Lactobacilli cell-free supernatants: Potential green and natural enhancers for nose-to-brain delivery of small hydrophilic molecules

Concerns about environmental health are driving pharmaceutical industries towards more eco-friendly and biocompatible products. Lactobacilli cell-free supernatants (CFS) are mixtures of soluble factors derived from the microbial growth of beneficial bacteria with the potential to serve as natural and sustainable excipients in emerging formulations. This work aims to verify the usefulness of the CFS obtained from human L. crispatus BC5, L. gasseri BC9 and BC12 as enhancers in the nose-to-brain absorption of small hydrophilic molecules. CFS influence on cell viability was investigated together with their ability to increase the diffusion of sodium fluorescein across in vitro models of the olfactory epithelium. The enhancing mechanism was studied through differential scanning calorimetry analysis and immunostaining assay of zonula occludens-1. The use of 25% (v/v) of all lactobacilli CFS on porcine olfactory epithelial primary cells was not associated with any cytotoxic effect, but only the CFS obtained from BC5 was pointed out as a permeation enhancer across both the biomimetic membrane PermeaPad®, the porcine olfactory tissue, and the primary cell model. The enhancing mechanism seems to rely on the CFS perturbation effect on lipid membranes that, in the case of the cell-based model, probably also results in an alteration of tight junctions’ activity.