LL-37

Volume Pricing

Price per pack (10 vials). Discount applies to this compound only – no mix and match.

LL-37 — Human Cathelicidin Antimicrobial Peptide | Innate Immune Defense & Immunomodulator

LL-37 is the sole member of the human cathelicidin family — a 37-amino acid cationic, amphipathic peptide derived from the C-terminal domain of the precursor protein hCAP18, encoded by the CAMP gene. It is released from neutrophils, macrophages, keratinocytes, and epithelial cells in response to infection or tissue injury, and represents the first-line peptide defense of the human innate immune system. Unlike conventional antimicrobials that act through a single enzymatic mechanism, LL-37 is fundamentally pleiotropic: it disrupts bacterial membranes through direct physical pore formation, neutralizes bacterial endotoxins (LPS and LTA), recruits and activates immune cells, promotes angiogenesis, accelerates wound re-epithelialization, and modulates both pro- and anti-inflammatory signaling — all through a compact helical structure of 37 amino acids with a net positive charge of +6.

Why LL-37’s Multi-Receptor Profile Defines Its Research Utility

LL-37’s defining feature as a research tool is its capacity to engage an unusually broad range of cellular targets from a single endogenous molecule. Most antimicrobial agents act on pathogens alone; LL-37 simultaneously acts on pathogens, immune cells, epithelial cells, endothelial cells, and connective tissue — making it a uniquely powerful probe for studying the intersection of innate immunity, inflammation, and tissue regeneration.

Its cationic amphipathic α-helical structure allows it to electrostatically target negatively charged bacterial membrane components (LPS in Gram-negatives; lipoteichoic acids in Gram-positives), insert into the lipid bilayer, and form oligomeric pores that disrupt membrane integrity and cause rapid bacterial cell death — a mechanism that remains effective against multidrug-resistant strains including MRSA, VRE, and resistant Klebsiella due to its physical, non-receptor-mediated mechanism of action.

Beyond direct antimicrobial killing, LL-37 engages host-cell receptors driving immunomodulatory and regenerative cascades:

This breadth of receptor engagement — across both pathogen-directed and host-directed pathways — distinguishes LL-37 from any single-mechanism antimicrobial or anti-inflammatory compound, and is why it has entered clinical trials for chronic wound healing, diabetic ulcers, and intratumoral injection in melanoma.

Research Applications

LL-37 is used in studies examining:

• Broad-spectrum antimicrobial activity against Gram-positive bacteria (MRSA, S. aureus, S. epidermidis), Gram-negative bacteria (E. coli, P. aeruginosa, Klebsiella), fungi (Candida spp.), and enveloped viruses (influenza, herpes simplex)
• Biofilm disruption and anti-biofilm mechanisms — particularly relevant to chronic wound and implant infection models
• Mechanism and kinetics of amphipathic α-helical pore formation in bacterial membrane systems
• Innate immune cell recruitment, neutrophil and monocyte chemotaxis via FPR2/FPRL-1
• IL-1β processing and secretion through P2X7 receptor activation in macrophage and monocyte models
• Wound healing — keratinocyte migration, angiogenesis, granulation tissue formation, and re-epithelialization
• Topical wound healing in venous leg ulcer and diabetic foot ulcer models (clinical data at 0.5–1.6 mg/mL topical concentrations)
• LPS neutralization and endotoxin sequestration in sepsis and systemic inflammation models
• Vitamin D–mediated upregulation of CAMP gene expression and cathelicidin production
• Psoriasis and autoimmune pathogenesis — LL-37/self-DNA complex formation and pDC-mediated IFN-α/β amplification
• Oncology-adjacent research — pro-apoptotic effects in certain cancer cell lines; intratumoral injection models for melanoma (Phase I clinical data)
• Gut epithelial repair in IBD-adjacent models; often stacked with BPC-157 in combined tissue-repair research designs

Specifications

Reconstitution

LL-37 arrives as lyophilized powder and is reconstituted with bacteriostatic water prior to use. Add bacteriostatic water slowly by directing the stream against the inside wall of the vial — do not inject directly onto the peptide cake. Gently swirl to dissolve; do not shake. LL-37’s amphipathic helical structure can self-associate at higher concentrations, so gentle handling during reconstitution preserves monomeric/active fractions.

Total mg ÷ Volume added (mL) = Concentration (mg/mL)

Example: 5mg + 3mL BAC water = 1.67mg/mL — each 0.1mL = 167mcg Example: 5mg + 2.5mL BAC water = 2mg/mL — each 0.1mL = 200mcg Example: 5mg + 5mL BAC water = 1mg/mL — each 0.1mL = 100mcg

Reconstituted LL-37 should be stored at 2–8°C and used within 28–30 days. The lyophilized peptide is stable for 2+ years when kept at or below 2–8°C, away from light and moisture.

Protocol Notes

LL-37 research is conducted via subcutaneous injection in systemic immune and tissue-repair models, or topically in wound healing studies. Unlike long-half-life growth factors, LL-37’s effects are partially immediate (membrane disruption, immune cell recruitment) and partially sustained (angiogenesis, re-epithelialization), so injection frequency varies by research endpoint. Cycling is not required for receptor desensitization reasons, but study durations are typically endpoint-specific.

Typical research dosing framework:

• Starting dose: 100mcg per administration
• Escalation: Increase by 50mcg every 1–2 weeks based on tolerance and experimental parameters
• Target range: 100–250mcg per administration (conservative); up to 400mcg in advanced protocols
• Frequency: Once daily SC, or 3–5×/week depending on study design
• Cycle length: 4–12 weeks depending on endpoint — wound healing studies commonly run 4–6 weeks; immune-focused studies extend to 8–12 weeks
• Topical reference dose: Clinical trial data supports 0.5–1.6 mg/mL applied twice weekly for wound healing endpoints

Commonly observed effects in research models:

• Immune: Rapid neutrophil and monocyte recruitment at injection/application site; enhanced pathogen clearance; IL-1β upregulation in macrophage models
• Tissue repair: Accelerated keratinocyte migration; increased granulation tissue and vascular density in wound models; collagen remodeling support
• Injection site: Transient local redness, warmth, or mild burning sensation — a direct consequence of FPR2-mediated immune cell recruitment and is expected, not pathological; rotate injection sites systematically
• High-dose caution: Doses above ~300–400mcg/day in research models can produce non-selective cytotoxicity in host fibroblasts and epithelial cells due to the same membrane-disrupting mechanism that kills bacteria; conservative titration is the standard approach
• Autoimmunity context: LL-37/nucleic acid complexes at sustained elevated levels can amplify TLR9/pDC activation — relevant consideration in models involving pre-existing autoimmune signaling backgrounds

Research Stacks

LL-37 is commonly paired in research settings with:

• KPV — KPV suppresses NF-κB signaling downstream of MC1R activation; pairing with LL-37’s TLR4/TLR9 modulatory activity is studied to assess whether simultaneous receptor-level and pathway-level anti-inflammatory intervention produces additive resolution of inflammatory signaling in epithelial and immune cell models.
• Thymosin Alpha-1 — Thymosin Alpha-1 drives TLR-mediated innate immune priming and dendritic cell maturation; co-administration with LL-37 is studied to probe synergies between endogenous host-defense peptide activity and systemic immune regulation in infection and barrier-disruption models.
• BPC-157 — BPC-157’s angiogenic and mucosal repair activity is studied alongside LL-37 in wound and tissue models where both antimicrobial peptide defense and structural repair are relevant endpoints, given their non-overlapping primary mechanisms.

Purity Guarantee

Every batch is ≥99% purity. If you independently test your compound and the results don’t match — send us the COA and we’ll issue store credit, no questions asked.