Objective:

To construct a positron emission tomography (PET) probe

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Ga-NOTA-376

targeting CLDN18

.2 using a non-site-specific labeling method

and to evaluate its in vitro and in vivo properties.

Methods:

The chelating agent p-SCN-Bn-NOTA was used to non-site-specifically conjugate the nanobody 376 targeting CLDN18.2

resulting in the precursor NOTA-376

which was then radiolabeled with

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Ga. The labeling efficiency

radiochemical purity

and in vitro stability of the probe were determined by radio- thin layer chromatography (Radio-TLC)

and micro-PET/ computed tomography (CT) imaging experiments were conducted in a nude mouse model of human gastric adenocarcinoma.

Results:

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Ga-NOTA-376 demonstrated a high labeling yield (89.98±0.07) %

high radiochemical purity (97.67±0.02)% and high specific activity (16.69±6.60) GBq/μmol

and remained stable in 5% human serum albumin (HSA) and phosphate-buffered saline (PBS). Micro-PET/CT results indicated that the maximum standardized uptake value (SUV

max

) of the probe in CLDN18.2-positive tumors was significantly higher than in CLDN18.2-negative tumors. At 4.0 h

the SUV

max

of CLDN18.2- positive tumors and CLDN18.2-negative tumors were 9.08±0.33 and 1.92±0.32

respectively.

Conclusion:

This study successfully constructed a CLDN18.2-targeting probe

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Ga-NOTA-376 using a non-site-specific labeling method

which showed high labeling efficiency

good stability

and targeting capability

making it a potential PET probe for the detection of CLDN18.2 protein expression levels.