Novel Bioactive Glass/Graphene Oxide-Coated Surgical Sutures for Soft Tissue Regeneration

Abstract

The combination of a commercially available PGLA (poly[glycolide-co-l-lactide]), 90:10% suture material with bioactive bioglass nanopowders (BGNs) and graphene oxide (GO)-doped BGNs offers new opportunities for the clinical application of biomaterials in soft tissue engineering. In the present experimental work, we demonstrate that GO-doped melt-derived BGNs were synthesized via the sol-gel process. After that, novel GO-doped and undoped BGNs were used to coat resorbable PGLA surgical sutures, thereby imparting bioactivity, biocompatibility, and accelerated wound healing properties to the sutures. Stable and homogeneous coatings on the surface of the sutures were achieved using an optimized vacuum sol deposition method. The phase composition, morphology, elemental characteristics, and chemical structure of uncoated and BGNs- and BGNs/GO-coated suture samples were characterized using Fourier transform infrared spectroscopy, field emission scanning electron microscopy, associated with elemental analysis, and knot performance test. In addition, in vitro bioactivity tests, biochemical tests, and in vivo tests were performed to examine the role of BGNs and GO on the biological and histopathological properties of the coated suture samples. The results indicated that the formation of BGNs and GO was enhanced significantly on the suture surface, which allowed for enhanced fibroblast attachment, migration, and proliferation and promoted the secretion of the angiogenic growth factor to speed up wound healing. These results confirmed the biocompatibility of BGNs- and BGNs/GO-coated suture samples and the positive effect of BGNs on the behavior of L929 fibroblast cells and also showed for the first time the possibility that cells can adhere and proliferate on the BGNs/GO-coated suture samples, especially in an in vivo environment. Resorbable surgical sutures with bioactive coatings, such as those prepared herein, can be an attractive biomaterial not only for hard tissue engineering but also for clinical applications in soft tissue engineering.

Figure 1

FTIR spectra for the surfaces of S group, S+BGNs group, and S+BGNs/GO group sutures.

Figure 2

FE-SEM images of the suture composite surfaces, depicting their morphology at different magnifications. The FE-SEM images provide information about the topography, texture, and composition of the surface. In this case, the FE-SEM images illustrate the structural features and surface characteristics of the suture composites, which are important for their mechanical performance and biological properties. The different magnifications used in the images enable a more comprehensive understanding of the surface morphology and the interactions between the different components of the composite.

Figure 3

EDX spectra obtained from the FE-SEM images of the surfaces of both as-received and coated suture samples. The spectra obtained from the as-received and coated suture samples provide information about the elements present on the surface and their distribution. The comparison of the spectra can help assess the success of the coating process and the changes in the elemental composition of the suture surface due to the coating.

Figure 4

(a) Schematic illustration of the L929 cell-based in vitro assay of suture composite samples in relation to cell viability. (b) In vitro cell viability and 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay. The observed cell morphology of L929 cells (mouse fibroblast cell line) after being treated for 24 h under a 100 Â inverted microscope. (c) Cell viability diagram (%) by the XTT assay for each group. Values represent the mean and ± SD of three independent experiments (p < 0.05; *Statistically significant differences between groups).

Figure 5

(a) Rat skin macroscopic photographs of the samples of each suture group obtained and the regions applied to the experimental animals during the surgical operation. The yellow circles that are pointed out in the images indicate the locations where the sutures were placed. (b) Appearance of the tissues with fragments taken for histopathological evaluation 7, 14, and 21 days after the surgical operation. In vivo suture samples interacting with the tissue appear to be completely surrounded by the tissue. (c) Photographs of histological analysis (H&E staining, 4× magnification) on H&E-stained cross sections of rat skin from both the epidermis and dermis layers to assess histological changes in rat skin following the surgical procedure.

Figure 6

Score classification of the histopathological lesions in the suture groups at each surgical removal time of rats (n = 5). Macroscopic evaluation was used to assess inflammation, capsule characterization, and polymorphonuclear leukocytes (PMNs) formation after laparotomy. The intensity of lesions was classified as absent reaction (0), mild reaction (1), moderate reaction (2), marked reaction (3), and severe reaction (4). All data are represented as the mean (standard deviation, ± SD) (p < 0.05; *Statistically significant differences between groups).

Figure 7

(a) Levels of the vascular endothelial growth factor (VEGF, ng/mL), interleukin-1β (IL-1β, ng/mL), and tumor necrosis factor-α (TNF-α, ng/mL) were determined from the intracardiac blood of rats on days 7, 14, and 21 after surgery. This was done to assess the changes in the levels of these biomarkers over time in each animal group. (b) VEGF levels in each animal group on days 7, 14, and 21 were compared to evaluate any differences in their expression. (c) Similarly, the levels of IL-1β between the groups on days 7, 14, and 21 were compared to assess any variations in their expression levels. (d) Lastly, the TNF-α levels between the groups on days 7, 14, and 21 were compared to determine any differences in their expression levels over time. All of the values are expressed as means (standard deviation, ± SD). Additionally, any statistically significant differences between groups were marked with an asterisk, and the significance level was set at p < 0.05.

Figure 8

Preparation of high-performance 45S5 bioglass nanoparticles (BGNs) and synthesis of graphene oxide (GO) nanosheets. (a) Schematic demonstrating the preparation of the melt-derived BGNs. The process involves the melting of the 45S5 bioglass material at high temperatures, followed by rapid quenching to produce a glassy matrix. This matrix is then ground into fine particles to produce the BGNs. (b) Chemical structure of BGNs: The BGNs are composed of various elements such as Si, Na, Ca, and P, which are essential for tissue repair. The top-view FE-SEM images of the BGNs show the morphology of the nanoparticles, with a uniform size distribution and an irregular shape. The EDX spectra of the BGNs confirm the presence of the related elements in the composition of the nanoparticles. (c) Experimental demonstration of the synthesis process of the GO by Hummer’s method. This method involves the oxidation of graphite using a mixture of concentrated H₂SO₄, K₂MnO₄, and NaNO₃. (d) Resulting GO material is composed of carbon, hydrogen, and oxygen, as demonstrated by the formation of its molecular structure. The FE-SEM image shows the morphology of the GO material, with a thin and flat structure that forms a nanosheet. The magnified TEM image provides a closer look at the nanosheet, revealing its layered nanostructure. The FTIR spectra of the GO material show the presence of various types of oxygen functional groups (C–OH, C–O–C, C=O, and O=C–OH), which are characteristic of GO.

Figure 9

Layout of the sol/gelation methodologies and vacuum sol deposition (VSD) process. (a) Surface-modified GO precipitate is subjected to ultrasonic waves at a frequency of 40 kHz and a power of 450 W for a period of 2 h. This process enhances the homogeneity of the GO dispersion and increases its surface area, making it more suitable for use in subsequent processing steps. (b) Desired volume of sols can be produced by mixing BGNs and BGNs/GO with a liquid solvent, which facilitates the formation of a sol. The sol preparation process involves mixing, stirring, and sonication to ensure a homogeneous mixture. (c) Chemical structure of the PGLA (poly(glycolide-co-lactide)) suture. The chemical structure of the PGLA suture is a long-chain polymer composed of repeating units of glycolide and lactide. (d) Experimental demonstration of the coating process of the suture composite samples by the VSD method. This process involves preparing a liquid sol of the coating material and depositing it onto the suture composite samples using a vacuum chamber. (e) Drying and cross-linking cycle of coated suture composite samples (20 cm length) is described in this step. Once the coating has been applied, the samples undergo a drying and cross-linking cycle to ensure that the coating adheres to the surface of the suture composite samples. The cross-linking process involves the formation of chemical bonds between the coating material and the surface of the suture composite samples, resulting in a strong and durable bond.