Exploring the phototherapy modalities and dosages for an ingestible light-emitting diode capsule to eliminate Helicobacter pylori infection

Abstract

Helicobacter pylori (H. pylori) infection presents increasing challenges to antibiotic therapies owing to limited drug bioavailability, multi-drug resistance and collateral damage to commensal intestinal microflora. To address these problems, here, an ingestible magnetically controlled light-emitting diode (LED) light source was designed for an ingestible capsule to perform antimicrobial photodynamic therapy (aPDT) without an exogenous photosensitizer (ex-PS) at 630 nm. Specifically, we first optimized the antibacterial rates of aPDT with ex-PS and aPDT without ex-PS against H. pylori at the bacterial suspension level by varying the wavelength (405, 530, 630 nm), photosensitizer concentration (2, 4, 6, 8, 10 μg/mL), power density (15, 30 mW/cm²), and energy density (0, 3.6, 7.2, 10.8, 14.4, 18.0 J/cm²). Then, we compared the antibacterial effect of aPDT with ex-PS and aPDT without ex-PS against H. pylori at the biofilm level, revealing that the antibacterial rate of aPDT without ex-PS reached approximately 97 % at 405 nm and 18 J/cm², similar to that of aPDT with ex-PS under the same conditions. Furthermore, 80 SD rats infected with H. pylori were treated with aPDT with ex-PS and aPDT without ex-PS at the above wavelengths. Histopathological analysis of rat gastrointestinal tissues revealed that aPDT with ex-PS and aPDT without ex-PS exhibited significant antibacterial activity against H. pylori, without side effects on normal tissues. Additionally, aPDT without ex-PS at 630 nm induced an anti-inflammatory response and regulated the intestinal flora. Ultimately, we developed a magnetically controlled LED capsule for in vivo aPDT without ex-PS at 630 nm against H. pylori.

Keywords: Antimicrobial photodynamic therapy; Exogenous photosensitizers; Helicobacter pylori; Ingestible LED capsule; Intestinal flora.