An organoid is a 3D organization of cells that can recapitulate some of the structure and function of native tissue. Recent work has seen organoids gain prominence as a valuable model for studying ...tissue development, drug discovery, and potential clinical applications. The requirements for the successful culture of organoids in vitro differ significantly from those of traditional monolayer cell cultures. The generation and maturation of high-fidelity organoids entails developing and optimizing environmental conditions to provide the optimal cues for growth and 3D maturation, such as oxygenation, mechanical and fluidic activation, nutrition gradients, etc. To this end, we discuss the four main categories of bioreactors used for organoid culture: stirred bioreactors (SBR), microfluidic bioreactors (MFB), rotating wall vessels (RWV), and electrically stimulating (ES) bioreactors. We aim to lay out the state-of-the-art of both commercial and in-house developed bioreactor systems, their benefits to the culture of organoids derived from various cells and tissues, and the limitations of bioreactor technology, including sterilization, accessibility, and suitability and ease of use for long-term culture. Finally, we discuss future directions for improvements to existing bioreactor technology and how they may be used to enhance organoid culture for specific applications.
Electrospinning is an increasingly popular technique to generate 3D fibrous tissue scaffolds that mimic the submicron sized fibers of extracellular matrices. A major drawback of electrospun scaffolds ...is the small interfibrillar pore size, which normally prevents cellular penetration in between fibers. In this study, we introduced a novel process, based on electrospinning, to manufacture a unique gradient porous fibrous (GPF) scaffold from soy protein isolate (SPI). The pore sizes in the GPF scaffolds gradually increase from one side of the scaffold to the other, ranging from 7.8 ± 2.5 μm in the small pore side, 21.4 ± 10.3 μm in the mid layer to 58.0 ± 23.6 μm in the large pore side. The smallest pores of the GPF scaffolds appeared to be somewhat larger than those in conventionally electrospun SPI scaffolds (4.2 ± 1.3 μm). Hydrated GPF scaffolds exhibited J-shaped stress-strain curves, reminiscent of those for soft biological scaffolds. Attachment, spreading, and proliferation of human dermal fibroblasts (HDFB) were supported on both the small and the large pore sides of the GPF scaffolds. Cultured HDFB and murine RAW 264.7 macrophages penetrated significantly deeper (98.7 ± 24.2 μm and 53.3 ± 9.6 μm, respectively) into the larger pores than when seeded onto the small pore side of GPF scaffolds (22.8 ± 6.2 μm and 25.7 ± 7.3 μm) and control SPI scaffolds. (11.3 ± 3.8 μm and 15.3 ± 3.1 μm). This study introduces a novel fabrication technique, which, by convergence of several biofabrication technologies, produces scaffolds with enhanced cellular penetration.
Custom prostheses could be used to recreate the ossicular chain and improve hearing.
Ossicular discontinuity or fixation occurs in 55% of cases of conductive hearing loss, with most cases involving ...the incus. Reconstruction has been achieved by a variety of methods; however, there has been little improvement in hearing outcomes in decades.
Precise measurements of anatomic dimensions, weight, and center of gravity were taken from 19 cadaveric incudes. These measurements were combined with measurements from the medical literature and micro-computed tomography (micro-CT) of cadaveric temporal bones to generate a rasterizable incus model. As a proof of concept, incudal replacements including possible anatomic variations were then three-dimensionally (3-D) printed and inserted into a cadaveric temporal bone.
Our measurements of cadaveric incudes corresponded well with those from the medical literature. These measurements were combined with anatomical information from micro-CT allowing identification of critical features of the incus, which remained constant. Other model features were modified to increase stability and facilitate synthesis, including broadening and thickening of the lenticular process and the incudomalleolar articulation. 3-D printed incudal replacements based on this model readily fit into a cadaveric temporal bone and successfully bridged the gap between malleus and incus.
We have generated a model for custom 3-D synthesis of incudal prostheses. While current 3-D printing in biocompatible materials at the size required is limited, the technology is rapidly advancing, and 3-D printing of incudal replacements with polylactic acid (PLA) is of the correct size and shape.
In this study we describe the use of an electrospun soy protein-based tissue scaffold (SPS) as a bioactive wound dressing in a pig model of full thickness excisional wound healing. The time course of ...wound healing and the quality of the healing tissue were evaluated using histology (H&E and Masson's trichrome staining). While the overall rate of wound closure was similar in the SPS-treated vs. untreated control wounds covered with Tegaderm®, there were significant qualitative differences between the two groups. Two weeks after a single application of SPS at the time of wounding, the SPS treated wounds showed robust signs of reepithelialization, which was absent in the control wounds. After 4 weeks, the SPS treated wounds contained a stratified epithelial layer in the epidermis that looked essentially normal, while the connective tissue in the dermis was attaining a cellular, organized appearance. By contrast the nascent epidermis of the untreated controls appeared immature, while the dermis was still replete with numerous inflammatory/immune cells. Masson's trichrome staining confirmed the increased presence of collagen in the dermis of the SPS treated wounds at 4 weeks, while the control wounds were largely devoid of collagen. Finally, in addition to enhanced reepithelialization and dermal tissue regeneration, 4 weeks after application of the SPS dressing, we observed the presence of dermal appendages, such as sweat glands and hair follicles. No such appendage formation was observed in the untreated controls during the entire duration of our study. Taken together, the histological data clearly indicate that our soy protein based scaffolds accelerated and enhanced a more natural mode of tissue regeneration in the porcine model of full thickness excisional wound healing. Given the similarities between porcine and human wound healing, we anticipate that SPS will also be advantageous in clinical applications.
Liposome-based chemical exchange saturation transfer (lipoCEST) agents have shown great sensitivity and potential for molecular magnetic resonance imaging (MRI). Here we demonstrate that the size of ...liposomes can be exploited to enhance the lipoCEST contrast. A concise analytical model is developed to describe the contrast dependence on size for an ensemble of liposomes. The model attributes the increased lipoCEST contrast in smaller liposomes to their larger surface-to-volume ratio, causing an increased membrane water exchange rate. Experimentally measured rates correlate with size, in agreement with the model. The water permeability of liposomal membrane is found to be 1.11 +/- 0.14 microm/s for the specific lipid composition at 22 degrees C. Availability of the model allows rational design of the size of liposomes and quantification of their properties. These new theoretical and experimental tools are expected to benefit applications of liposomes to sensing the cellular environment, targeting and imaging biological processes, and optimizing drug delivery properties.
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