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Biomaterials

Biomaterials - Poster Session C

Poster C2 - Incorporation of Gas Vesicles in Silk Fibroin Scaffolds

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

Introduction:  Biomaterials research using scaffolds has been crucial in regenerative medicine. A major goal in biomaterials research is to develop an approach for tailoring biomaterial scaffold degradation - in this case, silk fibroin scaffolds - to the patient's regenerative environment in wound healing. Matching the degradation to the regenerative rate is crucial, yet difficult due to highly variable patient regenerative environments, because the degradation will provide the adaptive space for the regenerating host tissue to expand into and replace the scaffold with its own extracellular matrix environment. [1] The long-term goal of our work is to develop a personalized biomaterial platform, where biomaterial degradation can be adjusted with focused ultrasound following routine monitoring of how the patient is healing. In this work, we target to develop a non-invasive method to control biomaterial scaffold degradation rate by incorporating ultrasound-responsive protein nanostructure — gas vesicles (GVs) — with silk fibroin scaffolds. This degradation will be activated using a technique called Low-Intensity Focused Ultrasound (LIFU). [2] Through characterization techniques, we can demonstrate the effective incorporation of GVs inside silk fibroin scaffolds, which allows for the creation of acoustically sensitive silk biomaterials for various biomedical applications.

Materials and

Methods:  Scaffold fabrications: First, silk fibroin was isolated from the Bombyx mori cocoons. This was degumming cocoons in NaOH. Then, the silk fibroin sheets were placed in a high-concentration solution of LiBr and heated in the oven for four hours to dissolve. The fibroin solutions were then dialyzed against deionized water and centrifuged to remove impurities. After thoroughly mixing GV suspension with 6% silk fibroin solution into a small plastic container, porogen was added to the system to cause aqueous silk fibroin to solidify. [3] After 48 hours of room temperature incubation, deionized water was added to dissolve and leach out the porogen for 48 hours.
Characterizations: Fabricated scaffolds were imaged using an ultrasound imaging paradigm named cross-amplitude modulation (xAM) to confirm the incorporation of GVs. This is achieved by specifically capturing non-linear scattering from GVs using xAM. [4] Then we applied high-pressure ultrasound to collapse GVs and performed another xAM imaging on the sample to create a contrast between pre-collapse and post-collapse images to characterize the existence of GVs within the fibroin scaffold matrix. MATLAB was utilized to process all the images.

Results, Conclusions, and Discussions: 

Discussion: Figure 1A is a scheme to illustrate our xAM ultrasound imaging to confirm the presence of GVs. Figure 1B & 1C shows the corresponding xAM ultrasound images of GV-incorporated silk scaffolds. Comparing the pre-collapse and post-collapse images, the pre-collapse image had a significantly higher signal, as shown via differences in brightness between the images. In the post-collapse image, since the ultrasound has collapsed the gas vesicles, it scatters a weaker signal. The findings indicate that gas vesicles were incorporated into the silk fibroin scaffold matrix and the incorporation is characterized by the visual difference in pre-collapse and post-collapse signals scattered from the scaffold matrix.

Conclusion: Our method of incorporating GVs in the silk fibroin scaffolds was demonstrated to be effective. This is the first step of towards creating a more controlled, non-invasive, and targeted scaffold degradation approach to match the patient’s regenerative rate in in vivo applications.

Acknowledgements (Optional):  The authors would like to thank all the members of the Abbott Lab at Carnegie Mellon University and members of the Shapiro Lab at California Institute of Technology. This research was funded in part by Summer Undergraduate Research Fellowship 2024 from Caltech Student Faculty Programs (SFP) department (Kim) and in part by Summer Undergraduate Research Fellowship 2023 from Carnegie Mellon University SURF Department (Kim).