Among several ions playing a vital role in the body, Sr2+ and Mg2+ are involved in the mechanism of bone formation, making them especially useful for bone tissue engineering applications. Recently, polylactic acid (PLA)/Mg composites have emerged as a promising family of biomaterials due to their inherent biocompatibility and biodegradability properties. In these composites, polymer and bio-metal have a synergetic effect—while the PLA inhibits the Mg fast reactivity, Mg provides bioactivity to the inert polymer buffering the medium pH during degradation. Meanwhile, the typical form of administrating Sr2+ to patients is through the medication strontium ranelate (SrR), which increases the bone mineral density. Following this interesting research line, a new group of composites, which integrates Mg particles and SrR charged onto halloysite nanotubes (HNT) in a polymeric matrix, was proposed. PLA/Mg/SrR–HNT composites have been processed following a colloidal route, obtaining homogenous composites granulated and film-shaped. The drug delivery profile was evaluated in terms of in vitro lixiviation/dissolution paying special attention to the synergism of both ions release. The combination of two of the most reported ions involved in bone regeneration in the composite biomaterial may generate extra interest in bone healing applications.

Biodegradable membranes, including Polylactic acid (PLA)-based membranes, are commonly used in bone-tissue-related clinical procedures as biointerface to promote bone tissue regeneration. Calcium (Ca2+) and Magnesium (Mg2+) ions have been related to the promotion of osteogenesis, where the PLA membranes could be used as carrier and delivery substrate for them to provide osteogenic properties to this material. For this aim, a new ion delivery system based on biodegradable PLA membranes loaded with Mg and hydroxyapatite (HA) particles has been processed by the combination of tape casting and colloidal route. Materials characterization shows that the incorporation of Mg and HA particles changes the surface and hydrophobicity of the PLA membrane, and the in vitro degradation test shows Mg2+ and Ca2+ ion release and occasionally the precipitation of different ion species onto the membrane surface. Mouse and human Mesenchymal Stem Cells (MSC) were used to define the biocompatibility and bioactivity of these PLA membrane composites, and data indicated Mg2+ promotes cell proliferation and potentiates osteoinductive signals, while Ca2+ induces the expression of ALP osteogenic marker in human MSCs. Biodegradable PLA membranes loaded with Mg and HA particles is a promising new ion delivery system of Mg2+ and Ca2+ ions that provides osteogenic signals and works as functional biointerface interfaces with bone tissues.

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