5xfad tg mouse model ( b6sjl - tg(appswfllon , psen1*m146l*l286v)6799vas ) ( jackson laboratories ) is bred on a non - transgenic background ( b6sjlf1 ) . hela is a human cervical cancer cell line ; nih/3t3s is a mouse embryonic fibroblast line ; hepg3 is from hepatocellular carcinoma ; raw264.7 is a mouse leukemic monocyte macrophage cell line . 16 nm magnetite nanoparticles were synthesized by decomposition of iron - oleate at 320c as described in an earlier report . 10.8 g of iron ( iii ) chloride hexahydrate and 36.5 g sodium oleate were dissolved in a mixture of 60 ml distilled water , 80 ml ethanol and 140 ml hexane and heated at 60c for 4 hr . the organic layer of the biphasic mixture becomes dark , indicating phase transfer of iron ( iii ) ions and formation of iron oleate complex . 18 g of iron oleate complex and 2.58 g of oleic acid were dissolved in 100 g of octadecene at room temperature and heated to 320c at a rate of 3.3c per minute . resulting nanoparticles are separated from the solution by addition of ethanol and ethyl acetate followed by centrifugation . to make the organic phase synthesized mns suitable for biological application we stabilized the mns using carboxylate terminated ligand with ndopa as an anchor . synthesis of carboxylate terminated ndopa ligand and functionalization of the mns was carried out according to the following protocol . tetraethylene diacide , n - hydroxysuccinimide ( nhs ) , n , n-dicyclohexylcarbodiimide ( dcc ) , ndopa hydrochloride and anhydrous sodium bicarbonate was dissolved in chloroform under argon atmosphere and stirred for 4 hr . hexane stabilized mns were added and stirred for another 24 hr . the precipitate formed was separated by magnet , dispersed in water and purified by dialysis . the conjugation of buffer stabilized mns with antibody was done using a conventional carboxyl - amine crosslinking method . we first activated the carboxyl terminated mns by sulfo - n - hydroxy succinimide ( snhs ) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide ( edc ) followed by incubation with corresponding antibody ( nu4 or igg1 , with or without fluorescent label ) overnight . conjugated mns were separated by magnet to remove excess reagent and antibody then re - dispersed in working media . conjugation efficiency was estimated using uv spectroscopy ( absorbance at 280 nm ) of the magnetically separated supernatant . of note , because both fluorophore and mns conjugation use carboxyl - amine crosslinking , fluorescent nu4 that has more than 2.5 mol fluorophore / mol antibody does not conjugate well to the mns . optimal concentration of fluorophore / nu4 is ~1.02.5 mol fluorophore / mol antibody for fluorescent - nu4mns preparation . mice were anesthetized with isoflurane and then placed on their backs with their heads positioned to maximize the residency time for the delivered material to remain on the olfactory surface . each naris was administered with 568-nu4 , nu4mns or non - immune iggmns ( 5 l / naris ) , using a sterile micropipette , slowly over a period of 1 min , keeping the opposite naris and mouth closed to allow complete aspiration of delivered material . a falcon tube containing the mns treated tissue samples was placed in a bruker pharmascan 7 t animal mri scanner . sample were imaged using a t2 * -weighted gradient echo ( gre ) flash pulse sequence 3-dimensional acquisition . the image resolution was 0.07 mm isotropic , with field - of - view ( fov ) 4.62cm/2.52cm/0.65 cm and image matrix ( mtx ) 700 pixels/385 pixels/100 pixels . the number of averages ( nex ) was 20 to improve the signal - to - noise ratio . following intranasal inoculation , the probe was allowed to distribute for 4 hours before mr imaging was performed according to imaging methodology described in mundt et al . t1 , t2 , and t2 * weighted mr images were acquired on a bruker biospec 7 t magnet , using a 25 mm rf quadrature coil . t1- and t2-weighted images provide anatomical guidance as well as some localization of the nu4mns and were acquired with a fat suppressed spin echo sequence ( rapid acquisition with relaxation enhancement , rare ) with the following parameters for t1-weighted ( tr=1000 ms , teeff=13.2 ms , rare factor 2 , number of excitations , nex=4 ) and for t2-weighted ( tr=3500 ms , teeff=58.5 ms , rare factor 4 , nex=4 ) . t2 * -weighted imaging provides more of the localization of the nu4mns as the iron causes local changes in magnetic susceptibility which t2 * weighted images can be sensitive to . a gradient echo sequence was used with the following parameters ( gradient echo fast imaging , gefi ; tr=1200 ms , te=5.6 ms , flip angle 35 and nex=4 ) . 5xfad tg mouse model ( b6sjl - tg(appswfllon , psen1*m146l*l286v)6799vas ) ( jackson laboratories ) is bred on a non - transgenic background ( b6sjlf1 ) . hela is a human cervical cancer cell line ; nih/3t3s is a mouse embryonic fibroblast line ; hepg3 is from hepatocellular carcinoma ; raw264.7 is a mouse leukemic monocyte macrophage cell line . 16 nm magnetite nanoparticles were synthesized by decomposition of iron - oleate at 320c as described in an earlier report . 10.8 g of iron ( iii ) chloride hexahydrate and 36.5 g sodium oleate were dissolved in a mixture of 60 ml distilled water , 80 ml ethanol and 140 ml hexane and heated at 60c for 4 hr . the organic layer of the biphasic mixture becomes dark , indicating phase transfer of iron ( iii ) ions and formation of iron oleate complex . 18 g of iron oleate complex and 2.58 g of oleic acid were dissolved in 100 g of octadecene at room temperature and heated to 320c at a rate of 3.3c per minute . resulting nanoparticles are separated from the solution by addition of ethanol and ethyl acetate followed by centrifugation . 10.8 g of iron ( iii ) chloride hexahydrate and 36.5 g sodium oleate were dissolved in a mixture of 60 ml distilled water , 80 ml ethanol and 140 ml hexane and heated at 60c for 4 hr . the organic layer of the biphasic mixture becomes dark , indicating phase transfer of iron ( iii ) ions and formation of iron oleate complex . 18 g of iron oleate complex and 2.58 g of oleic acid were dissolved in 100 g of octadecene at room temperature and heated to 320c at a rate of 3.3c per minute . resulting nanoparticles are separated from the solution by addition of ethanol and ethyl acetate followed by centrifugation . to make the organic phase synthesized mns suitable for biological application we stabilized the mns using carboxylate terminated ligand with ndopa as an anchor . synthesis of carboxylate terminated ndopa ligand and functionalization of the mns was carried out according to the following protocol . tetraethylene diacide , n - hydroxysuccinimide ( nhs ) , n , n-dicyclohexylcarbodiimide ( dcc ) , ndopa hydrochloride and anhydrous sodium bicarbonate was dissolved in chloroform under argon atmosphere and stirred for 4 hr . hexane stabilized mns were added and stirred for another 24 hr . the precipitate formed was separated by magnet , dispersed in water and purified by dialysis . the conjugation of buffer stabilized mns with antibody was done using a conventional carboxyl - amine crosslinking method . we first activated the carboxyl terminated mns by sulfo - n - hydroxy succinimide ( snhs ) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide ( edc ) followed by incubation with corresponding antibody ( nu4 or igg1 , with or without fluorescent label ) overnight . conjugated mns were separated by magnet to remove excess reagent and antibody then re - dispersed in working media . conjugation efficiency was estimated using uv spectroscopy ( absorbance at 280 nm ) of the magnetically separated supernatant . of note , because both fluorophore and mns conjugation use carboxyl - amine crosslinking , fluorescent nu4 that has more than 2.5 mol fluorophore / mol antibody does not conjugate well to the mns . optimal concentration of fluorophore / nu4 is ~1.02.5 mol fluorophore / mol antibody for fluorescent - nu4mns preparation . mice were anesthetized with isoflurane and then placed on their backs with their heads positioned to maximize the residency time for the delivered material to remain on the olfactory surface . each naris was administered with 568-nu4 , nu4mns or non - immune iggmns ( 5 l / naris ) , using a sterile micropipette , slowly over a period of 1 min , keeping the opposite naris and mouth closed to allow complete aspiration of delivered material . a falcon tube containing the mns treated tissue samples was placed in a bruker pharmascan 7 t animal mri scanner . sample were imaged using a t2 * -weighted gradient echo ( gre ) flash pulse sequence 3-dimensional acquisition . the image resolution was 0.07 mm isotropic , with field - of - view ( fov ) 4.62cm/2.52cm/0.65 cm and image matrix ( mtx ) 700 pixels/385 pixels/100 pixels . the number of averages ( nex ) was 20 to improve the signal - to - noise ratio . following intranasal inoculation , the probe was allowed to distribute for 4 hours before mr imaging was performed according to imaging methodology described in mundt et al . t1 , t2 , and t2 * weighted mr images were acquired on a bruker biospec 7 t magnet , using a 25 mm rf quadrature coil . t1- and t2-weighted images provide anatomical guidance as well as some localization of the nu4mns and were acquired with a fat suppressed spin echo sequence ( rapid acquisition with relaxation enhancement , rare ) with the following parameters for t1-weighted ( tr=1000 ms , teeff=13.2 ms , rare factor 2 , number of excitations , nex=4 ) and for t2-weighted ( tr=3500 ms , teeff=58.5 ms , rare factor 4 , nex=4 ) . t2 * -weighted imaging provides more of the localization of the nu4mns as the iron causes local changes in magnetic susceptibility which t2 * weighted images can be sensitive to . a gradient echo sequence was used with the following parameters ( gradient echo fast imaging , gefi ; tr=1200 ms , te=5.6 ms , flip angle 35 and nex=4 ) .
one way to image the molecular pathology in alzheimer s disease ( ad ) is by positron emission tomography using probes that target amyloid fibrils . 
 however , these fibrils are not closely linked to the development of the disease . 
 it is now thought that early stage biomarkers that instigate memory loss comprise of a oligomers ( aos ) . 
 here we report a sensitive molecular magnetic resonance imaging ( mri ) contrast probe that is specific for aos . 
 we attach oligomer - specific antibodies onto magnetic nanostructures and show the complex is stable and it binds to aos on cells and brain tissues to give a mri signal . 
 when intranasally administered to an ad mouse model , the probe readily reached hippocampal aos . in isolated samples of human brain tissue 
 , we observed an mri signal that distinguished ad from controls . 
 such nanostructures that target neurotoxic aos are potentially useful for evaluating the efficacy of new drugs and ultimately for early - stage ad diagnosis and disease management .