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Dr. Alka Ekka
Dr. Vijaya Gupta


Photosensitizer, Methylene Blue, Photocatalysis, Spectrophotometry


Background: The increasing environmental problems associated with traditional methods of water disinfection, such as chlorination, have prompted the hunt for sustainable substitutes. Photodynamic treatment (PDT) with photosensitizers has emerged as a viable approach to water purification due to its advantages over conventional approaches. The objective of this research is to evaluate the effects of immobilized photosensitizers, specifically potassium iodide (KI) and methylene blue (MB), on improved long-term water disinfection and bacterial inactivation.

Methods: When examining how photosensitizers affect bacterial inactivation, a methodical sequence of steps is utilized. Potassium iodide and methylene blue are co-extrusioned into a polymer matrix to create an efficient and safe immobilization procedure. The final beads undergo a thorough testing procedure that includes measurements of absorbance using UV-visible spectrophotometry, evaluation of photosensitizer leakage, and tests for antibacterial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria.

Findings: Examining photosensitizer in polymers reveals three different concentration gradients (C1, C2, and C3) with different amounts of methylene blue and potassium iodide. Following the deployment of the beads, data from the UV-visible spectrophotometer show an inverse relationship between absorbance and photosensitizer inclusion levels, with C1 showing the least inclusion and C3 the highest. Days 1 and 2 of the polymer matrix test show rapid leaking of photosensitizer, which is followed by a decrease in activity on the subsequent days. According to antibacterial activity tests, C1 is the concentration that works best for both types of bacteria, with C2 and C3 displaying different levels of potential for breakdown.

Conclusion: The study comes to the conclusion that immobilised photosensitizers are very effective at disinfecting water and inactivating germs, especially when potassium iodide is present. For photosensitizer immobilisation, the suggested co-extrusion approach works well and is both economical and ecologically benign. Reactive iodine species are produced in conjunction with potassium iodide, which is thought to have a synergistic impact that improves bacterial death during methylene blue photodynamic therapy. This creative method, which highlights the use of potassium iodide and immobilised photosensitizers in environmental stewardship, has the potential to advance sustainable water disinfection techniques.

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1. Braun Ang, L. Y., Lim, M. E., Ong, L. C., & Zhang, Y. (2011). Applications of upconversion nanoparticles in imaging, detection and therapy. Nanomedicine, 6(7), 1273-1288
2. Chong, M. N., Jin, B., Chow, C. W., & Saint, C. (2010). Recent developments in photocatalytic water treatment technology: a review. Water research, 44(10), 2997-3027.
3. Fotinos, N., Convert, M., Piffaretti, J. C., Gurny, R., & Lange, N. (2008). Effects on gram-negative and gram-positive bacteria mediated by 5-aminolevulinic acid and 5-aminolevulinic acid derivatives. Antimicrobial agents and chemotherapy, 52(4), 1366-1373.
4. García‐Fresnadillo, D. (2018). Singlet Oxygen Photosensitizing Materials for Point‐of‐Use Water Disinfection with Solar Reactors. ChemPhotoChem, 2(7), 512-534.
5. Hamblin, M. R., & Abrahamse, H. (2018). Inorganic salts and antimicrobial photodynamic therapy: mechanistic conundrums?. Molecules, 23(12), 3190.
6. Jiménez-Hernández, M. E., Manjón, F., García-Fresnadillo, D., & Orellana, G. (2006). Solar water disinfection by singlet oxygen photogenerated with polymer-supported Ru (II) sensitizers. Solar Energy, 80(10), 1382-1387.
7. Kasimova, K. R., Sadasivam, M., Landi, G., Sarna, T., & Hamblin, M. R. (2014). Potentiation of photoinactivation of Gram-positive and Gram-negative bacteria mediated by six phenothiazinium dyes by addition of azide ion. Photochemical & photobiological sciences, 13, 1541-1548.
8. Luz, P. P., Nobre, T. M., Serra, O. A., & Zaniquelli, M. E. (2011). Chitosan as a bioadhesive agent between porphyrins and phospholipids in a biomembrane model. Journal of Nanoscience and Nanotechnology, 11(2), 1278-1287.
9. Manjón, F., Garcáa-Fresnadillo, D., & Orellana, G. (2009). Water disinfection with Ru (II) photosensitisers supported on ionic porous silicones. Photochemical & Photobiological Sciences, 8, 926-932.
10. Nisnevitch, M., Lugovskoy, S., Pinkus, A., Nakonechny, F., & Nitzan, Y. (2014). Antibacterial activity of photosensitizers immobilized onto solid supports via mechanochemical treatment. Recent Research Developments in Photochemistry & Photobiology, Research Signpost, Kerala, India, 9.
11. Sabbahi, S., Alouini, Z., Ben Ayed, L., & Jemli, M. (2010). Inactivation of faecal bacteria in wastewater by methylene blue and visible light. Desalination and Water Treatment, 20(1-3), 209-219.
12. Thandu, M., Comuzzi, C., & Goi, D. (2015). Phototreatment of water by organic photosensitizers and comparison with inorganic semiconductors. International Journal of Photoenergy, 2015.
13. Vatansever, F., de Melo, W. C., Avci, P., Vecchio, D., Sadasivam, M., Gupta, A., ... & Hamblin, M. R. (2013). Antimicrobial strategies centered around reactive oxygen species–bactericidal antibiotics, photodynamic therapy, and beyond. FEMS microbiology reviews, 37(6), 955-989.
14. Vecchio, D., Gupta, A., Huang, L., Landi, G., Avci, P., Rodas, A., & Hamblin, M. R. (2015). Bacterial photodynamic inactivation mediated by methylene blue and red light is enhanced by synergistic effect of potassium iodide. Antimicrobial agents and chemotherapy, 59(9), 5203-5212.
15. Wagner, S. J., Skripchenko, A., Robinette, D., Foley, J. W., & Cincotta, L. (1998). Factors affecting virus photoinactivation by a series of phenothiazine dyes. Photochemistry and photobiology, 67(3), 343-349.