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).

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.