The Stimulus Preference Chip allows you to perform highly quantitative chemotaxis and odortaxis phenotypic assays with precise microfluidic control by restraining a worm with minimal immobilization so the worm can freely behave. The worm can choose between two separate stimulus streams with different chemicals, foods, odors, or temperatures.
How does the Stimulus Preference Chip work?
The nematode is held in place by a restraint that aligns the longitudinal axis of the body with the border between two laminar fluid streams, leaving the animal’s head and tail free to move. The content of the fluid streams can be manipulated to deliver step gradients in space or time. The Stimulus Preference Chip can be used as a stand-alone product.
Key Advantages of Stimulus Preference Chips:
- Easily see worm’s preference for chemicals, foods, odors and temperatures
- Expose worm to two different micro-environments at the same time
- Highly detailed, quantifiable behavior1 (Fig. 1)
Figure 1. Behavioral responses to step gradients in chemoattractant concentration. Mean head angle of wild type animals and tax-4 mutants by stimulus epoch. Error bars are s.e.m. Click HERE for more data.
|Stimulus Preference Chip Starter Kit (incl. all you need to start using the chip)||1||SPCK17||$200.00|
|Stimulus Preference Chip||1||SPC17||$50.00|
Video: Setting up the Stimulus Preference Chip
To operate the stimulus preference chip, you will need:
- 4 10mL fluid-reservoir syringes with one-way stopcock and 20G needle stubs
- 6 ~25cm tubing PE/9 polyethylene tubing with 1.5mm OD SS tube
- 1 5mL syringe with 17G blunt needle stub
- 1 PE/6 polyethylene tubing
- 7 pieces of tubing
- 1 stereomicroscope
- 2 vacuum sources
See Stimulus preference chip user guide for more information about the set-up.
Watch the video below. See Stimulus preference chip user guide for more information.
Video: Setting up the Stimulus Preference Chip
The stimulus preference chip is designed to accommodate first-day adults
The chip can deliver any water soluble compound as a stimulus in any of the four inputs. The chip can be operated in spatial or temporal modes. In the spatial mode, the solutions in the left and right channels are different. For example, the left and right solutions could be NaCl at different concentrations, yielding a step-wise concentration gradient. Or, the left and right solutions could contain the same concentration of NaCl and KCl, respectively, to measure the worm’s preference for Na+ and K+ ions. In the temporal mode, the worm experiences a sudden shift between two stimuli that are each delivered symmetrically. For example, the left and right channels could first contain a solution low in NaCl that is then switched to a solution high in NaCl to measure the worm’s response dynamics.
If solutions are well filtered to prevent the chip from clogging (e.g., 0.2 um for bacteria-free solutions), there is essentially no limit on the number of worms that can be tested in a single experimental session (e.g. one day in the lab). The chip can often be reused on subsequent days if it is cleaned and dried according to standard procedures described in the User’s Guide. This procedure works best when inorganic compounds are used as stimuli. In the case of organic odorants, there is the concern that these are retained by the chip to an unknown degree after cleaning. In this case, it is safest to use a new chip between daily sessions. A similar concern exists when bacteria are used as stimulants.
It takes about 5 min to load the chip with testing fluids at the start of an experiment. It takes about the same amount of time to wash and load a worm.
We recommend viewing the chip on a stereomicroscope. Taping the chip to the microscope stage is necessary to keep it from moving as the stopcocks are adjusted, worms are inserted and removed.
We recommend loading one worm at a time into the chip for more consistent behavioral results. There could be progressive changes in metabolic state as worms in the chip wait for their turn to perform.
The main difference is that worms are washed in bulk for the ScreenChip, but individually for the Preference Chip.
The chip is designed primarily for the collection of behavioral data in several forms. These include the percentage of time the worm’s head resides on the left or the right side of the chip, and mean head angle in the chip (measured with respect to the worm longitudinal axis of the body in the worm clamp).
Video recordings of worm behavior (30 frames/sec) can be analyzed in MATLAB using a custom routine to compute head angle θ in each image.
- Mask and threshold the frames to obtain an image of the worm.
- Use a skeletonization procedure obtain the centerline of the worm
- Starting at the position of the restraint, traverse the centerline to find the tip of the head, defined as the point furthest from the restraint.
- Initiation of reversals can be scored manually by an observer who was blind to experimental condition. Reversal behavior is defined as the propagation of the undulatory wave in the posterior to anterior direction
You can keep the worm trapped in place for up to 20 min.
Yes, worms can be readily flushed out of the chip and recovered at the end of each experiment.
Stimulus Preference Chip FAQs
ScreenChip system compatibility
Not at this time.
No. The two systems are independent.
No. Only the ScreenChip has a case.
User Guides & Documentation
- McCormick, K. E., Gaertner, B. E., Sottile, M., Phillips, P. C., & Lockery, S. R. (2011). Microfluidic Devices for Analysis of Spatial Orientation Behaviors in Semi-Restrained Caenorhabditis elegans. PLoS ONE, 6(10), e25710. http://doi.org/10.1371/journal.pone.0025710
Download the paper
- Composition: PDMS on glass
- Channel Height: 60 µm
- Size: 1" x 3" glass slide.
- Stage: For first day adult C. elegans.