Immonbiosensor For The Detection Of Toxoplasma Godii-specific IgM Based On Grapheme Sheets And Magnetic Nanoparticles

Objective:Toxoplasmosis which infects a broad range of hosts including humanshas little clinical symptom in immunocompetent individuals.Toxoplasmosis infection during pregnancy can cause miscarriage,premature birth, or stillbirth, and lead to permanent neurological damage orvisual impairment in neonates. Therefore early diagnosis of activetoxoplasmosis in pregnant women can properly manage the risk to the fetusof a maternal infection, and more important, give an early prenataltreatment to prevent severe congenital infection.Toxoplasma gondii-specific IgM （Tg-IgM） can be foundapproximately14days after infection, therefore, the presence of Tg-IgM isa sign of acute or recent toxoplasmosis infection, and it also could be usedfor detecting intrauterine infection. The employed serological methodshave limitations such as complicated operation, low sensitivity, andnon-quantitative detection. In this research, a novel sandwich-type electrochemical immunosensorfor sensitive detection of Tg-IgM based on grapheme sheets （GS） and goldnanoparticles （AuNPs） with anti-IgM-HRP-Au-Fe₃O₄as detection labelwas constructed.Methods:1. Preparation of the anti-IgM-HRP-Au-Fe₃O₄as detection label:Au-Fe₃O₄nanoparticles was employed to modify anti-IgM-HRP moleculesfor the preparation of the detection label, which exhibited good superiormagnetic propertie and biocompatibility.2. A sandwich-type electrochemical immunosensor was constructedusing Nf-GS, polythionine, and AuNPs to yield a hybrid membranedeposited on a glass electrode. The immunosensor which based onsandwich immunoassay protocol was used for quantitative detection ofTg-IgM.3. Optimization of electrochemical conditions, such as pH of theworking solution, incubation time, incubation temperature, and theconcentration of H2O2.4. Evaluation of the immunosensor, such as the low detection limit,selectivity, reproducibility regeneration ability and stability.Results:1. The detection label was characterized by TEM and UV-vis. The SEM image of anti-IgM-HRP-Au-Fe₃O₄become indistinct, and the size ofthe nanoparticles was increased. anti-IgM-HRP and Au-Fe₃O₄both can beseen in the UV-vis absorption spectroscopy. Indicating the successfulpreparation of the detection label.2. The redox reaction on the surface of the immunosensor is adiffusion controllable redox process. The immunosensor can detect Tg-IgMin two linear ranges from0.0375to1.2AU mL^-1and from2.0to18AU/mL with a detection limit of0.016AU/mL （S/N=3）.3. The immunosensor exhibited good reproducibility, selectivity,regeneration ability and stability.Conclusions:In conclusion, GS exhibited rapid electron transportation and excellentelectrical conductivity in the preparation of immunosensor. In this research,Nf was used to improve the dispersion of GS, as well as enhanceimmunosensor stability. Functionalized GS with AuNPs in this researchcould increase the immobilized amount of biomolecules, which was due tothe large specific surface area and excellent biocompatibility of AuNPs.The application of Au-Fe₃O₄in the immunosensor could increaseimmunosensor sensitivity, and also provide a non-chemical damageregeneration method.