Tailorable mechanical and degradation properties of KCl-reticulated and BDDE-crosslinked PCL/chitosan/κ-carrageenan electrospun fibers for biomedical applications: Effect of the crosslinking-reticulation synergy.

The development of intricated and interconnected porous mats is desired for many applications in biomedicine and other relevant fields. The mats that comprise the use of natural, bioactive, and biodegradable polymers are the focus of current research activities. In the present work, crosslinked fibers with improved characteristics were produced by incorporating 1,4-butanediol diglycidyl ether (BDDE) into a polymer formulation containing polycaprolactone (PCL), chitosan (CS), and κappa-carrageenan (κ-C). A slight variation of formic acid (FA)/acetic acid (AA) ratio used as a solvent system, significantly affected the characteristics of the produced fiber mats. Both polysaccharides and BDDE played a major role in tailoring mechanical properties when fibrous scaffolds were reticulated under KCl-mediated basic conditions for determined periods of time at 50 °C. In vitro biological assessment of the electrospun fiber mats revealed proliferation of MC3T3-E1 cells when incubated for 1 and 7 days. After staining the cells with 4',6-diamidino-2-phenylindole (DAPI)/rhodamine phalloidin an autofluorescence response was observed by fluorescence microscopy in the scaffold manufactured using a solvent with higher FA/AA ratio due to the formation of microfibers. The results demonstrated the potential of the BDDE-crosslinked PCL/CS/κ-C electrospun fibers as promising materials for biomedical applications that may include soft and bone tissue regeneration.

Environmentally friendly fabrication of electrospun nanofibers made of polycaprolactone, chitosan andκ-carrageenan (PCL/CS/κ-C).

Electrospun fibers based on biodegradable polyanionic or polycationic biopolymers are highly beneficial for biomedical applications. In this work, electrospun nanofibers made from poly(epsilon caprolactone) (PCL), chitosan (CS) andκ-carrageenan (κ-C) were successfully fabricated using several mixtures of benign solvents containing formic acid and acetic acid. The addition ofκ-C improved the preparation procedure for the production of PCL/CS fibers by electrospinning. Moreover, a polymer mixture was selected to be stored at -20 °C for one month with the purpose to study the properties of the resulting fiber mat. The results indicated that fiber characteristics were not seriously compromised compared to the ones of those fabricated with the original solution, which represents an important reduction in produced waste. Thus, the interactions that occur between positively and negatively charged hydrophilic polysaccharides might induce higher stability to the linear aliphatic polyester in the polymer mixture. All fiber mats were morphologically, physico-chemically and mechanically characterized, showing average fiber diameters in the nano scale. A direct cell viability assay using ST-2 cells demonstrated cell proliferation after seven days of incubation for all prepared fiber mats, confirming their suitability as potential candidates for bone tissue engineering and wound healing applications.

Exploiting the Potential of Supported Magnetic Nanomaterials as Fenton-Like Catalysts for Environmental Applications.

In recent years, the application of magnetic nanoparticles as alternative catalysts to conventional Fenton processes has been investigated for the removal of emerging pollutants in wastewater. While this type of catalyst reduces the release of iron hydroxides with the treated effluent, it also presents certain disadvantages, such as slower reaction kinetics associated with the availability of iron and mass transfer limitations. To overcome these drawbacks, the functionalization of the nanocatalyst surface through the addition of coatings such as polyacrylic acid (PAA) and their immobilization on a mesoporous silica matrix (SBA15) can be factors that improve the dispersion and stability of the nanoparticles. Under these premises, the performance of the nanoparticle coating and nanoparticle-mesoporous matrix binomials in the degradation of dyes as examples of recalcitrant compounds were evaluated. Based on the outcomes of dye degradation by the different functionalized nanocatalysts and nanocomposites, the nanoparticles embedded in a mesoporous matrix were applied for the removal of estrogens (E1, E2, EE2), accomplishing high removal percentages (above 90%) after the optimization of the operational variables. With the feasibility of their recovery in mind, the nanostructured materials represented a significant advantage as their magnetic character allows their separation for reuse in different successive sequential batch cycles.

Versatile Mesoporous Nanoparticles for Cell Applications.

Mesoporous silica nanostructures are emerging as a promising platform able to deal with challenges of many different applications in fields such as biomedicine and nanotechnology. The versatile physical and functional properties of these materials like high specific surface area, ordered porosity, chemical stability under temperature and pH variations, and biocompatible performance, offers new approaches to many biomedical applications ranging from drug delivery systems to biosensing, cell applications and tissue engineering. Their morphology, size and textural properties can be easily tailored by means of chemical control, giving rise to a variety of nanostructures with hexagonal (SBA15, MCM41) or cubic (SBA16) arrangement of channels and pore size ranging from 1.3 to 10 nm. Based on the versatility of their silane surface, a plethora of hybrid mesoporous matrices can be prepared incorporating new functionalities like contrast enhancement for magnetic resonance imaging, magnetic/plasmonic hyperthermia, drug delivery or cell applications by the simple grafting of superparamagnetic metal oxides (Fe3O4, transition metal ferrites) nanoparticles, noble metal (Au, Ag) nanoparticles, fluorescent moieties (fluorescein, rhodamine) or biological agents (mAb, mRNA, etc). The goal of this work is to present the development, by a facile soft template method, of size tailored mesoporous silica nanospheres from 20 to 350 nm (by means of chemical control), and highlight its versatility for surface grafting (with rhodamine and polydopamine) and their biological compatibility and efficient uptake by cultured HeLa cells. The combined, physicochemical and biological, properties indicate that MSNs are good candidates for cell tagging, gene transfer or targeted therapies.

Reusable Fe3O4/SBA15 Nanocomposite as an Efficient Photo-Fenton Catalyst for the Removal of Sulfamethoxazole and Orange II.

Today, the presence of recalcitrant pollutants in wastewater, such as pharmaceuticals or other organic compounds, is one of the main obstacles to the widespread implementation of water reuse. In this context, the development of innovative processes for their removal becomes necessary to guarantee effluent quality. This work presents the potentiality of magnetic nanoparticles immobilized on SBA-15 mesoporous silica as Fenton and photo-Fenton catalysts under visible light irradiation. The influence of the characteristics of the compounds and nanoparticles on the removal yield was investigated. Once the key aspects of the reaction mechanism were analyzed, to evaluate the feasibility of this process, an azo dye (Orange II) and an antibiotic (sulfamethoxazole) were selected as main target compounds. The concentration of Orange II decreased below the detection limit after two hours of reaction, with mineralization values of 60%. In addition, repeated sequential experiments revealed the recoverability and stability of the nanoparticles in a small-scale reactor. The benchmarking of the obtained results showed a significant improvement of the process using visible light in terms of kinetic performance, comparing the results to the Fenton process conducted at dark. Reusability, yield and easy separation of the catalyst are its main advantages for the industrial application of this process.

Hybrid mesoporous nanostructured scaffolds as dielectric biosimilar restorative materials.

BACKGROUND: The intricate structure of natural materials is in correspondence with its highly complex functional behaviour. The health of teeth depends, in a complex way, on a heterogeneous arrangement of soft and hard porous tissues that allow for an adequate flow of minerals and oxygen to provide continuous restoration. Although restorative materials, used in clinics, have been evolving from the silver amalgams to actual inorganic fillers, their structural and textural properties are scarcely biomimetic, hindering the functional recovery of the tissue. OBJECTIVE: The objective of this work is to compare and test the hybrid mesoporous silica-based scaffolds as candidates for dentine restoration applications. METHODS: In this work, we present the development and the physical properties study of biocompatible hybrid mesoporous nanostructured scaffolds with a chemically versatile surface and biosimilar architecture. We test their textural (BET) and dielectric permittivity (ac impedance) properties. RESULTS: These materials, with textural and dielectric properties similar to dentine and large availability for the payload of therapeutic agents, are promising candidates as functional restorative materials, suitable for impedance characterization techniques in dental studies. CONCLUSIONS: Structural, textural, morphological characterization and electrical properties of hybrid mesoporous show a large degree of similarity to natural dentin samples.

Multifunctional Superparamagnetic Stiff Nanoreservoirs for Blood Brain Barrier Applications.

Neurological diseases (Alzheimer's disease, Parkinson's disease, and stroke) are becoming a major concern for health systems in developed countries due to the increment of ageing in the population, and many resources are devoted to the development of new therapies and contrast agents for selective imaging. However, the strong isolation of the brain by the brain blood barrier (BBB) prevents not only the crossing of pathogens, but also a large set of beneficial drugs. Therefore, an alternative strategy is arising based on the anchoring to vascular endothelial cells of nanoplatforms working as delivery reservoirs. In this work, novel injectable mesoporous nanorods, wrapped by a fluorescent magnetic nanoparticles envelope, are proposed as biocompatible reservoirs with an extremely high loading capacity, surface versatility, and optimal morphology for enhanced grafting to vessels during their diffusive flow. Wet chemistry techniques allow for the development of mesoporous silica nanostructures with tailored properties, such as a fluorescent response suitable for optical studies, superparamagnetic behavior for magnetic resonance imaging MRI contrast, and large range ordered porosity for controlled delivery. In this work, fluorescent magnetic mesoporous nanorods were physicochemical characterized and tested in preliminary biological in vitro and in vivo experiments, showing a transversal relaxivitiy of 324.68 mM-1 s-1, intense fluorescence, large specific surface area (300 m² g-1), and biocompatibility for endothelial cells' uptake up to 100 µg (in a 80% confluent 1.9 cm² culture well), with no liver and kidney disability. These magnetic fluorescent nanostructures allow for multimodal MRI/optical imaging, the allocation of therapeutic moieties, and targeting of tissues with specific damage.