Evaluation of the levofloxacin release characters from a rabbit foldable capsular vitreous body

Abstract

The authors have manufactured a novel rabbit foldable capsular vitreous body (FCVB). The aim of this study was to determine whether this rabbit FCVB can release levofloxacin in vitro and in vivo, and to evaluate the release characteristics. In vitro, the rabbit FCVB with levofloxacin 500 μg/mL was immersed in cups of modified Franz diffusion cells. Following this, 200 μL of liquid was aspirated at intervals from 10 minutes to 24 hours. In vivo, the FCVB with levofloxacin was implanted into the right eyes of five rabbits. After implantation, the aqueous humor was aspirated on days 1, 7, 14, 28, and 56. The levofloxacin concentrations in the cups and aqueous humor samples were detected by high-performance liquid chromatography-tandem mass spectrometry. The FCVB was observed under a scanning electron microscope. The results showed that the released levofloxacin was stabilized at 20 ng/mL at time points from 10 minutes to 24 hours in vitro. In vivo, levofloxacin concentrations in the aqueous humor were 132, 50, 39, 11, and 15 ng/mL on days 1, 7, 14, 28, and 56, respectively. In the FCVB capsules, 300 nm apertures were observed. These results suggest the rabbit FCVB released levofloxacin stably in vitro and sustainably in vivo. This study provides a novel combined approach, with the FCVB as a vitreous substitute and drug delivery system for the treatment of bacterial endophthalmitis.

Keywords: bacterial endophthalmitis; drug delivery system; high-performance liquid chromatography–tandem mass spectrometry; vitreous substitute.

Figure 1

(A) Rabbit foldable capsular vitreous body (FCVB) filled with levofloxacin was immersed in cups of modified Franz diffusion cells, (B) a simple diagram of the releasing cell, and (C) the chemical structure of levofloxacin.

Figure 2

Rabbit foldable capsular vitreous body (FCVB) with levofloxacin was implanted in vivo. (A) Pars plana vitrectomy was performed on the right eye, (B) the capsule of FCVB was folded, (C) FCVB was implanted into the vitreous cavity, and (D) levofloxacin solution was injected into the capsule through the valve.

Figure 3

Steel mold and production of rabbit foldable capsular vitreous body (FCVB). (A) The mold for rabbit FCVB consisted of a core and lower and upper dies, (B) fabricated rabbit FCVB, and (C) the rabbit FCVB is highly transparent.

Figure 4

The production mass spectra of abundant protonated molecular ions ([M+H]+) for levofloxacin and ciprofloxacin. (A) Fragment ions of mass-to-charge ratio (m/z) 362.0 → 318.1 were chosen as the production for monitoring levofloxacin and (B) fragment ions of m/z 332.2 → 314.0 were chosen for ciprofloxacin.

Figure 5

Representative high-performance liquid chromatography–tandem mass spectrometry chromatograms of (A) blank water (H₂O), (B) blank H₂O with internal standard ciprofloxacin, and (C) blank H₂O with a sample of levofloxacin.

Figure 6

The levofloxacin released from the foldable capsular vitreous body stabilized at 20 ng/mL in vitro. Abbreviations: C, concentration; T, time.

Figure 7

Foldable capsular vitreous body (FCVB) continuously released levofloxacin in vivo. The levofloxacin in the aqueous humor was 132, 50, 39, 11, and 15 ng/mL on days 1, 7, 14, 28, and 56, respectively, after rabbit FCVB implantation. In the control group, the levofloxacin was 183, 9, and 0 ng/mL on days 1, 7, and 14, respectively. Abbreviations: C, concentration; d, days; PPV, pars plana vitrectomy; T, time.

Figure 8

Scanning electron microscope images of the capsule of the foldable capsular vitreous body where (A) 300 nm-mm apertures were observed in the capsule before release study and (B) apertures were observed at the end of release study.

Figure 9

In the Staphylococcus aureus endophthalmitis rabbit model, the rabbit foldable capsular vitreous body (FCVB) with levofloxacin 625 μg/mL tamponade and the culture results of aqueous humor were sterile. (A) S. aureus endophthalmitis rabbit model, (B) surgery of FCVB tamponade, and (C) no signs of endophthalmitis were observed in the treated eye.