This review highlights the research on degradable polymeric tissue adhesives for surgery and tissue engineering. Included are a comprehensive listing of specific uses, advantages, and disadvantages of different adhesive groups. A critical evaluation of challenges affecting the development of next generation materials is also discussed, and insights into the outlook of the field are explored.

Bone and tissue adhesives are essential in surgeries for wound healing, hemostasis, tissue reconstruction, and drug delivery. However, there are very few degradable materials with high adhesion strengths that degrade into bioresorbable byproducts. Caddisfly adhesive silk is interesting due to the presence of phosphoserines, which are thought to afford adhesive properties. In this work, phosphoserine-valine poly(ester urea) copolymers with 2% and 5% phosphoserine content were synthesized to mimic caddisfly adhesive silk. Significantly, the materials are ethanol soluble and water insoluble, making them clinically relevant. Their physical properties were quantified, and the adhesion properties were studied on aluminum and bovine bone substrates before and after cross-linking with Ca(2+) ions. The adhesive strength of the phosphorylated copolymer on a bone substrate after cross-linking with Ca(2+) was 439 ± 203 kPa, comparable to commercially available PMMA bone cement (530 ± 133 kPa).

The adhesive nature of mussels arises from the catechol moiety in the 3,4-dihydroxyphenylalanine (DOPA) amino acid, one of the many proteins that contribute to the unique adhesion properties of mussels. Inspired by these properties, many biomimetic adhesives have been developed over the past few years in an attempt to replace adhesives such as fibrin, cyanoacrylate, and epoxy glues. In the present work, we synthesized ethanol soluble but water insoluble catechol functionalized poly(ester urea) random copolymers that help facilitate delivery and adhesion in wet environments. Poly(propylene glycol) units incorporated into the polymer backbone impart ethanol solubility to these polymers, making them clinically relevant. A catechol to cross-linker ratio of 10:1 with a curing time of 4 h exceeded the performance of commercial fibrin glue (4.8 ± 1.4 kPa) with adhesion strength of 10.6 ± 2.1 kPa. These adhesion strengths are significant with the consideration that the adhesion studies were performed under wet conditions.

Hybrid nanoparticle based on quantum dots and dye labeled PNIPAM shows ratiometric changes in fluorescence emission upon temperature cycling between 25 °C and 45 °C.