Mónica Cicuéndez

Novel biopolymer-coated hydroxyapatite foams for removing heavy-metals from polluted water.

3D-macroporous biopolymer-coated hydroxyapatite (HA) foams have been developed as potential devices for the treatment of lead, cadmium and copper contamination of consumable waters. These foams have exhibited a fast and effective ion metal immobilization into the HA structure after an in vitro treatment mimicking a serious water contamination case. To improve HA foam stability at contaminated aqueous solutions pH, as well as its handling and shape integrity the 3D-macroporous foams have been coated with biopolymers polycaprolactone (PCL) and gelatine cross-linked with glutaraldehyde (G/Glu). Metal ion immobilization tests have shown higher and fast heavy metals captured as function of hydrophilicity rate of biopolymer used. After an in vitro treatment, foam morphology integrity is guaranteed and the uptake of heavy metal ions rises up to 405 μmol/g in the case of Pb(2+), 378 μmol/g of Cu(2+) and 316 μmol/g of Cd(2+). These novel materials promise a feasible advance in development of new, easy to handle and low cost water purifying methods.

Biocompatibility and levofloxacin delivery of mesoporous materials.

A comparative study of mesoporous matrices designed for both drug-loading methods, impregnation (IP) and surfactant-assisted drug loading (also denoted as one-pot, OP), has been carried out evaluating their physicochemical characteristics, cell response, drug delivery profiles, and antibacterial activity. Surfactant-free (calcined) and surfactant-templated (non-calcined) mesoporous silica have been used as IP and OP starting matrices, respectively. Both non-calcined and calcined matrices do not exert any cytotoxic effect on osteoblasts. However, non-calcined matrices induce on fibroblasts a significant proliferation delay with morphological alterations and dose-dependent increases in fibroblast size, internal complexity, and intracellular calcium content but without cell lysis and apoptosis. Residual ethanol and the surface silanol groups in these non-calcined matrices are involved in the observed fibroblast changes. Finally, both IP and OP matrices have been loaded with levofloxacin to compare them as drug delivery systems. Both IP and OP matrices exhibit similar in vitro levofloxacin release profiles, showing an initial fast delivery followed by a sustained release during long time periods. These profiles and the antimicrobial activity results suggest the use of these IP and OP matrices as local drug delivery systems in the osteomyelitis and other bone infection treatments.

Biological performance of hydroxyapatite–biopolymer foams: In vitro cell response

Uncoated and biopolymer-coated nanocrystalline hydroxyapatite (HA) macroporous foams are presented as promising candidates as scaffolds for bone tissue regeneration. To this end, foam degradability, the cytotoxic effects on osteoblast-like cells of foam degradation by-products and biocompatibility with osteoblast-like cells were assayed on the three-dimensional (3-D) foam surface. The results show that the 3-D interconnected architectural design of these HA foams allows excellent osteoblast internalization, proliferation and differentiation, exhibiting adequate colonization over the entire scaffold surface with an appropriate degradation rate without any cytotoxic effects.

Tailoring hierarchical meso–macroporous 3D scaffolds: from nano to macro

Bone tissue regeneration requires the use of 3D scaffolds which mimic the architecture of the natural extracellular matrix, creating an adequate microenvironment for bone cell growth. Such 3D scaffolds need surface properties suitable for biological recognition in the early stage of cell adhesion, necessary to ensure complete cell colonization, retained cell functionality, and subsequently bone regeneration. Herein, hierarchical 3D scaffolds based on new hydroxyapatite/mesoporous glass nanocomposite bioceramic (MGHA) exhibiting different scales of porosity have been synthesized. These 3D scaffolds possess: (i) highly ordered mesopores with diameters of 10 nm; (ii) macropores with diameters in the 30-80 μm range with interconnections of 1-10 μm; and (iii) large macropores of ca. 500 μm. To improve their surface properties, 3D scaffolds were modified through direct functionalization with amine propyl groups, which notably improve preosteoblast adhesion, proliferation (2.3 fold), differentiation (4.8 fold) and further cell colonization of these scaffolds. The observed enhancement can be related to these amine groups which favour early adhesion, e.g., based on nonspecific protein adsorption as was demonstrated by ellipsometry. These results suggest that the combination of hierarchical structure design and amine surface modification of hydroxyapatite/mesoporous nanocomposite scaffolds yields a double increase in cell proliferation, as well as a quadruple increase in cell differentiation, demonstrating the potential of these nanocomposite materials for bone tissue regeneration purposes.

Electrical stimuli to increase cell proliferation on carbon nanotubes/mesoporous silica composites for drug delivery

The development of smart materials as bone implants is nowadays a challenging task to optimize their fast osteointegration. Nevertheless, no attempts have been done in joining the possibility of using electrical stimulation and drug delivery together in a material intended for bone tissue engineering. Moreover, the use of this synergy to induce bone healing is still limited until novel drug reservoirs material formulations allow an efficient applicability of the electrical stimuli. Herein, we present the biological response of osteoblasts cells, cultured over carbon nanotubes-mesoporous silica composites while exposed to external electrical stimulus. Moreover, its ability to function as drug delivery systems is also demonstrated. Bone cell metabolism was stimulated and mitochondrial activity was increased up to seven times in the presence of these composites under electrical stimulus, suggesting their potential application in bone regeneration processes.

Mesoporous Silica Nanoparticles Decorated with Carbosilane Dendrons as New Non‐viral Oligonucleotide Delivery Carriers

A novel nanosystem based on mesoporous silica nanoparticles covered with carbosilane dendrons grafted on the external surface of the nanoparticles is reported. This system is able to transport single-stranded oligonucleotide into cells, avoiding an electrostatic repulsion between the cell membrane and the negatively charged nucleic acids thanks to the cationic charge provided by the dendron coating under physiological conditions. Moreover, the presence of the highly ordered pore network inside the silica matrix would make possible to allocate other therapeutic agents within the mesopores with the aim of achieving a double delivery. First, carbosilane dendrons of second and third generation possessing ammonium or tertiary amine groups as peripheral functional groups were prepared. Hence, different strategies were tested in order to obtain their suitable grafting on the outer surface of the nanoparticles. As nucleic acid model, a single-stranded DNA oligonucleotide tagged with a fluorescent Cy3 moiety was used to evaluate the DNA adsorption capacity. The hybrid material functionalised with the third generation of a neutral dendron showed excellent DNA binding properties. Finally, the cytotoxicity as well as the capability to deliver DNA into cells, was tested in vitro by using a human osteoblast-like cell line, achieving good levels of internalisation of the vector DNA/carbosilane dendron-functionalised material without affecting the cellular viability.

Biopolymer-coated hydroxyapatite foams: a new antidote for heavy metal intoxication

Novel 3D-macroporous biopolymer-coated hydroxyapatite foams are potential devices for the treatment of heavy-metal intoxication by ingestion. These foams are designed to exhibit a fast and efficient metal ion immobilization into the HA structure in acidic media. The capture process of metal ions is stable, not releasing any metal ion when the foams are soaked in clean basic media afterwards. These two steps mimic a digestion process.

Aqueous Exfoliation of Transition Metal Dichalcogenides Assisted by DNA/RNA Nucleotides: Catalytically Active and Biocompatible Nanosheets Stabilized by Acid–Base Interactions

The exfoliation and colloidal stabilization of layered transition metal dichalcogenides (TMDs) in an aqueous medium using functional biomolecules as dispersing agents have a number of potential benefits toward the production and practical use of the corresponding two-dimensional materials, but such a strategy has so far remained underexplored. Here, we report that DNA and RNA nucleotides are highly efficient dispersants in the preparation of stable aqueous suspensions of MoS2 and other TMD nanosheets at significant concentrations (up to 5-10 mg mL-1). Unlike the case of common surfactants, for which adsorption on 2D materials is generally based on weak dispersive forces, the exceptional colloidal stability of the TMD flakes was shown to rely on the presence of relatively strong, specific interactions of Lewis acid-base type between the DNA/RNA nucleotide molecules and the flakes. Moreover, the nucleotide-stabilized MoS2 nanosheets were shown to be efficient catalysts in the reduction of nitroarenes (4-nitrophenol and 4-nitroaniline), thus constituting an attractive alternative to the use of expensive heterogeneous catalysts based on noble metals, and exhibited an electrocatalytic activity toward the hydrogen evolution reaction that was not impaired by the possible presence of nucleotide molecules adsorbed on their active sites. The biocompatibility of these materials was also demonstrated on the basis of cell proliferation and viability assays. Overall, the present work opens new vistas on the colloidal stabilization of 2D materials based on specific interactions that could be useful toward different practical applications.

Effects of 3D nanocomposite bioceramic scaffolds on the immune response

The interaction of new nanocomposite mesoporous glass/hydroxyapatite (MGHA) scaffolds with immune cells involved in both innate and acquired immunity has been studied in vitro as an essential aspect of their biocompatibility assessment. Since the immune response can be affected by the degradation products of bioresorbable scaffolds and scaffold surface changes, both processes have been evaluated. No alterations in proliferation and viability of RAW-264.7 macrophage-like cells were detected after culture on MGHA scaffolds which did not induce cell apoptosis. However, a slight cell size decrease and an intracellular calcium content increase were observed after contact of this cell line with MGHA scaffolds or their extracts. Although no changes in the percentages of RAW cells with low and high contents of reactive oxygen species (ROS) are observed by the treatment with 7 day extracts, this study has revealed modifications of these percentages after direct contact with scaffolds and by the treatment with 24 h extracts, related to the high reactivity/bioactivity of this MGHA nanocomposite at initial times. Furthermore, when normal fresh murine spleen cells were used as an experimental model closer to physiological conditions, no significant alterations in the activation of different immune cell subpopulations were detected in the presence of 24 h MGHA extract. MGHA scaffolds did not affect either the spontaneous apoptosis or intracellular cytokine expression (IL-2, IL-10, IFN-γ, and TNF-α) after 24 h treatment. The results obtained in the present study with murine immune cell subpopulations (macrophages, lymphocytes B, lymphocytes T and natural killer cells) support the biocompatibility of the MGHA material and suggest an adequate host tissue response to their scaffolds upon their implantation.

MC3T3-E1 pre-osteoblast response and differentiation after graphene oxide nanosheet uptake

Nano-graphene oxide (GO) and its functionalized derivatives have aroused a great interest for drug delivery, tissue engineering and photothermal cancer therapy, but their biocompatibility has not yet been fully assessed. The aim of the present study was to evaluate the proliferation and differentiation of MC3T3-E1 pre-osteoblasts after the uptake of GO nanosheets (c.a. 400nm), functionalized with poly(ethylene glycol-amine) (PEG) and labelled with fluorescein isothiocyanate (FITC). Significant proliferation decrease and apoptosis increase were observed 3days after incorporation of FITC-PEG-GO by MC3T3-E1 cells. However, alterations on healthy pre-osteoblast differentiation into cells exhibiting osteoblast phenotype were not observed, as they showed normal alkaline phosphatase levels and matrix mineralization 12days after nanosheet uptake. The results suggest that 40μg/mL concentrations of these nanosheets would not affect the differentiation of healthy pre-osteoblasts, thus these PEG-GO nanosheets have potential to be used for biomedical applications after their internalization, as the induction of local hyperthermia on bone cancer.