Change in creep behavior of plexiform bone with phosphate ion treatment

Article type: Research Article

Authors: Regimbal, R.L.^{; ;} | DePaula, C. Alex^{; ;} | Guzelsu, N.^{; ;}

Affiliations: The University of Medicine and Dentistry of New Jersey‐SOM, Biomechanics Laboratory, Tr.#4, 675 Hoes Lane, Piscataway, NJ 08854, USA | Rutgers University, Department of Biomedical Engineering, 617 Bowser Road, Piscataway, NJ 08854, USA | Currently: Assistant Director, Regulatory Compliance, SmithKline Beecham, 1500 Littleton Road, Parsippany, NJ 07054, USA | Currently: MTF, Product Development Scientist, Edison Corporate Center, 125 May Street, Suite 300, Edison, NJ 08837, USA

Note: [] Corresponding author: N. Guzelsu, Ph.D., Associate Professor of Biomechanics, UMDNJ‐SOM, Department of Osteosciences/Biomechanics, PCC, Suite 102, 40 East Laurel Road, Straford, NJ 08084‐1504, USA. Tel.: 856 566 2731; Fax: 856 566 2733; E‐mail: [email protected].

Abstract: The effect of phosphate ions on the mechanical properties of plexiform bone in tension was investigated with an in‐vitro model. Bone samples were treated with saline and phosphate ion solutions for three days at 25°C and 37°C and tested in tension. The mechanical properties of the bone samples treated with phosphate were not different than controls (saline treated). Electro kinetic measurements on plexiform bone particles treated with phosphate ions at 37°C showed that phosphate ions alter electro kinetic potentials of bone particles by interacting with bone mineral as compare to saline treated particles near physiological pH. Because of the limited diffusion properties of intact plexiform bone tissue, the tension experiments indicate that, the effect of phosphate ions on the bone mineral–matrix interface is negligible after three days treatment. On the other hand, electro kinetic measurements demonstrated that in a short period of treatment time, phosphate ions diffuse through organic matrix barrier and interact with bone mineral when plexiform bone is in the particle form. As a final experiments bone samples were tested at 37°C in three point bending configuration for three days in saline and phosphate buffer solution. The maximum tension stress generated in bending samples was about 75 percent of the tension yield stress of the samples. The creep experiments showed that the bending rigidity of bone samples tested in phosphate solution reduced in time hence the creep deformation increased compare to control samples tested in saline. This observation is attributed to the acceleration of phosphate ion diffusion into the bending samples due to micro cracks accumulation in bone tissue during the creep experiments which facilitated the phosphate ion interaction with bone mineral.

Keywords: Bone, mechanical properties, phosphate ions, electrokinetic, viscoelastic behavior, bonding at the mineral–organic interface

Journal: Bio-Medical Materials and Engineering, vol. 13, no. 1, pp. 11-25, 2003