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Tewitro® TW 24
Transepidermal Waterloss Measurement in Skin Tissue Models
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Overview
The Tewitro® TW 24 is a specialized laboratory instrument designed by Courage + Khazaka Electronic to analyze the barrier function of cultured skin tissues. This device utilizes the “open chamber” method to simultaneously monitor transepidermal water loss (TEWL) across 24 separate wells in a single plate. By providing a non-invasive way to measure evaporation rates, it allows researchers to conduct safety and efficacy trials without relying on animal testing. The system is compatible with various commercial tissue models and includes dedicated software to track stability, temperature, and humidity during experiments. This technology is essential for evaluating how cosmetic products or external treatments impact the integrity of the dermal barrier in a controlled environment.temperature, and relative humidity data to be recorded and displayed during measurement.
Barrier Integrity Testing: The New Standard for In Vitro Skin Safety and Efficacy Research
The global shift driven by ECVAM, OECD, and REACH guidelines mandates the minimization of animal and human volunteer testing. In vitro cultured skin tissue models are now the regulatory standard for safety, dermal absorption, and efficacy assessments.
Quantifying barrier integrity on cultured cells is no longer optional. it is the fundamental baseline for modern dermatological research.
Features
TEWL measurement on up to 24 wells simultaneously
Measures water evaporation from cultured tissue models in standard 24-well plates, allowing all wells to be assessed under the same conditions.
Open-chamber Tewameter® principle
Uses the worldwide established open-chamber TEWL measurement method to evaluate barrier function without causing occlusion.
Designed for cultured tissue models
Suitable for in vitro skin tissue models and barrier function studies, supporting safety, efficacy, permeability, and dermal absorption testing.
24 sensor pairs / 48 single sensors
Each measurement inlet includes sensor pairs for temperature and relative humidity, allowing indirect calculation of the water vapor density gradient.
Long-term measurement capability
Supports measurements from a few seconds up to 24-hour long-term studies, making it useful for time-dependent tissue monitoring.
Organized software with complete data view
Software displays 24 TEWL values, adjustable averages, standard deviations, and individual temperature/RH values for upper and lower sensor pairs.
Automatic stop conditions
Measurements can stop automatically based on stability or defined measurement time, helping standardize protocols.
Check calibration and offset function
Includes easy and quick check calibration and offset functions to support reliable measurements.
Ambient condition recording
When connected, the Ambient Condition Sensor records environmental values continuously and saves them with the results.
TW 24R option for full-thickness models
The Tewitro® TW 24R includes special accessories such as higher feet and stainless-steel diffusion tubes for TEWL measurement on full-thickness reconstructed epidermis.
Technology
The Tewitro® TW 24 uses the established open-chamber Tewameter® measurement principle to evaluate water evaporation from cultured tissue models in standard 24-well plates. It is designed to measure TEWL on up to 24 wells simultaneously, making it suitable for parallel in vitro skin barrier studies.
Each measurement inlet contains two sensor pairs that continuously measure temperature and relative humidity. From these values, the system indirectly calculates the water vapor density gradient above the tissue surface, which corresponds to transepidermal water loss expressed in g/h/m².
The device is built with 6 slots, each containing 4 measurement inlets, allowing the full 24-well plate format to be monitored under comparable conditions. This setup enables researchers to evaluate barrier function, permeability, dermal absorption, and product effects across multiple tissue samples at the same time.
Through its dedicated software, the Tewitro® TW 24 displays individual TEWL values for each well, adjustable averages, standard deviations, and separate temperature/RH values for the upper and lower sensor pairs. Measurements can run from a few seconds up to 24-hour long-term studies, with automatic stop conditions based on stability or defined time.
Discover how to use the Tewitro® TW 24 for in vitro TEWL measurement on 24-well plates.
Reconstructed Tissue Models Compatibility
Tewitro® TW 24 is compatible with various tissue models like Epiderm®, Episkin®, and Labcyte.
A specialized version, the Tewitro TW 24R, features stainless steel diffusion tubes and higher feet for measuring full-thickness reconstructed epidermis (e.g., Phenion® FT)
Software Features
Comprehensive Data Display
The software shows 24 individual TEWL values simultaneously, along with adjustable averages and standard deviations.
Detailed Sensor Tracking
Users can view and save the specific RH and temperature values for both the upper and lower sensor pairs for every inlet separately.
Automated Controls
The system includes automatic stop conditions based on measurement stability or a specific time limit.
Safety and Calibration
It features a warning system for high relative humidity levels and provides tools for quick calibration and offset checks.
Environmental Monitoring
If an Ambient Condition Sensor probe is connected, its values are recorded and saved alongside the results
Application
Safety and Efficacy Testing
The system is an indispensable tool for measuring the safety of products before they are applied to human skin. It is specifically used to study skin permeability and dermal absorption, which are key requirements for these tests.
Barrier Health Monitoring
The device is used to non-invasively monitor the physiology of the dermal barrier under various experimental conditions and treatments. It can accurately indicate the degree of barrier damage or improvement by monitoring changes in TEWL values.
Claim Support and Validation
For products marketed to improve or enhance the skin barrier, the Tewitro TW 24 can validate these claims by detecting a stable TEWL value, signifying the barrier is intact.
Replacement for Animal Testing
Utilizing cultured cell sets provides a quick and easy method for long-term safety tests that avoids the use of animals or human volunteers. This approach aligns with global guidelines from institutions like ECVAM, OECD, and REACH.
Quality Control of Tissue Cultures
Before applying a product, the device is used to monitor tissue samples as they come out of an incubator. This ensures the cultures are healthy and have reached a stable plateau, providing a baseline control value for the experiment.
Comparative Product Testing
Because the system measures up to 24 wells simultaneously under the same microclimate, it is used to perform reproducible, repeated tests on multiple products or formulations under identical conditions.
Available Configuration
The Tewitro® TW 24 can be connected to compatible Courage + Khazaka MPA2 system.
MPA2
FAQs
What is the Tewitro® TW 24 used for?
The Tewitro® TW 24 is used for in vitro TEWL measurement on cultured tissue models in standard 24-well plates. It helps evaluate barrier function, permeability, safety, and product efficacy.
How many wells can be measured at the same time?
The system can measure up to 24 wells simultaneously, allowing all tissue samples to be tested under the same environmental and timing conditions.
Why is simultaneous measurement important?
After cultured tissues are removed from the incubator, the microclimate changes quickly. Measuring all wells at the same time improves reproducibility and avoids timing-related differences between wells.
Does the Tewitro® TW 24 use the open-chamber method?
Yes. It uses the open-chamber Tewameter® principle, which allows natural evaporation without occluding the tissue surface or disturbing the normal water loss process.
Can Tewitro® TW 24 be used before product application?
Yes. It can measure baseline TEWL values before product application. This confirms tissue stability and provides control values for later comparison.
How many measurements can one cartridge perform?
Each Sebumeter® cartridge can be used for approximately 400 measurements. The cartridge includes a scale from 1 to 0 to show how much unused tape remains.
What does high TEWL indicate in cultured tissue models?
Higher TEWL values generally indicate a weaker or damaged barrier, while stable lower TEWL values suggest a more intact barrier function.
Can Tewitro® TW 24 support long-term measurements?
Yes. The system supports continuous measurement over longer periods, making it suitable for time-dependent studies, barrier monitoring, and product effect evaluation.
Why must the tissue samples be heated to 33 °C?
Tissue samples should be heated to approximately 33°C to mimic real human skin temperature and ensure more accurate TEWL measurement.
At normal lab temperatures of around 20–22°C, differences between samples may be difficult to detect. Heating the samples makes barrier function differences and evaporation rates clearer, measurable, and more physiologically relevant.
What are the differences between the TW 24 and TW 24R models?
The main difference between Tewitro® TW 24 and TW 24R is their physical configuration and target tissue model.
Both systems use the same open-chamber TEWL measurement principle and sensor technology, but:
- TW 24 is designed for standard cultured tissue models such as EpiDerm, EpiSkin, and LabCyte.
- TW 24R is a specialized version optimized for full-thickness reconstructed epidermis, such as the Phenion® FT model by Henkel.
Are there adapters available for other tissue models?
Additional adapters are available for several specific tissue models, and custom fitting may be possible upon request.
Supported models include:
- Episkin® / SkinEthic® RHE and RHPE — 8 mm, 0.5 cm²
- MatTek EpiDerm® — 24-well set
- Thermo Fisher Scientific Nunc® — adapters for wells and height
- Merck Millicell Millipore — model PIHP01250
For other tissue models, a sample can be provided to the manufacturer to check whether a custom adapter can be made.
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