Journal of Biomedical Materials Research - Part A
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Effects of porosity and pore size on <i>in vitro</i> degradation of three‐dimensional porous poly(<scp>D</scp>,<scp>L</scp>‐lactide‐<i>co</i>‐glycolide) scaffolds for tissue engineering Abstract In vitro degradation of seven three‐dimensional porous scaffolds composed of PLGA85/15, a very useful poly(D ,L ‐lactide‐co ‐glycolide), was performed in phosphate‐buffered saline solution at 37°C up to 26 weeks, and effects of porosity (80–95%) and pore size (50–450 μm) on the degradation of the scaffolds were investigated. A series of quantities were measured during the degradation processes: molecular weight and its distribution of PLGA; compressive strength and modulus; and weight, dimension, and porosity of scaffolds. In all of cases with different pore morphologies, the degradation processes obeyed a three‐stage model. Scaffolds with a higher porosity or a smaller pore size degraded more slowly than and thus outlasted those with a lower porosity or a larger pore size. The effects are both attributed to a wall effect and a surface area effect because the scaffolds with lower porosities or larger pores possess thicker pore walls and smaller surface area, which depress the diffusion of acidic degradation products and thus results in a stronger acid‐catalyzed hydrolysis. This work suggests that, in designing a tissue‐engineering scaffold composed of PLGA and adjusting its degradation rate, the effects of pore morphologies should be taken into consideration in addition to those of chemical composition and condensed state of raw materials. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Journal of Biomedical Materials Research - Part A - Tập 75A Số 4 - Trang 767-777 - 2005
Wear mechanism and tribological characteristics of porous NiTi shape memory alloy for bone scaffold The abraded debris might cause osteocytic osteolysis on the interface between implants and bone tissues, thus inducing the subsequent mobilization of implants gradually and finally resulting in the failure of bone implants, which imposes restrictions on the applications of porous NiTi shape memory alloys (SMAs) scaffolds for bone tissue engineering. In this work, the effects of the annealing temperature, applied load, and porosity on the tribological behavior and wear resistance of three‐dimensional porous NiTi SMA are investigated systematically. The porous structure and phase transformation during the exothermic process affect the tribological properties and wear mechanism significantly. In general, a larger porosity leads to better tribological resistance but sometimes, SMAs with small porosity possess better wear resistance than ones with higher porosity during the initial sliding stage. It can be ascribed to the better superelasticity of the former at the test temperature. The porous NiTi phase during the exothermic reaction also plays an important role in the wear resistance. Generally, porous NiTi has smaller friction coefficients under high loads due to stress‐induced superelasticity. The wear mechanism is discussed based on plastic deformation and microcrack propagation. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 2586–2601, 2013.
Journal of Biomedical Materials Research - Part A - Tập 101A Số 9 - Trang 2586-2601 - 2013
Corneal bioprinting utilizing collagen‐based bioinks and primary human keratocytes Abstract Corneal transplantation is the treatment of choice for patients with advanced corneal diseases. However, the outcome may be affected by graft rejection, high associated costs, surgical expertise, and most importantly the worldwide donor shortage. In recent years, bioprinting has emerged as an alternative method for fabricating tissue equivalents using autologous cells with architecture resembling the native tissue. In this study, we propose a freeform and cell‐friendly drop‐on‐demand bioprinting strategy for creating corneal stromal 3D models as suitable implants. Corneal stromal keratocytes (CSK) were bioprinted in collagen‐based bioinks as 3D biomimetic models and the geometrical outcome as well as the functionality of the bioprinted specimens were evaluated after in vitro culture. We showed that our bioprinting method is feasible to fabricate translucent corneal stromal equivalents with optical properties similar to native corneal stromal tissue, as proved by optical coherence tomography. Moreover, the bioprinted CSK were viable after the bioprinting process and maintained their native keratocyte phenotypes after 7 days in in vitro culture, as shown by immunocytochemistry. The proposed bioprinted human 3D corneal models can potentially be used clinically for patients with corneal stromal diseases.
Journal of Biomedical Materials Research - Part A - Tập 107 Số 9 - Trang 1945-1953 - 2019
Evaluation of hydrogels for bio‐printing applications Abstract In the United States alone, there are approximately 500,000 burn injuries that require medical treatment every year. Limitations of current treatments necessitate the development of new methods that can be applied quicker, result in faster wound regeneration, and yield skin that is cosmetically similar to undamaged skin. The development of new hydrogel biomaterials and bioprinting deposition technologies has provided a platform to address this need. Herein we evaluated characteristics of twelve hydrogels to determine their suitability for bioprinting applications. We chose hydrogels that are either commercially available, or are commonly used for research purposes. We evaluated specific hydrogel properties relevant to bioprinting applications, specifically; gelation time, swelling or contraction, stability, biocompatibility and printability. Further, we described regulatory, commercial and financial aspects of each of the hydrogels. While many of the hydrogels screened may exhibit characteristics suitable for other applications, UV‐crosslinked Extracel, a hyaluronic acid‐based hydrogel, had many of the desired properties for our bioprinting application. Taken together with commercial availability, shelf life, potential for regulatory approval and ease of use, these materials hold the potential to be further developed into fast and effective wound healing treatments. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A:272–284, 2013.
Journal of Biomedical Materials Research - Part A - Tập 101A Số 1 - Trang 272-284 - 2013
Pore size and LbL chitosan coating influence mesenchymal stem cell<i>in vitro</i>fibrosis and biomineralization in 3D porous poly(epsilon-caprolactone) scaffolds
Journal of Biomedical Materials Research - Part A - Tập 103 Số 7 - Trang 2449-2459 - 2015
Three‐layered scaffolds for artificial esophagus using poly(ɛ‐caprolactone) nanofibers and silk fibroin: An experimental study in a rat model Abstract The purpose of this study was to determine the feasibility of an artificial esophagus using a three‐layered poly(ε‐caprolactone) (PCL)‐silk fibroin (SF) scaffold in a rat model. The artificial esophagus was a three‐layered, hybrid‐type prosthesis composed of an outer and inner layer of PCL with a middle layer of SF. After depositing the inner layer of the PCL scaffold by electrospinning, the lyophilized middle SF layer was created. The outer layer of PCL was produced following the same procedure used to make the inner PCL layer. Eleven rats were anesthetized using inhaled anesthesia. Circumferential defects of the cervical esophagus (n = 11) were created and reconstructed. Groups of rats were sacrificed after the 1st and 2nd weeks. Three rats died of an esophageal fistula and wound infection. No gross evidence of a fistula, perforation, abscess formation, seroma accumulation, or surrounding soft‐tissue necrosis was observed in the other rats sacrificed after the 1st and 2nd weeks. The artificial esophagus constructs produced complete healing of the circumferential defects by the 2nd week. The composition of the three‐layered artificial esophagus was confirmed histologically to have an outer and inner layer of PCL and a middle layer of SF. The fusion of the PCL‐SF scaffold and the regenerative tissue remained intact. Our study proposes a more practical experimental model for studying a three‐layered PCL‐SF scaffold in the esophagus. However, further studies on circumferential defect reconstruction in a rat model are still required. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2057–2065, 2015.
Journal of Biomedical Materials Research - Part A - Tập 103 Số 6 - Trang 2057-2065 - 2015
3D Bioprinting of heterogeneous aortic valve conduits with alginate/gelatin hydrogels Abstract Heart valve disease is a serious and growing public health problem for which prosthetic replacement is most commonly indicated. Current prosthetic devices are inadequate for younger adults and growing children. Tissue engineered living aortic valve conduits have potential for remodeling, regeneration, and growth, but fabricating natural anatomical complexity with cellular heterogeneity remain challenging. In the current study, we implement 3D bioprinting to fabricate living alginate/gelatin hydrogel valve conduits with anatomical architecture and direct incorporation of dual cell types in a regionally constrained manner. Encapsulated aortic root sinus smooth muscle cells (SMC) and aortic valve leaflet interstitial cells (VIC) were viable within alginate/gelatin hydrogel discs over 7 days in culture. Acellular 3D printed hydrogels exhibited reduced modulus, ultimate strength, and peak strain reducing slightly over 7‐day culture, while the tensile biomechanics of cell‐laden hydrogels were maintained. Aortic valve conduits were successfully bioprinted with direct encapsulation of SMC in the valve root and VIC in the leaflets. Both cell types were viable (81.4 ± 3.4% for SMC and 83.2 ± 4.0% for VIC) within 3D printed tissues. Encapsulated SMC expressed elevated alpha‐smooth muscle actin, while VIC expressed elevated vimentin. These results demonstrate that anatomically complex, heterogeneously encapsulated aortic valve hydrogel conduits can be fabricated with 3D bioprinting. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
Journal of Biomedical Materials Research - Part A - Tập 101A Số 5 - Trang 1255-1264 - 2013
Combinational effects of mechanical forces and substrate surface characteristics on esophageal epithelial differentiation Abstract Even the efficacy of substrate and mechanical stimuli in addition to biochemical cues have been recognized in many studies of stem cell differentiation, few studies have been reported on the differentiation into esophageal epithelial cells. Therefore, the aim of this study was set to propose a method of differentiating stem cells into esophageal epithelial cells according to biochemical reagent concentration, substrate properties, and mechanical forces. After the concentration of all‐trans retinoic acid was determined as 5 μM by a baseline experiment, the degree of differentiation was compared in three different kinds of substrates: cover glass, polyurethane (PU) membrane, and electrospun PU sheet (ePU). Then, on the substrate showing the more positive results, that is, ePU, two types of mechanical forces, intermittent hydrostatic pressure (IHP), and shear stress (SS), were applied individually at different magnitudes for the latter 7 days of an overall incubation period of 14 days. Following various biological assays, the lower IHP (50 mmHg) resulted in greater positive effects than the others. Even with cessation of the mechanical force, the relevant markers were remarkably increased. Although the range of factors regulating differentiation was limited, this study nonetheless demonstrated the combinational effects of mechanical force along with substrate type for the first time in related studies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 552–560, 2019.
Journal of Biomedical Materials Research - Part A - Tập 107 Số 3 - Trang 552-560 - 2019
Evaluation of alginate purification methods: Effect on polyphenol, endotoxin, and protein contamination Abstract Alginate, a polysaccharide extracted from brown seaweed, is widely used for the microencapsulation of islets of Langerhans, allowing their transplantation without immunosuppression. This natural polymer is known to be largely contaminated. The implantation of islets encapsulated using unpurified alginate leads to the development of fibrotic cell overgrowth around the microcapsules and normalization of the blood glucose is restricted to a very short period if it is achieved at all. Several research groups have developed their own purification method and obtained relatively good results. No comparative evaluation of the efficiencies of these methods has been published. We conducted an evaluative study of five different alginate preparations: a pharmaceutical‐grade alginate in its raw state, the same alginate after purification according to three different published methods, and a commercially available purified alginate. The results showed that all purification methods reduced the amounts of known contaminants, that is, polyphenols, endotoxins, and proteins, although with varying efficiencies. Increased viscosity of alginate solutions was observed after purification of the alginates. Despite a general efficiency in decreasing contamination levels, all of the purified alginates contained relatively high residual amounts of protein contaminants. Because proteins may be immunogenic, these residual proteins may have a role in persisting microcapsule immunogenicity. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Journal of Biomedical Materials Research - Part A - Tập 76A Số 2 - Trang 243-251 - 2006
Adhesive protein‐free synthetic hydrogels for retinal pigment epithelium cell culture with low ROS level Abstract Engineering of human retinal pigment epithelium (RPE) cell monolayer with low level of reactive oxygen species (ROS) is important for regenerative RPE‐based therapies. However, it is still challenging to culture RPE monolayer with low ROS level on soft substratesin vitro . To address this, we developed cytocompatible hydrogels to culture human RPE cell monolayer for future use in regenerative RPE‐based therapies. The cell adhesion, proliferation, monolayer formation, morphology, survival, and ROS level of human ARPE‐19 cells cultured on the surfaces of negatively charged poly (2‐acrylamido‐2‐methyl propane sulfonic sodium) (PNaAMPS) and neutral poly(N,N ‐dimethylacrylamide) (PDMAAm) hydrogels with different stiffness were investigated. The importance of hydrogel stiffness on the cell function was firstly highlighted on the base of determined optimal Young's modulus for cultivation of RPE cell monolayer with relatively low ROS level. The construction of RPE cell monolayer with low ROS level on the PNaAMPS hydrogel may hold great potential as promising candidates for transplantation of RPE cell monolayer‐hydrogel construct into the subretinal space to repair retinal functions. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2258–2267, 2014.
Journal of Biomedical Materials Research - Part A - Tập 102 Số 7 - Trang 2258-2267 - 2014
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