Size Control of (99m)Tc-tin Colloid Using PVP and Buffer Solution for Sentinel Lymph Node Detection

Area of Science:

• Radiochemistry
• Nanotechnology
• Nuclear Medicine

Background:

• Colloidal particle size is crucial for sentinel lymph node mapping in lymphoscintigraphy.
• Developing methods for synthesizing controlled nano-sized radiocolloids is essential for improved diagnostic imaging.

Purpose of the Study:

• To develop facile methods for preparing technetium-99m-tin colloid with nanometer-scale particle sizes.
• To evaluate the suitability of different stabilizers and buffers for controlling colloid size.
• To assess the in vitro and in vivo behavior of the synthesized radiocolloids for sentinel node detection.

Main Methods:

• Synthesis of technetium-99m-tin colloid using tin fluoride, sodium fluoride, poloxamer-188, and polyvinylpyrrolidone (PVP).
• Adjustment of pH using phosphate or sodium bicarbonate buffers.
• Characterization of colloid particle size and evaluation of in vitro and in vivo distribution and uptake in animal models.

Main Results:

• Polyvinylpyrrolidone (PVP) effectively controlled colloid size within the nanometer range.
• Technetium-99m-tin colloid stabilized with sodium bicarbonate and PVP (99mTc-BPTC-50, <20 nm) showed preferential bone marrow and kidney distribution.
• Technetium-99m-tin colloid stabilized with phosphate buffer and PVP (99mTc-PPTC-30, >100 nm) primarily accumulated in the liver.
• In rabbits, 99mTc-BPTC-50 demonstrated increasing sentinel lymph node uptake over time, unlike 99mTc-PPTC-30.

Conclusions:

• Nano-sized tin colloids can be rapidly and easily synthesized using PVP.
• The 99mTc-BPTC-50 formulation shows significant potential as a radiopharmaceutical for sentinel lymph node detection due to its favorable biodistribution and node uptake characteristics.