An Integrated Microfluidic and Fluorescence Platform for Probing In Vivo Neuropharmacology

Neurology Bioengineering Life Sciences Medicine
microfluidics fluorescence neuropharmacology in vivo neurotransmitters drug delivery calcium indicators

Academic Background

Neuroscience research has made significant progress over the past decade, particularly in the development of neurotechnologies and genetic tools for dissecting neural circuit functions. However, the advancement of neuropharmacological methodologies has lagged in comparison. Understanding the precise pharmacological mechanisms of neuroactive compounds is critical for advancing basic neurobiology and neuropharmacology, as well as for developing more effective treatments for neurological and psychiatric disorders. Yet, integrating modern tools for assessing neural activity in large-scale neural networks with spatially localized drug delivery remains a major challenge. To address this issue, researchers have developed a dual-function platform combining microfluidic and fluorescence technologies, enabling simultaneous intracranial drug delivery and neural dynamics recording in the mouse brain.

Source of the Paper

This paper was co-authored by Sean C. Piantadosi, Min-Kyu Lee, Mingzheng Wu, and others, affiliated with institutions such as the University of Washington, Northwestern University, and Neurolux Inc. The paper was published on May 21, 2025, in the journal Neuron, under the title An Integrated Microfluidic and Fluorescence Platform for Probing In Vivo Neuropharmacology.

Research Process

1. Device Design and Fabrication

The researchers designed and fabricated a device integrating microfluidic and fluorescence technologies. The device includes a wireless, battery-free miniaturized fluidic system and an optical probe, enabling spatially and temporally restricted drug delivery while recording neural activity-dependent fluorescence signals using genetically encoded calcium indicators (GECIs), neurotransmitter sensors, and neuropeptide sensors. The core of the device is a microfluidic module weighing less than 0.15 grams and measuring 10×13 mm, wirelessly powered via magnetic inductive coupling at 13.56 MHz.

2. Integration of Microfluidic System and Optical Probe

The microfluidic system consists of two micropumps, each connected to an independent microchannel embedded in a soft polydimethylsiloxane (PDMS) probe. The probe is integrated with an optical fiber, allowing real-time recording of neural activity changes following drug delivery. The fluidic outlets are positioned at the bottom of the probe, ensuring even drug distribution beneath the optical fiber. Additionally, the device can be configured with multiple optical fibers, each connected to separate drug reservoirs, enabling drug and light stimulation in different brain regions.

3. Experimental Validation of Drug Delivery and Fluorescence Detection

In vitro experiments, researchers used a 0.6% agarose gel to simulate brain tissue, validating the device’s drug delivery and fluorescence detection capabilities. The results showed that drug diffusion beneath the probe was completed in approximately 25 seconds, with an average drug delivery flow rate of 1.5 µL/min. Subsequently, the device was implanted in the secondary motor cortex (M2) of anesthetized mice to validate its in vivo drug delivery and fluorescence detection capabilities. The results demonstrated that fluorescein isothiocyanate (FITC) delivery significantly increased fluorescence signals, while artificial cerebrospinal fluid (ACSF) showed no significant change.

4. Bidirectional Modulation of Behavior and Neural Activity

In awake mice, researchers used the device for drug delivery and neural activity recording. Experiments showed that delivery of the AMPA receptor agonist AMPA significantly increased calcium signals in M2 neurons and induced rotational behavior in mice. Subsequently, delivery of the GABAA receptor agonist Muscimol rapidly reduced M2 neuronal activity and normalized behavior. These results demonstrated that the device could achieve bidirectional modulation of neural activity and behavior through drug delivery in a single animal.

5. Combining Photostimulation with Neurotransmitter Sensing

Researchers further combined the device with photostimulation technology to validate its application in neurotransmitter sensing. Experiments showed that in the noradrenergic system, photostimulation significantly increased fluorescence signals of the GrabNE2m sensor, while delivery of the α2-adrenergic receptor antagonist Yohimbine inhibited this effect. These results demonstrated that the device could integrate local pharmacology, projection-specific photostimulation, and neurotransmitter sensing, providing a new tool for studying the endogenous functions of neurotransmitter systems.

6. Investigating Interactions Between Neuromodulatory Systems

Finally, researchers used the device to study the interaction between the dopamine (DA) and κ-opioid receptor (KOR) systems in the nucleus accumbens (NAc). Experiments showed that DA delivery significantly increased fluorescence signals of the GrabDA3m sensor while reducing fluorescence signals of the Klight1.3b sensor. These results indicated that increased DA concentration could reduce dynorphin release, revealing dynamic interactions between the DA and KOR systems.

Key Findings

  1. Device Design and Fabrication: Successfully developed a wireless, battery-free microfluidic-fluorescence device capable of spatially and temporally restricted drug delivery while recording neural activity-dependent fluorescence signals.
  2. Drug Delivery and Fluorescence Detection: In vitro and in vivo experiments validated the device’s drug delivery and fluorescence detection capabilities, with drug diffusion beneath the probe completed in approximately 25 seconds.
  3. Bidirectional Modulation of Behavior and Neural Activity: Delivery of AMPA and Muscimol significantly modulated M2 neuronal activity and mouse behavior.
  4. Combining Photostimulation with Neurotransmitter Sensing: Photostimulation significantly increased fluorescence signals of the GrabNE2m sensor, while Yohimbine delivery inhibited this effect.
  5. Interactions Between Neuromodulatory Systems: DA delivery significantly increased fluorescence signals of the GrabDA3m sensor while reducing fluorescence signals of the Klight1.3b sensor, revealing dynamic interactions between the DA and KOR systems.

Conclusion

This study developed a device integrating microfluidic and fluorescence technologies, enabling spatially and temporally restricted drug delivery while recording neural activity-dependent fluorescence signals. The device can integrate local pharmacology, projection-specific photostimulation, and neurotransmitter sensing, providing a new tool for studying the endogenous functions of neurotransmitter systems. Additionally, the device revealed dynamic interactions between neuromodulatory systems, offering new perspectives for neuropharmacological research.

Research Highlights

  1. Innovative Device Design: Developed a wireless, battery-free microfluidic-fluorescence device capable of spatially and temporally restricted drug delivery while recording neural activity-dependent fluorescence signals.
  2. Multifunctional Experimental Platform: The device integrates local pharmacology, projection-specific photostimulation, and neurotransmitter sensing, providing a new tool for studying the endogenous functions of neurotransmitter systems.
  3. Investigating Interactions Between Neuromodulatory Systems: Revealed dynamic interactions between the DA and KOR systems, offering new perspectives for neuropharmacological research.

Research Value

The device developed in this study provides a new tool for neuropharmacological research, enabling the integration of local pharmacology, projection-specific photostimulation, and neurotransmitter sensing to reveal the endogenous functions of neurotransmitter systems. Additionally, the device can uncover dynamic interactions between neuromodulatory systems, offering new perspectives for neuropharmacological research. This study holds significant scientific and application value and is expected to advance the field of neuropharmacology.