RESUMEN
To improve sensitivity of S. enterica serovar Typhimurium detection, multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) were combined and used as a label to amplify signal in a scanometric based assay. In this study, the MWCNTs/AuNPs nanocomposite was fabricated by directly assemble of Au(3+) to MWCNTs and allowed growing of AuNPs along the MWCNTs surface. This MWCNTs/AuNPs nanocomposite was then attached to anti-S. typhimurium antibody (MWCNTs/AuNPs/Ab(1)) and used as a detecting molecule. Upon binding to Salmonella, they were pre-concentrated by magenetic beads/antibody (MBs/Ab(2)) forming a sandwich immuno-complex which is later spotted on a nitrocellulose membrane coated slide. Silver reduction was applied to amplify signal. The detection limit of 42CFU/ml was achieved when 2% BSA was used as a blocking agent. Given different types of real samples testing, chicken broth was found to give lowest detection limit, followed by orange juice low fat and whole milk. Selectivity testing was performed by using Escherichia coli as interference and found slightly cross-reactivity which could be due to specificity of the Ab used. By virtue of using a slide for multi-samples spotting and a flatbed scanner for signal-read out acquisition, this scano-magneto immunoassay could enable low-cost detection as well as high throughput screening.
Asunto(s)
Técnicas Biosensibles/métodos , Análisis de los Alimentos/métodos , Microbiología de Alimentos , Oro/química , Nanopartículas/química , Nanotubos de Carbono/química , Salmonella typhimurium/aislamiento & purificación , Animales , Colodión/química , Microbiología de Alimentos/métodos , Humanos , Límite de Detección , Membranas Artificiales , Nanocompuestos/química , Oxidación-Reducción , Infecciones por Salmonella/diagnóstico , Infecciones por Salmonella/microbiologíaRESUMEN
Bioconjugate nanocapsules were fabricated by using polystyrene sulfonate (PSS) to encapsulate gold nanoparticles (AuNPs) bearing adsorbed horseradish peroxidase (HRP). The average size of nanocapsule was in a range 150-400 nm. The efficiency of the capsules to enhance signals in an immunoassay was demonstrated by using an enzyme linked immunosorbent assay (ELISA) to detect the food-borne pathogen -Listeria monocytogenes. The antibody adsorbed onto the PSS shell of the nanocapsules provided the recognition molecule. For a given quantity of antibody, the bioconjugate nanocapsules showed 30 times greater sensitivity and a shorter assay time (5 min) when compared to conventional ELISA using an HRP labelled antibody. This proof-of-concept encapsulation of HRP through PSS nanocapsules may pave the way for alternative signal enhancement strategies where sensitivity is a priority.