Effect of cell-penetrating peptide-coated nanostructured lipid carriers on the oral absorption of tripterine

Abstract

Purpose: To develop nanostructured-lipid carriers (NLCs) coated with cell-penetrating peptides (CPP) for improving the oral bioavailability of tripterine.

Methods: We prepared CPP-coated tripterine-loaded NLCs (CT-NLCs) by using a solvent evaporation method, and determined their physical properties. In vitro drug release was determined by using a dialysis bag diffusion technique, and intestinal toxicity was evaluated by performing MTT assay using Caco-2 cells. In vivo absorption was studied in an in situ rat intestinal perfusion model, and oral bioavailability was examined in beagles.

Results: The average particle size, zeta potential, and encapsulation efficiency of the optimized CT-NLCs were 126.7 ± 9.2 nm, 28.7 ± 3.4 mV, and 72.64% ± 1.37%, respectively. The CT-NLCs showed a controlled release profile in vitro and had significantly lower intestinal cytotoxicity than the tripterine solution (P < 0.05). The absorption levels of tripterine from the CT-NLCs in the rat duodenum and jejunum were markedly higher than with tripterine-loaded NLCs without the CPP coating (T-NLCs), and with tripterine solution. Pharmacokinetic study showed that the maximum concentration of the CT-NLCs was greater than that of the T-NLCs and tripterine suspension, and that the time to maximum concentration of the CT-NLCs as well as the T-NLCs, was longer than that of the tripterine suspension. The relative oral bioavailability of the CT-NLCs compared to that of tripterine suspension and T-NLCs were 484.75% and 149.91% respectively.

Conclusion: The oral bioavailability of tripterine is dramatically increased by CT-NLCs. Therefore, CT-NLCs seem to be a promising carrier for oral delivery of tripterine.

Keywords: bioavailability; cell-penetrating peptides; nanostructured lipid carriers; oral drug delivery; tripterine.

Figure 1

Transmission electron micrographs of the (A) T-NLC and (B) CT-NLC formulations. Abbreviations: T-NLC, tripterine-loaded nanostructured lipid carrier; CT-NLC, cell-penetrating peptide-coated T-NLC.

Figure 2

Differential scanning calorimetry curves of (a) tripterine, (b) CPP, (c) physical mixture I, (d) physical mixture II, (e) T-NLCs, and (f) CT-NLCs. Abbreviations: CPP, cell-penetrating peptide; physical mixture I (Precirol ATO-5, Labrafil M 1944CS, soybean lecithin, DPGS, and F68); physical mixture II, physical mixture I + tripterine and CPP; T-NLCs, tripterine-loaded nanostructured lipid carriers; CT-NLC, CPP-coated T-NLC.

Figure 3

In vitro release profiles of tripterine from the T-NLCs and CT-NLCs. Note: Data represent means ± standard deviation (SD). Abbreviations: T-NLCs, tripterine-loaded nanostructured lipid carriers; CT-NLCs, cell-penetrating peptide-coated T-NLCs.

Figure 4

Results of the MTT assay with Caco-2 cells. Notes: Data represent means ± standard deviation (SD). *P < 0.05, **P < 0.01 compared with the tripterine solution. Abbreviations: T-NLCs, tripterine-loaded nanostructured lipid carriers; CT-NLCs, cell-penetrating peptide-coated T-NLCs.

Figure 5

Cellular uptake of tripterine from the CT-NLCs and T-NLCs. Abbreviations: T-NLCs, tripterine-loaded nanostructured lipid carriers; CT-NLCs, cell-penetrating peptide-coated T-NLCs.

Figure 6

Results of the in situ rat intestinal absorption assay. (A) P_eff* and (B) 10 cm%ABS of tripterine, T-NLCs, and CT-NLCs in 4 intestinal segments. Notes: Data represent means ± standard deviation (n = 4). *P < 0.05 compared with the control. Abbreviations: P_eff*, effective permeability; 10 cm%ABS, percent absorption of 10 cm of intestine; T-NLCs, tripterine-loaded nanostructured lipid carriers; CT-NLCs, cell-penetrating peptide-coated T-NLCs.

Figure 7

Plasma concentration profile of tripterine after the oral administration of the CT-NLCs, T-NLCs, and tripterine in beagles (n = 6). Abbreviations: T-NLCs, tripterine-loaded nanostructured lipid carriers; CT-NLCs, cell-penetrating peptide-coated T-NLCs.