Anti-inflammatory polymeric coatings for implantable biomaterials and devices

Abstract

Synthetic polymer coatings are used extensively in modern medical devices and implants because of their material versatility and processability. These coatings are designed for specific applications by controlling composition and physical and chemical properties, and they can be formed into a variety of complex structures and shapes. However, implantation of these materials into the body elicits a strong inflammatory host response that significantly limits the integration and biological performance of devices. Biomaterial-mediated inflammation is a complex reaction involving protein adsorption, leukocyte recruitment and activation, secretion of inflammatory mediators, and fibrous encapsulation of the implant. Significant research efforts have focused on modifying material properties using various anti-inflammatory polymeric surface coatings to generate more biocompatible implants. This minireview provides a brief background on the events of biomaterial-mediated inflammation and highlights various approaches used for modifying material surfaces to modulate inflammatory responses. These include both passive and active strategies, such as nonfouling surface treatments and delivery of anti-inflammatory agents, respectively. Novel approaches will be needed to extend the in vivo lifetime and performance of devices and reduce the need for multiple implantation surgeries.

Keywords: anti-inflammatory; biomaterial; coating; host response; implant; polymer.

Figure 1.

Events of host foreign body response to implanted materials. Neutrophils and monocytes recruited by stimulatory cues emigrate from the vasculature and adhere to the layer of adsorbed proteins on the implant surface (Phases 1–3). Differentiated macrophages become activated, secreting a variety of inflammatory mediators, and often fuse into multinucleated foreign body giant cells (Phases 4-6). Fibroblasts infiltrate the site and generate a collagenous fibrous capsule around the implant (Phase 7). BV, blood vessel; PMN, polymorphonuclear leukocyte; MC, immature monocyte; MΦ, differentiated macrophage; FBGC, foreign body giant cell; FB, fibroblast.

Figure 2.

Passive anti-inflammatory surface coating for biomaterials. Hydrophilic polymeric coatings, such as PEG-based hydrogels, retain interfacial water molecules, rendering them highly resistant to protein adsorption.

Figure 3.

Bioactive implant coatings to deliver anti-inflammatory molecules. Representative schemes depict mechanisms for the active delivery of various immunomodulatory agents to reduce leukocyte adhesion and activation.