absorbance
band around 280nm. Our experimental and analytical observations prompt us to
raise a number of points of discussion or hypotheses. 1) The
presence of L-cysteine during the air-mediated oxidation of catecholamines
leads to darker-colored pigments; not reddish or lighter-colored pigments that
would visually resemble pheomelanin-like pigments, 2) SEC analyses suggested
that the black pigment generated during the air-mediated oxidation of
catecholamines is not necessarily the main reaction product, 3) The pre-formed,
dark-colored pigments obtained through the air-mediated oxidative melanogenesis
process can readily be deposited on insoluble mineral surfaces using an <i>in situ</i> co-precipitation procedure, 4)
The air-mediated oxidation of catecholamines leads to a binary product that
contains an insoluble, melanin-like substance and a soluble, oligo- or
polymeric substance containing unoxidized precursor units, 5) The melanogenesis
process leads to a binary product involving a non-covalently bonded combination
of dark-colored pigment and a lighter-colored or colorless substance; the
latter being understudied or ignored in the <i>in
vitro</i> or <i>in vivo</i> studies of the
melanogenesis process, 6) The kinetics of the melanogenesis process may
determine the balance between insoluble and soluble components of the binary
product generated; the slower the reaction the more dark-colored, insoluble
pigment generated, 7) One should consider the possibility of intermolecularly,
N-to-C, bonded units of catecholamines when evaluating the structure of
melanins, polydopamines, etc. and 8) There is a need for a systematic study of
the effect of amino acids (beyond just L-cysteine) and amines in general on the
melanogenesis process.</p>
“…This is consistent with reported studies that the self-polymerization of catechol cannot form good coatings in the absence of nucleophiles. 5,9,23,24 The addition of nucleophilic additives may overcome the limitations in the use of NADOPAMe and other catechols as monomers. Thus, an amended protocol was developed ( Fig.…”
Section: Coatings From Copolymerization Of Nadopame and Various Diffementioning
confidence: 99%
“…8 PDA is believed to result from oxidative polymerization reactions, via a combination of interand intra-molecular reactions of intermediates derived from the dopamine quinone. 1,9,10 The structure of PDA is proposed to be oligomeric in nature, with the coatings comprising of aggregates of such oligomers held through covalent and noncovalent interactions. 11 The precise structure of PDA is, however, still controversial despite significant efforts to elucidate its structure.…”
Section: Introductionmentioning
confidence: 99%
“…Surprisingly, there are only limited reports on the use of such a strategy in the development of new materials. 9,[17][18][19][20][21] Our interest is in the use of 3,4-dihydroxyphenylalanine (DOPA) derivatives as monomers to form coatings on substrates. In this study, N-Ac methyl ester of DOPA (NADOPAMe) was used to prevent the formation of complex eumelanin-like polymers, 22 so that, the formed polymers may have more welldefined compositions compared to that of PDA.…”
Biomimetic poly(catecholamine) coatings have gained much attention in recent years due to their versatility as functional materials. Despite this, only limited methods are available to modify the function and property of poly(catecholamine) coatings, primarily through post-modification methods. Our approach reported herein provides a simple approach to the fabrication of novel functionalized poly(catecholamine) coatings. The strategy employs the copolymerization of N-Ac-3,4-dihydroxyphenylalanine methyl ester (NADOPAMe) with nucleophilic additives, giving rise to nano-coatings on various surfaces including plastic, metal, glass and polymers. With the appropriate choice of nucleophilic additives, coatings with desired properties can be achieved. This is demonstrated through the fabrication of a redox responsive coating based on NADOPAMe with cysteamine as additive, which shows a concentration-dependent glutathione (GSH) responsive behavior. The ability to utilize this as a controlled release system is also demonstrated.
“…The ratio of ECs to SMCs in coculture condition has a significant rise for GA concentrations of 5 lg/ml. 78 Except of these adhesive proteins, anti-CD34 antibodies and VEGF were also coimmobilized onto the GA modified PPAam surface. For the design of novel DES, GA with a released concentration of 5 lg/ml may be a suitable candidate to be loaded in a polymer coating.…”
In this review, the authors summarize the developments in surface modification of cardiovascular materials especially in author's laboratory. The authors focus on three different strategies to construct multifunctional surfaces including coimmobilization of various biomolecules on stent surfaces, stem cell based therapy systems, and a single-molecule multipurpose modification strategy in vascular interventional therapy. The roles of various molecules like heparin, gallic acid, various aptamers, and nitric oxide are highlighted in the new strategies for developing cardiovascular stent surfaces with novel functions including excellent hemocompatibility, inhibiting smooth muscle cells proliferation, and native endothelium regeneration. The success of these multifunctional surfaces provides the tremendous potential in designing the next generation of vascular stents.
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