Glutamate oxidase biosensor based on mixed ceria and titania nanoparticles for the detection of glutamate in hypoxic environments.

We report on the design and development of a glutamate oxidase (GmOx) microelectrode for measuring l-glutamic acid (GluA) in oxygen-depleted conditions, which is based on the oxygen storage and release capacity of cerium oxides. To fabricate the biosensor, a nanocomposite of oxygen-rich ceria and titania nanoparticles dispersed within a semi-permeable chitosan membrane was co-immobilized with the enzyme GmOx on the surface of a Pt microelectrode. The oxygen delivery capacity of the ceria nanoparticles embedded in a biocompatible chitosan matrix facilitated enzyme stabilization and operation in oxygen free conditions. GluA was measured by amperometry at a working potential of 0.6 V vs Ag/AgCl. Detection limits of 0.594 µM and 0.493 µM and a sensitivity of 793 pA/µM (RSD 3.49%, n=5) and 395 pA/µM (RSD 2.48%, n=5) were recorded in oxygenated and deoxygenated conditions, with response times of 2s and 5s, respectively. The biosensor had good operational stability and selectivity against common interfering substances. Operation of the biosensor was tested in cerebrospinal fluid. Preliminary in vivo recording in Sprague-Dawley rats to monitor GluA in the cortex during cerebral ischemia and reperfusion demonstrate a potential application of the biosensor in hypoxic conditions. This method provides a solution to ensure functionality of oxidoreductase enzymes in oxygen-free environments.

Multifunctional biomagnetic capsules for easy removal of phenol and bisphenol A.

This paper reports fabrication, optimization and characterization of multifunctional biocapsules with immobilized enzyme using a layer-by-layer configuration and their application for removal of phenol and bisphenol A (BPA). The method is based on the combined use of enzymatic oxidation of the BPA and subsequent binding of the reaction product onto a chitosan core biopolymer. This platform has multiple functions including: (1) enzymatic degradation of BPA, (2) adsorption of the degraded compound within the core material, (3) colorimetric quantification and (4) magnetic capabilities. We examined various configurations of core/shell structures of alginate and chitosan and determined the stability and the optimum conditions in which these structures provide the most effective removal capacity. The amount of BPA that can be removed per capsule is 5.6 ppm while phenol can be removed up to 10 ppm per capsule within 15 h.

Toxicity and developmental defects of different sizes and shape nickel nanoparticles in zebrafish.

Metallic nanoparticles such as nickel are used in catalytic sensing, and electronic applications, but health and environmental affects have not been fully investigated. While some metal nanoparticles result in toxicity, it is also important to determine whether nanoparticles of the same metal but of different size and shape changes toxicity. Three different size nickel nanoparticle (Ni NPs) of 30, 60, and 100 nm and larger particle clusters of aggregated 60 nm entities with a dendritic structure were synthesized and exposed to zebrafish embryos assessing mortality and developmental defects. Ni NPs exposure was compared to soluble nickel salts. All three 30, 60, and 100 nm Ni NPs are equal to or less toxic than soluble nickel while dendritic clusters were more toxic. With each Ni NP exposure, thinning of the intestinal epithelium first occurs around the LD10 continuing into the LD50. LD50 exposure also results in skeletal muscle fiber separation. Exposure to soluble nickel does not cause intestinal defects while skeletal muscle separation occurs at concentrations well over LD50. These results suggest that configuration of nanoparticles may affect toxicity more than size and defects from Ni NPs exposure occur by different biological mechanisms than soluble nickel.

JEM Spotlight: Applications of advanced nanomaterials for environmental monitoring.

Rapid progress of the nanotechnology and advanced nanomaterials production offers significant opportunities for a wide range of applications for detection and remediation of a broad range of environmental contaminants. The convergence of analytical techniques and nanotechnology provides attractive possibilities for development of miniaturized, rapid, ultrasensitive and inexpensive methods for in situ and field-based environmental monitoring devices. This review provides an overview of the various nanoparticles and nanostructures used for this purpose, their integration into functional analytical devices, applications as electrode materials and gas sensing nanoprobes, in biosensors and as capture probes in immunomagnetic separations. Relevant, specific examples of nanomaterials-based chemical and biological sensors with applications in environmental monitoring are discussed.

Enzyme-functionalized mesoporous silica for bioanalytical applications.

The unique properties of mesoporous silica materials (MPs) have attracted substantial interest for use as enzyme-immobilization matrices. These features include high surface area, chemical, thermal, and mechanical stability, highly uniform pore distribution and tunable pore size, high adsorption capacity, and an ordered porous network for free diffusion of substrates and reaction products. Research demonstrated that enzymes encapsulated or entrapped in MPs retain their biocatalytic activity and are more stable than enzymes in solution. This review discusses recent advances in the study and use of mesoporous silica for enzyme immobilization and application in biosensor technology. Different types of MPs, their morphological and structural characteristics, and strategies used for their functionalization with enzymes are discussed. Finally, prospective and potential benefits of these materials for bioanalytical applications and biosensor technology are also presented.

Ductopapillary apocrine carcinoma of the eyelid metastatic to the parotid gland: report of a case diagnosed by fine-needle aspiration biopsy.

Ductopapillary apocrine carcinoma (DPAC) of the eyelid is a rare malignant neoplasm in the periocular region. The relative rarity of this tumor is a diagnostic challenge to the cytopathologist, especially when present as a metastatic lesion to an intraparotid lymph node, where the differential diagnosis includes primary parotid neoplasms, as well as various other metastatic malignancies. There are only a few reported cases of recurrent and metastatic DPAC of the eyelid, and to our knowledge, metastatic DPAC diagnosed by fine-needle aspiration biopsy (FNAB) has not been described. We report a case of a 65-year-old African-American male with a history of ductopapillary apocrine adenocarcinoma of the eyelid, diagnosed 6 weeks ago now presenting with a recurrence in the same area. Magnetic resonance imaging of the head and neck revealed an intraparotid mass also. FNAB of the parotid mass showed a well-differentiated papillary adenocarcinoma with a cystic component, similar to a previously excised ductopapillary apocrine adenocarcinoma of the eyelid.

Mixed ceria-based metal oxides biosensor for operation in oxygen restrictive environments.

The unique catalytic, electrochemical, and oxygen storage properties of ceria and mixed ceria/titania hybrid composites were used to fabricate a new type of electrochemical enzyme biosensor. These materials provided increased analytical performance and possibilities for operation in oxygen-free conditions of an oxidase enzyme biosensor using tyrosinase as a model example. The investigation of the enzymatic reaction in the presence and absence of oxygen was first carried out using cyclic voltammetry. The results were used to identify the role of each metal oxide in the immobilization matrix and fabricate a simple amperometric tyrosinase biosensor for the detection of phenol and dopamine. The biosensor was optimized and characterized with respect to response time, detection limit, linear concentration range, sensitivity, and kinetic parameters. The detection limit for phenol was in the nanomolar range, with a detection limit of 9.0 x 10(-9) M and a sensitivity of 86 mA M(-1) in the presence of oxygen and of 5.6 x 10(-9) M and a sensitivity of 65 mA M(-1) in the absence of oxygen. The optimized biosensor also showed selective determination of the neurotransmitter dopamine with a detection limit of 3.4 x 10(-8) M and a sensitivity of 14.9 mA M(-1) in the presence of oxygen and of 4.2 x 10(-8) M and 14.8 mA M(-1) in the absence of oxygen. This strategy shows promise for increasing the sensitivity of oxidase enzyme sensors and provides opportunities for operation in oxygen limited conditions. It can also be extended for the development of other enzyme biosensors.