IIT Guwahati’s bone graft aids extensive bone formation

Prelims level : Health / Biotech Mains level : GS - IIIScience and Technology- developments and their applications and effects in everyday life.
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  • A scaffold made of silk–bone cement composite doped with silicon and zinc metal ions has been found to regenerate new bone tissue in rabbits in three months.
  • The newly formed bone forms a seamless joint with the existing bone and has blood vessels inside it.
  • Tests carried out on rabbits with defective thigh bone (femur) showed extensive bone formation of 73% at the end of 90 days compared with 49% in the case of scaffold made only of silk fibre.
  • Even at the end of 30 days, there was adequate bone regeneration and new blood vessel formation.

Superior graft

  • The bone graft fabricated and tested is superior to currently available ones, affordable and does not require external use of growth factors for bone cells to grow.
  • At the end of three months, the silk fibre had completely degraded leaving behind a homogeneous bone produced by rabbit bone cells.
  • The newly formed bone had healed the defective femur. The bone cement made of calcium phosphate becomes a part of the bone while the biocompatible metal ions (silicon and zinc) get leached out at the end of 90 days.

The Chemistry behind:

  • The scaffold is fabricated by first doping the bone cement with silicon and zinc and mixing the bone cement with chopped mulberry silk fibre.
  • The bone cement gets adsorbed on the silk fibre. Liquid silk fibre is then added to bind the chopped fibre and bone cement; the liquid silk also makes the composite highly porous.
  • The silk–bone cement composite has higher density and strength, more surface area and high surface roughness, closely resembling a native bone.
  • The zinc and silicon ions get leached from the composite and activate bone and blood vessel cells.
  • This leads to faster regeneration of the bone tissue and blood vessel formation.
  • By doping with these metal ions we are doing away with external addition of growth factor and also making the graft affordable.

Bone regeneration

  • The compressive strength of silk fibre is about 40 kPa, while it is nearly double in the case of the silk–bone cement composite.
  • Though doping with the silicon and zinc metal ions reduces the mechanical properties, particularly the compressive strength, the bulk strength of the doped composite is sufficient to activate bone regeneration.
  • Through in vitro studies carried out prior to experimentation with rabbits, the researchers realised that incorporation of bone cement and metal ion doped bone cement enhanced the bone tissue regeneration capacity.
  • While the composite was seeded with bone cells for in vitro studies, in rabbits, the composite was used without adding any bone cells. Bone cells from neighbouring tissue migrate and bind to the scaffold and aid in bone regeneration.
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