Alterations in serum levels of trace elements in tuberculosis and HIV infections.

OBJECTIVE: To evaluate serum concentrations of trace elements in tuberculosis (TB) patients with or with out human immunodeficiency virus (HIV) coinfection before and after anti-TB chemotherapy. SUBJECTS: A total of 155 TB patients, 74 of which were coinfected with HIV, and 31 healthy controls from Gondar, Ethiopia. METHODS: Serum levels of copper, zinc, selenium and iron were determined using an inductively coupled plasma mass spectrometer from all subjects at baseline and from 44 TB patients (22 with HIV coinfection) at the end of an intensive phase of anti-TB chemotherapy. RESULTS: Compared with the control group, the concentrations of iron, zinc and selenium were significantly lower (P<0.05) while that of copper and copper/zinc ratio was significantly higher (P<0.05) in the serum of TB patients. TB patients with HIV coinfection had significantly lower serum zinc and selenium concentrations and significantly higher copper/zinc ratio compared to that in TB patients without HIV coinfection (P<0.05). The serum concentration of zinc had significantly increased at the end of intensive phase of anti-TB chemotherapy in patients without HIV coinfection (P<0.05). An increase in serum selenium level was observed in TB patients with or without HIV coinfection after therapy. On the contrary, serum copper concentration and copper/zinc ratio declined significantly after anti-TB chemotherapy irrespective of HIV serostatus (P<0.05). CONCLUSIONS: The results indicate that TB patients have altered profile of trace elements in their sera. This warrants the need for further investigations so that strategies for trace elements supplementation can be planned in addition to their potential as diagnostic parameters in monitoring responses to anti-TB chemotherapy.

Evaluation of osmium(II) complexes as electron transfer mediators accessible for amperometric glucose sensors.

In order to lower the redox potentials of Os(III/II) complexes, the mixed ligand complexes of Os(II) were synthesized. The redox potentials of Os(III/II) complexes could be lowered by the use of 4,4'-dimethyl-2,2'-bipyridine (dmbpy), imidazole (Him) or its derivatives, and chloride ion as ligands, e.g., values of the redox (formal) potentials of 628 mV vs. Ag/AgCl for [Os(bpy)3]3+/2+ (bpy: 2,2'-bipyridine) and -6 mV for [OsCl(Him)(dmbpy)2]2+/+ were given in deaerated 0.1 mol dm-3 phosphate buffer (pH 7.0). The evaluation of Os(II) complexes as electron transfer mediators accessible for amperometric glucose sensors was examined according to the determination of the redox potentials of Os(III/II) complexes and the second-order rate constants for electron transfer between glucose oxidase (GOx) in reduced form and the Os(III) complex. Although the Os(II) complexes with lower redox potentials tended to decrease the second-order rate constants ks, the ks values for the majority of Os(II) complexes synthesized in this study were greater than that for ferrocenecarboxylic acid. Acceleration of the electron-transfer reaction is attributable to the hydrogen bonding and/or the electrostatic interaction between the Os(II) complexes and GOx. It may be consequently concluded that the mixed ligand complexes of Os(II) with bpy (dmbpy), Him (its derivatives), and Cl- can act as more efficient electron transfer mediators for the fabrication of amperometric glucose sensors.

DNA electrochemical sensor using osmium complex.

The [Os(DA-bpy)2DPPZ]2+ complex (DPPZ; dipyrido [a:2',3'-c] phenazine, DA-bpy; 4,4'-diamino-2,2'-bipyridine) had a lower half-wave potential (E1/2) of 147 mV (vs. Ag|AgCl) and higher binding affinity with DNA (binding constant, K = 3.1 x 10(7) M-1) than those of DPPZ type metal complexes. With a single stranded DNA (ssDNA) immobilized gold electrode, the hybridization signal (delta I) of the [Os(DA-bpy)2DPPZ]2+ complex was linear in the concentration range of 1.0 pg ml-1-0.12 microgram ml-1 for the targeted DNA with a regression coefficient of 0.999. The detection limit was 0.1 pg ml-1. The 400 bp yAL3 gene was also detected with good sensitivity and selectivity using the [Os(DA-bpy)2DPPZ]2+ complex.

Electrochemical characterization and DNA-binding property of dipyridophenazine complexes of osmium (II).

Novel dipyridophenazine (DPPZ) complexes of osmium (II), [Os(L)2(DPPZ)]2+ [L = 2,2'-bipyridyl (bpy)(1), 4,4'-diamino-2,2'-bipyridyl (DA-bpy)(2), 4,4'-dimethyl-2,2'-bipyridyl(DM-bpy)(3), and 4,4'-dicarboxyl-2,2'-bipyridyl (DC-bpy)(4)] have been synthesized and characterized. The DNA-binding properties of the complexes were studied by electrochemical methods. As the results, complex 2 shows higher affinity to DNA than other osmium complexes. The binding constant, K of complex 2 to calf thymus DNA has been determined to be 2.3 x 10(7) M-1 by normal pulse voltammetry (NPV).

DNA hybridization sensor utilizing [Os(5,6-dmphen)3]2+ by square wave voltammetry.

DNA hybridization detection utilizing [Os(5,6-dmphen)3]2+ (tris(5,6-dimethyl-phenanthroline) osmium(II/III)) as hybridization indicator was studied, because [Os(5,6-dmphen)3]2+ has the most largest association constant (K2+) and high current density in osmium methyl substituted phenanthroline complexes. As the result, target DNA could be detected selectively ranging from 6.9 x 10(-10) to 6.9 x 10(-5) g/mL using square wave voltammetry.

Interaction between tris(bpyl)osmium(II/III) complex and immobilized DNA on a carbon electrode.

Interaction between (bipyridyl) osmium (II/III) complex and immobilized DNA on a carbon paste electrode was studied using cyclic voltammetry and chronocoulometry. The complex specifically interacted with immobilized double strand DNA (20 mer).

Recognition of DNA sequence utilizing osmium complex by amperometric technique.

Recognition of DNA sequence utilizing tris-(bipyridyl)osmium(II/III) complex was studied, because the osmium complex interacted with double strand DNA specifically. In this result, double strand DNA (12-20 mer) could be recognized selectivity.

Determination of cholesterol and cholesterol ester with novel enzyme microsensors.

Enzyme microsensors using cholesterol oxidase (EC 1.1.3.6) and cholesterol esterase (EC 3.1.1.13) were developed for measuring cholesterol and cholesterol ester. The platinum microsensors (platinum diameter, 50 microns) were etched in hot aqua regia to create a cavity at their tip. A porous composite material prepared from acetylene black and Teflon emulsion was packed into this cavity and the redox mediator [Os(bpy)3](PF6)2 was monitored by cyclic voltammetry in the potential range of 200-900 mV. The microsensors were dipped overnight in buffer solution containing the desired enzyme to immobilize it on the tip by adsorption. Calibration curves for measurements of cholesterol and cholesterol ester, the effects of pH, temperature, and concomitant compounds, the lifetime of the microsensors, and their availability for measuring cholesterol and cholesterol ester in urine were examined. Under optimal conditions, the response of the sensors was linear in concentration ranges of 5 microM-0.47 mM cholesterol and 2 microM-1.00 mM cholesterol ester.