Publications

Despite significant efforts in developing novel biomaterials to regenerate tissue, only a few of them have successfully reached clinical use. It has become clear that the next generation of biomaterials must be multifunctional. Smart biomaterials can respond to environmental or external stimuli, interact in a spatial-temporal manner, and trigger specific tissue/organism responses. In this study, the fabrication of novel 3D-printed and bioresorbable scaffolds, with embedded crystals that can convert near-infrared (NIR) light into visible light, is presented. It is demonstrated that these biophotonic scaffolds are not only bioactive and bioresorbable, but can also be promising as a platform for the controlled release or activation of photoactivated drugs locally and on demand, under illumination. The scaffolds are analyzed based on their up-conversion spectroscopic properties and their chemical stability in simulated body fluid. Furthermore, it is demonstrated that the up-conversion properties of the scaffolds are sufficient to release the signaling molecule nitric oxide (NO) and to photoisomerize the muscarinic ligand Phthalimide-Azo-Iperoxo (PAI), in a controlled manner, upon NIR light stimulus. Finally, to assess their biocompatibility for potential implantation, a preliminary study is conducted with human adipose stem cells cultured in contact with scaffolds. Live/dead assays, morphological analysis, CyQUANT analysis, and ion release measurements confirm that, despite some release of the upconverter crystals, the biophotonic materia and its dissolution by-products, are biocompatible. These findings highlight the potential of these bioresorbable biophotonic scaffolds for localized drug release in response to NIR light stimuli.

JTD Keywords: 45s, 45s5, Bioactive glass scaffolds, Borate, Bulk, Drug targeting, Implants, Luminescence, Nitric oxide, Optopharmacology, Photopharmacology, Phototherapeutic window, Silicate, System, Upconversio, Upconversion

Quantitative measurement of the low-frequency dielectric constants of thick insulators at the nanoscale is demonstrated utilizing ac electrostatic force microscopy combined with finite-element calculations based on a truncated cone with hemispherical apex probe geometry. The method is validated on muscovite mica, borosilicate glass, poly(ethylene naphthalate), and poly(methyl methacrylate). The dielectric constants obtained are essentially given by a nanometric volume located at the dielectric-air interface below the tip, independently of the substrate thickness, provided this is on the hundred micrometer-length scale, or larger.

JTD Keywords: Borosilicate glasses, Finite element analysis, Insulating thin films, Mica, Nanostructured materials, Permittivity, Polymers, Scanning probe microscopy