# An Intelligent Wired Capsule for the Treatment of Helicobacter pylori
## 2 Materials and Methods  
The PDT photodynamic therapy is a non-invasive treatment based on the effects resulting from the combination of individually inert agents. The conversion of molecular oxygen into reactive oxygen species, ROS, which can damage the cytoplasmic organelles or the cell membrane of the treated cells, originates from the stimulation of a light-sensitive substance through appropriate wavelengths [6]. Spectroscopic characterization and fluorescence imaging of _Helicobacter pylori_ endogenous porphyrins as been also performed in literature [7].  
The effect generated on many bacteria, both Gram-negative and Gram-positive, led to the evaluation of PDT in the eradication of _H. pylori_, with a view to determine an effective treatment that overcomes the problem of antibiotic resistance [8; 9; 10; 11].  
In reality, the action of the PDT against _H. pylori_ was tested by [PERSON] as early as 1990 [12]. Further experiments, aimed at detecting the action of different PS, reported interesting results following the application of Protoporphyrin IX in the treatment of _H. pylori_[13]. The determination of the ability, by various strains of _H. pylori_, to spontaneously synthesize porphyrins was the real step forward in considering PDT as an alternative treatment to the antibiotic. The bacterium, cultured in an aqueous medium, has, in fact, shown the ability to synthesize a quantity of protoporphyrins IX and coprorphyrins sufficient to kill even the most virulent and antibiotic resistant species, simply by using visual light. All strains involved in the experiment showed 99.9% eradication following irradiation at 20 J/cm\({}^{2}\) with a wavelength of 405 nm [14]. The absorption spectrum of the bacterium's endogenous porphyrins varies in relation to the relative concentration between PPIX (protoporphyrin IX), and CP (coproporphyrin I). However, this spectrum is characterized by a maximum absorption peak around 400 nm followed by a second peak, approximately 10 times lower in intensity, located between 500 nm and 650 nm. Porphyrin extracted from various strains of _H. pylori_ shows, in fact, the same fluorescence spectrum as commercial porphyrin [6].  
[PERSON] and co. developed the first clinical trial aimed at verifying the eradication of _H. pylori_ by blue light. The treatment focuses on the gastric antrum, which was uniformly exposed to the wavelength of 450 nm for 4.5 min, using a laser diode endoscope, also used to identify the areas to be treated and to take samples, both before and after treatment. The comparison between the samples taken before and after the treatment shows that _H. pylori_ can be eradicated in a single therapeutic session. At the relatively low levels of energy and power used, there is no appreciable overheating of the stomach wall or tissue damage [15]. However, it is necessary to verify the ability of the wavelength used to hit the _H. pylori_ undermined within the mucosa. Previous studies, aimed at determining the depth of penetration of visible light into the tissues, found that light at 400 nm penetrates only 2 mm into bovine muscles [16].  
[PERSON] and co. created a device capable of supplying 12 W to the entire surface of the stomach with a wavelength of 408 nm. The comparison between the samples taken before and after the treatment shows a significantly different bacterial load in the antrum and in the body, but not in the fundus of the stomach. The long-term results of the urea breath test show no changes following treatment, indicating the failure of the proposed therapy. One result could be derived from the presence of bacterial colonies undermined in depth in the wrinkles or in the crypts of the mucosa, difficult to reach by the wavelength used, regardless of the duration of irradiation. The result also indicates that a small residual bacterial fraction is enough to re-establish the colonization of _H. pylori_.