Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring.

This article presents the fabrication and characterization of novel tattoo-based solid-contact ion-selective electrodes (ISEs) for non-invasive potentiometric monitoring of epidermal pH levels. The new fabrication approach combines commercially available temporary transfer tattoo paper with conventional screen printing and solid-contact polymer ISE methodologies. The resulting tattoo-based potentiometric sensors exhibit rapid and sensitive response to a wide range of pH changes with no carry-over effects. Furthermore, the tattoo ISE sensors endure repetitive mechanical deformation, which is a key requirement of wearable and epidermal sensors. The flexible and conformal nature of the tattoo sensors enable them to be mounted on nearly any exposed skin surface for real-time pH monitoring of the human perspiration, as illustrated from the response during a strenuous physical activity. The resulting tattoo-based ISE sensors offer considerable promise as wearable potentiometric sensors suitable for diverse applications.

Disposable immunochips for the detection of Legionella pneumophila using electrochemical impedance spectroscopy.

The rapid diagnosis of Legionellosis is crucial for the effective treatment of this disease. Currently, most clinical laboratories utilize rapid immunoassays that are sufficient for the detection of Legionella serogroup 1, but not other clinically relevant serogroups. In this report, the development of a disposable immunochip system is described in connection with electrochemical impedance spectroscopy and fluorescence microscopy. The immunochips were prepared by covalently immobilizing fluorophore-conjugated L. pneumophilaantibodies on Au chips. The analytical performance of the immunochips was optimized as a prescreening tool for L. pneumophila. The versatile immunochips described here can be easily adapted for the monitoring of all Legionella serogroups in clinical and environmental samples.

Electrochemical oxidation of benzothiazole dyes for monitoring amyloid formation related to the Alzheimer's disease.

Alzheimer's disease (AD) is associated with the formation and deposition of amyloid fibrils. A better understanding of the oligomeric intermediates on the pathway to fibrilization is highly desired, but efficient methods for their detection are lacking. We have studied the interfacial properties of amyloid peptides (Abeta-40 and Abeta-42) and the course of their aggregation in vitro in the presence of the benzothiazole dyes Thioflavin T (4-(3,6-dimethyl-1,3-benzothiazol-3-ium-2-yl)-N,N-dimethylaniline) chloride, ThT) and BTA-1 ([2-(4'-(methylamino)phenyl) benzothiazole]) using electrochemical techniques. The intercalative properties of these dyes between the beta-sheets of amyloids have been well-documented using fluorescence-based systems, but their electrochemistry is reported here for the first time. ThT is positively charged and water-soluble, whereas BTA-1 is neutral and hydrophobic. Immediate and significantly different electrochemical characteristics of these dyes were observed in the presence of amyloid peptides. A decrease of the BTA-1 oxidation signal was observed upon incubation with Abeta-40. Incubation of BTA-1 with Abeta-42 results in an increased rate of exponential decay, which was in agreement with the known rapid aggregation properties of Abeta-42. The aggregation of amyloid peptides with ThT resulted in an unexpected increase in signal after 24 h of incubation, consistent for both peptides. The results of the electrochemical trials were confirmed using simultaneous fluorescence analysis of the same incubated amyloid samples. The very early changes in the interfacial behavior of the amyloid peptides after the first few minutes of incubation were attributed to the fast oligomerization of the peptides with the disruption of the intercalative properties of the benzothiazole dyes between the beta-sheets. The subsequent changes in the electrochemical signals can be related to the onset of intercalation between the fibrils. Our results demonstrate the utility of electrochemical oxidation signals of the benzothiazole dyes as a new and simple tool for the investigation of amyloid formation related to the AD.

Electroanalysis of the interaction between (-)-epigallocatechin-3-gallate (EGCG) and amyloid-ß in the presence of copper.

The misfolding of amyloid-beta (Aß) peptide is one of the pathological hallmarks of Alzheimer's disease (AD). Polyphenols are strong antioxidants and metal chelators, with characteristics that are of beneficial therapeutic values for their development as candidates targeting neurodegenerative and metal-induced diseases. We have demonstrated here the electrochemical properties of a green tea component, (-)-epigallocatechin-3-gallate (EGCG), and its potent activity on Aß peptides. Characterization of early interactions (≤48 h) between EGCG and Aß was conducted using square wave voltammetry (SWV). The interaction of Cu(ii) ions with the Tyr-10 residue of Aß was shown to be affected by surrounding His residues. Morphological changes due to the binding of EGCG and Cu(II) were also elucidated using transmission electron microscopy (TEM). Electroanalytical techniques are promising for facilitating the investigation of metals and flavonoids in drug screening studies.

Identification of drug candidates which increase cytochrome c oxidase activity in deficient patient fibroblasts.

Cytochrome c oxidase (COX) activity reflects the expressed level of respiratory chain complexes, mtDNA levels, titer and mass of mitochondria. Activity is also indicative of the overall fitness of mt-transcription factors and the import, transcription and translation of mt-proteins. We have developed a high-throughput assay to measure COX activity using live cells to screen chemical libraries for compounds capable of increasing COX activity. These libraries have revealed four examples which elevated the activities of COX in NIH-3T3 fibroblasts and in fibroblasts from patients with COX defects independent of the peroxisome proliferator activated receptor family.