Detection Of Toxoplasma Gondii And Schistosoma Japonicum Eggs With Magnetic Nanoparticle Probes Under-dark-field Microscopy

Toxoplasma gondii(T.gondii),as a common zoonotic parasite,can infect all warm blooded animals.Patients with low immunity may have lymphadenopathy or toxoplasmosis.Infection during pregnancy can cause serious damage to the fetus,such as fetal deformity,abortion or stillbirth.Schistosoma japonicum(S.japonicum)is the most famous zoonotic parasite in China.It can infect all mammals,damage the immune system,nervous system and digestive system,and eventually cause excessive loss of nutrition and death.Since the founding of the people's Republic of China,the number of patients with schistosomiasis has reached more than 12 million,which seriously threatens the public health and safety of our people and causes great economic losses to our animal husbandry every year.At present,the detection methods of T.gondii and Sjaponicum are mainly divided into pathogenic detection,immunological detection and molecular biological detection.These traditional detection methods have many defects,such as low sensitivity,cumbersome detection process,time-consuming and laborious,need expensive experimental instruments,can not meet the needs of grassroots workers in the field of rapid detection.Therefore,this study attempts to use the magnetic nanoparticle probe dark field microscopy to detect T.gondii and Sjaponicum.The detection process is simple,fast,high sensitivity and low requirements.In this study,firstly,the magnetic nanoparticles modified with protein A were incubated with the antibody of the target parasite to prepare the probe.Then,the probe and sample solution were mixed and vibrated at room temperature for 30 min,and the composite formed by the probe and parasite was pulled through the magnetic frame.After washing and re suspending,the samples were observed under the dark field microscope.Finally,the detection limit of the method is determined by sensitivity experiment,and the feasibility of the method in clinical detection is determined by animal experiment.The results showed that the probe was firmly attached to the surface of the body and diffracted golden light in dark field,which made the outline of the body clear to the naked eye.T.gondii showed golden crescent shape,and S.japonicum egg showed golden oval shape.The detection limit of T.gondii can reach 10000/ml,which is the same as that of PCR.The detection limit of S.japonicum eggs can reach 1000/ml.The target pathogens were successfully detected by this method in animal experiments.The magnetic nanoparticle probe dark field microscopy method has a good detection effect on T.gondii and S.japonicum eggs.The detection process is simple and fast,with high sensitivity and specificity,and it is suitable for grass-roots detection.