7- A Microfluidic Device for Partial Immobilization, Chemical Exposure and Behavioural Screening of Zebrafish Larvae
The zebrafish larva is an important vertebrate model for sensory–motor integration studies, genetic screening, and drug discovery because of its excellent characteristics such as optical transparency, genetic manipulability, and genetic similarity to humans. Operations such as precise manipulation of zebrafish larvae, controlled exposure to chemicals, and behavioural monitoring are of utmost importance to the abovementioned studies. In this work, a novel microfluidic device is presented to easily stabilize an individual larva’s head using a microfluidic trap while leaving the majority of the body and the tail unhindered to move freely in a downstream chamber. The device is equipped with a microvalve to prevent the larva’s escape from the trap and a microchannel beside the larva’s head to expose it to chemicals at desired concentrations and times, while investigating multiple behaviours such as the tail, eye, and mouth movement frequencies.
6- Characterization of Microfluidic Clamps for Immobilizing and Imaging of Drosophila melanogaster Larva’s Central Nervous System
Drosophila melanogaster is a well-established model organism to understand biological processes and study human diseases at the molecular-genetic level. The central nervous system (CNS) of Drosophila larvae is widely used as a model to study neuron development and network formation. This has been achieved by using various genetic manipulation tools such as microinjection to knock down certain genes or over-express proteins for visualizing the cellular activities. However, visualization of an intact-live neuronal response in larva’s Central Nervous System (CNS) is challenging due to robust digging/burrowing behaviour that impedes neuroimaging. To address this problem, dissection is used to isolate and immobilize the CNS from the rest of the body. In order to obtain a true physiological response from the Drosophila CNS, it is important to avoid dissection, while the larva should be kept immobilized. In this paper, a series of microfluidic clamps were investigated for intact immobilization of the larva.
5- Microfluidic Approaches for Manipulating, Imaging, and Screening C. elegans
The nematode C. elegans (worm) is a small invertebrate animal widely used in studies related to fundamental biological processes, disease modelling, and drug discovery. Due to their small size and transparent body, these worms are highly suitable for experimental manipulations. In recent years several microfluidic devices and platforms have been developed to accelerate worm handling, phenotypic studies and screens. Here we review major tools and briefly discuss their usage in C. elegans research.
4- A hybrid microfluidic device for on-demand orientation and multidirectional imaging of C. elegans organs and neurons
C. elegans is a well-known model organism in biology and neuroscience with a simple cellular (959 cells) and nervous (302 neurons) system and a relatively homologous (40%) genome to humans. Lateral and longitudinal manipulation of C. elegans to a favorable orientation is important in many applications such as neural and cellular imaging, laser ablation, microinjection, and electrophysiology. In this paper, we describe a micro-electro-fluidic device for on-demand manipulation of C. elegans and demonstrate its application in imaging of organs and neurons that cannot be visualized efficiently under natural orientation. To achieve this, we have used the electrotaxis technique to longitudinally orient the worm in a microchannel and then insert it into an orientation and imaging channel in which we integrated a rotatable glass capillary for orientation of the worm in any desired direction.
3- Cardiac screening of intact Drosophila melanogaster larvae under exposure to aqueous and gaseous toxins in a microfluidic device
Drosophila melanogaster is one of the promising model organisms for investigation of human diseases such as cardiac disorders. However, intact (not dissected) Drosophila larvae have not been extensively used as models in cardiac toxicity assays due to many challenges associated with assessment of their heart activities in the intact mode (i.e., heartrate monitoring of alive larva under exposure to aqueous and gaseous reagents). These challenges include the need for precise spatiotemporal control of stimulus exposure to posterior spiracles (i.e., breathing valves) and full immobilization of larvae in favorable orientations to monitor the heart under a microscope. In this paper, we not only present a novel microfluidic device that is capable of loading, orientating and immobilizing the larva reversibly in a chip, but also demonstrate for the first time the transient effects of toxic liquids (e.g., sodium azide) and gases (e.g., oxygen and carbon dioxide) at various concentrations on the heart of intact Drosophila larvae.
2- An integrated hybrid microfluidic device for oviposition-based chemical screening of adult Drosophila melanogaster
Chemical screening using Drosophila melanogaster (the fruit fly) is used in drug discovery, agricultural, and toxicological applications. Oviposition (egg laying) on chemically-doped agar plates is an important read-out metric used to quantitatively assess the biological fitness and behavioral responses of Drosophila. In this paper, we have developed a novel hybrid agar-polydimethylsiloxane (PDMS) microfluidic device for single- and multi-concentration chemical dosing and on-chip oviposition screening of free-flying adult stage Drosophila. To achieve this, we have devised a novel technique to integrate agar with PDMS channels using ice as a sacrificial layer. Subsequently, we have conducted single-chemical toxicity and multiple choice chemical preference assays on adult Drosophila melanogaster using zinc and acetic acid at various concentrations.
1- Agar-polydimethylsiloxane devices for quantitative investigation of oviposition behaviour of adult Drosophila melanogaster
Drosophila melanogaster (fruit fly) is a model organism and its behaviors including oviposition (egg-laying) have been widely used for assessment of a variety of biological processes in flies. Physical and chemical properties of the substrate are the dominant factors affecting Drosophila’s oviposition. In this paper, we have devised a simple, easily implementable, and novel methodology that allows for modification of physical and chemical composition of agar substrates in order to quantitatively study survival and oviposition of adult fruit flies in an accurate and repeatable manner. The technique is also useful for development of novel assays for learning and decision-making studies as well as miniaturized devices for self-assembly of eggs and embryonic developmental investigations.