The Efficiency of UVB Radiation Transmission Through Various Plastic

The Efficiency of UVB Radiation Transmission Through Various Plastic Acrylics and Wraps • • • Introduction Vitamin D3 Figure 1: Peak wavelength spectrum for LEDs. • • • Results Vitamin D is essential for calcium absorption to maintain bone health and is related to decreased risk of cancers and cardiovascular diseases. Vitamin D can be acquired through certain foods (fatty fish, etc), supplementation or through cutaneous production after solar or artificial Ultraviolet B (UVB) exposure. In the skin, UVB radiation converts 7‐dehydrocholesterol to previtamin D3 which then is thermally isomerized to Vitamin D3, also producing byproducts of lumisterol and tachysterol (Figure 2). The optimum wavelength for the LED device for vitamin D production is 293 nm, which was found to be 2.4 times more efficient in converting 7‐DHC to previtamin D3 in human skin than the sun. The peak wavelength for the LED used is 295 nm. Figure 2. 7‐ Figure 8: A) The chromatograph of the control ampoule at 280 nm, showing peaks of 7‐DHC and previtamin D, as well as photoproducts lumisterol and tachysterol. B) The chromatograph of ampoule cover with 125 micron acrylic from Evonik. C) The chromatograph of ampoule covered with 140 micron acrylic from Evonik. 7‐DHC Lumisterol B 7‐DHC dehydrocholesterol is converted to previtamin D3 after UV radiation, which is then converted to vitamin D3 with heat, and byproducts lumisterol and tachysterol. Tachysterol Previtamin D Lumisterol Those with fat malabsorption syndromes such as Crohn’s disease, cystic fibrosis, inflammatory bowel disease, and gastric bypass surgery are at a high risk of vitamin D3 deficiency and would benefit from producing vitamin D3 in their skin to satisfy their needs rather than take supplementation. Therefore, these patients would benefit from either solar or artificial UVB radiation. Recently, LEDs have been designed to transmit UVB radiation. The goal is to design an LED device that can be used to treat vitamin D deficiency in patients w fat malabsorption. The design of the device includes some type of material that protects the LED when placed next to human skin. That material needs to have transmission properties that permit UVB to transmit through. C 7‐DHC Previtamin D Tachysterol Lumisterol The device will need a plastic acrylic to house the LED lights to protect the skin as well as a replaceable plastic wrap to switch after every use, so oils from the body do not build up on it. These plastics must still allow UVB radiation to pass through and convert 7‐dehydrocholesterol to pre‐vitamin D3. The only compounds that absorb UVB radiation entirely are those with conjugated double bonds, thus this structure must be avoided in choosing the plastics. Thus, the composition of a plastic housing 4 of the LED must be devoid of these chemicals. UV spectrum of previtamin D Objective 120 UV spectrum of 7‐dehydrocholesterol Conversion of 7‐DHC to Previtamin D and Photoproducts of Control compared to Various Plastic Acrylics with UV Sperti Lamp Methods * * * * * 80 * Figure 14. Structure of Polyethylene, which contains no double bonds. 60 40 20 Irradiation of Ampoule under UV lamp at 10 MEDs with Acrylics and Saran Wraps 1. The plastic wrap (Gladwrap, Saran wrap, or Stretch‐tite) or plastic acrylic (Euoplex or Evonik Industries 80, 125, 140 or 240 microns) were placed evenly over a plastic frame containing three 7‐DHC ampoules (50 μg in methanol). (Figure 3A and 3B) Three 7‐DHC ampoules without any covering served as control. 2. All samples were irradiated 11.5 cm from the UV lamp (a Sperti lamp) for 15 minutes (10 Minimal Erythemal Doses [MED]). A MED is the minimal amount of UVB radiation required to turn the skin slightly pink after 24 hours. It is a standard for measuring biologic effect of UVB radiation in the skin. 0 Control Evonik 125 microns Evonik 80 microns Evonik 240 microns Evonik 140 microns Euoplex 80 microns Euoplex 125 microns Euoplex 80 microns Figure 9. Irradiated 7‐DHC ampoules under the UV lamp 11.5 cm from the lamp for 15 minutes, exposed to 10 MEDs. Statistical T‐testing showed the difference in the efficiency of the conversion of 7‐DHC to previtamin D3 between the acrylics was not significant. *= p<0.01 to control. Bars are means, percent of control 7‐DHC conversion to previtamin D3 and photoproducts, +/‐ standard deviation. n=3. Conversion of 7‐DHC to Previtamin D and Photoproducts of Control compared to Various Plastic Wraps with UV Sperti Lamp 120 Conversion of 7‐DHC to Previtamin D and Photoproducts of Control compared to Stretch‐tite wrap and Evonik 80 micron Acrylic with UV Sperti Lamp 120 * 100 * * Figure 3A and 3B. Ampoules Irradiated with 10 MEDs under UV lamp, 11.5 cm away and covered with plastic acrylic (2A) and plastic wrap (2B). 60 ** 80 ** 60 40 40 20 20 0 Control 0 Control Gladwrap Stretch‐tite Stretch‐tite plastic wrap Evonik 80 micron acrylic Stretch‐tite and acrylic Saran wrap Figure 10. 7‐DHC ampoules were irradiated under the UV lamp 10.5 cm from the lamp for 15 minutes, exposed to 10 MEDs. Statistical T‐testing showed the difference in conversion between the plastic wraps was not significant. *= p<0.01 to control. Bars are means, +/‐ standard deviation. n=3. Figure 11. 7‐DHC ampoules were irradiated under the UV lamp 24 cm from the lamp for 15 minutes, exposed to 3 MEDs. Statistical T‐testing showed the difference in conversion between the plastic wraps was not significant. *= p<0.05 to control, **=p<0.00001 to control. Bars are means, +/‐ standard deviation. n=3. Percent Conversion of 7‐DHC to Vitamin D3 in Skin Samples and Control Ampoules Irradiated with UVB LED 7‐DHC Conversion to Vitamin D3 and Photoproducts with Stretch‐tite wrap and Evonik 80 micron Acrylic Using UVB LED 5 120 1.5 MED 4.5 100 80 60 40 20 Percent Conversion of 7‐DHC 4 Percent 7‐DHC Conversion of Control Figure 4. 4 LEDs turned on. The red lights demonstrate that each of the LEDs was working. Figure 5: Ampoules placed directly on top of each LED with the combination of Stretch‐tite plastic wrap and Evonik Acrylic 80 microns, irradiated with 3 MEDs. HPLC Analysis of Ampoules 1. The solvent was dried with nitrogen gas. (Fig 6) 2. The sample was reconstituted in 1 mL of 0.8% isopropanol in hexane and transferred to vials for HPLC analysis. 3. Straight‐phase High Performance Liquid Chromatography was performed. Fig 6: Samples Drying with Nitrogen Gas. Percent of Control 80 Percent Conversion of Control * 100 Irradiation of Ampoules with UVB‐emitting LED or UV lamp 1. Evaluation of Plastic Wrap and Acrylics with Sperti UVB lamp: Stretch‐tite plastic wrap and Euoplex 80 micron acrylic were placed over plastic frame containing three 7‐DHC ampoules and exposed to 3 MEDs (24 cm away for 18 minutes). 2. Evaluation of the Plastic Acrylic and Plastic Wraps with UVB‐emitting LED: Stretch‐tite plastic wrap and Euoplex 80 micron acrylic were placed over the 295 nm LEDs and 7‐DHC ampoules were housed in a Styrofoam container and irradiated with 3 MEDs (0.5 cm away for 6 minutes). (Figure 5) • In figure 8, the peaks detected by the HPLC show presence of previtamin D and its photoproducts, lumisterol and tachysterol, in both the control and when the 125 and 140 micron acrylics from Evonik industries were placed between the ampoule and the UV source. The peaks are known to be previtamin D and 7‐DHC due to the UV spectra shown. Thus, the acrylics allow transmission of UVB radiation and facilitate conversion of 7‐DHC to previtamin D. • An evaluation of the thickness of acrylics from Evonik Industries and Euoplex shows no significant difference in the percent conversion of 7‐DHC to previtamin D and its photoproducts in each of the acrylics. The acrylics decreased the conversion of 7‐DHC by an average of 20%. This is in line with the report sent from the manufacturer about the transmission of UVB radiation in the acrylics. • Due to the fact the 7‐DHC conversion was unaffected by the thickness of the acrylics, it is likely the UVB radiation blocked by the plastic acrylics was reflected instead of absorbed. Further research is needed. • In all 3 types of plastic wrap (Gladwrap, stretch‐tite and saran wrap), there was no significant difference in 7‐DHC conversion to previtamin D and its photoproducts. On average, the plastic wraps blocked 10% of the 7‐DHC conversion to previtamin D. This could be due to UVB reflection or a contaminant in the plastic wraps. • In plastic wraps sold in the US, polyethylene is the main component. It is a structure with only single bonds, so it should not absorb any UV radiation, as it has no conjugated double bonds. However, some of the UVB radiation was blocked, suggesting a contaminant or reflection of UVB radiation. 100 To evaluate several commercially available acrylics plastic sheets and commonly used household transparent food wraps for their ability to transmit UVB radiation. Percent 7‐DHC conversion of control • A Tachysterol Previtamin D Discussion and Conclusion 3.5 0.75 MED 3 2.5 2 1.5 1 0.5 0 0 Figure 7: Skin Sample Irradiated by LED. Irradiation and Analysis of Skin Samples exposed to UVB LED 1. Surgically obtained (approved by BUMC institutional review board) type II human skin sample was placed in a quartz petri dish with the epidermis placed down. Samples were exposed for 0.75 (9 minutes) or 1.5 MEDs (18 minutes) with Stretch‐tite wrap and Evonik 80 micron acrylic (Fig 7). The skin sample was irradiated with 0.75 or 1.5 MEDs and then moved so another section of the skin was irradiated until all of the skin was irradiated. A 7‐DHC ampoule was processed in an identical fashion with the exception that Stretch‐tite wrap and the Evonik wrap was placed underneath the quartz petri dish. 2. Using heat separation, the epidermis was recovered from the sample by a heat separation technique. The epidermis was extracted and placed in a methanol solution. 3. The sample was placed in a 50 degree Celsius bath overnight and then centrifuged. 4. The sample was dried by nitrogen gas and reconstituted in 0.8% isopropanol in hexane and transferred to vials and placed into the HPLC. 5. Straight‐phase High Performance Liquid Chromatography was performed on 4.6x250 mm, 5μm Zorbax RX‐SIL column. Figure 11. 7‐DHC ampoules were irradiated under the UV lamp 24 cm from the lamp for 15 minutes, exposed to 3 MEDs. Bars are means, +/‐ standard deviation. n=3. Control Ampoule Human Skin Sample Control Ampoule Human Skin Sample Figure 12. Human skin samples and 7‐DHC ampoules were irradiated with 0.75 and 1.5 MEDs with an LED device. The human skin samples were also covered with Stretch‐tite plastic wrap and Evonik 80 micron acrylic. Vitamin D3 7‐DHC Figure 13. Chromatograph of human skin sample irradiated with 1.5 MEDs by LED device. Peaks of 7‐DHC and Vitamin D3 are labelled. UV Spectra of Vitamin D3 • In Figure 12, the human skin sample converted 7‐DHC to vitamin D3 after irradiation and heat overnight. Compared to the control ampoule, the 7‐DHC conversion in the human skin sample was reduced by 25% when irradiated with 1.5 MEDs. This is similar to the 30% reduction of 7‐DHC conversion to previtamin D found when using 7‐DHC ampoules with the same plastics under the Sperti UV lamp and also with the UVB LED. • Therefore, UVB‐emitting acrylic plastics and plastic wrappings may be a good source of materials for the planned Vitamin D producing LED device.