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Recent emergence of FTIR spectromicroscopy (micro-FTIR) as a dynamic spectroscopy for imaging to the study of biological chemistry has opened new possibilities for investigating in situ drug release, redox chemistry effects with biological molecules, DNA and drug interactions, membranes dynamic, and redox reaction with proteins at the single cell level. Micro-FTIR applied to metallodrugs have been playing important role in the last decade because of its great potential to achieve more robust and controlled pharmacological effects against several diseases, including cancer. An important aspect in the development of these drugs is to understand their cellular properties, such as uptake, accumulation, activity, and toxicity. In this review, we present the potential application of the micro-FTIR and its importance for studying metal-based drugs, highlighting the prospective of chemistry of living cells. We also present a bioimaging emphasis, which is therefore of high importance to localize the cellular processes, for the proper understanding of the mechanism of action.

Made available in DSpace on 2022-04-28T19:42:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-01 The exceptional catalysis for the oxygen reduction reaction (ORR) of bilirubin oxidase (BOD) encouraged us to reevaluate the existing catalytic models. Experimental evidence of the electron-transfer reaction's dependence on the three-dimensional structure of BOD is demonstrated by operando X-ray absorption spectroscopy (XAS) combined with Quantum Mechanics/Molecular Mechanics (QM/MM). We suggest that if a catalytic reaction occurs in a three-dimensional environment (3D-catalysis), the energies involved in the transition states during the electron transfer cannot be explained by adsorption kinetics. In contrast, there is the formation of a three-dimensional complex (TDC). Our data suggest influence of the metallic cofactor electronic structure as well as the spatial disposition of its surrounding ligands on the electron transfer that promotes the biocatalysis. We propose that investigating enzymatic redox processes involving a dynamic three-dimensional enzymatic structure can provide further insights as how heterogeneous catalysis can work beyond single atoms and surface chemistry. São Carlos Institute of Chemistry University of São Paulo Institute of Chemistry São Paulo State University Institute of Chemistry São Paulo State University

Synthetic biology pursues the understanding of biological processes and their possible mimicry with artificial bioinspired materials. A number of materials have already been used to mimic the active site of simple redox proteins, including nanosized iron oxides due to their redox properties. However, the mimicry of membrane redox protein complexes is still a challenge. Herein, magnetic iron oxide nanoparticles (NPs), incorporated as non-proteinaceous complexes III and IV in a mitochondrial model membrane, catalyze electron transfer (ET) similarly to the natural complexes towards cytochrome c. The associated molecular mechanism is experimentally proven in solution and in a Langmuir-Blodgett film. A direct and entropy-driven ET, with rate constant of 2.63 ± 0.05 L mol−1 at 25 °C, occurs between the iron sites of the NPs and the cytochrome c heme group, not affecting the protein secondary and tertiary structures. This process requires an activation energy of 40.2 ± 1.5 kJ mol−1 resulting in an overall Gibbs free energy of −55.3 kJ mol−1. Furthermore, the protein-NP system is governed by electrostatic and non-polar forces that contribute to an associative mechanism in the transition state. Finally, the incorporated NPs in a model membrane were able to catalyze ET, such as the natural complexes in respiratory chain. This work presents an experimental approach demonstrating that inorganic nanostructured systems may behave as embedded proteins in the eukaryotic cells membrane, opening the way for more sophisticated and robust mimicry of membrane protein complexes.

We introduce a set up by coupling multiplex FTIR microscopy to electrochemistry through a home-made spectroelectrochemical cell to observe real time changes in the electronic states of polymeric islands by monitoring the oxidation states of polyaniline (PANI). The resultant technique, called electrochemical-coupled vibrational spectromicroscopy (EVSM), enables the measurement of structural changes in the conductive islands of PANI with the spatial resolution as high as 2.5 μm. Unique 2D and 3D chemical maps obtained by the integration of the spectral bands in the subtractively normalized interfacial infrared (SNIFTIR) spectra reveal electrochemical heterogeneity, showing promising topological properties control for conducting polymer-based electronic devices.

We introduce a set up to observe real time changes in the electronic states of polymeric islands by monitoring the redox states of polyaniline using electrochemical-coupled vibrational spectromicroscopy (EVSM). Unique 2D and 3D chemical maps reveal electrochemical heterogeneity, showing promising topological properties controls.

Enzyme immobilization on solid conducting surfaces faces challenges for practical applications in technologies such as biosensors and biofuel cells. Short-term stability, poor electrochemical performance, and enzyme inhibition are some unsolved issues. Here, we show a simple methodology for bilirubin oxidase (BOD) immobilization on carbon-based gas diffusion electrode for four-electron electrochemical oxygen reduction reaction. BOD is incorporated into a Nafion® matrix and crosslinked with glutaraldehyde by a one-pot reaction in buffered solution, producing a stable BOD-based biogel. The biogel provides stable electrode performance and allows the direct electron-transfer mechanism of multicopper centers buried in the enzyme. A biocatalytic reduction current of −1.52 ± 0.24 mA cm−2 at 0.19 ± 0.06 V was observed under gas diffusion conditions. Additionally, the bioelectrode showed unprecedented long-term stability under continuous operation combined with satisfactory catalytic current without redox mediator. The BOD-based biogel layer thickness and the entrapment of BOD into Nafion network are crucial for the biocathode stability, and BOD crosslinking by glutaraldehyde contributes to enhance the catalytic currents. Further, the BOD-based biogel provides a suitable microenvironment for long-term enzymatic activity involving three-phase interfacial reaction. The present study provides new insights into enzyme immobilization to overcome the critical short-term stability of enzyme-based electrochemical devices for practical applications.

Graphene is considered a model material for surfaces because it is stable despite being composed of a single layer of carbon atoms. Although the thermal and electronic properties of graphene are well reported, the behavior of graphene sheets with the addition of charges to the structure is not well understood. Combining infrared spectroscopy, electrochemical analysis, and computational simulations, we report the effect of an electrochemically induced covalent anchoring of 4-carboxyphenyl (4-CP) units on the optical and electronic properties of graphene. Charges in graphene become concentrated at specific sites of the sheet when electrochemically perturbed and the functionalization occurs inhomogeneously along the graphene sheet. We observed that, when graphene is covalently functionalized, the resistance to heterogeneous electron transfer is increased by a factor of 1.4. Furthermore, scattering-type scanning near-field optical microscopy and atomic force microscopy show that the covalent functionalization affects drastically the optical and physical properties of the graphene/SiO2 system, especially the plasmon-phonon coupling after the functionalization. In addition, from these we infer that a comparatively higher degree of functionalization occurs near the electrode edges. These results are supported by computational simulations, which show that the covalent anchoring of 4-CP units weakens electron transfer because the charges are retained on the sp3-hybridized carbon atoms generated upon functionalization, suggesting that graphene properties are deeply influenced by the way the molecules are immobilized on its structure.

Here we propose an experimental setup based on operando X-ray absorption spectroscopy (XAS) to understand why copper-containing oxidoreductase enzymes show exceptional performance as catalysts for the oxygen reduction reaction (ORR). An electrode based on carbon nanoparticles organized in mesoporous structures with bilirubin oxidase (BOD) was developed to be used in a home-made operando XAS electrochemical cell, and we probed the electron transfer under ORR regime. In the presence of molecular oxygen, the BOD cofactor containing 4 copper ions require an overpotential about 150 mV to be reduced as compared to that in the absence of oxygen. A second electron transfer step, which occurs faster than the cofactor reduction, suggests that the cooper ions act as a tridimensional redox active electronic bridges for the electron transfer reaction., Understanding enzyme active sites can elucidate fundamental enzymatic reaction pathways and inform designs for synthetic catalysts. Here, authors employ operando X-ray absorption spectroelectrochemistry to assess copper ions in bilirubin oxidase during oxygen reduction electrocatalysis.

Multiplex Fourier-transform infrared microscopy (μFT-IR) helped to monitor trans-[Ru(NO) (NH3)4 (isn)]3+ (I), uptake by A549 lung carcinoma cell, as well as the generation of its product, nitric oxide (NO), inside the cell. Chronoamperometry with NO-sensor and μFT-IR showed that exogenous NADH and the A549 cell induced the NO release redox mechanism. Chemical imaging confirmed that (I) was taken up by the cell, and that its localization coincided with its consumption in the cellular environment within 15 min of exposure. The Ru–NO absorption band in the IR spectrum shifted from 1932 cm−1, when NO was coordinated to Ru as {RuII–NO+}3+, to 1876 cm−1, due the formation of reduced species {RuII–NO0}2+, a precursor of NO release. Futhermore, the μFT-IR spectral profile demonstrated that, as a result of the NO action on the target, NO interacted with nucleic acids, which provided a biochemical response that is detectable in living cells.

Endonuclease III (EndoIII) is a DNA glycosylase that contains the [4Fe4S] cluster, which is essential for the protein to bind to damaged DNA in a process called base excision repair (BER). Here we propose that the change in the covalency of Fe–S bonds of the [4Fe4S] cluster caused by double-stranded (ds)-DNA binding is accompanied by a change in their strength, which is due to alterations of the electronic structure of the cluster. Micro-FTIR spectroscopy in the mid-IR region and FTIR spectroscopy in the far IR (450 and 300 cm−1) were used independently to study the structural changes in EndoIII and the behavior of the [4Fe4S] cluster it contains, in the native form and upon its binding to ds-DNA. Structural changes in the DNA itself were also examined. The characteristics vibrational modes, corresponding to Fe–S (sulfide) and Fe–S (thiolate) bonds were identified in the cluster through far IR spectroscopy as well through quantum chemistry calculations. Based on the experimental results, these vibrational modes shift in their spectral positions caused by negatively charged DNA in the vicinity of the cluster. Modifications of the Fe–S bond lengths upon DNA binding, both of the Fe–S (sulfide) and Fe–S (thiolate) bonds in the [4Fe4S] cluster of EndoIII are responsible for the stabilization of the cluster towards higher oxidation state (3+), and hence its redox communication along the ds-DNA helix.

We have used temperature gradient surface plasmon resonance (SPR) measurements to quantitatively evaluate how the stability of different types of hybrids formed with DNA probes on surfaces is affected by probe spacing. SPR sensors with different average surface densities of probes were prepared by coadsorbing probes with lateral spacers strands comprised of phosphorothioated adenine nucleotides (A15*). Increasing the fraction of A15* spacers in the immobilization solution results in larger distances between probes on the sensor, determined here using a combination of SPR and X-ray photoelectron spectroscopy (XPS) measurements. The hybridization activities of probes were simultaneously measured over a temperature range that spanned the denaturation temperature (Tm) of hybrids by applying a spatial temperature gradient across the sensor surface. The resulting temperature profiles of hybridization activity show how the stability of hybrids increases as either the distance between probes or the ionic strength...

The controlled assembly of metal nanoparticles into ordered structures interacting with biological molecules is an emerging concept in surface science. Here, bare magnetite nanoparticles (Fe3O4–NPs...

IR spectroscopy is an excellent method for understanding surface redox chemistry. However, obtaining sufficient spatial resolution to analyze in situ surface redox reactions is difficult because the aqueous sampling environments provide some challenges for IR spectroscopy. These challenges arise because of the vibrational contribution of water. In this letter, we demonstrate a solution to this problem, where the key development enabling the coupling of spectromicroscopy with electrochemical measurements is a CaF2/electrolyte/Au sandwich IR-sensitive sample holder that acts as an electrochemical cell. In this system, there is a very thin layer of aqueous electrolyte (∼10 μm), and it is possible to monitor, in real time, the vibrational maps and changes to the Au surface modified with iron(II, III) hexacyanoferrate(II, III) by varying the electrochemical potential. By selecting specific vibrational modes with a focal plane array detector, which allows the simultaneous collection of IR spectra from 4096 micr...

Hybrid magnetite materials are interesting for both biomedical and catalytic applications due to their well-known biocompatibility, as well as their magnetic and electric properties. In this work we prepared Fe3O4 nanoparticles (NPs) coated with tannic acid (TA), a natural polyphenol, through two different synthetic routes, aiming to understand the influence of TA in the synthesis step and contribute to the development of water-dispersible magnetic materials. The coating process was verified by information obtained from transmission electron microscopy (TEM), zeta-potential and Fourier transform infrared (FTIR) spectroscopy. The incorporation of TA after Fe3O4 NPs production generated spherical NPs smaller than 10 nm, suggesting that TA plays a fundamental role in the nucleation and organization of Fe3O4 NPs. Data from both density functional theory (DFT) and FTIR allowed us to infer that Fe3O4 interacts mainly with the carbonyl groups of TA. Hybrid materials having improved water-dispersibility are very attractive for biomedical applications., The authors acknowledge the financial support from CNPq (470996/2011-0 and 304684/2011-2 projects), CAPES (nBioNet), FAPEPI, MICINN (Spain) for project MAT 2011-25870, and CENAPAD-UFC by availability of computational resources used in the development of theoretical calculations.

We report a highly resolved approach for quantitatively measuring the temperature dependence of molecular binding in a sensor format. The method is based on surface plasmon resonance (SPR) imaging measurements made across a spatial temperature gradient. Simultaneous recording of sensor response over the range of temperatures spanned by the gradient avoids many of the complications that arise in the analysis of SPR measurements where temperature is varied. In addition to simplifying quantitative analysis of binding interactions, the method allows the temperature dependence of binding to be monitored as a function of time, and provides a straightforward route for calibrating how temperature varies across the gradient. Using DNA hybridization as an example, we show how the gradient approach can be used to measure the temperature dependence of binding kinetics and thermodynamics (e.g., melt/denaturation profile) in a single experiment.

Supramolecular self-assembly has been demonstrated to be a useful approach to developing new functional nanomaterials. In this work, we used a cobalt Prussian blue analogue (PBA, Co3[Co(CN)6]2) compound and a β-cyclodextrin (CD) macrocycle to develop a novel host-guest PBA-CD nanomaterial. The preparation of the functional magnetic material involved the self-assembly of CD molecules onto a PBA surface by a co-precipitation method. According to transmission electronic microscopy results, PBA-CD exhibited a polydisperse structure composed of 3D nanocubes with a mean edge length of 85 nm, which became shorter after CD incorporation. The supramolecular arrangement and structural, crystalline and thermal properties of the hybrid material were studied in detail by vibrational and electronic spectroscopies and X-ray diffraction. The cyclic voltammogram of the hybrid material in a 0.1 mol · L(-1) NaCl supporting electrolyte exhibited a quasi-reversible redox process, attributed to Co2+/Co3+ conversion, with an E1/2 value of 0.46 V (vs. SCE), with higher reversibility observed for the system in the presence of CD. The standard rate constants for PBA and PBA-CD were determined to be 0.07 and 0.13 s(-1), respectively, which suggests that the interaction between the nanocubes and CD at the supramolecular level improves electron transfer. We expect that the properties observed for the hybrid material make it a potential candidate for (bio)sensing designs with a desirable capability for drug delivery.