Surface and bulk modifications to photocrosslinked polyanhydrides to control degradation behavior

Abstract

A unique class of surface-eroding polyanhydrides was developed and explored for use in medical applications requiring high-strength biomaterials (e.g., orthopedics). In particular, dimethacrylated anhydride monomers were synthesized that photopolymerize quickly to render densely crosslinked polymer networks that degrade from the surface only by hydrolysis of labile anhydride linkages. Previous research on these materials has shown that the rate of hydrolysis of the degradable linkages is dependent on the hydrophobicity of the network composition. This article demonstrates the versatility in controlling the degradation process and resulting cellular response in these materials through the incorporation of new chemistries and the formation of polymer-polymer composite structures. Specifically, the rate of mass loss was controlled by the addition of hydrophobic linear polymers [e.g., poly(methyl methacrylate)] or monovinyl monomers based on hydrophobic natural components (e.g., cholesterol, steric acid). In addition, a newly established photografting method was used to modify the network surface chemistry with cholesterol- and stearic acid-based polymer grafts to control the degradation front and cellular interactions at the polymer-tissue interface. Finally, a porogen leaching method was used to form porous polyanhydride constructs, which can be subsequently filled with osteoblasts photoencapsulated in a hydrogel, as potential synthetic allograft materials for tissue engineering bone.

Identification of osteoconductive and biodegradable polymers from a combinatorial polymer library

“…This will hopefully allow for minimal toxicity from the degradation products, yet provide support during the approximate time for a fracture to heal and the bony callus to resorb. 29,30 …”

“…This will hopefully allow for minimal toxicity from the degradation products, yet provide support during the approximate time for a fracture to heal and the bony callus to resorb. 29,30 From the original PBAE library of 120 polymers, 10 macromers [ Fig. 1(A6,A7,B1,B2,C11,C12,E1,E2,E9,J6)] were identified as forming polymer networks that meet this mass loss criteria.…”

Concurrent release of admixed antimicrobials and salicylic acid from salicylate‐based poly(anhydride‐esters)

“…Polyanhydrides are often defined as surface-eroding materials 4 with tunable erosion mechanisms for tissue engineering and sensitive compounds, such as proteins. 42,43 This research sought to correlate drug release rate to polymer matrix erosion profiles based on water uptake and mass loss. The varied solubility parameters and immiscibility of the polymer/antimicrobial blends were observed to influence drug release as demonstrated in related studies.…”

Hydrogels that allow and facilitate bone repair, remodeling, and regeneration

“…65, 115 Encapsulation approaches for bone tissue engineering were introduced by the Anseth group through a series of papers in 2000 and 2002 67, 116 demonstrating a photo-encapsulation method in acrylated PEG hydrogels. A key finding in this work was that encapsulation did not significantly alter cell viability.…”