Thermo-Responsive Mussel-Inspired Polypeptides Novel Surgical Adhesive & Hemostatic Biomaterials

Thermo-Responsive Mussel-Inspired Polypeptides: Novel Surgical Adhesive & Hemostatic Biomaterials

1.Research Background

Surgical sutures remain the mainstream wound closure method, yet they bring obvious drawbacks including residual needle scars, tissue irritation and secondary removal procedures. Commercially available tissue adhesives have critical defects: fibrin glue exhibits weak wet adhesion, while cyanoacrylate has poor biocompatibility and triggers severe inflammatory reactions, limiting their clinical application. Marine mussels can firmly adhere to moist substrates via abundant L-DOPA residues in adhesive proteins, inspiring massive biomimetic adhesive research. Existing mussel-mimetic polymers mostly suffer slow curing speed or insufficient underwater bonding strength. Besides, most reported bioadhesives lack thermo-responsive sol-gel transition capacity, which cannot form in-situ gel rapidly under human body temperature for instant hemostasis and wound sealing. Polypeptides possess outstanding biocompatibility, biodegradability and bioactivity, making them ideal biomedical carrier materials. However, multifunctional thermo-responsive polypeptide adhesives integrated with catechol, arginine, cysteine and lysine functional groups have rarely been systematically constructed and verified for skin & bone repair in animal models.

2.Research Significance

This work designs a series of multi-functional thermo-responsive polypeptides via NCA ring-opening polymerization, combining mussel-inspired catechol adhesion, electrostatic binding of arginine, thiol crosslinking of cysteine and thermo-sensitive EG₂-Glu segments. The research systematically characterizes their physicochemical properties, in vitro bonding performance and in vivo hemostasis & tissue repair capacity, filling the gap of multifunctional polypeptide surgical adhesives. The developed BPEDAC-BPEDAL composite material achieves robust wet adhesion on porcine skin and bone, realizes rapid in-situ gelation at 37 °C, low cytotoxicity and complete biodegradation. It provides a facile synthetic strategy for next-generation suture-free hemostatic & orthopedic adhesive biomaterials, offering reliable preclinical data for the translational development of polypeptide medical glues.

3.Research Content

Synthesis of Functional NCA Monomers & Polypeptide Copolymers Synthesize five amino acid NCA monomers (EG₂-Glu-NCA, DOPA-NCA, Arg-NCA, Cys-NCA, Ac-Lys-NCA); prepare four gradient copolymers (BPED, BPEDA, BPEDAC, BPEDAL) through sequential ring-opening polymerization initiated by 1,4-butanediol alkoxide initiator. Characterize molecular weight, dispersity via GPC & laser light scattering, and confirm chemical structure using ¹H NMR.

Thermo-Responsive & Surface Property Evaluation Test temperature-transmittance curves to verify sol-gel transition behavior; measure water contact angles at 25 °C and 37 °C to analyze temperature-dependent hydrophilic-hydrophobic transformation.

In Vitro Adhesion Performance Testing Follow ASTM standards to conduct lap-shear adhesion on porcine skin and tensile adhesion on porcine bone; optimize concentrations of HRP/H₂O₂ crosslinking agents, curing time and temperature; test elastic modulus of each polypeptide system.

Degradation & Cytotoxicity Assessment Carry out PBS enzymatic degradation experiment to record mass loss rate; adopt ISO10993 MTT assay with L929 fibroblasts to evaluate biocompatibility.

In Vivo Animal Model Validation Three animal models are established: rat liver hemorrhage hemostasis model, full-thickness skin incision healing model, and femoral osteotomy bone repair model; record blood loss, wound inflammation, tissue remodeling via X-ray and H&E histological staining.

4.Research Results

Polymer Synthesis & Thermoresponsive Features Four copolymers with controllable monomer incorporation ratios are successfully synthesized. All polymers show sharp sol-gel transition between 30–35 °C; contact angle rises from 27.5 °C (25 °C) to 72.5 °C (37 °C), proving weakened hydrophilicity at body temperature for rapid gel formation.

Outstanding Wet Adhesion Performance

Maximum lap-shear adhesion strength on porcine skin reaches 101.2 kPa; bone tensile adhesion peaks at 603 kPa.

37 °C significantly improves bonding strength versus room temperature; BPEDAC-BPEDAL hybrid system delivers the optimal mechanical property due to synergistic crosslinking of catechol, thiol and guanidinium groups.

Adhesion strength rises rapidly within 0.5–60 min curing and plateaus after 12 h; appropriate 1 wt% H₂O₂ and 1 mg/mL HRP achieve ideal oxidative crosslinking without over-oxidation damage.

Favorable Degradability & Biosafety BPEDAC loses over 70% mass within 72 h under protease-containing PBS, demonstrating full polypeptide biodegradation. MTT results show over 80% cell viability after 72 h incubation, with no obvious cell morphological damage, indicating negligible cytotoxicity.

Superior In Vivo Hemostasis & Repair Effect

Liver hemorrhage model: BPEDAC-BPEDAL reduces blood loss from 1.76 g (control) to 0.54 g within 3 min with instant gel sealing.

Skin incision: The polypeptide glue causes mild inflammation only at day 7, with complete dermis regeneration and no fibrosis at day 14, outperforming sutures and cyanoacrylate which induce persistent inflammatory hyperkeratosis.

Bone osteotomy: X-ray and histology prove complete bone remodeling within 60 days; the adhesive does not hinder osteoblast proliferation and trabecular reconstruction.

5.Discussion

Compared with traditional tissue adhesives, the thermo-responsive mussel-inspired polypeptides integrate multiple functional motifs to realize multi-crosslinking adhesion mechanisms including catechol coupling, thiol-ene click, electrostatic salt bridges and thermal phase separation, which jointly boost wet bonding strength on soft and hard tissues. The EG₂-Glu segment endows reversible sol-gel transition at physiological temperature, enabling minimally invasive in-situ injection and instant wound sealing without pre-setting. The fully polypeptide backbone ensures complete biodegradation into amino acid fragments with low systemic toxicity, solving the biocompatibility defects of cyanoacrylate. Limitations still exist: the synthetic process of multiple NCA monomers requires strict anhydrous operation, restricting large-scale industrial preparation. Future optimization can simplify polymerization routes and introduce low-cost natural amino acid raw materials. Meanwhile, further modification of polypeptide side chains will enhance antibacterial activity to realize integrated adhesive-hemostatic-antibacterial multifunctional biomaterials for wider clinical scenarios such as minimally invasive surgery and burn wound treatment. In general, this series of thermo-responsive polypeptides breaks the performance bottleneck of existing bioadhesives and possesses great commercial translation potential as suture-free surgical repair materials.

Reference:  Lu D D, Wang H S, Li T E, et al. Versatile Surgical Adhesive and Hemostatic Materials: Synthesis, Properties and Application of Thermo-responsive Polypeptides[J]. Chemistry of Materials, Just Accepted, online published 2017-06-13. https://doi.org/10.1021/acs.chemmater.7b00255.

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Email:   jennifer@dilunbio.com