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Chitosan bio-adhesives bond strongly with various biological tissues, such as skin, mucosa, and internal organs. Their adhesive ability arises from amino acid and hydroxyl groups in chitosan, facilitating interactions with tissue surfaces through chemical (ionic, covalent, and hydrogen) and physical (chain entanglement) bonding. As non-toxic, biodegradable, and biocompatible materials, chitosan bio-adhesives are a safe option for medical therapies. They are particularly suitable for drug delivery, wound healing, and tissue regeneration. In this review, we address chitosan-based bio-adhesives and the mechanisms associated with them. We also discuss different chitosan composite-based bio-adhesives and their biomedical applications in wound healing, drug delivery, hemostasis, and tissue regeneration. Finally, challenges and future perspectives for the clinical use of chitosan-based bio-adhesives are discussed. [ABSTRACT FROM AUTHOR]

The availability of grafts to replace small‐diameter arteries remains an unmet clinical need. Here, the validated methodology is reported for a novel hybrid tissue‐engineered vascular graft that aims to match the natural structure of small‐size arteries. The blood vessel mimic (BVM) comprises an internal conduit of co‐electrospun gelatin and polycaprolactone (PCL) nanofibers (corresponding to the tunica intima of an artery), reinforced by an additional layer of PCL aligned fibers (the internal elastic membrane). Endothelial cells are deposited onto the luminal surface using a rotative bioreactor. A bioprinting system extrudes two concentric cell‐laden hydrogel layers containing respectively vascular smooth muscle cells and pericytes to create the tunica media and adventitia. The semi‐automated cellularization process reduces the production and maturation time to 6 days. After the evaluation of mechanical properties, cellular viability, hemocompatibility, and suturability, the BVM is successfully implanted in the left pulmonary artery of swine. Here, the BVM showed good hemostatic properties, capability to withstand blood pressure, and patency at 5 weeks post‐implantation. These promising data open a new avenue to developing an artery‐like product for reconstructing small‐diameter blood vessels. [ABSTRACT FROM AUTHOR]

The synthesis of a porous shape‐changing interpenetrating network (IPN) bioink for the fabrication of large‐scale (cm) reversibly thermosensitive structures is described. The poly(N‐isopropylacrylamide) (PNIPAm) IPN is generated in situ within an ionically crosslinked alginate hydrogel at room temperature and under aerobic conditions using a horseradish peroxidase (HRP)/glucose oxidase (GOx) bienzymatic initiation system. Mechanical testing assessment of the IPN hydrogels confirm mechanical reinforcement via covalent single network interdigitation. Furthermore, the thermosensitive bioink can be used to print biohybrid reactors containing genetically engineered phosphotriesterase‐expressing E. coli capable of hydrolyzing toxic organophosphorus compounds. Herein, increasing the bioink pore size using the contractile‐thermosensitive response of the IPN improves the temperature‐dependent theoretical mass‐transfer‐limited enzyme catalyzed reaction rate, providing a plausible route to externally regulated enzymatic catalysis within bioprinted structures. [ABSTRACT FROM AUTHOR]

Acoustic fields are increasingly being used in material handling applications for gentle, noncontact manipulation of particles in fluids. Sonolithography is based on the application of acoustic radiation forces arising from the interference of ultrasonic standing waves to direct airborne particle/droplet accumulation in defined spatial regions. This approach enables reliable and repeatable patterning of materials onto a substrate to provide spatially localized topographical or biochemical cues, structural features, or other functionalities that are relevant to biofabrication and tissue engineering applications. The technique capitalizes on inexpensive, commercially available transducers and electronics. Sonolithography is capable of rapidly patterning micrometer to millimeter scale materials onto a wide variety of substrates over a macroscale (cm2) surface area and can be used for both indirect and direct cell patterning. [ABSTRACT FROM AUTHOR]

The changes in the surface structure of lysozyme adsorbed at the air-water interface produced by the chemical denaturant guanidinium chloride are examined. The methodologies to predict the protein orientation at the interface, based on amino acid residues' surface affinities and charge, are validated.

The x-ray and neutron reflectometry measurements are used for studying the structural changes caused by chemical denaturation of a surface excess of the bovine milk protein, [beta]-lactoglobulin. The interfacial free energy of unfolding in the absence of a denaturant has shown that the air-water interface has a destabilizing effect on protein structure.

The structure of the interface generated by a spread layer of beta-casein on an aqueous colloidal poly(silicic) acid subphase is examined using C-rays and neutrons. The use of multiple contrasts enables the scattering from the protein and the subphase to be decoupled to allow the surface excess of protein and volume fraction of water at the interface to be evaluated without assumptions regarding the volume of the protein.