Drug permeability and mucoadhesion properties of thiolated trimethyl chitosan nanoparticles in oral insulin delivery

Trimethyl chitosan-cysteine conjugate (TMC-Cys) was synthesized in an attempt to combine the mucoadhesion and the permeation enhancing effects of TMC and thiolated polymers related to different mechanisms for oral absorption. TMC-Cys with various molecular weights (30, 200, and 500 kDa) and quaternization degrees (15 and 30%) was allowed to form polyelectrolyte nanoparticles with insulin through self-assembly, which demonstrated particle size of 100–200 nm, zeta potential of +12 to +18 mV, and high encapsulation efficiency. TMC-Cys/insulin nanoparticles (TMC-Cys NP) showed a 2.1–4.7-fold increase in mucoadhesion compared to TMC/insulin nanoparticles (TMC NP), which might be partly attributed to disulfide formation between TMC-Cys and mucin as evidenced by DSC measurement. Compared to insulin solution and TMC NP, TMC-Cys NP induced increased insulin transport through rat intestine by 3.3–11.7 and 1.7–2.6 folds, promoted Caco-2 cell internalization by 7.5–12.7 and 1.7–3.0 folds, and augmented uptake in Peyer's patches by 14.7–20.9 and 1.7–5.0 folds, respectively. Such results were further confirmed by in vivo experiment with the optimal TMC-Cys NP. Biocompatibility assessment revealed lack of toxicity of TMC-Cys NP. Therefore, self-assembled nanoparticles between TMC-Cys and protein drugs could be an effective and safe oral delivery system.     

Colloidal carrier integrating biomaterials for oral insulin delivery: Influence of component formulation on physicochemical and biological parameters

Strategies to design effective and safe colloidal carriers for biopharmaceuticals have evolved through applying the knowledge gained in nanotechnology to medicine. Designing a colloidal carrier to serve as a protein delivery device requires an understanding of the effect of different materials on the physicochemical, physiological and toxicological parameters for clinical application. The purpose of this study was to evaluate the influence of formulation components on the physicochemical factors and biological function involved in the development and optimization of newly designed nanoparticles for orally dosed insulin. Biodegradable, biocompatible, mucoadhesive and protease-protective biomaterials were combined through ionotropic pre-gelation and polyelectrolyte complexation forming an alginate, dextran sulfate and poloxamer hydrogel containing insulin, stabilized in nanoparticles with chitosan and poly(ethyleneglycol) and coated with albumin. Nanoparticles ranged in size from 200 to 500 nm with 70–90% insulin entrapment efficiency, and electrostatic stabilization was suggested by zeta potential values lower than −30 mV. This combination of formulation components was selected for insulin protection against harsh gastric pH and proteolytic conditions, and to improve insulin absorption through intestinal mucosa by combining nanoparticle uptake and insulin release at the site of absorption. Insulin was shown to be bioactive after nanoparticle formulation and release in neutral pH conditions. Fourier transform infrared spectroscopy was used to confirm the presence of formulations components in the nanoparticle structure and to identify potential interactions between biomaterials.     

Protease inhibition and absorption enhancement by functional nanoparticles for effective oral insulin delivery

Complexing agents such as diethylene triamine pentaacetic acid (DTPA) are known to disrupt intestinal tight junctions and inhibit intestinal proteases by chelating divalent metal ions. This study attempts to incorporate these benefits of DTPA in functional nanoparticles (NPs) for oral insulin delivery. To maintain the complexing agent concentrated on the intestinal mucosal surface, where the paracellular permeation enhancement and enzyme inhibition are required, DTPA was covalently conjugated on poly(γ-glutamic acid) (γPGA). The functional NPs were prepared by mixing cationic chitosan (CS) with anionic γPGA-DTPA conjugate. The γPGA-DTPA conjugate inhibited the intestinal proteases substantially, and produced a transient and reversible enhancement of paracellular permeability. The prepared NPs were pH-responsive; with an increasing pH, CS/γPGA-DTPA NPs swelled gradually and disintegrated at a pH value above 7.0. Additionally, the biodistribution of insulin orally delivered by CS/γPGA-DTPA NPs in rats was examined by confocal microscopy and scintigraphy. Experimental results indicate that CS/γPGA-DTPA NPs can promote the insulin absorption throughout the entire small intestine; the absorbed insulin was clearly identified in the kidney and bladder. In addition to producing a prolonged reduction in blood glucose levels, the oral intake of the enteric-coated capsule containing CS/γPGA-DTPA NPs showed a maximum insulin concentration at 4 h after treatment. The relative oral bioavailability of insulin was approximately 20%. Results of this study demonstrate the potential role for the proposed formulation in delivering therapeutic proteins by oral route.