In vitro evaluation of compression-coated glycyl-L-histidyl-L-lysine-Cu(II) (GHK-Cu2+)-loaded microparticles for colonic drug delivery.

Glycyl-L-histidyl-L-lysine-Cu(II) (GHK-Cu(2+))-loaded Zn-pectinate microparticles in the form of hydroxypropyl cellulose (HPC) compression-coated tablets were prepared and their in vitro behavior tested. GHK-Cu(2+) delivery to colon can be useful for the inhibition of matrix metalloproteinase, with the increasing secretion of tissue inhibitors of metalloproteinases (TIMPS),which are the major factors contributing in mucosal ulceration and inflammation in inflammatory bowel disease. The concentration of peptide was determined spectrophotometrically. The results obtained implied that surfactant ratio had a significant effect on percent production yield (1.25 to 1.75 w/w; 72.22% to 80.84%), but cross-linking agent concentration had not. The entrapment efficiency (EE) was found to be in the range of 58.25-78.37%. The drug-loading factor significantly increased the EE; however, enhancement of cross-linking agent concentration decreased it. The release of GHK-Cu(2+) from Zn-pectinate microparticles (F1-F8) in simulated intestinal fluid was strongly affected by cross-linking agent concentration and drug amount (50 mg for F1-F6; 250 mg for F7-F8), but not particularly affected by surfactant amount. Release profiles represented that the microparticles released 50-80% their drug load within 4 h. Therefore, the optimum microparticle formulation (F8) coated with a relatively hydrophobic polymer HPC to get a suitable colonic delivery system. The optimum colonic delivery tablets prepared with 700 mg HPC-SL provided the expected delayed release with a lag time of 6 h. The effects of polymer viscosity and coat weight on GHK-Cu(2+) release were found to be crucial for the optimum delay of lag time. The invention was found to be promising for colonic delivery.