Design and Characterization of Aromatic Copolyesters Containing Furan and Isophthalic Rings with Suitable Properties for Vascular Tissue Engineering

Abstract

Cardiovascular diseases are responsible for a large number of severe disability cases and deaths worldwide. Strong research in this field has been extensively carried out, in particular for the associated complications, such as the occlusion of small-diameter (<6 mm) vessels. Accordingly, in the present research, two random copolyesters of poly(butylene 2,5-furandicarboxylate) (PBF) and poly(butylene isophthalate) (PBI), were successfully synthesized via two-step melt polycondensation and were thoroughly characterized from molecular, thermal, and mechanical perspectives. The copolymeric films displayed a peculiar thermal behavior, being easily processable in the form of films, although amorphous, with T_g close to room temperature. Their thermal stability was high in all cases, and from the mechanical point of view, the materials exhibited a high ultimate strength, together with values of elastic moduli tunable with the chemical composition. The long-term stability of these materials under physiological conditions was also demonstrated. Cytotoxicity was assessed using a direct contact assay with human umbilical vein endothelial cells (HUVECs). In addition, hemocompatibility was tested by evaluating the adhesion of blood components (such as the adsorption of human platelets and fibrinogen). As a result, a proper chemical design and, in turn, both the solid-state and functional properties, are pivotal in regulating cell behavior and opening new frontiers in the tissue engineering of soft tissues, including vascular tissues.

Keywords: aromatic copolyesters; biocompatibility; hemocompatibility; hydrolytic stability; poly(butylene 2,5-furanoate); poly(butylene isophthalate).

Figure 1

¹H-NMR spectrum of P(BF₁₀BI₉₀) with peaks’ assignment.

Figure 2

First (A) and second (B) DSC scans of purified powders, and (C) first DSC scan of films of PBF, PBI, and P(BF_xBI_y) copolymers. TGA (D) and WAXS (E) traces of PBF, PBI, and P(BF_xBI_y) copolymers, purified powders.

Figure 3

Stress–strain curves (A) and enlargement of the low-stress region (B) of PBF, PBI, and P(BF_xBI_y) copolymeric films.

Figure 4

Analysis of surface properties. (A) Z-potential measurement at pH 7.4. Data are shown as the mean values of the replicates (n = 3) ± the standard deviation (SD), represented by the error bars. One-way analysis of variance (ANOVA), followed by Bonferroni’s test between samples, showed significant difference: p value < 0.05 (*); p < 0.01 (**); p < 0.001 (***) and p < 0.0001 (****). (B) Haralick’s texture features. Estimated marginal means of PBF, PBI, and P(BF_xBI_y) copolymers samples with error bars indicating standard deviation. All comparisons are significant (p < 0.05).

Figure 5

Cell viability of PBF, PBI, and P(BF_xBI_y) copolymers, with respect to the control, after 1, 3, and 7 days of incubation. The data are presented as mean value ± SD.

Figure 6

Adhesion of platelets (PLT) on PBF, P(BF_xBI_y) copolymers, and PBI. PLT was obtained from Human platelet-rich plasma (hPRP) and incubated for 1 h at 37 °C + 5% CO₂ on samples and in a tissue culture plate (TCP) well used as a control. (A) Adhesion has been determined through the LDH assay. Data were represented as the number of adherent platelets per cm2 of surface. Data are shown as the mean values of the replicates (n = 3) ± standard deviation (SD), represented by the error bars. Statistically significant differences of samples vs. TCP were reported: p < 0.0001 (****). One-way analysis of variance (ANOVA), followed by Bonferroni’s test between samples, showed no significant differences between surfaces (p > 0.05). (B) Representative SEM images. Platelets that adhered to the surfaces were fixed and dehydrated to acquire SEM images at 3k× (scale bar 10 µm) magnification and insets at 10k× (scale bar 2 µm). TCP_Ctrl SEM images were in Supplementary Figure S5.

Figure 7

Human plasma total protein and fibrinogen absorption. Human plasma was immobilized on samples and on a tissue culture plate (TCP) control for 1 h at 37 °C. After the incubation time, the plasma proteins absorbed from the material’s surface were quantified (A) through the colorimetric BCA assay and expressed as µg proteins/cm². The quantity of human plasma fibrinogen absorbed from the surfaces (B) was detected through ELISA assay and expressed as µg/cm². Error bars indicate the standard deviation (SD) of the mean values of the replicates (n = 3). One-way analysis of variance (ANOVA) (*), followed by Bonferroni’s test between samples (p value < 0.05), was performed: p value < 0.05 (*); p < 0.01 (**); p < 0.001 (***) and p < 0.0001 (****). In (A) PBF vs. P(BF₉₀BI₁₀) samples: p value > 0.05; P(BF₉₀BI₁₀) vs. P(BF₁₀BI₉₀): p value > 0.05; PBI vs. P(BF_xBI_y): p value > 0.05. In (B) P(BF₉₀BI₁₀) vs. P(BF₁₀BI₉₀): p value > 0.05; PBI vs. P(BF_xBI_y): p value > 0.05.