Gold nanoparticles obtained by Au(III) reduction with Sn(II): Preparation and electrocatalytic properties in oxidation of reducing agents

Gold colloid solutions were prepared by reduction of Au(III) with Sn(II) in both acidic (HCl) and alkaline (carbonate) media, and characterized by electron microscopy, X-ray diffraction and light absorption spectra. Depending on the colloid preparation conditions, metal particles of 5-30 nm in size were obtained. Light absorption spectra of the Au colloid solutions contain an absorption band at 500-600 nm, typical of small gold particles. According to XRD data, colloid particles contain the metallic Au and SnO₂ phases. The colloid formation rate and colloid solution stability depend on solution pH; the alkaline colloid solutions are formed more slowly and are more stable. The gold nanoparticles adsorbed on the dielectrics surface were found to initiate the electroless copper deposition process. The glassy carbon (GC) electrode modified by Au nanoparticles (200-900 ng cm⁻² Au) was found to be an electrocatalyst for dimethylamine borane, borohydride, hydrazine, and formaldehyde oxidation in alkaline solutions. The activity of the reducers can be arranged as follows: DMAB > NaBH₄ > N₂H₄ > CH₂O.     

Joint: cartilage

Chemosensitivity ofN-methyl-N-nitrosourea-induced rat mammary tumours treated with 5-fluorouracil at a dose of 100 mg kg⁻¹ i.p. was assessed by using diffusion-weighted¹H-MRS to measure the average diffusion coefficient (ADC) of water in the tumour tissue. ADC measurements prior to any therapy correlated positively with necrotic fraction. Tumours with low initial ADC (<0.95×10⁹ m² s⁻¹) showed an increase in ADC 7 days after treatment, whereas tumours with a high initial ADC (>1.2×10⁹ m² s⁻¹) showed a decrease. All tumours decreased significantly in volume (P<0.05) 2, 5 and 7 days after treatment. At day 7 post-treatment, tumours with a high pre-treatment ADC started to regrow. The initial ADC value, as well as changes after treatment predict tumour chemosensitivity, which could be clinically relevant.