New surgical stitches capable of generating electrical charge may accelerate wound healing

Tested on rats, the stitches proved effective in treating wounds and could offer a cost-effective alternative to traditional sutures. 

In a recent study published in Nature Communications, researchers developed a bioabsorbable electrical stimulation (ES) suture (BioES-suture).

Background

Chronic and acute surgical wounds are common in clinical practice. Complete sealing of the opened tissue is essential for healing and minimizing complications, particularly for incisional wounds caused by surgery or trauma. Suture fibers have historically been used to close wounds. While synthetic absorbable sutures cause minimal tissue reaction and are biocompatible, they do not accelerate wound healing.

ES has been reported to be effective for wound care in non-pharmacological therapies as it mimics the natural healing mechanism of an endogenous electric field. It stimulates growth factor production and reception, promotes the migration of sodium and potassium ions between tissues, directs neurite growth, and induces cell proliferation and migration.

Self-powered ES devices have been developed, which significantly expedite wound healing. However, these devices are mainly used for microtrauma, nerve or bone repair, etc., and cannot be used at sites requiring suturing. Moreover, ES devices are partly not degradable or absorbable in the human body.

The study and findings

In the present study, researchers developed BioES-suture, a passive continuous bioabsorbable mechanoelectric fiber, as an ES suture. The suture can be prepared via a continuous process; poly(lactic-co-glycolic acid) (PLGA) nanofibers were twisted onto the surface of the magnesium filament electrode, forming the preassembled core fiber (Mg@PLGA).

Next, the preassembled core fiber was extracted from the polycaprolactone (PCL) melt. PCL was rapidly cooled and wrapped around the core fiber to yield the BioES-suture. The PLGA and PCL layers represented the power generation unit, while the magnesium filament was the electrical energy harvesting unit. The BioES-suture exhibited a higher tensile strength than commercial non-absorbable and bioabsorbable sutures.

Biocompatibility of the BioES-suture was evaluated by culturing fibroblasts in sheared magnesium filaments, Mg@PLGA, and BioES-suture. The non-stagnant proliferation and normal spreading of fibroblasts indicated that the BioES-suture was non-toxic and biocompatible. Next, the team measured the power generation performance of the suture.

The BioES-suture was used on artificial muscle fibers and immersed in water to generate electricity through the potential difference of contact separation between the PCL sheath and PLGA core layers. Its electrical output could power an LCD screen. Further, the researchers compared the electrical output in water and air. The output voltage was 1.39V higher in water than in air and remained stable at different frequencies.

Next, the team analyzed the in vitro degradation of the BioES-suture. The suture and magnesium electrode were incubated in phosphate-buffered saline (PBS) for degradation. The electrode and preassembled core fiber were degraded within 14 days. However, there was no degradation of the BioES-suture after 24 weeks.

Further, rat leg musculature was stitched using the BioES-suture. The output voltage during normal exercise was 2.3V, comparable to in vitro stimulation, indicating that BioES-suture could convert body movements into stable electrical impulses. Next, the team used the BioES-suture on bleeding muscle incisions in Sprague-Dawley rats. Two other rat groups included bioabsorbable-suture (bio-suture) and no-suture (control) groups.

The researchers measured electromyographic signals in the three groups and noted significantly higher signal intensity in the BioES-suture group; signal intensity was similar between the bio-suture and control groups. In addition, they performed hematoxylin-eosin and Masson trichrome staining on wound tissues. The BioES-suture group showed improved tissue migration, accelerated wound regeneration, and almost complete healing.

Collagen deposition was also evident in the BioES-suture group, reminiscent of the remodeling phase of normal wound healing. Besides, there was no significant fibrosis in the healed tissue in the BioES group. The wound closure rate was 96.5% for the BioES-suture group, 82.2% for the bio-suture group, and 60.4% for controls. Finally, the team established a rat wound-infection model and used ordinary surgical sutures and the BioES-suture.

Wound tissues were obtained a week later for bacterial count and culture. The BioES-suture had better healing outcomes than ordinary surgical sutures, significantly reducing bacterial counts in culture. Moreover, investigations into antimicrobial properties demonstrated that the BioES-suture group had relatively low bacterial counts (even) without daily wound disinfection compared to rats with ordinary surgical sutures and daily wound disinfection.

Conclusions

Together, the researchers developed BioES-suture for accelerated wound healing by converting body movements into effective ES. The suture exhibits comparable strength to standard commercial sutures.

In vitro and in vivo experiments revealed that the suture could generate an endogenous electric field at the wound site for ES, promote cell proliferation and migration, and alleviate infection risk.

Overall, the findings underscore that BioES-suture is a safe, advanced, biodegradable suture that could be translated into clinical practice.