Effects of silk degumming process on physicochemical, tensile, and optical properties of regenerated silk fibroin

Sericin removal from silk (degumming) affects material characteristics of silk fibroin (SF). Sodium carbonate is most commonly used for degumming, but numerous alternative methods are available. Herein, a systematic comparison of degumming methods is provided. Sodium carbonate, sodium oleate, trypsin, and ionic liquid are used, and materials are characterized regarding mass loss, SF content, molecular integrity of SF, refractive index, and tensile properties. Complete degumming is achieved within 30 min of using sodium carbonate, but results in significant reduction of molecular weight, shift toward less acidic charge variants, and reduction of yield- and rupture force. Sodium oleate and trypsin are inefficient and negatively affect tensile properties, while ionic liquid shows good efficiency and marginal degradation of SF but also reduced yield- and rupture force. Refractive index is not affected by degumming. These results allow rational selection of the degumming method and tuning of SF properties for biomedical applications

Oxidant-dependent antioxidant activity of polydopamine films: The chemistry-morphology interplay

Polydopamine (PDA) films allow to functionalize almost all materials with a conformal and chemically active coating. These coatings can react with reducible metallic cations and with all kinds of molecules carrying nucleophilic groups. Recently, our team extended PDA chemistry to a vast repertoire of oxidants and to acidic conditions. However, the influence of changes in the method of PDA deposition on the properties of the obtained coatings, in particular the antioxidant properties, have not been sufficiently explored. It is anticipated that the antioxidant properties should depend on the film preparation method. A combination of experimental techniques, atomic force microscopy, cyclic voltammetry and X ray photoelectron spectroscopy are used to relate the antioxidant properties of PDA films to their structural features and to their chemical composition. It is demonstrated that the antioxidant properties of PDA films are not only dependent on the type of the employed oxidant – which can be expected to affect a variable density of oxidizable groups on the surface of PDA - but also on the oxidant film morphology and roughness

Mimicking the chemistry of natural eumelanin synthesis: the ke sequence in polypeptides and in proteins allows for a specific control of nanosized functional polydopamine formation

The oxidation of dopamine and of other catecholamines leads to the formation of conformal films on the surface of all known materials and to the formation of a precipitate in solution. In some cases, it has been shown that the addition of additives in the dopamine solution, like certain surfactants or polymers, polyelectrolytes, and certain proteins, allows to get polydopamine nanoparticles of controlled size and the concomitant decrease, in an additive/dopamine dependent manner, in film formation on the surface of the reaction beaker. However, the mechanism behind this controlled oxidation and self-assembly of catecholamines is not known. In this article, it is shown that a specific diad of amino acids in proteins, namely KE, allows for specific control in the oxidation-self-assembly of dopamine to obtain polydopamine@protein core–shell nanoparticles which are biocompatible. The interactions between dopamine and the adjacent KE amino acids potentially responsible for the size control of polydopamine aggregates was investigated by molecular dynamics simulations. The obtained core– shell nanoparticles display the biological activity of the protein used to control the self- assembly of PDA. The photon to heat conversion ability of PDA is conserved in the PDA@protein particles

Contrôle de la structure et des propriétés de la polydopamine à l’état de suspension, de films et de gels pour des applications biomédicales

Face à la dynamique des océans, plusieurs organismes marins ont dû s’adapter et élaborer des stratégies d’adhésion pour survivre. En particulier, les moules sont connues pour leur extraordinaire capacité à se fixer sur une large variété de surfaces, et même dans des conditions humides. Cette prouesse a ouvert la porte à d’intenses efforts de recherche depuis une décennie pour tenter de comprendre cette propriété et s’en inspirer. Des études ont révélé la présence dans la substance adhésive des moules, une grande quantité de L-Lysine, de 3,4- dihydroxy-L-phenylalanine (DOPA) et de la 3-4-hydroxyproline (1). Il a été démontré que la combinaison de catéchols et d’amines primaires et secondaires contribue à cette forte adhésion (2). Partant de cette hypothèse, des chercheurs ont réussi à développer une synthèse simple de la polydopamine (PDA) par oxydation de la dopamine, qui est une molécule possédant justement ces deux fonctions chimiques (3). Toutefois, aujourd’hui encore, il n’existe aucun consensus quant aux mécanismes de formation de ce matériau. Cette complexité trouve son origine dans les nombreuses voies réactionnelles possibles après l’étape initiale d’oxydation. Par ailleurs, la PDA partage des caractéristiques physico-chimiques avec l’eumélanine, le pigment noir-brun responsable de la coloration de la peau. La similarité structurale entre ces deux entités confère à la PDA des propriétés intéressantes, la plus remarquable étant ses propriétés antioxydantes. Bien que la structure moléculaire et les étapes de formation de la PDA ne soient pas encore totalement élucidées, sa capacité à pouvoir adhérer à toute sorte de substrat font d’elle un matériau de choix dans de nombreuses applications en médecine, en cosmétique, dans l’industrie. Il est donc dans notre intérêt de poursuivre les efforts de recherche dans ce domaine. C’est dans ce contexte que s’inscrit cette thèse qui peut se diviser en trois axes : une première partie a consisté à optimiser la méthode de synthèse de la PDA et à former et développer une technique de contrôle des nanoparticules de PDA. Utilisant les avancées de cette étape, un intérêt particulier a été accordé à l’étude physico-chimique de films de PDA afin de mieux comprendre ses mécanismes de formation pour pouvoir ensuite mieux les contrôler. Enfin, une attention particulière a été donnée à l’étude d’une application de gel formé à partir de PDA en s’appuyant sur les découvertes des deux premiers axes...Because of the dynamics of the oceans, several marine organisms have had to adapt and develop adhesive strategies in order to survive. In particular, marine mussels are known for their extraordinary ability to attach to a wide variety of surfaces, and even in wet conditions. This feat has opened the door to intense research efforts over the past decade to attempt to understand and be inspired by this property. Studies have shown the presence in the adhesive substance of the mussels, a large amount of L-Lysine, 3,4-dihydroxy-L-phenylalanine (DOPA) and 3-4-hydroxyproline (1). The combination of catechols and primary and secondary amines has been shown to contribute to this strong adhesion (2). Based on this hypothesis, researchers have succeeded in developing a simple synthesis of polydopamine (PDA) by oxidation of dopamine, which is a molecule with precisely these two chemical functions (3). However, even today, there is no consensus on the mechanisms of formation of this material. This complexity stems from the many possible reaction pathways after the initial oxidation step. In addition, PDA shares physicochemical characteristics with eumelanin, the black-brown pigment responsible for the coloring of the skin. The structural similarity between these two entities gives PDA interesting properties, the most remarkable being its antioxidant properties. Although the molecular structure and the stages of formation of PDA are not yet fully understood, its ability to adhere to any kind of substrate makes it a material of choice in many applications in medicine, cosmetics, industry… It is therefore in our interest to continue research efforts in this area. It is in this context that this thesis fits, which can be divided into three axes: a first part consisted in optimizing the method of PDA synthesis and in training and developing a technique for controlling PDA nanoparticles. Using the advances of this step, interest was given to the physicochemical study of PDA films in order to better understand its formation mechanisms in order to then be able to better control them. Finally, special attention was given to the study of an application of gel formed from PDA based on the findings of the first two axes..

Contrôle de la structure et des propriétés de la polydopamine à l’état de suspension, de films et de gels pour des applications biomédicales

Because of the dynamics of the oceans, several marine organisms have had to adapt and develop adhesive strategies in order to survive. In particular, marine mussels are known for their extraordinary ability to attach to a wide variety of surfaces, and even in wet conditions. This feat has opened the door to intense research efforts over the past decade to attempt to understand and be inspired by this property. Studies have shown the presence in the adhesive substance of the mussels, a large amount of L-Lysine, 3,4-dihydroxy-L-phenylalanine (DOPA) and 3-4-hydroxyproline (1). The combination of catechols and primary and secondary amines has been shown to contribute to this strong adhesion (2). Based on this hypothesis, researchers have succeeded in developing a simple synthesis of polydopamine (PDA) by oxidation of dopamine, which is a molecule with precisely these two chemical functions (3). However, even today, there is no consensus on the mechanisms of formation of this material. This complexity stems from the many possible reaction pathways after the initial oxidation step. In addition, PDA shares physicochemical characteristics with eumelanin, the black-brown pigment responsible for the coloring of the skin. The structural similarity between these two entities gives PDA interesting properties, the most remarkable being its antioxidant properties. Although the molecular structure and the stages of formation of PDA are not yet fully understood, its ability to adhere to any kind of substrate makes it a material of choice in many applications in medicine, cosmetics, industry… It is therefore in our interest to continue research efforts in this area. It is in this context that this thesis fits, which can be divided into three axes: a first part consisted in optimizing the method of PDA synthesis and in training and developing a technique for controlling PDA nanoparticles. Using the advances of this step, interest was given to the physicochemical study of PDA films in order to better understand its formation mechanisms in order to then be able to better control them. Finally, special attention was given to the study of an application of gel formed from PDA based on the findings of the first two axes...Face à la dynamique des océans, plusieurs organismes marins ont dû s’adapter et élaborer des stratégies d’adhésion pour survivre. En particulier, les moules sont connues pour leur extraordinaire capacité à se fixer sur une large variété de surfaces, et même dans des conditions humides. Cette prouesse a ouvert la porte à d’intenses efforts de recherche depuis une décennie pour tenter de comprendre cette propriété et s’en inspirer. Des études ont révélé la présence dans la substance adhésive des moules, une grande quantité de L-Lysine, de 3,4- dihydroxy-L-phenylalanine (DOPA) et de la 3-4-hydroxyproline (1). Il a été démontré que la combinaison de catéchols et d’amines primaires et secondaires contribue à cette forte adhésion (2). Partant de cette hypothèse, des chercheurs ont réussi à développer une synthèse simple de la polydopamine (PDA) par oxydation de la dopamine, qui est une molécule possédant justement ces deux fonctions chimiques (3). Toutefois, aujourd’hui encore, il n’existe aucun consensus quant aux mécanismes de formation de ce matériau. Cette complexité trouve son origine dans les nombreuses voies réactionnelles possibles après l’étape initiale d’oxydation. Par ailleurs, la PDA partage des caractéristiques physico-chimiques avec l’eumélanine, le pigment noir-brun responsable de la coloration de la peau. La similarité structurale entre ces deux entités confère à la PDA des propriétés intéressantes, la plus remarquable étant ses propriétés antioxydantes. Bien que la structure moléculaire et les étapes de formation de la PDA ne soient pas encore totalement élucidées, sa capacité à pouvoir adhérer à toute sorte de substrat font d’elle un matériau de choix dans de nombreuses applications en médecine, en cosmétique, dans l’industrie. Il est donc dans notre intérêt de poursuivre les efforts de recherche dans ce domaine. C’est dans ce contexte que s’inscrit cette thèse qui peut se diviser en trois axes : une première partie a consisté à optimiser la méthode de synthèse de la PDA et à former et développer une technique de contrôle des nanoparticules de PDA. Utilisant les avancées de cette étape, un intérêt particulier a été accordé à l’étude physico-chimique de films de PDA afin de mieux comprendre ses mécanismes de formation pour pouvoir ensuite mieux les contrôler. Enfin, une attention particulière a été donnée à l’étude d’une application de gel formé à partir de PDA en s’appuyant sur les découvertes des deux premiers axes..

Polydopamine as a stable and functional nanomaterial

International audienceThe mussel inspired chemistry of dopamine leading to versatile coatings on the surface of all kinds of materials in a one pot process was considered as the unique aspect of catecholamine for a long time. Only recently, research has been undertaken to valorize the simultaneous oxidation and colloid formation in dopamine solutions in the presence of an oxidant. This mini review summarizes the synthesis methods allowing to get controlled nanomaterials, either nanoparticles, hollow capsules or nanotubes and even chiral nanomaterials from dopamine solutions. Finally the applications of those nanomaterials will be described

Enzymatically Active Polydopamine @ Alkaline Phosphatase Nanoparticles Produced by NaIO₄ Oxidation of Dopamine

Polydopamine (PDA) deposition, obtained from the oxidation of dopamine and other catecholamines, is a universal way to coat all known materials with a conformal coating which can subsequently be functionalized at will. The structural analogies between polydopamine and eumelanin, the black-brown pigment of the skin, were incited to produce stable polydopamine nanoparticles in solution, instead of amorphous precipitates obtained from the oxidation of dopamine. Herein, we demonstrate that size-controlled and colloidally stable PDA-based nanoparticles can be obtained in acidic conditions, where spontaneous auto-oxidation of dopamine is suppressed, using sodium periodate as the oxidant and a protein, like alkaline phosphatase (ALP), as a templating agent. The size of the PDA@ALP nanoparticles depends on the dopamine/enzyme ratio and the obtained particles display enzymatic activity of alkaline phosphatase, with an activity extending up to two weeks after particle synthesis. The PDA@ALP nanoparticles can be engineered in polyelectrolyte multilayered films to potentially design model biosensors

Optimization of the Elasticity and Adhesion of Catechol- or Dopamine-Loaded Gelatin Gels under Oxidative Conditions

The synthesis of surgical adhesives is based on the need to design glues that give rise to strong and fast bonds without cytotoxic side effects. A recent trend in surgical adhesives is to use gel-forming polymers modified with catechol groups, which can undergo oxidative crosslinking reactions and are strongly adhesive to all kinds on surfaces in wet conditions. We previously showed that blending gelatin with catechol can yield strong adhesion when the catechol is oxidized by a strong oxidant. Our previous work was limited to the study of the variation in the sodium periodate concentration. In this article, for an in-depth approach to the interactions between the components of the gels, the influence of the gelatin, the sodium periodate and dopamine/(pyro)catechol concentration on the storage (G') and loss (G″) moduli of the gels, as well as their adhesion on steel, have been studied by shear rheometry. The hydrogels were characterized by infrared and UV-Vis spectroscopy and the size of their pores visualized by digital microscopy and SEM after freeze drying but without further additives. In terms of adhesion between two stainless steel plates, the optimum was obtained for a concentration of 10% w/v in gelatin, 10 mM in sodium periodate, and 20 mM in phenolic compounds. Below these values, it is likely that crosslinking has not been maximized and that the oxidizing environment is weakening the gelatin. Above these values, the loss in adhesiveness may result from the disruption of the alpha helixes due to the large number of phenolic compounds as well as the maintenance of an oxidizing environment. Overall, this investigation shows the possibility to design strongly adhesive hydrogels to metal surfaces by blending gelatin with polyphenols in oxidative conditions. Keywords: gelatin adhesives; optimization; phenolic compounds

Poly(allylamine) plasma polymer coatings for an efficient retention of Ni(II) ions by ultrafiltration membranes

International audienc