µTongue: A Microfluidics-Based Functional Imaging Platform for the Tongue In Vivo
April 22nd, 2021
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The article introduces the µTongue (microfluidics-on-a-tongue) device for functional taste cell imaging in vivo by integrating microfluidics into an intravital imaging window on the tongue.
Overview
This article presents a detailed protocol for intravital fluorescence microscopy of taste cells in vivo using the microfluidic-integrated µTongue system. The method enables functional imaging of taste cells in a live mouse under controlled exposure to multiple tastants, preserving the natural microenvironment, neural connections, and blood circulation. The protocol covers preparation, mounting, imaging, and data analysis, offering practical tips for troubleshooting.
Key Study Components
Area of Science
- Intravital fluorescence microscopy
- Sensory biology
- Microfluidics
- Neurobiology
Background
- Intravital microscopy is widely used to study multicellular dynamics in live animals.
- Application to the taste sensory organ has been limited due to technical challenges.
- The µTongue system integrates microfluidics with an imaging window for the tongue.
- This allows controlled delivery of tastants and real-time imaging of taste cell activity.
Purpose of Study
- To provide a step-by-step protocol for using the µTongue system for in vivo imaging of taste cells.
- To enable functional analysis of taste cell responses under physiological conditions.
- To facilitate investigation of cell-to-cell communication in taste buds.
Methods Used
- Preparation of tastant and artificial saliva solutions.
- Setup of a pressurized microfluidic perfusion system for controlled tastant delivery.
- Surgical preparation and mounting of anesthetized mice with intact blood circulation.
- Attachment of the tongue to the µTongue device and positioning under a two-photon microscope.
- Intravital calcium imaging using GCaMP6f and tdTomato fluorescent reporters.
- Data acquisition and ratiometric analysis of taste cell responses.
Main Results
- Reliable imaging of taste cells in vivo with preserved neural and vascular connections.
- Visualization of autofluorescent filiform papillae, taste buds, and blood vessels.
- Functional calcium imaging revealed distinct taste cell responses to sweet, umami, and salt tastants.
- No response to sour tastants was observed in the representative example.
Conclusions
- The µTongue system enables robust, reproducible in vivo imaging of taste cell function.
- Controlled microfluidic delivery of tastants allows precise functional assays.
- This protocol supports advanced studies of taste cell physiology and intercellular communication in a natural context.
Frequently Asked Questions
What is the main advantage of the µTongue system for taste cell imaging?
The µTongue system allows functional imaging of taste cells in vivo under controlled, repeatable exposure to multiple tastants while maintaining physiological conditions.
How are tastants delivered to the tongue during imaging?
Tastants are delivered using a pressurized microfluidic perfusion system connected to the µTongue device, enabling precise timing and flow control.
What fluorescent reporters are used for imaging taste cell activity?
GCaMP6f (green) and tdTomato (red) are used for calcium imaging and ratiometric analysis of taste cell responses.
How is blood circulation monitored during the experiment?
TRITC-dextran is injected intravenously to visualize blood vessels and confirm intact circulation during imaging.
What types of taste responses can be detected with this protocol?
The protocol enables detection of taste cell responses to sweet, umami, and salt tastants; in the example, no response to sour was observed.
How is the mouse prepared for imaging?
The mouse is anesthetized, surgically prepared, and its tongue is attached to the µTongue device, ensuring stable positioning and moisture during imaging.
What troubleshooting tips are provided?
The protocol includes tips for maintaining steady fluid flow, preventing blood flow blockage, and keeping the tongue moist throughout the experiment.
Executive Industry Relevance
The µTongue platform enables functional imaging of taste cells in vivo with precise, microfluidic-controlled tastant delivery, preserving physiological context. This capability advances early discovery by allowing direct observation of sensory cell responses and cell-to-cell communication under native conditions. The approach supports predictive confidence in target validation and mechanistic de-risking for sensory biology and neurobiology portfolios.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables interrogation of taste cell function and pathway specificity in a native microenvironment.
- Supports biological de-risking by maintaining neural and vascular integrity during functional assays.
- Facilitates predictive confidence in sensory target validation through real-time, quantitative imaging.
Screening & Assay Development
- Prepares validated, physiologically relevant tissue systems for downstream compound screening.
- Delivers standardized, reproducible exposure to multiple tastants via microfluidic control.
- Generates quantitative, ratiometric imaging outputs for robust assay development.
Translational & Preclinical Research
- Aligns functional imaging outputs with disease-relevant sensory pathways when applicable.
- Provides continuity from discovery through preclinical validation by preserving in vivo context.
- Enables risk-adjusted advancement decisions based on direct functional readouts.
Pipeline & Workflow Integration
The µTongue system integrates at the interface of early discovery and assay development, bridging hypothesis-driven target validation with quantitative screening workflows.
- Discovery Biology: Supports hypothesis testing and mechanistic clarification of taste cell signaling in vivo.
- Screening: Provides assay-ready, reproducible tissue platforms with controlled stimulus delivery.
- Analytics: Enables quantitative measurement of calcium dynamics and ratiometric analysis for comparative studies.
- Translational Research: Maintains physiological relevance for preclinical continuity when sensory pathways are implicated.
- Enterprise Reuse: Establishes a reusable imaging and microfluidic platform for diverse sensory and neurobiological investigations.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in sensory target validation.
- Operational Value: Standardizes functional imaging and stimulus delivery for reproducibility and scalability.
- Strategic Value: Improves go/no-go decision quality and capital efficiency by enabling direct functional assessment.
- Portfolio Impact: Supports risk-adjusted prioritization and advancement of sensory and neurobiology programs.
Implementation Considerations
- Requires expertise in intravital imaging, microfluidics, and animal handling.
- Demands access to two-photon microscopy and precise fluidic control systems.
- Necessitates cross-team standardization for imaging protocols and data analysis.
- Adaptation may be needed for different animal models or sensory systems.
- Practical limitations include maintaining tissue viability and consistent fluid flow during extended imaging sessions.
Biopharma FAQs
Why does null hypothesis testing matter for taste cell response validation?
Null hypothesis testing enables objective assessment of whether observed taste cell responses to specific tastants are statistically significant, supporting rigorous target validation in sensory research pipelines.
How does independent variable isolation fit the microfluidic tastant delivery workflow?
Microfluidic control allows precise isolation and timed delivery of individual tastants, ensuring that observed cellular responses can be attributed to specific stimuli within the discovery workflow.
What do quantitative calcium imaging measurements enable in assay development?
Quantitative calcium imaging provides reproducible, ratiometric data on taste cell activation, enabling robust comparison of responses across conditions and supporting assay standardization.
Why are replication requirements critical for cross-functional imaging studies?
Replication ensures that functional imaging results are reproducible across experiments and teams, facilitating reliable data sharing and cross-functional collaboration in R&D environments.
What statistical analysis capabilities are required before implementing functional imaging outputs?
Statistical analysis must support ratiometric quantification, significance testing, and comparison of cellular responses to different tastants to enable actionable decision-making in biopharma pipelines.
