Colorimetric determination of ofloxacin using unmodified aptamers and the aggregation of gold nanoparticles.

A colorimetric method is presented for the determination of the antibiotic ofloxacin (OFL) in aqueous solution. It is based on the use of an aptamer and gold nanoparticles (AuNPs). In the absence of OFL, the AuNPs are wrapped by the aptamer and maintain dispersed even at the high NaCl concentrations. The solution with colloidally dispersed AuNPs remains red and has an absorption peak at 520 nm. In the presence of OFL, it will bind to the aptamer which is then released from the AuNPs. Hence, AuNPs will aggregate in the salt solution, and color gradually turns to blue, with a new absorption peak at 650 nm. This convenient and specific colorimetric assay for OFL has a linear response in the 20 to 400 nM OFL concentration range and a 3.4 nM detection limit. The method has a large application potential for OFL detection in environmental and biological samples. Graphical abstract Schematic of a sensitive and simple colorimetric aptasensor for ofloxacin (OFL) detection in tap water and synthesic urine. The assay is based on the salt-induced aggregation of gold nanoparticles which results in a color change from red to purple.

[Discussion of new classification of epididymal malformation in cryptorchidism of children].

OBJECTIVES: To discuss the new classification of epididymal malformation in cryptorchidism. METHODS: One hundred and fifty-three boys who were two to four year old underwent orchidopexy for cryptorchidism and 144 hydroceles who were two to eight year old were enrolled into control. Based on the observation of the status between testis and epididymia, the length of epididymis and the configuration of epididymis as well as spermaduct, we divided epididymal malformations in cryptorchidism into three types. Type I: obstruction of sperm transport, including I A, I B and I C; Type II: possible obstruction of sperm transport, defined by II A and II B; Type III: no obstruction of sperm transport, classified into III A and III B. RESULTS: There were 47 (23.4%) out of 201 undescended testes with malformation of epididymides and 16 (10.3%) out of 155 testes in the control(P < 0.05). 11 of 48 cases of bilateral cryptorchidism had the same malformations, with 2 cases of type IB, 2 of IC, 1 of II A, 4 of III A and 2 of IV B underwent orchidopexy or orchiectomy. CONCLUSIONS: These data showed that the incidence of epididymal abnormalities in cryptorchidism was higher than that in the hydroceles and it's not essential to have orchiectomy unlimitedly to serious epididymal abnormalities.