Using milk exosomes (mExos) to encapsulate the probiotic, researchers from the Ocean University of China aimed to form a ‘protective shield’ by targeting polysaccharides on the probiotic surface.
They reported high survival rates across three commonly used bacterial strains and improved intestinal adhesion.
“mExos exhibit excellent biocompatibility and gastrointestinal tolerance, demonstrating the potential to encapsulate and protect probiotics,” the authors wrote in Nutrients.
The problem with traditional encapsulation techniques
Encapsulation approaches have come some way in ensuring probiotics can survive the acidic pH, bile salts and digestive enzymes in the gastrointestinal environment, with microencapsulation largely improving the viability of probiotics.
However, problems still exist, including difficulty in controlling particle size, ‘leakage’ of probiotics and low efficiency in vivo, the researchers noted.
To overcome these drawbacks, they assessed a novel encapsulation technique which involves using nanoparticles to coat live bacteria.
Previous research has shown that milk exosomes— nanoparticles that carry proteins, lipids and nucleic acids—can protect molecules from degradation and digestion and can regulate the intestinal microflora in mice.
In order to achieve superior encapsulation and delivery efficacy, the researchers modified the exosome membrane using distearoyl phosphatidyl ethanolamine-polyethylene glycol-phenylboric acid (DSPE-PEG-PBA).
Study details
To test the efficacy of their approach, the study assessed three bacterial strains commonly used in probiotic formulas: Akkermansia muciniphila (AKK), Bifidobacterium animalis subsp. lactis BB-12 (BB12) and Lactiplantibacillus plantarum Q7 (Q7).
Each strain was coated with mExo@DSPE-PEG-PBA and suspended in a culture medium at 37°C, with specific pH and bile salt conditions to mimic the human gut.
Various techniques were used to analyze the properties of the encapsulated probiotics, such as transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and intrinsic fluorescence spectra (IFS).
TEM is a microscopy technique used to visualize the morphology and structure of the coated probiotics, while FT-IR and IFS were used to monitor how they performed.
Milk exosomes: a new probiotic carrier?
The researchers found that the final survival rates of the coated probiotics were higher than the uncoated counterparts, with Q7 showing a survival rate of 80.99%, BB12 of 85.28% and AKK of 94.53%.
The hydrophobicity—a cell surface characteristic of probiotics that helps them adhere to the gut lining— was also enhanced, as was the auto-aggregation capacity, leading to a significant improvement in mucoadhesive properties.
“The increase in the self-aggregation rate of probiotics might be related to the embedding of mExos, which increased the surface area of probiotics,” the researchers explained.
They also found that probiotics encapsulated with milk exosomes had good biosafety, with no toxic effects on cells.
The researchers therefore suggest that this encapsulation method has the potential to enhance the pH and the bile salt tolerance of probiotics, enabling the live bacteria to resist the digestion of gastric and intestinal fluid and colonize the gastrointestinal tract.
“These findings suggest that the mExo@DSPE-PEG-PBA@Probiotics system could be developed as a new carrier, not only for embedding and delivering probiotics but also for enhancing probiotic viability, intestinal adhesion and colonization,” they concluded.
Source: Nutrients. doi: 10.3390/nu17050923. “Milk Exosome-Based Delivery System for Probiotic Encapsulation That Enhances the Gastrointestinal Resistance and Adhesion of Probiotics.” Authors: L. Hao, et al.