Dispersant Molecules with Functional Catechol Groups for Supercapacitor Fabrication

Cathodes for supercapacitors with enhanced capacitive performance are prepared using MnO₂ as a charge storage material and carbon nanotubes (CNT) as conductive additives. The enhanced capacitive properties are linked to the beneficial effects of catecholate molecules, such as chlorogenic acid and 3,4,5-trihydroxybenzamide, which are used as co-dispersants for MnO₂ and CNT. The dispersant interactions with MnO₂ and CNT are discussed in relation to the chemical structures of the dispersant molecules and their biomimetic adsorption mechanisms. The dispersant adsorption is a key factor for efficient co-dispersion in ethanol, which facilitated enhanced mixing of the nanostructured components and allowed for improved utilization of charge storage properties of the electrode materials with high active mass of 40 mg cm⁻². Structural peculiarities of the dispersant molecules are discussed, which facilitate dispersion and charging. Capacitive properties are analyzed using cyclic voltammetry, chronopotentiometry and impedance spectroscopy. A capacitance of 6.5 F cm⁻² is achieved at a low electrical resistance. The advanced capacitive properties of the electrodes are linked to the microstructures of the electrodes prepared in the presence of the dispersants.

Mechanical Stabilization of Alginate Hydrogel Fiber and 3D Constructs by Mussel-Inspired Catechol Modification

Alginate is a representative biocompatible natural polymer with low cost for a variety of biomedical applications, such as wound dressing, drug delivery systems, tissue scaffolds, and 3D bioprinting. Particularly, the rapid and facile gelation of alginate via ionic interactions with divalent cations has been used for in situ 3D hydrogel fiber formation, which is potentially applicable to engineering cell alignment. However, challenges in enhancing the mechanical properties of alginate hydrogel fibers under physiological conditions are unresolved because of their fast dissociation by ion exchange. Herein, we report a stabilization strategy for alginate hydrogel fibers through mussel-inspired catechol chemistry, which involves inter-catechol crosslinking within a few minutes under basic conditions. The fabrication of catechol-tethered alginate hydrogel fibers through wet-spinning enabled the design of mechanically strong 3D constructs consisting of fibers. Catechol-to-quinone oxidation followed by covalent crosslinking enhanced the tensile strength of a single fiber. Additionally, the 'gluing' capability of the catechol stabilized the interface among the fibers, thus retaining the shape fidelity of the 3D constructs and encapsulating the cell density during culture. Our findings will be useful for designing bioink materials specialized in fibrous-type tissue scaffolds with mechanical stability.

Chemoenzymatic semisynthesis of caffeic acid β-phenethyl ester, an antioxidative component in propolis, from raw coffee bean extract

Caffeic acid β-phenethyl ester (CAPE), an antioxidative bioactive catechol isolated from propolis, was semisynthesized from chlorogenic acid and related compounds in an extract of raw (unroasted) Robusta coffee (Coffea canephora) beans in 5 steps and a total yield of 31%. Oxidative degradation of the intermediates and target molecule was prevented by alkaline hydrolysis of the chlorogenic acids in the presence of sodium dithionite (Na2S2O4) and deprotection of the catecholic diacetate precursor by Candida antarctica lipase B-mediated transesterification as the final step.

Fast-Curing Mussel-Inspired Adhesive Derived from Vegetable Oil

The development of functional materials based on renewable resources is of great significance in today's resource shortage. Here, we present an effective way to synthesize a mussel-inspired adhesive from acrylated epoxidized soybean oil (AESO), a renewable and commercially available small molecular material with a molecular weight around 1200 Da, by a one-step esterification reaction with the affordable 3,4-dihydroxybenzoic acid (DHA). By taking advantages of both the double bond and the catechol moiety presented in this small molecular adhesive, a short curing time was achieved with UV irradiation. An average bonding strength around 1.4 MPa at a curing time of only around 10 min on a glass substrate was observed, which reached 3.1 MPa (average 2.8 MPa) at a curing time of 2 h under ambient conditions. The curing time is much shorter, and the bonding strength is obviously stronger than the conditions where conventional oxidation agents such as IO₄^- or oxidation/coordination agents such as Fe³⁺ are used as the curing agent. Furthermore, the AESO-g-DHA can be used as an underwater adhesive, and an appreciable bonding strength up to 0.64 MPa was observed, which is superior than most of currently known commercialized glues. Given that the adhesive could be synthesized from low-cost renewable resources in one step, it might be a potential candidate for large-scale practical application.

Silver Nanowires as Electron Transfer Mediators in Electrochemical Catechol Biosensors

The integration of nanomaterials as electron mediators in electrochemical biosensors is taking on an essential role. Due to their high surface-to-volume ratio and high conductivity, metallic nanowires are an interesting option. In this paper, silver nanowires (AgNWs) were exploited to design a novel catechol electrochemical biosensor, and the benefits of increasing the aspect ratio of the electron mediator (nanowires vs. nanoparticles) were analyzed. Atomic force microscopy (AFM) studies have shown a homogeneous distribution of the enzyme along the silver nanowires, maximizing the contact surface. The large contact area promotes electron transfer between the enzyme and the electrode surface, resulting in a Limit of Detection (LOD) of 2.7 × 10⁻⁶ M for tyrosinase immobilized onto AgNWs (AgNWs-Tyr), which is one order of magnitude lower than the LOD of 3.2 × 10⁻⁵ M) obtained using tyrosinase immobilized onto silver nanoparticles (AgNPs-Tyr). The calculated K_M constant was 122 mM. The simultaneous use of electrochemistry and AFM has demonstrated a limited electrochemical fouling that facilitates stable and reproducible detection. Finally, the biosensor showed excellent anti-interference characteristics toward the main phenols present in wines including vanillin, pyrogallol, quercetin and catechin. The biosensor was able to successfully detect the presence of catechol in real wine samples. These results make AgNWs promising elements in nanowired biosensors for the sensitive, stable and rapid voltammetric detection of phenols in real applications.

Catechol-Based Antimicrobial Polymers

Catechol is a key constituent in mussel adhesive proteins and is responsible for strong adhesive property and crosslinking formation. Plant-based polyphenols are also capable of chemical interactions similar to those of catechol and are inherently antimicrobial. This review reports a series of catechol-based antimicrobial polymers classified according to their antimicrobial mechanisms. Catechol is utilized as a surface anchoring group for adhering monomers and polymers of known antimicrobial properties onto various types of surfaces. Additionally, catechol's ability to form strong complexes with metal ions and nanoparticles was utilized to sequester these antimicrobial agents into coatings and polymer matrices. During catechol oxidation, reactive oxygen species (ROS) is generated as a byproduct, and the use of the generated ROS for antimicrobial applications was also introduced. Finally, polymers that utilized the innate antimicrobial property of halogenated catechols and polyphenols were reviewed.

Catechol enhances chemo‑ and radio‑sensitivity by targeting AMPK/Hippo signaling in pancreatic cancer cells

Overcoming chemo‑ and radio‑resistance is a major challenge in pancreatic cancer treatment. Therefore, there is an urgent need to discover novel therapeutic approaches to avoid chemo‑ and radio‑resistance in pancreatic cancer. Catechol is a phytochemical found in some fruits and vegetables. A few studies have reported on the potential anticancer effects of pure catechol. The present study aimed to explore the chemo‑ and radio‑sensitizing effects of catechol in Panc‑1 human pancreatic cancer cells. The effects of catechol on Panc‑1 cell proliferation, clonogenic survival, invasion, and migration were assessed using MTT, cell migration, and Transwell invasion assays. The chemo‑ and radio‑sensitizing effects of catechol on Panc‑1 cells were evaluated via MTT assay and flow cytometry. Western blotting was conducted to analyze the expression of proteins involved in several mechanisms induced by catechol in Panc‑1 cells, including growth inhibition, apoptosis, suppression of epithelial‑mesenchymal transition (EMT), and chemo‑ and radio‑sensitizing activities. The results indicated that catechol inhibited proliferation, promoted apoptosis, and suppressed cell migration, invasion, and EMT in Panc‑1 cells in a dose‑dependent manner. Catechol treatment also induced the phosphorylation of AMP‑activated protein kinase (AMPK) with a concomitant reduction in the expression of Hippo signaling pathway components, including Yes‑associated protein, cysteine‑rich angiogenic inducer 61, and connective tissue growth factor. In addition, catechol enhanced the chemosensitivity of Panc‑1 cells to gemcitabine, a commonly used chemotherapy in pancreatic cancer treatment. A combination of catechol and radiation enhanced apoptosis and increased the expression of two radiation‑induced DNA damage markers, p‑ATM and p‑Chk2. Collectively, the present results demonstrated that catechol, a naturally occurring compound, could suppress the proliferation of pancreatic cancer cells, reduce the expression of EMT‑related proteins, and enhance the chemo‑ and radio‑sensitivity of Panc‑1 cells by targeting AMPK/Hippo signaling.

Effects of Chemically-Modified Polypyridyl Ligands on the Structural and Redox Properties of Tricarbonylmanganese(I) Complexes

Carbonyl complexes with manganese(I) as the central metal are very attractive catalysts. The introduction of redox-active ligands, such as quinones and methyl viologen analogs into these catalysts, would be expected to lead to superior catalyst performances, since they can function as excellent electron carriers. In this study, we synthesized four tricarbonylmanganese(I) complexes containing typical bidentate polypyridyl ligands, including 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) frameworks bound to redox-active ortho-quinone/catechol or methyl viologen-like units. The molecular structures of the resulting complexes were determined by X-ray crystallography to clarify their steric features. As expected from the infrared (IR) data, three CO ligands for each complex were coordinated in the facial configuration around the central manganese(I) atom. Additionally, the structural parameters were found to differ significantly between the quinone/catechol units. Electrochemical analysis revealed some differences between them and their reference complexes, namely [MnBr(CO)₃(phen)] and [MnBr(CO)₃(bpy)]. Notably, interconversions induced by two-electron/two-proton transfers between the quinone and catechol units were observed in the phenanthroline-based complexes. This work indicated that the structural and redox properties in tricarbonylmanganese(I) complexes were significantly affected by chemically modified polypyridyl ligands. A better understanding of structures and redox behaviors of the present compounds would facilitate the design of new manganese complexes with enhanced properties.

Natural compound catechol induces DNA damage, apoptosis, and G1 cell cycle arrest in breast cancer cells

Targeting cell cycle and inducing DNA damage by activating cell death pathways are considered as effective therapeutic strategy for combating breast cancer progression. Many of the naturally known small molecules target these signaling pathways and are effective against resistant and/or aggressive types of breast cancers. Here, we investigated the effect of catechol, a naturally occurring plant compound, for its specificity and chemotherapeutic efficacies in breast cancer (MCF-7 and MDA-MB-231) cells. Catechol treatment showed concentration-dependent cytotoxicity and antiproliferative growth in both MCF-7 and MDA-MB-231 cells while sparing minimal effects on noncancerous (F-180 and HK2) cells. Catechol modulated differential DNA damage effects by activating ATM/ATR pathways and showed enhanced γ-H2AX expression, as an indicator for DNA double-stranded breaks. MCF-7 cells showed G1 cell cycle arrest by regulating p21-mediated cyclin E/Cdk2 inhibition. Furthermore, activation of p53 triggered a caspase-mediated cell death mechanism by inhibiting regulatory proteins such as DNMT1, p-BRCA1, MCL-1, and PDCD6 with an increased Bax/Bcl-2 ratio. Overall, our results showed that catechol possesses favorable safety profile for noncancerous cells while specifically targeting multiple signaling cascades to inhibit proliferation in breast cancer cells.

Inhibitory Effect of Lithospermic Acid on the HIV-1 Nucleocapsid Protein

The HIV-1 nucleocapsid protein (NC) is a desirable target in antiretroviral therapy due to its high conservation among HIV-1 strains, and to its multiple and crucial roles in the HIV-1 replication cycle. Natural products represent a valuable source of NC inhibitors, with the catechol group being a privileged scaffold in NC inhibition. By coupling molecular modeling with NMR spectroscopy and fluorescence-based assays, we disclosed lithospermic acid, a catechol derivative extracted from Salvia miltiorrhizza, as a potent and chemically stable non-covalent inhibitor of the NC. Being different from other catechol derivative reported so far, lithospermic acid does not undergo spontaneous oxidation in physiological conditions, thus becoming a profitable starting point for the development of efficient NC inhibitors.

Integrated Experimental and Theoretical Studies on an Electrochemical Immunosensor

Electrochemical immunosensors (EIs) integrate biorecognition molecules (e.g., antibodies) with redox enzymes (e.g., horseradish peroxidase) to combine the advantages of immunoassays (high sensitivity and selectivity) with those of electrochemical biosensors (quantitative electrical signal). However, the complex network of mass-transfer, catalysis, and electrochemical reaction steps that produce the electrical signal makes the design and optimization of EI systems challenging. This paper presents an integrated experimental and modeling framework to address this challenge. The framework includes (1) a mechanistic mathematical model that describes the rate of key mass-transfer and reaction steps; (2) a statistical-design-of-experiments study to optimize operating conditions and validate the mechanistic model; and (3) a novel dimensional analysis to assess the degree to which individual mass-transfer and reaction steps limit the EI's signal amplitude and sensitivity. The validated mechanistic model was able to predict the effect of four independent variables (working electrode overpotential, pH, and concentrations of catechol and hydrogen peroxide) on the EI's signal magnitude. The model was then used to calculate dimensionless groups, including Damkohler numbers, novel current-control coefficients, and sensitivity-control coefficients that indicated the extent to which the individual mass-transfer or reaction steps limited the EI's signal amplitude and sensitivity.

Solid-Phase Synthesis and In-Silico Analysis of Iron-Binding Catecholato Chelators

Siderophores are iron-complexing compounds synthesized by bacteria and fungi. They are low molecular weight compounds (500-1500 Daltons) possessing high affinity for iron(III). Since 1970 a large number of siderophores have been characterized, the majority using hydroxamate or catecholate as functional groups. The biosynthesis of siderophores is typically regulated by the iron levels of the environment where the organism is located. Because of their exclusive affinity and specificity for iron(III), natural siderophores and their synthetic derivatives have been exploited in the treatment of human iron-overload diseases, as both diagnostic and therapeutic agents. Here, solid-phase approach for the preparation of hexadentate, peptide-based tricatecholato containing peptides is described. The versatility of the synthetic method allows for the design of a common scaffolding structure whereby diverse ligands can be conjugated. With so many possibilities, a computational approach has been developed which will facilitate the identification of those peptides which are capable of providing a high affinity iron(III) binding site. This study reports an integrated computational/synthetic approach towards a rational development of peptide-based siderophores.

Catechol protects against iron-mediated oxidative brain injury by restoring antioxidative metabolic pathways; and modulation of purinergic and cholinergic enzymes activities

OBJECTIVES

This study was aimed at investigating neuroprotective effect of catechol on redox imbalance, cholinergic dysfunctions, nucleotide hydrolysing enzymes activities, and dysregulated metabolic pathways in iron-mediated oxidative brain injury.

METHODS

Oxidative injury was induced in brain tissues by incubating with 0.1 mm FeSO₄ and treated with different concentrations of catechol.

KEY FINDINGS

Catechol significantly elevated glutathione level, superoxide dismutase and catalase activities, while depleting malondialdehyde and nitric oxide levels. It also inhibited the activities of acetylcholinesterase, butyrylcholinesterase, and ATPase, with concomitant elevation of ENTPDase activity. GC-MS analysis revealed that treatment with catechol completely depleted oxidative-generated lipid metabolites. While LC-MS analysis revealed depletion of oxidative-generated metabolites in brain tissues treated with catechol, with concomitant restoration of oxidative-depleted metabolites. Catechol also led to reactivation of oxidative-inactivated taurine and hypotaurine, purine, glutathione, glycerophospholipid, nicotinate and nicotinamide, fructose and mannose, pyrimidine metabolisms and pentose phosphate pathways. Catechol was predicted in silico to be permeable across the blood-brain barrier with a predicted oral LD₅₀ value of 100 mg/kg and a toxicity class of 3.

CONCLUSION

These results suggest the neuroprotective effects of catechol in iron-mediated oxidative brain injury.

Polydopamine Surface Coating Synergizes the Antimicrobial Activity of Silver Nanoparticles

Metal nanoparticles, especially silver nanoparticles (AgNPs), have drawn increasing attention for antimicrobial applications. Most studies have emphasized on the correlations between the antibacterial potency of AgNPs and the kinetics of metallic to ionic Ag conversion, while other antimicrobial mechanisms have been underestimated. In this work, we focused on the surface effects of polydopamine (PDA) coating on the antimicrobial activity of AgNPs. A method of fast deposition of PDA was used to synthesize the PDA-AgNPs with controllable coating thickness ranging from 3 to 25 nm. The antimicrobial activities of the PDA-AgNPs were analyzed by fluorescence-based growth curve assays on Escherichia coli. The results indicated that the PDA-AgNPs exhibited significantly higher antibacterial activities than poly(vinylpyrrolidone)-passivated AgNPs (PVP-AgNPs) and PDA themselves. It was found that the PDA coating synergized with the AgNPs to prominently enhance the potency of the PDA-AgNPs against bacteria. The analysis of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy elucidated that the synergistic effects could be originated from the interaction/coordination between Ag and catechol group on the PDA coating. The synergistic effects led to increased generation of reactive oxygen species and the consequent bacterial damage. These findings demonstrated the importance of the surface effects on the antimicrobial properties of AgNPs. The underlying molecular mechanisms have shined light on the future development of more potent metal nanoparticle-based antimicrobial agents.

Catechol Containing Polyelectrolyte Complex Nanoparticles as Local Drug Delivery System for Bortezomib at Bone Substitute Materials

The proteasome inhibitor bortezomib (BZM) is one of the most potent anti-cancer drugs in the therapy of multiple myeloma. In this study, an adhesive drug delivery system (DDS) for BZM was developed. Therefore, we extended the present DDS concept of polyelectrolyte complex (PEC) nanoparticle (NP) based on electrostatic interactions between charged drug and polyelectrolyte (PEL) to a DDS concept involving covalent bonding between PEL and uncharged drugs. For this purpose, 3,4-dihydroxyphenyl acetic acid (DOPAC) was polymerized via an oxidatively induced coupling reaction. This novel chemo-reactive polyanion PDOPAC is able to temporarily bind boronic acid groups of BZM via its catechol groups, through esterification. PDOPAC was admixed to poly(l-glutamic acid) (PLG) and poly(l-lysine) (PLL) forming a redispersible PEC NP system after centrifugation, which is advantageous for further colloid and BZM loading processing. It was found that the loading capacity (LC) strongly depends on the PDOPAC and catechol content in the PEC NP. Furthermore, the type of loading and the net charge of the PEC NP affect LC and the residual content (RC) after release. Release experiments of PDOPAC/PEC coatings were performed at medically relevant bone substitute materials (calcium phosphate cement and titanium niobium alloy) whereby the DDS worked independently of the surface properties. Additionally, in contrast to electrostatically based drug loading the release behavior of covalently bound, uncharged BZM is independent of the ionic strength (salt content) in the release medium.

The Pneumococcal Iron Uptake Protein A (PiuA) Specifically Recognizes Tetradentate FeIIIbis- and Mono-Catechol Complexes

Streptococcus pneumoniae (Spn) is an important Gram-positive human pathogen that causes millions of infections worldwide with an increasing occurrence of antibiotic resistance. Fe acquisition is a crucial virulence determinant in Spn; further, Spn relies on exogenous Fe^III-siderophore scavenging to meet nutritional Fe needs. Recent studies suggest that the human catecholamine stress hormone, norepinephrine (NE), facilitates Fe acquisition in Spn under conditions of transferrin-mediated Fe starvation. Here we show that the solute binding lipoprotein PiuA from the piu Fe acquisition ABC transporter PiuBCDA, previously described as an Fe-hemin binding protein, binds tetradentate catechol Fe^III complexes, including NE and the hydrolysis products of enterobactin. Two protein-derived ligands (H238, Y300) create a coordinately saturated Fe^III complex, which parallel recent studies in the Gram-negative intestinal pathogen Campylobacter jejuni. Our in vitro studies using NMR spectroscopy and ⁵⁴Fe LC-ICP-MS confirm the Fe^III can move from transferrin to apo-PiuA in an NE-dependent manner. Structural analysis of PiuA Fe^III-bis-catechol and Ga^III-bis-catechol and Ga^III-(NE)₂ complexes by NMR spectroscopy reveals only localized structural perturbations in PiuA upon ligand binding, largely consistent with recent descriptions of other solute binding proteins of type II ABC transporters. We speculate that tetradentate Fe^III complexes formed by mono- and bis-catechol species are important Fe sources in Gram-positive human pathogens, since PiuA functions in the same way as SstD from Staphylococcus aureus.

Linear Coordination Polymer Synthesis from Bis-Catechol Functionalized RAFT Polymers

Catechol-Fe(III) complexes contain some of the strongest known metal-chelate coordination bonds. Despite this, they have until now not been utilized in (polymeric linker) linear coordination polymer (LCP) synthesis. With the view of generating catechol end-functional polymers, a new, symmetrical bis-catechol functionalized trithiocarbonate reversible addition fragmentation chain transfer (RAFT) agent is synthesized (CatDMAT). Acrylamide (AM) and dimethylacrylamide (DMA) polymerizations are conducted with CatDMAT using direct photoactivation RAFT polymerization to yield bis-catechol end-functionalized homo- and block-copolymers of molecular weight 10-15 kDa. Catechol-Fe(III) LCPs are successfully formed from the telechelic catechol polymers by bis-complexation to Fe(III). The tetrahedral bis-complex is detected by UV-vis spectroscopy (λ_max  = 570 nm), while increases in relative viscosity and M_n,GPC over their respective uncomplexed polymers confirm the occurrence of supramolecular polymerization. The catechol-LCPs are shown to undergo oxidation and crosslinking in aqueous solution after 24 h.

Catechol-Functionalized Alginate Nanoparticles as Mucoadhesive Carriers for Intravesical Chemotherapy

This research aimed to synthesize and evaluate mucoadhesive catechol-functionalized alginate (Cat-Alg) nanoparticles (NPs) for bladder cancer. Cat-Alg was synthesized using coupling chemistry, and the structure was verified using NMR and FT-IR. Cat-Alg NPs were generated by ionic gelation between the synthesized Cat-Alg and calcium chloride. Garcinia mangostana L. extract (GM extract) was entrapped into the NPs during particle formation. The physical characteristics, mucoadhesive properties, drug loading and release, cellular uptake, and anticancer activity of the GM extract-loaded NPs were investigated. The Cat-Alg NPs were spherical with sizes in the range of 155-186 nm. The slightly negative surface charge of the NPs provided them with excellent stability. The Cat-Alg NPs could be retained on a porcine bladder mucosa to a greater extent compared with unmodified Alg NPs. High loading efficiency (71.6%) and loading capacity (292 μg/mg) of GM extract in the NPs were achieved, and a constant release of GM extract was obtained for up to 8 h with zero-order kinetics. Moreover, the GM extract-loaded NPs were deposited in bladder tissue and accumulated in MB49 cells at a higher rate compared with GM extract suspension. In addition, the NPs could kill a mouse urothelial carcinoma cell line with low IC₅₀. Therefore, these NPs have the potential to be a mucoadhesive drug delivery system for bladder cancer treatment. However, additional in vivo investigations are needed for clinical application in cancer treatment. Graphical abstract.

New Mussel Inspired Polydopamine-Like Silica-Based Material for Dye Adsorption

A straightforward and economic procedure has been developed for the synthesis of a new polydopamine-like silica-based material that has been obtained by oxidation of catechol with KIO4 followed by reaction with 3-aminopropyltrimethoxysilane. All techniques adopted for characterization showed that the obtained material is rich in different functional groups and the morphological analyses revealed dimensions in the nanometric range. The hybrid material has been characterized by several techniques showing its polydopamine-like nature, and preliminary observations for dye adsorption have been reported.

Electrochemical Oxidation of Metal-Catechol Complexes as a New Synthesis Route to the High-Quality Ternary Photoelectrodes: A Case Study of Fe2TiO5 Photoanodes

A new electrochemical, solution-based synthesis method to prepare uniform multinary oxide photoelectrodes was developed. This method involves solubilizing multiple metal ions as metal-catechol complexes in a pH condition where they are otherwise insoluble. When some of the catechol ligands are electrochemically oxidized, the remaining metal complexes become insoluble and are deposited as metal-catechol films on the working electrode. The resulting films are then annealed to form crystalline multinary oxide electrodes. Because catechol can serve as a complexing agent for a variety of metal ions, the newly developed method can be used to prepare a variety of multinary oxide films. In the present study, we used this method to prepare n-type Fe₂TiO₅ photoanodes and investigated their photoelectrochemical properties for use in a photoelectrochemical water-splitting cell. We also performed a computational investigation with two goals. The first goal was to investigate small electron polaron formation in Fe₂TiO₅. Charge transport in most oxide photoelectrodes involves small polaron hopping, but small polaron formation in Fe₂TiO₅ has not been examined prior to this work. The second goal was to investigate the effect of substitutional Sn doping at the Fe site on the electronic band structure and the carrier concentration of Fe₂TiO₅. The combined experimental and theoretical results presented in this study greatly improve our understanding of Fe₂TiO₅ for use as a photoanode.

pH-Triggered Adhesiveness and Cohesiveness of Chondroitin Sulfate-Catechol Biopolymer for Biomedical Applications

Nature provides biomaterials that tend to be effective to control both their adhesive and cohesive properties. A catecholamine motif found in the marine mussels, the mytilus edulis foot protein, can play adhesiveness and cohesiveness. Particularly, acidic pH drives catechol (Cat) to have adhesive function, resulting in surface coating, while basic pH allows to enhance its cohesive properties, resulting in the formation of hydrogels. In this work, we demonstrated the usefulness of Cat-conjugated chondroitin sulfate (CS) as a platform for mesenchymal stem cell culture, utilizing the adhesive property of CS-Cat as coating for different substrates and the cohesive properties as hydrogel for cells encapsulation. To prepare the CS-Cat biopolymer, dopamine (DP) was coupled to the CS by carbodiimide coupling reaction and the Cat content was determined by UV-Vis spectroscopy (4.8 ± 0.6%). To demonstrate the adhesive properties of the biopolymer, PLA, PCL, TiO₂, and SiO₂ substrates were immersed in CS-Cat solution (pH < 2). Following the coating, the surfaces became highly hydrophilic, exhibiting a contact angle less than 35°. Also, in the presence of an oxidizing agent at pH 8, CS-Cat solution immediately became a hydrogel, as shown by inverted-vial test. Finally, immortalized TERT human mesenchymal stem cells (Y201) confirmed the high cytocompatibility of the biopolymer. The CS-Cat coating significantly enabled the Y201 adhesion onto PLA substrates, while the prepared hydrogel demonstrated to be a suitable environment for the encapsulation of cells as suitable bioink for further bioprinting applications.

Controlling the Release of Hydrogen Peroxide from Catechol-Based Adhesive Using Silica Nanoparticle

Catechol-based bioadhesives generate hydrogen peroxide (H₂O₂) as a byproduct during the curing process. H₂O₂ can have both beneficial and deleterious effects on biological systems depending on its concentration. To control the amount of H₂O₂ released from catechol-containing polyethylene glycol-based adhesive (PEG-DA), adhesive was formulated with silica nanoparticles (SiNP) prepared with increased porosity and acid treatment to increase Si-OH surface content. These SiNP demonstrated increased surface area, which promoted interaction with catechol and resulted in increased cure rate, bulk mechanical properties and adhesive properties of PEG-DA. Most importantly, SiNP demonstrated a 50% reduction in the released H₂O₂ while improving the cell viability and proliferation of three primary cell types, including rat dermal fibroblasts, human epidermal keratinocytes, and human tenocytes. Additionally, SiNP degraded into soluble Si, which also contributed to increased cell proliferation. Incorporation of porous and acid-treated SiNP can be a useful approach to simultaneously modulate the concentration of H₂O₂ while increasing the adhesive performance of catechol-based adhesives.

Iron Magnetic Nanoparticle-Induced ROS Generation from Catechol-Containing Microgel for Environmental and Biomedical Applications

Reactive oxygen species (ROS) can degrade organic compounds and function as a broad-spectrum disinfectant. Here, dopamine methacrylamide (DMA) was used to prepare catechol-containing microgels, which can release ROS via metal-catechol interaction. A combination of the microgel and iron magnetic nanoparticle (FeMNP) significantly reduced the concentration of four organic dyes (Alizarin Red S, Rhodamine B, Crystal Violet, and Malachite Green) and an antibiotic drug, ciprofloxacin, dissolved in solution. Degradation of dye occurred across a wide range of pH levels (pH 3-9). This simple combination was also antimicrobial against both Escherichia coli and Staphylococcus aureus. Electron paramagnetic resonance spectroscopy (EPR) results indicate that singlet oxygen was generated during the reaction between catechol and FeMNP at both pH 3 and 7.4, which was responsible for the degradation of organic compounds and bactericidal features of the microgel. Unlike autoxidation that only occurs at a neutral to basic pH, FeMNP-induced catechol oxidation generated singlet oxygen over a wide range of pH level. Additionally, catechol chelates heavy metal ions, resulting in their removal from solution and repurposed these metal ions for dye degradation. This multifunctional microgel can potentially be used for environmental applications for the removal of organic pollutants and heavy metal ions from wastewater, as well as reducing bacterial infection in biomedical applications.

Catechol-bearing imidazolium and benzimidazolium chlorides as promising antimicrobial agents

Catechol-containing imidazolium (four) and benzimidazolium chlorides (eight) were synthesized to evaluate their antimicrobial properties. All the compounds were fully characterized using ¹ H and ¹³ C nuclear magnetic resonance, liquid chromatography-mass spectrometry, infrared spectroscopic methods, and elemental analyses. Antimicrobial activities of the compounds were tested against the bacteria Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Enterococcus faecalis, and the fungal strains Candida albicans and Candida glabrata, and promising results were achieved. The two most important benzyl-substituted benzimidazolium chlorides, 3l and 3k, showed comparable activity to vancomycin against MRSA.

Mussel-Inspired Alternating Copolymer as a High-Performance Adhesive Material Both at Dry and Under-Seawater Conditions

Marine mussels have the ability to cling to various surfaces at wet or underwater conditions, which inspires the research of catechol-functionalized polymers (CFPs) to develop high-performance adhesive materials. However, these polymeric adhesives generally face the problems of complex synthetic route, and it is still high challenging to prepare CFPs with excellent adhesive performance both at dry and underwater conditions. Herein, a mussel-inspired alternating copolymer, poly(dopamine-alt-2,2-bis(4-glycidyloxyphenyl)propane) (P(DA-a-BGOP)), is synthesized in one step by using commercially available monomers through epoxy-amino click chemistry. The incorporation of polar groups and rigid bisphenol A structures into the polymer backbone enhances the cohesion energy of polymer matrix. The alternating polymer structure endows the polymers with high catechol content and controlled polymer sequence. As a result, P(DA-a-BGOP) exhibits a strong bonding strength as high as 16.39 ± 2.13 MPa on stainless steel substrates after a hot pressing procedure and displays a bonding strength of 1.05 ± 0.05 MPa on glass substrates at an under-seawater condition, which surpasses most commercial adhesives.