Skip to main content
2024 BMES Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Orthopedic and Rehabilitation Engineering

Orthopedic and Rehabilitation Engineering - Poster Session C

Poster K10 - Growth Factor Delivery from Bioprinted Collagen Hydrogels to Enhance Fibrocartilage Differentiation

Friday, October 25, 2024
10:00 AM – 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  There are approximately 175,000 ACL reconstruction surgeries each year, but approximately 10% of these grafts fail, with one of the main failure points being the bone-fibrocartilage-ligament (BFL) interface. We propose to develop a gradient sleeve containing growth factors and other stimuli within the appropriate regions that can be added to an autologous graft and strengthen this interface. However, matching the gradient of the BFL from bone to fibrocartilage is challenging. Studies have tried using different materials and growth factors for cartilage production. For example, placing transforming growth factor-β3 (TGF- β3) in cell media can promote chondrogenic differentiation. However, for our study, it is not clear if the growth factor will stay near the scaffold, and in the right region of the sleeve, because of diffusion. Thus, this study aims to observe the spatio-temporal availability of TBF-β3 incorporated within a collagen hydrogel and its impact on the differentiation potential of mesenchymal stem cells (MSCs).

Materials and

Methods:  A construct with two sides, one with incorporated TGF- β3, was printed to allow investigation of the diffusion of the growth factor both into the other section of the hydrogel and out of the hydrogel. TGF-β3 loadings of 0, 10, and 20 ng/ml were tested. The bio-ink consisted of methacrylate collagen, streptavidin magnesphere paramagnetic (SMP) particles, and TBF-β3. Once printed with a magnet, the construct was incubated and crosslinked before being lifted. The interface between the two sides was characterized with SEM and optical coherence tomography (OCT) techniques. This included printing one side with SMP particles and the other side with deionized water to aid in visualization. An ELISA assay was run to obtain TGF- β3 concentrations released into the media from 8 – 72 h and in the different sides of the hydrogel after crushing the hydrogels. MSCs up to passage seven were seeded on top of the constructs and allowed to grow for 7 days prior to preliminary analysis (e.g., phalloidin staining). We are currently performing further investigation of MSC differentiation on the hydrogels in the form of RT-PCR, and we are assessing different ways to deliver TGF-β3, such as conjugation to the streptavidin-coated SMPs.

Results, Conclusions, and Discussions: The SEM images showed the SMP particles on the SMP portion of the hydrogel scaffold with limited particles on the water portion of the hydrogel. The same result is shown with the OCT images. When both sides of the hydrogel scaffold are imaged, only the SMP portion is visible in the image. When the image is sliced from the side, the interface can be seen to only overlay slightly at the top of the hydrogel. This shows that when printed on a magnet with SMP, an interface can be achieved between the two hydrogels. Next, a release study showed a total release of 0.154 ng or 44% of TGF-β3 from the 10 ng/ml hydrogel within 24 h, with a significant drop of TGF-β3 release after the initial 24-hour time period; there is also likely diffusion of the TGF-β3 that occurs into the other side of the hydrogel. The assay is ongoing with additional samples being analyzed. After 7 days, the phalloidin stain showed that MSCs attached and were well spread. Overall, this study shows that this model system has an established interface between the two sides that can be used to assess the release of growth factors from gradient hydrogel constructs. It also suggests the importance of investigating different methods of delivery, such as the release of TGF-β3 from SMP particles, for more extended and localized release.

Acknowledgements (Optional):  This project was funded by the National Institute of Health grant R15 ARO71102/NIAMS.