Piscidin
A family of fish antimicrobial peptides from mast cells — broad-spectrum, membrane-disrupting, with anticancer and aquaculture-immunity uses. Research compounds, not drugs
Piscidins are the signature antimicrobial peptides of fish. They were discovered in the mast cells — immune cells — of fish, and they now number many members across species (piscidin 1 through 7, and the well-studied tilapia piscidins TP1-TP4). Each is a short, linear, cationic peptide of roughly eighteen to twenty-six amino acids that folds into an amphipathic alpha-helix in a membrane, and many are unusually rich in the amino acid histidine near one end. Like other membrane-active peptides they bind and permeabilise microbial membranes, and they are broadly active against bacteria, fungi, viruses and parasites. Piscidins matter in two worlds at once: in aquaculture, where they are part of fish innate immunity and are studied as feed additives and disease-resistance tools, and in biomedical research, where tilapia piscidin 4 in particular is a promising anticancer peptide that selectively attacks cancer-cell membranes. Piscidins are research peptides; they are not approved medicines and have not been given to people as a treatment.
No established human dose Details ↓
Recommended Dosing
No established human dose
Piscidins are fish research peptides; none has been given to people as a treatment. The work is in bacteria, cultured cells and fish/animal models, often with engineered, encapsulated or gene-delivered forms, at experimental amounts that do not carry over to people.
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What is it?
Fish defend themselves against waterborne microbes with a rich set of innate-immune molecules, and piscidins are their best-known antimicrobial peptides. First reported in 2001 as peptide antibiotics in the mast cells of fish, they have since been found across many species and named in series — piscidin 1 to 7 in the original striped-bass work, and tilapia piscidins TP1 to TP4, among others. Each piscidin is a short, linear, cationic peptide that is largely disordered in water but folds into an amphipathic alpha-helix on contact with a membrane, and a characteristic histidine-rich stretch near the N-terminus makes some members sensitive to pH and able to bind metal ions.
Their central mechanism is membrane disruption: the positively charged helix binds the negatively charged surface of a microbial membrane, inserts, and permeabilises it. Biophysical work keeps refining this picture — a single change of one residue from its normal (L) to the mirror-image (D) form in a piscidin-2 variant created an N-terminal aromatic anchor that drove the peptide deeper into the lipid bilayer and raised its antibacterial activity, illustrating how finely structure controls function. Piscidins are broadly active against Gram-positive and Gram-negative bacteria, fungi, viruses and some parasites.
In aquaculture, piscidins are studied both as part of fish immunity and as practical tools. Dietary encapsulated piscidin 1 fed to gilthead seabream modulated the fish's immune responses and even affected flesh quality, and a probiotic Bacillus subtilis engineered to secrete tilapia piscidin-1 (with hepcidin) protected zebrafish against the fish pathogen Aeromonas hydrophila by cutting intestinal pathogen load and inflammation. A newly identified seabream piscidin (Gb-piscidin), which needs a disulfide bridge for activity, inhibited fish bacteria and tempered the inflammatory response to infection in trout. These point to piscidins as sustainable alternatives to antibiotics in fish farming.
Beyond fish, piscidins have become notable anticancer and biomaterial leads. Tilapia piscidin 4 (TP4) selectively permeabilises cancer-cell membranes, and biophysical studies tie that selectivity to its recognition of phosphatidylserine — an anionic lipid that cancer cells expose on their surface — and to its arginine-rich tail. Tilapia piscidin 3 (TP3) spontaneously self-assembles into an antimicrobial, biocompatible hydrogel that killed drug-resistant bacteria and fungi and reduced post-surgical adhesions in animals. These are laboratory and animal studies, not treatments given to people.
Through all of this, piscidins remain research peptides. No published study has given a piscidin to people as a treatment, none is approved anywhere, and material sold online under these names is an unregulated research chemical. Nothing here is a dose or a therapy; this page records what the published science says.
Mechanism of Action
Piscidins are short, linear, cationic, often histidine-rich fish antimicrobial peptides that fold into amphipathic alpha-helices and disrupt microbial membranes (broad-spectrum antibacterial, antifungal, antiviral). They contribute to fish innate immunity and are studied in aquaculture; some (tilapia piscidin 4) selectively kill cancer cells.
Fish mast-cell host defense
Short cationic amphipathic helices, often histidine-rich, from fish mast cells/granulocytes; members piscidin 1-7 and tilapia piscidins TP1-4 (PMIDs 41319890, 42912617).
Membrane disruption
Bind and permeabilise microbial membranes across bacteria, fungi, viruses and parasites; single-residue changes tune insertion depth and potency (PMIDs 42912617, 42134155).
Aquaculture immunity & anticancer
Part of fish innate immunity and studied as feed additives/disease-resistance tools; tilapia piscidin 4 selectively targets phosphatidylserine on cancer cells (PMIDs 42754065, 42063841).
Published Research
These are studies of piscidins read from their PubMed records on November 7, 2026: a biophysical structure-activity study of a piscidin-2 variant; two aquaculture studies (dietary piscidin 1 in seabream and a piscidin-secreting probiotic protecting zebrafish); a self-assembling tilapia piscidin-3 antimicrobial hydrogel with in-vivo anti-adhesion activity; the selective anticancer mechanism of tilapia piscidin 4; and a novel disulfide-bridged seabream piscidin with antimicrobial and immunostimulant activity. The evidence is in bacteria, cells and fish/animal models; piscidins have not been given to people as a treatment.
A single L-to-D change tunes how piscidin-2 disrupts membranes
Replacing one residue of a piscidin-2 variant with its mirror-image D-form kept the overall helical character but created an N-terminal aromatic anchor that buried the peptide more deeply in the lipid bilayer, increasing membrane tension, pore-forming kinetics and antibacterial activity — a biophysical structure-activity study (NMR and CD).
Dietary encapsulated piscidin 1 modulates immunity in seabream
Piscidin 1 encapsulated in microparticles and fed to gilthead seabream stayed structurally intact after oral delivery and modulated the fish's systemic immunity and gene expression along the gut-skin-brain axis, with effects on pigmentation and muscle texture — supporting its potential as a multifunctional aquaculture feed additive.
A piscidin-secreting probiotic protects zebrafish from a fish pathogen
A Bacillus subtilis probiotic engineered to secrete tilapia piscidin-1 (alone or fused with hepcidin) inhibited Aeromonas hydrophila; zebrafish fed the piscidin-hepcidin strain had the highest survival after infection, with lower intestinal pathogen load, less inflammation and better gut integrity — a preclinical aquaculture delivery strategy.
A self-assembling tilapia piscidin-3 antimicrobial hydrogel
Tilapia piscidin-3 (TP3) spontaneously self-assembled into a physically cross-linked hydrogel that was biocompatible, non-hemolytic and anti-inflammatory and had broad antimicrobial and antibiofilm activity against drug-resistant pathogens by a 'trap-and-kill' membrane mechanism; the gel reduced post-operative peritoneal adhesions in animals — a multifunctional biomaterial study.
Tilapia piscidin 4 selectively targets cancer-cell membranes
Tilapia piscidin 4 (TP4) permeabilised cancer-cell membranes more than normal-cell membranes, and biophysical studies tied this selectivity to its recognition of the anionic lipid phosphatidylserine (exposed on cancer cells) and to its arginine-rich tail, which drove binding and membrane disruption — a mechanism study framing TP4 as a selective anticancer peptide.
A novel disulfide-bridged seabream piscidin (Gb-piscidin)
A new piscidin from gilthead seabream (Gb-piscidin), a 22-residue peptide needing a disulfide bridge for activity, inhibited Gram-positive fish bacteria; in rainbow trout it reduced the pro-inflammatory response to infection while on its own inducing an immune signal — a dual antimicrobial and immunomodulatory role in fish.
No Established Human Dose
Piscidins are fish research peptides; none has been given to people as a treatment. The work is in bacteria, cultured cells and fish/animal models, often with engineered, encapsulated or gene-delivered forms, at experimental amounts that do not carry over to people. No regulator has approved any dose, and no published human dose exists, so no amount is printed here.
What this rests on: PMID 42912617, PMID 42063841, PMID 42754065.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Piscidin is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Piscidin has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Piscidin, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Piscidin stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Piscidin. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
How long it stays in the body: a half-life of not established for humans; short cationic peptides, variable stability. After about five half-lives almost none is left.
When effects appear: unknown; no source on this page gives a time to effect for Piscidin. Results reported in the studies are under Published Research.
Source: half-life: PMID 42754065.
Side effects, and when to stop or get help
From the Side Effects section: No human adverse-event data exist: no published study has administered a piscidin to people; As membrane-active peptides, hemolysis and cytotoxicity to host cells are the central safety concern; some piscidins and self-assembled forms are reported non-hemolytic in the lab (PMID 42134155) — a research finding, not human data; Tilapia piscidin 4 is cytotoxic to cancer cells by design (PMID 42063841); selectivity for tumour over healthy cells is an active research question; Material sold online as a 'piscidin' is an unregulated research chemical of unverified content. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Piscidin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“Piscidins are research peptides that have not been given to people as drugs, so there is no human safety profile; the points below reflect that research status and their biology”).
Interactions
Unknown: a PubMed search for human interaction studies of Piscidin (reviewed 2026-11-07) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Piscidin products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not drugs: Drugs@FDA and the openFDA label endpoint hold no record, and FDA GSRS and ChEMBL hold no approved-drug record for piscidin peptides (searched November 7, 2026)). Sport: Not on the 2026 List.
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
Piscidins are research peptides that have not been given to people as drugs, so there is no human safety profile; the points below reflect that research status and their biology.
Contraindications & Cautions
Piscidins have no approved use and no label. These points reflect their research status.
Legal Status
Piscidins are fish antimicrobial peptides used as research compounds; they are not drugs and are not approved in any country.
Frequently Asked Questions
?What are piscidins?
A family of antimicrobial peptides from the mast cells of fish, first described in 2001. They are short (~18-26 amino acid), cationic, often histidine-rich amphipathic helices; members include piscidin 1-7 and tilapia piscidins TP1-4 (PMID 42912617).
?How do they work?
They bind and disrupt microbial membranes, with broad-spectrum activity against bacteria, fungi, viruses and parasites; tilapia piscidin 4 also selectively targets cancer-cell membranes via the lipid phosphatidylserine (PMIDs 42134155, 42063841).
?What are they studied for?
As part of fish innate immunity and aquaculture tools (feed additives, disease resistance), as antimicrobial biomaterials, and as anticancer leads (tilapia piscidin 4) (PMIDs 42754065, 42063841).
?Are they approved or available to buy?
No. Piscidins are not medicines, have no FDA application or label, and are approved nowhere. Material sold online as a piscidin is an unregulated research chemical. Grey Peptides lists no sellers and recommends no source; this page records the published science.
References
- [mechanism] Souza KR, et al. "A Single L- to D-Substitution in Piscidin-2s Creates an N-Terminal Aromatic Anchor That Enhances Membrane Interaction and Antibacterial Activity." Biomacromolecules, 2026;27(10):6698-6714. PMID: 42912617.
- [animal] Marín-Parra C, et al. "Exploring the multifaceted effects of dietary encapsulated piscidin 1 on gilthead seabream (Sparus aurata): from immunomodulation to muscle quality." Fish Shellfish Immunol, 2026;179:111717. PMID: 42754065.
- [animal] Zhang KY, et al. "Engineered Bacillus subtilis secreting piscidin-1/hepcidin enhances resistance against Aeromonas hydrophila in a zebrafish model." Fish Shellfish Immunol, 2026;175:111447. PMID: 42176787.
- [animal] Selvaraj SP, et al. "Supramolecular self-assembly mechanisms, interfacial behavior, multimodal antimicrobial and anti-adhesion activities of the novel Tilapia piscidin-3 (TP3) peptide hydrogel." Colloids Surf B Biointerfaces, 2026;266:115806. PMID: 42134155.
- [mechanism] Makambi WK, et al. "Harnessing Membrane-Active Peptides for Selective Cancer Targeting: Phosphatidylserine Recognition by Tilapia Piscidin 4." JACS Au, 2026;6(4):2244-2263. PMID: 42063841.
- [animal] Berenjkar N, et al. "Gb-piscidin: A novel antimicrobial and immunostimulant peptide from gilthead seabream (Sparus aurata) - Identification, tissue-specific expression, recombinant production, and biological evaluation." Fish Shellfish Immunol, 2026;169:111049. PMID: 41319890.
- [other] Piscidins are antimicrobial peptides from the mast cells and granulocytes of fish, first described by Silphaduang and Noga (Nature, 2001), who reported peptide antibiotics in fish mast cells. Many members have since been found across fish species (piscidin 1-7, tilapia piscidins TP1-4); their structure and activities are described in the studies carded on this page (read November 7, 2026).
- [other] US FDA, Drugs@FDA and the openFDA label endpoint, searched November 7, 2026: no application and no label record for piscidin peptides. They are fish research antimicrobial/anticancer peptides, not drugs; FDA GSRS and ChEMBL hold no approved-drug record for them.
Sources & Citations
The six studies carded above were read from their PubMed records on November 7, 2026. The piscidin family's fish-mast-cell origin, its short histidine-rich amphipathic alpha-helical structure, its membrane-disrupting broad-spectrum mechanism, its aquaculture-immunity and biomaterial uses, and the selective anticancer activity of tilapia piscidin 4 are from the studies carded here; the discovery is Silphaduang & Noga (Nature, 2001). The absence of US approval or a drug record from Drugs@FDA, openFDA, FDA GSRS and ChEMBL was checked the same day. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.