Há mais de 50 anos os geradores de 68Ge/68Ga vêm sendo desenvolvidos, obtendo o 68Ga sem a necessidade da instalação de um cíclotron próximo à radiofarmácia ou ao centro hospitalar que tenha um PET/CT. O 68Ga é um emissor de pósitron com baixa emissão de fóton (β+, 89%, 1077 keV) e meia vida de 67,7 minutos, compatível com a farmacocinética de moléculas de baixo peso molecular, como peptídeos e fragmentos de anticorpos. Além disso, a química do Ga permite a ligação estável com agentes quelantes acoplados com peptídeos, como o DOTA. Todas estas características do 68Ga aliado a tecnologia PET/CT permitiram avanços em imagem molecular, como no diagnóstico de doenças de origem neuroendócrina. Entretanto, o eluato de 68Ga proveniente dos geradores de 68Ge/68Ga comerciais, ainda contém altos níveis de contaminantes, como o 68Ge e outros metais que competem quimicamente com o 68Ga, como o Fe3+ e Zn2+ e, como consequência, há redução do rendimento de marcação com biomoléculas. Quanto menor a quantidade de impurezas no eluato, a competição entre o peptídeo radiomarcado e peptídeo não marcado será menor e a qualidade de imagem será melhor, por isso existe a necessidade de diminuir a quantidade destes metais. Portanto, os objetivos deste trabalho são avaliar os métodos de purificação do 68Ga para a marcação de biomoléculas, com ênfase no estudo das impurezas químicas presentes nos radioisótopos primários, e desenvolver um método de purificação inédito. Diversos métodos de purificação foram estudados. Na purificação em resina catiônica tradicional e comercial, em que o 68Ga é adsorvido em resina catiônica e eluído em uma solução de acetona/ácido, a resina utilizada não é disponível comercialmente. Várias resinas catiônicas foram testadas simulando o processo comercial, e o uso das menores partículas da resina catiônica AG50W-X4 (200-400 mesh) foi a que apresentou os melhores resultados. Um método inovador foi a cromatografia por extração, onde o éter diisopropílico é adsorvido em resina XAD 16 e o 68Ga eluído em água deionizada. Apesar dos resultados de recuperação do 68Ga e a separação entre o 68Ga e o 65Zn terem sido bons, não houve reprodutibilidade na purificação dos metais. O método mais promissor e inédito foi a purificação do 68Ga em resina catiônica em meio básico que apresentou bons resultados, principalmente em relação à redução do Zn (98 ± 2)%, o contaminante químico encontrado em maior abundância no eluato de 68Ga. A redução total de impurezas foi (95 ± 4)%. Os peptídeos DOTATOC/DOTATATO foram marcados com o 68Ga em três diferentes formas: purificado em meio básico, por extração por solventes e sem a purificação prévia, o melhor resultado de rendimento de marcação do 68Ga DOTATATO foi obtido após a purificação do 68Ga em meio básico, comprovando a eficiência do processo. / For more than fifty years, the long-lived 68Ge/68Ga generators have been in development, obtaining 68Ga without the need of having in house cyclotron, which is a considerable convenience for PET centers that have no nearby cyclotrons. 68Ga decays 89% by positron emission and low photon emission (1077 keV) and the physical half life of 67.7 minutes is compatible with the pharmacokinetics of low biomolecular weight substances like peptides and antibody fragments. Moreover, its established metallic chemistry allows it to be stably bound to the carrier peptide sequence via a suitable bifunctional chelator, such as DOTA. All these reasons together with the technology of PET/CT allowed advances in molecular imaging, in particular in the diagnosis of neuroendocrine diseases. However, the eluate from the commercial 68Ge/68Ga generators still contains high levels of long lived 68Ge, besides other metallic impurities, which competes with 68Ga with a consequent reduction of the labeling yield of biomolecules, such as Fe3+ and Zn2+. Thus, the lower the amount of impurities in the eluate, the competition between the radiolabeled and unlabeled peptide by the receptor will be smaller and the quality of imaging will be better, a subsequent purification step is needed after the generator elution. The aim of this work is to evaluate different purifications methods of 68Ga to label biomolecules, with emphasis on the study of the chemical impurities contained in the eluate and to develop a new purification method. Several purification methods were studied. Many cationic resin were tested simulating the commercial process. 68Ga is adsorbed in cationic resin, which is not commercial available and eluted in acid/acetone solution. The use of minor particles of cationic resin AG50W-X4 (200-400 mesh) showed the best results. An innovate method was the extraction chromatography, wich is based on the absorption of diisopropyl ether in XAD 16 and 68Ga recovery in deionized water. Although the results regarding to 68Ga recovery and the radiochemical separation between 68Ga and 65Zn were excellent, there was no reproducibility on the purification of metals. The most promising and innovative method was the 68Ga purification performed by cationic resin in basic media, which presented the best results, especially regarding the Zn reduction (98 ± 2)%, the chemical contaminant found in great abundance in 68Ga eluate. The total impurities reduction was (95 ± 4)%. The peptides DOTATOC/DOTATATE were labeled 68Ga in three different forms: purified 68Ga in basic solution, through solvent extraction and no purified 68Ga. The best result was achieved with DOTATATE labeling with purified 68Ga in basic media, proving the purification process efficiency.

Há mais de 50 anos os geradores de 68Ge/68Ga vêm sendo desenvolvidos, obtendo o 68Ga sem a necessidade da instalação de um cíclotron próximo à radiofarmácia ou ao centro hospitalar que tenha um PET/CT. O 68Ga é um emissor de pósitron com baixa emissão de fóton (β+, 89%, 1077 keV) e meia vida de 67,7 minutos, compatível com a farmacocinética de moléculas de baixo peso molecular, como peptídeos e fragmentos de anticorpos. Além disso, a química do Ga permite a ligação estável com agentes quelantes acoplados com peptídeos, como o DOTA. Todas estas características do 68Ga aliado a tecnologia PET/CT permitiram avanços em imagem molecular, como no diagnóstico de doenças de origem neuroendócrina. Entretanto, o eluato de 68Ga proveniente dos geradores de 68Ge/68Ga comerciais, ainda contém altos níveis de contaminantes, como o 68Ge e outros metais que competem quimicamente com o 68Ga, como o Fe3+ e Zn2+ e, como consequência, há redução do rendimento de marcação com biomoléculas. Quanto menor a quantidade de impurezas no eluato, a competição entre o peptídeo radiomarcado e peptídeo não marcado será menor e a qualidade de imagem será melhor, por isso existe a necessidade de diminuir a quantidade destes metais. Portanto, os objetivos deste trabalho são avaliar os métodos de purificação do 68Ga para a marcação de biomoléculas, com ênfase no estudo das impurezas químicas presentes nos radioisótopos primários, e desenvolver um método de purificação inédito. Diversos métodos de purificação foram estudados. Na purificação em resina catiônica tradicional e comercial, em que o 68Ga é adsorvido em resina catiônica e eluído em uma solução de acetona/ácido, a resina utilizada não é disponível comercialmente. Várias resinas catiônicas foram testadas simulando o processo comercial, e o uso das menores partículas da resina catiônica AG50W-X4 (200-400 mesh) foi a que apresentou os melhores resultados. Um método inovador foi a cromatografia por extração, onde o éter diisopropílico é adsorvido em resina XAD 16 e o 68Ga eluído em água deionizada. Apesar dos resultados de recuperação do 68Ga e a separação entre o 68Ga e o 65Zn terem sido bons, não houve reprodutibilidade na purificação dos metais. O método mais promissor e inédito foi a purificação do 68Ga em resina catiônica em meio básico que apresentou bons resultados, principalmente em relação à redução do Zn (98 ± 2)%, o contaminante químico encontrado em maior abundância no eluato de 68Ga. A redução total de impurezas foi (95 ± 4)%. Os peptídeos DOTATOC/DOTATATO foram marcados com o 68Ga em três diferentes formas: purificado em meio básico, por extração por solventes e sem a purificação prévia, o melhor resultado de rendimento de marcação do 68Ga DOTATATO foi obtido após a purificação do 68Ga em meio básico, comprovando a eficiência do processo. / For more than fifty years, the long-lived 68Ge/68Ga generators have been in development, obtaining 68Ga without the need of having in house cyclotron, which is a considerable convenience for PET centers that have no nearby cyclotrons. 68Ga decays 89% by positron emission and low photon emission (1077 keV) and the physical half life of 67.7 minutes is compatible with the pharmacokinetics of low biomolecular weight substances like peptides and antibody fragments. Moreover, its established metallic chemistry allows it to be stably bound to the carrier peptide sequence via a suitable bifunctional chelator, such as DOTA. All these reasons together with the technology of PET/CT allowed advances in molecular imaging, in particular in the diagnosis of neuroendocrine diseases. However, the eluate from the commercial 68Ge/68Ga generators still contains high levels of long lived 68Ge, besides other metallic impurities, which competes with 68Ga with a consequent reduction of the labeling yield of biomolecules, such as Fe3+ and Zn2+. Thus, the lower the amount of impurities in the eluate, the competition between the radiolabeled and unlabeled peptide by the receptor will be smaller and the quality of imaging will be better, a subsequent purification step is needed after the generator elution. The aim of this work is to evaluate different purifications methods of 68Ga to label biomolecules, with emphasis on the study of the chemical impurities contained in the eluate and to develop a new purification method. Several purification methods were studied. Many cationic resin were tested simulating the commercial process. 68Ga is adsorbed in cationic resin, which is not commercial available and eluted in acid/acetone solution. The use of minor particles of cationic resin AG50W-X4 (200-400 mesh) showed the best results. An innovate method was the extraction chromatography, wich is based on the absorption of diisopropyl ether in XAD 16 and 68Ga recovery in deionized water. Although the results regarding to 68Ga recovery and the radiochemical separation between 68Ga and 65Zn were excellent, there was no reproducibility on the purification of metals. The most promising and innovative method was the 68Ga purification performed by cationic resin in basic media, which presented the best results, especially regarding the Zn reduction (98 ± 2)%, the chemical contaminant found in great abundance in 68Ga eluate. The total impurities reduction was (95 ± 4)%. The peptides DOTATOC/DOTATATE were labeled 68Ga in three different forms: purified 68Ga in basic solution, through solvent extraction and no purified 68Ga. The best result was achieved with DOTATATE labeling with purified 68Ga in basic media, proving the purification process efficiency.

Introduction: Targeted pharmaceuticals for labelling with radio-isotopes for very specific imaging (and possibly later for targeted therapy) play a major role in Theranostics which is currently an important topic in Nuclear Medicine as well as personalised medicine. There was a need for a very specific lung cancer radiopharmaceutical that would specifically be uptaken in integrin 3 expression cells to image patients using a Positron Emission Tomography- Computed Tomography (PET-CT) scanner. Background and problem statement: Cold kits of c (RGDyK)–SCN-Bz-NOTA were kindly donated by Seoul National University (SNU) to help meet Steve Biko Hospital’s need for this type of imaging. These cold kits showed great results internationally in labelling with a 0.1 M 68Ge/68Ga generator (t1/2 of 68Ge and 68Ga are 270.8 days and 67.6 min, respectively). However the same cold kits failed to show reproducible radiolabeling with the 0.6 M generator manufactured under cGMP conditions at iThemba LABS, Cape Town and distributed by IDB Holland, the Netherlands. Materials and methods: There was therefore a need for producing an in-house NOTA-RGD kit that would enable production of clinical 68Ga-NOTA-RGD in high yields from the IDB Holland/iThemba LABS generator. Quality control included ITLC in citric acid to observe labelling efficiency as well as in sodium carbonate to evaluate colloid formation. HPLC was also performed at iThemba LABS as well as Necsa (South African Nuclear Energy Corporation). RGD was obtained from Futurechem, Korea. Kit mass integrity was determined by testing labelling efficiency of 10, 30 and 60 μg of RGD per cold kit. The RGD was buffered with sodium acetate trihydrate. The original kits were dried in a desiccator and in later studies only freeze dried. Manual labelling was also tested. The radiolabelled in-house kit’s ex vivo biodistribution in healthy versus tumour mice were examined by obtaining xenografts. The normal biodistribution was investigated in three vervet monkeys by doing PET-CT scans on a Siemens Biograph TP 40 slice scanner. Results: Cold kit formulation radiolabeling and purification methods were established successfully and SOPs (standard operating procedures) created. HPLC results showed highest radiochemical purity in 60 μg cold kit vials. 68Ga-NOTA-RGD showed increased uptake in tumours of tumour bearing mouse. The cold kit also showed normal distribution according to literature with fast blood clearance and excretion through kidneys into urine, therefore making it a suitable radiopharmaceutical for clinical studies. Conclusion: The in-house prepared cold kit with a 4 month shelf-life was successfully tested in mice and monkeys. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Introduction: Targeted pharmaceuticals for labelling with radio-isotopes for very specific imaging (and possibly later for targeted therapy) play a major role in Theranostics which is currently an important topic in Nuclear Medicine as well as personalised medicine. There was a need for a very specific lung cancer radiopharmaceutical that would specifically be uptaken in integrin 3 expression cells to image patients using a Positron Emission Tomography- Computed Tomography (PET-CT) scanner. Background and problem statement: Cold kits of c (RGDyK)–SCN-Bz-NOTA were kindly donated by Seoul National University (SNU) to help meet Steve Biko Hospital’s need for this type of imaging. These cold kits showed great results internationally in labelling with a 0.1 M 68Ge/68Ga generator (t1/2 of 68Ge and 68Ga are 270.8 days and 67.6 min, respectively). However the same cold kits failed to show reproducible radiolabeling with the 0.6 M generator manufactured under cGMP conditions at iThemba LABS, Cape Town and distributed by IDB Holland, the Netherlands. Materials and methods: There was therefore a need for producing an in-house NOTA-RGD kit that would enable production of clinical 68Ga-NOTA-RGD in high yields from the IDB Holland/iThemba LABS generator. Quality control included ITLC in citric acid to observe labelling efficiency as well as in sodium carbonate to evaluate colloid formation. HPLC was also performed at iThemba LABS as well as Necsa (South African Nuclear Energy Corporation). RGD was obtained from Futurechem, Korea. Kit mass integrity was determined by testing labelling efficiency of 10, 30 and 60 μg of RGD per cold kit. The RGD was buffered with sodium acetate trihydrate. The original kits were dried in a desiccator and in later studies only freeze dried. Manual labelling was also tested. The radiolabelled in-house kit’s ex vivo biodistribution in healthy versus tumour mice were examined by obtaining xenografts. The normal biodistribution was investigated in three vervet monkeys by doing PET-CT scans on a Siemens Biograph TP 40 slice scanner. Results: Cold kit formulation radiolabeling and purification methods were established successfully and SOPs (standard operating procedures) created. HPLC results showed highest radiochemical purity in 60 μg cold kit vials. 68Ga-NOTA-RGD showed increased uptake in tumours of tumour bearing mouse. The cold kit also showed normal distribution according to literature with fast blood clearance and excretion through kidneys into urine, therefore making it a suitable radiopharmaceutical for clinical studies. Conclusion: The in-house prepared cold kit with a 4 month shelf-life was successfully tested in mice and monkeys. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

<p>The positron emitting radionuclide ⁶⁸Ga (T_1/2 = 68 min) might become of practical interest for clinical positron emission tomography (PET). The metallic cation, ⁶⁸Ga(III), is suitable for complexation with chelators, either naked or conjugated with biological macromolecules. Such labelling procedures require pure and concentrated preparations of ⁶⁸Ga(III), which cannot be sufficiently fulfilled by the presently available ⁶⁸Ge/⁶⁸Ga generator eluate. This thesis presents methods to increase the concentration and purity of ⁶⁸Ga obtained from a commercial ⁶⁸Ge/⁶⁸Ga generator. The use of the preconcentrated and purified ⁶⁸Ga eluate along with microwave heating allowed quantitative ⁶⁸Ga-labelling of peptide conjugates within 15 min. The specific radioactivity of the radiolabelled peptides was improved considerably compared to previously applied techniques using non-treated generator eluate and conventional heating. A commercial ⁶⁸Ge/⁶⁸Ga generator in combination with the method for preconcentration/purification and microwave heated labelling might result in an automated device for ⁶⁸Ga-based radiopharmaceutical kit production with quantitative incorporation of ⁶⁸Ga(III).</p><p>Macromolecules were labelled with ⁶⁸Ga(III) either directly or via a chelator. The bifunctional chelator, DOTA, was conjugated in solution to peptides, an antibody and oligonucleotides. The peptides had varied pI values, constitution, and length ranging from 8 to 53 amino acid residues. The oligonucleotides were of various sequences and length with modifications in backbone, sugar moiety and both 3' and 5' ends with a molecular weight up to 9.8 kDa. The bioconjugates were labeled with ⁶⁸Ga(III), and the resulting tracers were characterised chemically and biologically. The identity of the ⁶⁸Ga-labelled bioconjugates was verified. The tracers were found to be stable and their biological activity maintained. Specific radioactivity was shown to be an important parameter influencing the feasibility of accurate imaging data quantification.</p><p>Furthermore, ⁶⁸Ga-labelled peptide imaging was shown to be a useful tool to study peptide adsorption to microstructures in a chemical analysis device.</p>

The positron emitting radionuclide 68Ga (T1/2 = 68 min) might become of practical interest for clinical positron emission tomography (PET). The metallic cation, 68Ga(III), is suitable for complexation with chelators, either naked or conjugated with biological macromolecules. Such labelling procedures require pure and concentrated preparations of 68Ga(III), which cannot be sufficiently fulfilled by the presently available 68Ge/68Ga generator eluate. This thesis presents methods to increase the concentration and purity of 68Ga obtained from a commercial 68Ge/68Ga generator. The use of the preconcentrated and purified 68Ga eluate along with microwave heating allowed quantitative 68Ga-labelling of peptide conjugates within 15 min. The specific radioactivity of the radiolabelled peptides was improved considerably compared to previously applied techniques using non-treated generator eluate and conventional heating. A commercial 68Ge/68Ga generator in combination with the method for preconcentration/purification and microwave heated labelling might result in an automated device for 68Ga-based radiopharmaceutical kit production with quantitative incorporation of 68Ga(III). Macromolecules were labelled with 68Ga(III) either directly or via a chelator. The bifunctional chelator, DOTA, was conjugated in solution to peptides, an antibody and oligonucleotides. The peptides had varied pI values, constitution, and length ranging from 8 to 53 amino acid residues. The oligonucleotides were of various sequences and length with modifications in backbone, sugar moiety and both 3' and 5' ends with a molecular weight up to 9.8 kDa. The bioconjugates were labeled with 68Ga(III), and the resulting tracers were characterised chemically and biologically. The identity of the 68Ga-labelled bioconjugates was verified. The tracers were found to be stable and their biological activity maintained. Specific radioactivity was shown to be an important parameter influencing the feasibility of accurate imaging data quantification. Furthermore, 68Ga-labelled peptide imaging was shown to be a useful tool to study peptide adsorption to microstructures in a chemical analysis device.