¹²³I-Radiolabeling Service

The ¹²³I-radiolabeling service includes the custom synthesis of SPECT tracers of unique quality, which is due to the optimal 13.2-hour half-life and clean gamma emission from the isotope, which allows for enhanced in vivo imaging of peptides, antibodies, and other biologics. State-of-the-art facilities and mastery of intricate radiohalogenation techniques enable Alfa Cytology to offer high-purity custom conjugated ¹²³I radiopharmaceuticals development for high-level preclinical research.

Introduction to ¹²³I Isotopes

Iodine-123 (¹²³I) is considered a cyclotron-produced radioisotope valuable for high-resolution single-photon emission computed tomography (SPECT) imaging. For diagnostic imaging, iodine-123 is considered ideal because of its half-life of 13.2 hours, which corresponds to the pharmacokinetics of various peptides and other biologics that require later imaging times. It emits 159 keV gamma rays, which are considered perfectly suited for SPECT cameras, allowing for superb image clarity and resolution. Due to these properties, iodine-123 is preferred for the development of novel diagnostic agents in neurology and cardiology.

¹²³I-Labeling for SPECT Imaging

Iodine-123 (¹²³I) is a radionuclide fundamental for SPECT imaging. It has a 13.2-hour half-life, which matches well the pharmacokinetics of peptides and proteins. Imaging is performed with a 159 keV gamma emission, which yields good resolution. In addition, the well-established radiohalogen chemistry enables ¹²³I stable and covalent incorporation into various molecules, broadening the potential for developing new radiopharmaceuticals for preclinical research.

Fig.1. [¹²³I]CC1 was synthesized from precursor 9 via a copper-mediated iododeboronation reaction. (Chung Ying Chan, et al., 2023)

¹²³I Radiopharmaceutical

Disclaimer: Alfa Cytology focuses on providing preclinical research services. This table is for information exchange purposes only. This table is not a treatment plan recommendation. For guidance on treatment options, please visit a regular hospital.

Advantages of ¹²³I -Labeling

• SPECT-Optimized Photon Energy: The principal 159 keV γ emission aligns with standard LEHR collimation, supporting high spatial resolution with low septal penetration and scatter.
• Chelator-Free, Size-Conserving Chemistry: Direct aromatic radioiodination or use of small prosthetic groups preserves molecular size and binding geometry relative to metal-chelator systems.
• High Specific (Molar) Activity: Cyclotron production allows trace-level labeling for low-abundance targets while minimizing receptor saturation.
• Cleaner Imaging vs ¹³¹I: Absence of high-energy γ lines and β radiation improves image contrast and quantitative accuracy in SPECT/CT.
• Element-Matched Theranostic Pairing with ¹³¹I: Identical iodine chemistry facilitates diagnostic-to-therapeutic translation and patient-specific (or animal-specific) dosimetry using the same vector.
• Robust Late-Stage Functionalization: Methods such as iododestannylation/iododeboronation and SIB-type prosthetics enable site-selective labeling under mild, protein-compatible conditions.

Our Services

Alfa Cytology offers expertise in radiohalogenation chemistry, which allows for stable and successful conjugation of Iodine-123 to numerous small molecules, peptides, and proteins. With our capabilities, we can provide you with stable, high-purity, and high-specific-activity ¹²³I-labeled compounds guaranteed with precision and accuracy for your preclinical imaging studies, guaranteed to deliver data that is reliable and reproducible.

Custom ¹²³I Conjugation Service

¹²³I conjugation service provides an all-inclusive solution that focuses specifically on transforming a novel compound into a high-performance SPECT imaging agent. We begin with detailed fundamental research, to the synthesis and purification alongside quality assurance, to deliver a radiotracer development service that satisfies the client's research requirements.

Small-Molecule Radionuclide Conjugate (SMRC)

Antibody-Radionuclide Conjugate (ARC)

Peptide-Radionuclide Conjugate (PRC)

siRNA-Radionuclide Conjugate

Radiolabeling Small Molecule with ¹²³I for SPECT Imaging

¹²³I Custom Radiosynthesis

Iodine-123-labeled small molecules begin with a collaborative consultation to outline goals and define the molecular structure. Following this, our specialists design and execute a custom radiolabeling strategy, determining the optimal approach for effective, selective, and targeted radionuclide incorporation.

• Strategy Selection: Given the structure of your target molecule and the specific site of labeling (e.g., on an aromatic ring), we choose and refine the most suitable iodination technique.
• Precursor Design & Synthesis: According to the defined approach, we synthesize or acquire a high-purity precursor molecule that is designed for efficient radioiodination.
• Protocol Optimization: For each specific compound, the reaction parameters such as the solvent, temperature, duration, and the oxidizing agent are customized to enhance the radiochemical yield.
• Custom Radiosynthesis: The reactions are monitored using rapid analytical techniques like micro-TLC and radio-HPLC to assess the optimal quenching time to achieve the highest yield and purity, under the shielded micro-reactors.

Purification & Quality Control

After labeling, the compound undergoes stringent purification and a battery of quality control (QC) tests to verify for successful incorporation of ¹²³I. Analytical methods, such as liquid chromatography (LC), mass spectrometry (MS), and scintillation counting, are used to confirm the correct isotopic labeling, purity, and stability of the compound, ensuring that it meets the necessary standards for biological studies.

In Vitro Evaluation

In vitro tests are performed to evaluate the biological properties of the ¹²³I-labeled radiopharmaceutical. This includes studying its interaction with target receptors, cellular uptake, metabolic stability, and other pharmacological properties.

In Vivo Evaluation

This vital step starts with quantitative biodistribution and pharmacokinetic (PK) studies to systematically assess the agent's distribution throughout the different parts of the body and the excretion rate. Thereafter, SPECT imaging is done in relevant disease models to assess the specific target engagement of the agent and in vivo blocking studies to conclusively assess the agent's potency for diagnosis.

Applications of ¹²³I-Radiolabeling

Due to its physical properties pertaining to SPECT, having a half-life of 13.2 hours and gamma emission of 159 keV, radiolabeling with ¹²³I has wide applications in the development of high precision imaging agents. Most are concerned with in vivo biodistribution and target engagement visualization of molecules with intermediate pharmacokinetics, including peptides, antibodies, and small-molecule ligands across a range of preclinical research.

Alfa Cytology has the capabilities to offer a complete ¹²³I-labeling service as a result of in-depth radiochemistry knowledge, and offers services from project strategic design and synthesis, even to the stages of product delivery and completion. We invite you to contact us with your project requirements to offer a fully-tailored solution to suit the specific objectives of the project.

Reference

1. Chung Ying Chan, et al. (2023). [¹²³I]CC1: A PARP-Targeting, Auger Electron–Emitting Radiopharmaceutical for Radionuclide Therapy of Cancer. Journal of Nuclear Medicine. jnumed.123.265429.

For research use only. Not intended for any clinical use.