Enhancing Rose Bengal penetration in ex vivo human corneas using iontophoresis

Abstract

Aim: Rose Bengal photodynamic antimicrobial therapy (RB-PDAT) has poor corneal penetration, limiting its efficacy against acanthamoeba keratitis (AK). Iontophoresis enhances corneal permeation of charged molecules, piquing interest in its effects on RB in ex vivo human corneas. Methods: Five donor whole globes each underwent iontophoresis with RB, soaking in RB, or were soaked in normal saline (controls). RB penetration and corneal thickness was assessed using confocal microscopy. Results: Iontophoresis increased RB penetration compared with soaking (177 ± 9.5 μm vs. 100 ± 5.7 μm, p < 0.001), with no significant differences in corneal thickness between groups (460 ± 87 μm vs. 407 ± 69 μm, p = 0.432). Conclusion: Iontophoresis significantly improves RB penetration and its use in PDAT could offer a novel therapy for acanthamoeba keratitis. Further studies are needed to validate clinical efficacy.

Plain language summary

The study aimed to improve a new treatment for eye infections known as photodynamic antimicrobial therapy. It investigated whether the use of electricity through a technique called iontophoresis could help a chemical called Rose Bengal go deeper into the eye in order to target more severe infections. The iontophoresis machine was custom built, with patient-contacting components 3D printed. The experiments were performed using donated human eye tissue and found that iontophoresis significantly improved the penetration depth of Rose Bengal as compared with the current technique of only soaking the eye in Rose Bengal.

Article highlights

Background

• Infectious keratitis poses a significant global threat to vision, with Acanthamoeba keratitis (AK) often presenting as deep and severe infection, refractory to medical therapy.

• Current treatments for AK are limited, necessitating investigation into alternative therapies such as Rose Bengal Photodynamic Antimicrobial Therapy (RB-PDAT) and Photo Activated Chromophore for Keratitis-Corneal Cross Linking (PACK-CXL).

• RB-PDAT shows promise but faces challenges due to limited corneal penetration, suggesting the need for methods like iontophoresis to enhance drug delivery into the cornea.

• This study aims to investigate the efficacy of iontophoresis in improving RB penetration depth in ex vivo human corneas, potentially offering a novel approach to treating severe AK.

Methods

• Iontophoresis for RB corneal delivery is achieved using a custom-built, handheld device, applying a reservoir of the drug through a 3D printed cathode.

• The system controls drug delivery by adapting the electric field based on specific resistance, allowing constant current delivery of 2.5 mA.

• Human globes are prepared within 24 h post-mortem, undergoing de-epithelialization before iontophoresis, with a total of 15 human globes (5 iontophoresis, 5 soak only, 5 control) prepared and followed by corneal imaging via confocal microscopy to assess penetration depth.

Results

• Iontophoresis increased RB penetration compared with soaking (177 ± 9.5 μm vs. 100 ± 5.7 μm, p < 0.001), with no significant differences in corneal thickness between groups (460 ± 87 μm vs. 407 ± 69 μm, p = 0.432).

Discussion & conclusion

• The use of iontophoresis is promising for targeting severe AK cases by enhancing Rose Bengal penetration depth, potentially addressing issues of medical treatment failure.

• The development of a custom iontophoresis device utilizing 3D printing technology presents advantages for future clinical applications, particularly in low-resource settings, with considerations for patient safety and feasibility of implementation.

Keywords: :

• acanthamoeba keratitis
• emerging technologies
• iontophoresis
• penetration depth
• personalized delivery
• PK profiles enhancement
• Rose Bengal

Supplemental material

Supplemental data for this article can be accessed at https://doi.org/10.1080/20415990.2024.2371778

Financial disclosure

This work was financially supported in part by the Beauty of Sight Foundation, the Edward D and Janet K Robson Foundation, NIH Center Grant (P30EY014801), Research to Prevent Blindness – Unrestricted Grant to BPEI (GR004596), the Henri and Flore Lesieur Foundation (JMP) and donations from KR Olsen, and ME Hildebrandt. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, stock ownership or options and expert testimony.

Writing disclosure

No writing assistance was utilized in the production of this manuscript.

Additional information

Funding

This work was financially supported in part by the Beauty of Sight Foundation, the Edward D and Janet K Robson Foundation, NIH Center Grant (P30EY014801), Research to Prevent Blindness – Unrestricted Grant to BPEI (GR004596), the Henri and Flore Lesieur Foundation (JMP) and donations from KR Olsen, and ME Hildebrandt.