In the framework of bacterial infections, those associated with Helicobacter pylori (Hp) are among those raising greatest concern, as they show a high worldwide prevalence combined with high failure of pharmacologic solutions due to antibiotic resistance. To overcome this limitation, endoscopic photodynamic therapy (PDT) devices have been tested, e.g. in the form of modified gastroscopes, also taking advantage from the endogenous production of photoactive porphyrins by the bacterium itself. In scientific literature, the proof-of-principle of Hp killing by visible light has been demonstrated in in vitro models and in one case also in vivo with a clinical test. However, all the illumination techniques realized up-to-date exhibit clear disadvantages, namely great invasivity, poor patient compliance and adverse effects.
In this context, we propose the use of an innovative illumination scheme, by means of an ingestible luminous capsule to perform intra-gastric photodynamic therapy against Hp in a minimally-invasive and efficient way. By combining photonics and robotics, we have started by designing a miniaturized device whose geometrical, mechanical and light-emission properties were compatible with an efficient bacterial photo-killing and all the safety requirements for medical devices. During its permanence in the gastric antrum, where Hp is mostly found, the capsule illuminates the gastric wall thanks to Light Emitting Diode (LED) sources, powered by a built-in battery. No active controls are envisaged, neither for the illumination (ideally performed with a “360o scheme”) nor for the capsule positioning, to maximize the radiant energy delivered. Once in the intestine, the device will be turned off thanks to e.g. pH sensors.
In this communication, the characteristics of the prototypes realized up to now will be described, including the illustration of their light-emission properties. Preliminary results in terms of in vivo photo-killing efficiency and safety studies will be presented. Besides, a semi-theoretical approach for the study of the action spectrum for in vivo photo-killing will be shown, where the gastric wall light-filtering and diffusing effect are taken into account. This has led to the definition of the best illumination wavelengths to optimize the PDT efficiency during the permanence time of the capsule in the stomach.
The efforts in designing and realizing our device have led to the creation of Probiomedica, a spin-off of both the University of Florence and the Scuola Superiore Sant’Anna in Pisa.