Investigation into various aspects of radiolabelling somatostatin peptide derivatives with 68Ga eluted from a SnO2-based 68Ge/68Ga generator
| dc.contributor.advisor | Rubow, Sietske Margarete | en_ZA |
| dc.contributor.advisor | Rossouw, Daniel Dutoit | en_ZA |
| dc.contributor.author | Prince, Deidre Mabel | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Nuclear Medicine. | en_ZA |
| dc.date.accessioned | 2018-02-19T13:27:55Z | |
| dc.date.accessioned | 2018-04-09T06:55:01Z | |
| dc.date.available | 2018-02-19T13:27:55Z | |
| dc.date.available | 2018-04-09T06:55:01Z | |
| dc.date.issued | 2018-03 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2018. | en_ZA |
| dc.description.abstract | ENGLISH SUMMARY : 68Ge/68Ga generators ensure the supply of 68Ga for positron emission tomography (PET), for instance for somatostatin receptor imaging with 68Ga-DOTA-labelled somatostatin analogues. There are various generators available and their eluates are processed differently for radiolabelling of peptides. The objectives of this study were to investigate various aspects of the elution characteristics of the generator, to optimize labelling conditions using different eluate processing techniques such as fractionation and cation exchange chromatography and to develop user-friendly kit formulations. This study was approved by the Stellenbosch University Health Research Ethics Committee and permission was granted for the experimental work to be conducted at iThemba LABS. Elution efficiencies were determined using different HCl concentrations (0.2 M – 1.0 M). Metal analysis and 68Ge breakthrough determination were performed on eluates. Radiolabelling parameters were optimized, using fractionated eluates and different DOTA-peptide masses (15 to 50 μg) at pH 3.5 – 4.0 in sodium acetate buffer. Different heating times and heating methods and the influence of various periods of non-elution of the generator on radiolabelling results were investigated. Cationic resins were investigated for eluate processing. Radiolabelling parameters, using cationic resin-processed eluates, were optimized. Labelling was conducted at various pH values, using different quantities of buffer. DOTA-peptide kits for both fractionated and resin-processed eluates were developed and tested for sterility, endotoxin content and stability. Radiochemical yields, radiolabelling efficiency and radiochemical purity of 68Ga-DOTA-peptides were determined. The elution efficiency of the generator increased with an increase in the concentration of HCl eluent. The 68Ge breakthrough increased dramatically at 0.8 M HCl. Most metal contaminants were lowest when eluting with 0.2 M HCl and the Zn content increased with the increase in HCl concentration. The eluent of choice for the SnO2-based generator was confirmed to be 0.6 M HCl. For radiolabelling, 35 μg DOTA-peptide (9.2 – 9.4 μM) was the most favourable. Extended heating times and heating method did not significantly impact on the radiolabelling. The radiolabelling efficiencies were consistently above 90 % even after 3 weeks of non-elution of the generator, but radiochemical yields dropped after 7 days. DOTA-peptide kits for fractionated eluates were successfully developed and the radiolabelling quality was found to be superior over peptide stock solutions. A radiolabelling method using a cationic exchange resin was successfully adapted for the SnO2 generator. 68Ga was efficiently adsorbed on a Bond Elut SCX (100 mg) cartridge and desorbed by acidified solutions of NaCl. The SCX resin effectively removed about 98 % of deliberately “spiked” metals from the 68Ga eluate. An optimized labelling method based on the use of SCX-purified eluates was developed, producing radiochemical yields of almost 85 % and lead to the successful formulation of DOTATATE kits. The quality was found to be suitable over a 3-month period. In conclusion, a kit type labelling procedure, using cationic resin purified 68Ga eluates, provides the most practical method to produce 68Ga-labelled DOTA-peptides. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING : 68Ge/68Ga generators verseker beskikbaarheid van 68Ga vir positron emissie tomografie (PET), bv. vir somatostatien reseptor beelding met 68Ga-DOTA-gemerkte somatostatien analoë. Verskillende tipes generators is beskikbaar waarvan die eluate op verskillende maniere vir die radiomerking van peptiede geprossesseer word. Die doelstellings van hierdie studie was om verskeie aspekte van die elueringskarakteristieke van die generator te ondersoek, om radioaktiewe merkingsparameters deur middel van verskillende eluaatverwerkingstegnieke soos fraksionering en katioonuitruil chromatografie te optimaliseer en om gebruikersvriendelike kitsstelformulerings te ontwikkel. Goedkeuring vir hierdie studie is deur die Komitee vir Navorsing en Etiek van die Universiteit van Stellenbosch toegestaan en toestemming is ook deur iThemba LABS verleen vir die uitvoer van alle eksperimentele werk by hierdie fasiliteit. Elueerdoeltreffendheid met verskillende HCl konsentrasies (0.2 M – 1.0 M) is bepaal. Metaalanalises en bepalings van 68Ge deurbraak is op eluate uitgevoer. Radiomerkingsparameters is geoptimaliseer met gefraksioneerde eluate en verskillende peptiedmassas (15 tot 50 μg) by pH 3.5 – 4.0 in ‘n natriumasetaat buffer. Verkillende verhittingstye en -metodes is ondersoek. Die invloed van verskeie tye van nie-eluering van die generator op radiomerking, is ondersoek. Katioonuitruilharse is ondersoek vir suiwering van eluate. Merking is by verskillende pH vlakke en met verskillende hoeveelhede buffer uitgevoer. DOTA-peptiedkitsstelle is vir beide gefraksioneerde en hars-gesuiwerde eluate ontwikkel en is vir steriliteit, endotoksieninhoud en stabiliteit getoets. Radiochemiese opbrengs, radiomerkingsdoeltreffendheid en radiochemiese suiwerheid van 68Ga-DOTA-peptiede is bepaal. Die elueringsdoeltreffendheid van die generator het stelselmatig toegeneem met ‘n toename in die konsentrasie van HCl elueermiddel. 68Ge deurbraak het aansienlik toegeneem by 0.8 M HCl. Die meeste metaalonsuiwerhede was die laagste wanneer met 0.2 M HCl ge-elueer is en die Zn inhoud het konsekwent toegeneem met toename in HCl konsentrasie. ‘n HCl konsentrasie van 0.6 M HCl is bevestig as die voorkeur elueermiddel vir die SnO2-gebaseerde generator. Vyf-en-dertig μg DOTA-peptied (9.2 – 9.4 μM) is as optimaal vir die radiomerkingsproses gevind. Nòg verlengde verhittingstye, nòg die tipe verhittingsmetode het enige noemenswaardige invloed op radiomerkingsresultate gehad. Die radiomerkingsdoeltreffendheid was konsekwent hoër as 90 %, selfs na 3 weke van nie-eluering van die 68Ge/68Ga generator, maar radiochemiese opbrengste het begin afneem na 7 dae. DOTA-peptied kitsstelformulerings vir gebruik met gefraksioneerde eluate is suksesvol ontwikkel en die radiomerkingsgehalte was beter as dié van peptied voorraadoplossings. ‘n Radiomerkingsmetode waarin eluate deur middel van ‘n katioonuitruilhars geprossesseer is, is suksesvol aangepas vir die SnO2 generator, wat met hoër konsentrasies HCl ge-elueer word. Die 68Ga is doeltreffend op ‘n Bond Elut SCX (100 mg) kolom ge-adsorbeer en daarna -elueer met aangesuurde NaCl oplossing herwin. Die SCX hars het ongeveer 98 % van metale wat doelbewus by eluate gevoeg is, doeltreffend verwyder. ‘n Ge-optimaliseerde merkingsmetode, gebaseer op die gebruik van SCXgesuiwerde eluate, is ontwikkel wat radiochemiese opbrengste van nagenoeg 85 % tot gevolg gehad het en tot die suksesvolle formulering van gebruikersvriendelike DOTATATE kitsstelle gelei het. Die kwaliteit is gedurende ‘n 3 maande stoorperiode deurlopend geskik bevind. Hierdie studie het getoon dat ‘n kitsstel vir merking met katioon-hars gesuiwerde 68Ga eluate die mees praktiese metode vir bereiding van 68Ga-gemerkte DOTA-peptiede is. | af_ZA |
| dc.format.extent | xiv, 115 pages ; illustrations, includes annexures | |
| dc.identifier.uri | http://hdl.handle.net/10019.1/103398 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | |
| dc.rights.holder | Stellenbosch University | |
| dc.subject | Tomography, Emission | en_ZA |
| dc.subject | (68)Ga-labelled DOTA-peptides | en_ZA |
| dc.subject | Radiolabeling | en_ZA |
| dc.subject | Gallium -- Isotopes | en_ZA |
| dc.subject | UCTD | |
| dc.title | Investigation into various aspects of radiolabelling somatostatin peptide derivatives with 68Ga eluted from a SnO2-based 68Ge/68Ga generator | en_ZA |
| dc.type | Thesis | en_ZA |