| Nanomaterials have been widely used in biomedical fields because of unique physical and chemical properties.For example,a variety of testing methods and imaging techniques based on nanomaterials have been clinically applied,especially graphenic nanomaterials.Magnetic materials has been paid more and more attention in clinical magnetic resonance imaging.The diagnosis and treatment of disease also become an important subject in the field of medical and scientific research.Gastric disease has become the fourth major disease that plagues people at present.The infection of Helicobacter pylori(H.pylori)is susceptible to the related diseases of the stomach.At present,the mainly detective methods of Helicobacter pylori consist of invasive ones and non-invasive ones.Invasive methods can directly detect the bacteria,but it can easily ignores some small lesions.At the same time,endoscopy can also bring pains to patients and increase the rejection of patients.Non-invasive methods are not straightforward enough to be susceptible to various conditions and result in false positives.In this paper,we compared the stability of MGNs with SPIONs,when they are exposed to acidic condition.Based on the resistance of MGNs to acid,we applied MGNs to H.pylori detection and in vivo imaging.In this research,we achieved noninvasive detection of Helicobacter pylori in vivo for the first time.The details are as follows:(1)The preparation,characterization and acid resistance of MGNs and SPIONs were inveatigated in Chapter 2.By CVD method,the outer layer of the magnetic nucleus FeCo is coated with graphene nanoshells.This magnetic nanoparticles not only have the Raman signal of graphene,but also can carry out MR imaging.At the same time,the shell of graphene can protect the magnetic core from the external acidic environment,and increase the stability and acid resistance of particles.The magnetic core(FeCo)can be used as a good magnetic resonance imaging contrast agent.The SPIONs was synthesized by coprecipitation method,and the nanoparticles were also characterized.The stability of these two nano materials were compared by their UV-vis spectrum,the changes of T2 relaxation time,TEM,and the change of hydrodynamic radius and surface charge in different acidic conditions.(2)The third chapter studies the comparison of the MGNs and SPIONs stability under the condition of gastric acid mimic and the MR imaging in vivo.First,we prepare gastric acid mimic with different pH in accordance with USP to create a real environment near the human body.We compared the stability of MGNs and SPIONs in complex environment of gastric acid miminc,by observing the changes of UV-Vis,T2 relaxation time and MR imaging.Afterwards,nanoparticles were used in more complex environments such as cellular and organizational levels.Finally,nanoparticles were applied in vivo MR imaging,and we observed the imaging effect of different time.(3)In the fourth chapter,we synthesised a new B-PEG to target H.pylori.The B-PEG was obtained after separation and purification after the amide reaction of 4-carboxylic acid and C18-(PEG)12-NH2.The B-PEG adsorbed onto the MGN surface by ultrasound,and then MGN@B-PEG was obtained.This universal target molecule has higher capture rate,lower detection limit and better sensitivity,and it also cannot be influenced by acidic conditions.After incubation H.pylori with MGN@B-PEG,Raman spectroscopy was used to characterize the detection of graphene,and the magnetic core of MGN@B-PEG was used for MR imaging.Then we infection BALB/c with H.pylori to establish the mice model,and the infection was verified by gram staining and urine enzyme activity.This method can be used to detect H.pylori or other bacteria with B-PEG and the combination with MGNs can also make the system in complex environments.This sensor has a big promissing in noninvasive detection H.pylori in vivo with MR imaging in the future. |
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