Refrigerated storage of L-PRF membranes: anti-bacterial activity, cytokine release, and in vitro keratinocyte effects-an in vitro pilot study.

AIMS: This in vitro study aimed to evaluate the effect of storage, for up to 4 weeks, on the degradation kinetics and bioactivity of leukocyte- and platelet-rich fibrin (L-PRF) membranes. METHODS: L-PRF membranes obtained from 8 volunteers were stored in L-PRF exudate at 4°C for 1, 2, or 4 weeks. Their antibacterial properties against the main periodontal pathogens, release levels of key growth factors and inflammatory cytokines, and regenerative effects on human oral keratinocytes (HOKs) were compared to fresh L-PRF. RESULTS: The inhibitory effects of L-PRF exudate varied among the tested pathogens and gradually decreased during storage. Growth factors released from L-PRF membranes exhibited different degradation kinetics, with VEGF demonstrating an early reduction within the first week, whereas PDGF-AB and TGF-β1 remained relatively stable until 2 weeks. Interleukin (IL)-8, IL-1b, and IL-6 were detectably released from L-PRF membranes, predominantly in fresh samples, and decreased within the first week. Conditioned medium derived from stored L-PRF membranes significantly promoted HOK metabolic activity and wound healing in vitro, without significant reduction over the 4-week storage period. CONCLUSION: Refrigerated storage preserved some L-PRF functions for up to 4 weeks in this in vitro study, but preservation was incomplete and function-specific, with the clearest losses in antibacterial activity, VEGF release, and inflammatory cytokine release.