**4. Conclusions**

The structure and physicochemical characteristics of the ES matrices obtained from the solutions of PCL with SRL in HFIP and their blends with HSA, DMSO, and TEA were studied. The matrix produced from 5% PCL/SRL/10% HSA/3% DMSO was shown to be the most suitable for bare-metal stent coating because it is su fficiently strong, exhibited long-term SRL release kinetics, and is thus expected to maintain a concentrations of SRL in the vascular wall that are suitable for antiproliferative activity over a long period. The use of BP increased SRL release. We showed that all matrices can release SRL without fiber degradation. The twofold elongation of the matrices barely changed the SRL release kinetics. Therefore, PCL-based matrices containing HSA, SRL, and DMSO are a promising material for vascular stent coating with prolonged delivery of SRL.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1996-1944/13/12/2692/s1, Table S1: Release curves comparison using Fit factors f1 and f2; Table S2: Release curves comparison using Fit factors f1 and f2. Comparison of kinetic curves of SRL release from the parent and the two-fold expanded matrices. Incubation of the matrices in BP with medium replacement.

**Author Contributions:** Z.K.N., investigation, matrix characterization and SRL release study, and writing—original draft; B.P.C., investigation, matrix production, and SEM study; V.S.C., investigation and contact angle measurements; I.V.R., investigation and SRL labeling; A.A.K., methodology and resources; P.P.L., supervision, project administration, methodology, funding acquisition, and writing—review & editing. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Russian Scientific Foundation, gran<sup>t</sup> number 18-15-00080, and partially supported by the Russian State funded budget project of ICBFM SB RAS number AAAA-A17-117020210026-2 (support of SEM and H3-labeling).

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
