Annotation of the results obtained in 2020
Continuing the work of the previous stage, we investigated the biocompatibility of polymer-protein scaffolds in vitro. For this, their ability to maintain the proliferation of fibroblasts of the 3T3 line was investigated. It turned out that cells grow on control scaffolds from PLA no worse than on protein-containing scaffolds (two-component PLA-BSA or PLA-fibrinogen). How does the presence of protein in an electrospun scaffold affect its properties? To answer this question, we investigated scaffolds made of PLA-BSA blends and the control scaffolds made of pure PLA. We varied not only the composition of the scaffolds, but also the conditions for their preparation, for example, the conditions for mixing the polymer-protein-solvent blend, which was loaded into the syringe for electrospinning. At the previous stage, we focused on measurements of the scaffold structure; however, at this stage – we focused on mechanical properties, degradation kinetics, and surface wettability. An increase in the percentage of BSA in the scaffold composition was accompanied by a significant decrease in ultimate elongation at break and strength, as well as a decrease in Young's modulus. This is an intuitively expected result because BSA is a globular protein, and BSA scaffolds a priori have lower mechanical characteristics than PLA scaffolds. We found an unexpectedly weak effect of phase separation in a ternary blend subjected to electrospinning on the properties of scaffolds made from this blend. It could be expected that a scaffold prepared from a heterogeneous blend would be heterogeneous, and structural inhomogeneities would deteriorate the mechanical properties. However, this effect was not observed experimentally. It turned out that the homogeneity of the scaffold has little effect on its mechanics, and structural defects (droplets and thickening of fibers), which appear at non-optimal electrospinning parameters, are far more significant. Similarly, the heterogeneity of the polymer-protein-solvent blend used to make the scaffold appears to have little effect on wettability. The contact angle changed with variation in the diameters of the scaffold fibers; however, the change was low with the variation composition. To interpret the data on wettability, a theoretical model was proposed for calculating the contact angles of nonwoven materials, including electrospun ones. The difference between our model and the others is that our model regards not only the fibers and the air between them but also a smooth substrate parallel to the fibers. This allows the model to be used to assess the wettability not only of electrospun scaffolds but also of individual fibers deposited onto the collector. One of the features of polylactide and many other polyesters is slow degradation (approximately six months for amorphous PLA and up to two years for semi-crystalline PLA), and it can be accelerated by introducing a water-soluble component (protein) into the scaffold. Using PLA-BSA scaffolds, we have shown that the introduction of a water-soluble protein into the scaffold accelerates its degradation in an aqueous solution by two mechanisms. First, the protein is released into the solution, and the mass of the scaffold decreases. Secondly, when washed out, the protein leaves pores that make the insoluble part of the scaffold more accessible to water - and thereby, it contributes to more rapid hydrolytic degradation of the scaffold. These features can be used to fabricate scaffolds with controlled degradation kinetics.

 

Publications

---

Annotation of the results obtained in 2019
In everyday life we use many products made of non-woven materials; they consist of randomly entangled threads and fibers. Non-wovens are used as diapers and napkins, pieces of clothing and shoes, bags, fillers for blankets and pillows, filters, and much more. Electrospinning is an outstanding method for the production of non-woven materials since it allows us to a mat consisting of fibers with a diameter of ~100 nm. This is 10-100 times less than the diameter of a fiber of a non-woven material made by the traditional methods. For comparison, the typical size of a bacteria is ~ 1000 nm. It turned out that non-woven mats formed by electrospinning look similar to the extracellular matrix. Thus, electrospinning is used to manufacture wound dressings, artificial skin, cell culture substrates, and other biomedical products. To render electrospun mats bioactive, we can add growth factors or other proteins to their composition. However, little is known about the influence of proteins on the structure and properties of electrospun mats. How does protein incorporation influence on the mat morphology? On mechanical properties? Solubility and the biological properties? In this project, we are trying to answer these questions; our experimental system consists of polylactide, a biocompatible absorbable polymer, and blood proteins - albumin and fibrinogen. We have chosen the conditions for the preparation of electroformed protein-containing films and studied their structure using high-resolution microscopy. It was found that, despite the low thermodynamic compatibility of polylactide with the proteins, individual electrospun fibers manufactured from the immiscible polyester-protein blends contain both components. We have carried out experiments on the biocompatibility of the electrospun protein-containing films.

 

Publications

---