An electrochemical microbiosensor for DNA has been fabricated based on new acrylic microspheres modified with reactive N-acryloxysuccinimide (NAS) functional groups. Hydrophobic poly(n-butylacrylate-N-acryloxysuccinimide) microspheres were synthesized in an emulsion form with a simple one-step photopolymerization technique. Aminated DNA probe was attached to the succinimde functional group of the acrylic microspheres via covalent bonding. The hybridization of the immobilized DNA probe with the complementary DNA was studied by differential pulse voltametry using anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) as the electroactive hybridization label. The influences of many factors such as duration of DNA probe immobilization and hybridization, pH, type of ions, buffer concentrations, ionic strength, operational temperature and non-complementary DNA on the biosensor performance were evaluated. Under optimized conditions, the DNA microbiosensor demonstrated a linear response range to target DNA over a wide concentration range of 1.0 × 10−16 and 1.0 × 10−8 M with a lower limit of detection (LOD) of 9.46 × 10−17 M (R2 = 0.97). This DNA microbiosensor showed good reproducibility with 2.84% RSD (relative standard deviation) (n = 3). Application of the NAS-modified acrylic microspheres in the construction of DNA microbiosensor had improved the overall analytical performance of the resultant DNA microbiosensor when compared with other reported DNA biosensors using other nano-materials for membranes and microspheres as DNA immobilization matrices.
New acrylic microspheres were synthesised by photopolymerisation where the succinimide functional group was incorporated during the microsphere preparation. An optical biosensor for urea based on reflectance transduction with a large linear response range to urea was successfully developed using this material. The biosensor utilized succinimide-modified acrylic microspheres immobilized with a Nile blue chromoionophore (ETH 5294) for optical detection and urease enzyme was immobilized on the surface of the microspheres via the succinimide groups. No leaching of the enzyme or chromoionophore was observed. Hydrolysis of the urea by urease changes the pH and leads to a color change of the immobilized chromoionophore. When the color change was monitored by reflectance spectrophotometry, the linear response range of the biosensor to urea was from 0.01 to 1,000 mM (R2 = 0.97) with a limit of detection of 9.97 μM. The biosensor response showed good reproducibility (relative standard deviation = 1.43%, n = 5) with no interference by major cations such as Na+, K+, NH4+ and Mg2+. The use of reflectance as a transduction method led to a large linear response range that is better than that of many urea biosensors based on other optical transduction methods.
Ammonia analysis based on complexing ammonia with Cu2+ ions by UV-Vis spectrophotometry. This research aims to obtain uptake at the maximum wavelength of the copper-ammonia complex, optimum conditions and validation of UV-Vis spectrophotometry. The reaction between Cu2+ ions which are blue with ammonia colorless occur in solution to form complex compounds [Cu(NH3)4]2+ dark blue, the maximum absorbance is obtained at a wavelength of 615 nm. Optimization of the ammonia complexing the Cu2+ ions provide optimum conditions a solution of Cu2+ concentrations of 0.01 M in ammonia concentration of 0.04 M, pH 7, and the optimum time to form a complex occurred in the 30th minute and complex compounds can be stable for 90 minutes (± 1 hours 30 minutes). The analytical method validation ammonia using Cu2+ ions provide linear regression equation y = 4,772 x + 0.333 with R2 = 0.989 ammonia concentration range of 0.003 M to 0.08 M; LOD 0.01 M; LOQ 0.04 M; % RSD = 1.32%; and% recovery = 102.03%. The concentration of ammonia in the wastewater sample application obtained the ammonia concentration of 0.04 M. Based on the results of the validation, Ammonia solution with Cu2+ ion as a complex used for the determination of ammonia levels by UV-Vis spectrophotometry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.