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.

Os estudos em animais foram aprovados pelo Conselho de Ética em Pesquisa Animal da Universidade McMaster, em conformidade com a Canadian Council on Animal Care (CCAC) orientações. 1. A radiomarcação de ligandos TZ-tridentados com 99m Tc CUIDADO: Os seguintes procedimentos requerem o uso de compostos radioactivos. O trabalho só deve ser feito em um laboratório licenciado com a adesão a normas de segurança e eliminação. reacções de micro-ondas deve ser realizada num forno de microondas especificamente concebido para a síntese química. <ol><li> Síntese de [99mTc (CO) 3 (H 2 O) 3] + 19, 20 <ol><li> Em um frasco de microondas, combinar 8 mg de K 2 [BH 3 CO 2], 15 mg de Na 2 CO 3, 20 mg de Na 2 B 4 O 7 · 10H 2 O e 25 mg KOCO [CH (OH)]2 COONa · 4H 2 O. Purge o frasco durante 10 min com gás argônio. </li><li> Adicionar 4 ml de 99m TcO ~ 4 - (1.100 MBq, ~ 30 mCi) em 0,9% de solução salina para o frasco. </li><li> Aquece-se a reacção num micro-ondas durante 3,5 minutos a 110 ° C, após 10 s de agitação para garantir uma mistura completa dos reagentes. </li><li> Ajuste o pH da solução para 3,5-4 com ~ 400 mL de HCl 1M. Verifique utilizando papel de pH. </li></ol></li><li> Radiomarcação de tetrazina ligantes 1-5 <ol><li> Dissolve-se 2 mg de cada ligando (compostos 1-5) em 250 mL de MeOH 21. </li><li> Adicionar 250 uL de [99mTc (CO) 3 (H 2 O) 3] + (~ 74 MBq, ~ 2 mCi) a cada solução. </li><li> Aquece-se a mistura de reacção utilizando um forno de microondas durante 20 min a 60 ° C. NOTA: Este passo foi idêntico para todos os 5 tetrazinas. </li><li> Para os compostos 2 a 5, evapora-se o solvente e re-dissolve os produtos resultantes em 1 mL de 1: v / v 1 DCM: TFA. </li><li> Aquecer os produtos de reacção dissolvidos (2-5) a 60 ° C em um micro-ondas durante 6 min (2-4) ou 10 min (5). </li><li> Após arrefecimento até à temperatura ambiente, evapora-se o solvente usando um evaporador (36 ° C, 8 mbar, 3 min, 6000 rpm) e dissolve-se o composto seco em 1: 1 de ACN: H 2 O ou 1: 1 de MeOH: H2O, antes da purificação por HPLC. </li><li> Purifica-se os compostos marcado com 99m Tc (1-5), incluindo a separação do produto marcado do ligando não marcado tetrazina, utilizando HPLC (C 18 de fase inversa). Tipicamente, usar um gradiente de eluição de 30:70 ACN: H 2 O (ambos com 0,1% de TFA) a 40:60 ACN: H2O ao longo de 20 min (18 min) e uma coluna analítica C 18 4,6 x 100 mm. Use tanto UV (254 nm) e detecção gama. <ol><li> Aqui uma pequena amostra de cada produto marcado e comparar o seu tempo de retenção HPLC para o de um co-injected, não radioactiva, marcada com Re padrão (0,125 mg em 20% de metanol-H2O). O padrão marcado com Re é identificada no rastreio de UV HPLC, e eluir, ao mesmo tempo que o composto 99m Tc-rotulada no rastreio γ-HPLC. Esta co-injecção mostra picos em tempos de retenção semelhantes, o que confirma a identidade do composto de 99m Tc-rotulados. </li></ol></li><li> Evapora-se o solvente a partir das fracções de HPLC utilizando um evaporador (36 ° C, 8 mbar, 3 min, 6000 rpm). </li><li> Formular o composto purificado, a uma concentração de 7,4 kBq / mL em PBS, contendo BSA a 0,5% e 0,01% de Tween-80. </li><li> Para garantir os compostos marcados são estáveis, realizar um estudo de estabilidade in vitro. Incubar o composto formulado a 37 ° C durante 1, 4 e 6 h, injectando uma pequena quantidade (3,7 MBq) da mistura em HPLC em cada ponto de tempo para avaliar a estabilidade. </li></ol></li></ol> 2. Estudos Bio-distribuição Pré-alvo <ol><li&gt; Preparação de animais <ol><li> Utilizando ratos fêmeas de 7-9 semanas de idade, ratinhos Balb / c (n = 3), administrar TCO-BP formulado em solução salina (20 mg / kg) (5 mg / mL), por via de injecção na veia da cauda-. </li><li> Coloque o mouse no dispositivo de contenção física, e identificar as veias localizadas nas superfícies laterais da cauda e limpe com um algodão embebido em álcool. Em cerca de 2 cm da extremidade da cauda, ​​inserir uma agulha de calibre 30 a um ângulo raso, paralelo à veia. Lentamente pressionar o êmbolo para injetar, remova a agulha e aplicar gaze limpa no local da injecção com uma ligeira pressão até o sangramento parar. </li><li> A 1 h após a injecção de TCO-BP, administrar ~ 0,74 MBq (20 uCi) de 99m Tc-tetrazina formulados em 100 ul de 0,5% de BSA, 0,01% de Tween-80 em PBS, através de injecção na veia da cauda. </li></ol></li><li> Estudos biológicos e de distribuição <ol><li> No ponto de tempo desejado (t = 6 H), anestesiar os ratos utilizando 3% de isoflurano e mistura gasosa de oxigénio de 2%. Demonstrar uma parae pitada retirada no rato anestesiado para garantir que eles estão em plano cirúrgico de anestesia. </li><li> Recolha de sangue (1 mL) através de punção cardíaca utilizando uma seringa pré-tratada com heparina. Colocar o mouse sobre as suas costas com o nariz no cone do nariz para anestesia continuou e localizar o apêndice xifóide no animal. <ol><li> Inserir uma agulha G 25, ligeiramente à esquerda da linha média do animal no âmbito do processo xifóide, em um ângulo de 20 °. Totalmente inserir a agulha, e, lentamente, puxar o êmbolo para ver sangue no centro da agulha se o coração foi perfurado. Ligeiramente reajustar a agulha, mantendo o êmbolo, se necessário, para perfurar o coração. Lentamente extrair o sangue para dentro da seringa. </li></ol></li><li> Eutanásia do animal por deslocamento cervical, sob anestesia. </li><li> Coloque cada animal em um saco plástico e usar um calibrador de dose (configuração Tc 99m) para medir todo o nível de atividade do corpo. </li><li> Coletar os seguintes tecidos e fluidos em pré-pesamed contando tubos: sangue, osso (joelho e ombro), vesícula biliar, rins, fígado, estômago (com conteúdo), intestino delgado (com conteúdo), intestino grosso e ceco (com conteúdo), tireóide e traqueia, bexiga com urina , e cauda. </li><li> Lavar tecidos apropriados (excluindo sangue, vesícula biliar e bexiga urinária) em PBS para remover o sangue e secar antes de colocar os tecidos em tubos de contagem adequadas. </li><li> Coloque carcaça de animal em um saco plástico e medir a atividade do corpo inteiro residual usando um calibrador de dose. </li><li> Pesar cada tubo que contém uma amostra de tecido. Subtrair o peso inicial do tubo para obter uma massa de tecido. </li><li> Usar um calibrador de dose (99m Tc definição) para medir a quantidade de actividade de uma amostra de teste (100 uL) no momento da injecção para cada rato. NOTA: Esta amostra teste é igual ao volume de injecção, dando, assim, a contagem de actividade no momento da injecção. </li><li> Na altura da medição do tecido, umaliquot 5 uL da amostra de teste utilizado anteriormente. Utilizar um contador de raios gama múltiplos detectores (configuração Tc 99m) e contam para obter a contagem por minuto (CPM) para a amostra de teste de 5 mL. </li><li> Use os dois valores obtidos em 2.2.9 e 2.2.10 para calcular a atividade e relacionamento CPM usando a equação 1 para obter um factor de conversão (CPM uCi -1). (1) <img alt="equação 1" src="/files/ftp_upload/55188/55188eq1.jpg" /></li><li> Utilizar o contador gama para medir a quantidade de radioactividade em cada tecido ou amostra de fluido. </li><li> Use equação 1 para calcular a quantidade de actividade em cada tecido ou fluido no momento da medição em relação à dose total injectada. Este valor é em seguida normalizado pelo peso do órgão e relatados como percentagem da dose injectada por grama (ou seja,% ID / g) de tecido. </li><li> Siga os passos 2.1.2 a 2.2.13 para conduzir um experimento de controle negativo usando os marcado com 99m Tc ligantes tetrazina na Absence de TCO-BP. Sacrifício ratinhos (n = 3) em 0,5, 1, 4 e 6 h pós-injecção e obter o tecido ou fluido, tal como descrito acima. </li></ol></li></ol>

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The authors declare they have no competing financial interests.

Uma colecção de quelatos tridentados ligada-tetrazina de polaridades diferentes foi preparado, e a utilidade dos seus complexos 99mTc na reacção com um derivado IEDDA TCO in vivo foi avaliada. Um método eficaz e reprodutível rotulagem 99m Tc foi desenvolvido para cinco tetrazina-quelatos, onde a concentração de ligando foi 10 -3 M. A etapa de marcação foi seguida por desprotecção de t- butilo (para os compostos 2-5). A elevada concentração...

99m Tc continua a ser o radioisótopo dominante usada na medicina nuclear de diagnóstico, com mais de 50 milhões de procedimentos de imagem realizados por ano em todo o mundo 1, 2, 3. A maioria dos 99m agentes Tc utilizadas clinicamente são do tipo de perfusão radiofármacos. Há um número limitado de compostos-alvo de forma activa em que o 99mTc é dirigido para se ligar a um biomarcador específico através da ligação a uma construção de direccionamento. A criação de 99m alvo radiofármacos Tc é frequentemente prejudicado pela influência de 99m de complexos de Tc-ligando sobre a capacidade da molécula de direccionamento para ligar o biomarcador de interesse, ou os isótopos de meia-vida não é suficiente para utilização com biomoléculas peso molecular mais elevado tais como anticorpos. O último requer tipicamente vários dias antes de as imagens são adquiridas para que a biomolécula para limpar a partir de não-alvo tiss<html> ues. Pré-segmentação oferece uma abordagem alternativa para superar esses desafios. Pré-segmentação combinada com a química bioorthogonal tem demonstrado ser uma forma eficaz de desenvolver novas sondas imagem molecular para ambos fluorescência e radio-imagiologia 4, 5, 6, 7, 8. A reacção inversa de electrões demanda de Diels-Alder (IEDDA) entre derivados -cicloocteno trans (TCO) 1,2,4,5-tetrazina (Tz) e, como se mostra na Figura 1, tem sido demonstrado ser particularmente eficaz 6. A reação IEDDA com estes componentes podem apresentar cinética rápida na PBS (k 2 ≈ 6.000 M -1 s -1) e alta seletividade, sendo ideal para aplicações in vivo pré-segmentação 9, 10. e_content &quot;&gt; A abordagem mais comum utilizado envolve a administração de um vector de TCO-derivado de segmentação e depois de um período de atraso suficiente, uma tetrazina radiomarcado é administrado. tetrazinas marcados radioactivamente com base em 11 C, 18 F, 64 Cu, 89 Zr, e 111 no foram relataram 11, 12, 13, 14, 15. em contraste, há apenas um relatório de um marcado com 99m Tc Tz, o qual foi preparado usando um tipo de ligando HYNIC requerendo o uso de co-ligandos para prevenir a ligação e degradação de proteínas in vivo 16. Como alternativa, relatamos aqui a síntese de 99m Tc (I) marcado tetrazinas usando uma família de ligandos que formam complexos estáveis com um tridentados [99mTc (CO) 3] + núcleo. Figura 1: A reacção IEDDA bioorthogonal entre tetrazina e -cicloocteno trans. <a href="http://ecsource.jove.com/files/ftp_upload/55188/55188fig1large.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> A família de ligandos preparados contêm quelatos tridentados que variam em polaridade e da natureza do grupo de ligação entre a região de ligação do metal e a Tz (Figura 2). O objetivo foi identificar a 99m Tc-tetrazina construir que poderiam efetivamente localizar e reagir com os locais TCO marcados in vivo e rapidamente claro, não ligadas, a fim de produzir alta meta-se não-alvo rácios. Para testar os ligandos, um TCO-derivado de um bisfosfonato (TCO-PA) foi utilizado 17. Nós mostramos anteriormente que TCO-BP localiza a áreas do metabolismo ósseo activo e pode reagir comtetrazinas radiomarcados in vivo 18. É um reagente conveniente para testar novas tetrazinas, porque ele pode ser preparado num único passo e experiências podem ser realizadas em ratinhos normais onde a localização ocorre principalmente nas articulações (joelhos e ombros).

<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.

Os ligandos foram sintetizados utilizando diferentes ligantes e agentes quelantes através de um simples estratégia de aminação redutiva (Figura 2), seguido por acoplamento do produto a um tetrazina comercialmente disponíveis 22, 23. A marcação radioactiva foi realizada utilizando o mesmo método para todos os compostos e era altamente reprodutível. O processo foi optimizado variando o pH, a quantidade de ...

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.

Preparação e Avaliação de<sup&gt; 99m</sup&gt; Tc-rotulados tridentadas Quelatos de Pré-alvo Usando Bioorthogonal Química

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 de Cartagena UDEC

Research

JoVE Journal

Chemistry

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

8.1K visualizações.  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. 

Vídeo: 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 Reação Capture-cicloadição para imobilizar reversível pequenas moléculas ou estruturas multi-componentes para aplicações de biossensores

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

Química

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.

O bioconjugação e radiossíntese de 89 Anticorpos Zr-DFO-rotulados

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.

Um protocolo otimizado para a radiomarcação eficiente de nanopartículas de ouro usando um<sup&gt; 125</sup&gt; Marcado com Eu Azida grupo prostético

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.

Aproveitando a demanda Bioorthogonal Inverse Electron Diels-Alder para Pretargeted PET Imagem

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

Bioengenharia

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 Imagem Molecular do cancro da próstata com um pequeno Molecular CLT1 Peptide alvejado agente de contraste

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 baseado na reação de Diels-Alder de demanda inversa elétron

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.

Síntese e Bioconjugation dos reagentes Thiol-reativa para a criação de Site-seletivamente modificado 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.

Imagem por Tomografia por Emissão de Pósitrons do Tráfico Celular: Um Método de Radiomarcação Celular

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

Pesquisa do câncer

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.

Avaliação inicial do anticorpo cojugado modificado com peptídeos virais-derivado para aumentar a acumulação celular e melhorando o direcionamento do Tumor

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 Linfócitos Rotulagem por<sup&gt; 64</sup&gt; Cu-Antibody Receptor Segmentação para<em&gt; In Vivo</em&gt; Tráfico celular por 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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