An Amphiphilic-ligand-modified Gold Nanoflower Probe For Enhancing The Stability Of Lateral Flow Immunoassays For Zearalenone Detection In Dried Distillers' Grains

Immunochromatographic assay(ICA)has been known as one of the most popular point-of-care techniques due to its unique merits of rapidity,simplicity and low cost.Traditional colloidal gold based ICA always suffers from its relative low sensitivity owing to its insufficient brightness owing to insufficient brightness of the generally used signal reporter of 20?40 nm spherical gold nanoparticles.In addition,for some complex matrices,such as tissue samples,feed samples and some powder matrix samples,it is still required a,complicated pre-treatment processes to improve the reliability of strip test,which greatly restrict its detection convenience.Compared with spherical gold nanoparticles,gold nanoflowers(AuNFs)with similar size present much larger molar extinction coefficient and stronger signal intensity,thus can be used as a novel signal reporter to improve the detection performance of ICA.The complex matrix of DDGS in this study will seriously affect the sensitivity,detection linearity,accuracy and precision of the Tr-ZEN-LFA test strip,thus leading to incorrect detection events.After modified with a functional ligand,the AuNFs can greatly improve the anti-interference ability and stability in complex matrix.In this paper,an amphiphilic ligand capped AuNFs was proposed as a novel reporter of ICA to improve its reliability and accuracy for zearalenone(ZEN)detection in distillers' dried grains solubles(DDGS).The amphiphilic ligand consists of a thiol-terminated hydrophobic alkane chain,a tetra(ethylene glycol)unit,and a terminal carboxyl group.The novel AuNF probe(N-AuNF-Abs)was prepared by coupling the amino group of anti-ZEN antibodies with the AuNF carboxyl group via an amido covalent linkage.For comparison,a traditional AuNF probe(Tr-AuNF-Abs)was prepared by labeling antibodies on the surface of citrate capped AuNFs via an electrostatic adsorption method.In this study,the two AuNF probes were compared in the tolerance of against NaCl content and pH of solution.Then two corresponding ZEN-LFA test trips were constructed,and compared in tolerance against NaCl content and pH,analytical performance for detecting buffer samples and real DDGS samples(sensitivity,robustness,reproducibility),and shelf life.The results show that N-AuNFs,N-AuNF-Abs and N-LFA showed excellent tolerance against NaCl content and pH of the sample solution.The resultant N-LFA afforded a lower IC50 value(15.97 ng/mL)for ZEN detection in phosphate buffered saline than that of the Tr-AuNF-mAb based LFA(Tr-LFA,31.06 ng/mL).The IC50 value of N-LFA in DDGS extract was 17.46 ng/mL which was almost the same as in buffer samples,whereas the Tr-LFA showed poor robustness and reproducibility in DDGS samples,resulting in a failed determination.The intra-and inter-assays of N-LFA for ZEN-spiked DDGS samples indicated that the average recoveries ranged from 93.0%to 125.9%(coefficients of variation ranged from 2.8%to 21.9%).These results indicated that the N-LFA strip exhibits a good robustness and an acceptable accuracy for ZEN quantitative detection in complex DDGS samples.In accelerated aging studies,N-LFA showed a longer shelf life(5 years)than that of Tr-LFA(1 year).In summary,the proposed method provided a novel strategy to prepare a super-stable probe for enhancing the detection performance of LFA for small molecular detection in complex sample matrices such as DDGS.