The methodology behind blue light is that it can operate by activating a photosensitizing molecule, porphyrin, that is produced within many of the target bacterium or microbes. It is an oxygen dependent mechanism in which the visible light excites the endogenous porphyrin into a high energy state and and transfers the energy to form a reactive oxygen species. The porphyrin can produces ROS or reactive oxygen species which kills the microbes and thus reduces the proliferation of the biofilm [1]. As of now there is an investigation to see the ideal dosage required for this inactivation to occur. It was found that a power of around 60 mJ/cm^2 at an optimal wavelength of 405 nm, where 405 nm is the peak absorption wavelength of porphyrin, achieved a one log reduction in bacteria confluence [2].

In general, Blue light is found in the visible light spectrum around 400-450 nm. In our everyday lives, blue light is known to be harmful as it is found in multiple of our technologies such as phones and laptops and can cause fatigue and eye strain. However, blue light has anti microbial properties around 400-410 nm that can eradicate E. coli. In this case it can be used to our advantage as a sterilization method.

In the U.S., 1 out of every 25 hospitalized patients contracts one or more HAIs, which are responsible for increased morbidity, mortality, and healthcare costs. HAIs occur in 5-10% of acute care hospital admissions, and this costs around $28-45 billion annually. UTIs are the most prevalent HAIs – about 75% of UTIs are contracted through urinary catheters, and roughly 15%-25% of hospitalized patients require them. The daily risk of bacterial acquisition when urinary catheters are kept in-situ varies from 3% - 7%, increasing the likelihood of the patient contracting a CAUTI. From this broad market need for the medical device to help curb the onset of a CAUTI, the following stakeholder such as patients, doctors, hospitals, and researchers can benefit from Blue Light being proven as a valid way to sterilize urinary catheters and eradicate E. coli.

Blue light, or visual light sterilization (VLS), has the possibility to be used as a safe alternative to other sterilization methods, such as UV light radiation, or more specifically, UVC light radiation [3]. The mechanism of UVC inactivation of microorganisms is by damaging genetic material in the nucleus of the cell [3]. UVC is known to have the strongest germicidal effect. However, UVC inactivation can also damage mammalian cells because of its short wavelength and has been known to cause skin cancer [6]. Blue light sterilization, which has a wavelength of around 405 nm, is known to also eradicate bacteria without causing damage to mammalian cells [4]. The current practice to sterilize urinary catheters is to insert the catheter in a device such as the sterilizer box shown on the left. This can sterilize catheters before or after use in the human body. However, UV sterilization cannot be used on the human body because it is unsafe and therefore the body is left vulnerable to infections by HAIs and CAUTIs.

In comparison to the use of antibiotics to treat hospital associated infections that develop, a blue light catheter method can proactively prevent these infections by inducing biophysical effects on internal cellular content [4]. Additionally, the infections can become antibiotic resistant and need much stronger antibiotics to be treated, which are obviously much more expensive [4]. Unlike antibiotics, the blue light catheter method is not a time-dependent process that the patient has to follow in order to treat the infection; it is a prevention method that effectively diminishes the risk of infection later on [8].

Some current applications for blue light can be seen with the treatment for acne.

Blue light therapy has been proven effective with the eradication of acne-causing bacteria such as Propionibacterium acnes (P. acnes) bacterium. An open study was performed in acne patients who were treated twice a week up to 5 weeks with a high intensity, enhanced, narrow band, blue light source of around 410 nm [3]. This specific type of phototherapy was shown to be effective and well tolerated in the acne patients [3]. Blue light was able to significantly decrease the numbers of P. acnes invitro [3]. Another study was done that examined and assessed the eradication of P. acnes by its endogenic porphyrins after illumination with intense blue light at 407-420 nm [3]. The viability of 24h cultures that were grown anaerobically in liquid medium was reduced by less than two orders of magnitude when illuminated once with a light dose of 75 J cm-2. Even better photodynamic effects were obtained when cultures were illuminated twice or three times with a dose of 75 J cm-2 , as the viability of the culture decreased by four orders of magnitude after two illuminations [4]. Thus, using visible blue light to illuminate bacterium is a possible form of eradication. Blue light works by an oxygen dependent mechanism in which this visible light excites the endogenous porphyrins into a high energy state and transfers the energy to from a reactive oxygen species, ROS, that causes damage inside the cell [1].