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INTRODUCTION: Cartilage degeneration and synovitis are key hallmarks of joint degenerative diseases, such as osteoarthritis (OA). The communication between these two tissues is fundamental to maintain both homeostasis and disease onset. However, studying this communication has remained challenging. Herein, we propose a novel modular precision microfluidic platform, that combines a synovial membrane-on-chip and a cartilage-on-chip platform. This seamless strategy enables the facile and in depth study of cross-communication between these two joint components, specificallyvia inflammatory mediators, aiming to replicate the onset of OA. METHODS: Two types of microfluidic PDMS-based chips were designed with actuation chambers to emulate the mechanical forces of the cartilage and synovial membrane. For the cartilage chip, human healthy and OA affected chondrocytes were seeded in an ECM-like hydrogel. The synovial membrane chip was composed of a hydrogel re-enforced by an elastic membrane, which was seeded with synovium fibroblasts. Both chips were connected by a common channel, where synovium mimicking medium (culture medium supplemented with HA) was flowing (60 μl/hr). After both tissues achieved phenotypical maturation, human macrophages were added to the system. The behavior of the immune cells were a key read-out, focusing on their mobility, cytokine and proteinase release profile (ELISA) and polarization ratio between M1 and M2 (qPCR). On-line and end-pointanalysis were conducted after 1, 3 and 7 days. RESULTS & DISCUSSION: The unique chip actuator designs allowed for physiologically relevant stimulation of the cartilage and synovial membrane, by cyclic compression and stretching, respectively. The effect of the mechanical load was determined on the release of inflammatory mediators. The proteinases and inflammatory cytokine profiles are the basis of the fingerprint of the influence of the variables: static vs. mechanically stimulated, healthy vs. OA-affected chondrocytes,and, presence vs. absence of macrophages. CONCLUSIONS: This modular joint-on-chip platform has the potential to provide unprecedented insights in the effects of inflammation of a single joint tissue, the performance of the various joint tissues, and the joint function itself.

Here, we present a cartilage-on-chip platform comprising an innovative multi-modal actuation unit to subject chondrocyte-laden hydrogel to both compression and shear strain. The response of human chondrocytes to both healthy and pathophysiological mechanical stimulation is evaluated.

INTRODUCTION: Native tissues are characterized by a dynamic nature. Recapitulating such dynamicity in engineered tissues requires spatiotemporal control over their biochemical composition. Here, we pioneered supramolecular desthiobiotin/avidin complexation to enable dynamic functionalization of biomaterials. Desthiobiotin is a non-sulfur containing analog of biotin that also interacts with avidin, but with substantially lower binding affinity than biotin [1]. We hypothesized that combining biotinylated hydrogel with desthiobiotinylated bioactive molecules would enable the spatiotemporal functionalization of biomaterials via in situ desthiobiotin/biotin displacement, which is a novel, facile, and fully cytocompatible material modification strategy. METHODS: Biotinylated dextran-based (Dex-TA) hydrogel constructs were functionalized with 1μM neutravidin (i.e., avidin analog), 1μM desthiobiotin-FITC (D-FITC) and 1μM biotin-atto565 (B-atto565), and subsequently analyzed using fluorescence recovery after photobleaching (FRAP) and confocal microscopy. Surface plasmon resonance imaging (SPRi) and reporter cells were used to analyze the reversible presentation and bioactivity of desthiobiotinylated BMP7 antibodies and BMP7 growth factors. RESULTS & DISCUSSION: The reversible and sequential modification of the hydrogel constructs was demonstrated by displacing D-FITC with B-atto565. By tuning the concentration and incubation time of B-atto565, we reproducibly controlled its penetration depth into the hydrogel. An injectionmolded bone-shaped 3D construct was spatially modified by controlling the thickness of the biotindisplaced layer. Moreover, competitive supramolecular complexation enabled the temporal presentation of desthiobiotinylated BMP7 antibodies and growth factors, as confirmed using SPRi and reporter cells. CONCLUSIONS: We have successfully developed and characterized a novel spatiotemporal biomaterial modification strategy based on competitive supramolecular complexation.

In het kader van het gezamenlijke programma Strategy & Change hebben TNO en het Den Haag Centrum voor Strategische Studies (HCSS) zich samen met SER-Brabant de vraag gesteld wat de belangrijkste motoren voor Innovatie in Brabant zijn en hoe deze kunnen worden verterkt. Voor het inslaan van nieuwe wegen is het van belang te onderkennen dat innovatie van producten, diensten en processen meer dan ooit het bij elkaar brengen van uiteenlopende kennis en ervaring, productiefaciliteiten en financiële en andere diensten eist.

Purpose: We recently developed a novel injectable in situ crosslinkable Dextran-Tyramine 14kDa-DS=15 (Dex-TA) hydrogel, which has shown high potential for cartilage regeneration. However, cartilage repair strategies based on autologous chondrocyte implantation still rely on in vitro expansion to obtain sufficient cells with all inherent drawbacks such as dedifferentiation. Cartilage repair using mixtures of a limited number of chondrocytes with Mesenchymal Stem Cells (MSCs) can potentially overcome this hurdle. It remains unclear whether the hydrogels should be seeded with single-cell suspension or with preformed microaggregates of defined size. To test, this we have seeded hydrogels with microaggregates of chondrocytes, MSCs or a mixture of both and compared their performance with single-cell seeded hydrogels. Methods and Materials: High throughput formation of microaggregates of 50, 100 and 200 cells was achieved in micromolds. Microaggregates were prepared of chondrocytes, MSCs or a mixture of both. Morphology, stability and chondrogenic capacity was evaluated. Aggregates with the optimal cell density of 100 cells were incorporated into Dex-TA hydrogels, cultured in vitro and in vivo and compared to single-cell seeded hydrogels. Results: Micro-aggregates were formed in a very controlled manner and successfully incorporated into Dex-TA hydrogels. Aggregates formed by 100 cells showed a superior balance between stability and gene expression profile, with higher collagen type2 and Aggrecan expression. After incorporation of micro-aggregates into Dex-TA, long term stability and survival was observed, as well as enhanced matrix production, when compared to single-cell seeded hydrogels. More cartilage was formed in micro-aggregates consisting of a 50%/50% mixture of chondrocytes and MSCs, compared to both micro-aggregates of pure cell populations and to single-cell mixtures. Conclusions: We conclude that neocartilage formation is greatly improved by seeding hydrogels with micro-aggregates instead of single-cell suspensions. In addition, this system provided preliminary information about the effect of micro-cocultures, showing enhancement of neocartilage formation when using 50% chondrocytes mixed with 50% MSCs.

De Breinwerker, onder redactie van Iris Bakker, is een exclusief boekwerk dat tot stand is gekomen tijdens haar promotieonderzoek aan de TU Delft naar de productieve werkomgeving. De publicatie is samengesteld met de hulp van een aantal deskundigen die gezamenlijk een beeld van de productieve werkomgeving geven. Het eerste deel zoomt in op de mens. In het tweede deel staat de omgeving centraal. Veel kleurenfoto’s en een frisse vormgeving nodigen uit tot een boeiende wandeling door de productieve omgeving in boekvorm

Modular tissue engineering enables the formation of larger 3D multiscale tissues by assembly of building blocks composed of cells and/or (micro)materials. However, current tissue building blocks are static, thereby limiting the functionality of modular tissues. In this study, an advanced droplet microfluidics system is used to produce microgels that are optimized to act as smart tissue building blocks. The cell-sized microgels are functionalized with reactive moieties that allow for the microgels' in situ chemical and mechanical tuning, thereby providing spatiotemporal control over living modular tissues.