Artificial Antigen-Presenting Cell Topology Dictates T Cell Activation

Contains fulltext : 283270.pdf (Publisher’s version ) (Open Access

Multifunctional, Multivalent PIC Polymer Scaffolds for Targeting Antigen-Specific, Autoreactive B Cells

Multivalent scaffolds that carry multiple molecules with immunophenotyping or immunomodulatory properties areinvaluable tools for studying and modulating specific functions ofhuman immune responses. So far, streptavidin-biotin-basedtetramers have been widely used for B-cell immunophenotypingpurposes. However, the utility of these tetramers is limited by theirtetravalency, the inherent immunogenicity of streptavidin (abacterial protein that can potentially be recognized by B cells),and the limited feasibility to functionalize these reagents. This has rendered tetramers suboptimal for studying rare, in particular,antigen-specific B-cell populations in the context of clinical applications. Here, we used polyisocyanopeptides (PICs), multivalentpolymeric scaffolds functionalized with around 50 peptide antigens, to detect autoreactive B cells in the peripheral blood of patientswith rheumatoid arthritis. To explore the potential immunomodulatory functionalities, we functionalized PICs with autoantigenicpeptides and a trisaccharide CD22 ligand to inhibit autoreactive B-cell activation through interference with the B-cell receptoractivation pathway, as evidenced by reduced phospho-Syk expression upon PIC binding. Given the possibilities to functionalizePICs, our data demonstrate that the modular and versatile character of PIC scaffolds makes them promising candidates for futureclinical applications in B-cell-mediated diseasesPathophysiology and treatment of rheumatic disease

Water-soluble polyisocyanopeptides : Development of multifunctional bioconjugates for biomedical applications

Contains fulltext : 160651.pdf (publisher's version ) (Open Access)Radboud University, 16 november 2016Promotores : Rowan, A.E., Figdor, C.G. Co-promotor : Blank, K.G.192 p

Biomimetic Stress Sensitive Hydrogel Controlled by DNA Nanoswitches

Contains fulltext : 178194.pdf (publisher's version ) (Open Access)One of the most intriguing and important aspects of biological supramolecular materials is its ability to adapt macroscopic properties in response to environmental cues for controlling cellular processes. Recently, bulk matrix stiffness, in particular, stress sensitivity, has been established as a key mechanical cue in cellular function and development. However, stress-stiffening capacity and the ability to control and exploit this key characteristic is relatively new to the field of biomimetic materials. In this work, DNA-responsive hydrogels, composed of semiflexible PIC polymers equipped with DNA cross-linkers, were engineered to create mimics of natural biopolymer networks that capture these essential elastic properties and can be controlled by external stimuli. We show that the elastic properties are governed by the molecular structure of the cross-linker, which can be readily varied providing access to a broad range of highly tunable soft hydrogels with diverse stress-stiffening regimes. By using cross-linkers based on DNA nanoswitches, responsive to pH or ligands, internal control elements of mechanical properties are implemented that allow for dynamic control of elastic properties with high specificity. The work broadens the current knowledge necessary for the development of user defined biomimetic materials with stress stiffening capacity

Semiflexible polymer scaffolds : an overview of conjugation strategies

Contains fulltext : 234100.pdf (Publisher’s version ) (Open Access

Controlling T-Cell Activation with Synthetic Dendritic Cells Using the Multivalency Effect

Contains fulltext : 174408.pdf (publisher's version ) (Open Access)Artificial antigen-presenting cells (aAPCs) have recently gained a lot of attention. They efficiently activate T cells and serve as powerful replacements for dendritic cells in cancer immunotherapy. Focusing on a specific class of polymer-based aAPCs, so-called synthetic dendritic cells (sDCs), we have investigated the importance of multivalent binding on T-cell activation. Using antibody-functionalized sDCs, we have tested the influence of polymer length and antibody density. Increasing the multivalent character of the antibody-functionalized polymer lowered the effective concentration required for T-cell activation. This was evidenced for both early and late stages of activation. The most important effect observed was the significantly prolonged activation of the stimulated T cells, indicating that multivalent sDCs sustain T-cell signaling. Our results highlight the importance of multivalency for the design of aAPCs and will ultimately allow for better mimics of natural dendritic cells that can be used as vaccines in cancer treatment

Stress-stiffening-mediated stem-cell commitment switch in soft responsive hydrogels

Bulk matrix stiffness has emerged as a key mechanical cue in stem cell differentiation. Here, we show that the commitment and differentiation of human mesenchymal stem cells encapsulated in physiologically soft ( approximately 0.2-0.4 kPa), fully synthetic polyisocyanopeptide-based three-dimensional (3D) matrices that mimic the stiffness of adult stem cell niches and show biopolymer-like stress stiffening, can be readily switched from adipogenesis to osteogenesis by changing only the onset of stress stiffening. This mechanical behaviour can be tuned by simply altering the material's polymer length whilst maintaining stiffness and ligand density. Our findings introduce stress stiffening as an important parameter that governs stem cell fate in a 3D microenvironment, and reveal a correlation between the onset of stiffening and the expression of the microtubule-associated protein DCAMKL1, thus implicating DCAMKL1 in a stress-stiffening-mediated, mechanotransduction pathway that involves microtubule dynamics in stem cell osteogenesis