Surface Engineered Antifouling Optomagnetic Nanoparticles For Bi-modal Targeted Imaging Of Pancreatic Cancer

Pancreatic cancer has a high mortality rate, which is generally related to the initialdiagnosis coming at late stage disease combined with a lack of effective diagnostictechniques. Over the past few years, molecular imaging, which can be defined as the invivo characterization and measurement of biologic processes at the molecular and genelevels, has developed rapidly and allows diagnosing pancreatic cancer more early andspecifically. Magnetic resonance imaging (MRI) is widely used for molecular imagingbecause of the high spatial resolution. But the low sensitivity has limited its use in the earlydiagnosis of cancer. Fluorescence imaging has a high sensitivity，but with a low spatialresolution and a high background. Thus bi-modal imaging, which combined the advantagesof the MRI and the fluorescence imaging, becomes the hotspot of research. The preparationof the probe is the study center. This paper focuses on the preparation and characterizationof a novel optomagnetic nanoparticles, and discusses its application in bimodal targetedimaging of pancreatic cancer.The main content of this paper can be divided into two parts:(1) design a novelmodification method to preparing bi-modal imaging agent with excellent colloidal stability,biocompatibility, and minimal nonspecific binding;(2) evaluate the bio-safty andpharmacokinetic of the as-synthesized imaging agent, and study the bimodal targetedimaging of pancreatic cancer both in vitro and in vivo.The first part is to explore a novel method for modifying the nanoparticles. Tosynthesis hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs), high thermaldecomposition is used with Fe(acac)3as precursor and oleic acid, oleylamine,1, 2-hexadecanediol and benzyl ether as surfactant. Upon characterized by TEM, XRD andVSM, the as-synthesized hydrophobic SPIONs have good appearance, uniform size andnone residual magnetism. Then we used two methods to modify the nanoparticles. The firstmethod is based on amphiphilic modify using hydrophilic PMAO to replace thehydrophobic groups through reverse phase rotary evaporation. After the ring openingpolymerization of2,2’-(Ethylenedioxy)bis(ethylamine) and PMAO, enough carboxyl andamino groups are obtained for latter coupling reaction with Cy5and antibody. The secondmethod is ligand exchange, using Nitrosonium tetrafluoroborate (NOBF4) to treat thehydrophobic SPIONs first and then using bovine serum albumin (BSA) to cap vialigand-exchange. The characterizations such as TEM, colloidal stability and relaxivity testindicate that the as-synthesized SPIONs by the above methods both have goodwater-solubility, excellent colloidal stability and high relaxivity.The second part is to examine the bio-safty of BSA·SPIONs using the3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) method andhematoxylin and eosin-stained (HE) histology analysis. The result indicates hypotoxicity ofBSA·SPIONs against normal L02cells and has good biocompatibility. Mice post-injectedwith BSA·SPIONs at different intervals were used for biodistribution studies. All micewere sacrificed after complete anesthesia, and major organs were collected. The organswere pulverized, digested by nitric acid and filtered for determination of Fe. The resultsshow that the BSA·SPIONs are primarily taken up by liver, spleen and the large intestine.The concentration of Fe in the liver, spleen and large intestine reached a peak at12h afterinjection, and then decreased to normal levels gradually. When conjugated withNear-infrared (NIR) fluorescent dye and monoclonal antibody, the bimodalprobe--dyeBSA·SPION-mAb bioconjugates showed excellent targeting capability withminimal nonspecific binding in the bi-modal imaging in vitro and in vivo, presenting greatpromise in MRI/NIRF bimodal imaging.In summary, we have synthesized magnetic nanoparticles using two methods, whichexhibit good biocompatibility and stability. BSA·SPIONs is chosen for conjugating with NIR dye and antibody, the bio-safty and pharmacokinetic of the as-synthesized imagingprobe are studied. The bimodal imaging indicates the probe can be used for early detectionof tumor, promising for biomedical application in future.