Synthesis of 3D porous ceramic scaffolds obtained by the sol-gel method with surface morphology modified by hollow spheres for bone tissue engineering applications

In the present work, we modified the surface morphology of 3D porous ceramic scaffolds by incorporating strontium phosphate (SrP) hollow nano-/microspheres with potential application as delivery system for the local release of therapeutic substances. SrP hollow spheres were synthesized by a template-free hydrothermal method. The influence of the reaction temperature, time and concentration of reactants on precipitates' morphology and size were investigated. To obtain a larger number of open hollow spheres, a new methodology was developed consisting of applying a second hydrothermal treatment to spheres by heating them at 120 °C for 24 h. The X-ray diffraction (XRD) analysis indicated that spheres consisted of a main magnesium-substituted strontium phosphate phase ((Sr_0.86Mg_0.14)₃(PO₄)₂). The scanning electron microscopy (SEM) micrographs confirmed that spheres had hollow interiors (～350 nm size) and an average diameter of 850 nm. Spheres had a specific surface area of 30.5 m²/g, a mesoporous shell with an average pore size of 3.8 nm, and a pore volume of 0.14 cm³/g. These characteristics make them promising candidates for drug, cell and protein delivery. For the attachment of spheres to scaffolds’ surface, ceramic structures were immersed in an ethanol solution containing 0.1 g of hollow spheres and kept at 37 °C for 4 h. The scaffolds with incorporated spheres were bioactive after being immersed in simulated body fluid (SBF) for 7 days and spheres were still adhered to their surface after 14 days.     

Oral drug delivery platforms for biomedical applications

Oral administration is perhaps the most commonly used and acceptable route for drug delivery to patients, mainly due to its non-invasiveness, simplicity, and versatility. Conventional delivery media such as tablets or capsule-based formulations, however, could result in low drug bioavailability and insufficient therapeutic efficiency, especially for delivering biologics (e.g., peptide, protein, antibody, nucleic acid). Therefore, with the advancement of material science and micro-/nano-fabrication techniques, various carriers have been developed to protect drugs and improve their absorption in the gastrointestinal (GI) tract. Herein, we first summarized various types of drug molecules being used for oral administration. Then we discussed the major physiological barriers (including various biochemical, mucosal diffusion, and cellular permeation barriers) that hinder drug transportation and absorption, as well as the main targeting regions in the GI tract. On this basis, we reviewed recently emerged oral drug delivery platforms and discussed their widely investigated biomedical applications. Finally, we present future perspectives for materials science-enabled oral drug delivery platforms, and potential challenges for clinical translation.