Bilosomes and Niosomes for Enhanced Intestinal Absorption and In Vivo Efficacy of Cytarabine in Treatment of Acute Myeloid Leukemia

Abstract

Cytarabine (CTR) is a hydrophilic anticancer drug used to treat leukemia. It suffers from poor permeability and intestinal metabolism, diminishing its oral bioavailability.

Background/objectives: The objective was to develop and evaluate niosomes and bilosomes for enhanced intestinal absorption; hence, oral bioavailability.

Results: CTR-loaded niosomes and bilosomes with vesicle sizes of 152 and 204.3 nm were successfully prepared with acceptable properties. The presence of bile salts increased the zeta potential of bilosomes. The recorded entrapment efficiency of cytarabine was acceptable for such a hydrophilic drug. CTR-bilosomes showed a pH-dependent drug release pattern with preferred release in pH 6.8. Intestinal absorption behavior indicated a site-dependent CTR absorption pattern with unfavorable absorption in the distal intestine. Niosomal and bilosomal formulations enhanced intestinal absorption parameters with evidence for a predominant paracellular absorption mechanism that bypasses intestinal barriers. The investigation of the anti-leukemic effect of niosomal and bilosomal formulations indicated that both formulations ameliorated the blood parameters, reflecting significant improvement in leukemia treatment compared with the drug solution. Pathological examination of blood films revealed decreased blast cells in peripheral blood in groups treated with tested formulations.

Methods: Tested formulations were prepared according to the pro-concentrate method and characterized for particle size, zeta potential, entrapment efficiency, and in vitro release. CTR-loaded niosomes and bilosomes were evaluated for enhanced intestinal absorption utilizing the single-pass in situ intestinal perfusion method in rabbits, and the anti-leukemic effect was assessed using the benzene-induced leukemia model in rats.

Conclusions: This study introduced surfactant vesicles for enhanced oral bioavailability of CTR.

Keywords: bilosomes; cytarabine; intestinal perfusion; leukemia; niosomes.

Figure 1

(A) Chromatograms of calibration standards of CTR in different concentrations (2, 4, 6, 8 and 10 μg/mL); and (B) the constructed calibration curve between area under the curve (AUC) of the peak (mAU) and CTR concentration (μg/mL).

Figure 2

(A,B) Transmission electron micrographs of CTR-niosomes; (C) histogram representing size distribution of CTR-niosome in diameter frequency (%); (D,E) CTR-bilosomes; and (F) histogram representing size distribution of CTR-bilosome in diameter frequency (%).

Figure 3

Release profiles of cytarabine from (a) CTR-niosomes and CTR-bilosomes at pH 6.8 for 10 h; (b) Fitting of release profiles of the tested niosomes and bilosomes at pH 6.8 with Higuchi release kinetic model; (c) the CTR-niosomes at different intestinal pH, including 6.6, 6.8, and 7.4 for 2 h; (d) CTR-bilosomes at different intestinal pH, including 6.6, 6.8, and 7.4 for 2 h; and (e) CTR-niosomes and CTR-bilosomes at continuous pH variation medium for 10 h. * Amounts of CTR release from niosomes are significantly higher than that recorded from bilosomes at corresponding time points.

Figure 4

Bar charts of (a) absorptive clearance; (b) L95%; and (c) percent of paracellular pathway in intestinal absorption of CTR passing different segments of GIT in the form of CTR solution (blue), niosomes (CTR-niosomes) (orange), and bilosomes (CTR-bilosomes) (green). Values are expressed in mean ± SD (n = 4). * Significantly different compared to the corresponding CTR solution. p < 0.05 is considered significant.

Figure 5

Comparative effect of CTR solution (group C), CTR-niosomes (group D), and CTR-bilosomes (group E) on (a) hemoglobin (Hgb); (b) red blood cell counts (RBCs); (c) hematocrit (Hct); and (d) white blood cell counts (WBCs). All graphs are compared to the healthy group (group A) and the diseased untreated group (group B). Values are expressed in mean ± SD (n = 5). p < 0.05 is considered significant. a: significant compared to group A. b: significant compared to group B. c: significant compared to group C.

Figure 6

Blood film pictures represent animals in (A) the normal group; (B) diseased group; (C) the group treated with CTR solution; (D) CTR-niosomes; and (E) CTR-bilosomes.

Figure 7

Schematic illustration of experimental design of in vivo assessment of the anti-leukemic effect of CTR solution, CTR-niosomes, and CTR-bilosomes.