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Wound closure in surgeries is traditionally achieved using invasive methods such as sutures and staples. Adhesion‐based wound closure methods such as tissue adhesives, sealants, and hemostats are slowly replacing these methods due to their ease of application. Although several chemistries have been developed and used commercially for wound closure, there is still a need for better tissue adhesives from the point of view of toxicity, wet‐adhesion strength, and long‐term bonding. Catechol chemistry has shown great promise in developing wet‐set adhesives that meet these criteria. Herein, we have studied the biocompatibility of a catechol‐based copolymer adhesive, poly([dopamine methacrylamide]‐co‐[methyl methacrylate]‐co‐[poly(ethylene glycol) methyl ether methacrylate]) or poly(catechol‐MMA‐OEG), which is soluble in water. The adhesive was injected subcutaneously in a mouse model on its own and in combination with a sodium periodate crosslinker. After 72 h, 4 weeks, and 12 weeks, the mice were euthanized and subjected to histopathological analysis. Both adhesives were present and still palpable at the end of 12 weeks. The moderate inflammation observed for the poly(catechol‐MMA‐OEG) cohort at 72 h had reduced to mild inflammation at the end of 12 weeks. However, the moderate inflammatory response observed for the poly(catechol‐MMA‐OEG) + crosslinker cohort at 72 h had not subsided at 12 weeks. [ABSTRACT FROM AUTHOR]

Here, a polymer blend active layer that exhibits both electronic and adhesive properties is introduced. Various conjugated polymers are blended with a catechol‐based polymer that shows high adhesion, such that blends serve as the active layer of multifunctional sticky organic thin‐film transistors (OTFTs). Blend films maintain relatively constant field‐effect charge carrier mobility in OTFTs regardless of composition. Lap shear adhesion strength tests show that all blend films exhibit adhesive properties with adhesion values ranging from 0.05 to 4.30 MPa. With relatively consistent mobility and the presence of adhesive properties at different compositions, blends of conjugated and adhesive polymers can lead to next‐generation organic transistors for stable 3D stacking and waterproof adhesive sensors. [ABSTRACT FROM AUTHOR]

Plant‐based, nontoxic and strong adhesives that can work on different substrates allow for better product recycling. Replacing synthetic adhesives with plant based ones that perform equally well may lead to a more sustainable ecosystem. Adhesives based on zein protein, derived from corn, can be made as strong as Super Glue. Unlike petroleum‐based adhesives, this plant protein is removable and degradable. Here, adhesives from the components zein and tannic acid function well on different substrates such as metals, plastics, and wood. This work presents the properties of selected adhesive formulations including bond strengths when the substrates are changed. To achieve near Super Glue strength, each substrate requires a different adhesive formulation. Temperature‐dependent curing, (potential of hydrogen) changes, and additional variables influence adhesion. Tack testing at room temperature is measured to provide comparisons between initial bonding and that achieved after curing. Adhesion to plastic substrates is less than wood or metal, but still plenty strong to measure. Aging of adhesive solutions as well as water resistance after curing is investigated. Infrared spectroscopy data are correlated with changes in color, age, and pH of adhesives. These new adhesives may lead to a sustainable and cleaner environment. [ABSTRACT FROM AUTHOR]

NMR spectroscopy is used to investigate the reaction of trimethyl phosphate with four iron-sulfur complexes, (Fe4S4(SR)4)(super 2-), where R = C6H5, C2H5, Fe4S4(SC2H5)4](super 3-) and (Fe(SC2H5)4)(super 2-). Results show that the products vary depending upon starting iron complex. However, in each reaction, methylation occurs to release a thiolate ligand as the methyl thioether, CH3SR. There are also differences in nucleophilicity among the cour complexes as revealed by kinetic studies.

Incorporating catechols into polymers can provide strong adhesion even in moist environments, and these polymers show promise for use in several biomedical applications. Surgical adhesives must have strong bonds, be biocompatible, and function in a moist environment. Poly(lactic acid) (PLA) has a long history as a biocompatible material for hard tissue device fixation. By combining these concepts, catechol‐containing poly(lactic acid) (cPLA) polymers are created that are strongly adhesive and degrade in physiological environments. Here, we evaluated the cytocompatibility of cPLA with iron(III) or periodate (IO4−) cross‐linkers. Fibroblasts cultured in cPLA leachate or on cPLA films generally had slower growth and lower metabolism compared with PLA controls but no differences in viability. These results demonstrated that cPLA was not cytotoxic but that including catechols reduced cell health. When cPLA was cross‐linked with periodate, cells generally had reduced metabolism, slower cell growth, and poor actin fiber formation compared with PLA. These results are attributed to the cytotoxicity of periodate since cells cultured with periodate leachate had extremely low viability. Cells grown on the films of iron‐cross‐linked cPLA generally had high viability and metabolism but slower proliferation than PLA controls. These results indicate that the cPLA and iron‐cross‐linked cPLA systems are promising materials for biomedical adhesive applications. [ABSTRACT FROM AUTHOR]

1H, 31P(1H) and 199Hg(1H) NMR spectroscopic methods are used to investigate the reactions of ((CH3)4N)2(Hg(SC6H5)4) and ((C4H9)4N)(Hg(SC6H5)3) with (CH3O)3PO. Results show that the four-coordinate (Hg(SC6H5)4)(super 2-) readily dissociates a thiolate ligand, which demethylates (CH3O)3PO. The three-coordinate (Hg(SC6H5)3), however, does not dissociate a ligand and is less reactive. These results are used to explain th inactivity of the mercury derivative of Escherichia coli Ada DNA alkylation repair protein.

The reaction of ((CH3)4N)2(Zn(SC6H5)4) complex with (CH3O)3PO in the presence of DMSO was used as a model to understand the mechanism of repair of DNA alkylation damage rendered by the Ada protein of Escherichia coli. It was found that the reaction mimics the enzyme activity as the complex demethylates (CH3O)3PO. The active nucleophile in the reaction was identified to be a dissociated thiolate.

Author(s): Jonathan J. Wilker (corresponding author) [1] Ask beachgoers how mussels, barnacles and oysters attach themselves to rocks, and they will often guess that suction cups are involved. Actually, these [...]

The article presents the discussion on mussels using microfluidic assembly and vanadium for creating an adhesive anchoring in the natural environment. Topics include Iron being essential for producing blood and zinc being vital for stabilizing protein structures; mussel bonding apparatus being protein-based and composed of plaques of glue grabbing the surface and threads; and proteins being posttranslationally modified for generating catechol side chains.

Experimental studies were conducted to gain insight into the biomineralized adhesive material generated by the oyster for aggregating into large communities. The findings for the oyster cement could open new route to strategies to develop synthetic composite materials as well as better understand the components needed for healthy coastal environments.

The electron paramagnetic resonance spectra of iron bound by catecholate, tironate, and the Ac-Ala-DOPA-Thr-Pro-CON[H.sub.2] ('AdopaTP#) peptide in mono, bis, and tris coordination environments are presented. The data shows that Fe[(DOPA).sub.3] moieties and oxygen are needed to generate radical species and that protein-based radicals give a route to radical-radical coupling for generation of organic cross-links or protein-surface binding for the creation of surface bonding.

The alkylation reactions of various oxo compounds were studied in an effort to gain mechanistic insights on the cancer-preventing properties of vanadium and selenium. It is suggested that the design of new compounds for cancer prevention should incorporate reactive oxo groups with high anionic charge density.

The isolation, crystal structure and nonaqueous solution behavior of the first trinuclear vanadate is presented. The crystal structure reveals a six-membered cyclic arrangement of alternating vanadium and oxygen atoms for the anion of trinuclear vanadate and the NMR spectrum shows multiple peaks and the existence of ion pairs in acetonitrile is the only interpretation for the solution behaviour of trinuclear vanadate.

The optimum zinc center for DNA methylphosphotriester repair is (Zn(S-cys)4)2- in which the thiolate center is deactivated, aiming to improve it as a functional species. The nucleophilicity and the ability to function in DNA methylphosphotriester repair is obtained by the coordination of Cys69 to the (Zn(S-cys)3)- moiety in Ada. The new compounds (CH3)4N(Zn(SC6H5)3(MeIm)) (MeIm = 1-methylimidazole) and (Zn(SC6H5)2(MeIm)2) are synthesized to evaluate the character of alternative (Zn(S-cys)3(N-histidine))- and (Zn(S-cys)2(N-his)2) sites.

Oyster reefs help maintain coastal ecosystems by filtering water, holding silt in place, and absorbing storm surge energy. We are just beginning to understand the chemical and structural nature of the adhesive used by these animals for building such reef communities. The adhesive has a high calcium carbonate content relative to other bioadhesives, but also appreciable levels of organics, presumably for bonding. The studies presented here use X-ray absorption near edge structure spectroscopy, X-ray photoemission electron microscopy, scanning electron microscopy, and microhardness methods to understand the composition, as well as the mechanical properties, of this biological material. Oyster adhesive appears to be a heterogeneous mixture of calcium carbonate and silica inclusions arranged randomly within a matrix that lacks any observable structure. Microindentation shows inclusions are significantly harder than their surroundings. This hard plus soft strategy has been noted in other biological materials, although not in any adhesives. These compositional and structural insights help propose a mechanism by which the animals generate their adhesive. Such an intriguing structure, along with resulting mechanical implications, may help explain how oyster reefs can thrive despite being subjected to demanding forces created by predators and the environment around them. [ABSTRACT FROM AUTHOR]

The development of adhesives suitable for biomedical applications has been challenging given that these materials must exhibit sufficient adhesion strengths and biocompatibility. Biomimetic materials inspired by mussel adhesive proteins appear to contain many of the necessary characteristics for biomedical adhesives. In particular, poly[(3,4-dihydroxystyrene)- co-styrene] has been shown to be a high strength adhesive material with bonding comparable to or even greater than several commercial glues. Herein, a thorough study on the cytocompatibility of this copolymer provides insights on the suitability of a mussel-mimicking adhesive for applications development. The cytotoxicity of poly[(3,4-dihydroxystyrene)- co-styrene] was evaluated through assessment of the viability, proliferation rate, and morphology of NIH/3T3 fibroblasts when cultured with copolymer extracts or directly in contact with the adhesive. After 1 and 3 days of culture, both the copolymer alone and copolymer cross-linked with periodate exhibited minimal effects on cell viability. Likewise, cells cultured on the copolymer displayed proliferation rates and morphologies similar to cells on the poly- l-lysine control. These results indicate that poly[(3,4-dihydroxystyrene)- co-styrene] is highly cytocompatible and therefore a promising material for use where biological contact is important. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 983-990, 2016. [ABSTRACT FROM AUTHOR]

High-performance adhesives require mechanical properties tuned to demands of the surroundings. A mismatch in stiffness between substrate and adhesive leads to stress concentrations and fracture when the bonding is subjected to mechanical load. Balancing material strength versus ductility, as well as considering the relationship between adhesive modulus and substrate modulus, creates stronger joints. However, a detailed understanding of how these properties interplay is lacking. Here, a biomimetic terpolymer is altered systematically to identify regions of optimal bonding. Mechanical properties of these terpolymers are tailored by controlling the amount of a methyl methacrylate stiff monomer versus a similar monomer containing flexible poly(ethylene glycol) chains. Dopamine methacrylamide, the cross-linking monomer, is a catechol moiety analogous to 3,4-dihydroxyphenylalanine, a key component in the adhesive proteins of marine mussels. Bulk adhesion of this family of terpolymers is tested on metal and plastic substrates. Incorporating higher amounts of poly(ethylene glycol) into the terpolymer introduces flexibility and ductility. By taking a systematic approach to polymer design, the region in which material strength and ductility are balanced in relation to the substrate modulus is found, thereby yielding the most robust joints. [ABSTRACT FROM AUTHOR]

Metastable precursors are thought to play a major role in the ability of organisms to create mineralized tissues. Of particular interest are the hard and abrasion-resistant teeth formed by chitons, a class of rock-grazing mollusks. The formation of chiton teeth relies on the precipitation of metastable ferrihydrite (Fh) in an organic scaffold as a precursor to magnetite. In vitro synthesis of Fh under physiological conditions has been challenging. Using a combination of X-ray absorption and electron paramagnetic resonance spectroscopy, we show that, prior to Fh formation in the chiton tooth, iron ions are complexed by the organic matrix. In vitro experiments demonstrate that such complexes facilitate the formation of Fh under physiological conditions. These results indicate that acidic molecules may be integral to controlling Fh formation in the chiton tooth. This biological approach to polymorph selection is not limited to specialized proteins and can be expropriated using simple chemistry. [ABSTRACT FROM AUTHOR]

Marine mussels clinging to rocks inspire the development of novel materials. Characterization of mussel adhesive plaques describes a matrix of proteins containing 3,4-dihydroxyphenylalanine (DOPA), which provides cross-linking chemistry that allows mussels to attach firmly. Several synthetic polymer systems have been developed based on this DOPA chemistry. High strength bonding has been achieved with poly[(3,4-dihydroxystyrene)- co-styrene], a simplified mimic of mussel proteins in which 3,4-dihydroxystyrene provides the cross-linking and adhesion of DOPA. The poly(styrene) host polymer stands in for a protein backbone. Prior efforts showed that a monomer ratio of 1:2 3,4-dihydroxystyrene:styrene within the statistical copolymer poly[(3,4-dihydroxystyrene)- co-styrene] yields the highest adhesion. To enhance adhesive performance of this biomimetic polymer, a systematic study is carried out in which a range of cross-linking agents, cure times, cure temperatures, polymer concentrations, and fillers are examined. Lap shear adhesion testing revealed substantial increases in bond strength from each study. Consensus conditions are then determined and bonding performance is assessed on several substrates. Adhesion of this system turns out to be one of the strongest of all biomimetic polymers. These studies show that DOPA chemistry may be able to stand alongside of cyanoacrylate (e.g., Super Glue) and epoxy when it comes to high strength bonding. [ABSTRACT FROM AUTHOR]

Oligo(ethylene glycol) (OEG) and poly(ethylene glycol)(PEG) exhibitseveral desirable properties including biocompatibility and resistanceto fouling by protein adsorption. Still needed are surgical gluesand orthopedic cements, among several other materials, that displaysimilar traits. However, the very lack of interactions with othermolecules that prevents toxicity and fouling also makes adhesion elusive.In work described here the cross-linking chemistry of marine musseladhesive is combined with OEG to make a family of terpolymers. Theeffect of polymer composition upon bulk adhesion was examined. Highstrength bonding was found with a subset of the polymers containingappreciable OEG content. These structure–property insightsmay help the design of new materials for which the properties of OEGand high strength adhesion are both being sought. [ABSTRACT FROM AUTHOR]