Rabbit as an Animal Model for Pharmacokinetics Studies of Enteric 
Capsule Contains Recombinant Human Keratinocyte Growth Factor Loaded Chitosan Nanoparticles

BACKGROUND: Recombinant human keratinocyte growth factor (rHuKGF) has gained considerable attention by researchers as epithelial cells proliferating agent. Moreover, intravenous truncated rHuKGF (palifermin) has been approved by Food and Drug Administration (FDA) to treat and prevent chemotherapy-induced oral mucositis and small intestine ulceration. The labile structure and short circulation time of rHuKGF in-vivo are the main obstacles that reduce the oral bioactivity and dosage of such proteins at the target site. OBJECTIVE: Formulation of methacrylic acid-methyl methacrylate copolymer-coated capsules filled with chitosan nanoparticles loaded with rHuKGF for oral delivery. METHODS: We report on chitosan nanoparticles (CNPs) with diameter < 200 nm, prepared by ionic gelation, loaded with rHuKGF and filled in methacrylic acid-methyl methacrylate copolymer-coated capsules for oral delivery. The pharmacokinetic parameters were determined based on the serum levels of rHuKGF, following a single intravenous (IV) or oral dosages using a rabbit model. Furthermore, fluorescent microscope imaging was conducted to investigate the cellular uptake of the rhodamine-labelled rHuKGF-loaded nanoparticles. The proliferation effect of the formulation on FHs 74 Int cells was studied as well by MTT assay. RESULTS: The mucoadhesive and absorption enhancement properties of chitosan and the protective effect of methacrylic acid-methyl methacrylate copolymer against rHuKGF release at the stomach, low pH, were combined to promote and ensure rHuKGF intestinal delivery and increase serum levels of rHuKGF. In addition, in-vitro studies revealed the protein bioactivity since rHuKGF-loaded CNPs significantly increased the proliferation of FHs 74 Int cells. CONCLUSION: The study revealed that oral administration of rHuKGF–loaded CNPs in methacrylic acid-methyl methacrylate copolymer-coated capsules is practically alternative to the IV administration since the absolute bioavailability of the orally administered rHuKGF–loaded CNPs, using the rabbit as animal model, was 69%. Fluorescent microscope imaging revealed that rhodamine-labelled rHuKGF-loaded CNPs were taken up by FHs 74 Int cells, after 6 hours’ incubation time, followed by increase in the proliferation rate.