Introduction: 3D printing has emerged as a promising technique for fabricating permanent dental ceramic restorations. However, there is limited literature regarding aesthetic ceramics for monolithic restorations, such as 5 mol% yttria partially stabilized zirconia (5Y-PSZ). Therefore, the aim of this study was to investigate the influence of printing layer orientation and finishing protocol on the fracture behavior of 5Y-PSZ by stereolithography (SLA) 3D printing.

Materials and Methods: Bar-shaped 5Y-PSZ specimens were 3D-printed via SLA, followed by debinding and sintering. The dimension of the as-sintered specimens was 1.0 mm x 1.0 mm x 12.0 mm. The specimens were randomly divided into two groups according to printing layer orientations: parallel or perpendicular to the tensile surface in the following bending test. The specimens of each printing layer orientation were subsequently submitted to different surface finishing protocols: as-sintered, polished, and glazed. The fracture strength of each group was determined using a ball-in-hole device. The fractured specimens were examined under a scanning electron microscope to identify the fracture origin.

Results: Two-way analyses of variance showed significant effects of printing layer orientation (p<0.001) and finishing protocol (p<0.001), while the interaction of factors was not significant (p=0.195). The parallel orientation (639.9 ± 98.6 MPa) was stronger than the perpendicular (506.9 ± 47.9 MPa) for the as-sintered specimens. Polishing significantly improved the strength for both parallel (782.0 ± 134.0 MPa)^A and perpendicular (644.6 ± 159.8 MPa)^B orientations. While glazing did not have a significant effect on the strength for both orientations, the glazed perpendicular specimen (622.8 ± 96.7 MPa)^B presented similar strength to the glazed parallel specimens (580.9 ± 116.9 MPa)^B.

Conclusion: Both printing layer orientation and finishing protocol affect the fracture strength of 3D-printed 5Y-PSZ. Despite some differences, polishing and glazing are acceptable surface finishing protocols for 3D-printed ceramic restorations in terms of strength.

Fresh 3D printing allows tissue and organ equivalents to be prototyped for biomedical applications by extruding hydrogel "ink" into a bath with a supportive gel containing an active crosslinking component. The aim of this work is to select the conditions for the formation of a supportive gelatin matrix, to obtain hydrogel inks and functional products based on esterified pectin.
The following research objects were selected: aqueous solutions of thermally reversible gelatin protein (2.5-3 wt. %) and UP (2-6 wt. %), as well as solutions of CaCl2, an ion-type crosslinking agent for UP, selected in a molar ratio.
As a result of the research work, cooling curves of gelatin and UP solutions were obtained, presented in Arrhenius coordinates, on the basis of which the values of the activation energy of the viscous flow and the gelation process were obtained. The concentration dependences of the gelation temperature and dynamic viscosity were obtained, and the effect of concentration on the mechanism of structure formation was studied. The concentration dependences of dynamic viscosity indices on pH for equiviscid and equiconcentrated solutions are investigated. The working concentrations of a gelatin-based hydrogel bath and UP ink have been established. The effect of the molar content of calcium chloride on the mechanism and rate of Ca2+-induced gelation of unipectin working solutions has been studied. The strength characteristics of gel systems and the frame-type products based on them were determined using a rupture testing machine (RKM X.1.01 PS, Russia). A complex of biological tests of the cytocompatibility and hemocompatibility of the hydrogel components of the system was carried out.
Based on the conducted research, it was found that the implemented approach to the adaptation of hydrogels based on esterified pectin opens up new opportunities for the production of carcass structures using the technology of fresh printing on a 3D bioprinter (Fabion, Russia).

Bone tissue regeneration has become increasingly important due to the challenges posed by critical-sized injuries, pathology, or disease. Tissue engineering offers a promising approach to repair and regenerate damaged bone tissue. To achieve this, emerging technologies such as 3D bioprinting have been proposed for designing microarchitectures through layer-by-layer extrusion using different biopolymers or hydrogels such as alginate and gelatin, which, due to their malleability and biocompatibility, facilitate the generation of cell-laden scaffolds that could restore bone defect functionality.

This work aimed to synthesize a 3D bioprinting scaffold with a bioink combination of alginate–gelatin with and without fetal osteoblasts. The scaffold's characterization by FTIR showed the characteristic signals of the bioink components, while SEM analysis showed the porous structure morphology of the 3D-printed scaffold and the cell–material interaction.

The biological response when osteoblasts were seeded over the surface and use as part of the bioink showed good adhesion and biocompatibility over the 21 days of culture. Moreover, alizarin red staining showed that osteogenic factors improved the quantity of calcium deposits in both assays for calcium deposit evaluation.

In conclusion, our results showed that the bioink based on alginate and gelatin allows for a stable 3D-printed scaffold, supporting the osteoblasts' viability and cell growth and bone extracellular matrix deposition. The authors want to thank the financial support of CONAHCYT for the scholarship granted for the master study of DVH with CVU: 1190428, and the financial support given by the DGAPA-UNAM-PAPIIT IN202924 project.

Microfibrillated cellulose (MFC) is a natural material that can be extracted from the plant cell wall. It has attractive properties such as high strength, excellent stiffness, and high surface area, but its hydroxylated surface is often pointed out as a limiting factor for its use in commercial applications. MFC cannot be ideally dispersed in non-polar solvents, monomers, or polymers since the hydrophilic surface of MFC is incompatible with hydrophobic environments. The complete dissolution of cellulose in a solvent system is complex. A cyclotetrasiloxane was synthesized via hydrosilylation of 1, 3, 5, 7-tetramethylcyclotetrasiloxane (D₄H) with Trimethoxyvinylsilane (TMVS). The structure of tetramethylcyclotetrasiloxane modified with Trimethoxyvinylsilane (D₄H– TMVS) was characterized by Fourier-transform infrared (FT-IR) and 1H nuclear magnetic resonance (¹H-NMR). This cyclotetrasiloxane bound to cellulose and then polymerized it by ring-opening polymerizations (ROPs) with an initiator in a second step. Polysiloxanes are useful for conferring chain flexibility, biointegrity, radiation resistance, thermal stability, and hydrophobicity. With an appropriate degree of silylation, cellulose will disperse efficiently in organic solvents such as acetone, chloroform, and tetrahydrofuran. As a result, the possibility of using cellulose is increased in a number of different disciplines, such as antioxidants, bio-composites, biomedicine, carbon fiber, photo-catalysts and photovoltaics, the adsorption of heavy metal ions, and wood adhesives.

The goal of the research was to investigate the photocytotoxicity effect and target delivery of polyelectrolyte microcapsules loaded with the photosensitizer chlorin E6 (ClE6) and iron oxide nanoparticles on mouse hepatoma cells (Mh22a). Microcapsules were made by layer by layer (caps-ClE6). Polyelectrolyte layers (PAH and PSS) and iron oxide nanoparticles were alternately deposited on the spherical cores loaded with ClE6. After 24 h incubation of Mh22a with caps-ClE6 (20 caps/cell) and free ClE6 (11.2 μg/mL), the cells were irradiated by red light (660 nm and 60W) for 15 min (RL). The photocytotoxicity was evaluated using MTT colometric tests. The targeting in vitro was determined in a Petri dish after 24 h incubation of cells with caps-CLE6 on a permanent magnet and RL 15 min. The cell death was assessed using double staining (acridine orange and ethidium bromide). For caps-CLE6, the cell viability without RL was more than 70%. In the case of free ClE6, the viability was only 26%. After RL, cell death was 92% and 95% for caps-ClE6 and ClE6,respectively. ROS generation by caps-ClE6 was 2-fold higher compared to free ClE6. After incubation of Mh22a with caps-CLE6 on a permanent magnet and RL, fluorescence microscopy showed almost complete cell death by necrosis and apoptosis and no cell death outside the magnet. Thus, Caps-CLE6 had less dark cytotoxicity with the phototoxicity effect via RL, and could be concentrated with magnets.

Introduction. The development of targeted delivery systems (DSs), including DSs with controlled release, e.g., photoinduced release, is considered to be one of the most promising directions of antitumour therapy development. The increasing morbidity of patients with non-small cell lung cancer makes it urgent to improve the therapy of this disease. One of the effective drugs in the treatment of this disease is Gefitinib (Gef); however, Gef is used in the form of tablets, and its bioavailability is about 50%. In this regard, the development of DSs with photoinduced release for Gefitinib is very promising, and their use will improve the safety profile of the drug and reduce undesirable effects.

Methods. The combined DSs were prepared by the following methods: 1. liposomes were obtained by the lipid film; 2. micelles were emulsified by inert gas bubbling. The created model formulations were evaluated according to the particle size, ζ-potential, and content of active substances. The cytotoxic activity of the nanoconstructions was studied on the lung carcinoma cell line A549.

Results. In the process work, model formulations of DSs with different morphologies were created. From the proposed formulations, the most promising ones were selected according to the criteria of particle size (˂200 nm) and active substance inclusion (85-90%). The leader models were also tested for cytotoxic activity on A549 cells. It turned out that only in the micellar model did the toxicity index for irradiated and non-irradiated cells exceed 50%. This indicates the promising application of this model for further research.

Conclusions. In the course of this work, biopharmaceutical studies were carried out to substantiate the composition and technology of targeted DSs with photoinduced release of Gefitinib and to study the antitumour activity in vitro.

Funding. This study was supported by the Russian Science Foundation grant No. 23-75-01026 «Development of targeted combined structures based on phospholipid nanosystems for lung cancer therapy».

Introduction. The application of the photosensitizer methylene blue (MB) in photodynamic therapy (PDT) is limited by the high risk of side effects. This restricts the possibility of using MB for highly effective PDT. This study presents the development of a new strategy for local PDT based on MB adsorbed on a photocatalyst—hexagonal boron nitride nanoparticles (h-BN).

Materials and Methods. h-BN/n•MB heterostructures with a specified concentration (n) of MB were obtained by immobilizing MB on h-BN NPs using a controlled adsorption method. Characterization of h-BN/n•MB heterostructures was carried out using SEM, EDX, UV-Vis spectrophotometry, and fluorescence and FTIR spectroscopy. The level of ROS mediated by h-BN/n•MB heterostructures was determined via an amperometric method. The cytotoxicity of the material was assessed on human skin melanoma (A-375) and human fibroblast (Wi-38) cell lines.

Results. h-BN/MB heterostructures with MB concentrations of 100, 200, and 300 mg/g were fabricated. The results of fluorescence and FTIR spectroscopy indicate π-π stacking of MB and h-BN in these heterostructures. According to spectrophotometry, the desorption of MB is no more than 7 mass %, which confirms the high stability of the heterostructures. All h-BN/n•MB heterostructures generated a high level of ROS—up to 3.8 ×10-2 ±0.3×10-2 µM/µg within 24 hours after exposure to sunlight. Biological studies indicate the pronounced antitumor activity of the material, as well as its selective cytotoxicity to normal and cancer cells.

Conclusions. A new sunlight-activated platform for local PDT has been developed. h-BN/n•MB heterostructures demonstrate a high therapeutic potential due to their strong oxidative activity. The presented data confirm the feasibility of using heterostructures to enhance the photoefficiency of low doses of MB.
This research was funded by the Russian Science Foundation ( 20-19-00120-P).