Detection Of Biogenic Amines And Biothiols By Lignocellulose-based Fluorescent Chemosensor

The content of specific molecules in food can be used as important indexes to monitor the quality and safety food.Biogenic amines(BAs)are important biomarkers for evaluating the freshness and quality of food.Biothiols have an effect on the flavor,color and texture of food.They can have positive effects on human body when consumed in moderation,but excessive intake will have adverse toxicological effects.Therefore,accurate detection of BAs and biothiols in food can provide valuable reference for controlling the quality and safety of food.Among the commonly detection methods,fluorescent chemosensor has the advantages of high sensitivity,good selectivity,convenient operation and real-time monitoring,and shows desirable application prospects in the detection of BAs and biothiols.In this study,cellulose and lignin were separated from poplar sawdust by a simple and sustainable method of separation,conversion and utilization of lignocellulose.The lignin was used as carbon-based material to prepare porous carbon and fluorescent carbon dots(CDs).The cellulose was used as matrix material to combine with other fluorescent materials to construct paper-based fluorescent sensing labels,so as to realize portable and visual detection of BAs and biothiols.The specific work is as follows:(1)The lignin-based porous carbon microspheres(LPCMs)were prepared by carbonization and activation of lignin isolated from lignocellulose,and further interacted with fluorescein 5-isothiocyanate(5-FITC)to construct a novel “turn off-on” fluorescent probe.The fluorescence of 5-FITC was quenched in the presence of LPCMs.After the addition of BAs,5-FITC was released from the surface of LPCMs,resulting in fluorescence recovery.The probe achieved a sensitive and rapid response to BAs with LOD as low as 1.678 μM.Furthermore,the separated cellulose was used as the substrate material to prepare fluorescent test strips,which realized the sensitive and visual detection of BAs.(2)Fluorescent carbon dots(CDs)were prepared by using lignin to construct a ratiometric fluorescent probe for the detection of BAs.The performance and mechanism of ratiometric fluorescent probe for BAs detection were studied,and the limitation of single-emission fluorescent probes was reduced by self-calibration ability.This ratiometric fluorescent probe had a sensitive response to BAs.The fluorescence of the system changed from blue to red with the increase of BAs concentration,and showed a good linear relationship with LOD as low as0.045 μM.In addition,cellulose nanofibers(CNFs)were used as the substrate to prepare smart p H-responsive CDs/CNFs fluorescent film,and realized real-time and visual detection of BAs.(3)A Cu I-based CPs with green fluorescence was designed,synthesized and applied for selective detection of biothiols under the simulated physiological condition.The green fluorescence of CPs was originated from the charge transfer between metal and ligand.Based on the strong thiophilicity of Cu,the pyridine N of ligand was replaced by sulfhydryl group of biothiols,resulting in the change of structure and fluorescence properties of CPs.This probe could achieve selective and sensitive detection of Cys,GSH and Hcy with LOD of 1.013 μM,1.051 μM and 1.034 μM,respectively.The sensing properties of the probe were systematically studied and then the probe was applied to detect biothiols in food and biological samples,which showed good detection performance.Furthermore,a CPs/CNFs flexible composite film was prepared and realized visual detection of biothiols.