혈관대체체용 Polyurethane 지지체의 Compliance Property 향상을 위한 연구(I) Improved Compliance of Polyurethane Scaffold for Vascular Graft Application: Preliminary Study

In this study, we prepared solvent casting polyurethane films (sPU) and electrospun polyurethane films (ePU) to compare their compliance for providing better mechanical properties for vascular graft replacement. Mechanical properties of the prepared specimens showed that Young's modulus of each specimen was 0.037 N/m2 (ePU) and 0.035 N/m2(sPU). Deformation energy of ePU and sPU specimens were 0.00098600 (J) and 0.0020706 (J), respectively, and porcine's aorta was 0.00034845 (J). The ePU specimen showed closer value to that of porcine's aorta than that of sPU specimen's. That means the compliance of the ePU revealed closer value to the compliance of the porcine's aorta than that of the sPU specimen. For surface property of the specimens, the contact angle of the ePU (57.39° ± 1.84) was more hydrophilic than that of sPU (64.73° ± 1.56). However, human umbilical vein endothelial cells (HUVECs) attachment and proliferation tests showed better attachment and proliferation (more than 20%) for the sPU specmen rather than the ePU specimen. Conclusively, the PU film made by nano fiber can provide better compliance property but cytocompatibility was somewhat behind compared to solvent cast PU film.ope

Activated carbon nanofiber nanoparticles incorporated electrospun polycaprolactone scaffolds to promote fibroblast behaviors for application to skin tissue engineering

The most widely used one-dimensional (1D) carbonaceous nanomaterials in tissue engineering are carbon nanotubes, either single or multiwalled. Other forms of 1D nanomaterials, such as carbon nanowires and carbon nanofibers, have been less explored for biomedical applications. Herein, we synthesized 1D-activated carbon nanofiber nanoparticles (ACNF NPs) from the polyacrylonitrile electrospun nanofibers by continuous processes like stabilization, alkali treatment, calcination, and grinding. Two different sets of ACNF NPs-containing electrospun polycaprolactone (PCL) nanofiber mats, viz. surface-modified NP-deposited mats (ACNF@PCL) and NP-incorporated mats (ACNF-PCL), were prepared to examine their potential as skin tissue engineering scaffolds. Raman spectra demonstrated that ACNF NPs exhibited graphitization degree with an I-D/I-G ratio of 1.05. Scanning electron microscopy (SEM) observations showed that ACNF NPs are sized 280 +/- 100 nm by diameter and 565-3322 nm by length. The NPs concentrated above 30 mu g/mL were found to exhibit toxicity with < 70% viability of NIH3T3 fibroblasts on 48 h. The ACNF-PCL nanofiber mats displayed better cell proliferation profile showing significant changes compared to PCL and ACNF@PCL mats on days 1, 3, and 5. Hence, we concluded that ACNF-PCL mats with less concentration of ACNF NPs have more potential to support cellular growth, ensuring its possible impact on skin tissue regeneration.ope

Design, fabrication, and structural safety validation of 3D-printable biporous bone augments

The use of commercial products such as a cup and liner for total hip arthroplasty for patients with severe bone defects has a high probability of failure. In these patients the cup alone cannot cover the bone defect, and thus, an additional augment or cage is required. In this study, we designed three-dimensional (3D) printable bone augments as an alternative to surgeries using reinforcement cages. Thirty-five sharp-edged bone augments of various sizes were 3D printed. A biporous structure was designed to reduce the weight of the augment and to facilitate bone ingrowth. Two types of frames were used to prevent damage to the augment’s porous structure and maintain its stability during printing. Furthermore, two types of holes were provided for easy augment fixation at various angles. Fatigue tests were performed on a combination of worst-case sizes derived using finite element analysis. The test results confirmed the structural stability of the specimens at a load of 5340 N. Although the porosity of the specimens was measured to be 63.70%, it cannot be said that the porous nature was uniformly distributed because porosity tests were performed locally and randomly. In summary, 3D-printable biporous bone augments capable of bonding from various angles and bidirectionally through angulation and bottom-plane screw holes are proposed. The mechanical results with bone augments indicate good structural safety in patients. However, further research is necessary to study the clinical applications of the proposed bone augment.ope

Shape suitability and mechanical safety of customised hip implants: Three-dimensional printed acetabular cup for hip arthroplasty

Background: Owing to an increase in the number of hip arthroplasty surgeries, the number of implant replacement surgeries is increasing rapidly as well. This necessitates the study of hip joint conditions. Therefore, Paprosky defined a classification system to indicate the degree of damage to the hip joint. In this study, a customised hip implant suitable for Paprosky classification Type ⅡC and over was designed. The shape, suitability, and mechanical safety of the worst-case model for the implant were evaluated. Materials and methods: To identify the implant size depending on states over Type ⅡC acetabulum bone loss, a size range was selected and a customised implant was designed according to the computed tomography data within the size range. The implant was designed for the flange, hook, and flattened model types. The worst-case selection test was conducted using finite element analysis. The von Mises stresses of the flange, hook, and flattened models were found as 76.223, 136.99, and 80.791 MPa, respectively. Therefore, the hook-type model was selected as the worst case for the mechanical performance test. Results: A bending test was conducted on the hook-type model without fracture and failure at 5344.56 N. The proposed customised implant was found suitable for Type ⅢA acetabulum bone loss, whereas the shape suitability and mechanical safety were verified for the worst case. Conclusion: The shape of a customised implant suitable for Paprosky ⅢA type was designed. The shape suitability and mechanical safety were evaluated using finite element method analysis and bending tests. Clinical validation is required through subsequent clinical evaluation.ope

Stimulating effect of graphene oxide on myogenesis of C2C12 myoblasts on RGD peptide-decorated PLGA nanofiber matrices

BACKGROUND: In the field of biomedical engineering, many studies have focused on the possible applications of graphene and related nanomaterials due to their potential for use as scaffolds, coating materials and delivery carriers. On the other hand, electrospun nanofiber matrices composed of diverse biocompatible polymers have attracted tremendous attention for tissue engineering and regenerative medicine. However, their combination is intriguing and still challenging. RESULTS: In the present study, we fabricated nanofiber matrices composed of M13 bacteriophage with RGD peptide displayed on its surface (RGD-M13 phage) and poly(lactic-co-glycolic acid, PLGA) and characterized their physicochemical properties. In addition, the effect of graphene oxide (GO) on the cellular behaviors of C2C12 myoblasts, which were cultured on PLGA decorated with RGD-M13 phage (RGD/PLGA) nanofiber matrices, was investigated. Our results revealed that the RGD/PLGA nanofiber matrices have suitable physicochemical properties as a tissue engineering scaffold and the growth of C2C12 myoblasts were significantly enhanced on the matrices. Moreover, the myogenic differentiation of C2C12 myoblasts was substantially stimulated when they were cultured on the RGD/PLGA matrices in the presence of GO. CONCLUSION: In conclusion, these findings propose that the combination of RGD/PLGA nanofiber matrices and GO can be used as a promising strategy for skeletal tissue engineering and regeneration.ope

The Effect of Poly(lactic-co-glycolic acid)/Hydroxyapatite Composite Scaffold on Chondrocyte Cyto-compatibility (II)

The effect of PLGA/HA composite material on cellular adhesion and proliferation was investigated. The composite film was prepared by poly(D,L-lactic-co-glycolic acid) (PLGA) and hydroxyapatite (HA). The PLGA was used as matrix mate- rial and the HA particles were incorporated as reinforcing material. The HA particles were mixed in 5, 10 and 15 wt% with PLGA for preparing PLGA/HA composite film and scaffold. Mechanical property of the composite film was char- acterized by tensile test. The ultimate tensile strength of 10 wt% HA content film was two-fold higher than control group. Surface of the composite films and scaffolds were characterized by contact angle measurement and scanning electron microscope (SEM). The PLGA/HA composites were more hydrophilic than control group. The SEM picture showed that the pores in the PLGA/HA composite scaffold were clearly observed as the pores in the PLGA scaffold (control). For the PLGA/HA composite scaffold, compression test was performed. The compressive stress was decreased with increasing the amount of HA. This is the same phenomenon as the tensile test for composite film. For cell-com- patibility, cellular attachment and proliferation were significantly higher on PLGA/HA (10 wt%) composite film than control group (1.5 times higher in attachment test and 1.3 times higher for 6th -day culture in proliferation assaying, p<0.05). However, the PLGA/HA (10wt%) composite scaffold showed not as good result as the film has. For 3-D scaf- fold structure, it is presumed that other geometrical factors may important role in cellular adhesion and proliferation.ope

PLGA nanofiber membranes loaded with epigallocatechin-3-O-gallate are beneficial to prevention of postsurgical adhesions.

This study concentrates on the development of biodegradable nanofiber membranes with controlled drug release to ensure reduced tissue adhesion and accelerated healing. Nanofibers of poly(lactic-co-glycolic acid) (PLGA) loaded with epigallocatechin-3-O-gallate (EGCG), the most bioactive polyphenolic compound in green tea, were electrospun. The physicochemical and biomechanical properties of EGCG-releasing PLGA (E-PLGA) nanofiber membranes were characterized by atomic force microscopy, EGCG release and degradation profiles, and tensile testing. In vitro antioxidant activity and hemocompatibility were evaluated by measuring scavenged reactive oxygen species levels and activated partial thromboplastin time, respectively. In vivo antiadhesion efficacy was examined on the rat peritonea with a surgical incision. The average fiber diameter of E-PLGA membranes was approximately 300-500 nm, which was almost similar to that of pure PLGA equivalents. E-PLGA membranes showed sustained EGCG release mediated by controlled diffusion and PLGA degradation over 28 days. EGCG did not adversely affect the tensile strength of PLGA membranes, whereas it significantly decreased the elastic modulus and increased the strain at break. E-PLGA membranes were significantly effective in both scavenging reactive oxygen species and extending activated partial thromboplastin time. Macroscopic observation after 1 week of surgical treatment revealed that the antiadhesion efficacy of E-PLGA nanofiber membranes was significantly superior to those of untreated controls and pure PLGA equivalents, which was comparable to that of a commercial tissue-adhesion barrier. In conclusion, the E-PLGA hybrid nanofiber can be exploited to craft strategies for the prevention of postsurgical adhesions.ope

Coculture of Primary Motor Neurons and Schwann Cells as a Model for In Vitro Myelination

A culture system that can recapitulate myelination in vitro will not only help us better understand the mechanism of myelination and demyelination, but also find out possible therapeutic interventions for treating demyelinating diseases. Here, we introduce a simple and reproducible myelination culture system using mouse motor neurons (MNs) and Schwann cells (SCs). Dissociated motor neurons are plated on a feeder layer of SCs, which interact with and wrap around the axons of MNs as they differentiate in culture. In our MN-SC coculture system, MNs survived over 3 weeks and extended long axons. Both viability and axon growth of MNs in the coculture were markedly enhanced as compared to those of MN monoculture. Co-labeling of myelin basic proteins (MBPs) and neuronal microtubules revealed that SC formed myelin sheaths by wrapping around the axons of MNs. Furthermore, using the coculture system we found that treatment of an antioxidant substance coenzyme Q10 (Co-Q10) markedly facilitated myelination.ope

Multiphoton imaging of myogenic differentiation in gelatin-based hydrogels as tissue engineering scaffolds

BACKGROUND: Hydrogels can serve as three-dimensional (3D) scaffolds for cell culture and be readily injected into the body. Recent advances in the image technology for 3D scaffolds like hydrogels have attracted considerable attention to overcome the drawbacks of ordinary imaging technologies such as optical and fluorescence microscopy. Multiphoton microscopy (MPM) is an effective method based on the excitation of two-photons. In the present study, C2C12 myoblasts differentiated in 3D gelatin hydroxyphenylpropionic acid (GHPA) hydrogels were imaged by using a custom-built multiphoton excitation fluorescence microscopy to compare the difference in the imaging capacity between conventional microscopy and MPM. RESULTS: The physicochemical properties of GHPA hydrogels were characterized by using scanning electron microscopy and Fourier-transform infrared spectroscopy. In addition, the cell viability and proliferation of C2C12 myoblasts cultured in the GHPA hydrogels were analyzed by using Live/Dead Cell and CCK-8 assays, respectively. It was found that C2C12 cells were well grown and normally proliferated in the hydrogels. Furthermore, the hydrogels were shown to be suitable to facilitate the myogenic differentiation of C2C12 cells incubated in differentiation media, which had been corroborated by MPM. It was very hard to get clear images from a fluorescence microscope. CONCLUSIONS: Our findings suggest that the gelatin-based hydrogels can be beneficially utilized as 3D scaffolds for skeletal muscle engineering and that MPM can be effectively applied to imaging technology for tissue regeneration.ope

Cell Migration According to Shape of Graphene Oxide Micropatterns

Photolithography is a unique process that can effectively manufacture micro/nano-sized patterns on various substrates. On the other hand, the meniscus-dragging deposition (MDD) process can produce a uniform surface of the substrate. Graphene oxide (GO) is the oxidized form of graphene that has high hydrophilicity and protein absorption. It is widely used in biomedical fields such as drug delivery, regenerative medicine, and tissue engineering. Herein, we fabricated uniform GO micropatterns via MDD and photolithography. The physicochemical properties of the GO micropatterns were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. Furthermore, cell migration on the GO micropatterns was investigated, and the difference in cell migration on triangle and square GO micropatterns was examined for their effects on cell migration. Our results demonstrated that the GO micropatterns with a desired shape can be finely fabricated via MDD and photolithography. Moreover, it was revealed that the shape of GO micropatterns plays a crucial role in cell migration distance, speed, and directionality. Therefore, our findings suggest that the GO micropatterns can serve as a promising biofunctional platform and cell-guiding substrate for applications to bioelectric devices, cell-on-a-chip, and tissue engineering scaffolds.ope