Silk-based bone graft revealed extensive bone formation

Silk-based bone graft revealed extensive bone formation

Researchers at Indian Institute of Technology Guwahati have developed a scaffold made of silk-bone cement allowing bone graft that successfully regenerated new bone tissue in animal study.

The scaffold is fabricated by doping the bone cement with silicon and zinc and mixing with mulberry silk fibre. The silk-bone cement composite is a high density structure proving good strength, porosity and surface area closely resembling a native bone.

The study was performed in rabbits with a defective thigh bone. The bone graft resulted in extensive bone formation within ninety days by which the silk fibre showed to have completely degraded. The newly formed bone revealed to seamlessly join with the existing bone, and had blood vessels inside it.

“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,” said the lead researcher Prof. Biman Mandal, Department of Biosciences and Bioengineering, IIT Guwahati in a press release.

The bone cement made of calcium phosphate become part of the bone while the biocompatible silicon and zinc metal ions get leached out at the end of three months.

“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,” said Prof. Mandal. “By doping with these metal ions we are doing away with external addition of growth factor and also making the graft affordable.”

“While the silk scaffold provides the physical cues, the silicon and zinc metal ions provide the chemical cues. These two synergistically mimic the biological cues which people use for tissue engineering,” explains Joseph Christakiran Moses, Department of Biosciences and Bioengineering, IIT Guwahati and first author of the paper.

Demonstrating the formation of new blood vessels, Moses said: “Silicon and zinc trigger a molecular response within the bone cells which makes them feel that they are lacking oxygen (triggering hypoxia response element). So the bone cells start secreting pro-blood vessel forming (angiogenic) signals leading to vascularisation.”

The silk-bone scaffold was used in the study without addition of any bone cells unlike in in vitro studies where the composite is seeded with bone cells.

“Bone cells from neighbouring tissue migrate and bind to the scaffold and aid in bone regeneration,”said Prof. Mandal .

The study was published in the journal ACS Biomaterials Science & Engineering.

The team is now validating the bone graft in large animals for clinical translation.

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