Dosimetry of Beryllium in an Animal Model Dosimetry of Beryllium in an Animal Model by Accelerator Mass Spectrometry (AMS)by Accelerator Mass Spectrometry (AMS)

Marina Chiarappa-Zucca

R.C. Finkel

J.E. McAninch

R.E. Martinelli

K.W. Turteltaub

Lawrence Livermore National Laboratory University of California

Our aim is to develop a method to quantify attomole Our aim is to develop a method to quantify attomole (10(10-18-18) amounts of Be in biological samples) amounts of Be in biological samples

• This method should enable the identification of molecular targets of Be at very low doses and provide detailed characterization of Be dosimetry

• Demonstration of this capability will facilitate research collaborations on the cellular and molecular mechanisms of CBD

OutlineOutline

• Introduction– What is accelerator mass spectrometry (AMS)?

• Experimental Approach– Sample preparation steps for extracting Be for AMS – AMS measurement of Be standards– Data from experiments showing Be distribution in

mouse tissues

• Conclusions

What is AMS?What is AMS?

AMS counts nuclei directly rather then measuring radioactive decay

This results in 3-9 orders of magnitude more sensitivity relative to scintillation counting

Allows analysis of attomole quantities in small samples (µg-mg) with low activity levels (nCi-fCi)

LLNL has 15 years of experience with AMS and has pioneered the bioscience applications

AMS provides high sensitivity measurements AMS provides high sensitivity measurements of long-lived (10 < tof long-lived (10 < t1/2 1/2 > 10> 107 7 yrs) radioisotopesyrs) radioisotopes

Current AMS Capability

Developing Capability

Long-lived isotopes with possible applications using AMS10 yrs < t1/2 < 107 yrs

Difficult to produceFission fragments

Ce Tb Dy Ho Er Tm Yb LuLa Pr Nd Pm Sm Eu Gd

Ac Th UPa Np Pu Am Cm Bk Cf Es Fm Md No Lr

Pd

NaMg Al

Ga

In

Tl

B

As

Sb

Bi

N

P

Se

Te

O

S

Po

C

Ge

Pb

Sn

Si

He

Ne

Ar

Kr

Xe

Rn

Cl

Br

F

At

I

NiSc V Cr Co Cu Zn

Y Ru Rh Ag Cd

Ta W Os Ir Au

Ti MnFe

Zr Nb Tc

Hf Re Pt Hg

Mo

Ca

Be

H

Li

K

Rb

Fr

Ba

Ra

Cs

Sr

Accelerators at Lawrence Livermore National Accelerators at Lawrence Livermore National LaboratoryLaboratory

64 samples (plus standards and blanks) measured as a set

>100 unknowns can be quantified in 24 hr of accelerator time

14C BioAMS

Tandem; multiple isotopes including 10Be

10Be has significant advantages compared to other Be isotopes

Routine sensitivity is ~0.02 fg

Experiments require fCi total activities

10Be has a long half life (1.6 My) and therefore can be measured in samples from months to years

10Be in low dose experiments can typically be handled as non-radioactive and non-hazardous

AMS can be used to measure AMS can be used to measure 1010BeBe

Sample Preparation StepsSample Preparation Steps

There are multiple steps for extracting Be from There are multiple steps for extracting Be from samples for AMS measurementsamples for AMS measurement

AMS Ion SourcePacking intoAMS target

Oxidizing to BeO

DisposableQuartz Crucibles

PrecipitationAcid digestion

AMS Measurements of Standards AMS Measurements of Standards

Each data point represents the mean ± SD of three independently prepared standards

Instrument precision is 1-3%

AMS measurement of standards is linear in AMS measurement of standards is linear in the range of interest with good precision the range of interest with good precision

1.0E+05

1.0E+07

1.0E+09

1.00E+05 1.00E+07 1.00E+09

Expected 10Be atoms

Method Detection Limit

109

107

105

Mea

sure

d 10

Be

ato

ms

107 109

Proof-of-Concept ExperimentProof-of-Concept Experiment

30 g male ICR mice

Intraperitoneal injection of 0.05, 0.5, and 5.0 µg Be (~2-200 µg/kg body weight)

Three mice used for each dose

24 hr exposure

Liver, spleen, kidneys, lung, blood, and femurs prepared for AMS analysis

Proof of concept experiments show Be Proof of concept experiments show Be distribution in mouse tissuesdistribution in mouse tissues

Be measured in tissues is dose-dependent Be measured in tissues is dose-dependent within dose range studiedwithin dose range studied

1.0E-03

1.0E-01

1.0E+01

1.0E+03

1.0E+05

1.E-04 1.E-02 1.E+00

FemurSpleenLiver BloodLungKidney

105

10-3

10

0.001 0.1 10

Be

(ng

/g w

et t

issu

e)

Total Dose (µg Be)

method detection limit

* **

Spleen and blood data extrapolated to determine dose limits with current MDL

~ 200 pg (.007 µg/kg bw) * ~ 0.01 µg (0.3 µg/kg bw) **

These doses are below environmental Be exposures (e.g. for humans 0.9 0.5 µg/kg bw)

ConclusionsConclusions

• AMS provides high sensitivity 10Be measurements in biological samples

• Our future direction is to study mechanisms of Be disease– Explore molecular dosimetry– Identify molecular (e.g. protein) targets that are

responsible or involved in CBD– Evaluate the correlation between these endpoints

and susceptibility to CBD

• We are ready now to collaborate with other researchers that have specific applications for this capability

FundingFunding

Office of Biological and Environmental ResearchU.S. Department of Energy