The skin is our largest organ. Unfortunately for one third of the population, their skin is affected by skin disease (1). This not only negatively influences their physical but for many also decreases their mental health (2). Understanding the cause and mechanism of a disease is important to design an effective treatment plan, but also to improve self-esteem.
The skin is covered by bacteria, which together with other species, like fungi, form the so-called skin microbiota. These bacteria are important for different aspects, for example to develop a healthy immune system and to retain a healthy skin barrier (3). However, if certain bacterial species colonise the skin or the ratio of normally harmless bacteria drastically changes, it can result in various skin diseases.
The best known and most common skin disease in adolescents is acne vulgaris. The origin of the chronic inflammatory disease is a complex network between genetic and environmental factors (4). The bacterial strain Cutibacterium acnes (C. acnes) is suspected to negatively impact the process of acne vulgaris progression. While for a long time it was believed that an increase in total C. acnes population of the skin caused the disease, nowadays studies show that dysbiosis, meaning an imbalance in ratio between the different C. acnes strains, is associated with the disease (5, 6, 7).
Figure 1: Ratio of different C. acnes strains in acne vulgaris on the face and back (5).
Even so, it is known that acne is caused by multiple factors, the European guidelines for treating acne vulgaris include the use of broad-spectrum antibiotics (7, 8). Broad-spectrum antibiotic use cleanses the skin from nearly all bacteria, which may help in reducing the symptoms short-term, but changes the resident microbiota in the long run and may result in antibiotic resistance (9).
Atopic dermatitis is another skin disease associated with microbiotal dysbiosis. In atopic dermatitis, patients suffer from itching and skin lesions, which can lead to cutaneous infections. The formation of the disease is, like in acne vulgaris, complex. Several internal and external factors interact and lead to the problematic skin condition. Staphylococcus sureus (S. aureus) is a bacterial strain known to worsen atopic dermatitis (10) and its colonisation on the skin results from dysbiosis of the normal and healthy microbiota.
Acne vulgaris and atopic dermatitis are only examples of various skin conditions associated with microbiotal dysbiosis. Establishing these associations of dysbiosis in skin diseases would strengthen skin-microbiota research and help to find sustainable treatment strategies for several skin conditions. Additionally, normalisation of the skin microbiota in already well studied skin diseases would improve the clinical state of patients and would be an effective strategy in reconstituting a healthy microbiota after treatment if antibiotic use is necessary.
MIKROSKIN aims to provide an easy and quick tool not only to study microbiotal dysbiosis in a research setting but in patients too for selecting and monitoring treatment of various skin conditions. By targeting several bacterial species at the same time the long-term aim is to create a high throughput test to detect dysbiosis in the skin microbiota.
The aim is to develop an aptamer-based rapid test that detects dysbiosis in the microbiota and induce a color change in a semiquantitative manner.
What is an aptamer?
Aptamers are small RNA or single strand DNA sequences that are about 100 nucleotides long. These short single-stranded nucleotide sequences can fold and form tridimensional structures. In this tridimensional state aptamers acquire recognition properties, meaning that they can bind to other molecules and targets. Using a technique called Systematic Evolution of Ligands by Exponential Enrichment (SELEX), aptamers are specifically selected and improved to bind only one particular target (11).
In general, aptamers are similar to antibodies. However, aptamers have some advantages compared to antibodies. Aptamers are easier to work with and cheaper to produce than antibodies. Additionally, aptamers are about 10 fold smaller than antibodies (11). This property enables them to target epitopes in locations that an antibody cannot reach.
In our project we use SELEX to select aptamers targeting specific skin bacterial strains and determine their abundance on the skin.
If you want to know more about the theory behind SELEX and the detailed protocol, click here
Our detection method is based on the colorimetric properties of Polydiacetylene (PCDA). PCDA can self-assemble into vesicles, which acquire colour-changing properties upon stress induction. External-stress, like heat, chemical or mechanical stress, induces a colour change from blue to red. It is possible to conjugate sensor molecules, like antibodies or aptamers to these vesicles, which in turn changes colour due to the binding of a specific target. This makes PCDA ideal for a biosensor (12).
If you want to know more about the theory behind our detection method and the detailed protocol, click here
By targeting different skin bacterial strains with our aptamers, we get detailed information about their presence upon our skin. By comparing these results with an internal control, sensing nearly all skin bacteria, we can calculate a ratio and thus see the proportion of the skin bacterial strains. This enables us to detect dysbiosis in the skin microbiota fast and easily, without the need of expensive sequencing or slow bacterial cultivation.
We can expand our targets by the selection of new aptamers against additional bacterial strains or even antibiotic resistant strains. Our aim is to make MIKROSKIN a high throughput testing tool with customisable targets. Users would be able to choose the targets, which the test should detect - tailored to the user's personalised needs. These adaptation possibilities make our rapid test MIKROSKIN a great tool for research and possibly also for clinicians and individuals.
Find out more about our stakeholders and implementation strategy, click here
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Lebegue, E., Farre, C., Jose, C., Saulnier, J., Lagarde, F., Chevalier, Y., Chaix, C. and Jaffrezic-Renault, N., 2018. Responsive Polydiacetylene Vesicles for Biosensing Microorganisms. Sensors, 18 (2) , p. 599.