Copolymer Bioplastic: Candidate for Synthetic Bone?

A copolymer of bioplastic Polyhydroxybutyrate (PHB) and Polyethylene Glycol (PEG) has been discovered by to be of use in Tissue Engineering and could be a candidate for producing synthetic bone. The discovery was made by Singapore based A*STAR and was published in the Journal of Physical Chemistry.

Tissue Engineering makes use of stem cells, growth factors and scaffolds to control cell differentiation to produce different types of tissue; for example, blood cells, skin cells or neural tissue. The combined effect of the growth factor and scaffold controls which cell type the stem cell becomes and the form of the tissue, respectively. Bone is a tissue with a complex structure, including several cell types, mineral deposits, fibrous material and a network of blood vessels. Finding the right material to use as a scaffold to produce bone can be difficult. There is value for being able to produce synthetic bone to treat conditions such as osteoporosis, broken bones or for bone grafting procedures, though this technology is still young and needs development before use in treatment.

The A*STAR Institute of Materials Research and Engineering have been working on co-polymers to act as scaffolds for tissue engineering; their latest development here is a co-polymer made of PHB and PEG. PHB is a biodegradable biopolymer polymerized from Hydroxybutyrate which in turn is produced from bacteria. PEG is also biodegradable and can be produced from bio feedstock by companies such as Novepha. Most importantly, these polymers are biocompatible; if implanted in humans there would be a low risk of rejection by the patient. Alone, PHB is unsuitable because it is brittle and stem cells have difficulty attaching to it, but combined with PEG the resulting co-polymer is more flexible and the attachment problem is removed; chemically it’s properties are like that of the fibrous material found in bone. This polymer is then electrospun to create a structure that physically resembles the porous structure of bone. When used as a scaffold the PHB-PEG co-polymer successfully created a material like living bone when it was treated with “simulated body fluid”; it absorbed water and salts, mineralized and allowed connective tissue to form between cells.