(303g) Nanoparticles in Motion: The Effect of Gastrointestinal Fluid Chemical Composition on Nanoparticle Stability and Aggregation

The gastrointestinal tract (GIT) is a complex system that poses a challenge for the oral delivery of nanoparticles. The different compositions, pH values, and characteristics of each stage of the GIT (e.g., stomach, small intestine, and colon) can vary extensively. Commonly used bulk techniques to assess the fate of nanoparticles through the GIT have been mostly optimized for testing drug compounds’ solubility or stability, rather than the dynamic behavior of nanoparticles in the GIT, such as aggregation or enzyme corona formation [1]. Furthermore, little is known about how GIT pathologies may affect nanoparticle stability and physicochemical properties after oral administration. For example, it has been reported that normal pH values, osmolality, and lecithin concentration in the GIT can dramatically change when patients suffer from inflammatory bowel disease (IBD) [2]. These changes should be considered when developing nanoparticles for the oral route. Miniaturization of a system where the GIT is mimicked would offer a high surface-to-volume ratio, the possibility of automatization, and a reduced need for valuable chemicals (like enzymes). Cell-free microfluidic devices that mimic drug compound digestion through the GIT have been previously reported [3], however, this process has not been adapted for the study of nanoparticles yet.

The aim of this work is to develop a microfluidic device in which gastrointestinal media (healthy, and IBD simulating media) can be mixed with nanoparticles, to study how the physicochemical properties of the media affect the stability and aggregation of inorganic nanoparticles through each stage of the GIT.

Methods:

Iron oxide nanoparticles were synthesized by flame spray pyrolysis and coated with a silica layer in a single step. They were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS). Commercially available micromixers were then tested. The efficiency with which these micromixers combine and distribute two convergent flow streams to create a uniform mixture was studied. For this purpose, fluorescein dextran MW 10kDa (FITC) was supplied in one flow stream inlet, and water was supplied in another inlet at equal flow rate. The fluorophore intensity throughout the chips at different inlet flow rates (10, 40, and 80 µL/min ) was analyzed. Inflammatory bowel disease-simulating media was developed based on literature, and the herringbone micromixers were utilized to study how the pH, bile acid concentration, lecithin concentration, and soluble protein content of healthy and IBD-simulating media affect nanoparticle stability and aggregation behavior.

Results and Discussion

This work presents advances in the design of a microfluidic device based on reported digestion-on-a-chip systems [3]. A pearl-chain micromixer, two types of herringbone micromixers, and a serpentine micromixer were tested for their mixing efficiency. Mixing of FITC was quantified based on pixel intensity in a cross-section of the last part of the microfluidic channel. The fluorescent images obtained were analyzed using a python code available at https://github.com/yaelsuarez/mixing_quantification. The long herringbone micromixer was selected for further development since it presented the best mixing efficiency. Iron oxide nanoparticles coated with silica were characterized by XRD and showed a maghemite/magnetite crystalline phase. FTIR, TEM, and EDS also confirmed the presence of the silica layer coating the iron oxide nanoparticles. The effects of the media composition on nanoparticle aggregation behavior were investigated using the herringbone micromixer to simulate each stage (stomach, small intestine, and colon) of the GIT.

Conclusion

The most efficient micromixer was selected to continue the development of a microfluidic device that allows the systematic study of the different parameters affecting the stability of nanoparticles through each stage of the GIT (stomach, small intestine, and colon), in a healthy or IBD condition, in an automated and controlled way.

Acknowledgments

This project has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 101002582).

References

[1] S. Asad, Jacobsen, A.C., and A. Teleki. Current Opinion in Chemical Engineering 38 (2022)

[2] C.H. Kim, Y.U. Lee, K.H. S. Kang, G.H. Kang, H. Chu, and S. Lee. Diagnostics 12, 1969 (2022)

[3] P. de Haan, M. A. Ianovska, K. Mathwig, G. A. A. van Lieshout, V. Triantis, H. Bouwmeester, and E. Verpoorte. Lab on a Chip 19 9 (2019)