"Adhesive biomaterials have been studied by the scientific community in an attempt to surpass the current disadvantages of sutures and staples in surgery, such as the challenging implementation in some tissues and the risk of infection. The developed bioadhesives have been used as: i) glues for maintaining biological tissues together after laceration; ii) tissue sealants for preventing the leakage of body fluids, and; iii) hemostatic agents for helping generate the blood clot. Despite the potential of this area, whose market size was valued at USD 1.8 billion in 2015 and is projected to grow 9.7% annually, existent adhesive materials approved by the Food and Drug Administration (FDA), still present several limitations. Some are not biocompatible or their degradation produces cytotoxic by-products, others lack bulk strength and bioactive properties, and some have proinflammatory potential.
Regarding wet-adhesion, mussel-inspired bioadhesives have gained attention, mimicking the mussel´s strong underwater adhesion, using catechol groups in the compound’s structures. Tannic acid (TA), a plant-derived polyphenol, is a safe and low-cost source of catechol/pyrogallol groups. It allows polymeric crosslinking through hydrogen and ionic bonding, or hydrophobic interactions, improving biomaterials adhesiveness and mechanical performance, while endowing it with anti-microbial, anti-inflammatory and antioxidant properties. Hence, by combining laminarin (LAM-OH) or pullulan (PUL-OH), two natural origin polisaccharides with TA, bioinspired adhesive biomaterials for biomedical applications were produced.
A library of bioadhesives was fabricated by combining PUL-OH and LAM-OH with TA in several concentrations, having the best formulations been chosen by lap shear test performance. Then, LAM-OH and PUL-OH were functionalized with methacrylic groups, having the modification of the polymers backbone (LAM-MET and PUL-MET) been successfully confirmed by 1H-NMR spectroscopy and FTIR. In the previous best formulations, the natural polysaccharides were substituted by LAM-MET and PUL-MET, respectively, and the bioadhesives presented adhesion to wet porcine skin, contrary to some already commercialized cyanoacrylate adhesives. Rheological and biological properties were also evaluated. Therefore, the present bioadhesives show good perspectives for being implemented as soft tissue bioadhesives.
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