The Tewitro® TW 24 is the only device to measure the water evaporation from cultured tissue sets (wells in a plate with medium) in up to 24 wells simultaneously with the worldwide most used “open chamber” measurement of the Tewameter®.
For each product to be applied to the skin, safety measurements are indispensable. The use of skin tissue models for long-term safety tests is a quick and easy method to avoid using animals or volunteers.
Whenever the barrier is damaged, the evaporation rate will increase immediately. Also for claims related to barrier improvement/enhancing, tests on cultured cells are needed, as products meant to keep the barrier intact or to even improve it, can be detected by a stable Transepidermal Water Loss (TEWL).
The Tewitro® is well-suited to non-invasively monitor TEWL of cultured skin tissue samples. These results open up new opportunities to monitor the dermal barrier physiology under different experimental conditions and treatments in vitro.
See a video on a typical application with the Tewitro® (product efficacy).
Fully equipped, the Tewitro® TW 24 can be used in standard 24-wells plates (6x4). The probe features 6 slots with 4 measurement inlets each. Each measurement inlet features two sensor pairs constantly measuring temperature and relative humidity, thus measuring in an indirect way the density gradient of the water evaporation from the surface of the bottom of the well. This gradient equals the Transepidermal Water Loss typically measured on the in vivo skin surface in g/h/m². This "open chamber" TEWL measurement method is the worldwide most-used method to quantify the barrier function of the skin. Hundreds of publications prove this fact. The Tewameter® had even been used on board of the International Space Station (ISS) to monitor the astronaut's skin during long-term exposure in space.
The Tewitro® TW 24 can measure in the well plates of cultured tissue. Until now, we have experience with the following readily on the market available models:
The Tewitro® TW 24R comes with special accessories (slightly higher feet and stainless steel diffusion tubes) to allow TEWL measurements on full thickness reconstructed epidermis.
Phenion® FT (https://www.phenion.com) by Henkel directly in the wells.
For the measurement of TEWL, the plate with the wells and the measurement probe has to be heated to skin temperature. The laboratory condition is rather cool (20-22°C), in this condition differences in TEWL are barely visible. As soon as the system is heated to skin temperature, the differences become immediately obvious. We recommend to use a heating plate with a temperature around 33 °C.
See a video on a typical application (product efficacy).
On pre-cultured tissue before the product(s) to be tested are applied:
Constant measurement of the evaporating water which is typical for the wells when coming out of the incubator until a normal TEWL value (for incubated cell cultures) is reached. When the probe starts to measure, the TEWL is very high but constantly decreasing. As soon as it has reached a stable plateau, it indicates that the tissue cultures are now ready for the application of the product. At the same time, the recorded TEWL is a control value (before application).
Measuring the actual effect on the barrier function of applied products (safety & efficacy):
When the well-plate comes out of the incubator, the TEWL measurement can again be used to monitor when the surplus humidity from the incubator has left the samples and the real measurement time starts. Depending on the nature of the applied products the barrier of the cultured tissues is more or less intact. When the barrier has been damaged, particles of the cells can be found (microbiologically) in the surrounding medium. However, the degree of damage or barrier improvement can very accurately be indicated by the monitored TEWL- values. The higher they stay, the less intact the barrier.
The Tewitro® TW 24/24R probe comes with its own software and an MPA 2 unit (please see details in Basic Probe Systems).
Probe TW 24
Dimensions: 113 (W) x 170 (L) x 33 (H) mm (for the basic feet), weight: 300 g, cable length: approx. 1.20 m, frame material: anodized aluminum (AlMg 3), power consumption: max. 12 V
Sensors: 24 sensor pairs (48 single sensors)
Measurement range: Temperature: 0 - 50° C, resolution: typ. 0.015 °C, RH: 0% - 100% RH, resolution: typ. 0.01 % RH, TEWL: 0 to 320 g/h/m²
(RH ≤ 92%): ± (5 % of the displayed TEWL result + 1.0 g/m²/h)
(RH > 92%): ± (10 % of the displayed TEWL result + 2.5 g/m²/h)
Operating conditions: T: 10-40° C, RH: 30-70 % RH
Probe TW 24R
See TW 24
Dimensions: 113 (W) x 170 (L) x 42 (H) mm
Stainless steel tubes: 27 mm, 11 mm Ø
Technical changes may be made without prior notice.
Other related probes available: