Research ArticlesFormulation pH modulates the interaction of insulin with chitosan nanoparticles
Section snippets
INTRODUCTION
Chitosan is a polysaccharide derived from chitin by alkaline deacetylation. Generally regarded as biocompatible, biodegradable, and nontoxic, chitosan is an interesting biomaterial because of its ability to mediate the permeation of molecules across absorptive epithelia. It has been reported to enhance the nasal absorption of insulin in rabbits1 and sheep,2 and the mucosal permeation of other drug molecules.3 The mechanism has been ascribed to a combination of mucoadhesion and widening of the
Materials
Chitosan (CS) (MW) 1.86 (± 0.16) × 105, degree of deacetylation 84.71 ± 0.59%, Aldrich Chemical Co., Milwaukee, WI), insulin (from porcine pancreas, 1 mg was equivalent to 27.8 USP units, Sigma Chemical Co., St. Louis, MO), lysozyme (from chicken egg white, 48,800 U/mg, Sigma Chemical Co.), chitosanase‐RD (from Bacillus SP. PI‐7S, 0.15–0.35 U/mg, Pias Corporation, Osaka, Japan) and pentasodium tripolyphosphate (TPP) (Merck, Darmstadt, Germany) were used as received. All organic solvents were of
RESULTS
Chitosan–insulin nanoparticles were prepared in the pH range of 2.3 to 6.3, achieved by careful control of the acidity and alkalinity of the chitosan and TPP solutions, respectively. Nanoparticle formation was effected by mixing the chitosan and TPP solutions. Insulin was premixed with either the TPP solution or the chitosan solution prior to nanoparticle formation, and the resultant nanoparticles are designated as TPP‐np and CS‐np, respectively. The initial insulin loading concentration was
DISCUSSION
The chitosan–insulin nanoparticles were produced by ionotropic gelation with the counterion, TPP. Chitosan, which has an apparent pKa of 6.3, assumes a stiff extended conformation in aqueous media of low pH due to the charge repulsion of highly protonated amino groups, but it becomes increasingly globular as pH increases, and can precipitate at pH 6.6 or lower, depending on the ionic strength of the solution.14 In this study, precipitation was apparent at pH ≥ 6.3, while the particle yield was
CONCLUSION
Chitosan nanoparticles (237 to 325 nm) with insulin association efficiency that varied from 2 to 85% could be prepared by the iontropic gelation method with careful control of the formulation pH from 2.3 to 6.3. The insulin association was very sensitive to formulation pH, and was also dependent on insulin loading concentration. High association (≥ 80%), attributed to physical adsorption predominated by hydrophobic interactions with chitosan, occurred at insulin loading concentrations ≥ 4.28
Acknowledgements
This study is supported by a National University of Singapore grant (R148‐000‐023‐112). Zengshuan Ma is grateful to the National University of Singapore for financial support of his graduate studies.
REFERENCES (25)
- et al.
Oral insulin delivery
Adv Drug Deliv Rev
(1999) - et al.
Chitosan beads and granules for oral sustained delivery of nifedipine: In vitro studies
Biomaterials
(1992) - et al.
The adsorption of bovine serum albumin on positively and negatively charged polystyrene lattices
J Colloid Int Sci
(1990) - et al.
Chitosan–DNA nanoparticles as gene carriers: Synthesis, characterization and transfection efficiency
J Control Rel
(2001) - et al.
Ionization behavior of native and mutant insulins: pK perturbation of B13‐Glu in aggregated species
Arch Biochem Biophy
(1990) - et al.
Toward understanding insulin fibrillation
J Pharm Sci
(1997) - et al.
Studies of the structure of insulin fibrils by Fourier Transform infrared (FTIR) spectroscopy and electron microscope
J Pharm Sci
(2001) - et al.
Enhancement of nasal absorption of insulin using chitosan nanoparticles
Pharm Res
(1999) - et al.
Chitosan as a novel nasal delivery system for peptide drugs
Pharm Res
(1994) - et al.
Chitosan for enhanced delivery of therapeutic peptides across intestinal epithelia: In vitro evaluation in Caco‐2 cell monolayers
Int J Pharm
(1997)