Formulation and Evaluation of Moxifloxacin Loaded Bilosomes In-Situ Gel: Optimization to Antibacterial Evaluation

Abstract

In this study, moxifloxacin (MX)-loaded bilosome (BS) in situ gel was prepared to improve ocular residence time. MX-BSs were prepared using the thin-film hydration method. They were optimized using a Box−Behnken design (BBD) with bile salt (A, sodium deoxycholate), an edge activator (B, Cremophor EL), and a surfactant (C, Span 60) as process variables. Their effects were assessed based on hydrodynamic diameter (Y1), entrapment efficacy (Y2), and polydispersity index (Y3). The optimized formulation (MX-BSop) depicted a low hydrodynamic diameter (192 ± 4 nm) and high entrapment efficiency (76 ± 1%). Further, MX-BSop was successfully transformed into an in situ gel using chitosan and sodium alginate as carriers. The optimized MX-BSop in situ gel (MX-BSop-Ig4) was further evaluated for gelling capacity, clarity, pH, viscosity, in vitro release, bio-adhesiveness, ex vivo permeation, toxicity, and antimicrobial properties. MX-BSop-Ig4 exhibited an optimum viscosity of 65.4 ± 5.3 cps in sol and 287.5 ± 10.5 cps in gel states. The sustained release profile (82 ± 4% in 24 h) was achieved with a Korsmeyer−Peppas kinetic release model (R2 = 0.9466). Significant bio-adhesion (967.9 dyne/cm2) was achieved in tear film. It also exhibited 1.2-fold and 2.8-fold higher permeation than MX-Ig and a pure MX solution, respectively. It did not show any toxicity to the tested tissue, confirmed by corneal hydration (77.3%), cornea histopathology (no internal changes), and a HET-CAM test (zero score). MX-BSop-Ig4 exhibited a significantly (p < 0.05) higher antimicrobial effect than pure MX against Staphylococcus aureus and Escherichia coli. The findings suggest that bilosome in situ gel is a good alternative to increase corneal residence time, as well as to improve therapeutic activity.

Keywords: antimicrobial activity; bilosomes; moxifloxacin; ocular delivery; toxicity study.

Figure 2

Effect of independent variables sodium deoxycholate (A), Cremophor EL (B), and Span 60 (C) on hydrodynamic diameter (Y₁).

Figure 3

Effect of independent variables (A) sodium deoxycholate, (B) Cremophor EL, and (C) Span 60 on entrapment efficiency (Y₂).

Figure 4

Effect of independent variables sodium deoxycholate (A), Cremophor EL (B), and Span 60 (C) on PDI (Y₃).

Figure 5

Actual and predicted images of (A) hydrodynamic diameter (Y₁), (B) entrapment efficiency (Y₂), and (C) PDI (Y₃). Color full square indicated the actual and predicted data of the responses.

Figure 1

Chemical structures of (A) moxifloxacin, (B) chitosan, and (C) sodium alginate.

Figure 6

Hydrodynamic diameter image of optimized moxifloxacin bilosomes (MX-BSop).

Figure 7

DSC thermogram of moxifloxacin, cholesterol, Span 60, sodium alginate, chitosan, optimized moxifloxacin bilosomes (MX-BSop), and optimized moxifloxacin bilosome in situ gel (MX-BSop-Ig4).

Figure 8

In vitro drug release profiles of MX from moxifloxacin-loaded bilosome in situ gel (MX-BSop-Ig4), moxifloxacin in situ gel (MX-lg), and pure MX solution. The study was performed in triplicate, and data are shown as mean ± SD.

Figure 9

Histopathology images of (A) moxifloxacin-loaded bilosome in situ gel (MX-BSop-Ig4) and (B) normal-saline-treated cornea.

Figure 10

HET-CAM images of (A) normal saline, (B) moxifloxacin-loaded bilosome in situ gel (MX-BSop-Ig4), and (C) positive-control-treated cornea.

Figure 11

Isotonicity images of (A) normal saline and (B) moxifloxacin-loaded bilosome in situ gel (MX-BSop-Ig4).

Figure 12

Antibacterial activity of MX-BSop-Ig4 and pure MX solution treated against E. coli and S. aureus. The study was performed in triplicate, and data are shown as mean ± SD. * indicates significant and *** indicates highly significant to pure MX.