WHAT IS UV DISINFECTION?

Ranging between ultraviolet (UV) and blue light (200 nm – 400 nm) may inactivate/kill pathogens such as bacteria and virus causing disease in various ways depending on the wavelength, exposure time and radiant intensity.

 

In electromagnetic spectrum, the part between 200 nm and 400 nm is named as UV (Ultraviolet) zone (Figure 1). The emitting rays from the sources in this zone is invisible.
UV zone is mainly divided into three parts within itself as UV-A (320-400 nm), UV-B (280-320 nm) and UV-C (200-280 nm).
Since particularly UV-C is relatively high energy rays, direct contact with eye and skin should be avoided.


Figure 1. Electromagnetic spectrum

The emitting sources in UV band generally leads to photochemical effects. Particularly, the emitting rays in UV-C zone (200 nm – 280 nm) are absorbed by the nucleic acids (in DNA and RNA) in the cell nucleus and cause damage to the cell [1] (Figure 2). Therefore, the emitting sources in UV zone can be used in order to kill and/or make the microorganisms ineffective.

Since the zone between 260 nm – 275 nm is the most absorbed wavelength range on the side of proteins in spectrum, inactivation of the sources emitting in this range and the microorganisms is maintained productively. Effect of the emitting sources in UV-B zone is relatively less.
Another disinfection method is narrow-band (400-410 nm) light sources with 405 nm (@peak) wavelength. These light sources have effect at molecular level and inactivate microorganisms in order to damage nucleoides on DNA or RNA like UV-C. [2]. The photon with a wavelength of 405 nm stimulates porphyrin in the cell and deactivates the microorganism. With the stimulation of porphyrin, cytotoxide reactive oxygen species (ROS) are formed in the cell which leads to the cell to become deactivated (Figure 3) [3].


Figure 2. UV-C is absorbed on the side of nucleid acids in DNA                                                             Figure 3. Inactivation process with 405 nm

The amount of radiation that the microorganisms need to be exposed is expressed as dose. The dosage amount may differ for the inactivation of each microorganism. Dose is (dose (D) – J/m2) multiplying of exposed time (time (t) – sec) and radiant flux (radiant flux (IR) – W/m2) (1) [1].

D = IR . t (1)

If the source has a uniform distribution, the radiant flux vary in direct proportion to the radiant power emitted from the source and inversely proportional to the square of the target distance. Radiant flux also depends to light distribution of the source.

Productive disinfection is possible with both methods (UV-C and 405 nm). These methods have advantages and disadvantages compared to each other. It is essential to make required assessments depending on the environment to be used and to select product accordingly. For example, disinfection with narrow band light sources of 405 nm can be effective in longer time (8 – 18 hours) than UV-C since the required dose amounts are high. UV-C lights can be effective in much shorter time (30 minutes – 2 hours), while it is very important that there is no living thing in the environment where these lights are operated which can be directly exposed to ray in order to not being damaged. However, there is no harmful effect on the skin and eye in the environment with light source of 405 nm.

EAE Lighting UV radiation measurement tests are conducted in Phycotec Biyoteknoloji A.Ş laboratory in Boğaziçi University Teknopark.

The tests regarding efficiency of the devices are still ongoing.


The images belong to the control colony exposed to radiation of 405 nm.

 

 

 

 

In the products we design for disinfection process, radiation-emitting LED technology in UV-C and 405 nm band is used.

LED technology has numerous advantages than lamps. Since the mercurial lamps may lead to ozone release, they may cause toxic effect in the environment (which may particularly damage lungs and respiratory tracts) in time. Besides, time spent for the full-efficient operation (heating of lamps, etc.) İs longer than LED products. Therefore, gas lamps may not be suitable for frequent turning on and off. However, this is not valid for LEDs, which can work instantly with full effciency. Additionally, mercury (~20-200mg) is used to increase productivity in gas lamps. When the products are damaged, mercury infiltration and/or dispersion can also produce toxic effects. Another advantage of LED products is their lifetime. Their lifetime is approximately 5 times longer than gas lamps. Since different type of optical elements (lens, reflector etc.) can implement easily in LED system, the rays can be directed to desired area/zone efficiently. LEDs provide more compact and practical design solutions compared to lamps due to their structure.

Scientific research and tests clearly show the reducing effect of 405 nm narrow band radiation-emitting light sources in UV-C zone on microorganisms. With our devices that we have designed and tested in the light of this information, disinfection processes can be performed quickly, effortlessly and continuously, without the need for harmful chemicals (reducing the risk of allergens).

REFERENCES

  1. Kowalski, Wladyslaw. (2009). Ultraviolet Germicidal Irradiation Handbook. 10.1007/978-3-642-01999-9_2.
  2. Maclean M, MacGregor SJ, Anderson JG, Woolsey G. Inactivation of bacterial pathogens following exposure to light from a 405-nanometer light-emitting diode array. Appl Environ Microbiol. 2009;75(7):1932-1937. doi:10.1128/AEM.01892-08
  3. Rutala WA, Kanamori H, Gergen MF, et al. Antimicrobial activity of a continuous visible light disinfection system. Infect Control Hosp Epidemiol. 2018;39(10):1250-1253. doi:10.1017/ice.2018.200

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