title: Blocking nonspecific adsorption of native food-borne microorganisms by immunomagnetic beads with iota-carrageenan.
abstract: We present herein the partitioning characteristics of anti-Salmonella and anti-Escherichia coli O157 immunomagnetic beads (IMB) with respect to the nonspecific adsorption of several nontarget food-borne organisms with and without an assortment of well-known blocking agents, such as casein, which have been shown to be useful in other immunochemical applications. We found several common food-borne organisms that strongly interacted with both types of IMB, especially with anti-Salmonella form (av DeltaG0=-20 +/- 4 kJ mol(-1)) even in the presence of casein [1% (w/v): DeltaG0=-18 +/- 3 kJ mol(-1); DeltaDeltaG0 approximately -2 kJ mol(-1)]. However, when one of the most problematic organisms (a native K12-like E. coli isolate; DeltaG0=-19 +/- 2 kJ mol(-1)) was tested for nonspecific binding in the presence of iota-carrageenan (0.03-0.05%), there was an average decline of ca. 90% in the equilibrium capture efficiency xi (DeltaG0=-11 +/- 4 kJ mol(-1); DeltaDeltaG0 approximately -8 kJ mol(-1)). Other anionic polysaccharides (0.1% kappa-carrageenan and polygalacturonic acid) had no significant effect (av DeltaG0=-19 +/- 1 kJ mol(-1); DeltaDeltaG0 approximately 0 kJ mol(-1)). Varying iota-carrageenan from 0% to 0.02% resulted in xi significantly diminishing from 0.69 (e.g., 69% of the cells captured; DeltaG0=-19 +/- 3 kJ mol(-1)) to 0.05 (DeltaG0=-11 +/- 2 kJ mol(-1); DeltaDeltaG0 approximately -9 kJ mol(-1)) at about 0.03% iota-carrageenan where xi leveled off. An optimum blocking ability was achieved with 0.04% iota-carrageenan suspended in 100 mM phosphate buffer. We also demonstrated that the utilization of iota-carrageenan as a blocking agent causes no great loss in the IMBs capture efficiency with respect to the capture of its target organisms, various salmonellae.
authors.affiliation: Microbial Biophysics and Residue Chemistry, ARS, Eastern Regional Research Center, US Department of Agriculture, 600 E Mermaid Lane, Wyndmoor, PA 19038, USA. pirwin@errc.ars.usda.gov
authors.forename: Peter
authors.initials: P
authors.lastname: Irwin
authors.forename: Andrew
authors.initials: A
authors.lastname: Gehring
authors.forename: Shu-I
authors.initials: SI
authors.lastname: Tu
authors.forename: Chin-Yi
authors.initials: CY
authors.lastname: Chen
mesh_terms: D000327:Adsorption / Q000187:drug effects; D002021:Buffers; D002351:Carrageenan / Q000737:chemistry* / Q000494:pharmacology; D004926:Escherichia coli / Q000302:isolation & purification; D005502:Food; D005516:Food Microbiology; D018189:Immunomagnetic Separation / Q000379:methods*; D012475:Salmonella / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D012964:Sodium / Q000737:chemistry; D013045:Species Specificity
chemical_list: D002021:Buffers; D002351:Carrageenan; D012964:Sodium