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Multicellular microtissues of primary human hepatocytes (PHHs) co-cultured with other supporting cell types are a promising model for drug screening and toxicological studies. However, these liver microtissues (LMs) rapidly lose their functions during ex vivo culture. Here, in order to mimic the cellular and structural hepatic microenvironment, we co-cultured PHHs with human mesenchymal stromal cells (MSCs) and human umbilical vein endothelial cells (HUVECs) in the presence of cell-sized microparticles (MPs) derived from liver extracellular matrix (LEMPs). The microwell culture platform enabled biofabrication of size-controlled multicellular microtissues (PHH:HUVEC:MSC = 3:2:1) with efficient LEMP incorporation (about 70% at a 2:1 ratio of cells:MP). The biofabricated liver microtissues (BLMs) were cultured ex vivo for 14 days and compared to the cell-only LM in terms of gene and protein expression, functional activity, cytochrome P450 (CYP450) enzyme inducibility, and drug sensitivity. The results supported superior hepatic-related gene expression, functional activity, and polarity for PHH in BLM compared to LM. CYP450 enzyme inducibility and dose-responsive sensitivity to toxic drugs were significantly higher in the BLM group. In conclusion, microtissue engineering by incorporation of tissue-specific microparticles within a multicellular microtissue can offer some advantages for drug discovery studies and cell transplantation applications. In the near future, this approach could generate a scalable platform of several functional biofabricated microtissues representing different organs.

The development of thermolabile substance carriers with a variable shape, size, and release kinetics is one of the most difficult goals of the pharmaceutical industry. Here, we propose to use the two-step combination of two-photon polymerization (2PP) and micromolding techniques to fabricate particles of a preset shape and size from star-shaped methacrylate functionalized poly(D,L)-lactides. Using a 2PP set-up, we fabricated an E-Shell cube-patterned matrix used to prepare a silicon mold. Then this mold was filled with functionalized poly(D,L)-lactides mixed with 4,4′-bis(dimethylamino)benzophenone as a photoinitiator and exposed to UV irradiation to crosslink particles which were further easily detached. The study revealed that the arm length of the functionalized polylactides caused differences in the mechanical properties and surface topography of the fabricated particles that determined their degradation rate, drug loading and release. Using the arm length as a structure parameter, one can prepare tailored polylactide particles with controllable substance release.

Biological self-assembly is crucial in the processes of development, tissue regeneration, and maturation of bioprinted tissue-engineered constructions. The cell aggregates—spheroids—have become widely used model objects in the study of this phenomenon. Existing approaches describe the fusion of cell aggregates by analogy with the coalescence of liquid droplets and ignore the complex structural properties of spheroids. Here, we analyzed the fusion process in connection with structure and mechanical properties of the spheroids from human somatic cells of different phenotypes: mesenchymal stem cells from the limbal eye stroma and epithelial cells from retinal pigment epithelium. A nanoindentation protocol was applied for the mechanical measurements. We found a discrepancy with the liquid drop fusion model: the fusion was faster for spheroids from epithelial cells with lower apparent surface tension than for mesenchymal spheroids with higher surface tension. This discrepancy might be caused by biophysical processes such as extracellular matrix remodeling in the case of mesenchymal spheroids and different modes of cell migration. The obtained results will contribute to the development of more realistic models for spheroid fusion that would further provide a helpful tool for constructing cell aggregates with required properties both for fundamental studies and tissue reparation.

Fibrin is one of the promising biomaterials in tissue engineering for creating favorable conditions for the formation of a capillary-like vascular network. The use of native fibrin is limited due to its rapid degradation and opacity. To improve its properties, including biological ones, various modifications have been proposed, for example, using functionalized polyethylene glycol (PEG). In this work, homobifunctional (O,O''-bis[2-(N-succinimidyl-succinylamino)ethyl])polyethylene glycol of various molecular weights was used to modify fibrin. The modification of fibrin with vascular endothelial growth factor was also analyzed for possible stimulation of the formation of tubule-like structures. Small-angle X-ray scattering (SAXS) data and ab initio modeling of the three-dimensional particle shape showed that PEG–fibrin conjugates consist of filamentous particles, depending on the size of the PEG molecule, the molar ratio of fibrin to PEG, and the presence or absence of vascular endothelial growth factor.

One of the promising approaches to the treatment of injured tissue is the application of bioengineering techniques based on the introduction of cells into the damage area. An application of cells alone does not provide a complete replacement of the tissue defect. Therefore, scaffolds are used allowing organization of the cells into a structure, which is capable of the total reproduction of the damaged tissue integrity. Great number of factors, which influence the cell behavior and tissue formation at the injury site when using scaffolds are known. Here, we analyzed the effect of structural heterogeneity of scaffolds on cellular behavior and metabolism. All scaffolds were obtained by two-photon polymerization technic. It was found that colonization of heterogeneous scaffolds was insignificant less than homogeneous ones. However, there were not dead cells on heterogeneous matrix. We found that the level of free and bound NAD(P)H for the cells on the heterogeneous and homogeneous scaffolds was differ. This can indicate a different contribution of glycolysis and oxidative phosphorylation intensity in stem cells seeded on two types of scaffolds.

Lactoferrin (Lf) possesses various biological properties and therapeutic potentials being a perspective anti-inflammatory, antibacterial, antiviral, antioxidant, antitumor, and immunomodulatory agent. A significant body of literature has also demonstrated that Lf modulates regenerative processes in different anatomical structures, such as bone, cartilage, skin, mucosa, cornea, tendon, vasculature, and adipose tissue. Hence, this review collected and analyzed the data on the regenerative effects of Lf, as well as paid specific attention to their molecular basis. Furthermore, tissue and condition-specific activities of different Lf types as well as problems of their delivery to the targeted organs were discussed. The authors strongly hope that this review will stimulate researchers to focus on the highlighted topics thus accelerating the progress of Lf's wider clinical application.

A two-stage polylactide modification was performed in the supercritical carbon dioxide medium using the urethane formation reaction. The modification resulted in the synthesis of polymerizable methacrylate derivatives of polylactide for application in the spatial 3D structuring by laser stereolithography. The use of the supercritical carbon dioxide medium allowed us to obtain for the first time polymerizable oligomer-polymer systems in the form of dry powders convenient for further application in the preparation of polymer compositions for photocuring. The photocuring of the modified polymers was performed by laser stereolithography and two-photon crosslinking. Using nanoindentation, we found that Young&rsquo, s modulus of the cured compositions corresponded to the standard characteristics of implants applied in regenerative medicine. As shown by thermogravimetric analysis, the degree of crosslinking and, hence, the local stiffness of scaffolds were determined by the amount of the crosslinking agent and the photocuring regime. No cytotoxicity was observed for the structures.

Great number of factors, which influence the cell behavior and tissue formation at the injury site when using scaffolds are known. Here, we analyzed the effect of structural heterogeneity of scaffolds on cellular behavior. All scaffolds were obtained by two-photon polymerization technic. We found that the MSC behavior and metabolism have a great differences between the heterogeneous and standard tissue constructs. The main differences relate to cell migration, proliferation, and metabolic pathways. The heterogeneous scaffolds can significantly expand the fundamental knowledge of cellular behavior and the formation of various types of tissues in vitro and in vivo.

In this paper, terahertz (THz) pulsed spectroscopy and solid immersion microscopy were applied to study interactions between water vapor and tissue scaffolds–the decellularized bovine pericardium (DBP) collagen matrices, in intact form, cross-linked with the glutaraldehyde or treated by plasma. The water-absorbing properties of biomaterials are prognostic for future cell-mediated reactions of the recipient tissue with the scaffold. Complex dielectric permittivity of DBPs was measured in the 0.4–2.0 THz frequency range, while the samples were first dehydrated and then exposed to water vapor atmosphere with 80.0 ± 5.0% relative humidity. These THz dielectric measurements of DBPs and the results of their weighting allowed to estimate the adsorption time constants, an increase of tissue mass, as well as dispersion of these parameters. During the adsorption process, changes in the DBPs’ dielectric permittivity feature an exponential character, with the typical time constant of =8–10 min, the transient process saturation at =30 min, and the tissue mass improvement by =1–3%. No statistically-relevant differences between the measured properties of the intact and treated DBPs were observed. Then, contact angles of wettability were measured for the considered DBPs using a recumbent drop method, while the observed results showed that treatments of DBP somewhat affects their surface energies, polarity, and hydrophilicity. Thus, our studies revealed that glutaraldehyde and plasma treatment overall impact the DBP–water interactions, but the resultant effects appear to be quite complex and comparable to the natural variability of the tissue properties. Such a variability was attributed to the natural heterogeneity of tissues, which was confirmed by the THz microscopy data. Our findings are important for further optimization of the scaffolds’ preparation and treatment technologies. They pave the way for THz technology use as a non-invasive diagnosis tool in tissue engineering and regenerative medicine.

We examined the accumulation of phenylethanol, geraniol, citronellol, and nerol by Eremothecium ashbyi Guillermond 1935 strains characterized by different levels of riboflavin synthesis. There was a significant positive correlation between riboflavin and monoterpene alcohol biosyntheses (Spearman’s correlation coefficients = 0.81–1.00, p ≤ 0.05). Strain accumulation of the main secondary metabolites such as vitamin B2 and aroma forming compounds was found to be accompanied with an increase in the lipid droplet quantities and the vacuole filling with lipophilic compounds. These phenomena may be used as an indirect measure of riboflavinogenesis intensity and essential oil synthesis.

Emerging global danger of multidrug resistant microbes makes it essential to explore new approaches to treat infections. We studied antibacterial and pro-regenerative effects of photodynamic therapy (PDT) performed with water solutions of photodithazine and its complexes with Pluronic F127 and chitosan in rat model of full thickness wound (n = 24) infected by an associated Gram-negative and Gram-positive bacteria culture. Laboratory rats were exposed to PDT 24 and 72 h after the injury. Exudate samples were collected before and after PDT for a microbiological study. Autopsy tissues were excised and fixed in formalin on day 4 of the experiment. Fixed tissues were processed and poured into paraffin. Paraffin sections were stained with hematoxylin and eosin and studied by an experienced pathologist. Microbiological analysis revealed that the photoactivation of photodithazine and its complexes suppressed the associated microflora in vivo and inhibited suppurative inflammation in the wounds. The triple Photodithazine-Pluronic F127-Chitosan system possessed the highest antibacterial activity. The morphological study revealed that PDT with photodithazine polymer complexes accelerated wound healing, promoted restoration of microcirculation, facilitated proliferation of fibroblast and vessels and stimulated collagen synthesis. The Photodithazine-Pluronic F127-Chitosan complex may be successfully applied for PDT to prevent and treat suppurative inflammatory diseases of the skin and soft tissues.

RSC Advances 10(8), 4190 - 4200 (2020). doi:10.1039/C9RA08169K, Fibrin is a well-known tool in tissue engineering, but the structure of its modifications created to improve its properties remains undiscussed despite its importance, e.g. in designing biomaterials that ensure cell migration and lumenogenesis. We sought to uncover the structural aspects of PEGylated fibrin hydrogels shown to contribute to angiogenesis. The analysis of the small-angle X-ray scattering (SAXS) data and ab initio modeling revealed that the PEGylation of fibrinogen led to the formation of oligomeric species, which are larger at a higher PEG : fibrinogen molar ratio. The improvement of optical properties was provided by the decrease in aggregates' sizes and also by retaining the bound water. Compared to the native fibrin, the structure of the 5 : 1 PEGylated fibrin gel consisted of homogenously distributed flexible fibrils with a smaller space between them. Moreover, as arginylglycylaspartic acid (RGD) sites may be partly bound to PEG-NHS or masked because of the oligomerization, the number of adhesion sites may be slightly reduced that may provide the better cell migration and formation of continuous capillary-like structures., Published by RSC Publishing, London

In this work, we have explored 3-D co-culture of vasculogenic cells within a synthetically modified fibrin hydrogel. Fibrinogen was covalently linked with PEG-NHS in order to improve its degradability resistance and physico-optical properties. We have studied influences of the degree of protein PEGylation and the concentration of enzyme thrombin used for the gel preparation on cellular responses. Scanning electron microscopy analysis of prepared gels revealed that the degree of PEGylation and the concentration of thrombin strongly influenced microstructural characteristics of the protein hydrogel. Human umbilical vein endothelial cells (HUVECs) and human adipose-derived stem cells (hASCs), used as vasculogenic co-culture, could grow in 5:1 PEGylated fibrin gels prepared using 1:0.2 protein to thrombin ratio. This gel formulation supported hASCs and HUVECs spreading and the formation of cell extensions and cell-to-cell contacts. Expression of specific ECM proteins and vasculogenic process inherent cellular enzymatic activity were investigated by immunofluorescent staining, gelatin zymography, western blot and RT-PCR analysis. After evaluation of the optimal gel composition and PEGylation ratio, the hydrogel was utilized for investigation of vascular tube formation within a perfusable microfluidic system. The morphological development of this co-culture within a perfused hydrogel over 12 days led to the formation of interconnected HUVEC-hASC network. The demonstrated PEGylated fibrin microfluidic approach can be used for incorporating other cell types, thus representing a unique experimental platform for basic vascular tissue engineering and drug screening applications.

Significance: Currently, various scaffolds with immobilized cells are widely used in tissue engineering and regenerative medicine. However, the physiological activity and cell viability in such constructs might be impaired due to a lack of oxygen and nutrients. Photobiomodulation (PBM) is a promising method of preconditioning cells to increase their metabolic activity and to activate proliferation or differentiation. Aim: Investigation of the potential of PBM for stimulation of cell activities in hydrogels. Approach: Mesenchymal stromal cells (MSCs) isolated from human gingival mucosa were encapsulated in modified fibrin hydrogels with different thicknesses and concentrations. Constructs with cells were subjected to a single-time exposure to red (630 nm) and near-infrared (IR) (840 nm) low-intensity irradiation. After 3 days of cultivation, the viability and physiological activity of the cells were analyzed using confocal microscopy and a set of classical tests for cytotoxicity. Results: The cell viability in fibrin hydrogels depended both on the thickness of the hydrogels and the concentration of gel-forming proteins. The PBM was able to improve cell viability in hydrogels. The most pronounced effect was achieved with near-IR irradiation at the 840-nm wavelength. Conclusions: PBM using near-IR light can be applied for stimulation of MSCs metabolism and proliferation in hydrogel-based constructs with thicknesses up to 3 mm.

Photobiomodulation (PBM) using nonionizing light sources, including lasers, light-emitting diodes, and/or broadband light, in the visible (400 to 700 nm) and near-infrared (700 to 1100 nm) electromagnetic spectrum, has been successfully exploited for multiple therapeutic purposes. We analyzed the effects of red and infrared irradiation on neuroblastoma cells in an in vitro rotenone model of Parkinson’s disease. Cell viability was assessed by colorimetric assay for metabolic activity (MTT test), and the oxygen consumption rate was analyzed using a Seahorse analyzer. Low doses of rotenone slightly, but not significantly, suppressed oxygen consumption and did not affect cell viability within 2 hours of treatment. PBM stimulated mitochondrial respiration overcoming rotenone-induced inhibition. At high doses (50 μM), rotenone moderately suppressed cell viability, which was reversed by PBM. Thus, preliminary treatment with red and infrared radiation improves cell viability and enhances mitochondrial oxygen consumption in an in vitro rotenone model of Parkinson’s disease.

Maintaining the epithelial status of cells in vitro and fabrication of a multilayered epithelial lining is one of the key problems in the therapy using cell technologies. When cultured in a monolayer, epithelial cells change their phenotype from epithelial to epithelial-mesenchymal or mesenchymal that makes it difficult to obtain a sufficient number of cells in a 2D culture and to use them in tissue engineering. Here, using buccal epithelial cells from the oral mucosa, we developed a novel approach to recover and maintain the stable cell phenotype and form a multilayered epithelial lining in vitro via the 2D/3D cell self-assembling. Transitioning the cells from the monolayer to non-adhesive 3D culture conditions led to formation of self-assembling spheroids, with restoration of their epithelial characteristics after epithelial-mesenchymal transition. In 7 days, the cells within spheroids restored the apical-basal polarity, and the formation of both tight (ZO1) and adherent (E-cadherin) intercellular junctions was shown. Thus, culturing buccal epithelial cells in a 3D system allowed us to recover and durably maintain the morphological and functional characteristics of epithelial cells. The multilayered epithelial lining formation was achieved after placing spheroids for 7 days onto a hybrid matrix, which consisted of collagen layers and reinforcing poly (lactide-co-glycolide) fibers and was proven promising for replacement of the urothelium. Thus, we offer an effective technique of forming multilayered epithelial linings on carrier-matrices using cell spheroids that was not previously described elsewhere and can find a wide range of applications in tissue engineering, replacement surgery, and regenerative medicine.

One of the essential goals in regenerative medicine is microvascularization which enables an effective blood supply within de novo constructed tissues and organs. In our study, we used two common multipotent mesenchymal stromal cell (MMSC) sources (subcutaneous adipose tissue and Wharton's jelly of the umbilical cord) where is a subpopulation of endothelial precursors. In the medium supplemented with VEGF, the 3D cultures of UC MMSCs and ADSCs promoted the endothelial cell differentiation. To evaluate their ability to form a capillary-like network, we encapsulated spheroids within non-modified and PEGylated fibrin hydrogels. The PEGylated hydrogel supported better the formation of multibranched cords than the pure fibrin gel. Analysis of tubule growth rate, length, and branching showed that the differentiated ADSCs had higher angiogenic potential than the differentiated hUC MMSCs. Our study can be a basis for the development of new strategies in tissue engineering and treatment of vascular diseases.

In the presented study, we have developed a synthetic strategy allowing a gradual variation of a polylactide arms' length, which later influences the micromorphology of the scaffold surface, formed by a two-photon polymerization technique. It has been demonstrated that the highest number of cells is present on the scaffolds with the roughest surface made of the polylactide with longer arms (PLA760), and osteogenic differentiation of mesenchymal stem cells is most pronounced on such scaffolds. According to the results of biological testing, the PLA760 scaffolds were implanted into a created cranial defect in a mouse for an in vivo assessment of the bone tissue formation. The in vivo experiments have shown that, by week 10, deposition of calcium phosphate particles occurs in the scaffold at the defect site, as well as, the formation of a new bone and ingrowth of blood vessels from the surrounding tissues. These results demonstrate that the cross-linked microstructured tetrafunctional polylactide scaffolds are promising microstructures for bone regeneration in tissue engineering.

Polymeric, ceramic and hybrid material-based three-dimensional (3D) scaffold or matrix structures are important for successful tissue engineering. While the number of approaches utilizing the use of cell-based scaffold and matrix structures is constantly growing, it is essential to provide a framework of their typical preparation and evaluation for tissue engineering. This chapter describes the fabrication of 3D scaffolds using two-photon polymerization, decellularization and cell encapsulation methods and easy-to-use protocols allowing assessing the cell morphology, cytotoxicity and viability in these scaffolds.

Developing bone scaffolds can greatly improve the patient&rsquo, s quality of life by accelerating the rehabilitation process. In this paper, we studied the process of composite polycaprolactone supercritical foaming for tissue engineering. The influence of graphene oxide and reduced graphene oxide on the foaming parameters was studied. The structural and mechanical properties were studied. The scaffolds demonstrated mechanical flexibility and endurance. The co-culturing and live/dead tests demonstrated that the obtained scaffolds are biocompatible. Different composite scaffolds induced various surface cell behaviors. The experimental data demonstrate that composite foams are promising candidates for in vivo medical trials.