Team:Aalto-Helsinki/Concept

• Laboratory
  • Overview
  • Theoretical Background
  • Materials and Methods
    • Protocols
  • Results and Discussion
  • Future Perspectives
• Modeling
  • Overview
  • Theoretical Background
  • Simulation Setup
  • Results and Discussion
• Human Practices
  • Overview
  • Project
  • Public Outreach
  • Judging
• Community
  • Overview
  • Parts
  • Composite Part
  • Improved Part
  • InterLab
  • Collaborations
• People
  • Team Members
  • Advisors
  • Attributions
  • Sponsors

PROJECT

Story
Dialog
Safety
Ethics
The Concept

The Concept

We wanted to create a concept that gathers together the whole project we have been working with. The purpose of the concept is to have a way to communicate with people about possibilities of synthetic biology. Skin care and acne turned out to be really good way to do that, because it is part of almost everyone’s daily life in a way or another and with it it was easy to build a bridge between science and people. The concept itself is simple and easy to understand. Our aim was to create purifying skin care product for people suffering from acne. Our primary of importance was to create non-toxic and safe product that doesn’t cause any environmental impacts, is easy to produce and simple to use.

Porifi - Purify your pores from acne bacteria

Our application for antimicrobial dermcidin is exfoliating skin care product made out of cellulose hydrogel. Important part of taking care of acne is to remove and exfoliate dead skin gently and purify the skin. Cellulose hydrogel is natural and non-toxic substance that could be ideal for store dermcidin in. By changing content and amounts of water and CMC it was possible to have different viscosities and feelings of hydrogel. By testing different kind of compositions we ended up using one with..

Picture on the left: Michal and Maisa making the hydrogel
Picture on the right: Hydrogel sample ready for density measurement

Hydrogel sample

For exfoliating beads ideal material would be cellulose that dissolves in water as time passes but not too fast when product is stored and still under use. Dermcidin could also be bonded with cellulose based bead. In our product trial we used grinded peach stones.

Peach stones

Picture on the left: Filters for the grinding machine
Picture on right: Andreas Lindberg helping us with the grinding machine

Smooth as a peach - The product

From the survey and meetings with professionals and people suffering with acne we got valuable information what kind of products people in general are willing to use and what kind of effect they are looking for form the product. We wanted to make our product application as simple and user friendly as possible. Instead of making purifying mask that user should wear 10 to 20 minutes we decided to make easy exfoliating gel. User only needs add it on skin, rub it gently on the skin and rinse away.

The efficiency of the product is based on both antimicrobial dermcidin component which could increase the natural dermcidin balance on the skin and exfoliating the dead skin by rubbing peach stone beads gently on the skin.

Why cellulose

Sustainable and environmentally friendly thinking was important part of application design process. We decided to use cellulose together with dermcidin because cellulose has a versatile forms and compositions and it is environmental friendly and rising economy in Finland.

Cellulose also began sound very interesting because of the possibility to add cellulose binding domain into our dermcidin peptide. With cellulose binding domain antimicrobial dermcidin could be attached to different kinds of bandages, cotton pads and dressings and it could be used as an alternative for example for antimicrobial silver bandages used widely in wound care. Also in skin care we were first thinking about using cellulose based paper mask or some kind of cotton pads where we could tie up dermcidin. But based on our survey results and discussions with cosmetologist and dermatologist we decided to concentrate more on purifying product with exfoliating properties. Many beauty and skin care products contains environmentally harmful ingredients like micro plastic beads. We wanted to find substitutes for those and create as pure and natural antimicrobial product as possible. We decided to concentrate on cellulose based hydrogel (CMC) because it is safe, non-toxic and easy to experiment with. We got lot of help from Andreas Lindberg Doctoral candidate, Aalto University, School of Chemical Engineering.

Hydrogel pH

We measured pH of CMC-hydrogel to see if it promotes the antimicrobial activity of dermcidin. Using pH test strips, we obtained the pH value of about 6, whereas pH of skin varies from 4.5-5.75 and the theoretical value for dermcidin is about 5.

Hydrogel viscosity

Viscosity correlates resistance to flow and thickness of a substance. In case of our cosmetic formulation, it affects cleansing efficiency and user perception. Iit also impacts the way the product should be stored and thus, a packaging choice. Moreover, the high enough viscosity is required to prevent exfoliant from sedimentation at the bottom of the package.

Hydrogel samples

Carboxymethylcellulose (CMC)-based hydrogel is the base component of our cosmetic formulation. For testing purpose, we used two grades of CMC manufactured by CP Kelco (#picture, choose one below), Cekol 2000 (low modular weight polymer) and Cekol 50000 W (high modular weight polymer). We prepared several aqueous solutions of different CMC concentrations (5%, 7% solutions of Cekol 2000; 1%, 2% and 3% solutions of Cekol 50000 W).

Based on that, we could check initially how the cosmetic formulation would “feel and look”, and got the first candidates for our products.

Viscosity measurement

We also decided to measure actual viscosity values of the hydrogel samples. Measurement setting We conducted measurements using Brookfield rotational viscometer with RV spindles.

We kept temperature constant at 24-25°C and measured hydrogel viscosity at different spindle speeds (0.1 - 200 RPM). We decided to test the hydrogel samples at broad range of speeds due to its non-newtonian behaviour which means that its viscosity decreases under shear strain (shear-thinning effect). Moreover, assuming that the cosmetic will undergo different shear stress while scooping out from the package, keeping still on fingers, and applying on face by rubbing, we were interested how viscosity would change then. We neglected, however, temperature effect by that.

Results

The results of our measurements confirmed the non-newtonian behaviour of the CMC-based hydrogel. When the shear stress increases, the viscosity decreases for all samples (#graph). The viscosity changes by one or two orders of magnitude with applied shear depends on CMC grade. However it is also completely and instantaneously reversible and the original viscosity is retained when the shear stops.

According to the CMC information booklet provided by the CP Kelco company [1], the pseudoplastic flow behavior is related to de-entanglement and orientation of the CMC molecules in the direction of the flow. It seems to be seen in our results, where a longer chain molecule (higher molecular weight), as found in 3% Cekol 50000W CMC, is more "shear thinning" compared to the shorter chain molecule found in 5% Cekol 2000 CMC at higher spindle speeds.

The viscosity is proportional to the average chain length of the CMC molecule. The average chain length determines the molecular weight of the CMC grade. Thus, the viscosity at low speeds increases more rapidly for long-molecule CMC than short-molecule one with increasing concentration. The higher viscosities can be also obtained for long-molecule CMC despite lower concentration of the solution.

The excel file contains the table of viscosity values with related graphs, as well as more detailed description of the test-bed configuration for particular measurements.

Conclusion

We were looking for the hydrogel composition which would not only remain stable at rest in the package as well as by scooping it with fingers and then applying it on face, but also which would get liquid enough while rubbing and exfoliating dead cells. Based on the perception as well as on the result of the viscosity measurements, the aqueous solution of 3% CMC with long chain molecules appears to be the good choice. 7% CMC with short molecules is another option.

Hydrogel with exfoliant

Cosmetics is one of the major sources for microplastics that end up in the environment. We were critical of microbeads which many cosmetic companies use as exfoliating agents in their products. Microbeads are tiny plastic particles which end up in the oceans, as they cannot be filtered from our waste waters. After, through plankton, they start to accumulate in fish and fish-eating birds [2]. In the beginning of 2017 microplastics were already detectable from table salt. We used natural beads made of peach pits. We grinded them to achieve the beads of different particle sizes: coarse (heavy), medium (mix) and fine. Then, we added them to hydrogel samples to get different compositions. The viscosity also impacts the sedimentation rate of exfoliating beads suspended in the hydrogel.

Exfoliant sedimentation and user perception tests

First, we compared all samples by sensing and realized that the fine exfoliant felt too delicate in all prepared hydrogels. On the other hand, the coarse beads were quite big and had sharp edges. The medium exfoliant seemed to nicely blend with hydrogels and provide good exfoliating effect.

After testing based on perception, we left the samples for several days to see what would happen with the exfoliants. It turned out that the most viscous solutions, 7% Cekol 2000 and 3% Cekol 50000 W, remained stable and kept the beads uniformly distributed (#picture). However, we also noticed the degradation of cellulose chains in the hydrogels due to microorganisms growth, which resulted in severe viscosity reduction.

Hydrogel degradation

Although CMC has good stability towards degradation– enzymes and oxidants may still degrade it. Enzymes produced by microorganisms, may degrade the cellulose chain, and thus, cause serious, irreversible viscosity decreases. [1]

It happened to our samples while keeping them in room temperature and being exposed to light. We were warned about the possible spoilage in the talk with one expert, but despite that, we had neither carefully sterilized the peach pits nor added any preservative before. In result, after one week, two samples (1% and 2% Cekol 50000 W with the fine exfoliant) completely turned into cloudy liquids. Some other were affected by mold and the degradation process started too. After another week, the cellulose chains in most of other samples were either entirely or almost entirely degraded (#picture).

Pic: a,b) Degraded 3% Cekol 50000 W with medium exfoliant - cloudy liquid on top and severely c) Mold in 7% Cekol 2000 with heavy exfoliant

An efficient way to stop enzymatic attacks is thus to prevent growth of microorganisms. This can be done by adding preservative. The CMC manufacturer suggest the following preservatives for food, cosmetic and pharmaceutical uses:
- Sodium benzoate
- Sorbates (Na and K salts)
- Sodium propionate
- Methyl parahydroxybenzoate
We also searched for other preservatives which are commonly used in cosmetics. The attachment presents the list of several other preservatives with brief descriptions.

Preservatives

Due to problem with microorganism growth in the hydrogels, we decided to check the effect of adding a preservative on the solution stability. We picked the benzyl alcohol for a trial, because it is used in a wide variety of cosmetic formulations [3]. According to Cosmetic Ingredient Review, it is safe to use in cosmetic products at concentrations of up to 5%. However, in the European Union, benzyl alcohol is allowed at maximum concentration of 1% in ready for use preparation [4].

Although benzyl alcohol can be considered as a natural ingredient as many plants, fruits, and teas have it as a component. On the other hand, the cheaper synthetic version is usually used in products, which is produced by mixing benzyl chloride with sodium hydroxide. Other ‘natural’ alternatives are also available and could be also considered in the future.

Benzyl alcohol is a colorless liquid and has a mild, pleasant aromatic scent, so it is used not only as a preservative but also as a fragrance ingredient. We assumed that our cosmetic product should be odorless or with subtle aroma. However, during testing benzyl alcohol as the preservative we got annoyed with its perfumed smell. After mixing the components, the smell was not so irritating anymore, but it is important to consider the influence of preservatives and other additives on the finished product aesthetics such as odor, color and viscosity.

Moreover, the interaction of benzyl alcohol or other preservatives with the dermcidin should be investigated in the future to provide the anti-acne features of our product. The testings we made with benzyl alcohol turned out to be promising and within one week no microorganism growth wasn’t found. In the future more test are required and we were also taking into account the possible effect of sterilization of the beads and order to avoid contamination.

Sterilized peach beads.