Effect of in vitro digestion on bioactive compounds, antioxidant and antimicrobial activities of coffee (Coffea arabica L.) pulp aqueous extract.

Effect of in vitro digestion on bioactive compounds, biological activities of coffee pulp extract (CPE) against pathogens and a probiotic (Lactobacillus acidophilus TISTR 1338) was investigated. Total phenolic compound (TPC), chlorogenic acid (CGA), caffeine (CF), total monomeric anthocyanin (TMA), antioxidant and antimicrobial activities of the CPE were determined before and after digestion. After the digestion, the TPC, CGA and CF decreased 7.9, 31.7 and 50.0%, dry weight (dw), respectively. The antioxidant activity decreased 22.6% (DPPH) and 12.4% (FRAP). The CPE inhibited Escherichia coli TISTR 780 and Staphylococcus aureus TISTR 1466 at 150 and 200 mg/mL, respectively. Both CPE and the digested CPE had no effect on the tested probiotics. These results suggest that bioactive compounds of CPE may degrade during in vitro digestion, consequently the antioxidant and antimicrobial properties. Therefore, CPE could be a potential natural antimicrobial for food industry with no effect on the probiotics.

Label-free as-grown double wall carbon nanotubes bundles for Salmonella typhimurium immunoassay.

BACKGROUND: A label-free immunosensor from as-grown double wall carbon nanotubes (DW) bundles was developed for detecting Salmonella typhimurium. The immunosensor was fabricated by using the as-grown DW bundles as an electrode material with an anti-Salmonella impregnated on the surface. The immunosensor was electrochemically characterized by cyclic voltammetry. The working potential (100, 200, 300 and 400 mV vs. Ag/AgCl) and the anti-Salmonella concentration (10, 25, 50, 75, and 100 µg/mL) at the electrode were subsequently optimized. Then, chronoamperometry was used with the optimum potential of 100 mV vs. Ag/AgCl) and the optimum impregnated anti-Salmonella of 10 µg/mL to detect S. typhimurium cells (0-10(9) CFU/mL). RESULTS: The DW immunosensor exhibited a detection range of 10(2) to 10(7) CFU/mL for the bacteria with a limit of detection of 8.9 CFU/mL according to the IUPAC recommendation. The electrode also showed specificity to S. typhimurium but no current response to Escherichia coli. CONCLUSIONS: These findings suggest that the use of a label-free DW immunosensor is promising for detecting S. typhimurium.

Ultralong aligned multi-walled carbon nanotube for electrochemical sensing.

We have investigated electrochemical sensing properties of electrodes fabricated with ultralong aligned multi-walled carbon nanotube (MWNT) bundles synthesized using water-assisted chemical vapor deposition on aluminum (Al) and iron (Fe) coated silicon wafer with ethylene and argon/hydrogen gas as carbon source and buffer gas respectively. Cyclic voltammograms performed on these electrodes show diffusion-controlled-reversible reaction. The dominance of radial diffusion mass transport at these electrodes was also indicated by sigmoidal-shaped voltammograms obtained at various scan rates. These electrodes were able to sense very low concentration of ascorbic acid (approximately 0.7 microM) and dopamine (approximately 1.87 microM), two model species often used in electro-analysis. The excellent electrochemical properties along with good single species detection ability suggest that these MWNTs are promising electrode materials for developing very sensitive chemical and/or biological sensors.