Anti-inflammatory, antibacterial, and cytotoxic activity by natural matrices of nano-iron(hydr)oxide/halloysite

This manuscript reports on the effects of natural Fe-halloysite matrices on infiltration and migration of neutrophils (polymorphonuclear (PMN) leukocytes), which, after the skin, constitute the primary protection of organisms against pathogens. Speciation of mineral Fe was quantified before and after treatment with citrate-bicarbonate-dithionite (CBD). Infiltration and migration of inflammatory and immune effector cells, and cell viability were quantified using the 12- O-tetradecanoylphorbol-13-acetate (TPA) and myeloperoxidase (MPO) enzymatic activity methods, and the Griess assay. Halloysite was collected ~. 2 km from Opotiki, Bay of Plenty, New Zealand. HRSEM images confirmed typical morphological features proper of spheroidal Hal (S-Hal). Mössbauer spectroscopy of S-Hal confirmed the presence of Fe, octahedrally coordinated in the form of substituted Fe(III), magnetically ordered goethite or ferrihydrite. HRTEM images showed the presence of small-size domains of Fe (~. 3-nm) predominantly in the form of ferrihydrite. EPR analyses of S-Hal (0-5000. ppm) before and after reacting with desferrioxamine-B confirmed the fast release of Fe from the nanodomains of ferrihydrite. Early inhibition of edema by S-Hal doubled that by CBD treated Hal (t-S-Hal), explained because labile Fe (2- L-ferrihydrite) enhanced the 4-h anti-inflammatory response. On the other hand, prolonged inhibition of edema by S-Hal and t-S-Hal compared, consistent with the release of Fe from the Hal structure. The presence of S-Hal or t-S-Hal related to the inhibition of MPO content. After 4 h, the inhibition of MPO content by S-Hal or t-S-Hal compared to that by commercial indomethacin (ca. 80%). S-Hal or t-S-Hal showed high inhibition of MPO contents shortly after exposure, but decreased sharply afterwards. On the other hand, tubular Hal (T-Hal) caused an increasing inhibition of MPO with time, explained because clay structure restricted the kinetics and mechanism of MPO inhibition. Evidenced showed that the release of mineral Fe related to infiltration and migration of inflammatory and immune effector cells, expanding the knowledge that metal ions affect inflammatory responses. Finally, dose-response experiments confirmed that the inhibition of edema and cell viability were surface-mediated. Natural clay reservoirs are complex in composition, therefore identifying the molecular mechanism(s) regulating cell migration and infiltration becomes necessary prior to recommending their use for healing purposes.