Pathogen reduction / growth suppression system using ultraviolet A (UVA) and ultraviolet C (UVC) in combination

Abstract

A UVA / UVC system for reducing the level of at least one pathogen on a surface and inhibiting further growth of at least one pathogen on the surface, wherein the UVA / UVC system does not have harmful effects on humans, particularly on the eyes or the epidermis and dermis of humans, the system comprising: iv) at least one UVA light source; v) at least one UVC light source; and at least one controller coupled to each of the at least one UVA light source and the at least one UVC light source and controlling at least one parameter of each of the UVA light source and the UVC light source.

Description

[Technical Field]

[0001] The present invention relates to systems and methods for reducing and inhibiting pathogen growth in public places, such as areas frequently traveled by public transportation vehicles, by using UVA and UVC light sources at levels that are harmful to pathogens but safe for animals, including mammals and humans. [Background technology]

[0002] UVC light sources are known to be highly effective at reducing bacterial levels on surfaces, but the typical exposure times required to achieve this can be harmful to the human eyes, epidermis, and dermis.

[0003] What is needed is a system that keeps bacterial levels on surfaces low enough to be safe for human exposure and inhibits further growth. Summary of the Invention

[0004] According to one aspect, the present invention provides an alternating UVA / UVC system for reducing the level of at least one pathogen on a surface and inhibiting further growth of said pathogen without harmful effects on the eyes, epidermis, and dermis of animals, including humans, particularly humans, comprising: i) at least one UVA light source; ii) at least one UVC light source; and iii) A system including at least one controller connected to each of the at least one UVA light source and the at least one UVC light source and controlling at least one parameter of each of the at least one UVA light source and the at least one UVC light source, such as light intensity, radiation output level, wavelength, exposure time, and more, wherein the at least one UVC light source emits UVC light onto a surface for a time (duration) that reduces the level of the pathogen to a level safe for humans and other animals, and the at least one UVA light source emits UVA light onto a surface for a time (duration) that inhibits the growth of the pathogen, and the at least one UVC The system provides a system in which radiation levels from the one UVC light source and the at least one UVA light source are safe for humans and other animals while the light source and the at least one UVA light source are emitting light onto the surface, the at least one UVC light is in an off state when the at least one UVC light source is emitting UVA light onto the surface, and the at least one UVC light source is in an off state when the at least one UVA light source is emitting light onto the surface, and the at least one UVC light source is in an off state, and the repeated cycling between the at least one UVC light source and the at least one UVA light source is controlled by the at least one control device.

[0005] In another embodiment, the at least one UVC light source has an operating wavelength of about 275 nanometers (nm) to about 295 nm. In another embodiment, the at least one UVC light source has an operating wavelength of about 275 nm.

[0006] In another embodiment, the at least one UVA light source has an operating wavelength of about 385 nm to about 405 nm. In another embodiment, the at least one UVA light source has an operating wavelength of about 405 nm.

[0007] In yet another embodiment, the at least one UVC light source is a light emitting diode (LED).

[0008] In yet another embodiment, the at least one UVA light source is an LED.

[0009] In one embodiment, the at least one controller automatically controls (automates) cycling between the emission of the at least one UVA light source and the emission of the at least one UVC light source.

[0010] In one embodiment, the at least one UVC light source emits light at a predetermined power level and for a predetermined time that results in low pathogen levels on surfaces exposed to the at least one UVC light source.

[0011] In one embodiment, the power level of the at least one UVC light source is selected to ensure that the radiation emission is at a level that is safe for the human eye and the epidermis and dermis.

[0012] In one embodiment, the time period is selected to ensure a safe exposure time for the human eye, epidermis, and dermis to the radiation emitted by the at least one UVC light source.

[0013] In one embodiment, the at least one UVA light source emits light at a power level that inhibits the growth of at least one pathogen on a surface exposed to the at least one UVC light source, regardless of exposure time, while remaining safe for the human eye and epidermis and dermis.

[0014] In one embodiment, the at least one UVC light source has a power rating of about 10 mW to about 100 W. In one embodiment, the at least one UVC light source has a power rating of 244 mW.

[0015] In one embodiment, the at least one UVA light source has a power rating of about 10 mW to about 100 W. In one embodiment, the at least one UVA light source has a power rating of 20 mW.

[0016] In one embodiment, the system reduces pathogen levels on surfaces exposed to the system by 1% to about 100%, and in one embodiment, by 10% to about 20%.

[0017] Yet another aspect is a method for reducing the level of at least one pathogen on a surface and inhibiting further growth of the pathogen on the surface without adverse effects on the eyes or epidermis and dermis of an animal, including humans, particularly humans, comprising: i) exposing the surface to at least one UVC light source for a predetermined time period that reduces the level of at least one pathogen on the surface; ii) terminating the exposure of the surface to the at least one UVC light source; iii) exposing the UVC exposed surface to at least one UVA light source for a period of time that inhibits the growth of at least one pathogen on the surface; iv) terminating the exposure of the surface to the at least one UVA light source; and v) optionally repeating steps i) through iv) to maintain a desired level of said at least one pathogen on said surface.

[0018] In another embodiment, the at least one UVC light source has an operating wavelength of about 275 nanometers (nm) to about 295 nm. In another embodiment, the at least one UVC light source has an operating wavelength of about 275 nm.

[0019] In another embodiment, the at least one UVA light source has an operating wavelength of about 385 nm to about 405 nm. In another embodiment, the at least one UVA light source has an operating wavelength of about 405 nm.

[0020] In yet another embodiment, the at least one UVC light source is a light emitting diode (LED).

[0021] In yet another embodiment, the at least one UVA light source is an LED.

[0022] In another embodiment, steps i) through iv) are controlled by at least one controller that automates repeated cycling between emission of light from the at least one UVA light source and emission of light from the at least one UVC light source.

[0023] In another embodiment, the at least one UVC light source emits light at a predetermined power level and for a predetermined time period that reduces the concentration of at least one pathogen on surfaces exposed to the at least one UVC light source.

[0024] In one embodiment, the power level of the at least one UVC light source is selected to ensure that the radiation emission is at a level that is safe for the human eye and the epidermis and dermis.

[0025] In one embodiment, the time period is selected to ensure a safe exposure time for the human eye, epidermis, and dermis to the radiation emitted by the at least one UVC light source.

[0026] In another embodiment, the at least one UVA light source emits light at a power level that inhibits the growth of at least one pathogen on a surface exposed to the at least one UVC light source, regardless of exposure time, while remaining safe for human eyes and the human epidermis and dermis.

[0027] In another embodiment, the at least one UVC light source has a power rating of about 10 mW to about 100 W, and in another embodiment, a power rating of 20 mW.

[0028] In another embodiment, the at least one UVA light source has a power rating of about 10 mW to about 100 W. In another embodiment, the at least one UVA light source has a power rating of 20 mW.

[0029] In one embodiment, the method reduces the level of at least one pathogen on a surface by 1-100%, and in another embodiment, the method reduces the growth of the pathogen by 1-100%, or in another embodiment, by at least one of the following ranges: 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, 60-70%, 70-80%, 80-90%, and 90-100%.

[0030] In another embodiment, the UVC on state in the method is a UVC time interval of 1 second to 300 seconds (with UVA off), and the UVA on state is a time interval of 1 hour to 10 days (with UVC off). The UVC on / off and UVA on / off time intervals depend on factors such as the power rating of the UV light source, the target pathogen, the location of the pathogen, the level of the pathogen, and the type of pathogen.

[0031] In another embodiment, the UVA light source can suppress pathogen growth and maintain a level that is safe for humans and other animals, and when pathogen suppression reaches its limit, the UVC light source can be turned on at intervals that maintain low pathogen levels.

[0032] As used herein, the term pathogen is intended to include bacteria, viruses, yeasts, protozoa, molds, and combinations thereof.

[0033] In another embodiment, the pathogen is a pathogen selected from the group consisting of E. coli K12, S. Epidermis, and B. Subtilis.

[0034] As used herein, the term "surface" refers to surfaces commonly found in public places such as bathrooms and kitchens, including but not limited to countertops, hard and wooden countertops, concrete surfaces, rubber surfaces, leather surfaces, and material surfaces. [Prior art documents] [Non-patent literature]

[0035] [Non-Patent Document 1] Bolton, JR and Linden, KG (2003) Standardization of Methods for Fluence (UV Dosage) Determination in Bench-Scale UV Experiment. Journal of Environmental Engineering 129(3)209-215 [Non-patent document 2] Haas, CN (2015) Microbial Dose Response Modeling: Past, Present and Future. Environmental Science and Technology 49 1245-1259 [Non-patent document 3] Watanabe, T. et al. (2010) Development of a Dose-Response Model for SARS Coronavirus. Risk Analysis 30 7 [Non-patent document 4] Du Pont, LH et al. (1971) Pathogenesis of Escherichia coli Diarrhea. The New England Journal of Medicine 285 1-9 [Non-Patent Document 5] Nishikawa-Nonaka, R. et al. (2018) Irradiation by ultraviolet light-emitting diodes influenza a viruses by inhiting replication and transcription of viral RNAin host cells Journal of Photochemistry and Photobiology B:Biology 189 193-200 [Non-patent document 6] Keil,SDBowen,R.and Marschner,S.(2016)Inactivation of Middle East respiratory syndrome coronavirus (MERS-CoV)in plasma products using a riboflavin-based and ultraviolet light-based photochemical treatment.Transfusion 56 2948-2952 [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is a block diagram illustrating a system according to one embodiment. [Figure 2] FIG. 2 is a block diagram showing a system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0037] Referring to FIG. 1, this figure is a block diagram illustrating one pulse width modulation (PWM) implementation of the system disclosed herein. A PWM generator 10 generates a single continuous PWM signal that is input to two circuits. The first circuit is a logic buffer circuit 20, optionally used to control the pulsing of a UVC light source 40. This logic buffer circuit 20 ensures that the UVC light source 40 is on when the PWM generator 10 outputs a high logic level and that the UVC light source 40 is off when the PWM generator 10 outputs a low logic level. See output curve 22. The second circuit is a logic inverter 30 that controls a UVA light source 50, ensuring that the UVA light source is off when the PWM generator 10 outputs a high logic level and that the UVA light source is on when the PWM generator 10 outputs a low logic level. See inverted output curve 32.

[0038] Referring to FIG. 2, this figure is a block diagram illustrating another embodiment of a timer-controlled system. In this embodiment, a UVC timer circuit 100 and a UVA timer circuit 200 control a UVC light source 40 and a UVA light source 50, respectively. The UVC timer circuit 100 is set to an on state for 150 seconds, and the UVA timer circuit 200 is set to a 6-hour state. At startup, the UVC timer circuit 100 is enabled and outputs a high logic level, which is sent to a first logic buffer 110 and a first logic inverter 120. The first logic buffer 110 controls the UVC light source 40 to an on state, while the first logic inverter 120 ensures that the UVA timer circuit 200 is off. When the UVC timer circuit 100 completes its 150-second on state, its output changes state, turning the UVC light source 40 off and the UVA timer 200 on for 6 hours. Once armed, UVA timer circuit 200 outputs a logic high state that is sent to second logic buffer 130 and second logic inverter 140. Second logic buffer 130 controls UVA light emitter 50 to an on state, while second logic inverter 140 is used to ensure UVC timer circuit 100 is in an off state. After six hours, the output changes state, turning UVA light emitter 50 off and UVC timer circuit 100 on, followed by UVC light emitter 40 on for 150 seconds. This cycle is repeated as necessary. Each time value depends on a variety of factors, including the pathogen to be eliminated, the power level of the UV light source, and the size of the room.

[0039] Example 1

[0040] Research into UVC LED-only suppression

[0041] The FLS UV Tool program was used to calculate the effectiveness of UVC LEDs in reducing bacteria levels in an enclosed space measuring 3m x 3m x 3m. Nine UVC LEDs, each with a wavelength of 275nm and a rated power of 244.2mW, were tested for a 20% bacteria reduction rate at various distances (floor level, 2m above floor) from the light source on the ceiling of the enclosed space (3m from the floor) and safety to human eyes and skin.

[0042] Each UVC LED was placed equidistant from the other on the ceiling of the room, resulting in a 3 × 3 array of UVC LEDs. The radiation angle of each UVC LED was 135° (FWHM*).

[0043] *LED beam angle, or commonly referred to as LED viewing angle, measures the usable light emitted from an LED source. Most commonly, beam angle is determined using one of two methods: the first method determines the angle at which 50% of the peak intensity is reached on either side of the emitting source; the second method determines the angle at which 10% of the peak intensity is reached on each side of the emitting source. The most commonly used method is the Full Width, Half Maximum (FWHM) for 50% intensity. For example, if an LED is measured to have 50% intensity at 15°, the viewing angle (FWHM) is considered to be 30°.

[0044] Based on the above parameters, the amount of time required for UVC to reduce pathogens by 20% at floor level (i.e., 3 m from the light source) was tested for the following pathogens: JPEG0007756930000001.jpg233153 JPEG0007756930000002.jpg37143

[0045] UVC alone required 9 minutes and 3 seconds to suppress all bacteria by 20%.

[0046] The maximum exposure time for humans at a safe level was also measured at 1 m from the light source for wavelengths including the UVC LED wavelengths investigated.

[0047] JPEG0007756930000003.jpg5761

[0048] In experiments using only UVC LEDs, a 20% reduction in bacteria levels required 9 minutes and 3 seconds, exceeding the maximum safe time of 3 minutes and 26 seconds.

[0049] Example 2

[0050] Research on UVA LED-only suppression

[0051] Nine UVA LEDs, each with a wavelength of 405 nm and a rated power of 1000 mW, were tested for their effectiveness in inhibiting bacterial growth at levels that are safe for human eyes and skin at various distances from the light source (floor level, 1 m above floor level, and 2 m above floor level) for a period of 40 hours in a test room measuring 3 m x 3 m x 3 m.

[0052] The UVA LEDs were placed equidistant from each other on the ceiling of the room, resulting in a 3 × 3 array of UVA LEDs. The radiation angle of each UVC LED source was 120° (FWHM).

[0053] This study also used the pathogens from Study 1.

[0054] UVA LEDs were used as described above to inhibit pathogens as follows. JPEG0007756930000004.jpg249154

[0055] The amount of time required for 20% inhibition is at least 23 hours.

[0056] The safe level was measured 1 m from the light source. JPEG0007756930000005.jpg128165

[0057] The suppressive effect of UVA alone exceeds the safety limit in 7 minutes and 45 seconds.

[0058] Example 3

[0059] Research using UVC pulses

[0060] The FLS UVTool software program was used to calculate the effectiveness of pulsed (on for a period, off for a period) UVC LEDs at suppressing bacterial levels in an enclosed space measuring 3m x 3m x 3m. Nine UVC LEDs, each with a UVC wavelength of 275nm and a rated power of 244.2mW, were tested for 20% bacterial suppression and safety to human eyes and skin at various distances (floor level, 2m above floor level) from the light source installed on the ceiling of the enclosed space (3m above floor level).

[0061] Each UVC LED was placed equidistant from the other on the ceiling of the room, resulting in a 3x3 array of UVC LEDs. The light source emission angle of each UVC LED was 135° (FWHM). Each UVC LED was pulsed on for 150 seconds at a time, and pathogen levels were measured. The time required for 20% inhibition was then calculated based on the percent inhibition at 150 seconds.

[0062] JPEG0007756930000006.jpg249142JPEG0007756930000007.jpg58151

[0063] The safe level was measured 1 m from the light source. JPEG0007756930000008.jpg143160

[0064] As shown above, pulsing UVC at 150 second intervals while keeping it on stays within the safety limits and meets the 20% suppression level.

[0065] Example 4

[0066] UVA growth suppression effect after UVC pulse application

[0067] The FLS UVTool software program was used to calculate the effectiveness of pulsed (on for a period, off for a period) UVA LEDs on suppressing bacterial levels in an enclosed space measuring 3m x 3m x 3m after exposure to UVC light as described above in Example 3. Nine UVC LEDs, each with a UVA wavelength of 405nm and a rated power of 20mW, were tested for bacterial suppression and safety to human eyes and skin at various distances (floor level, 2m above floor level) from the light source mounted on the ceiling of the enclosed space (3m above floor level).

[0068] The UVA LEDs were placed equidistant from each other on the ceiling of the room, resulting in a 3x3 array of UVC LEDs. The light source angle of each UVA LED was 120° (FWHM). Each UVA LED was pulsed on (alternating with UVC pulses) for 6 hours at a time, and pathogen levels were measured. JPEG0007756930000009.jpg216128 JPEG0007756930000010.jpg87129

[0069] UVA was used to inhibit the growth of the bacteria.

[0070] The safety levels 1m below the light source are shown below. JPEG0007756930000011.jpg52170

[0071] The combined use of UVA / UVC maintained growth inhibition without exceeding the safe level.

[0072] The levels of Anthrax Spores on surfaces in a room measuring 3m x 3m x 3m measured according to the above conditions in UVC Pulsed On / Off and UVA Pulsed On / Off conditions using the conditions in Examples 3 and 4 are shown in the table below. TIFF0007756930000012.tif158138 JPEG0007756930000013.jpg248147 JPEG0007756930000014.jpg250145 JPEG0007756930000015.jpg248138 JPEG0007756930000016.jpg248143 JPEG0007756930000017.jpg248145 JPEG0007756930000018.jpg249147 JPEG0007756930000019.jpg250148 JPEG0007756930000020.jpg249145 JPEG0007756930000021.jpg250149 JPEG0007756930000022.jpg249146 JPEG0007756930000023.jpg249148 JPEG0007756930000024.jpg16145

[0073] As can be seen, pulsing UVC light on kills bacteria to a certain level; pulsing UVA light on and pulsing UVC light off maintains the same bacterial level with no growth. Pulsing UVA light off and UVC light on then further kills bacteria; turning UVC light off and then UVA light on again maintains a new, lower bacterial level on the surface, further suppressing growth. This pulsing on / off method can reduce bacterial levels on surfaces by approximately 20% in 12-18 hours and suppress bacterial growth for at least 24 hours, while maintaining radiation levels safe for humans.

[0074] Example 5

[0075] UVA / UVC driving method compared to no UV against E. coli K12

[0076] Abbreviation

[0077] ATP: adenosine triphosphate, CFU: colony forming units, RLU: relative light units, SEM: standard error of the mean, TNTC: too many to calculate, UVA: ultraviolet A, UVC: ultraviolet C

[0078] raw material

[0079] Agar plates, maximum recovery dilution, violet-red bile salts agar and tryptone soy agar from Oxoid Ltd. (Basingstoke, Hampshire, UK); Petri dishes from Scientific Lab Supplies Ltd. UK; UlraSnap TM Adenosine triphosphate (ATP) surface test kits were purchased from Hygiena International Ltd. and for E. coli K12 from Blades Biological Ltd. (East Sussex, UK).

[0080] Device JPEG0007756930000025.jpg5079

[0081] Scheme of the device construction (not to scale). The two buttons on the control box represent the UVA and UVC switches. The lamp was placed 32 cm away from the Petri dish.

[0082] The device was housed in a Syngene Bioimaging light box to prevent exposure to UVA and UVC light. The wires from the lamp were wrapped around the clamp stand to ensure the lamp fully exposed the Petri dish. The lamp was positioned 32 cm from the Petri dish. The lamp and control box were from Helios. An Eclipse 17 was used as an autoclave, and a Genlab incubator was used for microbial culture. The box temperature was maintained at room temperature. A Hygiena luminometer was used for ATP readings.

[0083] experiment

[0084] Microorganisms and culture methods

[0085] The test microorganism was E. coli K12. The agar was sterilized at 121°C. The microorganism was grown on tryptone soy agar broth and incubated at 37°C for 12 hours. Violet-red bile salts agar was used to test E. coli K12. The maximum recovery dilution was autoclaved prior to use. E. coli K12 was diluted to 1 / 10,000 in the maximum recovery dilution to allow enumeration using the lawn plate approach. After transferring 10 μL of E. coli K12 to four different areas on nutrient 3 agar plates under sterilized conditions, the plates were stored under one of three conditions: low light, natural light, or UV light. Details regarding UV exposure are described in Protocol I and Protocol II. After exposure, the plates were incubated at 37°C for 24 hours, and colonies were counted.

[0086] Protocol I

[0087] Untreated media was exposed to natural light and dark conditions.

[0088] Protocol II

[0089] The UVA (nominal wavelength: 405 nm) was set to an output intensity of 42 mW, and the UVC (nominal wavelength: 275 nm) was set to an output intensity of 117 mW. The UVA was quenched with UVC for 3 minutes, and then UVA was quenched with UVC for 30 minutes. A total of 10 to 13 cycles were completed for this procedure. The total exposure times were 330 and 429 minutes, respectively.

[0090] ATP measurement

[0091] ATP measurements were performed when no visible colonies were present. TMThe swab was allowed to equilibrate at room temperature. The surface of the Petri dish was thoroughly wiped. The swab was placed back into the tube, and the tube was inserted into the Hygiena Luminometer within 30 seconds to record the ATP level. A reading of less than 10 relative light units (RLU) was considered clean. A reading of 11-29 RLU indicated a warning, and a reading of 30 RLU or greater indicated a dirty surface.

[0092] CFU rating

[0093] Colony forming units (CFU) are counted based on the number of viable bacterial cells. This counting was performed with the aid of a microscope. The number of bacteria per mL of sample is calculated by dividing the number of colonies by the dilution factor used. This is a direct counting method.

[0094] result

[0095] The survival status of E. coli K12 was monitored over different time periods.

[0096] Protocol I

[0097] The observed bacterial growth was too numerous for counting (TNTC) on the low-light and natural-light plates, so colony-forming unit (CFU) numbers could not be determined. ATP measurements were performed to assess the surfaces. JPEG0007756930000026.jpg35107

[0098] Table 1: ATP measurements in RLU under low light and natural light conditions

[0099] The difference in bacterial levels between dark and natural light conditions is due to the small differences in temperature and light exposure, resulting in diurnal variations.

[0100] Protocol II

[0101] After three rounds of 13 replicates of Protocol II above, a 32 ± 3% (mean ± standard error of the mean (SEM)) reduction in CFU was observed compared to bacteria stored in natural light. These values ​​vary with different pulse distances, intensities, and durations. JPEG0007756930000027.jpg62135

[0102] Table 2. Summary of the effect of UV Protocol II on bacterial load over 13 cycles.

[0103] After 10 cycles of the above protocol, a 6% reduction in bacterial load was observed when compared to bacteria exposed to low-intensity UV light, demonstrating the difference that shorter exposure times to UV light using this pulsing sequence make. JPEG0007756930000028.jpg40134

[0104] Table 3 Comparison of conditions (natural light vs. low light) for data from 13 cycles

[0105] Thirteen 33-minute light cycles (Protocol II) were observed to reduce bacterial load by 32 ± 3%. Compared to controls exposed to natural and low-intensity light, Protocol II reduced bacterial load by 35 ± 12%.

[0106] Example 6

[0107] UVA / UVC pulsed irradiation on E. coli K12, Bacillus subtilis and Staphylococcus epidermis

[0108] In this example, UVA and UVC irradiation of bacterial strings was investigated using modeling to consider the effect of UVA and UVC pulsing on bacterial strings considering various power settings and times, and considering various distances and exposure times, and to assess the risk of cross-contamination after exposure to UV light.

[0109] raw material

[0110] Agar, maximum recovery dilution, violet red bile salts agar and tryptone soy agar from Oxoid Ltd. (Basingstoke, Hampshire, UK); bent Petri dishes from Scientific Lab Supplies Ltd. UK; UlraSnap TM Adenosine triphosphate (ATP) surface test kits were purchased from Hygiena International Ltd. Escherichia coli K12, Bacillus subtilis and Staphylococcus epidermis were purchased from Blades Biological Ltd. (East Sussex, UK).

[0111] Device JPEG0007756930000029.jpg5491

[0112] Scheme of the apparatus construction (not to scale). The blue (outlined) box indicates the housing of the apparatus within the light box. The two green buttons on the control unit indicate the UVA and UVC switches. The lamp was placed 32 cm away from the Petri dish.

[0113] The apparatus was housed in a Syngene Bioimaging light box to prevent exposure to UVA and UVC. Wires from the lamp were wrapped around the clamp stand to ensure the lamp fully exposed the Petri dish. All experiments were performed with the lamp positioned 32 cm from the Petri dish, unless the distance was changed. UVA and UVC exposure dials were used for direct exposure. Controls included a total of 16 different settings for the lamp. The apparatus was assembled at Nottingham Trent University, UK.

[0114] The entire apparatus was sterilized using an autoclave (Eclipse 17) and growth was carried out using a Genlab incubator maintained at 37°C throughout the duration of the experiment. The temperature of the box was maintained at room temperature, varying between 18°C ​​and 25°C. A Hygiena luminometer was used for ATP readings.

[0115] The experimental design was similar to that described by Bolton, JR and Linden, KG (2003) (Standardization of Methods for Fluence (UV Dosage) Determination in Bench-Scale UV Experiment. Journal of Environmental Engineering 129(3)209-215).

[0116] This research paper outlines the importance of standardizing UV laboratory bench-scale setups and raises one of the most important points: the only missing attributes from the experimental setup described in this paper are the use of agitators and Petri dishes (Bolton and Linden 2003), which are recognized as methodologically inappropriate due to the use of a lawn-based medium approach.

[0117] experiment

[0118] Microorganisms and culture methods

[0119] Test organisms included E. coli K12, B. subtilis, and S. epidermidis. Agar and violet-red bile salts agar were prepared according to the manufacturer's protocol and sterilized at 121°C and 110.4 kPa for 1 hour. Both types of agar were poured into individual vented Petri dishes, allowed to dry, harden, and stored at 4°C prior to use. The organisms (B. subtilis and S. epidermidis) were cultured in tryptone soy agar and incubated at 37°C for 12 hours. E. coli K12 was confirmed using VRBG agar by the streaking method. B. subtilis and S. epidermidis were also confirmed using agar. Maximum recovery dilutions were autoclaved prior to use. E. coli K12, B. subtilis, and S. epidermidis were diluted 1 / 10,000 with the maximum recovery dilution solution to allow counting using the lawn plate approach. E. coli K12 was pipetted in 10 μL aliquots onto different areas of sterile nutrient 3 agar plates. The agar plates were stored under one of three conditions: low-intensity light, natural light, or UV light for different periods of time. Details regarding UV exposure, exposure time, and distance from the UV lamp are described in Protocol I and Protocol II below. After exposure, the plates were incubated at 37°C for 24 hours, and colonies were counted. ATP measurements were performed when bacteria were too numerous to count (TNTC).

[0120] Protocol I

[0121] UVA and UVC were used simultaneously on agar plates for 12 hours at various power levels, including 42mW, 117mW, and 65mW. This was done for all microorganisms tested, including E. coli K12, B. subtilis, and S. epidermidis. The bacteria were then incubated for 24 hours before data collection.

[0122] Protocol II

[0123] UVA and UVC were pulsed using power levels of 42mW and 65mW, respectively. The UVC was turned on for 3 minutes and then quenched. The UVA was then turned on for 30 minutes and then quenched. This was repeated 10-13 times, for a total exposure time of 270 and 399 minutes, respectively. The bacteria were then grown for 24 hours and data were acquired. This was performed for E. coli K12 and S. epidermidis strains.

[0124] ATP measurement

[0125] ATP measurements were performed when no colonies were observed on the agar plate or when the bacterial colonies were TNTC. TM The swabs were equilibrated at room temperature (UltraSnap TM The swabs were stored at 21°C. The surface of the Petri dish was thoroughly disinfected with the swab, especially the center of the plate where the bacteria had been directly pipetted. The swab was then placed back into the tube and placed in the UltraSnap TM A liquid stabilizing reagent was added from the swab. The purpose of adding the liquid stabilizing reagent is to accelerate the bioluminescent reaction and optimize sample recovery. This specialized liquid stabilizing reagent ensures excellent sensitivity and reliable results, achieving a sensitivity of 0.001 fmol. The tube was inserted into the Hygiena luminometer within 30 seconds, and ATP levels were recorded using novel solid-state photodiodes. These photodiodes can detect and qualify low light levels. The light emitted is directly proportional to the amount of ATP present in the sample. A reading of less than 10 relative light units (RLU) indicates cleanliness. A reading between 11 and 29 RLU indicates a warning condition, and a reading of 30 RLU or greater indicates an unclean condition. ATP is used in food production and healthcare settings to determine whether a surface is clean.

[0126] Modeling cross-contamination risks

[0127] Dose-response models have been introduced to assess cross-contamination risk. These models help understand the implications of pathogen exposure and are important for risk assessment (Haas, CN (2015) Microbial Dose Response Modeling: Past, Present and Future. Environmental Science and Technology 49 1245-1259). An exponential distribution has been developed (Watanabe. Risk Analysis 30 7) and classified as a Generation 1 model, i.e., a model that describes the probability of response to an exposed dose (Haas 2015).

[0128] p(d)=1-e (-d / k)

[0129] In the above equation, p(d) is the risk of disease at a dose, and k is a parameter specific to the pathogen (Watanabe et al. 2010). Parameter k is the probability that a single pathogen will initiate a response (Watanabe et al. 2010). Parameter k occurs for each microorganism (Watanabe et al. 2010). This exponential model can be applied to assess the risk of cross-contamination.

[0130] Results and Discussion

[0131] Both Protocol I and Protocol II were used to monitor survival of E. coli K12, B. subtilis and S. epidermidis over different time periods.

[0132] Protocol I

[0133] Because bacterial growth observed was TNTC for E. coli K12, B. subtilis, and S. epidermidis on low-light and natural-light plates, colony-forming unit (CFU) counts could not be determined. Furthermore, bacteria were not visible to the naked eye for all strains tested. Therefore, ATP measurements were performed to evaluate surfaces and assess residual bacteria, if present, and if the surface was contaminated. JPEG0007756930000030.jpg114161

[0134] Table 4: ATP (RLU) measured under low light, natural light, and UV light conditions using different UVA and UVC power levels, F, 42 mW, and 65 mW, for different bacterial strains E. coli K12, B. subtilis, and S. epidermis.

[0135] These results demonstrate that the combined use of UVA and UVC light at output levels of 42 mW, 117 mW, and 65 mW is as effective at killing bacteria as those shown above (Table 4). The difference in levels of low-intensity light and natural light disinfection is within the diurnal variation due to small variations in temperature and natural light exposure. In conclusion, using any of the UVC and UVA output levels, we can achieve nearly 100% ATP reduction over a 12-hour period, demonstrating that we are within the cleanliness limit of 10 RLU. This is demonstrated using three different bacterial strains, including Coli K12, S. subtilis, and B. epidermis.

[0136] Protocol II

[0137] Distance measurement JPEG0007756930000031.jpg79103

[0138] Graph 1 shows the difference (%) in the ratio of bacterial load to distance from the lamp bacteria when comparing UV light with natural light (blue) and low-intensity light (gray) conditions using E. coli K12 as a common model.

[0139] After 13 repetitions of the above protocol, a 32 ± 3% mean ± standard error (SEM) reduction in CFU was observed when comparing bacteria stored in natural light at a distance of 32 cm with bacteria exposed to UV light (Graph 1). The 13 repetitions included a total of 39 minutes of UVC exposure and 360 minutes of UVA exposure. These values ​​may vary considering different intensities. Additionally, after 13 repetitions of the above protocol, a 35 ± 8% mean ± standard error (SEM) reduction in CFU was observed when comparing bacteria stored in low-intensity light at a distance of 32 cm with bacteria exposed to UV light (Graph 1). These findings were obtained using E. coli K12 as a common model microorganism using n = 36 readings. Similar findings were observed for S. epidermis. Using the same power levels as above, a 36 ± 2% (mean ± SEM) reduction in CFU was observed when comparing bacteria stored in low-intensity light at a distance of 32 cm with bacteria exposed to UV light. Similar findings were observed when comparing CFU of S. epidermis in light and UV conditions, with a 34 ± 5% (mean ± SEM) reduction in bacteria exposed to UV light, using a total reading of n = 86. This indicates that microorganisms, i.e., bacteria, behave similarly toward different lighting conditions, consistent with findings demonstrated in Protocol I.

[0140] Furthermore, we investigated the effect of distance using a common model microorganism, bacteria, and found that the distance between the lamp and the Petri dish affected growth rate (see above). This graph shows the findings of n=207 readings. The closer the lamp was to the Petri dish, the more pronounced the decrease observed (Graph 1). The average SEM level for these measurements was 4%. This indicates that as the distance decreases, e.g., from 26 cm to 22 cm, some overlap in the readings occurs. Overall, Graph 1 shows a negative linear trend, with the decrease increasing the closer the lamp was to the Petri dish. The regression values ​​for light conditions (blue) show a trend with R2=0.9993. The closer the regression value is to 1, the stronger the relationship between these points. This demonstrates that distance from the lamp is dependent on bacterial growth.

[0141] Repeat number measurement

[0142] Furthermore, after repeating the above protocol 10 times, a 6% reduction in bacterial load was observed when comparing bacteria exposed to UV light with bacteria exposed to low intensity light. This was confirmed using E. coli K12 as a generic model with n=10 readings. This indicates that a difference can be made with shorter exposure times to UV light using this pulse drive train and power level.

[0143] Response modeling for cross-contamination risk

[0144] With the data acquired, a suitable model is prepared to assess the risk of cross-contamination. Using the exponential model described above, the effect of pulsed UV at a distance of 32 cm was examined with 39 iterations. k=9.7×10 -9(Du Pont, LH et al. (1971) Pathogenesis of Escherichia coli Diarrhea. The New England Journal of Medicine 285 1-9) Using E. coli K12, a pulsed UVA and UVC program was implemented, and it was found that the risk of cross-contamination of C. coli K12 was reduced by 50%.

[0145] This technique has the potential to be applied to RNAs that are specifically important for viruses. The effectiveness of UV has been demonstrated in other viral models, such as influenza (Nishikawa-Nonaka, R. et al. (2018) Irradiation by ultraviolet light-emitting diodes inhibits replication and transcription of viral RNA in host cells. Journal of Photochemistry and Photobiology B:Biology 189 193-200). Recently, it has also been shown that coronaviruses, particularly MERS-CoV, are susceptible to UV light and can be inactivated after exposure (Keil, S.D.; Bowen, R. and Marschner, S. (2016) Inactivation of Middle East respiratory syndrome coronavirus (MERS-CoV) in plasma products using a riboflavin-based and ultraviolet light-based photochemical treatment. Transfusion 56 2948-2952).

[0146] Pulsed UVA and UVC sequences have also been shown to have the potential to reduce bacterial loads, particularly for E. coli K12, S. epidermis, and B. subtilis. A 12-hour exposure time with UVA and UVC was observed for all strains, particularly when combined with different power levels, specifically 65 mW (UVC), 42 mW (UVA), and 117 mW (UVC). Furthermore, pulsed experiments using UVA at 42 mW and UVC at 65 mW showed a reduction in E. coli K12 and S. epidermis at a distance of 32 cm compared to natural light and low-light conditions. Furthermore, UV lamp distance also affected bacterial growth, demonstrating a relationship with an R2 of 0.9993. Modeling also revealed a 50% reduction in the risk of cross-contamination.

[0147] The matter disclosed herein is intended to be illustrative and not restrictive, as many changes can be made in the preferred embodiment of the invention without departing from the scope of the invention. [Explanation of symbols]

[0148] 10 PWM generator 20 Logic buffer circuit 22 Power curve 30 inverters 32 Inverted Output Curve 40 UVC light emitter 50 UVA light source 100 UVC timer circuit 110 First Logical Buffer 120 First Logic Inverter 130 Second Logical Buffer 140 Second Logic Inverter 200 UVA timer circuit

Claims

1. 1. A UVA / UVC system for reducing the level of at least one pathogen on a surface and inhibiting further growth of at least one pathogen on said surface, said UVA / UVC system having no harmful effects on human eyes, comprising: i) said surface ii) at least one UVA light source at least 22 centimeters away from the surface; iii) at least one UVC light source at least 22 centimeters away from the surface; and iv) at least one controller connected to each of the at least one UVA light source and the at least one UVC light source, the controller controlling at least one parameter of each of the UVA light source and the UVC light source selected from light source, light intensity, radiation output level, wavelength, exposure time, and a plurality of these; wherein said at least one UVC light source emits UVC light onto said surface for a time period sufficient to reduce the level of said at least one pathogen to a level safe for humans, and said at least one UVA light source emits UVA light onto said surface for a time period sufficient to inhibit growth of said at least one pathogen on said surface, said at least one UVC light source and said at least one UVA light source emitting light onto said surface for said time period, and wherein radiation levels from said at least one UVC light source and said at least one UVA light source are maintained at a level safe for humans in a public place; turning off the at least one UVA light source when the at least one UVC light source is emitting UVC light at the surface, and turning off the at least one UVC light source when the at least one UVA light source is emitting UVC light at the surface, and controlling a repeating cycle between the at least one UVC light source and the at least one UVA light source with the at least one controller; the at least one UVA light source has an operating wavelength of about 385 nanometers (nm) to about 405 nm, the at least one UVA light source has a rated power of about 10 mW to about 100 W, the at least one UVC light source has an operating wavelength of about 275 nm to about 295 nm, and the at least one UVC light source has a rated power of about 10 mW to about 100 W, the rated power of the UVA light source is maintained constant during the exposure time that suppresses growth of the at least one pathogen on the surface, and the rated power of the UVC light source is maintained constant during the exposure time that maintains low levels of the at least one pathogen on the surface, and the exposure time for irradiating each of i) the UVA light source and ii) the UVC light source is adjusted on and / or off based solely on time.

2. 10. The system of claim 1, wherein said at least one UVC light source has an operating wavelength of about 275 nm.

3. 3. The system of claim 1 or claim 2, wherein said at least one UVA light source has an operating wavelength of about 385 nm to about 405 nm, or said at least one UVA light source has an operating wavelength of about 405 nm.

4. The system of any one of claims 1 to 3, wherein said at least one UVC light source is a light emitting diode (LED).

5. The system of any one of claims 1 to 4, wherein said at least one UVA light source is an LED.

6. 6. The system of any one of claims 1 to 5, wherein the at least one controller automates repeated cycling between emission from the at least one UVA light source and emission from the at least one UVC light source.

7. 10. The system of claim 1, wherein said at least one UVC light source emits light at a power level and for a duration that reduces at least one pathogen on said surface exposed to said at least one UVC light source.

8. 2. The system of claim 1, wherein said power level is selected to ensure that radiation emissions from said at least one UVC light source are maintained at a level that is safe for the human eye.

9. 2. The system of claim 1, wherein said time is selected to ensure that radiation emitted from said at least one UVC light source is maintained at an exposure time that is safe for the human eye.

10. The system described in claim 1, wherein the at least one UVA light source emits light at an output level that inhibits the growth of at least one pathogen on the surface exposed to the at least one UVC light source.

11. 10. The system of claim 1, wherein said at least one UVC light source has a power rating of 244 mW.

12. 10. The system of claim 1, wherein said at least one UVA light source has a power rating of 20 mW.

13. 13. The system of any one of claims 1 to 12, wherein the system reduces the level of at least one pathogen on the surface exposed to the system by 1 to 100%, alternatively by 10 to 20%.

14. The system according to any one of claims 1 to 13, which inhibits at least one pathogen selected from the group consisting of E. coli K12, S. epidermis, and B. subtilis.

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