Electrospining Machine: Preparation of ultraflexible multiscale patterned fiber tube scaffolds with morphologic features using coiled static electrospinning method

Background

Synthetic vessels are used clinically for vascular bridging in cardiovascular disease or hemodialysis, and autologous vessels are an option depending on the condition of the vessel. However, synthetic vascular grafts are more commonly used than autologous vascular grafts due to the insufficient supply of grafts from large-diameter (≥6 mm) to small-diameter (< 6 mm) vessels. However, vascular grafts suffer from a number of defects, including rapid intimal hyperplasia, stenotic occlusion, aneurysm formation, and thrombosis, which often stem from the challenge of maintaining the tubular structure of the graft, resulting in impaired circulation.

The main point of this paper

Risks after vascular graft surgery:

Serious risks such as intimal hyperplasia, luminal dilatation, and thrombosis may be faced after vascular graft surgery, and these problems are usually associated with inadequate mechanical properties of the artificial vascular grafts, such as mechanical strength and resistance to kinking

Electrospinning technology in tissue engineering:

Electrospinning technology is widely used to prepare biomimetic fibrous scaffolds that mimic the structure of the extracellular matrix (ECM), provide cells with an environment similar to that of natural tissues, and support cell adhesion and intercellular communication

Properties of nanofibers and their effects on cell behavior:

Nanofibers are characterized by large specific surface area, high porosity, good mechanical properties, and controllable morphological size, which can promote cell infiltration and attachment as well as provide mechanical stability

Vascular grafts prepared by improved electrospinning technique:

Ultraflexible fibrous tubular scaffolds (FTS) with aligned and randomly oriented multiscale fibers, developed by an improved electrospinning device, exhibit excellent properties in terms of shape retention and resistance to kinking

Material selection and FTS preparation:

FDA-approved polycaprolactone (PCL) and sericin protein were chosen as materials for the preparation of vascular grafts because of their good mechanical properties and biocompatibility

Topographic characterization and mechanical properties of FTS:

The topographical features of the new FTS influence the formation of multi-scale fibers through the use of an improved collector design, related to humidity and temperature during processing, which is a key factor in improving the mechanical properties of the fibers

In vivo and ex vivo experimental results:

PCL/silk protein fiber tubular scaffolds prepared under high humidity conditions (PSFTS-HH) were superior to scaffolds prepared under low humidity conditions (PSFTS-LH) in retaining their shape and resisting kinking, and the mechanical properties of the designed vascular grafts showed significant improvement in in vivo results

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Potential and challenges of FTS as vascular grafts:

Fiber-tube stents (FTS) have the potential to be used as vascular grafts, but their inadequate mechanical properties hinder clinical application.

Consequences of inadequate mechanical properties:

Inadequate mechanical properties of vascular grafts may lead to serious side effects such as intimal hyperplasia, lumen dilatation, and thrombosis.

Development of a novel FTS:

A novel FTS composed of multi-scale fibers was developed in the study to ensure superior mechanical properties.

One-step manufacturing method:

The novel FTS was produced by a modified electrostatic spinning device using a one-step manufacturing method, which enables the fabrication of super flexible fiber tube scaffolds (SF-FTS) with topographical features.

Critical factors in the preparation process:

The effects of humidity and temperature on the formation of multi-scale fibers during the preparation process were investigated, and these factors are critical for improving the mechanical properties of FTS.

Significant improvement in mechanical properties:

The incorporation of multi-scale fibers and topographical features significantly improved the mechanical properties of FTS, as confirmed by anti-torsion tests, compression tests and in vivo experiments..

Summarize

In this study, we report the preparation of ultra-flexible PCL/silk fiber tubular scaffolds using a modified electrostatic spinning device in a controlled environment. We successfully developed PSFTS-HH with multiscale fibers with excellent mechanical properties. We found that multiscale fibers can be fabricated in specific environments and they also have topographical features.The presence of multiscale fibers in PSFTS-HH provides excellent flexibility and shape stability. These prominent features were demonstrated in the in vivo differentiation results. After implantation, PSFTS-HH fully maintained the tubular structure and promoted tissue regeneration more efficiently than PSFTS-LH.PSFTS-HH is considered to be a suitable candidate to overcome the mechanical limitations of vascular grafts in clinical applications. Furthermore, topographical cues of PSFTS-HH induced cell elongation and alignment as well as structural effects. This new discovery provides an advanced electrostatic spinning method for the fabrication of advanced fibrous tube scaffolds that are ultra-flexible and promote tissue regeneration, offering a practical solution for vascular grafts.