Tissue Regenerating Plastics From Bugs – CPS Talk 02/12/14

-Article by Stephen Leach

Out of the 10 lectures I’ve witnessed this term, this was the first delivered by a female academic. According to WISE (Women into Science and Engineering), women represent only 13% of the employees in STEM industries. Once I’d finished my Garibaldi biscuit and gotten over the gender imbalance in the CPS microcosm, I focussed on the impending wave of awesome research that was about to break over the heads of the CPS devotees.

The talk was entitled: “Tissue Regenerating Plastics from Bugs” and was delivered by Dr. Ipsita Roy, Reader at University of Westminster and Guest Reader at Imperial College London. Having ‘bugs’ for a workforce can be pretty productive it seems; they are abundant, renewable and can be stimulated to tirelessly manufacture all manner of chemicals. Bacterial cells are able to synthesize molecules far more complex than humans can manage in a lab, for example, bacterially synthesized human insulin replaced the need for pig insulin, which understandably not all people would tolerate. Incidentally the molecules that Dr. Roy was discussing were not complex, but are destined for complex applications.

Dr. Roy is aiming to synthesize a biocompatible polymer that acts as a scaffold for the regeneration of new tissues in humans. She has found that one family of polymers show such diversity in their properties that they may find multiple applications within the body. All thanks to the industrious bacteria.

These polymers are produced naturally in some bacteria in order to store energy and carbon, analogous to the role of starch in plants. The polymer is a polyhydroxyalkanoate (PHA), these have variable side chains and varying lengths of unsaturated carbon chains between the polymerising functional groups, it is essentially a polyester. Dr. Roy has been championing this material for bio-implant applications because it is bio inert, it happily supports cell growth and displays such a range of useful mechanical properties. For example, by slightly varying the number of (CH₂) linkages in the chain the elasticity of the material can be changed by a factor of 1000.

I know I’m most productive when I eat molasses all the time and the little Bacillus Cereus are no different, in fact they gave a PHA yield of 80% of their dry cell weight.

The polymer is hoped to have applications for cell growth in bone, cartilage, skin and even heart tissue.

Using a composite of PHA and BioGlass™ (an existing osteogeneric material), Dr Roy is tinkering with a substance that reproduces the mechanical properties of bone, stimulates new bone growth and eventually harmlessly dissolves when the new bone is in place. Investigative work is being done to incorporate carbon nanotubes into the mixture to improve mechanical strength and provide a non-invasive means to monitor the material since the nanotubes are conductive.

The polymer can also be formed into amphiphilic microspheres which can be used to deliver and release drugs at a controlled rate, this technology could be implemented along with other applications to deliver antibiotics at the sites of new bone growth, preventing possible infection.

Finally the material can even be used to make patches that could stimulate the growth of new cardiomyocytes over scar tissue in the heart. Tests have shown that cardiomyocytes are supported and grow well on the material in-vitro.

Its early days for this polymer, so far it has been FDA approved for use as a suturing material, this shows that its biocompatibility is fully trusted. Dr. Roy is ready to follow up with a whole range of new products, for example, stents, nerve conduits and perhaps in the future some of the more exotic cases as mentioned above. 

With that the CPS lectures for the term are done. All that is left on the horizon this year is the CPS Christmas quiz…