Biomaterial Strategies for Immunomodulation

Strategies to enhance, suppress, or qualitatively shape the immune response are of importance for diverse biomedical applications, such as the development of new vaccines, treatments for autoimmune diseases and allergies, strategies for regenerative medicine, and immunotherapies for cancer. However, the intricate cellular and molecular signals regulating the immune system are major hurdles to predictably manipulating the immune response and developing safe and effective therapies. To meet this challenge, biomaterials are being developed that control how, where, and when immune cells are stimulated in vivo, and that can finely control their differentiation in vitro. We review recent advances in the field of biomaterials for immunomodulation, focusing particularly on designing biomaterials to provide controlled immunostimulation, targeting drugs and vaccines to lymphoid organs, and serving as scaffolds to organize immune cells and emulate lymphoid tissues. These ongoing efforts highlight the many ways in which biomaterials can be brought to bear to engineer the immune system.Bill & Melinda Gates FoundationUnited States. Army Research Office. Institute for Soldier Nanotechnologies (Contract W911NF-13-D-0001)Ragon Institute of MGH, MIT and HarvardCancer Research Institute (New York, N.Y.) (Irvington Postdoctoral Fellowship)National Institutes of Health (U.S.) (Awards AI104715, CA172164, CA174795, and AI095109

Reduced Acute Inflammatory Responses to Microgel Conformal Coatings

Implantation of synthetic materials into the body elicits inflammatory host responses that limit medical device integration and biological performance. This inflammatory cascade involves protein adsorption, leukocyte recruitment and activation, cytokine release, and fibrous encapsulation of the implant. We present a coating strategy based on thin films of poly(N-isopropylacrylamide) hydrogel microparticles (i.e. microgels) cross-linked with poly(ethylene glycol) diacrylate. These particles were grafted onto a clinically relevant polymeric material to generate conformal coatings that significantly reduced in vitro fibrinogen adsorption and primary human monocyte/macrophage adhesion and spreading. These microgel coatings also reduced leukocyte adhesion and expression of pro-inflammatory cytokines (TNF-alpha, IL-1 beta, MCP-1) in response to materials implanted acutely in the murine intraperitoneal space. These microgel coatings can be applied to biomedical implants as a protective coating to attenuate biofouling, leukocyte adhesion and activation, and adverse host responses for biomedical and biotechnological applications

Chronic Inflammatory Responses to Microgel-Based Implant Coatings

Inflammatory responses to implanted biomedical devices elicit a foreign body fibrotic reaction that limits device integration and performance in various biomedical applications. We examined chronic inflammatory responses to microgel conformal coatings consisting of thin films of poly(N-isopropylacrylamide) hydrogel microparticles cross-linked with poly(ethylene glycol) diacrylate deposited on poly(ethylene terephthalate) (PET). Unmodified and microgel-coated PET disks were implanted subcutaneously in rats for 4 weeks and explants were analyzed by histology and immunohistochemistry. Microgel coatings reduced chronic inflammation and resulted in a more mature/organized fibrous capsule. Microgel-coated samples exhibited 22% thinner fibrous capsules that contained 40% fewer cells compared to unmodified PET disks. Furthermore, microgel-coated samples contained significantly higher levels of macrophages (80%) than unmodified PET controls. These results demonstrate that microgel coatings reduce chronic inflammation to implanted biomaterials

Amine functionalization of cholecyst-derived extracellular matrix with generation 1 PAMAM dendrimer

This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Biomacromolecules, copyright © American Chemical Society after peer review. To access the final edited and published work, see http://pubs.acs.org/doi/pdf/10.1021/bm701055k.A method to functionalize cholecyst-derived extracellular matrix (CEM) with free amine groups was established in an attempt to improve its potential for tethering of bioactive molecules. CEM was incorporated with Generation-1 polyamidoamine (G1 PAMAM) dendrimer by using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide and N-hydroxysuccinimide cross-linking system. The nature of incorporation of PAMAM dendrimer was evaluated using shrink temperature measurements, Fourier transform infrared (FTIR) assessment, ninhydrin assay, and swellability. The effects of PAMAM incorporation on mechanical and degradation properties of CEM were evaluated using a uniaxial mechanical test and collagenase degradation assay, respectively. Ninhydrin assay and FTIR assessment confirmed the presence of increasing free amine groups with increasing quantity of PAMAM in dendrimer-incorporated CEM (DENCEM) scaffolds. The amount of dendrimer used was found to be critical in controlling scaffold degradation, shrink temperature, and free amine content. Cell culture studies showed that fibroblasts seeded on DENCEM maintained their metabolic activity and ability to proliferate in vitro. In addition, fluorescence cell staining and scanning electron microscopy analysis of cell-seeded DENCEM showed preservation of normal fibroblast morphology and phenotype

Unconventional Maturation of Dendritic Cells Induced by Particles from the Laminated Layer of Larval Echinococcus granulosus

The larval stage of the cestode parasite Echinococcus granulosus causes hydatid disease in humans and livestock. This infection is characterized by the growth in internal organ parenchymae of fluid-filled structures (hydatids) that elicit surprisingly little inflammation in spite of their massive size and persistence. Hydatids are protected by a millimeter-thick layer of mucin-based extracellular matrix, termed the laminated layer (LL), which is thought to be a major factor determining the host response to the infection. Host cells can interact both with the LL surface and with materials that are shed from it to allow parasite growth. In this work, we analyzed the response of dendritic cells (DCs) to microscopic pieces of the native mucin-based gel of the LL (pLL). In vitro, this material induced an unusual activation state characterized by upregulation of CD86 without concomitant upregulation of CD40 or secretion of cytokines (interleukin 12 [IL-12], IL-10, tumor necrosis factor alpha [TNF-α], and IL-6). When added to Toll-like receptor (TLR) agonists, pLL-potentiated CD86 upregulation and IL-10 secretion while inhibiting CD40 upregulation and IL-12 secretion. In vivo, pLL also caused upregulation of CD86 and inhibited CD40 upregulation in DCs. Contrary to expectations, oxidation of the mucin glycans in pLL with periodate did not abrogate the effects on cells. Reduction of disulfide bonds, which are known to be important for LL structure, strongly diminished the impact of pLL on DCs without altering the particulate nature of the material. In summary, DCs respond to the LL mucin meshwork with a “semimature” activation phenotype, both in vitro and in vivo

IL-10-Functionalized Hydrogels Support Immunosuppressive Dendritic Cell Phenotype and Function

Biomaterial systems such as hydrogels enable localized delivery and postinjection modulation of cellular therapies in a wide array of contexts. Biomaterials as adjuvants have been an active area of investigation, but the study of functionalized biomaterials supporting immunosuppressive cell therapies for tolerogenic applications is still nascent. Here, we developed a 4-arm poly(ethylene-glycol)-maleimide (PEG-4MAL) hydrogel functionalized with interleukin-10 (IL-10) to improve the local delivery and efficacy of a cell therapy against autoimmune disease. The biophysical and biochemical properties of PEG-4MAL hydrogels were optimized to support dendritic cell (DC) viability and an immature phenotype. IL-10-functionalized PEG-4MAL (PEG-IL10) hydrogels exhibited controlled IL-10 release, extended the duration of DC support, and protected DCs from inflammatory assault. After incorporation in PEG-IL10 hydrogels, these DCs induced CD25+FoxP3+ regulatory T cells (Tregs) during in vitro coculture. These studies serve as a proof-of-concept for improving the efficacy of immunosuppressive cell therapies through biomaterial delivery. The flexible nature of this system enables its widespread application across a breadth of other tolerogenic applications for future investigation