The skin is the layer of flexible outer tissue covering the body and functions as an interface with the environment.^1,2 The main function of the skin is the protection from external factors, for example, against various xenobiotics and pathogens. Water and temperature balances are also regulated based on the processes in the skin. The functions and dysfunctions of the skin, including many pathological conditions, have a significant impact on both the physical health and general wellness of a person.

For the past 10 years, the main efforts of most bioprinting research teams have focused on creating new bioink formulations, rather than inventing new printing set-up concepts. New tissue-specific bioinks with good printability, shape fidelity, and biocompatibility are based on “old” (well-known) biomaterials, particularly fibrin. While the interest in fibrin-based bioinks is constantly growing, it is essential to provide a framework of material’s properties and trends. This review aims to describe the fibrin properties and application in three-dimensional bioprinting and provide a view on further development of fibrin-based bioinks.

Biodegradable polymeric fibrous non-woven materials are widely used type of scaffolds for tissue engineering. Their morphology and properties could be controlled by composition and fabrication technology. This work is aimed at development of fibrous scaffolds from a multicomponent polymeric system containing biodegradable synthetic (polylactide, polycaprolactone) and natural (gelatin, chitosan) components using different methods of non-woven mats fabrication: electrospinning and electro-assisted solution blow spinning. The effect of the fabrication technique of the fibrous materials onto their morphology and properties, including the ability to support adhesion and growth of cells, was evaluated. The mats fabricated using electrospinning technology consist of randomly oriented monofilament fibers, while application of solution blow spinning gave a rise to chaotically arranged multifilament fibers. Cytocompatibility of all fabricated fibrous mats was confirmed using in vitro analysis of metabolic activity, proliferative capacity and morphology of NIH 3T3 cell line. Live/Dead assay revealed the formation of the highest number of cell–cell contacts in the case of multifilament sample formed by electro-assisted solution blow spinning technology.

Photobiomodulation (PBM) is a nonthermal process that utilizes nonionizing forms of light sources, including lasers, LEDs, and broadband light in the visible (400 to 750 nm) and infrared range (750 to 1100 nm).^1,2 The process of PBM of biological objects is usually referred to as an irradiation.^{3 – 5} Historically, the PBM application in clinics began earlier than any clinical trials, in vivo or in vitro tests on this method. The PBM effects themselves were first discovered in 1967 by Endre Mester while he was trying to treat an advanced melanoma in one of his patients.⁶ Intrigued by the results of laser irradiation being opposite to those expected, Mester continued his experiments on mice—and his works are the first known confirmation of the PBM effects.⁷ Nowadays, PBM is widely utilized for various clinical and therapeutic applications. PBM in the red and NIR ranges have proven itself to be beneficial for the repair of cartilage and bone defects,^8,9 a wide range of neuronal disorders,¹⁰ and is also capable of resolving pain, decreasing inflammation, and accelerating healing.^{11 – 13} Currently, there are more than 600 registered clinical trials related to PBM, and more than half of them have been successfully completed. The trials based on the PBM include various conditions, such as postoperative wounds, chronic pain, skin diseases, and more (details are provided in Table 1). Based on this clinical research, PBM devices using both lasers and LEDs have been cleared for marketing by FDA.^{14 – 16}

An elevated concentration of fibrinogen in blood is a significant risk factor during many pathological diseases, as it leads to an increase in red blood cells (RBC) aggregation, resulting in hemorheological disorders. Despite the biomedical importance, the mechanisms of fibrinogen-induced RBC aggregation are still debatable. One of the discussed models is the non-specific adsorption of fibrinogen macromolecules onto the RBC membrane, leading to the cells bridging in aggregates. However, recent works point to the specific character of the interaction between fibrinogen and the RBC membrane. Fibrinogen is the major physiological ligand of glycoproteins receptors IIbIIIa (GPIIbIIIa or αIIββ3 or CD41/CD61). Inhibitors of GPIIbIIIa are widely used in clinics for the treatment of various cardiovascular diseases as antiplatelets agents preventing the platelets’ aggregation. However, the effects of GPIIbIIIa inhibition on RBC aggregation are not sufficiently well studied. The objective of the present work was the complex multimodal in vitro study of the interaction between fibrinogen and the RBC membrane, revealing the role of GPIIbIIIa in the specificity of binding of fibrinogen by the RBC membrane and its involvement in the cells’ aggregation process. We demonstrate that GPIIbIIIa inhibition leads to a significant decrease in the adsorption of fibrinogen macromolecules onto the membrane, resulting in the reduction of RBC aggregation. We show that the mechanisms underlying these effects are governed by a decrease in the bridging components of RBC aggregation forces.