# Healing Effects of Photobiomodulation on Diabetic Wounds
## 3 Photobiomodulation (PBM)
### Effects of PBM Using Blue Light on Bacterial Growth and Fibroblasts  
PBM has been shown to eradicate bacteria within the blue spectrum of light. [PERSON] and colleagues [37] irradiated _Staphylococcus aureus_ (_S. aureus_) and _Escherichia coli_ (_E. coli_) with a halogen lamp with filters for irradiation in the blue (400-500 nm) and red (500-800 nm) spectra, or with blue LEDs (415 and 455 nm; 100 mW/cm\({}^{2}\); for 30, 60, and 120 J/cm\({}^{2}\)). There was more ROS production in bacterial cells exposed to blue light (400-500 nm) than those exposed to red light (500-800 nm). When irradiated with LEDs, 415 nm was found to be more valuable than a wavelength of 455 nm, at higher fluences. A fluence of 30 J/cm\({}^{2}\) at 415 nm and a fluence of either 30 or 60 J/cm\({}^{2}\) at a wavelength of 455 nm resulted in an increase in proliferation of _S. aureus_. [PERSON] and colleagues [45] showed that exposure of two strains of methicillin-resistant _Staphylococcus aureus_ (MRSA) to blue light at a wavelength of 470 nm (output power of 150 mW; irradiance of 30 mW/cm\({}^{2}\)) was able to inhibit and kill the bacteria. Two strains of MRSA were used, IS-853 representing hospital-acquired methicillin-resistant _S. aureus_ (HA-MRSA) and US-300 representing community-acquired _S. aureus_ (CA-MRSA). Quantification of bacterial colonies and aggregate area of colonies 24 h post-irradiation showed that there was a dose-dependent reduction in both strains. A low fluence of 3 J/cm\({}^{2}\) produced 34.1% and 27.6% death for US-300 and IS-853 strains, respectively, which increased to more than 48% and 67.3% at 7 J/cm\({}^{2}\), respectively. When a fluence of 11 J/cm\({}^{2}\) was provided, a reduction of 61.2% and 56.4% was observed, respectively. Over 80% bacterial death was noted in both strains when a fluence of 35 J/cm\({}^{2}\) was used, and there was an average death of 90.4% for both strains at a fluence of 55 J/cm\({}^{2}\), and 91.7% and 94.8% of the aggregate area was eradiated for US-300 and IS-853 strains, respectively. In a similar study, using the same LED light device (470 nm wavelength; output power of 150 mW; irradiance of 30 mW/cm\({}^{2}\)) [PERSON] and colleagues [46] irradiated MRSA USA300 three times (with 30 min between exposures) to a fluence of 36 J/cm\({}^{2}\) (cumulative fluence of 108 J/cm\({}^{2}\)) or four times (with 30 min between exposures) to a fluence of 65.5 J/cm\({}^{2}\) (cumulative fluence of 262 J/cm\({}^{2}\)). MRSA treated with blue light at either exposure regimens did not express any bacterial growth. FTIR analysis showed that there were changes in DNA conformation and that irradiation of MRSA with 470 nm light induces A-DNA cleavage. [PERSON] and colleagues [38] also showed that irradiation of MRSA USA300 to a diode laser with a wavelength of 405 nm (output power of 500 mW; irradiance of 135 mW/cm\({}^{2}\)) inhibited bacterial growth. Either bacterial cells were irradiated with a single dose, or a double dose with 30 min between doses; each dose was at a fluence of 121 J/cm\({}^{2}\). A double dose was found to be more efficient than a single irradiation. They also showed that there was depolarization of the cell membrane and that MRSA expressed demonstrable amounts of porphyrins, and its production was dependent on the cell cycle phase. It was suggested that blue light was able to target these porphyrins, and due to the production of ROS and attack thereof of the membrane, there was a decrease in the transmembrane potential, leading to cell death. An important paper published by [PERSON] et al. [47] determined the effect of blue light on fibroblast cells. If blue light is to be used to treat infected wounds in vivo, the treatment protocol needs to have an inhibitory effect on the invading pathogen, while leaving the surrounding host cells intact. Cells were irradiated at a wavelength of 470 nm and different fluencies of 3, 55, 110,or 220 J/cm\({}^{2}\) (output power of 150 mW; irradiance of 30 mW/cm\({}^{2}\)).