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Updated: Aug 19, 2026
Visualization of Bacterial Resistance using Fluorescent Antibiotic Probes
Published on: March 2, 2020
Transscleral permeability of fluorescent-labeled antibiotics
James C Kao1, Dayle H Geroski, Henry F Edelhauser
1Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, USA.
Purpose:
To determine the in vitro transscleral permeability of antibiotics for posterior segment infection.
Methods:
Scleral sections from moist chamber-stored human globes were mounted in a 2-compartment perfusion chamber. Fluorescent-labeled vancomycin, polymyxin B, or penicillin G was added to the episcleral surface, while the choroidal side was slowly perfused with balanced salt solution (Alcon Laboratories, Inc., Ft. Worth, TX). The perfusate was collected and fluorescence was measured using a fluorometer. From the measurements, permeability (Ktrans) was calculated. Photomicrographs were taken with a fluorescent microscope to evaluate tissue absorption.
Results:
The Ktrans values (cm/s, mean +/- standard error) were 6.66 +/- 1.46 x 10(-7) for vancomycin, 3.90 +/- 0.59 x 10(-7) for polymyxin B, and 1.89 +/- 0.21 x 10(-6) for penicillin G. The percent of antibiotic that diffused across the sclera from the donor chamber in 24 hours was 20.6 +/- 4.2 for vancomycin, 12.6 +/- 2.0% for polymyxin B, and 50.8 +/- 4.8% for penicillin G.
Conclusions:
This study shows that human sclera is more permeable to lower molecular weight, water-soluble penicillin G than to vancomycin or polymyxin B. The data suggests that a local, noninvasive, transscleral drug-delivery method may be reasonable for treating intraocular infections.
Insights
Human sclera shows higher permeability to penicillin G than vancomycin or polymyxin B. This suggests transscleral antibiotic delivery may be a viable option for treating posterior segment eye infections.
Area of Science:
- Ophthalmology
- Pharmacology
- Biomedical Engineering
Background:
- Posterior segment intraocular infections pose treatment challenges.
- Effective drug delivery to the posterior eye segment is crucial for successful treatment.
- Transscleral drug delivery offers a potential non-invasive approach.
Purpose of the Study:
- To investigate the in vitro transscleral permeability of key antibiotics.
- To assess the potential of antibiotics to penetrate the sclera for posterior segment infections.
Main Methods:
- Human scleral tissue mounted in a perfusion chamber.
- Fluorescent-labeled antibiotics (vancomycin, polymyxin B, penicillin G) applied to the episcleral surface.
- Perfusate collected and analyzed for antibiotic diffusion using fluorometry.
Main Results:
- Penicillin G exhibited significantly higher transscleral permeability (Ktrans: 1.89 x 10(-6) cm/s) compared to vancomycin and polymyxin B.
- Over 24 hours, 50.8% of penicillin G diffused across the sclera, versus 20.6% for vancomycin and 12.6% for polymyxin B.
- Lower molecular weight, water-soluble antibiotics demonstrated greater scleral penetration.
Conclusions:
- Human sclera permeability varies significantly among different antibiotics.
- Penicillin G, a lower molecular weight antibiotic, penetrates the sclera more readily.
- Transscleral drug delivery is a promising strategy for treating posterior segment ocular infections.
