This work supported by research grant funding from the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Ontario Institute for Cancer Research (OICR, #P.SI.015.8), and the Canadian Cancer Society (CCS, #703857). The authors acknowledge the contributions of Dr. Denis Snider who provided assistance in preparing the manuscript.

מחקרים בבעלי חיים אושרו על ידי מועצת האתיקה בעלי חיים למחקר באוניברסיטת מקמאסטר בהתאם המועצה הקנדית על טיפול בבעלי חיים (CCAC) הנחיות. 1. Radiolabeling של הליגנדים TZ-tridentate עם 99m Tc זהירות: ההליכים הבאים מחייבים את השימוש של תרכובות רדיואקטיבי. העבודה צריכה להיעשות רק במעבדה מורשה עם דבקות תקנות הבטיחות וסילוק. תגובות מיקרוגל צריכות להתבצע במיקרוגל שתוכנן במיוחד עבור סינתזה כימית. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> סינתזה של [99m Tc (CO) 3 (H 2 O) 3] + 19, 20 <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> בבקבוקון מיקרוגל, לשלב 8 מ&quot;ג K 2 [BH 3 CO 2], 15 מ&quot;ג Na 2 CO 3, 20 מ&quot;ג Na 2 B 4 O 7 · 10H 2 O, ו -25 מ&quot;ג קוקו [CH (OH)]2 COONa · 4H 2 O. טהר הבקבוקון במשך 10 דקות עם גז ארגון. </li><li style=";text-align:right;direction:rtl"> הוסף 4 מ&quot;ל של 99m TCO 4 - (~ 1,100 MBq, ~ 30 MCI) סליין 0.9% ל הבקבוקון. </li><li style=";text-align:right;direction:rtl"> מחמם את התגובה במיקרוגל במשך 3.5 דקות ב 110 מעלות צלזיוס לאחר 10 שניות של ערבוב כדי להבטיח ערבוב יסודי של חומרים כימיים. </li><li style=";text-align:right;direction:rtl"> התאם את ה- pH של הפתרון 3.5-4 באמצעות ~ 400 μL של 1 M HCl. אמת באמצעות נייר pH. </li></ol></li><li style=";text-align:right;direction:rtl"> Radiolabeling של Tetrazine הליגנדים 1-5 <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> ממיסים 2 מ&quot;ג של כל ליגנד (תרכובות 1-5) ב 250 μL MeOH 21. </li><li style=";text-align:right;direction:rtl"> הוסף 250 μL של [99m Tc (CO) 3 (H 2 O) 3] + (~ 74 MBq, ~ 2 MCI) כל פתרון. </li><li style=";text-align:right;direction:rtl"> מחממים את תערובת התגובה באמצעות במיקרוגל למשך 20 דקות ב 60 מעלות צלזיוס. הערה: שלב זה היה זהה עבור כל 5 tetrazines. </li><li style=";text-align:right;direction:rtl"> עבור תרכובות 2- 5, להתאדות הממס מחדש dissolve המוצרים וכתוצאה מכך 1 מ&quot;ל של 1: 1 v / v DCM: TFA. </li><li style=";text-align:right;direction:rtl"> מחממים את תוצרי התגובה מומס (2-5) ב 60 ° C במיקרוגל במשך 6 דקות (2-4) או 10 דקות (5). </li><li style=";text-align:right;direction:rtl"> לאחר קירור לטמפרטורת החדר, להתאדות ממס באמצעות המאייד (36 מעלות צלזיוס, 8 mbar, 3 דקות, 6,000 סל&quot;ד) ו לפזר את המתחם מיובש 1: 1 ACN: H 2 O או 1: 1 MeOH: H 2 O, לפני טיהור HPLC. </li><li style=";text-align:right;direction:rtl"> לטהר את תרכובות Tc שכותרתו 99m (1-5), כולל הפרדת מוצר שכותרתו מ ליגנד tetrazine ללא תווית, באמצעות HPLC (C 18 התהפכה פאזי). בדרך כלל, להשתמש שיפוע elution של 30:70 ACN: H 2 O (שניהם עם 0.1% TFA) כדי 40:60 ACN: H 2 O מעל 20 דקות (18 דקות) ו טור 100 מ&quot;מ 4.6 x 18 C אנליטית. השתמש בשני UV (254 ננומטר) וזיהוי גמא. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> לקחת דגימה קטנה של כל מוצר שהכותרת ולהשוות זמן שמירת HPLC שלה לזה של inj-שיתוףected, שאינם רדיואקטיביים, Re-שכותרתו סטנדרטי (0.125 מ&quot;ג ב 20% מתנול-H 2 O). התקן שכותרתו Re מזוהה עקבות UV HPLC, ויהיה elute באותו זמן כמו במתחם Tc שכותרתו 99m ב עקבות γ-HPLC. שיתוף הזרקה זה מראה פסגות בזמני שימור דומים, המאשרת את זהותו של 99m Tc שכותרתו מתחם. </li></ol></li><li style=";text-align:right;direction:rtl"> להתאדות הממס מתוך שברי HPLC באמצעות מאייד (36 מעלות צלזיוס, 8 mbar, 3 דקות, 6,000 סל&quot;ד). </li><li style=";text-align:right;direction:rtl"> נסח במתחם המטוהר בריכוז של 7.4 kBq / μL ב PBS, המכיל BSA 0.5% ו 0.01% Tween-80. </li><li style=";text-align:right;direction:rtl"> כדי להבטיח את התרכובות שכותרתו יציבות, לבצע מחקר יציבות חוץ גופייה. דגירה למתחם ניסח ב 37 מעלות צלזיוס למשך 1, 4 ו -6 שעות, הזרקת כמות קטנה (3.7 MBq) של התערובת על HPLC בכל נקודת זמן כדי להעריך את היציבות. </li></ol></li></ol> 2. מחקרים ביו-הפצה טרום ממוקד <ol style=";text-align:right;direction:rtl"><li&gt; הכנת חיות <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> שימוש 7-9 בן שבוע, עכברים Balb / c נקבה (n = 3), לנהל TCO-BP מנוסחת מלוחים (20 מ&quot;ג / ק&quot;ג) (5 מיקרוגרם / μL), באמצעות הזרקת הזנב ורידים. </li><li style=";text-align:right;direction:rtl"> העבר את העכבר בהתקן ריסון פיזי, ולזהות את הוורידים ממוקמים על המשטחים לרוחב של הזנב ולנגב עם מטלית אלכוהול. בערך בשעה 2 ס&quot;מ מהקצה של הזנב, להכניס מחט 30-מד בזווית שטוחה, במקביל הווריד. לאט לוחץ על המתג כדי להזריק, להסיר מחט ולהחיל ספוג גזה נקי במקום ההזרקה עם לחץ קל עד עוצר דימום. </li><li style=";text-align:right;direction:rtl"> בשעה 1 הזרקת שעות שלאחר של TCO-BP, לנהל ~ 0.74 MBq (20 μCi) של 99m Tc-tetrazine מנוסחת 100 μL של 0.5% BSA, 0.01% Tween-80 ב PBS, באמצעות הזרקה-וריד הזנב. </li></ol></li><li style=";text-align:right;direction:rtl"> מחקרים ביו-הפצה <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> בנקודת הזמן הרצויה (t = 6 שעות), לטשטש את העכברים באמצעות 3% isoflurane תערובת גז חמצן 2%. להפגין כדידואר נסיגת קמצוץ על העכבר הרדים כדי לוודא שהם תחת מטוס של הרדמה כירורגית. </li><li style=";text-align:right;direction:rtl"> איסוף דם (1 מ&quot;ל) באמצעות לנקב לב באמצעות מזרק טרום שטופלו הפרין. מקום עכבר על גבית עם אף בחרוט אף הרדמה המשיכה ולאתר את תהליך xiphoid על החיה. <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הכנס מחט 25 G, מעט שמאלה של קו האמצע של החיה תחת תהליך xiphoid, בזווית 20 מעלות. הכנס את המחט, ולאט לאט למשוך בחזרה על הבוכנה לראות דם רכזת המחט אם הלב היה מנוקב. מעט מחדש את המחט תוך כדי לחיצה על הבוכנה במידת הצורך, כדי לנקב את הלב. לאט להקיז דם לתוך המזרק. </li></ol></li><li style=";text-align:right;direction:rtl"> להרדימו על ידי נקע בצוואר הרחם, בעוד בהרדמה. </li><li style=";text-align:right;direction:rtl"> מניח כל חיה בתוך שקית פלסטיק ולהשתמש כיל מנה (הגדרת Tc 99m) כדי למדוד את רמת פעילות הגוף כולו. </li><li style=";text-align:right;direction:rtl"> אסוף את רקמות ונוזלים הבאים טרום לשקולed לספור צינורות: דם, עצמות (ברך וכתף), כיס מרה, כליות, כבד, קיבה (עם תוכן), מעי דק (עם תוכן), מעי גס ואת מעי אטום (עם תוכן), בלוטת תריס ואת קנה נשימה, שלפוחית ​​שתן עם שתן , וזנב. </li><li style=";text-align:right;direction:rtl"> לשטוף רקמות מתאימות (למעט דם, כיס מרה, ואת שלפוחית ​​שתן) ב PBS להסיר דם כתם יבש לפני הנחת רקמות צינורות ספירה מתאימות. </li><li style=";text-align:right;direction:rtl"> מניחים פגר חיה בתוך שקית ניילון ולמדוד פעילות הגוף כולו שיורית באמצעות כיל מנה. </li><li style=";text-align:right;direction:rtl"> לשקול כל שפופרת המכילה דגימת רקמה. המשקל ההתחלתי הפחת של הצינור כדי לקבל מסה של רקמה. </li><li style=";text-align:right;direction:rtl"> השתמש כיל מנה (הגדרת Tc 99m) כדי למדוד את כמות פעילות מדגם בדיקה (100 μL) בעת ההזרקה עבור כל עכבר. הערה: זה מדגם בדיקה שווה את עוצמת הזריקה, ובכך נותן את ספירת הפעילות בזמן ההזרקה. </li><li style=";text-align:right;direction:rtl"> בעת מדידת רקמות,liquot 5 μL של מדגם הבדיקה השתמש בעבר. השתמש דלפק גמא רב-גלאי (הגדרת Tc 99m) ולספור להשיג הספירה לדקה (CPM) עבור מדגם בדיקת 5 μL. </li><li style=";text-align:right;direction:rtl"> השתמש בשני הערכים שהתקבלו ב 2.2.9 ו 2.2.10 לחשב את הפעילות ואת קשר CPM בעזרת משוואת 1 להשיג מקדם מרה (CPM μCi -1). (1) <img alt="משוואה 1" src="/files/ftp_upload/55188/55188eq1.jpg" /></li><li style=";text-align:right;direction:rtl"> השתמש הדלפק גמא למדוד את כמות רדיואקטיביות בכל רקמה או מדגם נוזל. </li><li style=";text-align:right;direction:rtl"> השתמש במשוואה 1 כדי לחשב את הסכום של הפעילות בכל רקמה או נוזל בזמן יחסית המדידה מהחומר המוזרק הכולל. ערך זה מנורמל אז לפי משקל איבר כפי שדווח מהחומר המוזרק אחוזים לגרם (כלומר,% מזהה / g) של רקמות. </li><li style=";text-align:right;direction:rtl"> בצע את השלבים 2.1.2 כדי 2.2.13 לנהל ניסוי ביקורת שלילית באמצעות הליגנדים tetrazine Tc שכותרתו 99m ב absence של TCO-BP. עכברי קורבן (n = 3) ברמה של 0.5, 1, 4 ו -6 הזרקת שעות שלאחר ולקבל רקמה או נוזל כמתואר לעיל. </li></ol></li></ol>

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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+properties+of+boranocarbonate:+A+convenient+in+situ+CO+source+for+the+aqueous+preparation+of+[99mTc(OH2)3(CO)3.">Synthesis and properties of boranocarbonate: A convenient in situ CO source for the aqueous preparation of [99mTc(OH2)3(CO)3.</a> J. Am. Chem. Soc. 123 (13), 3135-3136 (2001).</li><li>Lu, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+SAR+of+99mTc/Re-labeled+Small+Molecule+Prostate+Specific+Membrane+Antigen+Inhibitors+with+Novel+Polar+Chelates.">Synthesis and SAR of 99mTc/Re-labeled Small Molecule Prostate Specific Membrane Antigen Inhibitors with Novel Polar Chelates.</a> Bioorg. Med. Chem. Lett. 23 (5), 1557-1563 (2013).</li><li>Maresca, K. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+Molecule+Inhibitors+of+PSMA+Incorporating+Technetium-99m+for+Imaging+Prostate+Cancer:+Effects+of+Chelate+Design+on+Pharmacokinetics.">Small Molecule Inhibitors of PSMA Incorporating Technetium-99m for Imaging Prostate Cancer: Effects of Chelate Design on Pharmacokinetics.</a> Inorg. Chim. Acta. 389, 168-175 (2012).</li><li>Bartholom&#228;, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insight+into+the+Mode+of+Action+of+Re(CO)3+Thymidine+Complexes.">Insight into the Mode of Action of Re(CO)3 Thymidine Complexes.</a> ChemMedChem. 5 (9), 1513-1529 (2010).</li></ol>

The authors declare they have no competing financial interests.

אוסף של chelates tridentate צמוד tetrazine של קטבים שונים הוכן, ואת השירות של המתחמים שלהם 99m Tc תגובת IEDDA עם נגזרת TCO in vivo הוערך. שיטת תיוג יעילה לשחזור 99m Tc פותחה במשך חמש tetrazine-chelates, שבו הריכוז ליגנד היה 10 -3 M. שלב התיוג לווה deprotection של T- קבוצות בוטיל (עבור תרכ...

99m Tc נשאר רדיואיזוטופיים הדומיננטי בשימוש ברפואה גרעינית אבחון, עם למעלה מ -50 מיליון הליכי הדמיה שנערכו בשנת ברחבי עולם 1, 2, 3. רוב סוכני 99m Tc בשימוש קליני הם רדיואקטיביות סוג זלוף. ישנם מספר מצומצם של תרכובות ממוקדות פעיל אשר 99m Tc מופנה לאגד סמן ביולוגי ספציפי באמצעות קשירה לבנות מיקוד. יצירת רדיואקטיביות 99m Tc הממוקד מתעכבת לעתים קרובות על ידי השפעתו של 99m Tc-ליגנד מתחמים על היכולת של מולקולת המיקוד להיקשר הסמן הביולוגי של עניין, או איזוטופים מחצית החיים אינם ארוך מספיק לשימוש עם ביומולקולות משקל מולקולרי גבוה כמו נוגדנים. זה האחרון בדרך כלל דורש כמה ימים לפני תמונות נרכשות על מנת biomolecule כדי לנקות מן היעד הלא Tiss<html> UES. מיקוד טרום מציע גישה חלופית כדי להתגבר על האתגרים אלה. טרום מיקוד בשילוב עם כימית bioorthogonal הוכח להיות דרך יעילה לפתח בדיקות הדמיה מולקולריות חדשות לשני קרינת רדיו-הדמיה 4, 5, 6, 7, 8. הביקוש אלקטרונים הפוך- אלמון דילס (IEDDA) התגובה בין 1,2,4,5-tetrazine (טז) ו -cyclooctene טרנס (TCO) נגזרים, כפי שמוצג באיור 1, הוכח להיות יעיל במיוחד 6. התגובה IEDDA עם רכיבים אלה יכולים להפגין קינטיקה מהירה ב PBS (k 2 ≈ 6,000 M -1 s -1) סלקטיביות גבוהה, מה שהופך אותו אידיאלי עבור in vivo מראש מיקוד יישומים 9, 10. <html> e_content &quot;&gt; הגישה הנפוצה ביותר בשימוש כרוך בניהול וקטור מיקוד TCO הנגזר לאחר תקופת עיכוב מספיק, tetrazine radiolabeled מנוהל. tetrazines radiolabeled מבוסס על 11 C, 18 F, 64 Cu, 89 ZR, ו -111 ב כבר 11 דיווחו, 12, 13, 14, 15. לעומת זאת, יש רק אחד הדיווחים של 99m Tc שכותרתו טז, אשר הוכן באמצעות ליגנד סוג HYNIC המחייב שימוש-הליגנדים שיתוף למנוע התקשרות חלבונים והשפלה in vivo 16. כחלופה, אנו מדווחים כאן את הסינתזה של 99m Tc (I) שכותרתו tetrazines באמצעות משפחה של הליגנדים המהווים מתחמי tridentate יציבה עם [99m Tc (CO) 3] + הליבה. גיל = &quot;1&quot;&gt; <img alt="איור 1" src="/files/ftp_upload/55188/55188fig1.jpg" /> איור 1: תגובת IEDDA bioorthogonal בין tetrazine ו -cyclooctene טרנס. <a href="http://ecsource.jove.com/files/ftp_upload/55188/55188fig1large.jpg" target="_blank">אנא לחץ כאן כדי לצפות בגרסה גדולה יותר של דמות זו.</a> בני משפחתו של הליגנדים מוכן לכלול chelates tridentate שמשתנות הקוטביות ואת לאופי הקבוצה מקשר בין אזור מתכת מחייב ואת טז (איור 2). המטרה היתה לזהות 99m Tc-Tetrazine לבנות שיכול למקם ביעילות ומגיבים עם אתרים שכותרתו TCO in vivo וברור במהירות כאשר לא מחויב, על מנת להניב גבוהה היעד ל-יעד שאינו יחסי. כדי לבדוק את הליגנדים, TCO-נגזרת של ביספוספונטים (TCO-BP) שימש 17. הראינו בעבר כי TCO-BP localizes לאזורים של מטבוליזם העצם פעיל ויכול להגיב עםtetrazines radiolabeled in vivo 18. זהו מגיב נוח לבדוק tetrazines חדש, כי זה יכול להיות מוכן בשלב אחד וניסויים יכול להתבצע בעכברים נורמליים שבו לוקליזציה מתרחשת בעיקר במפרקים (ברכיים וכתפיים).

<table><tbody><tr><td>Argon gas</td><td>Alphagaz</td><td>---</td><td>---</td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3&lt;/sub&gt;</td><td>EMD Millipore</td><td>106395</td><td>---</td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;B&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;&amp;#183;10H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Anachemia</td><td>S9640</td><td>---</td></tr><tr><td>KNaC&lt;sub&gt;4&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt;&amp;#183;4H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Anachemia</td><td>217255</td><td>---</td></tr><tr><td>Technelite &lt;sup&gt;99m&lt;/sup&gt;Tc generator</td><td>Lantheus medical imaging</td><td>---</td><td>Source of &lt;sup&gt;99m&lt;/sup&gt;TcO&lt;sup&gt;4-&lt;/sup&gt;</td></tr><tr><td>0.9% Saline</td><td>Lantheus medical imaging</td><td>---</td><td>To elute generator</td></tr><tr><td>1 M HCl</td><td>Lab Chem</td><td>---</td><td>---</td></tr><tr><td>MeOH</td><td>Caledon</td><td>---</td><td>---</td></tr><tr><td>ACN</td><td>Caledon</td><td>---</td><td>HPLC grade</td></tr><tr><td>Millipore H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Thermo Fisher Scientific</td><td>Barnstead Nanopure</td><td>---</td></tr><tr><td>DCM</td><td>Caledon</td><td>---</td><td>---</td></tr><tr><td>TFA</td><td>Caledon</td><td>---</td><td>---</td></tr><tr><td>PBS</td><td>Thermo Fisher Scientific</td><td>10010023</td><td>pH 7.4 1x</td></tr><tr><td>BSA</td><td>Sigma Aldrich</td><td>A7906</td><td>---</td></tr><tr><td>Tween80</td><td>Sigma Aldrich</td><td>P8047</td><td>---</td></tr><tr><td>Isoflurane</td><td>CDMV</td><td>108737</td><td>Supplier: Fresenius Kabi Animal Health</td></tr><tr><td>HPLC</td><td>Waters</td><td>1525 Binary Pump, 2998 Photodiodde Array Detector, E-SAT/IN, Bioscan Flowcount PMT detector (item # 15590)</td><td>---</td></tr><tr><td>HPLC column for analysis and purification of compounds 2-4</td><td>Phenomenex</td><td>00G-4435-E0</td><td>Gemini&amp;reg; 5 &amp;micro;m C18 110&amp;nbsp;&amp;Aring;, LC Column 250 x 4.6 mm</td></tr><tr><td>HPLC column for analysis and purification of compounds 1 and 5</td><td>Waters&amp;nbsp;</td><td>186003115</td><td>XBridge BEH C18 Column, 130 &amp;Aring;, 5 &amp;micro;m, 4.6 mm x 100 mm</td></tr><tr><td>Microwave Reactor&amp;nbsp;</td><td>Biotage&amp;nbsp;</td><td>Initiator 8</td><td>---</td></tr><tr><td>Biotage V10 Evaporator</td><td>Biotage&amp;nbsp;</td><td>Serial # V1041</td><td>---</td></tr><tr><td>Dose calibrator</td><td>Capintec, Inc.&amp;nbsp;</td><td>CRC-25R</td><td>---</td></tr><tr><td>Gamma counter</td><td>Perkin Elmer</td><td>Wizard 1470 Automatic Gamma Counter</td><td>---</td></tr><tr><td>Animal room scale&amp;nbsp;</td><td>Mettler Toledo</td><td>XP105 Delta Range</td><td>---</td></tr><tr><td>Microwave vials&amp;nbsp;</td><td>Biotage&amp;nbsp;</td><td>355629</td><td>0.5-2 mL&amp;nbsp;</td></tr></tbody></table>

preparation and evaluation of 99mtc-labeled tridentate chelates for pre-targeting using bioorthogonal chemistry

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the inverse electron demand Diels-Alder (IEDDA) cycloaddition between a radiolabeled tetrazines and trans-cyclooctene (TCO) linked to a biomolecule has proven to be a highly effective bioorthogonal approach to imaging specific biological targets. Despite the fact that technetium-99m remains the most widely used isotope in diagnostic nuclear medicine, there is a scarcity of methods for preparing 99mTc-labeled tetrazines. Herein we report the preparation of a family of tridentate-chelate-tetrazine derivatives and their Tc(I) complexes. These hitherto unknown compounds were radiolabeled with 99mTc using a microwave-assisted method in 31% to 83% radiochemical yield. The products are stable in saline and PBS and react rapidly with TCO derivatives in vitro. Their in vivo pre-targeting abilities were demonstrated using a TCO-bisphosphonate (TCO-BP) derivative that localizes to regions of active bone metabolism or injury. In murine studies, the 99mTc-tetrazines showed high activity concentrations in knees and shoulder joints, which was not observed when experiments were performed in the absence of TCO-BP. The overall uptake in non-target organs and pharmacokinetics varied greatly depending on the nature of the linker and polarity of the chelate.

הליגנדים היו מסונתזים באמצעות linkers ו chelators השונים באמצעות אסטרטגית amination רדוקטיבי פשוטה (איור 2), ואחריו צימוד של המוצר אל tetrazine הזמין מסחרי 22, 23. Radiolabeling בוצע תוך שימוש באותה השיטה לכל התרכובות והיה מאוד לשחזור...

Watch this Scientific Journal Video about Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry at JoVE.com

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Here, we describe a protocol for radiolabeling and in vivo testing of tridentate 99mTc(I) chelate-tetrazine derivatives for pre-targeting and bioorthogonal chemistry.

הכנה והערכה של<sup&gt; 99m</sup&gt; Tc שכותרתו Tridentate chelates לחינוך קדם-מיקוד שימוש Bioorthogonal לכימיה

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the ...

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Research

JoVE Journal

Chemistry

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

8.1K Views.  McMaster University. Here, we describe a protocol for radiolabeling and in vivo testing of tridentate 99mTc(I) chelate-tetrazine derivatives for pre-targeting and bioorthogonal chemistry. 

Video: Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Microfluidic On-chip Capture-cycloaddition Reaction to Reversibly Immobilize Small Molecules or Multi-component Structures for Biosensor Applications

Methods for rapid surface immobilization of bioactive small molecules with control over orientation and immobilization density are highly desirable for biosensor and microarray applications. In this Study, we use a highly efficient covalent bioorthogonal [4+2] cycloaddition reaction between trans-cyclooctene (TCO) and 1,2,4,5-tetrazine (Tz) to enable the microfluidic immobilization of TCO/Tz-derivatized molecules. We monitor the process in real-time under continuous flow conditions using surface plasmon resonance (SPR). To enable reversible immobilization and extend the experimental range of the sensor surface, we combine a non-covalent antigen-antibody capture component with the cycloaddition reaction. By alternately presenting TCO or Tz moieties to the sensor surface, multiple capture-cycloaddition processes are now possible on one sensor surface for on-chip assembly and interaction studies of a variety of multi-component structures. We illustrate this method with two different immobilization experiments on a biosensor chip; a small molecule, AP1497 that binds FK506-binding protein 12 (FKBP12); and the same small molecule as part of an immobilized and in situ-functionalized nanoparticle.

We present a method for rapid, reversible immobilization of small molecules and functionalized nanoparticle assemblies for Surface Plasmon Resonance (SPR) studies, using sequential on-chip bioorthogonal cycloaddition chemistry and antibody-antigen capture.

Microfluidic תגובת Capture-חיי בן אשר על השבב כדי לשתק הפיך מולקולות קטנות או מבני Multi-רכיב עבור יישומי Biosensor

Methods  for rapid surface immobilization of bioactive small molecules with control over  orientation and immobilization density are highly desirable for ...

The Bioconjugation and Radiosynthesis of 89Zr-DFO-labeled Antibodies

The exceptional affinity, specificity, and selectivity of antibodies make them extraordinarily attractive vectors for tumor-targeted PET radiopharmaceuticals. Due to their multi-day biological half-life, antibodies must be labeled with positron-emitting radionuclides with relatively long physical decay half-lives. Traditionally, the positron-emitting isotopes 124I (t1/2 = 4.18 d), 86Y (t1/2 = 14.7 hr), and 64Cu (t1/2 = 12.7 hr) have been used to label antibodies for PET imaging. More recently, however, the field has witnessed a dramatic increase in the use of the positron-emitting radiometal 89Zr in antibody-based PET imaging agents. 89Zr is a nearly ideal radioisotope for PET imaging with immunoconjugates, as it possesses a physical half-life (t1/2 = 78.4 hr) that is compatible with the in vivo pharmacokinetics of antibodies and emits a relatively low energy positron that produces high resolution images. Furthermore, antibodies can be straightforwardly labeled with 89Zr using the siderophore-derived chelator desferrioxamine (DFO). In this protocol, the prostate-specific membrane antigen targeting antibody J591 will be used as a model system to illustrate (1) the bioconjugation of the bifunctional chelator DFO-isothiocyanate to an antibody, (2) the radiosynthesis and purification of a 89Zr-DFO-mAb radioimmunoconjugate, and (3) in vivo PET imaging with an 89Zr-DFO-mAb radioimmunoconjugate in a murine model of cancer.

The Bioconjugation and Radiosynthesis of 89Zr-DFO-labeled Antibodies

Due to its multi-day radioactive half-life and favorable decay properties, the positron-emitting radiometal 89Zr is extremely well-suited for use in antibody-based radiopharmaceuticals for PET imaging. In this protocol, the bioconjugation, radiosynthesis, and preclinical application of 89Zr-labeled antibodies will be described.

Bioconjugation וRadiosynthesis של<sup&gt; 89</sup&gt; נוגדנים שכותרתו ZR-DFO

The exceptional affinity, specificity, and selectivity of antibodies make them extraordinarily attractive vectors for tumor-targeted PET ...

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient radiolabeling of DBCO-group-functionalized gold nanoparticles using a copper-free click reaction. Radioiodination of the stannylated precursor (2) was carried out by using [125I]NaI and chloramine T as an oxidant at room temperature for 15 min. After HPLC purification of the crude product, the purified 125I-labeled azide (1) was obtained with high radiochemical yield (75 &plusmn; 10%, n = 8) and excellent radiochemical purity (&gt;99%). For the synthesis of radiolabeled 13-nm-sized gold nanoparticles, the DBCO-functionalized gold nanoparticles (3) were prepared by using a thiolated polyethylene glycol polymer. A copper-free click reaction between 1 and 3 gave the 125I-labeled gold nanoparticles (4) with more than 95% of radiochemical yield as determined by radio-thin-layer chromatography (radio-TLC). These results clearly indicate that the present radiolabeling method using a strain-promoted copper-free click reaction will be useful for the efficient and convenient radiolabeling of DBCO-group-containing nanomaterials.

An Optimized Protocol for the Efficient Radiolabeling of Gold Nanoparticles by Using a 125I-labeled Azide Prosthetic Group

A detailed procedure for the synthesis of a 125I-labeled azide and the radiolabeling of dibenzocyclooctyne (DBCO)-group-conjugated, 13-nm-sized gold nanoparticles using a copper-free click reaction is described.

פרוטוקול אופטימיזציה עבור Radiolabeling היעיל של חלקיקי זהב על ידי שימוש<sup&gt; 125</sup&gt; שכותרתו לי אזיד תותבת קבוצה

Here, we demonstrate a detailed protocol for the radiosynthesis of a 125I-labeled azide prosthetic group and its application to the efficient ...

Harnessing the Bioorthogonal Inverse Electron Demand Diels-Alder Cycloaddition for Pretargeted PET Imaging

Due to their exquisite affinity and specificity, antibodies have become extremely promising vectors for the delivery of radioisotopes to cancer cells for PET imaging. However, the necessity of labeling antibodies with radionuclides with long physical half-lives often results in high background radiation dose rates to non-target tissues. In order to circumvent this issue, we have employed a pretargeted PET imaging strategy based on the inverse electron demand Diels-Alder cycloaddition reaction. The methodology decouples the antibody from the radioactivity and thus exploits the positive characteristics of antibodies, while eschewing their pharmacokinetic drawbacks. The system is composed of four steps: (1) the injection of a mAb-trans-cyclooctene (TCO) conjugate; (2) a localization time period during which the antibody accumulates in the tumor and clears from the blood; (3) the injection of the radiolabeled tetrazine; and (4) the in vivo click ligation of the components followed by the clearance of excess radioligand. In the example presented in the work at hand, a 64Cu-NOTA-labeled tetrazine radioligand and a trans-cyclooctene-conjugated humanized antibody (huA33) were successfully used to delineate SW1222 colorectal cancer tumors with high tumor-to-background contrast. Further, the pretargeting methodology produces high quality images at only a fraction of the radiation dose to non-target tissue created by radioimmunoconjugates directly labeled with 64Cu or 89Zr. Ultimately, the modularity of this protocol is one of its greatest assets, as the trans-cyclooctene moiety can be appended to any non-internalizing antibody, and the tetrazine can be attached to a wide variety of radioisotopes.

The bioorthogonal inverse electron demand Diels-Alder cycloaddition has been harnessed to create an effective and modular pretargeted PET imaging strategy for cancer. In this protocol, the steps of this methodology are described in the context of a model system employing the colorectal cancer targeted antibody huA33 and a 64Cu-labeled radioligand.

רתימת ביקוש Bioorthogonal הפוך אלקטרונים דילס-Alder cycloaddition לPretargeted PET הדמיה

Due to their exquisite affinity and specificity, antibodies have become extremely promising vectors for the delivery of radioisotopes to cancer cells for ...

Bioengineering

MR Molecular Imaging of Prostate Cancer with a Small Molecular CLT1 Peptide Targeted Contrast Agent

Tumor extracellular matrix has abundance of cancer related proteins that can be used as biomarkers for cancer molecular imaging. In this work, we demonstrated effective MR cancer molecular imaging with a small molecular peptide targeted Gd-DOTA monoamide complex as a targeted MRI contrast agent specific to clotted plasma proteins in tumor stroma. We performed the experiment of evaluating the effectiveness of the agent for non-invasive detection of prostate tumor with MRI in a mouse orthotopic PC-3 prostate cancer model. The targeted contrast agent was effective to produce significant tumor contrast enhancement at a low dose of 0.03 mmol Gd/kg. The peptide targeted MRI contrast agent is promising for MR molecular imaging of prostate tumor.

To demonstrate MR cancer molecular imaging with a small peptide targeted MRI contrast agent specific to clotted plasma proteins in tumor stroma in a mouse prostate cancer model.

MR הדמיה המולקולרית של סרטן הערמונית עם חומר ניגוד ממוקד המולקולרי קטן CLT1 פפטיד

Tumor extracellular  matrix has abundance of cancer related proteins that can be used as biomarkers  for cancer molecular imaging. In this work,  we ...

Medicine

Pretargeted Radioimmunotherapy Based on the Inverse Electron Demand Diels-Alder Reaction

While radioimmunotherapy (RIT) is a promising approach for the treatment of cancer, the long pharmacokinetic half-life of radiolabeled antibodies can result in high radiation doses to healthy tissues. Perhaps not surprisingly, several different strategies have been developed to circumvent this troubling limitation. One of the most promising of these approaches is pretargeted radioimmunotherapy (PRIT). PRIT is predicated on decoupling the radionuclide from the immunoglobulin, injecting them separately, and then allowing them to combine in vivo at the target tissue. This approach harnesses the exceptional tumor-targeting properties of antibodies while skirting their pharmacokinetic drawbacks, thereby lowering radiation doses to non-target tissues and facilitating the use of radionuclides with half-lives that are considered too short for use in traditional radioimmunoconjugates. Over the last five years, our laboratory and others have developed an approach to in vivo pretargeting based on the inverse electron-demand Diels-Alder (IEDDA) reaction between trans-cyclooctene (TCO) and tetrazine (Tz). This strategy has been successfully applied to pretargeted positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging with a variety of antibody-antigen systems. In a pair of recent publications, we have demonstrated the efficacy of IEDDA-based PRIT in murine models of pancreatic ductal adenocarcinoma and colorectal carcinoma. In this protocol, we describe protocols for PRIT using a 177Lu-DOTA-labeled tetrazine radioligand ([177Lu]Lu-DOTA-PEG7-Tz) and a TCO-modified variant of the colorectal cancer targeting huA33 antibody (huA33-TCO). More specifically, we will describe the construction of huA33-TCO, the synthesis and radiolabeling of [177Lu]Lu-DOTA-PEG7-Tz, and the performance of in vivo biodistribution and longitudinal therapy studies in murine models of colorectal carcinoma.

This protocol describes the synthesis and characterization of a trans-cyclooctene (TCO)-modified antibody and a 177Lu-labeled tetrazine (Tz) radioligand for pretargeted radioimmunotherapy (PRIT). In addition, it details the use of these two constructs for in vivo biodistribution and longitudinal therapy studies in a murine model of colorectal cancer.

Radioimmunotherapy pretargeted התגובה תגובת דילס-אלדר דרישה אלקטרון הופכי

While radioimmunotherapy (RIT) is a promising approach for the treatment of cancer, the long pharmacokinetic half-life of radiolabeled antibodies can ...

Synthesis and Bioconjugation of Thiol-Reactive Reagents for the Creation of Site-Selectively Modified Immunoconjugates

Maleimide-bearing bifunctional probes have been employed for decades for the site-selective modification of thiols in biomolecules, especially antibodies. Yet maleimide-based conjugates display limited stability in vivo because the succinimidyl thioether linkage can undergo a retro-Michael reaction. This, of course, can lead to the release of the radioactive payload or its exchange with thiol-bearing biomolecules in circulation. Both of these processes can produce elevated activity concentrations in healthy organs as well as decreased activity concentrations in target tissues, resulting in reduced imaging contrast and lower therapeutic ratios. In 2018, we reported the creation of a modular, stable, and easily accessible phenyloxadiazolyl methyl sulfone reagent &#8212; dubbed &#8216;PODS&#8217; &#8212; as a platform for thiol-based bioconjugations. We have clearly demonstrated that PODS-based site-selective bioconjugations reproducibly and robustly create homogenous, well-defined, highly immunoreactive, and highly stable radioimmunoconjugates. Furthermore, preclinical experiments in murine models of colorectal cancer have shown that these site-selectively labeled radioimmunoconjugates exhibit far superior in vivo performance compared to radiolabeled antibodies synthesized via maleimide-based conjugations. In this protocol, we will describe the four-step synthesis of PODS, the creation of a bifunctional PODS-bearing variant of the ubiquitous chelator DOTA (PODS-DOTA), and the conjugation of PODS-DOTA to the HER2-targeting antibody trastuzumab.

In this protocol, we will describe the synthesis of PODS, a phenyoxadiazolyl methyl sulfone-based reagent for the site-selective attachment of cargos to the thiols of biomolecules, particularly antibodies. In addition, we will describe the synthesis and characterization of a PODS-bearing bifunctional chelator and its conjugation to a model antibody.

סינתזה, Bioconjugation של תיול-תגובתי ריאגנטים עבור הקמת האתר באופן סלקטיבי שונה Immunoconjugates

Maleimide-bearing bifunctional probes have been employed for decades for the site-selective modification of thiols in biomolecules, especially antibodies. ...

Positron Emission Tomography Imaging of Cell Trafficking: A Method of Cell Radiolabeling

Stem cell and chimeric antigen receptor (CAR) T-cell therapies are emerging as promising therapeutics for organ regeneration and as immunotherapy for various cancers. Despite significant progress having been made in these areas, there is still more to be learned to better understand the pharmacokinetics and pharmacodynamics of the administered therapeutic cells in the living system. For noninvasive, in vivo tracking of cells with positron emission tomography (PET), a novel [89Zr]Zr-p-isothiocyanatobenzyl-desferrioxamine ([89Zr]Zr-DBN)-mediated cell radiolabeling method has been developed utilizing 89Zr (t1/2 78.4 h). The present protocol describes a [89Zr]Zr-DBN-mediated, ready-to-use, radiolabeling synthon for direct radiolabeling of variety of cells, including mesenchymal stem cells, lineage-guided cardiopoietic stem cells, liver regenerating hepatocytes, white blood cells, melanoma cells, and dendritic cells. The developed methodology enables noninvasive PET imaging of cell trafficking for up to 7 days post-administration without affecting the nature or the function of the radiolabeled cells. Additionally, this protocol describes a stepwise method for the radiosynthesis of [89Zr]Zr-DBN, biocompatible formulation of [89Zr]Zr-DBN, preparation of cells for radiolabeling, and finally the radiolabeling of cells with [89Zr]Zr-DBN, including all the intricate details needed for the successful radiolabeling of cells.

Presented here is a protocol to radiolabel cells with a positron emission tomography (PET) radioisotope, 89Zr (t1/2 78.4 h), using a ready-to-use radiolabeling synthon, [89Zr]Zr-p-isothiocyanatobenzyl-desferrioxamine ([89Zr]Zr-DBN). Radiolabeling cells with [89Zr]Zr-DBN allows noninvasive tracking and imaging of administered radiolabeled cells in the body with PET for up to 7 days post-administration.

טומוגרפיה של פליטת פוזיטרונים הדמיה של סחר בתאים: שיטה של תיוג רדיו תאים

Stem cell and chimeric antigen receptor (CAR) T-cell therapies are emerging as promising therapeutics for organ regeneration and as immunotherapy for ...

Cancer Research

Initial Evaluation of Antibody-conjugates Modified with Viral-derived Peptides for Increasing Cellular Accumulation and Improving Tumor Targeting

Antibody-conjugates (ACs) modified with virus-derived peptides are a potentially powerful class of tumor cell delivery agents for molecular payloads used in cancer treatment and imaging due to increased cellular accumulation over current ACs. During early AC in vitro development, fluorescence techniques and radioimmunoassays are sufficient for determining intracellular localization, accumulation efficiency, and target cell specificity. Currently, there is no consensus on standardized methods for preparing cells for evaluating AC intracellular accumulation and localization. The initial testing of ACs modified with virus-derived peptides is critical especially if several candidates have been constructed. Determining intracellular accumulation by fluorescence can be affected by background signal from ACs at the cell surface and complicate the interpretation of accumulation. For radioimmunoassays, typically treated cells are fractionated and the radioactivity in different cell compartments measured. However, cell lysis varies from cell to cell and often nuclear and cytoplasmic compartments are not adequately isolated. This can produce misleading data on payload delivery properties. The intravenous injection of radiolabeled virus-derived peptide-modified ACs in tumor bearing mice followed by radionuclide imaging is a powerful method for determining tumor targeting and payload delivery properties at the in vivo phase of development. However, this is a relatively recent advancement and few groups have evaluated virus-derived peptide-modified ACs in this manner. We describe the processing of treated cells to more accurately evaluate virus-derived peptide-modified AC accumulation when using confocal microscopy and radioimmunoassays. Specifically, a method for trypsinizing cells to remove cell surface bound ACs. We also provide a method for improving cellular fractionation. Lastly, this protocol provides an in vivo method using positron emission tomography (PET) for evaluating initial tumor targeting properties in tumor-bearing mice. We use the radioisotope 64Cu (t1/2 = 12.7 h) as an example payload in this protocol.

Viral-derived peptides coupled to antibody-conjugates (ACs) is an approach gaining momentum due to the potential of delivering molecular payloads with increased tumor cell accumulation. Utilizing common methods to evaluate peptide conjugation, AC and payload intracellular accumulation, and tumor targeting, this protocol helps researchers during the key initial development phases.

ההערכה הראשונית של נוגדן-conjugates שונה עם פפטידים ויראלי-derived הגדלת לצבירה התאית ושיפור הגידול מיקוד

Antibody-conjugates (ACs) modified with virus-derived peptides are a potentially powerful class of tumor cell delivery agents for molecular payloads used ...

Murine Lymphocyte Labeling by 64Cu-Antibody Receptor Targeting for In Vivo Cell Trafficking by PET/CT

This protocol illustrates the production of 64Cu and the chelator conjugation/radiolabeling of a monoclonal antibody (mAb) followed by murine lymphocyte cell culture and 64Cu-antibody receptor targeting of the cells. In vitro evaluation of the radiolabel and non-invasive in vivo cell tracking in an animal model of an airway delayed-type hypersensitivity reaction (DTHR) by PET/CT are described.
In detail, the conjugation of a mAb with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) is shown. Following the production of radioactive 64Cu, radiolabeling of the DOTA-conjugated mAb is described. Next, the expansion of chicken ovalbumin (cOVA)-specific CD4+ interferon (IFN)-&#947;-producing T helper cells (cOVA-TH1) and the subsequent radiolabeling of the cOVA-TH1 cells are depicted. Various in vitro techniques are presented to evaluate the effects of 64Cu-radiolabeling on the cells, such as the determination of cell viability by trypan blue exclusion, the staining for apoptosis with Annexin V for flow cytometry, and the assessment of functionality by IFN-&#947; enzyme-linked immunosorbent assay (ELISA). Furthermore, the determination of the radioactive uptake into the cells and the labeling stability are described in detail. This protocol further describes how to perform cell tracking studies in an animal model for an airway DTHR and, therefore, the induction of cOVA-induced acute airway DHTR in BALB/c mice is included. Finally, a robust PET/CT workflow including image acquisition, reconstruction, and analysis is presented.
The 64Cu-antibody receptor targeting approach with subsequent receptor internalization provides high specificity and stability, reduced cellular toxicity, and low efflux rates compared to common PET-tracers for cell labeling, e.g.64Cu-pyruvaldehyde bis(N4-methylthiosemicarbazone) (64Cu-PTSM). Finally, our approach enables non-invasive in vivo cell tracking by PET/CT with an optimal signal-to-background ratio for 48 h. This experimental approach can be transferred to different animal models and cell types with membrane-bound receptors that are internalized.

Murine Lymphocyte Labeling by 64Cu-Antibody Receptor Targeting for In Vivo  Cell Trafficking by PET/CT

Following the preparation of a 64Cu-modified monoclonal antibody binding to a transgenic murine T cell receptor, T cells are radiolabeled in vivo, analyzed for viability, functionality, labeling stability and apoptosis, and adoptively transferred into mice with an airway delayed-type hypersensitivity reaction for non-invasive imaging by positron emission tomography/computed tomography (PET/CT).

Murine לימפוציטים תיוג ידי<sup&gt; 64</sup&gt; Cu-נוגדן קולטן מיקוד עבור<em&gt; In vivo</em&gt; סחר Cell על ידי PET / CT

This protocol illustrates the production of 64Cu and the chelator conjugation/radiolabeling of a monoclonal antibody (mAb) followed by murine lymphocyte ...

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