Exploring Zeolitic Imidazolate Framework‐8 (ZIF‐8) Nanoparticles as Additives to Growth Media for Myoblasts
Authors: Tomlin Ryan A. , Mueller Paul H. , Fischer Kristin M. 
Published: April 2020

Introduction

Injuries resulting in significant skeletal muscle tissue loss cannot be repaired naturally by the body. Tissue engineering research aims to grow mature skeletal muscle cells outside of the patient and reinstitute them as mature, functional tissue. One facet of the research is to test different supplements on in vitro skeletal muscle maturation. Zinc (Zn) shows promise as a supplement given its secondary messenger role in many signaling pathways and increased concentration during skeletal muscle maturation. Zeolitic imidazolate framework‐8 (ZIF‐8) particles are composed of a Zn ion surrounded by four imidazole rings. ZIF‐8 with attached glutamine and carboxaldehyde (ZIF‐8_Glu_S) was synthesized and characterized before in vitro cell studies. Initial work focused on improving ZIF‐8’s suspendability in phosphate buffered saline (PBS) to keep it suspended throughout the autoclave/cool down process necessary to ensure sterility for cell studies. It is hypothesized that ZIF‐8_Glu_S particles will increase myotube length, number, and mitochondrial activity compared to a control.

Materials and Methods

To increase suspendability, ZIF‐8 with attached glutamine (ZIF‐8_Glu) was synthesized using a similar protocol to Liang et al. This product fell out of suspension quickly, so solvent‐assisted linker exchange synthesis (SALE) was done to replace some of the methylimidazole in the ZIF‐8 with imidazole carboxaldehyde to increase suspendibility as described by Jayachandrababu et al. A relative amount of ZIF‐8_Glu_S remained suspended for long enough to move forward. Thus, more ZIF‐8_Glu was synthesized and characterized using FT‐Infrared (FT‐IR) spectroscopy. Microwave plasma atomic emissions spectrometry (MP‐AES) was run to determine Zn as a percentage by mass in the particles and as ppm in PBS suspension.

Results and Discussion

We found that 3 mL of ZIF‐8_Glu_S in PBS stayed suspended for ~2 hours. Thus, the ZIF‐8_Glu synthesis was completed 5 times and characterized. In the IR spectra, there were consistent peaks around 3000–3100 cm−1 indicative of aromatic carbons. The peaks at 2850–2985 cm−1 were expected C‐H stretches. The peaks around 1570–1590 cm−1 were likely shifted imine stretches. The 13C‐NMR and 1H‐NMR characterization is ongoing. For MP‐AES, the ZIF‐8_Glu product was found to contains 10.90% Zn compared to the theoretical value of 28.74% Zn. The remaining product from the ZIF‐8_Glu synthesis will be run through SALE synthesis and characterized using similar instrumentation (as well as SEM). Suspendability tests will be repeated to find the max amount of ZIF‐8_Glu_S that stays suspended for at least 2 hours for sterilization purposes followed by two cell studies.

Conclusion

The IR results suggest that the ZIF‐8_Glu syntheses were successful and contained Zn, but did not stay suspended in PBS. Further work will include syntheses and characterization of the ZIF‐8_Glu_S product and determination of a suspendable concentration. A novel logarithmic cell study will determine a concentration of ZIF‐8_Glu_S that is not toxic to C2C12 skeletal muscle cells. A myogenesis cell study will test ZIF‐8_Glu_S’s effect on myotube length, number, and mitochondrial activity.

Support or Funding Information

Hampden‐Sydney College Research Council and the Departments of Biology and Chemistry.