Diamond-Like Carbon Depositing on the Surface of Polylactide Membrane for Prevention of Adhesion Formation During Tendon Repair

Peritendinous adhesion formation is one of the most common and challenging complications during the healing process following tendon injuries and tendon surgeries. Until now, approximately 30%–40% of patients suffer from peritendinous adhesion to the surrounding tissues after tendon surgeries. Pathologically, the granulation tissue invades into injury site from surrounding tissues to promote tendon healing as an exogenous repair. However, the excessive exogenous repair leads to abnormal adhesions to the surrounding tissue that limits tendon sliding, excursion, and range of motion, eventually restricting joint motion. The adhesions also increase the risk of a secondary tendon rupture because of the forceful training and mobilization. Furthermore, the decreased range of motion caused by adhesions can prolong rehabilitation and necessitate reoperation, reducing patients’ quality of life and exacerbating psycho-socioeconomic problems.

Electrospun fibrous polylactic acid (PLA) membranes are a popular anti-adhesion strategy that serve as a physical barrier. However, its wide application as anti-adhesion membrane, artificial scaffold and wound dressing may lead to foreign body reaction (FBR) after PLA membrane implantation, leading to local inflammation and thus destroying its anti-adhesion effect. On the other hand, the biodegradation and release of by-products of the PLA membrane aggravate the formation of peritendinous adhesions and impair its anti-adhesion efficiency. From these two perspectives, the degradation of PLA membrane and foreign body-induced macrophage polarization greatly weaken the anti-adhesion efficacy of PLA membrane. Therefore, modification of the PLA membrane is crucial to prevent inflammation caused by foreign bodies, delay biodegradation, and enhance anti-adhesion effects.

On April 30, 2024, Yao Xiao, Tao Zaijin of Shanghai Jiao Tong University & Ju Yufeng of Shanghai Tongji Hospital and others proposed the use of diamond-like carbon deposited on polylactic acid (PLA) film in the journal Nano-Micro Letters (impact factor 26.6) (DLC) as a biophysical mechanism of anti-adhesion barrier to encapsulate ruptured tendons in rats with tendon injury.The results indicate that PLA/DLC composite membrane exhibits more efficient anti-adhesion effect than PLA membrane, with histological score decreasing from 3.12 ± 0.27 to 2.20 ± 0.22 and anti-adhesion effectiveness increasing from 21.61% to 44.72%. Mechanistically, the abundant C=O bond functional groups on the surface of DLC can reduce reactive oxygen species level effectively; thus, the phosphorylation of NF-κB and M1 polarization of macrophages are inhibited. Consequently, excessive inflammatory response augmented by M1 macrophage-originated cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) is largely reduced. For biocompatibility evaluation, PLA/DLC membrane is slowly absorbed within tissue and displays prolonged barrier effects compared to traditional PLA membranes. Further studies show the DLC depositing decelerates the release of degradation product lactic acid and its induction of macrophage M2 polarization by interfering esterase and PLA ester bonds, which further delays the fibrosis process. It was found that the PLA/DLC membrane possess an efficient biophysical mechanism for treatment of peritendinous adhesion.

Highlights1

• The anti-adhesion effect of polylactic acid (PLA) membrane with diamond-like carbon (DLC) depositing is 44.72%, enhanced by 23.11% compared to PLA.