Antimicrobial Photoinactivation Using Visible Light Plus Water-Filtered Infrared-A (VIS + wIRA) and Hypericum Perforatum Modifies In Situ Oral Biofilms

Abstract

Due to increasing antibiotic resistance, the application of antimicrobial photodynamic therapy (aPDT) is gaining increasing popularity in dentistry. The aim of this study was to investigate the antimicrobial effects of aPDT using visible light (VIS) and water-filtered infrared-A (wIRA) in combination with a Hypericum perforatum extract on in situ oral biofilms. The chemical composition of H. perforatum extract was analyzed using ultra-high-performance liquid chromatography coupled with high resolution mass spectrometry (UPLC-HRMS). To obtain initial and mature oral biofilms in situ, intraoral devices with fixed bovine enamel slabs (BES) were carried by six healthy volunteers for two hours and three days, respectively. The ex situ exposure of biofilms to VIS + wIRA (200 mWcm−2) and H. perforatum (32 mg ml−1, non-rinsed or rinsed prior to aPDT after 2-min preincubation) lasted for five minutes. Biofilm treatment with 0.2% chlorhexidine gluconate solution (CHX) served as a positive control, while untreated biofilms served as a negative control. The colony-forming units (CFU) of the aPDT-treated biofilms were quantified, and the surviving microorganisms were identified using MALDI-TOF biochemical tests as well as 16 S rDNA-sequencing. We could show that the H. perforatum extract had significant photoactivation potential at a concentration of 32 mg ml−1. When aPDT was carried out in the presence of H. perforatum, all biofilms (100%) were completely eradicated (p = 0.0001). When H. perforatum was rinsed off prior to aPDT, more than 92% of the initial viable bacterial count and 13% of the mature oral biofilm were killed. Overall, the microbial composition in initial and mature biofilms was substantially altered after aPDT, inducing a shift in the synthesis of the microbial community. In conclusion, H. perforatum-mediated aPDT using VIS + wIRA interferes with oral biofilms, resulting in their elimination or the substantial alteration of microbial diversity and richness. The present results support the evaluation of H. perforatum-mediated aPDT for the adjunctive treatment of biofilm-associated oral diseases.

An extended logistic model of photodynamic inactivation for various levels of irradiance using the example of Streptococcus agalactiae

“…Irradiance is one of the most important factors influencing the acceleration of microorganism mortality in PDI processes. Experimental PDI tests are most often performed with a constant irradiance for a specified period of time [7][8][9][10][11][12] . Therefore, commonly used mathematical models of PDI processes usually refer only to specific values of irradiance without taking into account the influence of changes in irradiance on the dynamic properties of inactivation.…”

Antimicrobial Photoinactivation of In Situ Oral Biofilms by Visible Light Plus Water-Filtered Infrared A and Tetrahydroporphyrin-tetratosylate (THPTS)

“…Periodontitis, peri-implantitis and caries are the most common biofilm-associated infections in the field of dentistry. As has previously been reported, biofilm bacteria have an enhanced antibiotic resistance of up to 1000-fold that of planktonic bacteria [ 1 ]. Antimicrobial PDT (aPDT) as an alternative approach or adjunct method of dental bacterial decontamination, has the advantage that it can be applied locally because the photosensitizer is favorably located in the bacteria and not in the surrounding tissue [ 2 ].…”

“…Antimicrobial PDT (aPDT) as an alternative approach or adjunct method of dental bacterial decontamination, has the advantage that it can be applied locally because the photosensitizer is favorably located in the bacteria and not in the surrounding tissue [ 2 ]. Moreover, this therapy does not induce any resistance [ 1 ]. The mechanism of action in aPDT is, put briefly, that the presence of a photosensitizer, oxygen, and light induces oxidative damage in bacterial cells by generating free radicals or singlet oxygen [ 3 , 4 ].…”

“…Our previous studies examined photodynamic antimicrobial inactivation using toluidine blue, chlorine e6, indocyanine green and hypericin, respectively, as photosensitizers, in combination with water-filtered infrared A (wIRA) as a light source. These experiments showed that aPDT with wIRA has a remarkable potential for eradicating both initial and mature biofilms [ 1 , 5 , 6 , 7 , 8 ]. In addition, it altered the microbial composition within the biofilms.…”

Microbial Composition of Oral Biofilms after Visible Light and Water-Filtered Infrared a Radiation (VIS+wIRA) in Combination with Indocyanine Green (ICG) as Photosensitizer

“…Since the binding to plasma proteins leads to a concentration-dependent shift in the absorption spectrum of ICG, a light source with a broad wavelength spectrum was chosen [ 36 ]. For the purpose of light-induced excitation, a VIS+wIRA broadband radiator (Hydrosun ® 750 FS, Hydrosun Medizintechnik, Müllheim, Germany) with a 7 mm water cuvette was used, as described in other studies [ 23 , 37 , 38 , 39 ]. Instead of the standard light filter, an orange filter of type BTE 31 was investigated, which emphasizes the desired emission in relation to the absorption spectrum of protoporphyrin IX of more than twice the conventional filter (BTE 595).…”