Paula Díez

Glucose-triggered release using enzyme-gated mesoporous silica nanoparticles

A new gated nanodevice design able to control cargo delivery using glucose as a trigger and cyclodextrin-modified glucose oxidase as a capping agent is reported.

Supramolecular immobilization of xanthine oxidase on electropolymerized matrix of functionalized hybrid gold nanoparticles/single-walled carbon nanotubes for the preparation of electrochemical biosensors.

Glassy carbon electrodes modified with single-walled carbon nanotubes and a three-dimensional network of electropolymerized Au nanoparticles capped with 2-mercaptoethanesulfonic acid, p-aminothiophenol, and 1-adamantanethiol were used as hybrid electrochemical platforms for supramolecular immobilization of a synthesized artificial neoglycoenzyme of xanthine oxidase and β-cyclodextrin through host-guest interactions. The ensemble was further employed for the bioelectrochemical determination of xanthine. The biosensor showed fast amperometric response within 5 s and a linear behavior in the 50 nM to 9.5 μM xanthine concentration range with high sensitivity, 2.47 A/(M cm(2)), and very low detection limit of 40 nM. The stability of the biosensor was significantly improved and the interferences caused by ascorbic and uric acids were noticeably minimized by coating the electrode surface with a Nafion thin film.

Decorating carbon nanotubes with polyethylene glycol-coated magnetic nanoparticles for implementing highly sensitive enzyme biosensors

Superparamagnetic Fe3O4 nanoparticles were coated with (3-aminopropyl)triethoxysilane and further branched with monomethoxypolyethylene glycol chains. These nanoparticles were employed for the non-covalent surface modification of single walled carbon nanotubes, conferring them magnetic properties. This nanomaterial was employed to immobilize the enzyme xanthine oxidase in order to construct magnetically modified disposable gold screen-printed electrodes as bioelectrodes for the determination of xanthine. The electroanalytical properties of the biosensor were modulated by the nanomaterial composition, being optimal at a carbon nanotubes : magnetic nanoparticles ratio of 1 : 27. The resulting biosensor showed a linear dependence on the xanthine concentration in the 0.25–3.5 μM range with a fast amperometric response in 12 s. The biosensor also showed a noticeable high sensitivity of 1.31 A M−1 cm−2 and a very low detection limit of 60 nM, which can be compared advantageously with other biosensor designs for xanthine.

Decorating graphene oxide/nanogold with dextran-based polymer brushes for the construction of ultrasensitive electrochemical enzyme biosensors

A novel strategy was employed to prepare a water-soluble graphene derivative by using dextran-based polymer brushes as solubilizing agents. Graphene oxide was grafted with (3-mercaptopropyl) trimethoxysilane and further decorated with Au nanoparticles. This hybrid nanomaterial was then reduced and anchored with polysaccharide-based polymer brushes by chemisorption of an end-group thiolated dextran derivative on the Au nanoparticles. The resulting hybrid nonmaterial allowed highly stable aqueous dispersions to be obtained, which were used to coat glassy carbon electrodes for the preparation of a model tyrosinase electrochemical biosensor for catechol. The enzyme electrode showed excellent electroanalytical performance with fast response in about 5 s, a linear range of 100 pM-120 nM, a very high sensitivity of 45.9 A M-1 and a very low detection limit of 40 pM for catechol.

Supramolecular immobilization of redox enzymes on cyclodextrin-coated magnetic nanoparticles for biosensing applications.

Mono-6-formyl-β-cyclodextrin moieties were attached to (3-aminopropyl)triethoxysilane-coated superparamagnetic Fe(3)O(4) nanoparticles by reductive alkylation with NaBH(3)CN. The oligosaccharide-capped core-shell nanoparticles were employed as support for the supramolecular immobilization of two different adamantane-modified enzymes, tyrosinase and xanthine oxidase, through host-guest interactions. The enzyme-modified nanomaterial was further used to magnetically modify carbon paste electrodes for constructing amperometric biosensors toward cathecol and xanthine. The tyrosinase and xanthine oxidase based biosensors showed excellent electroanalytical behaviours, with linear ranges of 100 nM-12 μM cathecol and 5.0-120 μM xanthine, sensitivities of 12 mA/M and 130 mA/M, and low detection limits of 22 nM and 2.0 μM, respectively. The supramolecular nature of the immobilization approach was confirmed by electroanalytical methods.

Decoration of reduced graphene oxide with rhodium nanoparticles for the design of a sensitive electrochemical enzyme biosensor for 17β-estradiol

A novel nanocomposite material consisting of reduced graphene oxide/Rh nanoparticles was prepared by a one-pot reaction process. The strategy involved the simultaneous reduction of RhCl3 and graphene oxide with NaBH4 and the in situ deposition of the metal nanoparticles on the 2D carbon nanomaterial planar sheets. Glassy carbon electrode coated with this nanocomposite was employed as nanostructured support for the cross-linking of the enzyme laccase with glutaraldehyde to construct a voltammperometric biosensor for 17β-estradiol in the 0.9-11 pM range. The biosensor showed excellent analytical performance with high sensitivity of 25.7AµM-1cm-1, a very low detection limit of 0.54pM and high selectivity. The biosensor was applied to the rapid and successful determination of the hormone in spiked synthetic and real human urine samples.

Neoglycoenzyme-Gated Mesoporous Silica Nanoparticles: Toward the Design of Nanodevices for Pulsatile Programmed Sequential Delivery

We report herein the design of a stimulus-programmed pulsatile delivery system for sequential cargo release based on the use of a lactose-modified esterase as a capping agent in phenylboronic acid functionalized mesoporous silica nanoparticles. The dual-release mechanism was based on the distinct stability of the cyclic boronic acid esters formed with lactose residues and the long naturally occurring glycosylation chains in the modified neoglycoenzyme. Cargo delivery in succession was achieved using glucose and ethyl butyrate as triggers.

Seed-mediated growth of jack-shaped gold nanoparticles from cyclodextrin-coated gold nanospheres

Branched gold nanoparticles were prepared by a seed-mediated approach using per-6-thio-6-deoxy-β-cyclodextrin capped gold nanospheres as seeds and a growth medium similar to those commonly employed to prepare gold nanorods, containing AgNO3, ascorbic acid and cetyltrimethylammonium bromide. Novel jack-shaped gold nanoparticles (102-105 nm) were obtained at a specific range of Ag(+) ion concentrations (62-102 μM). The crystalline structure of these nanoparticles was confirmed by high-resolution transmission electron microscopy. The influence of the perthiolated β-cyclodextrin on the successful preparation of gold nanojacks was demonstrated. The jack-shaped gold nanoparticles showed strong absorption in the near infrared region and excellent catalytic activity for the electrochemical oxidation of H2O2.

Gold nanoparticles/silver-bipyridine hybrid nanobelts with tuned peroxidase-like activity

Gold nanoparticles-decorated silver-bipyridine coordination polymers with intrinsic peroxidase-like activity are reported. Both morphology and mimetic enzyme activity can be tuned by rational manipulation of the nanohybrid composition. The nanomaterial was used for the electrochemical determination of H2O2 and glucose.

Enzyme‐Controlled Nanodevice for Acetylcholine‐Triggered Cargo Delivery Based on Janus Au–Mesoporous Silica Nanoparticles

This work reports a new gated nanodevice for acetylcholine-triggered cargo delivery. We prepared and characterized Janus Au-mesoporous silica nanoparticles functionalized with acetylcholinesterase on the Au face and with supramolecular β-cyclodextrin:benzimidazole inclusion complexes as caps on the mesoporous silica face. The nanodevice is able to selectively deliver the cargo in the presence of acetylcholine via enzyme-mediated acetylcholine hydrolysis, locally lowering the pH and opening the supramolecular gate. Given the key role played by ACh and its relation with Parkinsons disease and other nervous system diseases, we believe that these findings could help design new therapeutic strategies.