An antifouling polydopamine-based fluorescent aptasensor for determination of arginine kinase

Simple yet efficient detection methods for food allergens are in urgent need to help people avoid the risks imposed by allergenic food.In this work,a polydopamine(PDA)-based fluorescent aptasensor was developed to detect arginine kinase(AK),one of the major allergens in shellfish.The aptamer towards AK was firstly selected via systematic evolution of ligands by exponential enrichment method and labeled with fluorescein amidite(FAM)to build a fluorescence resonance energy transfer(FRET)system with PDA particles.Polyethylene glycol(PEG)was employed to construct an antifouling surface for the aptasensor to eliminate food matrix interferences.With the presence of AK,the PDA-based aptasensor exhibited elevated fluorescent signals as the FAM-labeled aptamer bound to AK and detached from the PDA particles.The aptasensor showed great stability and resistance to nonspecific interference of background proteins and had a limit of detection(LOD)of 0.298μg/mL.The proposed aptasensor was further proved to be feasible for quantitative analysis of AK in nine species of shrimps and five commercial processed products,which indicated its high potential in tracing the presence of AK in complex aquatic products.

Enhanced biohydrogen generation from organic wastewater containing NH^(+)_(4)by phototrophic bacteria Rhodobacter sphaeroides AR-3

NH^(+)_(4)is typically an inhibitor to hydrogen production from organic wastewater by photo-bacteria.In this experiment,biohydrogen generation with wild-type anoxygenic phototrophic bacterium Rhodobacter sphaeroideswas found to be sensitive to NH^(+)_(4)due to the significant inhibition of NH^(+)_(4)to its nitrogenase.In order to avoid the inhibition of NH^(+)_(4)to biohydrogen generation by R.sphaeroides,a glutamine auxotrophic mutant R.sphaeroides AR-3 was obtained by mutagenizing with ethyl methane sulfonate.The AR-3 mutant could generate biohydrogen efficiently in the hydrogen production medium with a higher NH^(+)_(4)concentration,because the inhibition of NH^(+)_(4)to nitrogenase of AR-3 was released.Under suitable conditions,AR-3 effectively produced biohydrogen from tofu wastewater,which normally contains 50–60 mg/L NH^(+)_(4),with an average generation rate of 14.2 mL/L$h.This generation rate was increased by more than 100%compared with that from wild-type R.sphaeroides.