| Alzheimer's disease(AD) is the most common form of dementia and is characterised by progressive impairment in cognitive function and behaviour.The pathological features of AD include neuritic plaques composed ofβ-amyloid peptide (Aβ) fibrils,neurofibrillary tangles of hyperphosphorylated tau,and neurotransmitter deficits.People with mild cognitive impairment(MCI) have a high risk of AD.MCI is an intermediate stage between cognitive change with normal ageing and what might constitute an early stage of AD.The distinction between normal ageing and MCI might be quite subtle.Patients with MCI have amyloid pathology in higher amounts than expected for age at autopsy.In order to understand and detect early AD,not only functional consequences of the pathological processes but also in vivo neurochemistry and imaging of aetiological and pathological processes including Aβpathology need to be measured. The measurement of amyloid in vivo will not only have a large effect on the understanding of the underlying pathophysiological mechanisms of AD,but also should aid in the testing of new antiamyloid drugs.Ongoing studies with antiamyloid therapy,such as vaccination,have shown some difficulties in the assessment of drug effects at autopsy.The visualisation of amyloid plaques in the brains of living patients with AD would greatly aid the assessment of efficacy for antiamyloid therapy.Developing Aβ-aggregate-specific imaging agents is now an emerging field of research.Many agents based on Chrysamine G and Congo Red have been reported recently with only limited success.The 2-arylbenzothiazole(BTA) derivatives represent one of the most promising families,of which[11C]6-OH-BTA-1(carbon-11-labelled-PIB) shows more binding in the brains of patients with AD than in those of healthy people.Partâ… The chemical syntheses of 6-OH-BTA-0 and 6-OH-BTA-1Aim:To synthesize and identify 6-OH-BTA-0 and and 6-OH-BTA-1,which of the former is precursor of amyloid positron emission tomography(PET) imaging chemical[11C]6-OH-BTA-1,and the later is quality control.2.To find the appropriate HPLC mobile phase mixture for 6-OH-BTA-0 and and 6-OH-BTA-1.Methods:After series of chemical syntheses,throughâ‘ N-(4'-methoxyphenyl)-4-nitrothiobenzamideâ‘¡2-(4'-nitrophenyl)-6-methoxybenzothiazoleâ‘¢2-(4'-nitrophenyl)-6-hydroxybenzothiazole,â‘£2-(4'-nitrophenyl)-6-methoxymethoxybenzothiazole,there was the last intermediate product 2-(4'-aminophenyl)-6-methoxymethoxybenzothiazole (6-MOMO-BTA-0).Then 6-MOMO-BTA-0 was made to 2-(4'-aminophenyl)-6-hydroxybenzothiazole (6-OH-BYA-0)and 2-(4'-methylaminophenyl)-6-hydroxybenzothiazole (6-OH-BYA-1).We tried different HPLC mobile phase portions of CH3CN/H2O/triethyl-ammonium acetate and many flow rates.Result:1.6-OH-BTA-0 is light yellow powder,tested by 1H-NMR and 13C-NMR.2.6-OH-BTA-1 is vermilion powder,tested by 1H-NMR.3.An analytical HPLC column,stationary phase:Hypersil C-18 ODS2 5um, 4.6mm×250mm;mobile phase:V(CH3CN):V(H2O):V(triethylammonium acetate) =250:250:1 of pH 6,flow:2ml/min,UV detector 254nm.Partâ…¡Different efficient radiosyntheses ofβ-amyloid imaging radiotracer([11C]-6-OH-BTA-1)Aim:1.To compare the captive solvent "loop" method and "V-Vial" method used in radiosyntheses of[11C]6-OH-BTA-1.2.To check the radiolabelled effect of self-made 6-OH-BTA-0 and ABX Co. 6-OH-BTA-0.Method:1."V-Vial" method:[11C]-methyl triflate was bubbled(N2 sweep flow of 20 ml/min) into a solution of 6-OH-BTA-0 in methylethyl ketone at -20℃.Upon maximal trapping of radioactivity,the reaction was immediately heated to 80℃for one minute.2."loop" method:[11C]-methylations with[11C]-methyl triflate were carried out inside an HPLC sample loop at room temperature.Then the mixture was purified with C18 cartridge.Result:1.Two methods of[11C]6-OH-BTA-1 in sterile solution ready for i.v. injection within total synthesis times of 33min.Radiochemical yields of "V-Vial" method is 28±12%,while "loop" method is 40±4%.2.There are no significant difference in radiochemical yields of 40±4%between self-made 6-OH-BTA-0 and ABX Co.6-OH-BTA-0,which of the former is radiochemical purity of 92-93%,and the latter is of 93%.Partâ…¢Entry and clearance of[11C]6-OH-BTA-1 in rats,PET imaging in mice and rhesus monkey for clinical test preparationsAim:1.To make quality standard of[11C]6-OH-BTA-1 preparation.2.To investigate acute toxicity in mice.3.To clarify the entry,distribution and clearance of animals.Method:1.Three preparations of[11C]6-OH-BTA-1 were lasted for 3 radio-active half-lives to test pH,radiochemical purity and etc.2.Six mice were injected in a lateral tail vein with 74 MBq(2mCi) of [11C]6-OH-BTA-1,killed to obtain pathology slices in 7 days.3.The normal rats were injected in a lateral tail vein with 3.7 MBq(0.1mCi) of [11C]6-OH-BTA-1,then anesthetized and killed to obtain arterial blood,heart,hepar, spleen,lung,and kidney samples at 5,10,20,30,40,or 60min postinjection.Brains were rapidly excised and divided into cerebellum,brain stem,prefrontal lobe, temporal lobe,and occipital lobe fractions.All samples were counted in a gamma wellcounter,and the counts were decay-corrected to the time of injection relative to 11C standards prepared from the injection solution to determine the percent injected dose(%ID) in the samples.The samples were weighed to determine the percent injected dose per gram tissue(%ID/g),and this quantity was multiplied by the whole body weight(in kg) to determine the body-weight normalized radioactivity concentration%ID-Kg/g of each tissue sample.Result:1.[11C]6-OH-BTA-1 i.v.injection is hyaline,pH6.0～8.0,radioactive half-life of 21±0.5min,and radiochemicaI purity by radio HPLC＞90%.2.There are no toxic effects of 1000 times of clinical injection done on mice.3.At an early stage after injection,the radio activity in blood and lung is much higher than other tissues,but diminished through hepar quickly.At 20min postinjection,other than brain,the tissues carrying highest radio activity are hepar, lung,kidney,blood,spleen,and heart.APP transgenic mice and control senile mice have the same significant radio activity in hepar,partial accumulation in kidney. There are only heart(%ID=0.63±0.14) and spleen(0.17±0.11) of APP transgenic mice different from control mice(heart0.42±0.12,spleen0.07±0.02),p＜0.05.Conclusions1.Self-made 6-OH-BTA-0 and 6-OH-BTA-1 are qualified by NMR.2."loop" method to radiolabel[11C]6-OH-BTA-1 is recommended.3.There are no toxic effects of 1000 times of clinical injection done on mice.4.It's 20 min postinjection to get PET/CT scan.5.APP transgenic mice and control mice almost have the same radio activity in brains.We've made enough preparations for PET clinical test of[11C]6-OH-BTA-1.
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