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.

Gli studi sugli animali sono stati approvati dal Consiglio di Ricerca Etica degli animali alla McMaster University in accordo con il Consiglio Canadese Animal Care (CCAC) le linee guida. 1. radiomarcatura di ligandi Tz-tridentati con 99m Tc NOTA: Le seguenti procedure richiedono l&#39;uso di composti radioattivi. Il lavoro dovrebbe essere fatto solo in un laboratorio autorizzato con aderenza alle norme di sicurezza e di smaltimento. reazioni microonde devono essere eseguiti in un forno a microonde specificamente progettato per sintesi chimica. <ol><li> Sintesi di [99m Tc (CO) 3 (H 2 O) 3] + 19, 20 <ol><li> In una fiala forno a microonde, unire 8 mg K 2 [BH 3 CO 2], 15 mg di Na 2 CO 3, 20 mg di Na 2 B 4 O 7 · 10H 2 O, e 25 mg KOCO [CH (OH)]2 COONa · 4H 2 O. spurgo la fiala per 10 minuti con gas argon. </li><li> Aggiungere 4 ml di 99m TcO 4 - (~ 1.100 MBq, ~ 30 MCI) in soluzione fisiologica 0,9% al flaconcino. </li><li> Riscaldare la reazione in un forno a microonde per 3,5 min a 110 ° C dopo 10 s di agitazione per assicurare una completa miscelazione dei reagenti. </li><li> Regolare il pH della soluzione a 3,5-4 utilizzando ~ 400 ml di 1 M HCl. Verificare utilizzando carta pH. </li></ol></li><li> Radiomarcatura di tetrazina ligandi 1-5 <ol><li> Sciogliere 2 mg di ciascun ligando (composti 1-5) in 250 ml MeOH 21. </li><li> Aggiungere 250 ml di [99m Tc (CO) 3 (H 2 O) 3] + (~ 74 MBq, ~ 2 MCI) a ogni soluzione. </li><li> Riscaldare la miscela di reazione utilizzando un forno per 20 minuti a 60 ° C. NOTA: Questo passaggio era identica per tutti i 5 tetrazines. </li><li> Per composti 2- 5, si evapora il solvente e re-dissolve i prodotti risultanti in 1 ml di 1: 1 v / v DCM: TFA. </li><li> Riscaldare i prodotti di reazione disciolti (2-5) a 60 ° C in un forno a microonde per 6 minuti (2-4) o 10 min (5). </li><li> Dopo raffreddamento a temperatura ambiente, si evapora il solvente usando un evaporatore (36 ° C, 8 mbar, 3 min, 6.000 rpm) e sciogliere il composto essiccato in 1: 1 ACN: H 2 O o 1: 1 MeOH: H 2 O, prima purificazione HPLC. </li><li> Purificare i 99m Tc-marcato composti (1-5), tra cui la separazione del prodotto etichettato da senza etichetta ligando tetrazina, utilizzando HPLC (C 18 in fase inversa). Tipicamente, utilizzare un gradiente di eluizione di 30:70 ACN: H 2 O (entrambi con 0,1% TFA) a 40:60 ACN: H 2 O oltre 20 min (18 min) e una analitica colonna C 18 4,6 x 100 mm. Utilizzare sia UV (254 nm) e la rilevazione di gamma. <ol><li> Prendere un piccolo campione di ciascun prodotto etichettato e confrontare il suo tempo di ritenzione HPLC a quella di un co-injette, non radioattivo, standard di Re-marcato (0,125 mg nel 20% di metanolo-H 2 O). Lo standard Re-marcato è identificato nella traccia UV HPLC, e verrà eluire al tempo stesso come il 99m Tc composto marcato nella traccia γ-HPLC. Questa co-iniezione mostra picchi a tempi di ritenzione comparabili, confermando l&#39;identità del 99m Tc-etichettato compound. </li></ol></li><li> Evaporare il solvente dalle frazioni HPLC utilizzando un evaporatore (36 ° C, 8 mbar, 3 min, 6,000 rpm). </li><li> Formulare il composto purificato ad una concentrazione di 7,4 kBq / ml in PBS, contenente 0,5% di BSA e 0,01% Tween-80. </li><li> Per garantire i composti marcati sono stabili, effettuare uno studio in vitro stabilità. Incubare il composto formulato a 37 ° C per 1, 4 e 6 h, iniettando una piccola quantità (3,7 MBq) della miscela sulla HPLC ad ogni tempo per valutare la stabilità. </li></ol></li></ol> 2. Studi Bio-Pre-distribuzione mirati <ol><li&gt; Preparazione degli animali <ol><li> Utilizzando 7-9 settimane di età, i topi femmina BALB / c (n = 3), amministrare TCO-BP formulato in soluzione salina (20 mg / kg) (5 mg / mL), mediante iniezione coda vena. </li><li> Posizionare il mouse in un dispositivo di contenzione fisica, e identificare le vene situate sulle superfici laterali della coda e pulire con un tampone imbevuto di alcol. A circa 2 cm dall&#39;estremità della coda, inserire un ago da 30 gauge con un angolo basso, parallelamente alla vena. Premere lentamente lo stantuffo per iniettare, rimuovere l&#39;ago ed applicare pulita garza al sito di iniezione con una leggera pressione fino a quando si arresta l&#39;emorragia. </li><li> Al 1 ore dopo l&#39;iniezione di TCO-BP, amministrare ~ 0,74 MBq (20 pCi) di 99m Tc-tetrazina formulati in 100 ml di 0,5% di BSA, 0,01% di Tween-80 in PBS, tramite iniezione coda vena. </li></ol></li><li> Studi Bio-distribuzione <ol><li> Al punto di tempo desiderato (t = 6 h), anestetizzare i topi utilizzando 3% isoflurano e miscela gassosa di ossigeno 2%. Dimostrare un ae un pizzico di ritiro sul mouse anestetizzato per assicurare che siano in aereo chirurgico di anestesia. </li><li> Raccogliere il sangue (1 mL) mediante puntura cardiaca usando una siringa pre-trattati con eparina. Posizionare il mouse sul dorso con il naso nel cono di naso per continuare l&#39;anestesia e individuare il processo xifoideo sull&#39;animale. <ol><li> Inserire un ago G 25, leggermente a sinistra della linea mediana dell&#39;animale sotto il processo xifoideo, ad un angolo di 20 °. Inserire completamente l&#39;ago, e lentamente tirare indietro lo stantuffo per vedere il sangue nel mozzo ago se il cuore è stato perforato. Leggermente regolare nuovamente l&#39;ago tenendo lo stantuffo se necessario, forare il cuore. Lentamente prelevare il sangue nella siringa. </li></ol></li><li> Eutanasia dell&#39;animale mediante dislocazione cervicale, mentre sotto anestesia. </li><li> Mettere ogni animale in un sacchetto di plastica e utilizzare un calibratore di dosi (99m impostazione Tc) per misurare tutto il livello di attività del corpo. </li><li> Raccogliere i seguenti tessuti e fluidi in pre-pesareEd contando tubi: sangue, midollo (ginocchio e della spalla), cistifellea, reni, fegato, dello stomaco (con il contenuto), piccolo intestino (con il contenuto), intestino crasso e cieco (con il contenuto), tiroide e trachea, vescica urinaria con l&#39;urina , e la coda. </li><li> Risciacquare tessuti idonei (ad esclusione del sangue, della cistifellea e vescica urinaria) in PBS per rimuovere il sangue e asciugare prima di mettere i tessuti nelle provette di conteggio appropriati. </li><li> Mettere carcassa animale in un sacchetto di plastica e misurare l&#39;attività residua di tutto il corpo con un calibratore di dosi. </li><li> Pesare ciascuna provetta contenente un campione di tessuto. Sottrarre peso iniziale del tubo per ottenere la massa del tessuto. </li><li> Utilizzare un calibratore di dosi (99m Tc impostazione) per misurare la quantità di attività in un campione di prova (100 mL) al momento dell&#39;iniezione per ogni mouse. NOTA: Questo campione è uguale al volume di iniezione, dando così il conteggio attività al momento dell&#39;iniezione. </li><li> Al momento della misurazione del tessuto, unliquot 5 ml di campione usato in precedenza. Utilizzare un contatore gamma multi-detector (99m impostazione Tc) e contare per ottenere il conteggio al minuto (CPM) per il campione 5 ml. </li><li> Utilizzare i due valori ottenuti in 2.2.9 e 2.2.10 per calcolare l&#39;attività e rapporto CPM con l&#39;equazione 1 per ottenere un fattore di conversione (CPM pCi -1). (1) <img alt="Equazione 1" src="/files/ftp_upload/55188/55188eq1.jpg" /></li><li> Utilizzare il contatore gamma per misurare la quantità di radioattività in ogni tessuto o campione di fluido. </li><li> Utilizzare equazione 1 per calcolare la quantità di attività in ciascun tessuto o fluido al momento della misura relativa alla dose totale iniettata. Questo valore viene quindi normalizzata per il peso degli organi e riportato come la dose percentuale iniettata per grammo (cioè,% ID / g) di tessuto. </li><li> Seguire i passaggi 2.1.2 a 2.2.13 per condurre un esperimento di controllo negativo utilizzando i 99m Tc-marcato ligandi tetrazina nel Absence di TCO-BP. topi sacrificio (n = 3) a 0.5, 1, 4 e 6 ore dopo l&#39;iniezione ed ottenere tessuti o fluidi come sopra descritto. </li></ol></li></ol>

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The authors declare they have no competing financial interests.

Una collezione di tetrazina linked chelati tridentati di polarità variabile è stata preparata, e l&#39;utilità dei loro complessi 99m Tc nella reazione IEDDA con un derivato TCO in vivo è stata valutata. Un metodo di etichettatura 99m Tc efficace e riproducibile stato sviluppato per cinque tetrazina chelati, dove la concentrazione del ligando era 10 -3 M. Il passo etichettatura è stata seguita da deprotezione del t-butil (per i composti 2-5). L&#39...

99m Tc rimane il radioisotopo dominante utilizzato in medicina nucleare diagnostica, con oltre 50 milioni di procedure di imaging condotti ogni anno in tutto il mondo 1, 2, 3. La maggior parte degli agenti 99m Tc usati clinicamente sono di tipo perfusione radiofarmaci. Ci sono un numero limitato di composti mirati attivamente in cui 99m Tc è diretto ad associare un biomarker specifico mediante legatura ad un costrutto targeting. La creazione di 99m mirata Tc radiofarmaci è spesso ostacolato dalla influenza di 99m complessi Tc-ligando sulla capacità della molecola targeting impegnare la biomarker di interesse, o gli isotopi emivita non è sufficiente per l&#39;utilizzo con elevate biomolecole peso molecolare come gli anticorpi. Quest&#39;ultimo richiede tipicamente diversi giorni prima immagini sono acquisite in modo che la biomolecola cancellare da non bersaglio tiss<html> UES. Pre-targeting offre un approccio alternativo per superare queste sfide. Pre-targeting combinato con la chimica bioorthogonal ha dimostrato di essere un modo efficace per sviluppare nuove sonde imaging molecolare sia per fluorescenza e radio imaging 4, 5, 6, 7, 8. La domanda di elettroni inversa Diels-Alder (IEDDA) reazione tra 1,2,4,5-tetrazina (Tz) e derivati -cyclooctene trans (TCO), come mostrato nella Figura 1, ha dimostrato di essere particolarmente efficace 6. La reazione IEDDA con questi componenti può esibire una rapida cinetica in PBS (k 2 ≈ 6.000 M -1 s -1) e alta selettività, che lo rende ideale per in vivo pre-targeting applicazioni 9, 10. e_content &quot;&gt; L&#39;approccio più comune utilizzato implica la gestione di un vettore targeting TCO-derivati e dopo un periodo di ritardo sufficiente, un tetrazina radioattivo viene somministrato. tetrazines radioattivo sulla base di 11 C, 18 F, 64 Cu, 89 Zr, e 111 sono stati segnalato 11, 12, 13, 14, 15. al contrario, c&#39;è solo un rapporto di un 99m Tc-etichettato Tz, che è stato preparato utilizzando un tipo ligando HYNIC richiedere l&#39;uso di co-ligandi per prevenire legame proteico e la degradazione in vivo 16. in alternativa, riportiamo qui la sintesi di 99m Tc (I) etichettato tetrazines utilizzando una famiglia di leganti che formano complessi stabili con tridentati [99m Tc (CO) 3] + nucleo. Figura 1: La reazione IEDDA bioorthogonal tra tetrazina e -cyclooctene trans. <a href="https://ecsource-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/55188/55188fig1large.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> La famiglia di leganti preparati contengono chelati tridentati che variano in polarità e la natura del gruppo linker tra la regione di legame del metallo e Tz (Figura 2). L&#39;obiettivo era quello di individuare una 99m Tc-tetrazina costrutto che potrebbe efficacemente localizzare e reagire con i siti TCO-etichettati in vivo e rapidamente chiaro non collegate, al fine di produrre alta target-to-non-bersaglio rapporti. Per testare i ligandi, un TCO-derivato di un bisfosfonato (TCO-BP) è stato utilizzato 17. Abbiamo dimostrato in precedenza che il TCO-BP localizza alle aree di metabolismo osseo attivo e può reagire contetrazines radiomarcati in vivo 18. È un reagente conveniente per testare nuove tetrazines, perché può essere preparato in un&#39;unica fase e gli esperimenti può essere eseguita in topi normali dove localizzazione luogo soprattutto nelle articolazioni (ginocchia e spalle).

<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.

I leganti sono stati sintetizzati utilizzando diversi linker e chelanti tramite una semplice strategia amminazione riduttiva (figura 2), seguita da accoppiamento del prodotto ad un tetrazina disponibile in commercio 22, 23. Radiomarcatura è stata effettuata utilizzando lo stesso metodo per tutti i composti ed era altamente riproducibile. Il processo è stato ottimizzato variando il pH, quantità di ligando, temp...

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.

Preparazione e valutazione di<sup&gt; 99m</sup&gt; Tc marcato tridentate chelati di pre-targeting Utilizzando Bioorthogonal Chimica

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

preparation-evaluation-99mtc-labeled-tridentate-chelates-for-pre

Universidad San Sebastian

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 On-chip Capture-cicloaddizione Reazione di immobilizzare reversibilmente piccole molecole o strutture multi-componenti per applicazioni Biosensor

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

Ricerca

Chimica

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.

Il bioconjugation e radiosintesi di<sup&gt; 89</sup&gt; Anticorpi Zr-DFO-etichettati

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.

Un protocollo ottimizzato per la radiomarcatura efficiente di oro nanoparticelle utilizzando un<sup&gt; 125</sup&gt; Azide gruppo I-etichettati protesico

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.

Sfruttando la domanda Bioorthogonal Inverse Electron Diels-Alder cicloaddizione per 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 ...

Bioingegneria

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 Imaging Molecolare del cancro alla prostata con un piccolo Molecular CLT1 Peptide mirato di contrasto agente

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

Medicina

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.

Pretargeted Radioimmunotherapy basato sulla reazione di Diels-Alder domanda inversa Electron

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.

Sintesi e Bioconjugation di tiolo-reattive reagenti per la creazione del sito-selettivamente per volta efattori

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.

Tomografia a emissione di positroni Imaging del traffico cellulare: un metodo di radiomarcatura cellulare

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

Ricerca sul cancro

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.

Valutazione iniziale di anticorpo-coniugati modificate con peptidi virali-derivati per accumulo cellulare di aumentare e migliorare il Targeting tumorale

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).

Murino linfociti Etichettatura da<sup&gt; 64</sup&gt; Cu-anticorpo recettore Targeting per<em&gt; In Vivo</em&gt; Cell Traffico da 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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