Polypyrrole-palladium nanocomposite as a high-efficiency transducer for thrombin detection with liposomes as a label.

Sensitive and selective determination of protein biomarkers with high accuracy often remains a great challenge due to their existence in the human body at an exceptionally low concentration level. Therefore, sensing mechanisms that are easy to use, simple, and capable of accurate quantification of analyte are still in development to detect biomarkers at a low concentration level. To meet this end, we demonstrated a methodology to detect thrombin in serum at low concentration levels using polypyrrole (PPy)-palladium (Pd)nanoparticle-based hybrid transducers using liposomes encapsulated redox marker as a label. The morphology of Ppy-Pd composites was characterized by scanning electron microscopy, and the hybrid structure provided excellent binding and detection platform for thrombin detection in both buffer and serum solutions. For quantitative measurement of thrombin in PBS and serum, the change in current was monitored using differential pulse voltammetry, and the calculated limit of quantification (LOQ) and limit of detection (LOD) for the linear segment (0.1-1000 nM of thrombin) were 1.1 pM and 0.3 pM, in serum, respectively. The sensors also exhibited good stability and excellent selectivity towards the detection of thrombin, and thus make it a strong candidate for adopting its sensing applications in biomarker detection technologies.

Highly Sensitive Electrochemical Sensor for Diagnosis of Diabetic Ketoacidosis (DKA) by Measuring Ketone Bodies in Urine.

In this report, we present an enzyme deposited Au electrode for an electrochemical measurement of acetylacetic acid (AcAc) in urine. The electrode has an immobilized layer of a mixture of D-ß-hydroxybutyrate dehydrogenase (HBDH) and nicotinamide adenine dinucleotide (NADH) as sensing material to investigate its electroanalytical properties by means of cyclic voltammetry (CV). The modified electrodes are used for the detection of AcAc and present a linear current increase when the AcAc concentration increases. The electrode presents a limit of detection (LOD) of 6.25 mg/dL in the range of 6.25-100 mg/dL for investigation of clinical relevance. Finally, the electrode was evaluated using 20 patient samples. The measured results of urine ketone by the developed electrode were compared with the clinical results from a commercial kit, and the analysis showed good agreement. The proposed electrode was demonstrated to be a very promising platform as a miniaturized electrochemical analyzer for point-of-care monitoring of the critical biochemical parameters such as urine ketone.

Dimeric-serotonin bivalent ligands induced gold nanoparticle aggregation for highly sensitive and selective serotonin biosensor.

Chemically modulating monoamine neurotransmitter serotonin undergoes a physiological reaction of enzyme intermediated peroxidation to reconstruct dimeric self-assembled complex. A standard bivalent ligand approach dimeric serotonin increases structural and functional scaffolding with recognition-binding sites that are fundamentally more friendly than monovalent binding sites. Dimerization reaction accelerates the catalytic activity of one-electron oxidation at the C(4) position of serotonin to generate dual phenolic radicals in the presence of horseradish (HRP) and hydrogen peroxide (H2O2). Herein, we suggest the dimeric serotonin-based colorimetric assay, which presents a new rapid, sensitive, selective, and quantitative visualization. The dimeric serotonin possesses the capability to recognize intermolecular interaction units that cause aggregation scaffold of gold nanoparticles (GNPs), providing inexpensive and straightforward analytical needs. As a proof of visual and spectral analysis, peroxidative dimeric serotonin demonstrated sensitive and robust results. The calorimetric method enables highly sensitive detection of serotonin in phosphate buffer, and in human serum samples at nanomolar levels with a LOD of 2.6 nM and 2.81 nM, respectively, and the sensor possesses a dynamic range of 100-300 nM in buffer condition. Also, as proof of concept, visible color imaging of immunosensors which is appropriate for fast visible testing at detection limits as low as 2.90 nM concentration.

Functional analysis of desVIII homologues involved in glycosylation of macrolide antibiotics by interspecies complementation.

The DesVIII is an auxiliary protein which enhances the transfer of TDP-d-desosamine catalyzed by DesVII glycosyltransferase in the biosynthesis of macrolide antibiotics, neomethymycin, methymycin and pikromycin, in Streptomyces venezuelae ATCC 15439. Homologues of the desVIII gene are present in a number of aminosugar-containing antibiotic biosynthetic gene clusters including eryCII from the erythromycin producer Saccharopolyspora erythraea, oleP1 from the oleandomycin producer Streptomyces antibioticus, dnrQ from the doxorubicin producer Streptomyces peucetius, and tylMIII from the tylosin producer Streptomyces fradiae. In order to gain further insight into the function of these DesVIII homologues, interspecies complementation experiments were carried out by expressing each gene in a desVIII deletion mutant strain of S. venezuelae. Complementation by expressing EryCII, OleP1, and DnrQ in this mutant strain restored the production of glycosylated macrolides to an approximate level of 66%, 26% and 26%, respectively, compared to self-complementation by DesVIII. However, expression of TylMIII did not restore the antibiotic production. These results suggest that the DesVIII homologues (except for TylMIII) can functionally replace the native DesVIII for glycosylation to proceed in vivo and their functions are similar in acting as glycosyltransferase auxiliary proteins. The requirement of glycosyltransferase auxiliary protein seems to be more widespread in polyketide biosynthetic pathways than previously known.