Catechol Residues Research Articles

Mussel-Bioinspired Lignin Adhesive for Wearable Bioelectrodes.

As a natural "binder," lignin fixes cellulose in plants to foster growth and longevity. However, isolated lignin has a poor binding ability, which limits its biomedical applications. In this study, inspired by mussel adhesive proteins, acidic/basic amino acids (AAs) are introduced in alkali lignin (AL) to form ionic-π/spatial correlation interactions, followed by demethylation to create catechol residues for enhanced adhesion activity. Atomic force microscopy reveals that catechol residues are the primary adhesion structures, with basic AAs exhibiting superior synergistic effects compared to acidic AAs. Demethylated lysine-grafted AL exhibits the strongest adhesion force toward skin tissue. Molecular dynamic simulation and density functional theory calculations indicate that adhesion against skin tissue mainly results from hydrogen bonds and cation-π interactions, with the adhesion mechanism being based on the Gibbs free energy of the Schiff base reaction. In summary, a biomimetic electrode based on lignin inspired by mussel adhesive proteins is prepared; the presented method offers a straightforward strategy for the development of biomimetic adhesives. Furthermore, this mussel-inspired adhesive can be used as a wearable bioelectrode in biomedical applications.

Polydiacetylene Liposome-Based Dual-Output Optical Sensor for ppb Level Detection of Dopamine in Solution and Solid Phases.

Dopamine (DA), a neurotransmitter, plays a crucial role in regulating motor functions and emotions and can serve as a marker for several diseases. In this study, we report a highly sensitive polydiacetylenes (PDA)-based dual-output sensor for dopamine detection in both solution and solid phases that was developed by modifying PDA liposomes with boronic acid groups at the termini. This sensor exploits the high affinity between the catechol residue of dopamine and the -B(OH)2 group of the PDA-based probe (PDA-PhBA) to form boronate ester bonds, causing a stress-induced blue-to-red color change along with a steady increase in fluorescence response at λmax 622 nm. The PDA-PhBA-based sensor displays high sensitivity toward dopamine with low limit of detection of 6.2 ppb in colorimetric analysis and 0.6 ppb in fluorimetric measurements, demonstrating its dual optical output ability. The sensor works well for adrenaline, another catecholamine, with similar efficacy. Its practical applicability was validated by the successful recovery of trace level dopamine in blood serum and real water samples. Additionally, immobilizing PDA-PhBA liposomes in sodium alginate produced PDA beads for the solid-phase detection of dopamine with an limit of detection (LOD) of 59 nM (9.0 ppb) in colorimetric detection using a smartphone for capturing images and ImageJ software for analysis.

Smart zwitterionic coatings with precise pH-responsive antibacterial functions for bone implants to combat bacterial infections.

Hydrophilic antifouling coatings based on zwitterionic polymers have been widely applied for the surface modification of bone implants to combat biofilm formation and reduce the likelihood of implant-related infections. However, their long-term effectiveness is significantly limited by the lack of effective and precise antibacterial activity. Here, a pH-responsive smart zwitterionic antibacterial coating (PSB/GS coating) was designed and robustly fabricated onto titanium-base bone implants by using a facile two-step method. First, dopamine (DA) and a poly(sulfobetaine methacrylate-co-dopamine methacrylamide) (PSBDA) copolymer were deposited on implants via mussel-inspired surface chemistry, resulting in a hydrophilic base coating with abundant catechol residues. Next, an amino-rich antibiotic, gentamicin sulfate (GS), was covalently linked to the coating through the formation of acid-sensitive Schiff base bonds between the amine groups of GS and the catechol residues present in both the zwitterionic polymer and the DA component. During the initial implantation period, the hydrophilic zwitterionic polymers demonstrated the desired anti-fouling properties that could effectively reduce protein and bacterial adhesion by over 90%. With time, the bacterial proliferation led to a decrease in the microenvironment pH value, resulting in the hydrolysis of the acid-sensitive Schiff base bonds, thereby releasing GS on demand and effectively enhancing the anti-biofilm properties of coatings. Benefiting from this synergistic antifouling and smart antibacterial activities, the PSB/GS coating exerted an excellent anti-infective activity in both in vivo preoperative and postoperative infection rat models. This proposed facile yet effective coating strategy is expected to provide a promising solution to combat bone implant-related infections.

Discovery of a New Siderophore Cephalosporin, Cefiderocol

Cefiderocol is a novel siderophore-conjugated cephalosporin with a catechol residue acting as an iron chelator. Cefiderocol forms a chelating complex with ferric iron and is transported rapidly into bacterial cells through iron-uptake systems. As a result, cefiderocol shows good activity against Gram-negative bacteria, including carbapenem-resistant isolates that are causing significant global health issues. Cefiderocol has been approved for clinical use in the United States and Europe, where it is being used to treat infection caused by carbapenem-resistant Gram-negative pathogens.

Sensing platform for the highly sensitive detection of catechol based on composite coupling with conductive Ni3(HITP)2 and nanosilvers.

Catechol, which has a high toxicity and low degradability, poses significant risks to both human health and the environment. Tracking of catechol residues is essential to protect human health and to assess the safety of the environment. We constructed sensing platforms to detect catechol based on the conductive metal-organic frameworks [Ni3(HITP)2] and their nanosilver composites. The reduction process of catechol at the Ni3(HITP)2/AgNP electrode is chemically irreversible as a result of the difference in compatibility of the oxidation stability and conductivity between the Ni3(HITP)2/AgNS and Ni3(HITP)2/AgNP electrodes. The electrochemical results show that the Ni3(HITP)2/AgNS electrode presents a lower detection limit of 0.053 μM and better sensitivity, reproducibility and repeatability than the Ni3(HITP)2/AgNP electrode. The kinetic mechanism of the catechol electrooxidation at the surface of the electrode is controlled by diffusion through a 2H+/2e- process. The transfer coefficient is the key factor used to illustrate this process. During the electrochemical conversion of phenol to ketone, more than half of ΔG is used to change the activation energy. We also studied the stability, anti-interference and reproducibility of these electrode systems.

Facile Synthesis of Catechol-Containing Polyacrylamide Copolymers: Synergistic Effects of Amine, Amide and Catechol Residues in Mussel-Inspired Adhesives.

The straightforward synthesis of polyamide-derived statistical copolymers with catechol, amine, amide and hydroxy residues via free radical polymerization is presented. In particular, catechol, amine and amide residues are present in natural mussel foot proteins, enabling strong underwater adhesion due to synergistic effects where cationic residues displace hydration and ion layers, followed by strong short-rang hydrogen bonding between the catechol or primary amides and SiO2 surfaces. The present study is aimed at investigating whether such synergistic effects also exist for statistical copolymer systems that lack the sequence-defined positioning of functional groups in mussel foot proteins. A series of copolymers is established and the adsorption in saline solutions on SiO2 is determined by quartz crystal microbalance measurements and ellipsometry. These studies confirm a synergy between cationic amine groups with catechol units and primary amide groups via an increased adsorptivity and increased polymer layer thicknesses. Therefore, the free radical polymerization of catechol, amine and amide monomers as shown here may lead to simplified mussel-inspired adhesives that can be prepared with the readily scalable methods required for large-scale applications.

Bio-inspired conductive adhesive based on calcium-free alginate hydrogels for bioelectronic interfaces

Electrode impedance is one of the greatest challenges facing neural interfacing medical devices and the use of electrical stimulation-based therapies in the fields of neurology and regenerative medicine. Maximizing contact between electronics and tissue would allow for more accurate recordings of neural activity and to stimulate with less power in implantable devices as electric signals could be more precisely transferred by a stable interfacial area. Neural environments, inherently wet and ion-rich, present a unique challenge for traditional conductive adhesives. As such, we look to marine mussels that use a 3,4-dihydroxyphenyl-L-analine (DOPA)-containing proteinaceous excretion to adhere to a variety of substrates for inspiration. By functionalizing alginate, which is an abundantly available natural polymer, with the catechol residues DOPA contains, we developed a hydrogel-based matrix to which carbon-based nanofiller was added to render it conductive. The synthesized product had adhesive energy within the range of previously reported mussel-based polymers, good electrical properties and was not cytotoxic to brain derived neural precursor cells.

Red emission nitrogen and zinc co-doped carbon dots as fluorescent sensor for reversible detection of peroxynitrite in living cells

Reactive oxygen species (ROS), including ONOO-, H2O2, ClO-, etc, are inevitable products of aerobic metabolism. They involved in physiological processes and have concentration-dependent influences. Furthermore, their intracellular contents are always in a state of flux. Since then, the reversible and dynamic monitoring of ROS is of great significance. Till now, only a few nano sensors could achieve reversible detection of ROS, and their fluorescence wavelengths are short. Herein, we developed N, Zn co-doped CDs (NZnCDs) with red fluorescence for selective and reversible detection of ONOO-. The NZnCDs possess catechol residues on their surface. The reversible transition of quinone/phenol and their different effect on fluorescence of the CDs lay the foundation of the redox reversible sensor. With emission wavelength of 619 nm and quantum yield of 0.21, NZnCDs can selectively respond to ONOO-, giving a good linearity in 2–40 μM, and can be efficiently recovered by GSH. Finally, the proposed rare redox reversible CDs have been successfully applied for the imaging of ONOO-/GSH in MCF-7 cells.

Synthesis and biological evaluation of 6-nitro-1,2,4-triazoloazines containing polyphenol fragments possessing antioxidant and antiviral activity

Stable σ-adducts of azolo[5,1-c]triazines and azolo[1,5-a]pyrimidines with different polyphenols were synthesized and their antioxidant and antiviral activity were investigated. Their affinity to viral hemagglutinin was assessed using molecular modelling. The phloroglucinol-modified azolo-azines possessed the highest virus-inhibiting activity. According to the results of the study of antioxidant properties of compounds, the most promising ones exhibiting highest antioxidant capacity were adducts containing in their structure pyrogallol and catechol residues and 6-nitro-triazolotriazin-7-ol scaffold. No correlation between antioxidant and virus-inhibiting activity of compounds studied was detected. The most active compounds demonstrated the ability to prevent binding of viral hemagglutinin with cellular receptor as shown in hemagglutination inhibition assay. Our results demonstrate that polyphenol-modified azolo-azines are prospective for further optimization as potential antivirals and that their action is directed against viral hemagglutinin.

Identifying adhesive components in a model tunicate.

Tunicates populate a great variety of marine underwater substrates worldwide and represent a significant concern in marine shipping and aquaculture. Adhesives are secreted from the anterior papillae of their swimming larvae, which attach and metamorphose into permanently adhering, filter-feeding adults. We recently described the cellular composition of the sensory adhesive organ of the model tunicate Ciona intestinalis in great detail. Notably, the adhesive secretions of collocytes accumulate at the tip of the organ and contain glycoproteins. Here, we further explore the components of adhesive secretions and have screened for additional specificities that may influence adhesion or cohesion of the Ciona glue, including other carbohydrate moieties, catechols and substrate properties. We found a distinct set of sugar residues in the glue recognized by specific lectins with little overlap to other known marine adhesives. Surprisingly, we also detect catechol residues that likely originate from an adjacent cellular reservoir, the test cells. Furthermore, we provide information on substrate preferences where hydrophobicity outperforms charge in the attachment. Finally, we can influence the settlement process by the addition of hydrophilic heparin. The further analysis of tunicate adhesive strategies should provide a valuable knowledge source in designing physiological adhesives or green antifoulants. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.

Water‐Dispersible Polydopamine‐Coated Nanofibers for Stimulation of Neuronal Growth and Adhesion

Hybrid nanomaterials have shown great potential in regenerative medicine due to the unique opportunities to customize materials properties for effectively controlling cellular growth. The peptide nanofiber-mediated auto-oxidative polymerization of dopamine, resulting in stable aqueous dispersions of polydopamine-coated peptide hybrid nanofibers, is demonstrated. The catechol residues of the polydopamine coating on the hybrid nanofibers are accessible and provide a platform for introducing functionalities in a pH-responsive polymer analogous reaction, which is demonstrated using a boronic acid modified fluorophore. The resulting hybrid nanofibers exhibit attractive properties in their cellular interactions: they enhance neuronal cell adhesion, nerve fiber growth, and growth cone area, thus providing great potential in regenerative medicine. Furthermore, the facile modification by pH-responsive supramolecular polymer analog reactions allows tailoring the functional properties of the hybrid nanofibers in a reversible fashion.

ModifiedB‐Alkylcatecholboranes as Radical Precursors

AbstractGeneration of radicals fromB‐alkylcatecholboranes represents an efficient tin‐free procedure for the generation of alkyl radicals. A modified version of this method has been developed. The simple catechol is replaced by a dihydroxylated tetrahydroisoquinoline, which can be separated from the reaction products by simple extraction with an aqueous acid solution. The modified alkyl radical precursors are easily prepared from alkenes by hydroboration with BH3·Me2S followed by treatment with the dihydroxytetrahydroisoquinoline. The new alkylboronates of this type are suitable radical precursors in a wide range of reactions such as sulfenylation, allylation, alkynylation, vinylation, and addition to quinones. This strategy is particularly useful when separation of reaction products from catechol residues is problematic, as illustrated by a radical addition to 1,4‐benzoquinone leading to 2‐alkyl‐1,4‐hydroquinones.

Efficient and Practical Protection of the Catechol Residue of 3,4-Dihydroxyphenylalanine (DOPA) Derivative as Acetonide

The acetonide formation of 3,4-dihydroxyphenylalanine (DOPA) derivative was realized under efficient and practical reaction conditions: the reaction of the methyl ester of DOPA in acetone-i-PrOH in the presence of 5 mol% of TsOH afforded the catechol side chain protected DOPA as an acetonide in quantitative yield; the workup procedure is a simple evaporation of the solvents. This methodology allows an access to the reaction in large scale.

Synthesis of tailor-made copolymers containing free or protected catechol residues for selective flocculation of mineral dispersions

pH-Controlled selective polymeric flocculants for titanium mineral dispersions have been designed and prepared through the synthesis of five new vinyl monomers containing catechol residues in free or protected form and through their radical copolymerization with acrylic or methacrylic acid. The synthesis of copolymers with unprotected catechol groups has been studied either by directly copolymerizing unprotected monomers in the presence of tri-n-butylborane or by chemically transforming copolymers obtained from protected monomers.

Iron-regulated outer membrane proteins of Escherichia coli K-12 and mechanism of action of catechol-substituted cephalosporins.

Selected aminothiazolyl-oxime cephalosporin congeners substituted at C-3' with a catechol moiety were used to probe the basis of the enhanced antibacterial activity against Escherichia coli K-12 often associated with chemical modifications of this type. Evidence is presented for a tonB-dependent illicit transport of the compounds across the outer membrane of E. coli K-12, the process involving jointly and specifically the Fiu and Cir iron-regulated outer membrane proteins. Thus, both tonB and fiu cir mutants showed a comparably reduced susceptibility to the probe compounds, whereas mutants singularly lacking any one of the six iron-regulated outer membrane proteins (Fiu, FepA, FecA, FhuA, FhuE, and Cir) or lacking any combination of any two of these proteins (except Fiu plus Cir) did not show this resistance. Mutants devoid of all six iron-regulated outer membrane proteins were no more resistant to the probe compounds than fiu cir or tonB strains. In addition to the latter genes, the products of the exbB and possibly the exbC loci were necessary for maximal antibacterial potency. A dependence of antibacterial activity on the level of expression of the uptake system components was noted. Comparison of penicillin-binding protein target affinity with antibacterial activity suggested a possible periplasmic accumulation of active compounds by E. coli K-12. Free vicinal hydroxyl groups of the catechol residue were a primary chemical requirement for recognition by the uptake pathway and thus for high antibacterial activity.

Solid state structure of a diazadibenzo-30-crown-10 disulphonamide

X-Ray crystallography of compound (2) has revealed the presence of edge- to-face interactions between N-tosyl groups and catechol residues in symmetry-related molecules in the crystalline state.

Toxicity of 5-chloro-3-methyl-catechol to rat: chemical observations and light microscopy of the tissue.

5-chloro-3-methyl-catechol was first time described by GAUNT and EVANS (1961) as a metabolite of MCPA (4-chloro-2-methylphenoxyacetic aci~which is the most widely used herbicide in the Nordic countries. The toxicity of the metabolite 5-chloro-3-methylcatechol bas hot been studied so far. Other catechols like 3,5dichlorocatechol has been shown to be a metabollte of 2,4-D (BOLLAG et ai. 1968a, BOLLAG et ai. 1968b), and it has been proven to be toxic to cells by HORVATH (1971). The catechols are metabolized by bacteria finally to muconic semialdehyde (HORVATH 1970, HORVATH and ALEXANDER 1970). In this work the toxicity of 5-chloro-3-methyl-catechol to maie rats was studied in acute and subchronic experiment in order to relate the histopathological changes in the tissues to the residue levels in the same tissues. A TLC method recently developed by SATTAR et ai. (1977) was used in the clean-up and the quantitative determination of the catechol residues occurred by glass capillary GLC.

The chemistry of the phosphoryl linkage: examples of P IV ? P V and P IV ? P VI transformation under mild conditions

Catechol and substituted catechols react with phosphonic acid or with phosphoryl chloride under mild conditions to give P-spirobis-(o-arylenedioxy)phosphoranes; where the non-cyclic substituent at phosphorus is a catechol residue the phosphoranes are readily transformed by organic bases into corresponding tris-(o-aryl-enedioxy)phosphate anions.

Stereochemie des fünfbindigen Phosphors: Kristallstrukturen von zwei Oxyphosphoranen / Stereochemistry of Five-coordinated Phosphorus: Crystal Structures of Two Oxyphosphoranes

The crystal structures of (C6H4O2)2PR with two chelating catechol residues and R = F (1) and CH3 (2), respectively, at a phosphorus atom were determined. The observed geometry at this atom is between a trigonal bipyramid and a tetragonal pyramid in 1 and close to a tetragonal pyramid in 2. These results are discussed in the light of existing knowledge and theories on five-coordination of phosphorus.

Lignin as an Additive Compound to Storage Batteries I.

The functional group and the reaction mechanism of lignin as a battery additive were studied on a small alkaline storage battery specially prepared. The capacity of battery increased with addition of catechol, guaiacol and many chelating agents such as EDTA, as well as with that of lignin. Demethylation of guaiacol in the electrolytic solution was observed and it was proved that the catechol residue reacts as a functional group of lignin in alkaline storage batteries, which is just the same as in the case of lead storage batteries. A significant increase in Cd+2 ion in electrolytic solution was found with addition of lignin and chelating agents including catechol derivatives, which suggested that the increase in capacity should be connected with the chelating effect of the additives with heavy metalic ions of cathode. The Cd+2 ion increased slightly during discharging process and decreased during charging, but the quantity of electricity transported with the Cd0-Cd+2 transformation was too small to interpret the whole increase in capacity.From the potential-time curves of charge-discharge cycle before and after addition of lignin and chelating agents, it is suggested that lignin makes the grain of cathode active material minute quickly during charging process, resulting in an increase in discharging capacity.Attempt was made to probe the mechanism of capacity increase with lignin both from the chelating effect and adsorption of lignin : Dissolved Cd+2-lignin complex will make the grain of active material minute when it deposites on cathode and dissolution of Cd+2 into electrolytic solution will also cause a minuteness of the grain. Violent adsorption of lignin or Cd+2-lignin complex is expected on the surface of cathode, for lignin has a chelating ability with active material. The transformation of Cd0 to Cd+2 or of its reverse on the cathode surface will occur at the opening of the vigorously adsorbed lignin molecule, resulting in rugged surface of cathode. The increase in surface area caused by minimized active material grain will bring with it also discharging capacity increase.