Direct electron transfer of Horseradish peroxidase on porous structure of screen-printed electrode.

Disposable hydrogen peroxide biosensor was developed based on the direct electron transfer of horseradish peroxidase (HRP) on porous screen-printed carbon electrodes. Conventional screen-printing process was manually performed to fabricate the planar carbon electrodes, which were endowed with porous surfaces especially after anodizing pretreatment. The cyclic voltammetry experiment indicated a pair of stable and well-defined redox peaks with a formal potential of -0.33 V. And the formal potential was pH-dependent, having a slope of -55.2 mV/pH which indicated one electron transfer. The heterogeneous electron transfer rate constant k(s) was estimated to be 13.28+/-4.80s(-1). Additionally, the sensitivity was 143.3 mAM(-1)cm(-2) and the linear range was from 5.98 to 35.36 microM. In conclusion, the present work achieved the direct electron transfer of HRP on screen-printed electrodes without any promoters. The porous structure of screen-printed carbon electrodes facilitated the direct electron transfer between the active sites of HRP and the electrodes due to large amounts of conductive sites available on the surface for contacting with enzyme molecules. Moreover, the proposed biosensor could be mass-produced at low price, promising for commercial application.

[A comparative study of the expression of ras oncogenic protein P21 and oncofetal protein AFP, CEA in human hepatocellular carcinoma (HCC)].

The expression of P21, AFP and CEA were detected in human hepatocellular carcinoma and its surrounding nontumor tissues by immunohistochemical staining on serial sections. The significance of AFP and P21 in HCC auxiliary diagnosis was discussed. The results are as follows: (1) AFP and P21 were more closely related with HCC than CEA. Both AFP and P21 were expressed simultaneously in more than half the cases. The distribution of these two antigens in HCC was similar. (2) The positive incidence of AFP in tumor tissues was higher than that in surrounding nontumor tissues, but vice versa for P21. Based on the results of this study, we regard that AFP is a relatively specific marker of HCC, better than P21 in auxiliary diagnosis of HCC. The hepatocytes which surround the tumor and can simultaneously express AFP and P21, are likely to be precancerous cells which have been initiated and possess the ability of neoplastic growth but lack phenotype transformation.

Effect of Anordrin on serum levels of sex hormone binding globulin, caeruloplasmin and ovarian function.

Ten doses of 7.5 mg Anordrin were administered on alternate days from day 5 of the menstrual cycle to 20 women. Serum concentrations of both SHBG and CP were significantly increased after the fourth dose but the increases were minor compared to those produced by ethynyloestradiol. Two weeks after stopping Anordrin, serum concentrations of the proteins were still elevated in most women. Ovarian activity was studied in 8 women; serum oestradiol and progesterone concentrations indicated that ovulation occurred at the normal time in three women but was delayed for two weeks or more in the remaining five. The findings suggest that in humans, Anordrin acts as a weak oestrogen and may also have antioestrogenic activity.