Enzyme-Loaded Hemin/G-Quadruplex-Modified ZIF-90 Metal-Organic Framework Nanoparticles: Bioreactor Nanozymes for the Cascaded Oxidation of N-hydroxy-l-arginine and Sensing Applications.

Biocatalytic cascades are challenging to operate in homogeneous solution, where diffusional mass transport hinders efficient communication between the reactive components. There is great interest in developing devices to perform such transformations in confined environments, which increase the efficiency of the cascaded process by generating high local concentrations of the reactive species. Herein, a bioreactor-nanozyme assembly is introduced for the cascaded aerobic oxidation of N-hydroxy-l-arginine (NOHA) to citrulline in the presence of glucose. The reaction mimics a key step in the nitric oxide synthase oxidation of l-arginine in nature. The system consists of glucose oxidase (GOx)-loaded hemin/G-quadruplex (hemin/G4)-modified ZIF-90 metal-organic framework nanoparticles. The aerobic oxidation of glucose by GOx yields H2 O2 that fuels the hemin/G4-catalyzed oxidation of NOHA into citrulline. The process driven by the bioreactor-nanozyme system is ≈sixfold enhanced compared to the homogeneous mixture of the biocatalysts, due to its operation in the confined environment of the nanoparticles. Extension to a three-step cascade is then demonstrated using a bioreactor composed of ß-galactosidase/GOx-loaded hemin/G4-modified ZIF-90 nanoparticles activating the cascaded oxidation of NOHA to citrulline, in the presence of lactose. Moreover, the bioreactor-nanozyme hybrid is applied as a functional optical sensor of glucose, using fluorescence or chemiluminescence as readout signals.

Stimuli-responsive metal-organic framework nanoparticles for controlled drug delivery and medical applications.

Stimuli-responsive metal-organic framework nanoparticles, NMOFs, provide a versatile platform for the controlled release of drugs and biomedical applications. The porous structure of NMOFs, their biocompatibility, low toxicity, and efficient permeability turn the NMOFs into ideal carriers for therapeutic applications. Two general methods to gate the drug-loaded NMOFs and to release the loads were developed: by one method, the loaded NMOFs are coated or surface-modified with stimuli-responsive gates being unlocked in the presence of appropriate chemical (e.g., ions or reducing agents), physical (e.g., light or heat), or biomarker (e.g., miRNA or ATP) triggers. By a second approach, the drug-loaded NMOFs include encoded structural information or co-added agents to induce the structural distortion or stimulate the degradation of the NMOFs. Different chemical triggers such as pH changes, ions, ATP, or redox agents, and physical stimuli such as light or heat are applied to degrade the NMOFs, resulting in the release of the loads. In addition, enzymes, DNAzymes, and disease-specific biomarkers are used to unlock the gated NMOFs. The triggered release of drugs for cancer therapy, anti-blood clotting, and the design of autonomous insulin-delivery systems ("artificial pancreas") are discussed. Specifically, multi-drug carrier systems and functional NMOFs exhibiting dual and cooperative therapeutic functions are introduced. The future perspectives and applications of stimuli-responsive particles are addressed.

Mimicking Functions of Native Enzymes or Photosynthetic Reaction Centers by Nucleoapzymes and Photonucleoapzymes.

The covalent linkage of catalytic units to aptamer sequence-specific nucleic acids exhibiting selective binding affinities for substrates leads to functional scaffolds mimicking native enzymes, nucleoapzymes. The binding of the substrates to the aptamer and their structural orientation with respect to the catalytic units duplicate the functions of the active center of enzymes. The possibility of linking the catalytic sites directly, or through spacer units, to the 5'-end, 3'-end, and middle positions of the aptamers allows the design of nucleoapzyme libraries, revealing structure-functions diversities, and these can be modeled by molecular dynamics simulations. Catalytic sites integrated into nucleoapzymes include DNAzymes, transition metal complexes, and organic ligands. Catalytic transformations driven by nucleoapzymes are exemplified by the oxidation of dopamine or l-arginine, hydroxylation of tyrosine to l-DOPA, hydrolysis of ATP, and cholic acid-modified esters. The covalent linkage of photosensitizers to the tyrosinamide aptamer leads to a photonucleoapzyme scaffold that binds the N-methyl-N'-(3-aminopropane)-4,4'-bipyridinium-functionalized tyrosinamide to the aptamer. By linking the photosensitizer directly, or through a spacer bridge to the 5'-end or 3'-end of the aptamer, we demonstrate a library of supramolecular photosensitizer/electron acceptor photonucleoapzymes mimicking the functions of photosystem I in the photosynthetic apparatus. The photonucleoapzymes catalyze the photoinduced generation of NADPH, in the presence of ferredoxin-NADP+-reductase (FNR), or the photoinduced H2 evolution catalyzed by Pt nanoparticles. The future prospects of nucleoapzymes and photonucleoapzymes are discussed.

Aptamer-Modified Cu2+-Functionalized C-Dots: Versatile Means to Improve Nanozyme Activities-"Aptananozymes".

The covalent linkage of aptamer binding sites to nanoparticle nanozymes is introduced as a versatile method to improve the catalytic activity of nanozymes by concentrating the reaction substrates at the catalytic nanozyme core, thereby emulating the binding and catalytic active-site functions of native enzymes. The concept is exemplified with the synthesis of Cu2+ ion-functionalized carbon dots (C-dots), modified with the dopamine binding aptamer (DBA) or the tyrosinamide binding aptamer (TBA), for the catalyzed oxidation of dopamine to aminochrome by H2O2 or the oxygenation of l-tyrosinamide to the catechol product, which is subsequently oxidized to amidodopachrome, in the presence of H2O2/ascorbate mixture. Sets of structurally functionalized DBA-modified Cu2+ ion-functionalized C-dots or sets of structurally functionalized TBA-modified Cu2+ ion-functionalized C-dots are introduced as nanozymes of superior catalytic activities (aptananozymes) toward the oxidation of dopamine or the oxygenation of l-tyrosinamide, respectively. The aptananozymes reveal enhanced catalytic activities as compared to the separated catalyst and respective aptamer constituents. The catalytic functions of the aptananozymes are controlled by the structure of the aptamer units linked to the Cu2+ ion-functionalized C-dots. In addition, the aptananozyme shows chiroselective catalytic functions demonstrated by the chiroselective-catalyzed oxidation of l/d-DOPA to l/d-dopachrome. Binding studies of the substrates to the different aptananozymes and mechanistic studies associated with the catalytic transformations are discussed.

Horizontal transmission of Piscirickettsia salmonis from the wild sub-Antarctic notothenioid fish Eleginops maclovinus to rainbow trout (Oncorhynchus mykiss) under experimental conditions.

Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis, a bacterial disease that affects farmed salmonids, causing high mortalities and significant economic losses in the Chilean salmon farm industry. Given the Chilean native fish species Patagonian blenny, Eleginops maclovinus, lives in the vicinity of salmon farms, it is relevant to clarify the epidemiological role that this species could play in the transmission and/or dissemination of this pathogen. This study aimed to evaluate the bidirectional transmission of P. salmonis between the Patagonian blenny and Oncorhynchus mykiss (rainbow trout), via a cohabitation challenge model. The results of this study demonstrated the transmission of the bacteria from Patagonian blennies to rainbow trout, considering the specific mortality in cohabitant rainbow trout, reaching 46%: the necropsy of these specimens, evidencing the characteristic pathological lesions of the disease and the positive results of the qPCR analysis for P. salmonis, in the same individuals. In contrast, no mortalities of Patagonian blenny specimens were recorded in the challenged experimental groups. This study is the first report showing the horizontal transmission of P. salmonis from a native non-salmonid species, such as the Patagonian blenny, to a salmonid species, generating the disease and specific mortality in rainbow trout, using a cohabitation challenge.

Aptamer-Functionalized Hybrid Nanostructures for Sensing, Drug Delivery, Catalysis and Mechanical Applications.

Sequence-specific nucleic acids exhibiting selective recognition properties towards low-molecular-weight substrates and macromolecules (aptamers) find growing interest as functional biopolymers for analysis, medical applications such as imaging, drug delivery and even therapeutic agents, nanotechnology, material science and more. The present perspective article introduces a glossary of examples for diverse applications of aptamers mainly originated from our laboratory. These include the introduction of aptamer-functionalized nanomaterials such as graphene oxide, Ag nanoclusters and semiconductor quantum dots as functional hybrid nanomaterials for optical sensing of target analytes. The use of aptamer-functionalized DNA tetrahedra nanostructures for multiplex analysis and aptamer-loaded metal-organic framework nanoparticles acting as sense-and-treat are introduced. Aptamer-functionalized nano and microcarriers are presented as stimuli-responsive hybrid drug carriers for controlled and targeted drug release, including aptamer-functionalized SiO2 nanoparticles, carbon dots, metal-organic frameworks and microcapsules. A further application of aptamers involves the conjugation of aptamers to catalytic units as a means to mimic enzyme functions "nucleoapzymes". In addition, the formation and dissociation of aptamer-ligand complexes are applied to develop mechanical molecular devices and to switch nanostructures such as origami scaffolds. Finally, the article discusses future challenges in applying aptamers in material science, nanotechnology and catalysis.

Triggered Release of Loads from Microcapsule-in-Microcapsule Hydrogel Microcarriers: En-Route to an "Artificial Pancreas".

A method to assemble stimuli-responsive nucleic acid-based hydrogel-stabilized microcapsule-in-microcapsule systems is introduced. An inner aqueous compartment stabilized by a stimuli-responsive hydrogel-layer (∼150 nm) provides the inner microcapsule (diameter ∼2.5 µm). The inner microcapsule is separated from an outer aqueous compartment stabilized by an outer stimuli-responsive hydrogel layer (thickness of ∼150 nm) that yields the microcapsule-in-microcapsule system. Different loads, e.g., tetramethyl rhodamine-dextran (TMR-D) and CdSe/ZnS quantum dots (QDs), are loaded in the inner and outer aqueous compartments. The hydrogel layers exist in a higher stiffness state that prevents inter-reservoir or leakage of the loads from the respective aqueous compartments. Subjecting the inner hydrogel layer to Zn2+-ions and/or the outer hydrogel layer to acidic pH or crown ether leads to the triggered separation of the bridging units associated with the respective hydrogel layers. This results in the hydrogel layers of lower stiffness allowing either the mixing of the loads occupying the two aqueous compartments, the guided release of the load from the outer aqueous compartment, or the release of the loads from the two aqueous compartments. In addition, a pH-responsive microcapsule-in-microcapsule system is loaded with glucose oxidase (GOx) in the inner aqueous compartment and insulin in the outer aqueous compartment. Glucose permeates across the two hydrogel layers resulting in the GOx catalyzed aerobic oxidation of glucose to gluconic acid. The acidification of the microcapsule-in-microcapsule system leads to the triggered unlocking of the outer, pH-responsive hydrogel layer and to the release of insulin. The pH-stimulated release of insulin is controlled by the concentration of glucose. While at normal glucose levels, the release of insulin is practically prohibited, the dose-controlled release of insulin in the entire diabetic range  is demonstrated. Also, switchable ON/OFF release of insulin is achieved highlighting an autonomous glucose-responsive microdevice operating as an "artificial pancreas" for the release of insulin.

Thermoplasmonic-Triggered Release of Loads from DNA-Modified Hydrogel Microcapsules Functionalized with Au Nanoparticles or Au Nanorods.

Microcapsules consisting of hydrogel shells cross-linked by glucosamine-boronate ester complexes and duplex nucleic acids, loaded with dyes or drugs and functionalized with Au nanoparticles (Au NPs) or Au nanorods (Au NRs), are developed. Irradiation of Au NPs or Au NRs results in the thermoplasmonic heating of the microcapsules, and the dissociation of the nucleic acid cross-linkers. The separation of duplex nucleic acid cross-linkers leads to low-stiffness hydrogel shells, allowing the release of loads. Switching off the light-induced plasmonic heating results in the regeneration of stiff hydrogel shells protecting the microcapsules, leading to the blockage of release processes. The thermoplasmonic release of tetramethylrhodamine-dextran, Texas Red-dextran, doxorubicin-dextran (DOX-D), or camptothecin-carboxymethylcellulose (CPT-CMC) from the microcapsules is introduced. By loading the microcapsules with two different drugs (DOX-D and CPT-CMC), the light-controlled dose release is demonstrated. Cellular experiments show efficient permeation of Au NPs/DOX-D or Au NRs/DOX-D microcapsules into MDA-MB-231 cancer cells and inefficient uptake by MCF-10A epithelial breast cells. Cytotoxicity experiments reveal selective thermoplasmon-induced cytotoxicity of the microcapsules toward MDA-MB-231 cancer cells as compared to MCF-10A cells. Also, selective cytotoxicity towards MDA-MB-231 cancer cells upon irradiation of the Au NPs- and Au NRs-functionalized microcapsules at λ = 532 or 910 nm is demonstrated.

A Bis-Zn2+ -Pyridyl-Salen-Type Complex Conjugated to the ATP Aptamer: An ATPase-Mimicking Nucleoapzyme.

Catalytic nucleic acids consisting of a bis-Zn2+ -pyridyl-salen-type ([di-ZnII 3,5 bis(pyridinylimino) benzoic acid]) complex conjugated to the ATP aptamer act as ATPase-mimicking catalysts (nucleoapzymes). Direct linking of the Zn2+ complex to the 3'- or 5'-end of the aptamer (nucleoapzymes I and II) or its conjugation to the 3'- or 5'-end of the aptamer through bis-thymidine spacers (nucleoapzymes III and IV) provided a set of nucleoapzymes exhibiting variable catalytic activities. Whereas the separated bis-Zn2+ -pyridyl-salen-type catalyst and the ATP aptamer do not show any noticeable catalytic activity, the 3'-catalyst-modified nucleoapzyme (nucleoapzyme IV) and, specifically, the nucleoapzyme consisting of the catalyst linked to the 3'-position through the spacer (nucleoapzyme III) reveal enhanced catalytic features in relation to the analogous nucleoapzyme substituted at the 5'-position (kcat =4.37 and 6.88 min-1 , respectively). Evaluation of the binding properties of ATP to the different nucleoapzyme and complementary molecular dynamics simulations suggest that the distance separating the active site from the substrate linked to the aptamer binding site controls the catalytic activities of the different nucleoapzymes.

Stimuli-Responsive Biomolecule-Based Hydrogels and Their Applications.

This Review presents polysaccharides, oligosaccharides, nucleic acids, peptides, and proteins as functional stimuli-responsive polymer scaffolds that yield hydrogels with controlled stiffness. Different physical or chemical triggers can be used to structurally reconfigure the crosslinking units and control the stiffness of the hydrogels. The integration of stimuli-responsive supramolecular complexes and stimuli-responsive biomolecular units as crosslinkers leads to hybrid hydrogels undergoing reversible triggered transitions across different stiffness states. Different applications of stimuli-responsive biomolecule-based hydrogels are discussed. The assembly of stimuli-responsive biomolecule-based hydrogel films on surfaces and their applications are discussed. The coating of drug-loaded nanoparticles with stimuli-responsive hydrogels for controlled drug release is also presented.

A Multisensor System for the Characterization of the Field Pressure in Terrain. Accuracy, Response, and Adjustments.

In different disciplines of science, the knowledge of the resulting pressures in the subsoil can help to understand physical phenomena of mass exchange between the atmosphere and the terrain. The measurement of lower differential pressures is complicated given the low range of detected values. In this paper, a multisensor system has been designed and developed to measure differential pressures in radon gas transport studies. The adequacy of this system has been proven using a purpose-built pressure chamber and an automatic motion system developed by the authors. The temporal response frequencies, the pressure values measured by the sensors, and their ability to link in series were analyzed to offer a multisensor spatial and temporal mapping. At the same time, the influence of the components required for a real deployment were studied using different tube lengths and diameters, connectors, and obstructions across the operating range of the pressure sensors. The system has also been tested for measuring differential pressures in a real model with a concrete slab above the soil and a pressure generator system below. It was found that this system is very suitable for outdoor measurements that demand a quick temporal response and accuracy.

Catalyzed and Electrocatalyzed Oxidation of l-Tyrosine and l-Phenylalanine to Dopachrome by Nanozymes.

Catalyzed oxygen insertion into C-H bonds represents a continuous challenge in chemistry. Particularly, driving this process at ambient temperature and aqueous media represents a "holy grail" in catalysis. We report on the catalyzed cascade transformations of l-tyrosine or l-phenylalanine to dopachrome in the presence of l-ascorbic acid/H2O2 as oxidizing mixture and CuFe-Prussian Blue-like nanoparticles, Fe3O4 nanoparticles or Au nanoparticles as catalysts. The process involves the primary transformation of l-tyrosine to l-DOPA that is further oxidized to dopachrome. The transformation of l-phenylalanine to dopachrome in the presence of CuFe-Prussian Blue-like nanoparticles and l-ascorbic acid/H2O2 involves in the first step the formation of l-tyrosine and, subsequently, the operation of the catalytic oxidation cascade of l-tyrosine to l-DOPA and dopachrome. Electron spin resonance experiments demonstrate that ascorbate radicals and hydroxyl radicals play cooperative functions in driving the different oxygen-insertion processes. In addition, the aerobic elecrocatalyzed oxidation of l-tyrosine to dopachrome in the presence of naphthoquinone-modified Fe3O4 nanoparticles and l-ascorbic acid is demonstrated. In this system, magnetic-field attraction of the naphthoquinone-modified Fe3O4 nanoparticles onto the electrode allows the quinone-mediated electrocatalyzed reduction of O2 to H2O2 (bias potential -0.5 V vs SCE). The electrogenerated H2O2 is then utilized to promote the transformation of l-tyrosine to dopachrome in the presence of l-ascorbic acid and Fe3O4 catalyst.

Seed Characteristics and Nutritional Composition of Pine Nut from Five Populations of P. cembroides from the States of Hidalgo and Chihuahua, Mexico.

The aim of this study was to analyze the seed characteristics and nutritional composition of five pine nut P. cembroides samples from two Mexican states. Morphometry, proximal composition, phenolic compounds, and antioxidant capacity were determined. Samples differed in several morphometric trails, but important differences were documented between SMCH and JCZH samples from Hidalgo State. JCZH and FMH had the highest contents of water, lipids, protein, flavonoids, and antioxidant activity, while CMCC population from Chihuahua State had presented the highest content of ash and carbohydrates. Morphometry and chemical composition data were subjected to clustering analysis. This analysis showed that SMCH and LFCH from Hidalgo State were well separated from the JCZH and FMH populations from Hidalgo State, which showed a strong similarity between them, while the CMCC from Chihuahua State was the most distant population. Principal components analysis showed that the variables that strongly contributed to PC1 were the antioxidant activity determined by FRAP assay, flavonoids, and water content. These data have provided biochemical markers that could help to establish phylogenetic associations between populations, and also to reveal potentially account as an alternative source for dietary nutrition.

Multi-triggered Supramolecular DNA/Bipyridinium Dithienylethene Hydrogels Driven by Light, Redox, and Chemical Stimuli for Shape-Memory and Self-Healing Applications.

Multi-triggered DNA/bipyridinium dithienylethene (DTE) hybrid carboxymethyl cellulose (CMC)-based hydrogels are introduced. DTE exhibits cyclic and reversible photoisomerization properties, switching between the closed state (DTEc), the electron acceptor, and the open isomer (DTEo) that lacks electron acceptor properties. One system introduces a dual stimuli-responsive hydrogel containing CMC chains modified with electron donor dopamine sites and self-complementary nucleic acids. In the presence of DTEc and the CMC scaffold, a stiff hydrogel is formed, cooperatively stabilized by dopamine/DTEc donor-acceptor interactions and by duplex nucleic acids. The cyclic and reversible formation and dissociation of the supramolecular donor-acceptor interactions, through light-induced photoisomerization of DTE, or via oxidation and subsequent reduction of the dopamine sites, leads to hydrogels of switchable stiffness. Another system introduces a stimuli-responsive hydrogel triggered by one of three alternative signals. The stiff, multi-triggered hydrogel consists of CMC chains cross-linked by dopamine/DTEc donor-acceptor interactions, and by supramolecular K+-stabilized G-quadruplexes. The G-quadruplexes are reversibly separated in the presence of 18-crown-6 ether and reformed upon the addition of K+. The stiff hydrogel undergoes reversible transitions between high-stiffness and low-stiffness states triggered by light, redox agents, or K+/crown ether. The hybrid donor-acceptor/G-quadruplex cross-linked hydrogel shows shape-memory and self-healing features. By using three different triggers and two alternative memory-codes, e.g., the dopamine/DTEc or the K+-stabilized G-quadruplexes, the guided shape-memory function of the hydrogel matrices is demonstrated.

Cu2+ -Modified Metal-Organic Framework Nanoparticles: A Peroxidase-Mimicking Nanoenzyme.

The synthesis and characterization of UiO-type metal-organic framework nanoparticles (NMOFs) composed of Zr4+ ions bridged by 2,2'-bipyridine-5,5'-dicarboxylic acid ligands and the postmodification of the NMOFs with Cu2+ ions are described. The resulting Cu2+ -modified NMOFs, Cu2+ -NMOFs, exhibit peroxidase-like catalytic activities reflected by the catalyzed oxidation of Amplex-Red to the fluorescent Resorufin by H2 O2 , the catalyzed oxidation of dopamine to aminochrome by H2 O2 , and the catalyzed generation of chemiluminescence in the presence of luminol/H2 O2 . Also, the Cu2+ -NMOFs mimic NADH peroxidase functions and catalyze the oxidation of dihydronicotinamide adenine dinucleotide, NADH, to nicotinamide adenine dinucleotide, NAD+ , in the presence of H2 O2 . The Cu2+ -NMOFs-catalyzed generation of chemiluminescence in the presence of luminol/H2 O2 is used to develop a glucose sensor by monitoring the H2 O2 formed by the aerobic oxidation of glucose to gluconic acid in the presence of glucose oxidase. Furthermore, loading the Cu2+ -NMOFs with fluorescein and activating the catalyzed generation of chemiluminescence in the presence of luminol/H2 O2 yield an efficient chemiluminescence resonance energy transfer (CRET) process to the fluorescein reflected by the activation of the fluorescence of the dye (λ = 520 nm, CRET efficiency 35%).

DNA-Responsive SiO2 Nanoparticles, Metal-Organic Frameworks, and Microcapsules for Controlled Drug Release.

Recent advances addressing the development of stimuli-responsive nucleic acid (DNA)-functionalized micro/nanocarriers for the controlled release of drugs are presented. The DNA associated with the drug-loaded carriers acts as capping units that lock the drugs in the carriers. In the presence of appropriate triggers, the capping units are unlocked, resulting in the release of the drugs. Three types of DNA-modified carriers are discussed, including mesoporous SiO2 nanoparticles (MP SiO2 NPs), metal-organic framework nanoparticles (NMOFs) and micro/nanocapsules. The triggers to unlock the DNA gating units include pH, the dissociation of K+-stabilized G-quadruplexes in the presence of crown ethers, the catalytic dissociation of the capping units by enzymes or DNAzymes, the dissociation of capping units by the formation of aptamer-ligand complexes (particularly ligands acting as biomarkers for different diseases), and the use of light for the photochemical unlocking of the DNA gates. Different issues related to the targeting of the different drug-loaded carriers to cancer cells, the switchable ON/OFF release of the drug loads, and the selective cytotoxicity of the drug-loaded carriers toward cancer cells are discussed. Finally, the future perspectives of the stimuli-responsive DNA-based, drug-loaded micro/nanocarriers for future nanomedicine and, in particular, the development of autonomous sense-and-treat systems are addressed.

Mimicking Horseradish Peroxidase and NADH Peroxidase by Heterogeneous Cu2+-Modified Graphene Oxide Nanoparticles.

Cu2+-ion-modified graphene oxide nanoparticles, Cu2+-GO NPs, act as a heterogeneous catalyst mimicking functions of horseradish peroxidase, HRP, and of NADH peroxidase. The Cu2+-GO NPs catalyze the oxidation of dopamine to aminochrome by H2O2 and catalyze the generation of chemiluminescence in the presence of luminol and H2O2. The Cu2+-GO NPs provide an active material for the chemiluminescence detection of H2O2 and allow the probing of the activity of H2O2-generating oxidases and the detection of their substrates. This is exemplified with detecting glucose by the aerobic oxidation of glucose by glucose oxidase and the Cu2+-GO NP-stimulated chemiluminescence intensity generated by the H2O2 product. Similarly, the Cu2+-GO NPs catalyze the H2O2 oxidation of NADH to the biologically active NAD+ cofactor. This catalytic system allows its conjugation to biocatalytic transformations involving NAD+-dependent enzyme, as exemplified for the alcohol dehydrogenase-catalyzed oxidation of benzyl alcohol to benzoic acid through the Cu2+-GO NPs-catalyzed regeneration of NAD+.

Mimicking Peroxidase Activities with Prussian Blue Nanoparticles and Their Cyanometalate Structural Analogues.

Nanoparticles composed of Prussian Blue, PB, and the cyanometalate structural analogues, CuFe, FeCoFe, and FeCo, are examined as inorganic clusters that mimic the functions of peroxidases. PB acts as a superior catalyst for the oxidation of dopamine to aminochrome by H2O2. The oxidation of dopamine by H2O2 in the presence of PB is 6-fold faster than in the presence of CuFe. The cluster FeCo does not catalyze the oxidation of dopamine to aminochrome. The most efficient catalyst for the generation of chemiluminescence by the oxidation of luminol by H2O2 is, however, FeCo, and PB lacks any catalytic activity toward the generation of chemiluminescence. The order of catalyzed chemiluminescence generation is FeCo ≫ CuFe > FeCoFe. The clusters PB, CuFe, FeCoFe, and FeCo mimic the functions of NADH peroxidase. The catalyzed oxidation of NADH by H2O2 to form NAD+ follows the order PB ≫ CuFe ∼ FeCoFe, FeCo. The efficient generation of chemiluminescence by the FeCo-catalyzed oxidation of luminol by H2O2 is used to develop a glucose sensor. The aerobic oxidation of glucose in the presence of glucose oxidase, GOx, yields gluconic acid and H2O2. The chemiluminescence intensities formed by the GOx-generated H2O2 relate to the concentration of glucose, thus providing a quantitative readout signal for the concentrations of glucose.

Stress response of Salmo salar (Linnaeus 1758) when heavily infested by Caligus rogercresseyi (Boxshall & Bravo 2000) copepodids.

The year-round presence of ovigerous females of the parasite Caligus rogercresseyi in the fish farms of southern Chile results in a continuous source of the copepodid (infestive) stage of this louse. The short generation time in spring-summer could lead to high abundances of this copepodid, potentially leading to high infestation levels for fish. Knowing how heavy lice infestations affect Salmo salar can help determine how to time antiparasitic treatments so as to both minimize the treatment impact and reduce lice infestation levels for fish. This study aimed to describe the effects of high infestations of the copepodid stage of C. rogercresseyi on the physiology of S. salar. Two groups of S. salar were used: an infested group (75 copepodids per fish) and a control group (not infested). Sixty-five days after the first infestation, the infested fish group was re-infested at an infestation pressure of 200 copepodids per fish. Sampling was done prior to and following the second infestation, at 56 and 67 days (the latter 2 days following the second infestation). Several physiological variables were measured: cortisol (primary stress response) and glucose, proteins, amino acids, triglycerides, lactate, osmolality levels, and number and diameter of skin mucous cells (secondary stress responses). The plasma cortisol, glucose, and triglyceride levels were altered in the heavily infested fish, as was the diameter of skin mucous cells. These results suggest that heavy infestations of C. rogercresseyi lead to an acute stress response, metabolic reorganization, and increased mucus production in S. salar under heavy infestation conditions.

[The role of gut microbiota in the regulation of the immune response]. / Rol de la microbiota gastrointestinal en la regulación de la respuesta inmune.

The gastrointestinal tract hosts around 10(14) bacterial microorganisms, in a constantly growing density from the stomach to the distal colon. This microbiota is composed by more than 500 species of bacteria, which are quickly acquired after birth, fairly stable during the host’s life, and essential for human homeostasis. These bacteria have important functions, such as stimulating the immune system, protecting the host from invading bacteria and viruses, and improving digestion, especially of complex carbohydrates. Also, the gut microbiota interacts directly with the immune system. However, the interaction of the intestinal epithelium and its microbiota with the immune system has yet to be fully understood. Secretory immunoglobulin A, produced by the plasma cells in Peyer’s patches and in the lamina propria, maintains non-invasive commensal bacteria and neutralize invasive pathogens. Dendritic cells migrate from the lamina propria of the secondary lymphoid organs to regulate gut immunity. They also have a key role maintaining luminal IgA and inducing the growth of regulatory T cells. Dendritic cells supervise the gut microenvironment too, keeping an immunological equilibrium and tolerance. The importance of the gut microbiota in regulating the immune system lies mostly in the homeostasis-or positive equilibrium. Thus, many diseases are a consequence of poor interactions or a loss of this equilibrium.