Browsing by Author "Grigoryan, Bagrat"
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Item Advanced Stereolithography for Translational Vascular 3D Bioprinting(2019-04-19) Grigoryan, Bagrat; Miller, Jordan SThe field of tissue engineering aims to fulfill the great clinical need to repair, replace, or regenerate impaired tissues and organs by delivery of a combination of cells, biomaterials, and biochemical and physicochemical factors. Indeed, tremendous strides have been achieved over the past several decades to construct implantable avascularized constructs such as skin, cornea, and bladder towards treatment for diseases and/or injuries. However, obtaining functional, physiologically relevant tissues is still a major challenge in the field due to the necessity of a vasculature system to supply nutrients and remove waste in thick constructs. This challenge can be attributed to convective transport limitations which results in necrotic cells due to inadequate access to nutrients. Indeed, vascularization of engineered thick tissue constructs is the current impediment in tissue engineering. Additionally, lack of the ability to recreate the heterogeneous patterns of cells and matrix to obtain constructs with controlled shape and architectures has further hindered progress towards organ replacement. This thesis aims to address these limitations by developing, characterizing, and validating a light-based 3D printing platform towards realization of thick, functional tissue constructs containing physiologically relevant micro-architectures. Of key importance towards achieving this goal, novel photopolymerizable formulations were identified and demonstrated towards stereolithographic generation of thick, perfusable hydrogels. Our hardware and materials innovations were then applied towards generation of hydrogels (composed of ≥90% water) containing various unprecedented space-filling, interpenetrating vessel networks, a hallmark of advanced multicellular life. We demonstrated a plethora of biological utility of our approach by illustrating examples of intervascular interstitial transport, generation of viable and functioning in vitro models of lung and bone tissue, and construction of a therapeutic transplantation liver model. This work unlocks transformative opportunities to mimic, interrogate, and utilize intricate multivariate vascular architectures that are vital to advanced multicellular life.Item Development, characterization, and applications of multi-material stereolithography bioprinting(Springer Nature, 2021) Grigoryan, Bagrat; Sazer, Daniel W.; Avila, Amanda; Albritton, Jacob L.; Padhye, Aparna; Ta, Anderson H.; Greenfield, Paul T.; Gibbons, Don L.; Miller, Jordan S.As a 3D bioprinting technique, hydrogel stereolithography has historically been limited in its ability to capture the spatial heterogeneity that permeates mammalian tissues and dictates structure–function relationships. This limitation stems directly from the difficulty of preventing unwanted material mixing when switching between different liquid bioinks. Accordingly, we present the development, characterization, and application of a multi-material stereolithography bioprinter that provides controlled material selection, yields precise regional feature alignment, and minimizes bioink mixing. Fluorescent tracers were first used to highlight the broad design freedoms afforded by this fabrication strategy, complemented by morphometric image analysis to validate architectural fidelity. To evaluate the bioactivity of printed gels, 344SQ lung adenocarcinoma cells were printed in a 3D core/shell architecture. These cells exhibited native phenotypic behavior as evidenced by apparent proliferation and formation of spherical multicellular aggregates. Cells were also printed as pre-formed multicellular aggregates, which appropriately developed invasive protrusions in response to hTGF-β1. Finally, we constructed a simplified model of intratumoral heterogeneity with two separate sub-populations of 344SQ cells, which together grew over 14 days to form a dense regional interface. Together, these studies highlight the potential of multi-material stereolithography to probe heterotypic interactions between distinct cell types in tissue-specific microenvironments.Item Hypothermic 3D bioprinting of living tissues supported by perfusable vasculature(2022-06-28) Miller, Jordan; Ta, Anderson; Grigoryan, Bagrat; Rice University; William Marsh Rice University; United States Patent and Trademark OfficeThe present application is a divisional application of U.S. application Ser. No. 15/709,392, filed Sep. 19, 2017, which is a continuation application of International Application No. PCT/US16/23302, filed Mar. 18, 2016, which claims priority to U.S. Provisional Application No. 62/136,004, filed on Mar. 20, 2015, the contents of which are incorporated herein by reference.Item Hypothermic 3D bioprinting of living tissues supported by perfusable vasculature(2020-11-24) Miller, Jordan; Ta, Anderson; Grigoryan, Bagrat; Rice University; United States Patent and Trademark OfficeThe present disclosure provides compositions and methods for producing hydrogel matrix constructs. Methods of using hydrogel matrix constructs for tissue repair and regeneration and for the oxygenation of red blood cells are also disclosed.Item Hypothermic 3D bioprinting of living tissues supported by perfusable vasculature(2022-09-20) Miller, Jordan; Ta, Anderson; Grigoryan, Bagrat; Rice University; William Marsh Rice University; United States Patent and Trademark OfficeThe present disclosure provides compositions and methods for producing hydrogel matrix constructs. Methods of using hydrogel matrix constructs for tissue repair and regeneration and for the oxygenation of red blood cells are also disclosed.Item Hypothermic 3D bioprinting of living tissues supported by perfusable vasculature(2024-05-07) Miller, Jordan; Ta, Anderson; Grigoryan, Bagrat; Rice University; United States Patent and Trademark OfficeThe present disclosure provides compositions and methods for producing hydrogel matrix constructs. Methods of using hydrogel matrix constructs for tissue repair and regeneration and for the oxygenation of red blood cells are also disclosed.Item Projection-based stereolithography for direct 3D printing of heterogeneous ultrasound phantoms(Public Library of Science, 2021) Paulsen, Samantha J.; Mitcham, Trevor M.; Pan, Charlene S.; Long, James; Grigoryan, Bagrat; Sazer, Daniel W.; Harlan, Collin J.; Janson, Kevin D.; Pagel, Mark D.; Miller, Jordan S.; Bouchard, Richard R.Modern ultrasound (US) imaging is increasing its clinical impact, particularly with the introduction of US-based quantitative imaging biomarkers. Continued development and validation of such novel imaging approaches requires imaging phantoms that recapitulate the underlying anatomy and pathology of interest. However, current US phantom designs are generally too simplistic to emulate the structure and variability of the human body. Therefore, there is a need to create a platform that is capable of generating well-characterized phantoms that can mimic the basic anatomical, functional, and mechanical properties of native tissues and pathologies. Using a 3D-printing technique based on stereolithography, we fabricated US phantoms using soft materials in a single fabrication session, without the need for material casting or back-filling. With this technique, we induced variable levels of stable US backscatter in our printed materials in anatomically relevant 3D patterns. Additionally, we controlled phantom stiffness from 7 to >120 kPa at the voxel level to generate isotropic and anisotropic phantoms for elasticity imaging. Lastly, we demonstrated the fabrication of channels with diameters as small as 60 micrometers and with complex geometry (e.g., tortuosity) capable of supporting blood-mimicking fluid flow. Collectively, these results show that projection-based stereolithography allows for customizable fabrication of complex US phantoms.Item Remodeling of ECM patch into functional myocardium in an ovine model: A pilot study(Wiley, 2015) Scully, Brandi B.; Fan, Chris; Grigoryan, Bagrat; Jacot, Jeffrey G.; Vick, G. Wesley III; Kim, Jeffrey J.; Fraser, Charles D.; Grande-Allen, K. Jane; Morales, David L.S.Background: Previous studies have demonstrated that surgical patches comprised of small intestinal submucosa-derived extracellular matrix (ECM) have biological remodeling potential. This pilot study investigated histological, mechanical, and bioelectrical properties of an ECM patch implanted in the ovine right-ventricular outflow tract (RVOT). Materials and Methods: ECM patches (2 × 2 cm2) were implanted in four Western Range sheep (wether males, 37–49 kg, age <1 year) and explanted at 5 months (n = 2) and 8 months (n = 2). In vivo analysis included epicardial echocardiography and contact electrical mapping. Optical mapping was used to map electrical activity of two hearts on a Langendorff preparation. Mechanical testing quantified stiffness. Histological stains characterized structure, neovascularization, and calcification; immunohistochemistry (IHC) assessed cell phenotype. Results: In vivo analysis showed that ECM patch tissue was contractile by M-mode and two-dimensional echocardiographic evaluation. In vivo electrical mapping, and optical mapping confirmed that ECM conducted an organized electrical signal. Mechanical testing of native and ECM patched RVOT tissue showed an elastic modulus of the implanted patch comparable to native tissue stiffness. Conclusions: At 5 and 8 months, the ECM had undergone extracellular matrix remodeling and neovascularization without calcification. The ECM was populated with locally aligned muscle cells positive for sarcomeric alpha-actinin, CD45, and troponin I and T. In sheep, the ECM patch appears to have the potential of remodeling to resemble native, functional ventricular tissue as evidenced by histological, mechanical, and electrical properties.Item Thermofluidic heat exchangers for actuation of transcription in artificial tissues(AAAS, 2020) Corbett, Daniel C.; Fabyan, Wesley B.; Grigoryan, Bagrat; O'Connor, Colleen E.; Johansson, Fredrik; Batalov, Ivan; Regier, Mary C.; DeForest, Cole A.; Miller, Jordan S.; Stevens, Kelly R.Spatial patterns of gene expression in living organisms orchestrate cell decisions in development, homeostasis, and disease. However, most methods for reconstructing gene patterning in 3D cell culture and artificial tissues are restricted by patterning depth and scale. We introduce a depth- and scale-flexible method to direct volumetric gene expression patterning in 3D artificial tissues, which we call “heat exchangers for actuation of transcription” (HEAT). This approach leverages fluid-based heat transfer from printed networks in the tissues to activate heat-inducible transgenes expressed by embedded cells. We show that gene expression patterning can be tuned both spatially and dynamically by varying channel network architecture, fluid temperature, fluid flow direction, and stimulation timing in a user-defined manner and maintained in vivo. We apply this approach to activate the 3D positional expression of Wnt ligands and Wnt/β-catenin pathway regulators, which are major regulators of development, homeostasis, regeneration, and cancer throughout the animal kingdom.