Álvaro J. Leite

Chitosan/bioactive glass nanoparticles scaffolds with shape memory properties.

We propose a combination of chitosan (CHT) with bioactive glass nanoparticles (BG-NPs) in order to produce CHT/BG-NPs scaffolds that combine the shape memory properties of chitosan and the biomineralization ability of BG-NPs for applications in bone regeneration. The addition of BG-NPs prepared by a sol-gel route to the CHT polymeric matrix improved the bioactivity of the nanocomposite scaffold, as seen by the precipitation of bone-like apatite layer upon immersion in simulated body fluid (SBF). Shape memory tests were carried out while the samples were immersed in varying compositions of water/ethanol mixtures. Dehydration with ethanol enables to fix a temporary shape of a deformed scaffold that recovers the initial geometry upon water uptake. The scaffolds present good shape memory properties characterized by a recovery ratio of 87.5% for CHT and 89.9% for CHT/BG-NPs and a fixity ratio of 97.2% for CHT and 98.2% for CHT/BG-NPs (for 30% compressive deformation). The applicability of such structures was demonstrated by a good geometrical accommodation of a previously compressed scaffold in a bone defect. The results indicate that the developed CHT/BG-NPs nanocomposite scaffolds have potential for being applied in bone tissue engineering.

Bioplotting of a bioactive alginate dialdehyde-gelatin composite hydrogel containing bioactive glass nanoparticles

Alginate dialdehyde-gelatin (ADA-GEL) constructs incorporating bioactive glass nanoparticles (BGNPs) were produced by biofabrication to obtain a grid-like highly-hydrated composite. The material could induce the deposition of an apatite layer upon immersion in a biological-like environment to sustain cell attachment and proliferation. Composites were formulated with different concentrations of BGNPs synthetized from a sol-gel route, namely 0.1% and 0.5% (w/v). Strontium doped BGNPs were also used. EDS analysis suggested that the BGNPs loading promoted the growth of bone-like apatite layer on the surface when the constructs were immersed in a simulated body fluid. Moreover, the composite constructs could incorporate with high efficiency ibuprofen as a drug model. Furthermore, the biofabrication process allowed the successful incorporation of MG-63 cells into the composite material. Cells were distributed homogeneously within the hydrogel composite, and no differences were found in cell viability between ADA-GEL and the composite constructs, proving that the addition of BGNPs did not influence cell fate. Overall, the composite material showed potential for future applications in bone tissue engineering.

The potential of cashew gum functionalization as building blocks for layer-by-layer films

Cashew gum (CG), an exudate polysaccharide from Anacardium occidentale trees, was carboxymethylated (CGCm) and oxidized (CGO). These derivatives were characterized by FTIR and zeta potential measurements confirming the success of carboxymethylation and oxidation reactions. Nanostructured multilayered films were then produced through layer-by-layer (LbL) assembly in conjugation with chitosan via electrostatic interactions or Schiff bases covalent bonds. The films were analyzed by QCM-D and AFM. CG functionalization increased the film thickness, with the highest thickness being achieved for the lowest oxidation degree. The roughest surface was obtained for the CGO with the highest oxidation degree due to the predominance of covalent Schiff bases. This work shows that nanostructured films can be assembled and stabilized by covalent bonds in alternative to the conventional electrostatic ones. Moreover, the functionalization of CG can increase its feasibility in multilayers films, widening its potential in biomedical, food industry, or environmental applications.

Bioactive Composites Reinforced with Inorganic Glasses and Glass–Ceramics for Tissue Engineering Applications

Bioactive composites, prepared by the combination of glasses or glass–ceramics with natural or synthetic polymers or blends, have been extensively exploited in bone tissue engineering. Their bioactive character is usually derived from the glass or glass–ceramic phase and is one of the most relevant properties to generate bone bonding. Herein we focus on the development of bioactive composite structures that target tissue engineering applications, with special emphasis on bone regeneration. Some concepts, e.g., bioactivity and biocompatibility, are initially introduced, followed by a description of the synthetic approaches that have been reported for the preparation of bioactive inorganic glasses or glass–ceramics. Different strategies to compound these inorganic particles with polymeric phases are detailed, spanning from conventional methodologies and wet spinning to rapid prototyping. Finally, a series of systems that have been developed for bone tissue engineering are described (including injectable systems, 3D scaffolds, membranes, and biomimetic layer-by-layer structures), as well as their in vitro biological response.

Bioactive Hydrogel Marbles

Liquid marbles represented a significant advance in the manipulation of fluids as they used particle films to confine liquid drops, creating a robust and durable soft solid. We exploit this technology to engineering a bioactive hydrogel marble (BHM). Specifically, pristine bioactive glass nanoparticles were chemically tuned to produce biocompatible hydrophobic bioactive glass nanoparticles (H-BGNPs) that shielded a gelatin-based bead. The designed BHM shell promoted the growth of a bone-like apatite layer upon immersion in a physiological environment. The fabrication process allowed the efficient incorporation of drugs and cells into the engineered structure. The BHM provided a simultaneously controlled release of distinct encapsulated therapeutic model molecules. Moreover, the BHM sustained cell encapsulation in a 3D environment as demonstrated by an excellent in vitro stability and cytocompatibility. The engineered structures also showed potential to regulate a pre-osteoblastic cell line into osteogenic commitment. Overall, these hierarchical nanostructured and functional marbles revealed a high potential for future applications in bone tissue engineering.

Chapter 8:Bioactive Nanoparticles, Nanofibers, and Polymeric Nanocomposites

Bioactive glasses have been mainly proposed to be used in bone tissue engineering, but recent studies are also showing promising results of their applicability in soft tissue regeneration. The new discoveries in tissue engineering request the development of more sophisticated and efficient biomaterials. Researchers are being inspired by the hierarchical architecture of biological tissues, trying to mimic their nanostructure to develop new devices and materials. This chapter will focus on recent advances in the nanoscale design of bioactive glasses towards the development of bioactive glass nanofibers and nanoparticles. The fabrication technologies are also addressed. Polymeric materials exhibit suitable mechanical and processing capabilities but lack the bioactivity of bioactive glasses. Therefore, the state-of-the-art nanostructured polymeric composites and the recent advances are also considered. Various types of polymeric nanocomposites used in tissue engineering are reviewed regarding the impact of nanoscale bioactive glasses on the mechanical properties, bioactivity and cell behaviour. The future perspectives of nanoscale bioactive glasses for tissue engineering are also discussed.