The research demonstrates that 222-nm far-UVC light is safe for eye tissue and effectively kills bacteria on the cornea, offering a promising new method for disinfection in ophthalmic surgery.
- 222-nm far-UVC exposure is safe for corneal epithelial cells. - 9 mJ/cm2 of 222-nm far-UVC effectively eliminates bacteria on the corneal surface. - Silk fibroin (SF) corneal bandages provide a suture-less alternative to amniotic membrane for corneal abrasions. - SF membranes show good bonding strength and stability in both lab and live rabbit models. - No signs of edema or significant neovascularization observed in treated corneas.
This is from IOVS in 2024 at https://iovs.arvojournals.org/article.aspx?articleid=2787973
1. Far-UVC 2. Disinfection 3. Ophthalmic surgery 4. Corneal tissue 5. Safety
Abstract
Purpose : Far-ultraviolet C (UVC) is an efficient germicidal tool. Despite this, the safety issue of far-UVC exposure has been a point of contention on the ocular surface, preventing their large-scale implementation in the clinic. Thus, the purpose of this study is to investigate the safety and disinfection ability of 222nm far-UVC exposure on rat corneal tissue. To evaluate the effectiveness of far-UVC exposure in disinfecting surgical wounds, its efficiency was compared to that of traditional disinfectants, such as 5% povidone-iodine (PVP-I, known as Betadine) (diluted in balanced salt solution).
Methods : To evaluate the safety of 222-nm far-UVC exposure, rat corneas were exposed to 222-nm far-UVC at fixed intensity (3 mW/cm2) and distance (2 cm) for 1, 5, 10, 15, and 20 seconds. H&E stain, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and reactive oxygen species (ROS) assay were used to assess the cornea’s tissue damage, apoptosis, and inflammatory response, separately. For disinfection, the rat received 222-nm far-UVC treatment in a safe exposure window to destroy germs on the corneal surface. The viable bacteria on the corneal surface were collected by using contact plate stamping and analyzed with colony count and identification (gram stain, colony morphology, coagulase agglutination). Colony counts were measured by the number of colonies formed per plate.
Results : The 222-nm far-UVC radiation didn’t trigger apoptosis and inflammatory response within 1 to 5 seconds (below 15 mJ/cm2) of exposure in rat corneal tissue. Some apoptotic cells were detected in the first layer of corneal epithelium after 10 seconds (more than 30 mJ/cm2) of 222-nm far-UVC exposure. In comparison to 5% PVP-I, the number of all bacteria strains is significantly lower after 3 seconds (9 mJ/cm2) of exposure. Among all the bacteria strains, the reduction of 90.5% is the most significant after exposure to 222-nm far-UVC.
Conclusions : Our data demonstrated that 9 mJ/cm2 of 222-nm far-UVC exposure is not only safe for corneal epithelial cells but also sufficient to eliminate bacteria on the corneal surface. Ultimately, this study provides critical information to develop a safe, efficient, and non-irritating disinfection method for ophthalmologic surgeries.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.
Abstract
Purpose : Standard-of-care treatment for corneal abrasions consists of suturing amniotic membrane (AM) to the cornea. We have developed silk fibroin (SF) corneal bandages and a light-initiated fixation method that overcomes the potential allograft rejection, opacity, and scarcity of the AM, as well as need for sutures. We demonstrate the method and the optimization of photobonding parameters in a rabbit eye model ex vivo and in vivo.
Methods : SF was extracted from silkworm cocoons in water solution. 3% SF with 5% polyethylene glycol (PEG) solution was cast at 250C and 40% relative humidity. PEG acts as a crosslinker and porogen. Membranes were characterized by Fourier transform infrared spectroscopy (FTIR), cut into 8x10 mm strips with rounded corners and soaked in 0.01% Rose Bengal photosensitizer for 10min. Experiments were performed on corneal strips from 4 enucleated eyes and on 7 eyes in vivo, in a New Zealand rabbit model. Irradiation was carried out with 532nm collimated green laser light (0.15W/cm2 irradiance for 6.6min). Ex vivo, stained strip membranes were placed on corneal strips and irradiated. 24h post-treatment, the photobonding strength was characterized by uniaxial stretching. In vivo, stained membranes were placed on a pupil-centered vertical rectangular deepithelialized area of the same size. An opaque mask covered the limbus and the pupil leaving a rim of 2mm on either side of the bandage for irradiation. Animal follow up (0-15days) included clinical signs, neovessels formation, and membrane stability, bonding and transparency.
Results : Membranes showed 35-40μm thickness, 10.4±1.8MPa Young's modulus, >1 month stability in PBS and 24h in protease XIV. In corneas ex vivo, bonding force was 1.37 ± 0.24N/cm2. In vivo, the SF membranes remained bonded >1 week in 85% of the rabbits, and corneas showed no sign of edema. The membranes were fully transparent (no RB in the non-irradiated area) 10 days after bonding. Neovessels were observed superiorly, without reaching the optical area.
Conclusions : We have developed SF-based corneal bandages as alternative to AM dressing, and a photobonding paradigm that produces firm suture-less fixation to the cornea both ex vivo and in vivo. The procedure has proved safe and stable over time. Fine-tuning of some fabrication parameters (decreased membrane thickness or increased permeability) could eliminate the neovascularization found in some eyes.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.