Abstract:

In recent years, there has been significant interest in the potential of probiotics to inhibit the growth of Helicobacter pylori (H. pylori), a bacterium known to cause gastric infections. However, the effectiveness of probiotics in combating H. pylori is often hindered by their susceptibility to gastric acid, making it challenging for them to survive and remain active in the stomach. To address this issue, researchers have turned to hydrogel encapsulation as a promising strategy to protect probiotics. Therefore, we designed a hydrogel-probiotic capsules possessed both acid resistance and magnetic drive properties to protect and targeted-deliver probiotics in gastric conditions. The probiotic capsules with core-shell structure prepared by the electrostatic spray method can encapsule the probiotic without damaging the activity of probiotic. The probiotic capsule was composed of a calcium alginate/CaCO₃/FeCo@G (iron-cobalt magnetic graphitic nanocapsule) shell and a Laj (Lactobacillus Johnsonii, a kind of probiotics) core (Alg/CaCO₃/FeCo@G-Laj, ACFL). The capsules were thoroughly characterized using field emission scanning electron microscopy and cell microscopic imaging to verify their morphology and their ability to encapsulate probiotics. The results indicated that ACFL capsules maintained their integrity during a 2-h incubation in DPBS (Dulbecco's Phosphate-Buffered Saline) without releasing the probiotics, underscoring their robust encapsulation capacity. Moreover, ACFL could sustain the activity of Laj in SGF (simulated gastric fluid) for a long time by locally neutralizing the gastric acid through CaCO₃. It's worth noting that Laj exhibits considerable H. pylori inhibition properties by secreting lactic acid to damage H. pylori and by competing adsorption for gastric epithelial cells with H. pylori. ACFL capsules demonstrated significant H. pylori inhibition properties even after exposure to SGF, further supporting the protective effect of the encapsulation strategy on probiotic activity. Moreover, in order to achieve efficient bactericidal performance in the real system, it is necessary to design a power device to give the capsule active propulsion ability to realize targeted delivery of Laj. FeCo@G, which possesses brilliant stability in acid environment on account of the protective graphitic shell, was integrated in ACFL for efficient magnetically navigated delivery. The results show that ACFL can reach a velocity of 3 cm·s^-1 under the guidance of an external magnetic field, which confirms the ability of ACFL capsule to be potent tool for target delivery of probiotics. In conclusion, ACFL capsules hold promise for effectively targeting the gastric wall and releasing active probiotics to combat H. pylori infections. The combination of acid-neutralizing properties and magnetic navigation not only maintains the viability of the probiotics but also minimizes disruption to gastric homeostasis. This innovative approach offers a new avenue for protecting and controlling the release of active agents in the challenging gastric environment, opening up possibilities for improved treatments and interventions.

Key words: Probiotics, Helicobacter pylori, Gastric drug delivery, Magnetic graphite nanocapsules, Acid stability