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We describe a method for fabricating biocompatible chitosan-based adhesives with sub-micron structures to enhance tissue bonding. This procedure avoids coating and chemical modification of structures and requires a simple drop-casting step for the adhesive film formation. Chitosan thin films (27±3 μm) were fabricated with sub-micron pillars (rectangular cuboid with height ∼150 nm, square dimension ∼1 μm and pitch ∼2 μm) or holes (diameter ~500 nm or ~1 μm, depth ~100 or 400 nm, pitch of 1 or 2 μm). Polydimethylsiloxane moulds were used as negative templates for the adhesive solution that was cast and then allowed to dry to form thin films. These were applied on bisected rectangular strips of small sheep intestine and photochemically bonded by a green laser (λ= 532 nm, irradiance ∼110 J/cm2). The tissue repair was subsequently measured using a computer-interfaced tensiometer. The mould sub-micron structures were reproduced in the chitosan adhesive with high fidelity. The adhesive with pillars achieved the highest bonding strength (17.1±1.2 kPa) when compared to the adhesive with holes (13.0±1.3 kPa, p

An original wireless stimulator for peripheral nerves based on a metal loop (diameter ≈1 mm) that is powered by a transcranial magnetic stimulator (TMS) and does not require circuitry components is reported. The loop can be integrated in a chitosan scaffold that functions as a graft when applied onto transected nerves (graft‐antenna). The graft‐antenna is bonded to rat sciatic nerves by a laser without sutures; it does not migrate after implantation and is able to trigger steady compound muscle action potentials for 12 weeks (CMAP ≈1.3 mV). Eight weeks postoperatively, axon regeneration is facilitated in transected nerves that are repaired with the graft‐antenna and stimulated by the TMS for 1 h per week. The graft‐antenna is an innovative and minimally‐invasive device that functions concurrently as a wireless stimulator and adhesive scaffold for nerve repair.

A range of chitosan–based biomaterials have recently been used to perform sutureless, laser-activated tissue repair. Laser-activation has the advantage of bonding to tissue through a non-contact, aseptic mechanism. Chitosan adhesive films have also been shown to adhere to sheep intestine strongly without any chemical modification to chitosan. In this study, we continue to investigate chitosan adhesive films and explore the impact on the tissue repair strength and tensile strength characteristics of four types of adhesive film based on chitosan with different molecular weight and degree of deacetylation. Results showed that adhesives based on chitosan with medium molecular weight achieved the highest bonding strength, tensile strength and E-modulus when compared to the other adhesives. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Sutureless procedures for wound repair and closure have recently integrated nanostructured devices to improve their effectiveness and clinical outcome. This review highlights the major advances in gecko-inspired bioadhesives that relies mostly on van der Waals bonding forces. These are challenged by the moist environment of surgical settings that weaken adherence to tissue. The incorporation of nanoparticles in biomatrices and their role in tissue repair and drug delivery is also reviewed with an emphasis on procedures involving adhesives that are laser-activated. Nanostructured adhesive devices have the advantage of being minimally invasive to tissue, can seal wounds, and deliver drugs in situ. All these tasks are very difficult to accomplish by sutures or staples that are invasive to host organs and often cause scarring.

A range of chitosan-based biomaterials have recently been used to perform sutureless, laser-activated tissue repair. Laser-activation has the advantage of bonding to tissue through a non-contact, aseptic mechanism. Chitosan adhesive films have also been shown to adhere to sheep intestine strongly without any chemical modification to chitosan. In this study, we continue to investigate chitosan adhesive films and explore the impact on the tissue repair strength and tensile strength characteristics of four types of adhesive film based on chitosan with different molecular weight and degree of deacetylation. Results showed that adhesives based on chitosan with medium molecular weight achieved the highest bonding strength, tensile strength and E-modulus when compared to the other adhesives.

This study describes a simple one-step fabrication process of a chitosan film that has nanoscale pillars. The adhesive is laser-bonded to tissue and does not require pillar coating to enhance bonding in water. In comparison with a ‘flat’ adhesive without pillars, the nanostructured adhesive bonded significantly stronger to tissue under either stress or pressure. This adhesive combines two mechanisms for tissue bonding: one based on the nanopatterned surface that increases the adhesion strength over short distances (van der Waals and electrostatic interactions) and another based on elastic interaction with polymer chains over much longer distances.