title: The effect of fish matrix on the enzyme-linked immunosorbent assay of antibiotics.
abstract: BACKGROUND
  The matrix effect is considered to be a problem in the immunoassay of foodstuffs. However, information on the interference from aquatic products, as well as the mechanism involved, is very limited. In this study, using three flatfishes (Scophthalmus maximus, Paralichthys olivaceus and Cymoglossus robustus) as samples, the effect of the fish matrix on the competitive indirect enzyme-linked immunosorbent assay (ci-ELISA) of antibiotic (norfloxacin) residues was investigated. The mechanism of the observed matrix effect is also preliminarily discussed.
  
  
  RESULTS
  Within the working range of the calibration curves, a significant (P = 0.05) but irregular variation in the inhibition ratio was observed in the presence of fish extracts. Further experiments revealed that such a matrix effect could be caused by some water-soluble fish proteins with a wide range of molecular weight (from below 14.4 kDa to about 116.0 kDa), and the ions from fish muscles may also contribute to the interference. The results of western blotting indicated that some fish protein components might effectively bind with antibody reagents used.
  
  
  CONCLUSIONS
  Significant interference in the immunoassay of norfloxacin was observed in the presence of fish matrix. Some proteins and ions were demonstrated to contribute to the matrix effect investigated. Although the detailed mechanism is still unclear, the non-specific interaction between fish proteins and immunoglobulin G (IgG) or horseradish peroxidase (HRP) labelled IgG was assumed to be an important source of the matrix effect in immunoassays.
authors.affiliation: Food Safety Laboratory, Ocean University of China, Qingdao, 266003, China.
authors.forename: Xiudan
authors.initials: X
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Jianxin
authors.initials: J
authors.lastname: Sui
authors.forename: Limin
authors.initials: L
authors.lastname: Cao
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D015153:Blotting, Western; D004032:Diet; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D029941:Fish Proteins / Q000737:chemistry*; D005399:Fishes; D005506:Food Contamination / Q000032:analysis*; D006735:Horseradish Peroxidase; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry; D007202:Indicators and Reagents / Q000737:chemistry; D007477:Ions / Q000737:chemistry*; D008970:Molecular Weight; D009132:Muscles; D009643:Norfloxacin / Q000032:analysis; D011485:Protein Binding; D017747:Seafood; D012995:Solubility
chemical_list: D000900:Anti-Bacterial Agents; D029941:Fish Proteins; D007074:Immunoglobulin G; D007202:Indicators and Reagents; D007477:Ions; D006735:Horseradish Peroxidase; D009643:Norfloxacin