Dry Lab Design and Engineering Success

Dry Lab Engineering Success

To complement the Wet Lab’s photosynthesizing dye-bound M13 bacteriophage, it was important to design hardware that supplied efficient photodynamic therapy (PDT) for the dye activation and release of reactive oxygen species (ROS).

Research

The initial focus was the identification of the necessary wavelength to successfully activate our photosensitizing dye, Rose-Bengal. Additionally, deciding the distance from the S. aureus infection site and the amount of time the light would need to be applied without harming mammalian cells was especially important. Through further research, it was discovered that blue light between 450-500 nm in wavelength at a distance of approximately 50 cm for 15-20 minutes[4] would be ideal. This was calculated based on the 54-watt LED purchased for the project. Based on research the light should strike the skin with approximately 55 J/cm2 [1]. Using equation one:

E/A = t * S

(1)

Where S is energy flux in units of W/cm2, E is energy in Joules, A is area in cm2, and t is time in seconds. Assuming, approximately 20 minutes of application at an E/A value of 55 J/cm2, S is roughly equal to 0.0458 W/cm2.

P/S = A

(2)

Applying equation two, the power, P, of the LED in use is divided by the calculated S value to find the area that the energy is dispersed over.

π/4(d)2 = A

(3)

sin(45°) = d/L

(4)

Finally, employing equations 3 and 4 by first solving for diameter, d in cm and then solving for length, L using the assumption of approximately 45° light dispersion, the optimal distance for the light is calculated at 54.7 cm from the skin. Further research aided in the discovery that an LED light source would be the most efficient for our purpose. This is due to the efficiency of LED lights and the excess heat created by other light sources, such as fluorescence, which could cause harm or discomfort to the patient[3].

Making a Plan

The wet lab portion of our project is working to chemically conjugate a photosensitizing dye to a genetically modified M13 bacteriophage that specifically targets Staphylococcus aureus bacteria. The dry lab is working to design a lamp that emits the correct wavelength of light to initiate the activation of the photosensitizing dye. Additionally, it is imperative that the created hardware is able to eliminate an S. aureus infection in a medical setting, thus requiring the ability to be sterilized and reach any infected part of the human body.

Cycle 1

The original rendition of the hardware fully engulfed the desired section of the body. This design was called the “Light Glove.” The interior of the “Light Glove” would be lined with calibrated LEDs to activate the conjugated dye. The design allowed for immense customization for different areas of the body due to its adjustable design. Additionally, the adjustable rods on either end of the hardware allowed for containment of the light and infection.

Figure 1. Design one: Light Glove - Disassembled

Figure 2. Design one: Light Glove - Assembled

Perceived Problems

In line with our goal of accessibility, we wanted our device to be usable for all body types and infection sites. The dimensions of the “Light Glove” did not meet these goals, unless it was altered to be too large to be housed in a clinical setting. It also would increase LED light exposure, which although minimal in perceived harms, would decrease comfort of the patient. Furthermore, the number of moving parts in this design made sanitation increasingly difficult and would increase the possibility of cross-contamination between patients. Consequently, a new design was created.

Cycle 2

Our current design for the PDT lamp reimagines the entire structure from the ground up- literally. By creating a free standing lamp, capable of maneuvering to illuminate any part of the body, we eliminate any issues with variance in patient and case specific needs. This design also allows for easy sterilization, with a straightforward assembly anyone can disassemble and sterilize the lamp.

Figure 3. Current Design: Healios Lamp

Possible Future Improvements

The shape of the current bulb doesn’t allow for proper concentration of light, which would increase the efficacy of the treatment. However, greater concentrations of blue light can lead to macular dystrophy if the patient's eyes are exposed to the light. Studies show that greater concentrations of blue light could lead to a painful nerve reaction[1] in the patient, but we hope that the localization of the dye via phage therapy will decrease the likelihood of the nerve reaction due to the targeting of S. aureus. If this is not the case, then further improvements will need to be made to the PDT applicator. Creating a further modular design with a clear cover for the bulb to allow for autoclaving all parts that may come in touch with a patient would be greatly beneficial.

References

  1. Dai, T., Gupta, A., Murray, C. K., Vrahas, M. S., Tegos, G. P., & Hamblin, M. R. (2012). Blue Light for Infectious Diseases: Propionibacterium acnes, helicobacter pylori, and beyond? Drug Resistance Updates, 15(4), 223–236. https://doi.org/10.1016/j.drup.2012.07.001
  2. Kaw, U., Ilyas, M., Bullock, T., Rittwage, L., Riha, M., Vidimos, A., Hu, B., Warren, C. B., & Maytin, E. V. (2020). A regimen to minimize pain during blue light photodynamic therapy of actinic keratoses: Bilaterally controlled, randomized trial of simultaneous versus conventional illumination. Journal of the American Academy of Dermatology, 82(4), 862–868. https://doi.org/10.1016/j.jaad.2019.09.010
  3. Kurosu, M., Mitachi, K., Yang, J., Pershing, E. V., Horowitz, B. D., Wachter, E. A., Lacey, J. W., Ji, Y., & Rodrigues, D. J. (2022). Antibacterial activity of pharmaceutical-grade Rose Bengal: An application of a synthetic dye in antibacterial therapies. Molecules, 27(1), 322. https://doi.org/10.3390/molecules27010322
  4. Uekubo, A., Hiratsuka, K., Aoki, A., Takeuchi, Y., Abiko, Y., & Izumi, Y. (2016). Effect of antimicrobial photodynamic therapy using Rose Bengal and blue light-emitting diode on porphyromonas gingivalis in vitro: Influence of oxygen during treatment. LASER THERAPY, 25(4), 299–308. https://doi.org/10.5978/islsm.16-or-25