Carolyn Kim

All Publications

• Development and systematic characterization of GelMA/alginate/PEGDMA/xanthan gum hydrogel bioink system for extrusion bioprinting. Biomaterials Li, J., Moeinzadeh, S., Kim, C., Pan, C. C., Weale, G., Kim, S., Abrams, G., James, A. W., Choo, H., Chan, C., Yang, Y. P. 2022; 293: 121969

  Abstract

  Gelatin methacryloyl (GelMA)/alginate-based hydrogels have shown great promise in bioprinting, but their printability is limited at room temperature. In this paper, we present our development of a room temperature printable hydrogel bioink by introducing polyethylene glycol dimethacrylate (PEGDMA) and xanthan gum into the GelMA/alginate system. The inclusion of PEGDMA facilitates tuning of the hydrogel's mechanical property, while xanthan gum improves the viscosity of the hydrogel system and allows easy extrusion at room temperature. To fine-tune the mechanical and degradation properties, methacrylated xanthan gum was synthesized and chemically crosslinked to the system. We systematically characterized this hydrogel with attention to printability, strut size, mechanical property, degradation and cytocompatibility, and achieved a broad range of compression modulus (∼10-100 kPa) and degradation profile (100% degradation by 24 h-40% by 2 weeks). Moreover, xanthan gum demonstrated solubility in ionic solutions such as cell culture medium, which is essential for biocompatibility. Live/dead staining showed that cell viability in the printed hydrogels was over 90% for 7 days. Metabolic activity analysis demonstrated excellent cell proliferation and survival within 4 weeks of incubation. In summary, the newly developed hydrogel system has demonstrated distinct features including extrusion printability, widely tunable mechanical property and degradation, ionic solubility, and cytocompatibility. It offers great flexibility in bioprinting and tissue engineering.

  View details for DOI 10.1016/j.biomaterials.2022.121969

  View details for PubMedID 36566553

• Hybprinting for musculoskeletal tissue engineering. iScience Li, J., Kim, C., Pan, C., Babian, A., Lui, E., Young, J. L., Moeinzadeh, S., Kim, S., Yang, Y. P. 2022; 25 (5): 104229

  Abstract

  This review presents bioprinting methods, biomaterials, and printing strategies that may be used for composite tissue constructs for musculoskeletal applications. The printing methods discussed include those that are suitable for acellular and cellular components, and the biomaterials include soft and rigid components that are suitable for soft and/or hard tissues. We also present strategies that focus on the integration of cell-laden soft and acellular rigid components under a single printing platform. Given the structural and functional complexity of native musculoskeletal tissue, we envision that hybrid bioprinting, referred to as hybprinting, could provide unprecedented potential by combining different materials and bioprinting techniques to engineer and assemble modular tissues.

  View details for DOI 10.1016/j.isci.2022.104229

  View details for PubMedID 35494239

• A bioactive synthetic membrane improves bone healing in a preclinical nonunion model. Injury DeBaun, M. R., Salazar, B. P., Bai, Y., Gardner, M. J., Yang, Y. P., Stanford iTEAM group, Pan, C., Stahl, A. M., Moeinzadeh, S., Kim, S., Lui, E., Kim, C., Lin, S., Goodnough, L. H., Wadhwa, H. 1800

  Abstract

  OBJECTIVES: High energy long bone fractures with critical bone loss are at risk for nonunion without strategic intervention. We hypothesize that a synthetic membrane implanted at a single stage improves bone healing in a preclinical nonunion model.METHODS: Using standard laboratory techniques, microspheres encapsulating bone morphogenic protein-2 (BMP2) or platelet derived growth factor (PDGF) were designed and coupled to a type 1 collagen sheet. Critical femoral defects were created in rats and stabilized by locked retrograde intramedullary nailing. The negative control group had an empty defect. The induced membrane group (positive control) had a polymethylmethacrylate spacer inserted into the defect for four weeks and replaced with a bare polycaprolactone/beta-tricalcium phosphate (PCL/beta-TCP) scaffold at a second stage. For the experimental groups, a bioactive synthetic membrane embedded with BMP2, PDGF or both enveloped a PCL/beta-TCP scaffold was implanted in a single stage. Serial radiographs were taken at 1, 4, 8, and 12 weeks postoperatively from the definitive procedure and evaluated by two blinded observers using a previously described scoring system to judge union as primary outcome.RESULTS: All experimental groups demonstrated better union than the negative control (p=0.01). The groups with BMP2 incorporated into the membrane demonstrated higher average union scores than the other groups (p=0.01). The induced membrane group performed similarly to the PDGF group. Complete union was only demonstrated in groups with BMP2-eluting membranes.CONCLUSIONS: A synthetic membrane comprised of type 1 collagen embedded with controlled release BMP2 improved union of critical bone defects in a preclinical nonunion model.

  View details for DOI 10.1016/j.injury.2022.01.015

  View details for PubMedID 35078617

• The Influence of Electron Beam Sterilization on In Vivo Degradation of beta-TCP/PCL of Different Composite Ratios for Bone Tissue Engineering. Micromachines Kang, J., Kaneda, J., Jang, J., Sakthiabirami, K., Lui, E., Kim, C., Wang, A., Park, S., Yang, Y. P. 2020; 11 (3)

  Abstract

  We evaluated the effect of electron beam (E-beam) sterilization (25 kGy, ISO 11137) on the degradation of beta-tricalcium phosphate/polycaprolactone (beta-TCP/PCL) composite filaments of various ratios (0:100, 20:80, 40:60, and 60:40 TCP:PCL by mass) in a rat subcutaneous model for 24 weeks. Volumes of the samples before implantation and after explantation were measured using micro-computed tomography (micro-CT). The filament volume changes before sacrifice were also measured using a live micro-CT. In our micro-CT analyses, there was no significant difference in volume change between the E-beam treated groups and non-E-beam treated groups of the same beta-TCP to PCL ratios, except for the 0% beta-TCP group. However, the average volume reduction differences between the E-beam and non-E-beam groups in the same-ratio samples were 0.76% (0% TCP), 3.30% (20% TCP), 4.65% (40% TCP), and 3.67% (60% TCP). The E-beam samples generally had more volume reduction in all experimental groups. Therefore, E-beam treatment may accelerate degradation. In our live micro-CT analyses, most volume reduction arose in the first four weeks after implantation and slowed between 4 and 20 weeks in all groups. E-beam groups showed greater volume reduction at every time point, which is consistent with the results by micro-CT analysis. Histology results suggest the biocompatibility of TCP/PCL composite filaments.

  View details for DOI 10.3390/mi11030273

  View details for PubMedID 32155781