Innovations in Topical Probiotic Delivery and Hydrogel Systems for Dermatological Applications

New findings suggest that encapsulating lactic acid bacteria in calcium alginate microspheres improves topical stability and expands their therapeutic potential for skin applications.

In an in vitro formulation and skin-assay system, investigators tested three lactic acid bacteria strains — Lactobacillus reuteri 182, L. plantarum F1 and L. helveticus 305 — using triplicate experiments. They applied standardized endpoints for survival, preservative resistance and keratinocyte adhesion. Bacteria were incorporated into topical emulsion matrices and encapsulated within calcium alginate microspheres to evaluate protective effects. Primary endpoints were viable counts over time, preservative-challenge response, and adhesion/co-aggregation assays.

Viability persisted for over 35 days, with viable counts of 5.94 ± 0.06 lg CFU/g at room temperature on day 35. These data show that encapsulation confers measurable stability under the study conditions and support a multi-week functional shelf life for preserved topical products pending comprehensive stability testing.

Functionally, encapsulated strains co-aggregated with skin pathogens, inhibited pathogen biofilm formation and adhered to keratinocytes at high rates. L. reuteri 182 demonstrated high keratinocyte adhesion (≈77.94 ± 1.84%) and substantial co-aggregation with Staphylococcus epidermidis (~66.9 ± 2%), and selected pairings produced complete biofilm inhibition in the reported assays. Encapsulation therefore appears to provide a protective microenvironment while preserving biologically relevant interactions (co-aggregation and displacement) that plausibly enable competitive exclusion of pathogens — a mechanistic rationale for topical probiotic strategies without implying direct clinical efficacy.

Clinically, wound-associated malignancy and other complex wound microenvironments create a need for targeted, locally triggered delivery systems. pH‑responsive hydrogels that release payloads in acidic wound niches show translational promise: they can concentrate actives locally, trigger release in acidic microenvironments, and increase local retention of drugs or biologics.

Significant translational gaps remain, however — notably local toxicity profiling, compatibility and stability of live microbes within hydrogel matrices, and manufacturing scale-up to ensure consistent pH responsiveness.