Team:Manchester/Description
PROJECT DESCRIPTION
「Currently, available hair dyes are harmful to
the environment as well as the end consumer」
One of the many health concerns associated with hair dyes includes allergic reactions; many hair dyes on the market today contain chemicals such as para-phenylenediamine (PPD), a known irritant, according to the NHS. Additionally, there has been published peer-reviewed research papers that suggest a correlation between the use of hair dying products and the chance of cancer development.
However, there is controversy within the scientific community and hence more studies need to be undertaken. A more common side-effect of bleaching and dying hair is damage to the hair fibre, resulting in thin and brittle hair.
Additionally, hair dyes are known pollutants which can become environmental hazard when improperly disposed as they may end up in the water supply.
Once we became aware of these problems we wondered;
What if bacteria could serve as a replacement to chemical hair dyes?
Our solution is to genetically engineer a bacteria which naturally adhere to hair, to secrete a dye replacing the use of potential pollutants and carcinogens contained in hair dyes.
Soon after, we developed our idea further. We came up with an ambitious project, where our engineered bacteria will also be designed to secrete reparative proteins to help maintain and restore the integrity of the hair as well as volatile fragrance compounds, in addition to the colour proteins of our choice.
We initially proposed the use of a genetically engineered E. coli (ATCC ® 25922) to develop this modular, multifaceted product that fulfils many of the needs of hair product users. However, through our time in the lab, we were also able to experimentally prove that other E. coli strains such as DH5a and BL21 (DE3) would also adhere to hair. We additionally believe that other probiotic strains such as E. coli Nissle 1917 would be worth of future research. Our experimentation also proved the resilience these bacterial strains have when exposed to different stresses (salt, chlorine or shampoo; see hair adhesion).
The bacteria will be engineered to secrete 3 compounds to colour, shape, repair, and scent the hair while remaining attached to the outer layer of strands.
COLOUR
Conventional hair dyes contain potentially harmful compounds. These compounds are used to open the cuticle, the outermost layer of hair (see Figure 1) to allow the colour pigments to infiltrate the cortex.
Some of these compounds are responsible for allergic reactions. Around 42% of hair dye users have experienced adverse reactions to hair dyes, of which allergic itching and headache are the most prevalent. Diamines, such as the previously mentioned PPD, are important constituents of hair dyes; however, they become absorbed by the skin resulting in many unpleasant side effects. PPD itself is also a known carcinogen, mutagen and environmental hazard.
Moreover, diamines are not the only harmful chemical found in hair dyes, other compounds such as p-aminophenol are suspected carcinogens and environmental hazards. These potentially harmful compounds can get into the water supply as a consequence of their disposal, which results in water contamination and may ultimately risk the health of humans and the environment.
Aesthetically, hair dyes are also known to cause hair damage, as bleaching agents modify and deteriorate the ultrastructure of hair. Compounds such as ammonia, which is commonly used in dye products, are required to open the cuticle to allow pigment infiltration of the cortex. However, in many cases, the cuticle fails to re-seal leading to damage. Our solution is to use a protein-based chromophore to bind to the outer layer of the hair. This is a much safer alternative as it reduces the need for harsh chemicals and bleaching to get pigments into the hair (Figure 1).
In order to select our chromophores, we used computational modelling, based on extinction coefficients and Beer-Lambert’s law, to identify the most effective dyes. We aimed to have a set of three primary colours: red, green and blue, as it would enable us to produce any hue through mixing, like paint.
We also designed a hydrophobic tail, attached to the protein-based dye, able to migrate and embed in the β-layer of the cuticle. This holds our chromophore in place through hydrophobic interactions
HAIR REPAIR & STRAIGHTENING
Dying hair is not the only cause of hair damage; stress, heat, age and diet can all factor into the loss of hair integrity.
According to Mintel reports in 2010, 33% of women owned a pair of straighteners and used it daily. Hence, a large percentage of people worldwide use a damaging instrument to modify their natural hair-shape.
Our solution is the production of a small peptide (11 amino acids) which has been shown to alter hair-shape (they straighten the hair). These small decapeptides infiltrate through the cuticle into the cortex where binding to keratin causes macroscopic hair-shape changes.
Additionally, the decapeptides have also been seen to repair damage.
Therefore, the production of these decapeptides by our engineered E. coli will provide the option to straighten hair in a heat-free manner, preventing damage and also repair previously damaged hair.
Scent
Although most hair care products are scented, these scents are volatile and rapidly lost.
Here, just as for the dye selection, we first compare Odour Detection Thresholds, ODthreshold, enabling us to select fragrances to which humans are naturally sensitive, such as the scent of vanilla, or the one if citrus fruits. We also model a solution to Fick’s Second Law, identifying the expected level of fragrance production and allowing us to determine that we need to modify our BioBricks to express both odorants more strongly.
Below we depict a schematic representation of our product idea.
Figure 1 Overview of Cutiful (original figure- various sources)
Detailed layers of the cuticle to further outline the mechanism of interaction of the biosynthesised compounds produced by the engineered E. coli and to outline the product concept. Genetically Engineered E. coli produces and secretes: (1, left) protein-based dye attached to a hydrophobic tail that allows embedding in the outermost cuticle layer of the hair allowing pigmentation of the hair without cortex infiltration; (2, middle) in-situ production and secretion of volatile smell compounds such as vanillin or limonene; (3, right) secretion of decapeptide molecule that infiltrates into the cortex and allows shape-change avoiding the use of heat tools and consequently damage. All components (1, 2 and 3) will be tested in different plasmids for expression and finally expressed together on the chromosomal genome.
We have managed to discuss our project ideas with a number of stakeholders and experts, who have enabled us to understand the needs of potential customers. This has shown a general enthusiasm about our idea, but has also identified consumer safety concerns as an important aspect of the type of product we envisage. This has made us think of additional safety measures such as the addition of a kill switch. This kill switch avoids conjugation and subsequent transformation of adjacent bacteria. Therefore, if consumed or poorly disposed into the water supply our safety kill switch will inhibit the spread of our engineered E. coli and its engineered genes in the environment.
We hope that this project lays the foundations of synthetic biology in hair care, where future projects may involve engineering metabolic pathways to produce oils commonly found in shampoos, for example. This project may ultimately facilitate the expansion of the hair-industry market into safer and sustainable novel products using synthetic biology, and novel methods, like in situ biosynthesis of compounds. In conclusion, we aspire to produce an innovative and friendlier alternative, which can target the major health and environmental issues encountered within the currently marketed options as well as coming up with a solution against hair damage when colouring hair.