29/08/2018

Here, at iGEM Lahore, we aim to use genetic engineering principles to create a biomaterial known as nacre, which is the primary constituent of the outer coating of pearls. Nacre occurs naturally and consists of inorganic calcium carbonate plates connected by a framework of organic molecules. The material itself consists of several proteins in an inorganic and organic matrix. Each protein is coded by a gene, which we need to incorporate in a plasmid. A plasmid is essentially a circular piece of DNA found in bacterial cells and is very useful in this particular field as it is easy to move around and alter. The plasmid also consists of certain genes which are not essential; those can be removed with the help of enzymes known as ligases. They cut the plasmid at certain points known as restriction sites and once the gene sequences are removed, the plasmid can incorporate foreign DNA, which can produce the desired proteins. For iGEM, participants most often utilize either yeast or E. Coli cells, with our team opting to use the latter.

An issue which we face is that nacre consists of several proteins (around 30 in total). To incorporate all of those genes within a single plasmid would be very difficult and, to an extent, not doable as even nature have its limits. So, to overcome this issue, we have decided to select the gene sequence for the proteins we found most important in crystal and matrix formation. These include pearlin, dermatopontin and PfN23 among others. Another hurdle which we have to overcome is mimicking the conditions of the oyster. In the oyster, pearl formation is an immune response which comes about when an irritant enters the shell. The nacre depositions aim to seal off the irritant. We have to ensure that the crystal formation takes place the way it normally would, forming platelets known as aragonite which form polygonal tablets, at a faster rate than usual. Because of its precise structure, nacre also has a number of useful physical properties, such as high tensile strength. Moreover, we have to mimic the very tightly controlled process while simultaneously taking into consideration the rate at which it is happening.

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