Research ArticleAPPLIED SCIENCES AND ENGINEERING

Bioinspired tough gel sheath for robust and versatile surface functionalization

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Science Advances  07 Apr 2021:
Vol. 7, no. 15, eabc3012
DOI: 10.1126/sciadv.abc3012
  • Fig. 1 Bioinspired design of TGS suture.

    Schematics of the structural and material design of (A) tendon and (B) TGS suture. Scanning electron microscope images of (C) TGS suture and (D) a zoom-in at the suture-sheath interface. Scale bars, 100 (C) and 25 μm (D). (E) Bright- field image of TGS suture. Scale bar, 500 μm. (F) A continuous stitch applied on porcine skin using TGS suture. Scale bar, 1 cm. Photo credit: Zhenwei Ma, McGill University.

  • Fig. 2 Strong adhesion of TGS and suture.

    Representative force-displacement curves (A) and the adhesion energy (B) measured from the pull-out tests [inset in (A)] of gel-sheathed sutures formed with polyglactin 910 suture and different hydrogels. Alg, alginate; Chi, chitosan. (C) Adhesion energy as a function of NaOH treatment time. (D) FEM results of the normalized adhesion energy (Γ/Γ0) as a function of the ratio of the sheath thickness and the suture radius (rg/rs). The force-displacement curves of pull-out test (E) and the adhesion energy (F) of TGS sutures encompassing various suture materials, including polyglactin 910 (PLGA), plain gut, and nylon. Data reported as means ± SD for n = 3 independent experiments.

  • Fig. 3 Improved biomechanical properties of the TGS suture.

    (A) Stress-strain curves of the pristine and TGS sutures (polyglactin 910). (B) Representative microindentation force-indentation depth curve measured on the TGS suture surface. AFM, atomic force microscope. (C) Schematic of the tissue drag test. (D) Representative drag force-displacement curves of the pristine and TGS sutures. (E) Drag coefficients of suture (pristine or TGS) interfacing with various tissues (heart, skin, and liver). (F) Schematic of the ex vivo friction test of the suture placed on articular cartilage, where the PDMS is used as a substrate. Representative friction force-sliding distance curves (G) and the calculated friction coefficients (H) of intact cartilage and sutured cartilage with the pristine or TGS suture. Data reported as means ± SD for n = 3 independent experiments; ***P < 0.001, by two-tailed, one-way analysis of variance (ANOVA) with Holm-Sidak post hoc comparison.

  • Fig. 4 Versatile TGS suture functionalization.

    (A) Representative fluorescence images of live (green)/dead (red) assay of bacteria (P. aeruginosa and S. aureus) seeded onto the pristine or TGS suture. Scale bar, 10 μm. (B) Total number of bacteria adhesion on pristine or TGS sutures. (C) Over 99% bacteria were killed on TGS sutures loaded with BZK. Representative images (D) and quantitative color change assay (reflected in gray scale) (E) of pH-sensing TGS suture immersed in solution with various pH levels. Photo credit: Zhenwei Ma, McGill University. (F) Seven-day normalized cumulative release profile of FITC-BSA from the pristine or TGS suture. (G) BSA loading capacity of pristine or TGS suture. Data reported as means ± SD for n = 3 independent experiments; ***P < 0.001, by two-tailed, one-way ANOVA with Holm-Sidak post hoc comparison.

  • Fig. 5 Fluorescent suture for NIR bioimaging.

    (A) Representative transmission electron microscopy (TEM) image of mSiO2@PbS/CdS-Fe3O4 fluorescent NPs. Scale bar, 50 nm. (B) Fluorescent emission spectrum of mSiO2@PbS/CdS-Fe3O4 in the NIR-II window. a.u., arbitrary units. (C) Schematic of the ex vivo experimental setup to characterize the photoluminescence penetration of fluorescent NP–loaded TGS suture behind porcine tissue. (D) Representative fluorescence images (top) and normalized intensity (bottom) of the TGS sutures under tissues of varying thickness.

  • Fig. 6 In vivo biocompatibility and wound closure of pristine and TGS sutures.

    (A) Schematic illustration of the subcutaneous implantation of suture knots. The biocompatibility was assessed on days 7 and 14. (B) View of the suture knots implantation process and macroscopic inspection of the encapsulated suture knots on days 7 and 14. Photo credit: Zhenwei Ma and Qiman Gao, McGill University. (C) Degree of inflammation of implanted pristine and TGS sutures evaluated blindly by an experienced pathologist (0, normal; 1, very mild;, 2, mild; 3, moderate; 4, severe; 5, very severe). Statistical significance and P values are determined by two-sided Student’s t test. “*” indicates P < 0.5; “n.s.” indicates not significant. (D to K) Representative histology images stained with hematoxylin and eosin (H&E) of suture knot implanted for 7 days [pristine (D and H); TGS (F and J)] and 14 days [pristine (E and I); TGS (G and K)]. (H) to (K) are histological images of higher magnification of regions interest (rectangle with dashed red lines) from (D) to (G). White arrowheads indicate foreign body giant cells; star symbols indicate proinflammatory eosinophils. (L) Schematic illustration of incision wounds closed with pristine and TGS sutures as well as sections taken for histology (dotted red line) on day 7. (M and N) Representative histological images stained with H&E showing comparable wound healing outcome using pristine (M) and TGS (N) sutures, assessed blindly by an experienced pathologist (n = 6). Dashed white lines indicate wound edges.

Supplementary Materials

  • Supplementary Materials

    Bioinspired tough gel sheath for robust and versatile surface functionalization

    Zhenwei Ma, Zhen Yang, Qiman Gao, Guangyu Bao, Amin Valiei, Fan Yang, Ran Huo, Chen Wang, Guolong Song, Dongling Ma, Zu-Hua Gao, Jianyu Li

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