Development of Octreotide-Loaded Chitosan and Heparin Nanoparticles: Evaluation of Surface Modification Effect on Physicochemical Properties and Macrophage Uptake.

Octreotide (OCT) is a therapeutic peptide which is administered for the treatment of acromegaly. The purpose of this study was to design a new polyethylene glycol (PEG)-conjugated nanoparticle (PEG-NP) to overcome the short half-life and poor stability of OCT. The developed PEG-NPs were compared with non-PEGylated NPs with respect to their size, morphological characteristics, loading efficiency, release profile, and macrophage uptake. The OCT-loaded NPs and PEG-NPs were prepared by ionic complexion of chitosan (Cs) with either heparin (Hp) or PEGylated heparin (PEG-Hp). The chemical structure of PEG-Hp was confirmed by IR and proton nuclear magnetic resonance. Morphological analyses by scanning electron microscopy showed that NPs and PEG-NPs have a uniform shape. Dynamic laser scattering measurements indicated that hydrodynamic diameter of NPs and PEG-NPs were 222.5 ± 10.0 nm and 334.9 ± 6.7 nm, respectively. NPs and PEG-NPs had a positive zeta potential of about 32.5 ± 1.1 mv and 20.6 ± 2.4 mv, respectively. Entrapment efficiency was 61.4 ± 1.0% and 55.7 ± 2.4% for NPs and PEG-NPs, respectively. Compared with the NPs, the PEG-NPs exhibited a slower release profile. Subsequently, fluorescein isothiocyanate-labeled chitosanCs was synthesized and used to evaluate the stealth characteristic of PEG-NPs. In vitro macrophage uptake of fluorescently labeled NPs was measured by flow cytometry.