The improper disposal of toxic and carcinogenic organic substances resulting from the manufacture of dyes, drugs and pesticides can contaminate aquatic environments and potable water resources and cause serious damage to animal and human health and to the ecosystem. In this sense, heterogeneous photocatalysis stand out as one effective and cost-effective water depollution technique. The use of metal oxide nanocomposites (MON), from the mixture of two or more oxides or between these oxides and other functional semiconductor materials, have gained increasing attention from researchers and industrial developers as a potential alternative to produce efficient and environmentally friendly photocatalysts for the remediation of water contamination by organic compounds. Thus, this work presents an updated review of the main advances in the use of metal oxide nanocomposites-based photocatalysts for decontamination of water polluted by these substances. A bibliometric analysis allowed to show the evolution of the importance of this research topic in the literature over the last decade. The results of the study also showed that hierarchical and heterogeneous nanostructures of metal oxides, as well as conducting polymers and carbon materials, currently stand out as the main materials for the synthesis of MON, with better photocatalysis performance in the degradation of dyes, pharmaceuticals and pesticides.

Metal oxide nanocomposites (MON) have gained significant attention in the literature for the possibility of improving the optical and electronic properties of the hybrid material, compared to its pristine constituent oxides. These superior properties have been observed for TiO₂ — based MON, which exhibit improved structural stability and photoactivity in environmental decontamination processes. In addition, the use of polymer membrane-supported MON is preferable to prevent further aggregation of particles, increase the surface area of the semiconductor in contact with the contaminant, and enable material reuse without considerable efficiency loss. In this work, $\mathrm{V}$⁵⁺-doped ${\mathrm{TiO}}_2/{\mathrm{WO}}_3 \mathrm{MON}$ nanostructures were prepared by the sintering process at 500 °C and supported in electrospun fiber membranes for application as photocatalyst devices. Microstructural characterization of the samples was performed by XRD, SEM, EDS, Raman, and DSC techniques. The reflectance spectra showed that the bandgap of the MON was progressively decreased (3.20 to 2.11 eV) with the V⁵⁺ ions doping level increase. The fiber-supported MON showed photoactivity for rhodamine B dye degradation using visible light. In addition, the highest photodegradation efficiency was noted for the systems with 5 wt% vanadium oxide dispersed in the fibers (92% dye degradation in 120 min of exposure to the light source), with recyclability of the composite material for use in new photocatalysis cycles. The best results are directly related to the microstructure, lower bandgap and aggregation of metal oxide nanocomposite in the electrospun membrane, compared to the support-free MON.

The importance of the Eudragit^® E100 copolymer (E100) is recognized in the pharmaceutical industry as a pH-dependent coating material in conventional oral administration dosage applications, where a modified release profile is required. On the other hand, its arrangement for 3D printing of cylindrical-shaped filaments containing drugs (to produce customized pharmaceuticals), is still scarce in the literature, and is currently an open field of research. One of the main challenges involves the manufacture of filaments that are flexible and functional, as their cylindrical shape (which is necessary for its use on FDM 3D printers) significantly increases the material’s fragility. Thus, the objective of this work was to prepare and characterize E100/Hesperidin (Hsp) filaments, and to study in vitro dissolution from Hsp active molecules of this unconventional polymeric matrix. The hybrid filaments were produced using a surface chemical treatment of the material resulting from a hot-melt extrusion process. The microstructural characterization of the filaments was performed using SEM, XRD, FTIR and ATR. The thermal analysis of the materials was performed using DSC, and the mechanical resistance was analyzed using flexural testing. The in vitro release profiles of the filament-arranged drug were evaluated in solutions of simulated gastro and intestinal fluids.

The process of manufacturing drug delivery systems (DDSs) by fused deposition modeling (FDM) with 3D printing requires the availability of a polymeric filament containing the drug of interest. This filament is fused in the printer heating system and used to print polymer/drug volumetric parts. Polymers with pH-dependent solubility are widely known in the literature for their controlled release and drug dissolution-enhancing properties, biocompatibility, and variety of release profiles. Given these characteristics, the study of pH-responsive 3D printing filaments appears as a potential alternative for the development of new 3D printing functional materials for healthcare area applications. In this sense, this work aimed at the preparation and characterization of pH-dependent filaments of the Eudragit E 100 copolymer (E100) containing the model drug Amlodipine (Aml) for potential application in the manufacturing of DDSs by 3D printing. The E100/Aml filaments with two distinct drug concentrations were produced by hot-melt extrusion at 105 °C. The posterior chemical protonation treatment of the filaments for 60 min provided a significant improvement in their flexibility. Microstructural analysis (SEM, XRD, FTIR, and DLS) and thermal studies by DSC proved the feasibility of producing the filaments by hot-melt extrusion without the degradation of their constituent materials. The in vitro dissolution profiles of the E100/Aml samples were evaluated in simulated gastric and intestinal fluids. The facilitated solubility of the polymer in an acidic medium (pH = 1.2) was preserved in the filament form, with rapid and reproducible drug release from the polymer matrix. The saturation of the drug concentration in the medium occurred after 30 min of testing for E100/Aml models. A customized 3D part with geometry and fill control was also printed from E100/Aml filaments as proof of concept.

Fused deposition modeling (FDM) 3D printing is characterized as a technology for manufacturing three-dimensional objects through the deposition of successive layers of molten material onto a build platform, based on a user-defined design. The development of non-conventional polymer-based filaments incorporating carbon-based semiconducting materials represents an open field of research in both academia and industry, with applications in emerging areas such as supercapacitors, photocatalysts, and sensors. This paper investigates the development of non-conventional filaments for FDM 3D printing based on polylactic acid (PLA) and reduced graphene oxide (rGO) nanoparticles, aiming to obtain electrically conductive properties for emerging applications in nanoelectronics. The composites were prepared by dispersing rGO in a PLA solution using chloroform as solvent, followed by controlled evaporation, oven drying, and hot melt extrusion of filaments with different rGO mass concentrations (0%–15% w w ⁻¹ ), all showing good reproducibility. Sample characterization was carried out using scanning electron microscopy, x-ray diffraction, differential scanning calorimetry, mechanical strength tests, and electrical resistivity measurements. The results revealed a typical electrical percolation behavior with a reduction in resistivity by 6 orders of magnitude (∼200 MΩ cm to ∼300 Ω cm), with a percolation threshold around 3.95% rGO. The rate of change in resistivity became less evident for the samples containing 9.1% or more of rGO, while filament processability was maintained up to 15% rGO, above which excessive stiffness was observed. Additional tests demonstrated the feasibility of printing three-dimensional structures with low electrical resistance, with potential for use in personalized functional devices.

The aim of this study was to develop sustainable films based on collagen recovered from tanned leather waste with Hymenaea martiana stem extracts (HMEC) obtained by microextraction, with an emphasis on evaluating their physical and chemical properties. The phytochemical analysis of HMEC revealed a high content of phenolics (396.6 mg of gallic acid equivalents per gram of extract (mg EAG g–1) and flavonoids (296.2 mg of catechin equivalents per gram of extract (mg EC g–1)), with a predominance of flavonoids (74.7%). The liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-Q-TOF-MS) characterization evidenced a wide diversity of secondary metabolites, highlighting flavonoids such as fustin, isokaempferide, liquiritigenin, myricitrin, quercitrin, and quercetin derivatives, in addition to compounds such as quinic acid and glycosides. Furthermore, hydrolyzed collagen obtained from leather industry waste was combined with polyvinyl alcohol (PVA), glycerol, and different concentrations of HMEC to produce the films. The films exhibited high tensile strength (3833-4570 mPa), a significant increase in elongation at break (187.5-311.1%), and a swelling rate of up to 624.2% in samples with 3% HMEC, retaining 70% moisture after 18 h. The results highlight the great potential of these films for wound treatment and reinforce the sustainable reuse of leather industry waste.