LL-37
LL-37 (also known as CAP-18) is a 37-amino-acid cationic antimicrobial peptide derived from the C-terminal of human cathelicidin (hCAP18)[1]. It is the only known human cathelicidin, exhibiting broad-spectrum antibacterial activity and immune-modulating properties[2][3]. This educational protocol presents a once-daily subcutaneous approach using a practical dilution for clear insulin-syringe measurements.
Reconstitution Steps
Draw 3.0 mL bacteriostatic water with a sterile syringe.
Inject slowly down the vial wall; avoid foaming.
Gently swirl/roll until dissolved (do not shake).
Label and refrigerate at 2–8 °C (35.6–46.4 °F), protected from light.
Protocol Overview
Concise summary of the once‑weekly regimen.
Goal: Support antimicrobial defense and wound-healing processes[4][5].
Schedule: Daily subcutaneous injections for 8–12 weeks (extend to 16 weeks if desired).
Dose Range: 50–400 µg daily with gradual titration.
Reconstitution: 3.0 mL per 5 mg vial (~1.67 mg/mL) for accurate unit measurements.
Storage: Lyophilized frozen; reconstituted refrigerated; avoid repeated freeze–thaw.
Dosing Protocol
Suggested daily titration approach reflecting clinical study parameters.
Start: 50–100 µg daily; increase by ~50 µg each week as tolerated.
Target: 200–400 µg daily by Weeks 4–8.
Frequency: Once per day (subcutaneous); optional 5-on/2-off schedule.
Cycle Length: 8–12 weeks; optional extension to 16 weeks.
Timing: Any consistent time; rotate injection sites.
Storage Instructions
Proper storage preserves peptide quality.
Lyophilized: Store at −20 °C (−4 °F) in dry, dark conditions; stable ~24 months.
Reconstituted: Refrigerate at 2–8 °C (35.6–46.4 °F) for up to 4 weeks; frozen at −20 °C (−4 °F) for up to 6 months.
Allow vials to reach room temperature before opening to reduce condensation uptake.
Important Notes
Practical considerations for consistency and safety.
Use new sterile insulin syringes; dispose in a sharps container[8].
Rotate injection sites (abdomen, thighs, upper arms) to reduce local irritation[9].
Inject slowly; wait a few seconds before withdrawing the needle.
Document daily dose and site rotation to maintain consistency.
Early-phase doses (≤10 units) benefit from 30- or 50-unit syringes for precision.
How This Works
LL-37 exerts both direct and indirect antimicrobial effects. Its amphipathic, cationic α-helical structure (net +6 charge) allows it to preferentially bind and disrupt negatively charged microbial membranes[2]. Beyond direct killing, LL-37 modulates host immunity: in murine sepsis models, it induced neutrophils to release microvesicles rich in antimicrobial proteins, lowering bacterial burden and improving survival[3]. LL-37 can also bind bacterial lipopolysaccharide (LPS) and block its interaction with CD14/TLR4, reducing endotoxin-triggered TNF release and neutrophil apoptosis[2]. These combined mechanisms help explain its potential in infection control and tissue-repair contexts.
Potential Benefits
In chronic venous leg ulcers (which often lack endogenous LL-37), topical treatment with synthetic LL-37 significantly accelerated healing rates compared to placebo[4].
In diabetic foot ulcer trials, LL-37 cream improved granulation tissue formation and wound closure[5].
Broad-spectrum antimicrobial action helps clear infections; in experimental sepsis models, LL-37 treatment reduced bacterial loads and mortality[3].
Generally well tolerated; occasional mild injection-site reactions (redness, itch) may occur with subcutaneous administration.
Lifestyle Factors
Complementary strategies that may support therapeutic goals.
Optimize vitamin D status, as vitamin D upregulates endogenous cathelicidin/LL-37 expression[10].
Support wound healing with adequate protein intake and micronutrient sufficiency (zinc, vitamin C).
Maintain proper wound hygiene and dressing protocols if using for tissue-repair goals.
Prioritize sleep and stress management to support immune function and recovery.
