This work has received funding from the Center of Applied Nanomedicine, National Cheng Kung University from the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE), and Ministry of Science and Technology, Taiwan [MOST 109-2327-B-006-005] to TW Wong. J.H. Hung acknowledges funding from National Cheng Kung University Hospital, Taiwan [NCKUH-11006018], and [MOST 110-2314-B-006-086-MY3].

1. aPDT system preparation
<ol>
	<li>Cut four green light-emitting diodes (LEDs) from a LED strip (see Table of Materials) and align them with four wells of a 96-well plate (Figure 1). 
	NOTE: The LEDs were arranged into a 4 x 3 array. The back of the LED was adhered to a heat sink to disperse heat during irradiation.</li>
	<li>Measure the fluence rate11 of the LED at 540 nm with a light power meter (see Table of Materi...

<ol>
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N., Hsu, R., Chen, H., Wong, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Daylight+photodynamic+therapy:+an+update.">Daylight photodynamic therapy: an update.</a> Molecules. 25 (21), 5195 (2020).</li><li>Wainwright, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photodynamic+antimicrobial+chemotherapy+(PACT).">Photodynamic antimicrobial chemotherapy (PACT).</a> Journal of Antimicrobial Chemotherapy. 42 (1), 13-28 (1998).</li><li>Wong, T. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Indocyanine+green-mediated+photodynamic+therapy+reduces+methicillin-resistant+staphylococcus+aureus+drug+resistance.">Indocyanine green-mediated photodynamic therapy reduces methicillin-resistant staphylococcus aureus drug resistance.</a> Journal of Clinical Medicine. 8 (3), 411 (2019).</li><li>Kim, M. M., Darafsheh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+sources+and+dosimetry+techniques+for+photodynamic+therapy.">Light sources and dosimetry techniques for photodynamic therapy.</a> Photochemistry and Photobiology. 96 (2), 280-294 (2020).</li><li>Wong, T. W., Sheu, H. M., Lee, J. Y., Fletcher, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photodynamic+therapy+for+Bowen's+disease+(squamous+cell+carcinoma+in+situ)+of+the+digit.">Photodynamic therapy for Bowen's disease (squamous cell carcinoma in situ) of the digit.</a> Dermatologic Surgery. 27 (5), 452-456 (2001).</li><li>Wong, T. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photodynamic+inactivation+of+methicillin-resistant+Staphylococcus+aureus+by+indocyanine+green+and+near+infrared+light.">Photodynamic inactivation of methicillin-resistant Staphylococcus aureus by indocyanine green and near infrared light.</a> Dermatologica Sinica. 36 (1), 8-15 (2018).</li><li>Stasko, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visible+blue+light+inhibits+infection+and+replication+of+SARS-CoV-2+at+doses+that+are+well-tolerated+by+human+respiratory+tissue.">Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue.</a> Scientific Reports. 11 (1), 20595 (2021).</li><li>Crosbie, J., Winser, K., Collins, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+the+light+field+of+the+Waldmann+PDT+1200+lamp:+potential+for+wide-field+low+light+irradiance+aminolevulinic+acid+photodynamic+therapy.">Mapping the light field of the Waldmann PDT 1200 lamp: potential for wide-field low light irradiance aminolevulinic acid photodynamic therapy.</a> Photochemistry and Photobiology. 76 (2), 204-207 (2002).</li><li>Feenstra, R. P., Tseng, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+fluorescein+and+rose+bengal+staining.">Comparison of fluorescein and rose bengal staining.</a> Ophthalmology. 99 (4), 605-617 (1992).</li><li>Demidova, T. N., Hamblin, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+cell-photosensitizer+binding+and+cell+density+on+microbial+photoinactivation.">Effect of cell-photosensitizer binding and cell density on microbial photoinactivation.</a> Antimicrobial Agents and Chemotherapy. 49 (6), 2329-2335 (2005).</li><li>Shahid, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Duclauxin+derivatives+from+fungi+and+their+biological+activities.">Duclauxin derivatives from fungi and their biological activities.</a> Frontiers in Microbiology. 12, 766440 (2021).</li><li>Arendrup, M. C., Park, S., Brown, S., Pfaller, M., Perlin, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+CLSI+M44-A2+disk+diffusion+and+associated+breakpoint+testing+of+caspofungin+and+micafungin+using+a+well-characterized+panel+of+wild-type+and+fks+hot+spot+mutant+Candida+isolates.">Evaluation of CLSI M44-A2 disk diffusion and associated breakpoint testing of caspofungin and micafungin using a well-characterized panel of wild-type and fks hot spot mutant Candida isolates.</a> Antimicrobial Agents and Chemotherapy. 55 (5), 1891-1895 (2011).</li><li>Mukaremera, L., Lee, K. K., Mora-Montes, H. M., Gow, N. A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Candida+albicans+yeast,+pseudohyphal,+and+hyphal+morphogenesis+differentially+affects+immune+recognition.">Candida albicans yeast, pseudohyphal, and hyphal morphogenesis differentially affects immune recognition.</a> Frontiers in Immunology. 8, 629 (2017).</li><li>Hung, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+photodynamic+therapy+against+fungal+keratitis.">Recent advances in photodynamic therapy against fungal keratitis.</a> Pharmaceutics. 13 (12), 2011 (2021).</li><li>Martinez, J. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rose+Bengal+photodynamic+antimicrobial+therapy:+a+pilot+safety+study.">Rose Bengal photodynamic antimicrobial therapy: a pilot safety study.</a> Cornea. 40 (8), 1036-1043 (2021).</li></ol>

Encouraging results of clinical applications of RB-PDT for fungal keratitis have been reported recently19. The absorption peak of RB is at 450-650 nm. It is essential to determine the fluence rate of the light source for a successful aPDT. A high fluence (usually &#62;100 J/cm2) is required to treat cancer cells, while a lower fluence is expected to treat infected lesions6. A high fluence means a long exposure time which may not be practical in a clinical setting...

C. albicans colonizes in the gastrointestinal and genitourinary tracts of healthy individuals and can be detected as normal microbiota in about 50 percent of individuals1. If an imbalance is created between the host and the pathogen, C. albicans is capable of invading and causing disease. The infection can range from local mucous membrane infections to multiple organ failure2. In a multicenter surveillance study in the US, around half of the isolates from patients with invasive candidiasis between 2009 and 2017 is C. albicans3. Candidemia can be associated with high morbidity rates, mortality, prolonged hospital stay4. US Centers of Disease Control and Prevention reported that about 7% of all Candida blood samples tested are resistant to the antifungal drug fluconazole5. The emergence of drug-resistant Candida species raises the concern to develop an alternative or adjuvant therapy to antimycotic agents.
Antimicrobial photodynamic therapy (aPDT) involves activating a specific photosensitizer (PS) with light at the peak absorption wavelength of the PS6. After excitation, the excited PS transfers its energy or electrons to the nearby oxygen molecules and returns to the ground state. During this process, reactive oxygen species and singlet oxygen are formed and cause cell damage. aPDT has been widely used to kill microorganisms since the 1990s7. One of the benefits of aPDT is that multiple organelles are damaged in a cell by singlet oxygen and/or reactive oxygen species (ROS) during irradiation; thus, resistance to aPDT has not been found till today. Moreover, a recent study reported that the bacteria that survived after aPDT became more sensitive to antibiotics8.
The light sources used in aPDT include lasers, metal halogen lamps with filters, near-infrared light, and light-emitting diode (LED)9,10,11,12. The laser provides a high light power, usually larger than 0.5 W/cm2, that allows for the delivery of a high light dose in a very short time. It has been widely used in cases where a longer treatment time is inconvenient such as aPDT for oral infections. The drawback of a laser is that its spot size of illumination is small, ranging from a few hundred micrometers to 10 mm with a diffuser. Moreover, laser equipment is expensive and needs specific training to operate. On the other hand, the irradiation area of a metal halogen lamp with filters is relatively larger13. However, the lamp is too hefty and expensive. LED light sources have become mainstream of aPDT in the dermatologic field because it is small and less expensive. The irradiation area can be relatively large with an array arrangement of the LED light bulb. The whole face can be illuminated at the same time9. Nevertheless, most, if not all, LED light sources available today are designed for clinical use. It may not be suitable for experiments in a lab because it is space-occupying and expensive. We developed an inexpensive LED array that is very small and can be cut and assembled from a LED strip. The LEDs can be fitted into different arrangements for different experimental designs. Different conditions of aPDT can be completed in a 96-well plate or even a 384-well plate in one experiment.
Rose bengal (RB) is a colored dye widely used to enhance visualization of corneal damages in human eyes14. RB-mediated aPDT has shown killing effects on Staphylococcus aureus, Escherichia coli, and C. albicans with roughly comparable efficiency to that of Toluidine blue O15. This study demonstrates a method to validate the effect of RB-aPDT on multidrug-resistant C. albicans.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1.5 mL microfuge tube</td>
			<td>Neptune, San Diego, USA</td>
			<td>#3745.x</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL round-bottom tube with cell strainer cap</td>
			<td>Falcon, USA</td>
			<td>#352235</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well plate</td>
			<td>Alpha plus, Taoyuan Hsien, Taiwan</td>
			<td>#16196</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum foil</td>
			<td>sunmei, Tainan, Taiwan</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum heat sink</td>
			<td>Nanyi electronics Co., Ltd., Tainan, Taiwan</td>
			<td>BK-T220-0051-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Eppendorf, UK</td>
			<td>5415R</td>
			<td>disperses heat from the LED array</td>
		</tr>
		<tr>
			<td>Graph pad prism software</td>
			<td>GraphPad 8.0, San Diego, California, USA</td>
			<td></td>
			<td>graphing and statistics software</td>
		</tr>
		<tr>
			<td>Green light emitting diode (LED) strip</td>
			<td>Nanyi electronics Co., Ltd., Tainan, Taiwan</td>
			<td>2835</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Yihder, Taipei, Taiwan</td>
			<td>LM-570D (R)</td>
			<td>Emission peak wavelength: 525 nm, Viewing angle: 150&#176;; originated from https://www.aliva.com.tw/product.php?id=63</td>
		</tr>
		<tr>
			<td>Light power meter</td>
			<td>Ophir, Jerusalem, Israel</td>
			<td>PD300-3W-V1-SENSOR,</td>
			<td></td>
		</tr>
		<tr>
			<td>Millex 0.22 &#956;m filter</td>
			<td>Merck, NJ, USA</td>
			<td>SLGVR33RS</td>
			<td></td>
		</tr>
		<tr>
			<td>Multidrug-resistant Candida albicans</td>
			<td>Bioresource Collection and Research CenterBioresource, Hsinchu, Taiwan</td>
			<td>BCRC 21538/ATCC 10231</td>
			<td>http://catalog.bcrc.firdi.org.tw/BcrcContent?bid=21538</td>
		</tr>
		<tr>
			<td>OD600 spectrophotometer</td>
			<td>Biochrom, London, UK</td>
			<td>Ultrospec 10</td>
			<td></td>
		</tr>
		<tr>
			<td>Rose Bengal</td>
			<td>Sigma-Aldrich, MO, USA</td>
			<td>330000</td>
			<td>stock concentration 40 mg/mL = 4%, prepare in PBS, stored at 4 &#176;C</td>
		</tr>
		<tr>
			<td>Sterilized glass tube</td>
			<td>Sunmei Co., Ltd., Tainan, Taiwan</td>
			<td>AK45048-16100</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract Peptone Dextrose Medium</td>
			<td>HIMEDIA, India</td>
			<td>M1363</td>
			<td></td>
		</tr>
	</tbody>
</table>

rose bengal-mediated photodynamic therapy to inhibit candida albicans

Invasive Candida albicans infection is a significant opportunistic fungal infection in humans because it is one of the most common colonizers of the gut, mouth, vagina, and skin. Despite the availability of antifungal medication, the mortality rate of invasive candidiasis remains ~50%. Unfortunately, the incidence of drug-resistant C. albicans is increasing globally. Antimicrobial photodynamic therapy (aPDT) may offer an alternative or adjuvant treatment to inhibit C. albicans biofilm formation and overcome drug resistance. Rose bengal (RB)-mediated aPDT has shown effective cell killing of bacteria and C. albicans. In this study, the efficacy of RB-aPDT on multidrug-resistant C. albicans is described. A homemade green light-emitting diode (LED) light source is designed to align with the center of a well of a 96-well plate. The yeasts were incubated in the wells with different concentrations of RB and illuminated with varying fluences of green light. The killing effects were analyzed by the plate dilution method. With an optimal combination of light and RB, 3-log growth inhibition was achieved. It was concluded that RB-aPDT might potentially inhibit drug-resistant C. albicans.

Figure 1 shows the aPDT system being used in the present study. Since high temperatures may cause significant cell death, the LED array is cooled by an electric fan, and a heat sink is used during irradiation to maintain a constant temperature at 25 &#177; 1 &#176;C. The heat effect can be discounted. Having an even light distribution is also an important determining factor for a successful aPDT; therefore, it is critical to align the LED light bulb to the well precisely during illumination....

Watch this Scientific Journal Video about Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans at JoVE.com

Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans

The growing incidence of drug-resistant Candida albicans is a serious health issue worldwide. Antimicrobial photodynamic therapy (aPDT) may offer a strategy to fight against drug-resistant fungal infections. The present protocol describes Rose bengal-mediated aPDT efficacy on a multidrug-resistant C. albicans strain in vitro.

Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans

Invasive Candida albicans infection is a significant opportunistic fungal infection in humans because it is one of the most common colonizers of the gut, ...

This study is a simple, versatile and easy system to examine different photodynamic effects on various microorganisms and cells. In this system, the LED can be fit into different arrangement depending on experiment design. Different condition of PDT can be computated in a 96-well plate or even a 384-well plate in one experiment.This technique can be used to treat fungal keratitis because of which globally, around 150, 000 people lose their eyes in spite of intensive treatments. To begin, cut four green LEDs from an LED strip and align them with three wells of a 96-well plate. Measure the fluence rate of the LED at 540 nanometers with a light power meter.Maintain constant temperature at 25 degrees Celsius with an electric fan that was assembled alongside the plate during irradiation. With a sterile loop, pick a single colony of Candida albicans from an agar plate and add it to a sterilized glass tube containing three milliliters of YPD medium. Incubate the tube at 25 degrees Celsius at a rotation speed of 155 RPM for 14 to 16 hours to grow the yeast culture.Next dilute the overnight culture with YPD medium to an OD 600 value of 0.5. Incubate at 30 degrees Celsius with rotation at 155 RPM for four hours to achieve the log growth phase. Repeat the dilution of the log phase culture with fresh YPD medium to an OD 600 value of 0.65, to get approximately one times 10 to the seventh colony forming units per milliliter.Simultaneously prepare a 4%stock solution of rose bengal in 1X PBS. Filter sterilize with a 0.22 micrometer filter. Add 111 microliters of 2%rose bengal solution to one milliliter of log phase culture, and co-culture at different time points at room temperature to understand the absorption of RB in the cells.Centrifuge at 16, 100 times G for 2 1/2 minutes at room temperature, and wash the co-culture three times with one milliliter of 1X PBS. After washing, resuspend the Candida albicans culture in one milliliter of 1X PBS. For each condition, distribute the culture into three different wells in a 96-well plate.Align the wells with the LED array. In the light exposed groups, turn on the electric fan and light. After irradiation, perform tenfold serial dilutions twice by taking 20 microliters of the co-culture solution from one well, and adding it to a tube containing 180 microliters of 1X PBS.Then drop 20 microliters of each serial dilution in one quadrant of a YPD agar plate to obtain countable colonies on the plate. Fluorescent microscopy showed immediate staining of Candida albicans with rose bengal under red fluorescence. After 15 minutes of incubation, most of the cells were stained with rose bengal, indicating that it enters the cells in a time-dependent manner.Further, activation of rose bengal with light generates free radicals and singlet oxygen in the cells, resulting in cell death. In absence of rose bengal or irradiation, no cell death was observed. Candida albicans was inhibited after green light irradiation in the presence of 0.2%rose bengal in a light dose-dependent manner.It is important that first the 96-well plate must be aligned with the center of the LED. Second, the agar plate used must be dried thoroughly to prevent the mixing of separate colonies. The Candida albicans that grew on the plate can be further sent for gene analysis, which can answer how PDT affects gene expression of the cells.These techniques pave the way to examine how PDT works on different cell types, either cancer cells, bacteria, fungi or viruses with an easy, inexpensive and versatile platform.

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JoVE Journal

Immunology and Infection

2.9K visualizações.  National Cheng Kung University. Este estudo é um sistema simples, versátil e fácil de examinar diferentes efeitos fotodinâmicos em vários microrganismos e células. Neste sistema, o LED pode ser encaixado em diferentes arranjos, dependendo do design do experimento. Diferentes condições de PDT podem ser computadas em uma placa de 96 poços ou até mesmo uma placa de 384 poços em um experimento.Essa técnica pode ser usada para tratar a ceratite fúngica, pois globalmente, cerca de 150.000 pessoas perdem os olh...