Sungtaek Huh April 3 rd, 2012 The University of Western Ontario Department of Medical Biophysics

Cryopreservation and the Bone Freezing cells and tissue at very low temperatures Bone consists of a matrix of collagen and various ions which form the osseous tissue Results may be important in the medical field for transplants

Objectives Determine the mechanical properties of bone before and after cryopreservation Determine correlation between cryopreservation and non-cryopreservation

Hypothesis Frozen bone will be less elastic than before Water expands as it freezes Significant difference in mechanical properties between frozen group and control group

Methods 14 Food-grade chicken tibia used Prepared in moulds using plaster Bones loaded using 4-point stress method Images are taken of each load, then the angle is measured with ImageJ Strain values are calculated from the angles Bones are broken at the end using 3-point stress to determine the ultimate tensile strength

Methods - continued

All chicken tibia stressed and measured Frozen for 1 week, then measured Broken bones measured Stored in a refrigerator for 1 week, then measured Bones broken using 3-point bending stress Methods - continued

Results First Load Second Load Has an average Young’s modulus of 27.7MPa Frozen group has an average Young’s modulus of 66.7MPa Cold group has an average Young’s modulus of 0.8MPa Using paired t-tests for the available group, Young’s modulus values between the second load (frozen) and first load significantly different (P<0.05)! No significant difference found in the ultimate tensile strength between frozen and non-frozen bones

Discussion Cellular components required for elasticity may have been destroyed in the freezing process Cryoprotectants such as DMSO not used Week-long ‘sitting period’ for the control group may have affected the mechanical properties

Conclusion Significant differences in Young’s modulus for the frozen bones found (Between 1 st and 2 nd load) No significant difference found for the ultimate tensile strength between frozen bones and ‘cold’ bones

Acknowledgments Thank you to: Dr. Ian MacDonald, Department of Medical Biophysics

Images 1. Bone histology: _structure/su/m2/s3/index.htm _structure/su/m2/s3/index.htm 2. Water bottle: Glass_bottle_shattered_by_frozen_water- SPL.jpg Glass_bottle_shattered_by_frozen_water- SPL.jpg 3. Cell bursting: g g