Pendant Carboxyl Research Articles

Towards scarless repair: MMP-2 responsive drug releasing nanofibrous mat restores homeostasis via fibroblasts’ activation

The failure of wound repair, particularly in cases of refractory wounds, is closely associated with immune disorders, leading to serious consequences such as scarring and ulcers. To address this issue, Poly [octanediol-co- (citric acid)] (POCA)/gelatin curcumin-loaded nanofibrous mats responsive to inflammatory microenvironments are developed. POCA serves as a cross-linker for gelatin, providing the nanofibrous mat with skin-like J-shaped stress-strain behavior. Moreover, the pendant carboxyl groups of POCA enable adhesion ability in the wet state, thereby increasing wound sealing. Most importantly, the as-prepared nanofibers are sensitive to MMP-2. Amorphous curcumin is responsively released in response to high MMP levels present in inflammatory wounds. This significantly enhances curcumin's efficiency. The mat exhibits substantial therapeutic effects on chronic diabetic wounds and tension-loaded wounds, nudging wound healing toward regenerative repair. Moreover, it was also shown to promote basement membrane renewal by activating wound fibroblasts, which mitigates the immune response and reinstate homeostasis.

Vitrimer-like elastomers with rapid stress-relaxation by high-speed carboxy exchange through conjugate substitution reaction

We report vitrimer-like elastomers that exhibit significantly fast stress relaxation using carboxy exchange via the conjugate substitution reaction of α-(acyloxymethyl) acrylate skeletons. This network design is inspired by a small-molecule model that shows the carboxy exchange reaction even at ambient temperature in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO). The acrylate and acrylic acid copolymers are cross-linked using bis[α-(bromomethyl)acrylates] and doped with 10 wt% DABCO, exhibiting processability to obtain a transparent film by hot pressing. The high-speed bond exchange in the network, validated by stress-relaxation tests, allows quick molding with household iron. In addition, the material is applied as an adhesion sheet for plastic and metal substrates. Because dynamic cross-linking with the proposed bond exchange mechanism can be implemented for any polymer bearing carboxyl pendants, our approach can be applied to versatile backbones, which must thus be meaningful in the practical sense.

Thermosensitive Hydrogel with Programmable, Self-Regulated HIF-1α Stabilizer Release for Myocardial Infarction Treatment.

HIF-1α (hypoxia induced factor-1α), a vital protective signal against hypoxia, has a short lifetime after myocardial infarction (MI). Increasing HIF-1α stability by inhibiting its hydroxylation with prolyl hydroxylases inhibitors such as DPCA (1,4-dihydrophenonthrolin-4-one-3-carboxylic acid) presents positive results. However, the optimal inhibitor administration profile for MI treatment is still unexplored. Here, injectable, thermosensitive hydrogels with programmable DPCA release are designed and synthesized. Hydrogel degradation and slow DPCA release are coupled to form a feedback loop by attaching pendant DPCA to polymer backbone, which serve as additional crosslinking points through π-π and hydrophobic interactions. Pendant carboxyl groups are added to the copolymer to accelerate DPCA release. Burst release in the acute phase for myocardial protection and extended near zero-order release across the inflammatory and fibrotic phases with different rates are achieved. All DPCA-releasing hydrogels upregulate HIF-1α, decrease apoptosis, promote angiogenesis, and stimulate cardiomyocyte proliferation, leading to preserved cardiac function and ventricular geometry. Faster hydrogel degradation induced by faster DPCA release results in a HIF-1α expression eight times of healthy control and better therapeutic effect in MI treatment. This research demonstrates the value of precise regulation of HIF-1α expression in treating MI and other relevant diseases and provides an implantable device-based modulation strategy.

H3trica: Versatile Macrocyclic Chelator for [225Ac]Ac3+ and [155/161Tb]Tb3+ Theranostics.

H3trica is a nonadentate chelating ligand intended for coordinating large radiometal ions, such as those used in nuclear medicine. This chelator, featuring a triaza-18-crown-6 macrocycle with three pendant carboxylic acid functional groups, was synthesized and characterized. Complementary nuclear magnetic resonance (NMR) spectroscopy and high-resolution electrospray-ionization mass spectroscopy (HR-ESI-MS) studies were used to explore the coordination of H3trica with metal ions such as La3+, Y3+ (as a model for Tb3+), and Lu3+ at the bulk scale. Thermodynamic solution studies provided valuable insights, highlighting robust metal complexation of H3trica with La3+, Tb3+, and Lu3+, with the most noteworthy log KML value observed for Tb3+ (log KTbL = 17.08), followed by La3+ (log KLaL = 16.64) and Lu3+ (log KLuL = 16.25). Concentration-dependent radiolabeling studies with [225Ac]Ac3+, [155Tb]Tb3+, and [161Tb]Tb3+ demonstrated rapid complexation (5-30 min) under mild conditions (pH 6-7, 25 °C). Importantly, the radiolabeled complexes exhibited stability during incubation in human serum for one-half-life of the corresponding radiometal. Thus, H3trica emerges as a valuable chelator, demonstrating its potential to coordinate the theranostic couple [225Ac]Ac3+/[155Tb]Tb3+ as well as the powerful terbium quartet ([149/152/155/161Tb]Tb3+) with efficiency and stability.

Position Matters: Pyridine Regioisomers Influence Secondary Structure and Micelle Morphology in Polymer-Homopolypeptide Micelles.

Polymer-homopolypeptide block copolymers are a class of bioinspired materials that combine the processability and stability of synthetic polymers with the biocompatibility and unique secondary structures of peptides, such as α-helices and β-sheets. These properties make them ideal candidates for a wide variety of applications, for example, in the pharmaceutical field, where they are frequently explored as building blocks for polymeric micelle drug delivery systems. While homopolypeptide side chains can be furnished with an array of different moieties to impart the copolymers with desirable properties, such as stimulus responsivity, pyridine derivatives represent an underutilized functional group for this purpose. Additionally, the interplay between polypeptide side chain structure, secondary conformation, and micelle morphology is not yet well understood, particularly in the case of structural regioisomers. Therefore, in this work, a series of polymer-homopolypeptide copolymers were prepared from a poly(ethylene glycol)-b-poly(glutamic acid) (PEG-b-PGA) backbone, where the pendant carboxylic acid groups were covalently conjugated to a series of pyridine regioisomers by carbodiimide coupling. These pyridine regioisomers differed only in the position of the nitrogen heteroatom, ortho, meta or para, relative to the linking group, generating a series of PEG-b-poly(pyridinylmethyl glutamate) (PEG-b-PMG) copolymers. Following self-assembly of the copolymers in aqueous solutions, dynamic light scattering (DLS) revealed differences in micelle hydrodynamic diameter (Dh) (ranging from ∼60 to 120 nm), while transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) revealed distinctive morphologies ranging from ellipsoidal, to cylindrical, and disc-like, suggesting that subtle changes in positional isomers in the polypeptide block may influence the micelle structure. Analysis of the PEG-b-PMG copolymer micelles by circular dichroism (CD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy revealed that differences in the morphology were associated with changes in polypeptide secondary structure, which in turn was influenced by the position of the pyridine heteroatom. Overall, these findings contribute to the broader understanding of the relationship between polypeptide structure and micelle morphology and serve as useful insight for the rational design of polymer-polypeptide nanoparticles.

Incorporation of Carboxylate Pendant Arms into 18-Membered Macrocycles: Effects on [nat/203Pb]Pb(II) Complexation.

We present a detailed investigation on the coordination chemistry of [nat/203Pb]Pb(II) with chelators H4PYTA and H4CHX-PYTA. These chelators belong to the family of ligands derived from the 18-membered macrocyclic backbone PYAN and present varying degrees of rigidity due to the presence of either ethyl or cyclohexyl spacers. A complete study of the stable Pb(II) complexes is carried out via NMR, X-Ray crystallography, stability constant determination and computational studies. While these studies indicated that Pb(II) complexation is achieved, and the thermodynamic stability of the resulting complexes is very high, a certain degree of fluxionality does exist in both cases. Nevertheless, radiolabeling studies were carried out using SPECT (single photon emission computed tomography) compatible isotope lead-203 (203Pb, t1/2=51.9 h), and while both chelators complex the radioisotope, the incorporation of carboxylate pendant arms appears to be detrimental towards the stability of the complexes when compared to the previously described amide analogues. Additionally, incorporation of a cyclohexyl spacer does not improve the kinetic inertness of the system.

Carboxylated Nanoparticle Surfaces Enhance Association with Mucoid Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa biofilms comprise three main polysaccharides: alginate, psl, and pel, which all imbue tolerance against exogenous antimicrobials. Nanoparticles (NPs) are an exciting new strategy to overcome the biofilm matrix for therapeutic delivery applications; however, zero existing FDA approvals for biofilm-specific NP formulations can be attributed to the complex interplay of physiochemical forces at the biofilm-NP interface. Here, we leverage a set of inducible, polysaccharide-specific, expressing isogenic P. aeruginosa mutants coupled with an assembled layer-by-layer NP (LbL NP) panel to characterize biofilm-NP interactions. When investigating these interactions using confocal microscopy, alginate-layered NPs associated more than dextran-sulfate-layered NPs with biofilms that had increased alginate production, including biofilms produced by mucoid P. aeruginosa isolates from people with cystic fibrosis. These differences were further confirmed in LbL NPs layered with polysaccharide- or hydrocarbon-based polymers with pendent carboxylate or sulfate functional groups. These data suggest carboxylated NP surfaces have enhanced interactions specifically with mucoid biofilms as compared to sulfated surfaces and lay the foundation for their inclusion as a design element for increasing biofilm-NP interactions and efficacious drug delivery.

Electroreductive Decomplexation and Isomerism of Copper(II) Complexes with Cyclam Ligands for Medical Use

AbstractDetailed electrochemical study of copper(II) complexes of cyclam bearing two phosphonate (TE2P), phenolate (TE2PhOH) or carboxylate (TE2A) pendant arms (together with one cross‐bridged‐cyclam derivative cb‐TE2A) was performed using cyclic voltammetry (CV) and polarography. The electrochemical‐heterogeneous measurements were accompanied by UV‐vis spectra describing the situation in homogeneous phase. Reduction of complexes on mercury electrode in buffered aqueous solutions (pH 2–12) occurs generally as a two‐electron process of reductive decomposition. The formed Cu‐amalgam can be (e. g. during the anodic scan of CV) reoxidized to Cu(II) cation which undergoes re‐complexation resulting in the original complex. This process of a square diagram is manifold repeatable. The results also showed presence of several isomers differing in mutual orientation of substituents on cyclam nitrogen atoms. The primary “kinetic”, pentacoordinated isomers are irreversibly transformed to the stable, hexacoordinated “thermodynamic” ones upon heating. The development of isomerization process was followed electrochemically. The cross‐bridged cb‐TE2A derivative forms only one isomer which does not change even after heating. The higher stability of the complex manifests itself at pH>8 when the complex is reversibly reduced in one‐electron step, formally CuII/CuI, without decomposition.

Structural-property relationship in poly(vinyl aniline-co-maleic anhydride) for effective Hg2+ ions adsorption

Suitable functional modification of a polymer significantly influences its targeted applicability. Herein, we report new crosslinked copolymer synthesized from 4-vinylaniline (VA) and maleic anhydride MA) using adipic acid (AA) as the crosslinking agent, poly(VA-co-MA)-cl-AA where -co- stands for copolymer and -cl- for crosslinked. The poly(MA) component of as-synthesized copolymer was further hydrolyzed to form a new copolymer with pendant carboxyl groups. Both the copolymers, the as-synthesized and its hydrolyzed derivative, were evaluated as Hg2+ ions adsorbents. The adsorption capacity (q) was studied by variation of various adsorption parameters. The copolymer exhibited excellent Hg2+ ions adsorption (qmax = 202.43 mg g-1) with high cumulative q value (1151.3 mg g-1) in multiple cycles. The present work reveals important aspects of simple structural and functional modification of polymers achieved through simple polymer analogous reactions significantly influence their targeted applications. The findings documented in this report indicate the existence of crucial structure-activity relationship in polymer action and can be handy in designing more selective and efficient materials in future.

Crosslinking through acyl hydrazone formation by reacting water soluble polyurethanes derived from ketone diol comonomers and those containing hydrazide pendant groups

Fully water-based formulations are gaining traction with the sustainability initiative for various applications. In this regard, producing the components required for making these formulations by eliminating toxic reagents is highly desirable. Hydrazone formation is widely used as a non-hazardous curing process in coating applications. Generally, carbonyl compounds that are used in the hydrazone forming reaction are nearly exclusively derived from vinyl polymers. This article describes a facile process for making carbonyl group containing diols and keto group containing water-soluble polymers therefrom by step growth or condensation polymerization. A water-soluble polymeric hydrazide was prepared by DCC coupling reaction between hydrazine hydrate and a polyurethane bearing pendant carboxylic acid group. The aqueous solutions of keto group containing, and hydrazide pendant polymers were mixed and coated on glass slides. Subsequently, the acyl hydrazone formation was studied under static heating in a hot air oven and a dynamic condition provided by blowing air under ambient conditions with a hair dryer. The dynamic nature of the latter process more than compensated the absence of direct heating to induce drying and hydrazone formation sequentially as studied by FT-IR spectroscopy. The cured slides were stable to water and were sensitive to weakly acidic aqueous solutions (about pH 3) formed by dissolving citric acid in water. The keto group containing diols enabled the hydrazone formation in polymer pairs entirely derived from step growth polymerization. As step growth or condensation polymers potentially offer both degradability and recycling through the cleavage of labile bonds prevailing in the polymer backbone, these keto group containing diols are preferable alternatives to keto group containing vinyl monomers commonly used for making hydrazones.

Recyclable adsorption removal and fluorescent monitoring of hexavalent chromium by electrospun nanofibers membrane derived from Tb3+ coordinating polyarylene ether amidoxime

Emerging technologies or advanced materials which can simultaneously adsorb and detect highly toxic Cr(VI) are urgently in demand for environmental remediation. Herein, we have designed and synthesized a functional polyarylene ether with aromatic main chain and pendent carboxyl groups along with amidoxime group that can be coordinated with different metal ions. Thanks to its versatile activation of the lanthanide ions' inherent fluorescence and good processability, the fluorescent nanofiber membranes with competitive Cr(VI) adsorption and detection performance have been fabricated via one-step electrospinning of mixed solution containing synthesized polymer and terbium salt. More specifically, the optimized nanofiber membrane exhibits a maximal Cr(VI) adsorption of 278.2 mg/g and specific detection for hexavalent chromium down to 11.76 nM. More importantly, the prepared fluorescent nanofiber membranes can be easily re-generated and re-used for both Cr(VI) adsorption and detection for five times. Given the unique advantages of easy fabrication, competitive dual functionalities as well as good reusability of electrospun fluorescent nanofiber membranes, the present work basically opens up new insight in the design of multifunctional recyclable material for the remediation of heavy metal pollution.

Modular Photochemical Flow Synthesis of Structurally Diverse Benzyne and Triazine Precursors

AbstractBenzyne and related arynes are classical high‐energy species with a rich history of widespread applications in synthesis. However, despite several synthetic routes being available to generate arynes and their precursors, none represents an ideal entry to benzyne chemistry in view of safety, scalability, and sustainability. Here we report a new photochemical flow process allowing for the generation of benzyne precursors in high yields, and throughput, with easy isolation of multigram quantities of products. This process leverages a catalyst‐free photochemical rearrangement via a photoexcited nitro arene which involves a cyclic hydroxylamine intermediate that has been fully characterized. The resulting precursors were converted to benzynes via a second photochemical flow process generating heterocyclic targets upon trapping with azide and sydnone partners. Remarkably, when reacting the benzyne precursors with secondary amines, a wide range of aryl triazines is obtained in good yields via a third photo‐flow transformation. This represents a modular approach to synthesize these species, that avoids the use of potentially explosive diazonium salts. Ultimately, three photochemical flow processes using a single high‐power LED light source (365 nm, adjustable in‐put power) are presented with manifest benefits compared to batch processing. Moreover, the functionalization of a pendent carboxyl group to form sets of biologically relevant aryl triazine‐based amides highlights further applications of these unique and industrially relevant triazine entities.

Insight into the synthesis of biocompatible polymer for collagen stabilization and leather process

Collagen-based biomaterials are highly effective owing to their high biocompatibility and non-immunogenicity, but their biological application is still constrained because of poor thermal stability. The greener crosslinkers devoid of aldehydes and toxic precursors have recently evoked considerable interest. In this work, biocompatible and multifunctional carboxyl polymer (MCP) has been synthesized by a simple one-step carboxylation reaction by modifying the hydroxyl group in the monomer, followed by polymerization in aqueous conditions. The synthesized polymer has been used for both collagen stabilization and leather processing. The circular dichroism studies revealed a significant change in the secondary structure of the collagen with increasing concentration of the MCP, and thermal stability of the rat tail tendon is enhanced up to 70 °C. The application of MCP as a crosslinker for collagen in the leather-making process along with metal salts increased the leather's thermal stability and improved uptake of the metal salts. The interaction mechanism of MCP and the metals during the tanning process is through complexation with carboxyl pendants available on the MCP backbone, as confirmed by UV–Visible and IR spectroscopy. The experimental leathers showed a uniform penetration of tanning agents and excellent mechanical properties compared to the control leathers. Further, biocompatibility studies using 3 T3 fibroblast cells revealed that the MCP did not induce any significant cytotoxicity with cell viability of 96%, confirming the non-toxic nature of the synthesized polymer. Thus, the current study opens a new path for sustainable alternative polymeric crosslinkers for collagen stabilization and its potential application in biomaterial and leather-making fields.

Thermally curable polyurethanes with main-chain benzoxazine and pendant carboxylic acid groups and their use as electrically insulating coatings

Thermally curable polyurethanes with main-chain benzoxazine and pendant carboxylic acid groups and their use as electrically insulating coatings

BIO26: Engineering Anti-platelet polymers for regenerative cardiovascular applications

Thrombogenesis is the main failure cause of implantable cardiovascular devices. Thrombus formation not only occludes devices but exacerbates immune responses responsible for foreign body reaction. Biodegradable polymers modified with anticoagulating moieties represent a strategy to overcome these limitations. Herein, we propose the use of a novel polyester urethane urea (PEUU) with pendant carboxyl groups for functionalization with different anti-platelet deposition molecules. PEUU was synthesized from PCL (Polycaprolactone), 1,4-diisocyanatobutane and putrescine, and then chemically oxidized to introduce carboxyl groups in the polymer backbone (PEUU-COOH). PEUU-COOH was functionalized in-situ with Polyethyleneimine mW 400 (PEI), 4 arm Polyethylene Glycol (PEG-4-Arm-NH2), seleno-L-cystine, heparin sodium and fondaporinux as anti-platelet deposition molecules. After solvent casting, functionalization was confirmed via Fourier-transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Metabolic activity (MTT) and hemolysis assays were performed to validate biocompatibility. Anti-platelet activity of PRP exposed films was examined via a platelet aggregation assay, through an activation assay via lactate dehydrogenase (LDH), and by surface imaging with scanning electron microscopy (SEM). Whole-blood clotting time quantification assay was carried out to evaluate anticogulating properties. Upon oxidation, PEUU exhibited COOH pendant groups that were successfully employed to conjugate the anti-platelet molecules, obtaining homogeneous films. Overall cytotoxicity was below 20% and the hemolysis was below 5%, suggesting high biocompatibility and hemocompatibility. The most potent anticoagulant activity was obtained for heparin-functionalized materials followed by PEG-4-Arm-NH2 and PEI. Surprisingly, Seleno-L-cystine and Fondaporinux showed no anti-platelet activity. Results indicate that the polymers introduced here are a promising strategy to avoid thrombogenesis in vascular grafts.

Electrochemical Gelation of Metal Chalcogenide Quantum Dots: Applications in Gas Sensing and Photocatalysis.

ConspectusMetal chalcogenide quantum dots (QDs) are prized for their unique and functional properties, associated with both intrinsic (quantum confinement) and extrinsic (high surface area) effects, as dictated by their size, shape, and surface characteristics. Thus, they have considerable promise for diverse applications, including energy conversion (thermoelectrics and photovoltaics), photocatalysis, and sensing. QD gels are macroscopic porous structures consisting of interconnected QDs and pore networks in which the pores may be filled with solvent (i.e., wet gels) or air (i.e., aerogels). QD gels are unique because they can be prepared as macroscale objects while fully retaining the size-specific quantum-confined properties of the initial QD building blocks. The extensive porosity of the gels also ensures that each QD in the gel network is accessible to the ambient, leading to high performance in applications that require high surface areas, such as (photo)catalysis and sensing.Metal chalcogenide QD gels are conventionally prepared by chemical approaches. We recently expanded the toolbox for QD gel synthesis by developing electrochemical gelation methods. Relative to conventional chemical oxidation approaches, electrochemical assembly of QDs (1) enables the use of two additional levers for tuning the QD assembly process and gel structure: electrode material and potential, and (2) allows direct gel formation on device substrates to simplify device fabrication and improve reproducibility. We have discovered two distinct electrochemical gelation methods, each of which enables the direct writing of gels on an active electrode surface or the formation of free-standing monoliths. Oxidative electrogelation of QDs leads to assemblies bridged by dichalcogenide (covalent) linkers, whereas metal-mediated electrogelation proceeds via electrodissolution of active metal electrodes to produce free ions that link QDs by binding to pendant carboxylate functionalities on surface ligands (non-covalent linkers). We further demonstrated that the electrogel composition produced from the covalent assembly could be modified by controlled ion exchange to form single-ion decorated bimetallic QD gels, a new category of materials. The QD gels exhibit unprecedented performance for NO2 gas sensing and unique photocatalytic reactivities (e.g., the "cyano dance" isomerization and the reductive ring-opening arylation). The chemistry unveiled during the development of electrochemical gelation pathways for QDs and their post-modification has broad implications for guiding the design of new nanoparticle assembly strategies and QD gel-based gas sensors and catalysts.

Synthesis and Post-Processing of Chemically Homogeneous Nanothreads from 2,5-Furandicarboxylic Acid.

Compared with conventional, solution-phase approaches, solid-state reaction methods can provide unique access to novel synthetic targets. Nanothreads-one-dimensional diamondoid polymers formed through the compression of small molecules-represent a new class of materials produced via solid-state reactions, however, the formation of chemically homogeneous products with targeted functionalization represents a persistent challenge. Through careful consideration of molecular precursor stacking geometry and functionalization, we report here the scalable synthesis of chemically homogeneous, functionalized nanothreads through the solid-state polymerization of 2,5-furandicarboxylic acid. The resulting product possesses high-density, pendant carboxyl functionalization along both sides of the backbone, enabling new opportunities for the post-synthetic processing and chemical modification of nanothread materials applicable to a broad range of potential applications.

Synthesis and Post‐Processing of Chemically Homogeneous Nanothreads from 2,5‐Furandicarboxylic Acid**

AbstractCompared with conventional, solution‐phase approaches, solid‐state reaction methods can provide unique access to novel synthetic targets. Nanothreads—one‐dimensional diamondoid polymers formed through the compression of small molecules—represent a new class of materials produced via solid‐state reactions, however, the formation of chemically homogeneous products with targeted functionalization represents a persistent challenge. Through careful consideration of molecular precursor stacking geometry and functionalization, we report here the scalable synthesis of chemically homogeneous, functionalized nanothreads through the solid‐state polymerization of 2,5‐furandicarboxylic acid. The resulting product possesses high‐density, pendant carboxyl functionalization along both sides of the backbone, enabling new opportunities for the post‐synthetic processing and chemical modification of nanothread materials applicable to a broad range of potential applications.

Dicarboxylate-containing and fully substituted ferrocene with rapid dissolvability, high solubility, good stability, and moderate formal potential for mediated electrochemical detection.

An electron mediator with rapid dissolvability and high solubility in aqueous electrolyte solutions is essential for point-of-care testing based on mediated electrochemical detection. However, most ferrocenyl (Fc) compounds have slow dissolvability and poor solubility owing to high hydrophobicity of the Fc backbone. Moreover, many Fc compounds have poor stability and nonoptimal formal potential (). Herein, we present an Fc compound, Fc8m2c, which exhibits rapid dissolvability, high solubility, good stability, and moderate along with its high electron-mediation rate. The of Fc8m2c (0.17 V vs. Ag/AgCl) is tuned by two electron-withdrawing acyl substituents and eight electron-donating methyl substituents. Two pendant carboxylate groups of Fc8m2c allow for rapid dissolvability and high solubility (0.63 M in water), whereas full substitution in its two cyclopentadienyl ligands facilitates good chemical stability against decomposition in the presence of dissolved O2 and ambient light. A moderate enables the application of a potential of 0.07 V at which electrochemical background currents are low and also contributes toward resisting the decomposition of both Fc8m2c and Fc8m2c+. Fc8m2c provides a high electron-mediation rate constant (2.4 × 106 M-1 s-1) in glucose detection using glucose dehydrogenase. When Fc8m2c is applied to a glucose sensor, the calculated detection limit is ∼0.1 mM with a measurement period of 5 s. Considering that the normal concentration of glucose in serum is between 3.9 and 6.6 mM, the detection limit is sufficiently low. These results show that Fc8m2c is an excellent electron-mediator candidate for sensitive and rapid glucose detection.

Catalytic isomerization of glucose to fructose over organic ligands: a DFT study.

Isomerization processes between glucose and fructose catalyzed by four different organic ligands are investigated with quantum chemistry methods in this study. These organic ligands are the carboxylic pendant group, sulfonic pendant group, amino pendant group, and 1H-imidazole ligand. After guessing and verifying a variety of elementary reactions, transition states and energy barriers that are relevant to the optimum pathways have been confirmed. The effective barriers under the catalysis of the carboxylic pendant group, sulfonic pendant group, amino pendant group, and 1H-imidazole ligand are 97.5kJmol-1, 134.7kJmol-1, 146.7kJmol-1, and 167.7kJmol-1, respectively. Then, based on the conclusions of the non-solvation model, the effective barriers in solvents are briefly investigated. The implicit model predicts that solvents bring little improvement or setback to catalyzed reaction models. The explicit model shows that the proton transfer with the participant of water molecules can improve the catalytic performance of Lewis bases in these reactions. The detailed reaction mechanism combing and reliable reaction templates provided in this work will be useful for catalysis designs for glucose transformation to fructose. This work used the computational level of ωB97M-D3BJ/def2-SVP and the software package of ORCA 4.2. For solvent effects, energies of the gas phase were corrected by the combination of C-PCM and SMD.