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Biodegradable, a new revolutionary concept, is shaping the future design of biomedical implants that need to serve only as a temporary scaffold. Magnesium appears to be the most promising biodegradable metal, but challenges remain in its corrosion-controlling and uncertain biocompatibility. In this work, we employ chemical conversion and alternating dip-coating methods to anchor and deposit an Mg ion-integrated phytic acid (Mg-PA) coating on Mg, which is supposed to function both corrosion-controlling and osteo-compatible. It was ascertained that PA molecules were covalently immobilized on a chemically converted Mg(OH)2 base layer, and more PA molecules were deposited subsequently via chelating reactions with the help of additive Mg ions. The covalent immobilization and the Mg ion-supported chelating deposition contribute to a dense and homogeneous protective Mg-PA coating, which guarantees an improved corrosion resistance as well as a reduced degradation rate. Moreover, the Mg-PA coating performed osteo-compatible to promote not only bioactivity of bonelike apatite precipitation, but also induced osteoblast cells adhesion and proliferation. This is ascribed to its nature of PA molecule and the biocompatible Mg ion, both of which mimic partly the compositional structure of bone. Our magnesium ion-integrated PA-coated Mg might bode well for the future of biodegradable bone implant application.

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It is one of the challenges for a wide clinical application of polymer micelles to address the structure disintegration and premature drug release before reaching a pathological site. In the current study, folic acid (FA)-decorated polymer-drug conjugates (FSC) were synthesized with disulfide linkages between camptothecin (CPT) and amphiphilic poly(ethylene glycol)-b-poly(ε-caprolactone) (PECL) copolymers. FSC conjugates were proposed to assemble into micelles with a hydrophobic core of PCL segments and CPT and a hydrophilic corona of PEG segments. The addition of hexadecanol during micelle formation (FSC-16) was proposed to modulate the interactions of hydrophobic segments in micelles and enhance the reductive sensitivity. FSC-16 micelles were obtained with critical micelle concentration of around 2 μg/mL and an average size of around 200 nm, and the conjugated CPT was rapidly released out in response to glutathione. The reductive sensitivity was also demonstrated with respect to the changes of micelle size and morphologies as well as the fluorescent intensity of pyrene loaded in micelles. Benefiting from the FA receptor-mediated uptake and the reduction-sensitive release of CPT, significant cytotoxicity and cell apoptosis were identified for FSC-16 micelles against SKOV-3 cells with strong expressions of FA receptors. Flow cytometry and confocal laser scanning microscopy analyses demonstrated that CPT was distributed into nuclei after cellular uptake and intracellular release from FSC-16 micelles. Thus, the FA-decorated and reduction-sensitive micelles assembled from polymer-drug conjugates show advantages in inhibiting premature release during circulation, enhancing cellular uptake at the tumor tissues, and promoting intracellular release and nuclei location of the active moieties.

No abstract