## 4 Discussion
### Pbm  
This spectrophotometric study revealed that all the examined photosensizers applied at appropriate concentrations can allow light transmission. As a result, in clinical conditions, light will diffuse into the surrounding tissues, leading to possible PBM effects [12; 13; 61; 62]. According to the multi-phasic response in PBM, photobiostimulation is observed within the range of 2-10 J/cm\({}^{2}\) of the applied fluence, where, specifically at 5 J/cm\({}^{2}\), the optimal effect can be achieved [14]. Considering each photosensizer's intensity loss percentage and the respective calculated transmission percentage, the fluence range of 2-10 J/cm\({}^{2}\) and the 5 J/cm\({}^{2}\) value where optimal PBM effects may be observed, a subsequent fluence range can be calculated to deliver beneficial PBM effects in the surrounding tissues when photodynamic therapy is performed. The following formulas in Equations (3) and (4) are applied for this purpose:  
\[\text{Fluence range calculated}=(\text{2-10 J/cm${}^{2}$})/\text{ transmission (\%)} \tag{3}\]  
\[\text{Optimal fluence calculated}=(\text{5 J/cm${}^{2}$})/\text{ transmission (\%)} \tag{4}\]  
Information regarding the photosensizers, laser wavelength applied, respective intensity loss and transmission, fluence range calculated and optimal fluence calculated are provided in Table 3.  
The most commonly applied fluences for performing PDT, which correspond to photochemical reactions, range from 0.1 to 200 J/cm\({}^{2}\). Concerning irradiance (fluence rate), this value should be below 300 mW/cm\({}^{2}\), since detrimental tissue heating may occur beyond this upper limit [63]. Hence, Photolase illuminated by a 660 nm laser, which exhibits this dramatically high attenuation percentage (99.1%), cannot combine beneficial PBM effects along with PDT. It should also be noted that the manufacturer suggests irradiation with an 808 nm laser device [29; 64]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Photosensitizers** & **Laser Wavelength** & **Intensity Loss** & **Transmission** & **Fluence Range** & **Optimal Fluence** \\ **(Concentration in mg/mL)** & **(nm)** & **(\%)** & **(\%)** & **Calculated** & **Calculated** \\ \hline Curcumin (5.00) & 445 & 77.06 & 22.94 & 8.72–43.59 & 21.80 \\ \hline MB (0.05) & 660 & 64.80 & 35.20 & 5.68–28.41 & 14.20 \\ \hline MB (0.10) & 660 & 88.92 & 11.08 & 18.05–90.25 & 45.12 \\ \hline MB (10.00) & 660 & 94.50 & 5.50 & 36.36–181.81 & 90.90 \\ \hline PL (unknown) & 660 & 99.10 & 0.90 & 222.22–1111.11 & 555.55 \\ \hline TB (unknown) & 635 & 80.74 & 19.26 & 10.38–51.92 & 25.96 \\ \hline ICG (0.10) & 808 & 63.08 & 36.92 & 5.42–27.08 & 13.54 \\ \hline ICG (1.00) & 808 & 89.98 & 10.02 & 19.96–99.80 & 49.90 \\ \hline PL (unknown) & 808 & 88.74 & 11.26 & 17.76–88.81 & 44.40 \\ \hline TB (unknown) & 808 & 11.79 & 88.21 & 2.27–11.34 & 5.67 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Information regarding the photosensizers, laser wavelength applied, respective intensity loss and transmission, fluence range calculated and optimal fluence calculated. Abbreviations: CUR, Curcumin; MB, Methylene blue; PL, Photolase (methylene blue derivative); TB, Tuliodine blue; ICG, Indocyanine green. An innovating concept that should be borne in mind, when performing PBM, is the \"photon fluence\", which can be characterized as the wavelength-adjusted energy density, where the photon energy of each wavelength (in eV) plays a critical role in determining the nature of light-biological tissue interactions. Therefore, to achieve a more accurate light dose, the new formula of photon fluence should be applied, as indicated below [65]:  
\[\text{Photon fluence}=\text{irradiance}\ast\text{time}\ast\text{photon energy} \tag{5}\]  
To summarize, in order for the clinician to maximise the positive treatment outcomes prior to performing such therapies, the following considerations should be taken into account:  
* The photosensizer's characteristics, such as its concentration and wavelength-dependent extinction coefficient.