Objective    To investigate the acute toxicity in mice of an antisense oligodeoxynucleotide (ASODN) probes of oncogene c-erbB2 labeled by superparamagnetic iron oxide (SPIO) nanoparticle in order to make it be a target contrast agent for magnetic resonance (MR) imaging and targeting gene therapy.     Methods    Totally 60 health clean-grade Kunming mice were randomly and equally divided into oral administration

intravenous injection and intraperitoneal injection groups. All mice received the maximum dose although through different routes. The oral administration was given with a total dose of 2 104.8 mg/kg and a volume of 40 ml/kg

intravenous with a total dose of 438.5 mg/kg and a volume of 25 ml/kg

and intraperitoneal injection with a total dose of 1 578.6 mg/kg and a volume of 30 ml/kg respectively. Another 60 mice who received same dose of normal saline through same route served as the control group. All experimental mice were feed in 25 ℃ for 14 d. Their general condition

blood routine examination

coagulation indexes

main biochemical indexes and the pathological morphology of main viscera were tested and measured.     Results    During the observation period

there was no death in all mice

and only a few had appetite loss and increased water drinking

diarrhea

sleepiness

and more active

but all abnormalities disappeared in 3 d. There was no abnormality in gross observation and morphology of the liver

spleen

kidneys

heart

lungs

bone marrow and genitals. All cells of the liver

spleen

kidneys

heart

lungs

bone marrow and genitals had no edema

degeneration and necrosis either in HE or in Wright staining. There was no significant difference in the blood routine examination

coagulation indexes and biochemical indexes in experimental groups and control group.     Conclusion    SPIO labeled c-erbB2 ASODN probe has no acute toxicity to mice

and belongs to nontoxic compound.