Optimization of 3D printing and in vitro characterization of alginate/gelatin lattice and angular scaffolds for potential cardiac tissue engineering.

Background: Engineering cardiac tissue that mimics the hierarchical structure of cardiac tissue remains challenging, raising the need for developing novel methods capable of creating structures with high complexity. Three-dimensional (3D)-printing techniques are among promising methods for engineering complex tissue constructs with high precision. By means of 3D printing, this study aims to develop cardiac constructs with a novel angular structure mimicking cardiac architecture from alginate (Alg) and gelatin (Gel) composite. The 3D-printing conditions were optimized and the structures were characterized in vitro, with human umbilical vein endothelial cells (HUVECs) and cardiomyocytes (H9c2 cells), for potential cardiac tissue engineering. Methods: We synthesized the composites of Alg and Gel with varying concentrations and examined their cytotoxicity with both H9c2 cells and HUVECs, as well as their printability for creating 3D structures of varying fibre orientations (angular design). The 3D-printed structures were characterized in terms of morphology by both scanning electron microscopy (SEM) and synchrotron radiation propagation-based imaging computed tomography (SR-PBI-CT), and elastic modulus, swelling percentage, and mass loss percentage as well. The cell viability studies were conducted via measuring the metabolic activity of the live cells with MTT assay and visualizing the cells with live/dead assay kit. Results: Among the examined composite groups of Alg and Gel, two combinations with ratios of 2 to 1 and 3 to 1 (termed as Alg2Gel1 and Alg3Gel1) showed the highest cell survival; they accordingly were used to fabricate two different structures: a novel angular and a conventional lattice structure. Scaffolds made of Alg3Gel1 showed higher elastic modulus, lower swelling percentage, less mass loss, and higher cell survival compared to that of Alg2Gel1. Although the viability of H9c2 cells and HUVECs on all scaffolds composed of Alg3Gel1 was above 99%, the group of the constructs with the angular design maintained significantly more viable cells compared to other investigated groups. Conclusion: The group of angular 3D-ptinted constructs has illustrated promising properties for cardiac tissue engineering by providing high cell viability for both endothelial and cardiac cells, high mechanical strength as well as appropriate swelling, and degradation properties during 21 days of incubation. Statement of Significance: 3D-printing is an emerging method to create complex constructs with high precision in a large scale. In this study, we have demonstrated that 3D-printing can be used to create compatible constructs from the composite of Alg and Gel with endothelial cells and cardiac cells. Also, we have demonstrated that these constructs are able to enhance the viability of cardiac and endothelial cells via creating a 3D structure mimicking the alignment and orientation of the fibers in the native heart.

When the clock ticks wrong with COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a member of the coronavirus family that causes the novel coronavirus disease first diagnosed in 2019 (COVID-19). Although many studies have been carried out in recent months to determine why the disease clinical presentations and outcomes can vary significantly from asymptomatic to severe or lethal, the underlying mechanisms are not fully understood. It is likely that unique individual characteristics can strongly influence the broad disease variability; thus, tailored diagnostic and therapeutic approaches are needed to improve clinical outcomes. The circadian clock is a critical regulatory mechanism orchestrating major physiological and pathological processes. It is generally accepted that more than half of the cell-specific genes in any given organ are under circadian control. Although it is known that a specific role of the circadian clock is to coordinate the immune system's steady-state function and response to infectious threats, the links between the circadian clock and SARS-CoV-2 infection are only now emerging. How inter-individual variability of the circadian profile and its dysregulation may play a role in the differences noted in the COVID-19-related disease presentations, and outcome remains largely underinvestigated. This review summarizes the current evidence on the potential links between circadian clock dysregulation and SARS-CoV-2 infection susceptibility, disease presentation and progression, and clinical outcomes. Further research in this area may contribute towards novel circadian-centred prognostic, diagnostic and therapeutic approaches for COVID-19 in the era of precision health.

Biomineralization of three calcium silicate-based cements after implantation in rat subcutaneous tissue.

OBJECTIVES: The aim of this study was to evaluate the dystrophic mineralization deposits from 3 calcium silicate-based cements (Micro-Mega mineral trioxide aggregate [MM-MTA], Biodentine [BD], and EndoSequence Root Repair Material [ESRRM] putty) over time after subcutaneous implantation into rats. MATERIALS AND METHODS: Forty-five silicon tubes containing the tested materials and 15 empty tubes (serving as a control group) were subcutaneously implanted into the backs of 15 Wistar rats. At 1, 4, and 8 weeks after implantation, the animals were euthanized (n = 5 animals/group), and the silicon tubes were removed with the surrounding tissues. Histopathological tissue sections were stained with von Kossa stain to assess mineralization. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) were also used to assess the chemical components of the surface precipitates deposited on the implant and the pattern of calcium and phosphorus distribution at the material-tissue interface. The calcium-to-phosphorus ratios were compared using the non-parametric Kruskal-Wallis test at a significance level of 5%. RESULTS: The von Kossa staining showed that both BD and ESRRM putty induced mineralization starting at week 1; this mineralization increased further until the end of the study. In contrast, MM-MTA induced dystrophic calcification later, from 4 weeks onward. SEM/EDX showed no statistically significant differences in the calcium- and phosphorus-rich areas among the 3 materials at any time point (p > 0.05). CONCLUSIONS: After subcutaneous implantation, biomineralization of the 3-calcium silicate-based cements started early and increased over time, and all 3 tested cements generated calcium- and phosphorus-containing surface precipitates.

Controlled Drug Delivery Systems for Oral Cancer Treatment-Current Status and Future Perspectives.

Oral squamous cell carcinoma (OSCC), which encompasses the oral cavity-derived malignancies, is a devastating disease causing substantial morbidity and mortality in both men and women. It is the most common subtype of the head and neck squamous cell carcinoma (HNSCC), which is ranked the sixth most common malignancy worldwide. Despite promising advancements in the conventional therapeutic approaches currently available for patients with oral cancer, many drawbacks are still to be addressed; surgical resection leads to permanent disfigurement, altered sense of self and debilitating physiological consequences, while chemo- and radio-therapies result in significant toxicities, all affecting patient wellbeing and quality of life. Thus, the development of novel therapeutic approaches or modifications of current strategies is paramount to improve individual health outcomes and survival, while early tumour detection remains a priority and significant challenge. In recent years, drug delivery systems and chronotherapy have been developed as alternative methods aiming to enhance the benefits of the current anticancer therapies, while minimizing their undesirable toxic effects on the healthy non-cancerous cells. Targeted drug delivery systems have the potential to increase drug bioavailability and bio-distribution at the site of the primary tumour. This review confers current knowledge on the diverse drug delivery methods, potential carriers (e.g., polymeric, inorganic, and combinational nanoparticles; nanolipids; hydrogels; exosomes) and anticancer targeted approaches for oral squamous cell carcinoma treatment, with an emphasis on their clinical relevance in the era of precision medicine, circadian chronobiology and patient-centred health care.

Injectable conductive collagen/alginate/polypyrrole hydrogels as a biocompatible system for biomedical applications.

Recently, Injectable Conducting Hydrogel (ICH) systems have gained much attention for tissue engineering and regenerative medicine. These systems can promote the regeneration of tissues responding to electrical responses. In this study, a novel ICH system was introduced. To achieve this system, firstly, a soluble non-toxic polypyrrole (PPy) synthesized by grafting pyrrole on alginate (Alg) backbone (Alg-graft-PPy), and then, ICH systems were prepared by the given ratios of Alg-graft-PPy, Alg, and collagen (Col). Three different amounts of Col (0.5, 1, and 1.5 mg/ml) were added to the system including Alg-graft-PPy: Alg wt. % with the ratios of 20:80 and 30:70. FTIR spectroscopy, electrical conductivity, viscosity, syringeability, gelation time, and MTT assay were performed in order to characterize the produced hydrogels. Due to the rheological behavior of 20:80 (Alg-graft-PPy: Alg wt. %), it was recognized more suitable to inject. Also this system associated with 0.5 mg/ml Col introduced as the best sample with respect to its viscosity and injectability. This ICH system has shown high conductivity in addition to a good level of cell viability and syringeability. With respect to properties of the produced ICH system, it can be applied for bone, nerve, muscle and cardiac cells, which respond to electrical impulses.