DOTA/NOTA functionalization – metal chelator peptide labeling
Bi-Functional Chelating agents (BCA)
Modern imaging techniques use radioactive isotopes of metal ions, often in combination with targeting peptides.
Positron emission tomography (PET) is a nuclear medicine imaging technique commonly used for measuring changes in physiological activities.
By example, for positron emission tomography, DOTA metal chelator is combinate with a radionucleide, a metal radioactive isotope, for some applications such as contrast agents and cancer treatments.
Magnetic resonnance imaging and Single-photon emission computed tomography (SPECT) are other applications for DOTA bi-functional chelating agent (BCA).
Cyclic chelating compounds have been developed that have both nitrogens and carboxylates and are able to tightly coordinate metal ions useful for in vivo imaging diagnostics and drug discoverty. The most commonly BCAs are DOTA, NOTA and TETA.
sb-PEPTIDE offers to synthesize your peptide with DOTA labeling for your experiments. The modification is usually made in N-terminal or C-terminal on a Lysine residue.
As a polydentate ligand, DOTA is used for metal complexation, especially metal cations such as lanthanide ions LN3+ (e.g. Lanthanum or Lutetium)
DOTA contains four acetic acid carboxylate groups and four nitrogens in it 12-atom cyclic structure. C- or N-functionalized derivatives of this basic structure produce a bi-functionnal chelating agent (BCA) capable of modifying proteins and binding radioactive metal ions in strong coordination complexes of up to eight dative bonds.
DOTA is used in cancer therapy and diagnosis.
Peptides are frequently used with DOTA. For example, DOTATOC (DOTA-(Tyr3)-octreotide or edotreotide), or DOTA-TATE (DOTA-(Tyr3)-octreotate), are a form of peptide receptor radionuclide therapy (PRRT) which targets somatostatin receptors (SSR).
SSRs are found with high density in numerous malignancies, including CNS, breast, lung, and lymphatics. Their role in neuroendocrine tumours is now well established.
Also, DOTA-Biotin, which have an affinity for the proteins streptavidin and avidin,
Finally, the complex of Gd3+ and DOTA is used as a gadolinium-based MRI contrast agent under the name gadoteric acid.
If you are interested in DOTA, NOTA or TETA peptide labeling, please contact us.
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Lanthaninde ions (LN3+)
Also, Yttrium-90 is a transition metal historically classified as a lanthanide. It is frequently complexed with DOTA in some cancer therapies. By example, Yttrium (90Y) clivatuzumab tetraxetan, or also Yttrium (90Y) tacatuzumab tetraxetan.
1- Guleria M, Das T, Amirdhanayagam J, Sarma HD, Dash A. Cancer Biother Radiopharm. (2018)
Comparative Evaluation of Using NOTA and DOTA Derivatives as Bifunctional Chelating Agents in the Preparation of 68Ga-Labeled Porphyrin: Impact on Pharmacokinetics and Tumor Uptake in a Mouse Model
PURPOSE: Both NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid) and DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) derivatives have been used as bifunctional chelating agents (BFCAs) for the preparation of 68Ga-labeled target-specific agents having potential for positron emission tomography (PET) imaging of cancerous lesions. In the present work, the authors have attempted a comparative pharmacokinetic evaluation between 68Ga-labeled porphyrins prepared using NOTA and DOTA derivatives as the BFCAs.
PROCEDURES: A symmetrical porphyrin derivative, 5,10,15,20-tetrakis(p-carboxymethyleneoxyphenyl)porphyrin, was synthesized and coupled with two different BFCAs viz. p-NH2-benzyl-NOTA and p-NH2-benzyl-DOTA. Both the porphyrin-BFCA conjugates were radiolabeled with 68Ga. A comparative bioevaluation involving pharmacokinetics and tumor affinity was performed in a tumor-bearing small animal model.
RESULTS: Gallium-68-labeled porphyrin-amido-benzyl-NOTA and porphyrin-amido-benzyl-DOTA complexes were prepared with high radiochemical purity. Both radiolabeled complexes exhibited almost similar stability in human serum and near-identical tumor affinity and pharmacokinetic behavior in animal studies.
CONCLUSION: The present study demonstrates that the pharmacokinetic behavior of 68Ga-labeled porphyrin derivatives, prepared using either NOTA or DOTA derivatives as BFCAs, remains almost identical and hence both NOTA and DOTA derivatives could be considered equivalent for developing 68Ga-based PET agents for imaging of tumorous lesions.
2 - Notni J, Pohle K, Wester HJ. EJNMMI Res. (2012)
Comparative gallium-68 labeling of TRAP-, NOTA-, and DOTA-peptides: practical consequences for the future of gallium-68-PET
Currently, 68Ga-labeled 1,4,7,10-tetraazacyclododecane-tetraacetic acid (DOTA)-peptides are the most widely used class of 68Ga radiotracers for PET, although DOTA is not optimal for 68Ga complexation. More recently, 1,4,7-triazacyclononane-triacetic acid (NOTA) and particularly triazacyclononane-phosphinate (TRAP) chelators have been shown to possess superior 68Ga binding ability. Here, we report on the efficiency, reproducibility, and achievable specific activity for fully automated 68Ga labeling of DOTA-, NOTA-, and TRAP-peptide conjugates.
Compared to NOTA- and DOTA-peptides, achievable specific activity (AS) for TRAP-peptide is approximately 10 and 20 times higher, respectively. AS values in the range of 5,000 GBq/μmol were routinely obtained using 1 GBq of 68Ga, equivalent to 0.11 μg of cold mass for a 185-MBq patient dose of a 3-kDa conjugate. The TRAP-peptide could be 68Ga-labeled with excellent reproducibility and > 95% radiochemical yield for precursor amounts as low as 1 nmol.
High 68Ga labeling efficiency of TRAP-peptides could facilitate realization of kit labeling procedures. The good reproducibility of the automated synthesis is of relevance for GMP production, and the possibility to provide very high specific activities offers a high degree of safety in first clinical trials, due to reduction of cold mass content in tracer formulations.