GHK-Cu2+ Zn-pectinate microparticles achieve 6-hour lag time for colonic IBD delivery
Background
Inflammatory bowel disease (IBD) is characterised by mucosal ulceration and chronic inflammation driven in part by dysregulated matrix metalloproteinase (MMP) activity and insufficient levels of tissue inhibitors of metalloproteinases (TIMPs). Current oral drug delivery systems struggle to protect peptide therapeutics from upper-GI degradation and release them precisely at the colon. GHK-Cu2+ (glycyl-L-histidyl-L-lysine-Cu(II)) is a tripeptide-copper complex studied for its ability to inhibit MMP activity while increasing TIMP secretion, making it a candidate for local colonic therapy. Delivering GHK-Cu2+ intact to the colon requires a formulation strategy that creates a meaningful lag time, resists premature release in gastric and small-intestinal fluid, and then releases therapeutic payload in the colonic environment.
Study Design
GHK-Cu2+-loaded zinc-pectinate microparticles (formulations F1–F8) were prepared by varying surfactant ratio (1.25–1.75 w/w), cross-linking agent concentration, and drug loading (50 mg for F1–F6; 250 mg for F7–F8). Peptide concentration was determined spectrophotometrically. Release profiles were generated in simulated intestinal fluid over 4 h. The optimum microparticle formulation (F8) was then compression-coated with hydroxypropyl cellulose (HPC) at varying coat weights and polymer viscosities to create colonic delivery tablets, with the optimum tablet prepared at 700 mg HPC-SL, and lag time used as the primary endpoint.
Results
Surfactant ratio had a significant effect on production yield, which ranged from 72.22% (at 1.25 w/w) to 80.84% (at 1.75 w/w), while cross-linking agent concentration did not significantly affect yield. Entrapment efficiency (EE) spanned 58.25–78.37% across formulations; increasing drug-loading factor significantly raised EE, whereas increasing cross-linking agent concentration decreased it. In simulated intestinal fluid, microparticles released 50–80% of their drug load within 4 h, with release strongly influenced by cross-linking agent concentration and drug amount but not by surfactant amount.
The optimum colonic tablet (F8 coated with 700 mg HPC-SL) achieved a lag time of 6 h, meeting the design target for colonic-site delivery.
Polymer viscosity and coat weight were both identified as crucial variables controlling lag time, suggesting that HPC grade selection is a key lever for tuning release timing in this system.
Key Findings
- Production yield ranged from 72.22% to 80.84% depending on surfactant ratio (1.25–1.75 w/w).
- Entrapment efficiency spanned 58.25–78.37%; drug-loading increased EE, cross-linker concentration decreased it.
- Microparticles released 50–80% of GHK-Cu2+ within 4 h in simulated intestinal fluid.
- Optimum tablet (F8 + 700 mg HPC-SL) achieved a colonic lag time of 6 h.
- Polymer viscosity and coat weight were identified as the critical determinants of lag time.
Why It Matters
A reproducible 6-hour lag time positions this formulation as a viable oral colon-targeted delivery vehicle for GHK-Cu2+, a peptide that would otherwise be digested or absorbed before reaching inflamed colonic mucosa. For clinicians and formulation scientists working on peptide-based IBD therapies, the identification of HPC coat weight and polymer viscosity as the dominant lag-time levers provides actionable design rules. The finding that cross-linking agent concentration inversely affects entrapment efficiency is a critical quality-by-design parameter for scale-up. Full clinical translation still requires in vivo pharmacokinetic and efficacy validation in relevant animal and human IBD models before this platform can inform a dosing protocol.
TitrateLab articles covering GHK-Cu
Written by TitrateLab, separately from the study summarized above.
