A Simple and Precise Feed-Based Approach to Oral Drug Delivery in Fish
May 22nd, 2026
This study presents a gelatin-based feeding method that enables precise, non-invasive, body mass–based oral drug delivery in adult zebrafish. The protocol demonstrates reliable feed acceptance and, as a proof-of-principle, successful delivery of MK-801, which resulted in the expected behavioral effects.
This study describes a method for precise and non-invasive drug delivery to adult zebrafish. Unlike stressful, invasive, or imprecise traditional methods, this protocol enables non-invasive and precise drug delivery to adult zebrafish. To begin, fill 100 milliliter glass beaker with 50 milliliters of system water.
Place it on a digital scale and tare the scale to subtract the beaker weight, and reset the scale to zero. Use a fine mesh net to gently remove a single fish from their home tank. Remove excess water by briefly touching the net to a dry paper towel.
And place the fish carefully into the beaker without spilling water onto the scale. Record the weight and calculate the required feed volume as 1%volume per body weight for each individual fish. Add pre-weighed brine shrimp powder to 50 milliliters of distilled water while stirring to achieve a final concentration of 250 milligrams per milliliter.
Stir for one hour. Centrifuge the suspension at 12, 500 G for 10 minutes at room temperature. And collect the supernatant.
Centrifuge the liquid again to remove any remnant suspended debris, and collect the supernatant. Store at minus 20 degrees Celsius for up to six months. To prepare the gelatin-based feed, thaw the brine shrimp extract and calculate the approximate volume required for 500 microliters of the feed.
Calculate the required amounts of the components, then measure and add the appropriate amounts of the drug compound, spirulina, water, and brine shrimp extract into a 1.5 milliliter micro-centrifuge tube. Vortex thoroughly to homogenize. Transfer the required volume of the mixture to the gelatin containing tube to obtain a final gelatin concentration of 12%weight per volume.
Place the tube on a pre-warmed 45 degree Celsius heating block for five minutes. Vortex intermittently until the gelatin is completely dissolved. If necessary, gently stir with a sterile wood or metal stick to aid homogenization.
Aliquot 100 microliters of the homogenized mixture into labeled 1.5 milliliter micro-centrifuge tubes and solidify at minus 20 degree Celsius overnight. Align a flat sheet of paraffin film in a Petri dish, reheat and vortex the prepared gelatin feed. And pipette the volume corresponding to 1%of the fish's body mass onto the paraffin film to form individual morsels.
Solidify the morsels by placing the Petri dish at minus 20 degree Celsius for at least 20 minutes and keep on ice until feeding. Transfer fish from the housing rack to the behavior room to acclimatize for one hour. Use transparent barriers to temporarily isolate each fish in the tank for two to five minutes prior to feeding.
Use forceps to pick up the feed from parafilm and place an individual gelatin morsel onto the water surface for each fish. Observe each fish for five minutes to confirm consumption of the entire morsel. Remove the barriers after feed consumption, then return the fish to their home racks or use them for experimental procedures.
When adult AB and TL zebrafish were given gelatin feed for five mornings instead of their usual meal, all TL zebra fish consumed the morsels within five minutes on the first day. Whereas AB fish required four days of acclamation to reach a consistent consumption rate for 15 out of 16 individuals. TL fish of both sexes consumed the feed rapidly from the first exposure within four to 20 seconds, whereas AB fish showed longer initial consumption times ranging between seven to 144 seconds.
But improved to under 30 seconds over repeated days. Following two days of acclimation to gelatin morsels, male and female adult AB fish were divided into control and treatment groups, then fed with vehicle or MK-801 containing morsels. Behavior was analyzed as distance from the bottom in a novel tank test.
And both male and female drug-treated fish spent more time near the top of the tank compared to control indicating, reduced anxiety-like, or predator avoidance behavior. This protocol enables precise drug dosing and allow measurement of behavioral, pharmacological, and physiological responses in adult zebra fish. The key challenges are feed homogenization, setting, and confirming consumption by each fish.
Future work will extend this method for other compounds, different dosing regimens, and other aquatic model organisms.
Overview
This article presents a gelatin-based feeding method for precise, rapid, and minimally stressful drug delivery in fish models. The approach addresses limitations of traditional methods, enabling accurate dosing and reducing animal stress, which is particularly beneficial for behavioral pharmacology and long-term studies.
Key Study Components
Area of Science
- Behavioral pharmacology
- Biomedical research using aquatic models
- Drug delivery methods
Background
- Traditional drug delivery in fish (beaker dosing, injections, oral gavage) is time-consuming and imprecise.
- These methods can be stressful for animals, limiting their use in repeated or sensitive behavioral experiments.
- Stress and handling confounds can affect behavioral outcomes.
- There is a need for improved drug administration techniques in fish research.
Purpose of Study
- To develop a rapid, precise, and minimally disturbing drug delivery method for fish.
- To enable individualized dosing based on body mass.
- To facilitate behavioral experiments with reduced handling stress.
Methods Used
- Preparation of gelatin-based feed morsels containing brine shrimp extract, spirulina, and the drug of choice.
- Liquefaction and homogenization of the mixture for accurate portioning.
- Customization of feed morsel size according to individual fish body mass.
- Re-solidification of portions for easy administration.
Main Results
- Successful administration of the NMDA receptor antagonist MK-801 (4 mg/kg) to adult zebrafish.
- Observed behavioral effects in the novel tank test consistent with reduced anxiety-like behavior.
- Demonstrated feasibility and precision of the gelatin-based feeding method.
- Minimized animal disturbance during drug delivery.
Conclusions
- The gelatin-based feeding method enables precise, individualized drug dosing in fish.
- This approach reduces stress and is suitable for repeated or long-term studies.
- The method is adaptable to other aquatic model organisms and behavioral pharmacology research.