Bioconjugation of nanozyme and natural enzyme to enable a one-step cascade reaction for the detection of metabolites.

Nanozyme, with enzyme-mimicking activity and excellent stability, has attracted extensive attention. However, some inherent disadvantages, including poor dispersion, low selectivity, and insufficient peroxidase-like activity, still limit its further development. Therefore, an innovative bioconjugation of a nanozyme and natural enzyme was conducted. In the presence of graphene oxide (GO), histidine magnetic nanoparticles (H-Fe3O4) were first synthesized by a solvothermal method. The GO-supported H-Fe3O4 (GO@H-Fe3O4) exhibited superior dispersity and biocompatibility because GO was the carrier and possessed outstanding peroxidase-like activity because of the introduction of histidine. Furthermore, the mechanism of the peroxidase-like activity of GO@H-Fe3O4 was the generation of •OH. Uric acid oxidase (UAO) was selected as the model natural enzyme and covalently linked to GO@H-Fe3O4 with hydrophilic poly(ethylene glycol) as a linker. UAO could specifically catalyze the oxidation of uric acid (UA) to generate H2O2, and subsequently, the newly produced H2O2 oxidized the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue ox-TMB under the catalysis of GO@H-Fe3O4. Based on the above cascade reaction, the GO@H-Fe3O4-linked UAO (GHFU) and GO@H-Fe3O4-linked ChOx (GHFC) were used for the detection of UA in serum samples and cholesterol (CS) in milk, respectively. The method based on GHFU exhibited a wide detection range (5-800 µM) and a low detection limit (1.5 µM) for UA, and the method based on GHFC exhibited a wide detection range (4-400 µM) and a low detection limit (1.13 µM) for CS. These results demonstrated that the proposed strategy had great potential in the field of clinical detection and food safety.

Evaluation of erectile function after urethral reconstruction: a prospective study.

We conducted a prospective study of erectile dysfunction (ED) after urethral reconstructive surgery, using the 5-item International Index of Erectile Function (IIEF-5), the Sexual Life Quality Questionnaire (SLQQ) and the Quality of Life Questionnaire (QoLQ). Between January 2003 and July 2007, 125 male patients with urethral strictures underwent urethroplasty, and pre- and post-surgery erectile function was assessed using these three questionnaires. A formula to predict the probability of ED after urethroplasty was derived. At 3 months post-operatively, there was a significant decrease in IIEF-5 (16.57 +/- 7.98) and SLQQ scores (28.71 +/- 14.84) compared with pre-operative scores (P < 0.05). However, the IIEF-5 scores rebounded at 6 months post-operatively (17.22 +/- 8.41). Logistical regression analysis showed that the location of the urethral stricture, the recurrence of strictures and the choice of surgical technique were predictive of the post-operative occurrence of ED. This study identified the clinical risk factors for ED after urethroplasty. Posterior urethral stricture and end-to-end anastomosis were found to have a strong relationship with erectile function. The logistical model derived in this study may be applied to clinical decision algorithms for patients with urethral strictures.