Browsing by Subject "Rheology"

Now showing 1 - 3 of 3
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    Injectable laminin-functionalized hydrogel for nucleus pulposus regeneration.
    (Biomaterials, 2013-10) Francisco, Aubrey T; Mancino, Robert J; Bowles, Robby D; Brunger, Jonathan M; Tainter, David M; Chen, Yi-Te; Richardson, William J; Guilak, Farshid; Setton, Lori A
    Cell delivery to the pathological intervertebral disc (IVD) has significant therapeutic potential for enhancing IVD regeneration. The development of injectable biomaterials that retain delivered cells, promote cell survival, and maintain or promote an NP cell phenotype in vivo remains a significant challenge. Previous studies have demonstrated NP cell - laminin interactions in the nucleus pulposus (NP) region of the IVD that promote cell attachment and biosynthesis. These findings suggest that incorporating laminin ligands into carriers for cell delivery may be beneficial for promoting NP cell survival and phenotype. Here, an injectable, laminin-111 functionalized poly(ethylene glycol) (PEG-LM111) hydrogel was developed as a biomaterial carrier for cell delivery to the IVD. We evaluated the mechanical properties of the PEG-LM111 hydrogel, and its ability to retain delivered cells in the IVD space. Gelation occurred in approximately 20 min without an initiator, with dynamic shear moduli in the range of 0.9-1.4 kPa. Primary NP cell retention in cultured IVD explants was significantly higher over 14 days when cells were delivered within a PEG-LM111 carrier, as compared to cells in liquid suspension. Together, these results suggest this injectable laminin-functionalized biomaterial may be an easy to use carrier for delivering cells to the IVD.
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    ItemOpen Access
    Micro-Viscoelastic Properties of the Human Conventional Outflow Pathway and Their Evolution in an Early Ocular-Hypertension Model.
    (2021) Shah, Tejank Pragnesh

    Primary OAG (POAG) is the second leading cause of irreversible blindness in the US and its prevalence is expected to worsen in the coming years. Major pathological changes have been attributed to the Juxtacanicular Tissue (JCT) and Inner Wall (IW) of Schlemm’s Canal (SC) within the human conventional outflow pathway. Biological tissues like the JCT/IW are viscoelastic in nature with both intra-cellular and extra-cellular mechanisms by which to store and dissipate applied forces. How these events contribute towards regulation of the local mechanobiology in the dynamic reciprocitybetween cells, their extracellular matrix (ECM), and in ultimately regulating outflow resistance, is poorly understood. Furthermore, the viscoelastic properties of the human trabecular meshwork (hTM) tissue are poorly understood. As a first step to develop more insight into the role of viscoelasticity, it was our goal to determine the localized dynamic mechanical properties of different regions of the hTM as a function of dexamethasone treatment. To explore the viscoelastic properties of the different tissue regions in the hTM comprising the hTM, we applied our co-located AFM-based rheometer/CLSM method to frontal sections of hTM under control and early ocular hypertensive conditions across a broad frequency range (1 Hz-1 kHz). We specifically considered the storage and loss moduli in the ocular pulse-relevant frequency range (1-10 Hz) and their changes across regions under dex treatment for two donors.

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    ItemOpen Access
    Transition dynamics and magic-number-like behavior of frictional granular clusters.
    (Phys Rev E Stat Nonlin Soft Matter Phys, 2012-07) Tordesillas, Antoinette; Walker, David M; Froyland, Gary; Zhang, Jie; Behringer, Robert P
    Force chains, the primary load-bearing structures in dense granular materials, rearrange in response to applied stresses and strains. These self-organized grain columns rely on contacts from weakly stressed grains for lateral support to maintain and find new stable states. However, the dynamics associated with the regulation of the topology of contacts and strong versus weak forces through such contacts remains unclear. This study of local self-organization of frictional particles in a deforming dense granular material exploits a transition matrix to quantify preferred conformations and the most likely conformational transitions. It reveals that favored cluster conformations reside in distinct stability states, reminiscent of "magic numbers" for molecular clusters. To support axial loads, force chains typically reside in more stable states of the stability landscape, preferring stabilizing trusslike, three-cycle contact triangular topologies with neighboring grains. The most likely conformational transitions during force chain failure by buckling correspond to rearrangements among, or loss of, contacts which break the three-cycle topology.