Dual-light photodynamic therapy administered daily provides a sustained antibacterial effect on biofilm and prevents Streptococcus mutans adaptation
Sakari Nikinmaa, Heikki Alapulli, Petri Auvinen, Martti Vaara, Juha Rantala, Esko Kankuri, Timo Sorsa, Jukka Meurman, Tommi Pätilä
Published: May 6, 2020 https://doi.org/10.1371/journal.pone.0232775
Antibacterial photodynamic therapy (aPDT) and antibacterial blue light (aBL) are emerging treatment methods auxiliary to mechanical debridement for periodontitis. APDT provided with near-infrared (NIR) light in conjunction with an ICG photosensitizer has shown efficacy in several dental in-office-treatment protocols. In this study, we tested Streptococcus mutans biofilm sensitivity to either aPDT, aBL or their combination dual-light aPDT (simultaneous aPDT and aBL) exposure. Biofilm was cultured by pipetting diluted Streptococcus mutans suspension with growth medium on the bottom of well plates. Either aPDT (810 nm) or aBL (405 nm) or a dual-light aPDT (simultaneous 810 nm aPDT and 405 nm aBL) was applied with an ICG photosensitizer in cases of aPDT or dual-light, while keeping the total given radiant exposure constant at 100 J/cm2. Single-dose light exposures were given after one-day or four-day biofilm incubations. Also, a model of daily treatment was provided by repeating the same light dose daily on four-day and fourteen-day biofilm incubations. Finally, the antibacterial action of the dual-light aPDT with different energy ratios of 810 nm and 405 nm of light were examined on the single-day and four-day biofilm protocols. At the end of each experiment the bacterial viability was assessed by colony-forming unit method. Separate samples were prepared for confocal 3D biofilm imaging. On a one-day biofilm, the dual-light aPDT was significantly more efficient than aBL or aPDT, although all modalities were bactericidal. On a four-day biofilm, a single exposure of aPDT or dual-light aPDT was more efficient than aBL, resulting in a four logarithmic scale reduction in bacterial counts. Surprisingly, when the same amount of aPDT was repeated daily on a four-day or a fourteen-day biofilm, bacterial viability improved significantly. A similar improvement in bacterial viability was observed after repetitive aBL application. This viability improvement was eliminated when dual-light aPDT was applied. By changing the 405 nm to 810 nm radiant exposure ratio in dual-light aPDT, the increase in aBL improved the antibacterial action when the biofilm was older. In conclusion, when aPDT is administered repeatedly to S. mutans biofilm, a single wavelength-based aBL or aPDT leads to a significant biofilm adaptation and increased S. mutans viability. The combined use of aBL light in synchrony with aPDT arrests the adaptation and provides significantly improved and sustained antibacterial efficacy.
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Small-form-factor LED-based light application surface for ICG-mediated antibacterial photothermal therapy
Nikinmaa S, Meurman J, Moilanen N, Sorsa T, Rantala J, Alapulli H, Kankuri E, Kotiranta A, Auvinen P, Pätilä T.
Antimicrobial photodynamic therapy (aPDT) has been introduced as an adjunct method for dental hygiene. Although antibacterial and antiplaque effects resulting from aPDT
Fifteen healthy adults were assigned to the study. Upper premolars (4. and 5.) were examined on both sides of the maxilla. After meticulous scaling and root planing, the maxillary dental arch was left without any mechanical cleaning for four days. Randomisation of the treatment side of the upper dental arch was performed, and following the initial sample collection, the mouth was rinsed with ICG and 100J/cm2 of 810 nm light was subsequently applied for eight minutes. The treatment was repeated daily for four days. ICG localisation after the mou
Antimicrobial photodynamic therapy resulted in a significant reduction of plaque formation. An analysis of the 16S rRNA sequencing found a reduction in the Streptococcus, Acinetobacterial, Capnocytophagal, and Rothia bacteria species and a gain in Neisseria and Hemophilus ba
In conclusion, ICG-based aPDT is effective and reduces the amount of known oral pathogens, with compensated bacterial growth in species associated with good oral health, but without a change in overall bacterial diversity. The treatment can be applied specifically to dental plaque, and the anti-inflammatory effect may prevent the development of early gingivitis.
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A Review of Fluorescent Imaging in Surgery
International Journal of Biomedical Imaging | Volume 2012 | Article ID 940585 | 26 pages | https://doi.org/10.1155/2012/940585
Academic Editor: Guowei Wei
The purpose of this paper is to give an overview of the recent surgical intraoperational applications of ICG fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.
Fluorescence Imaging (FI) is one of the most popular imaging modes in biomedical sciences for the visualisation of cells and tissues both in vitro and in vivo . The benefits of FI include
1. high contrast, that is, signal to noise ratio (SNR): only the target, not background, is visible because separate wavelengths are used for illumination and recording,
2. high sensitivity: extremely small concentrations can often be made visible,
3. Gives molecular information: makes some (bio) chemistry spatially and temporally visible,
4. great tools for research: several possible imaging modes, most of which are unique,
5. cheap: the optical instrumentation and computing needed are quite simple,
6. easy to use: resembles classical staining.
Fluorescent imaging is a relatively recent imaging method and thus still developing in many ways. This is especially true for ICG imaging in its new clinical applications recently proposed in various branches of surgical medicine, although it has been used in some clinical applications routinely already for almost sixty years. Thus, ICG is well known in its established clinical applications, which greatly facilitates its introduction to new applications. From an engineering point of view, image and video processing seems to be among the main areas in which ICG imaging (ICGI) has potential for major developments, for example, for analysis of ICG fluorescence dynamics  (cf. Figure 2). This means, among other things, that a lot of computing development work is still needed for a broader acceptance of various emerging ICG-based medical imaging methods .
4.8.1. Photodynamic and Photothermal Therapy
When an ICG molecule is excited, it can further transfer energy to other molecules. When exciting oxygen, ICG turns out to be a photodynamic therapy agent. In principle, for example, after having been used to reveal lymph nodes a strong illumination with NIR light could be used to destroy metastatic nodes. ICG binds easily to tissue even at high concentrations, and the visual change in colour from green to orange is manifested by the wavelength shift in reflectance peak. ICG has been used in vitro laser-assisted fat cell destruction, which might give a new optics-based procedure for cosmetic surgery .
Similarly, ICGA can be used as a light-activated antibacterial agent (LAAA), for example, in wound healing , or treating chronic rhinosinusitis  with near-infrared laser illumination (NILI). It was shown recently that the photodynamic effect can be used for acne treatment [241–243]. Nevertheless, many problems have to be solved in order to design optimal technology for acne treatment without side effects.
Through intense light (laser) irradiation a number of new effects can be provided, which lead to more effective bacteria killing and controllable cell destruction and/or inhibition of excessive synthesis of sebum in sebocytes, like the localised photodynamic effect based on the appropriate concentration of the suitable exogenous dye incorporated into hair follicle or any other skin appendages. ICG is one of the prospective exogenous dyes for soft photodynamic treatment (PDT).