Harnessing the Bio-Nano Interactions of Natural Clay for Advanced Antimicrobial Solutions

Biological cells have evolved alongside of natural mineral clay (layered aluminosilicates) leading to intriguing interactions from beneficial to bio-adverse. Specifically, bacteria were shown to adhere to clay particles and even incorporate them into their biofilm¹. We endeavor to direct these interactions to neutralize a specific pathogenic bacterial srain in a heterogenous culture, maintaining the non-pathogenic populations unharmed and mitigating the global surge in antibiotic resistance. To that end, we utilize Halloysite nanotubes (HNTs), which are 600-900 nm long and 50 nm wide, and exhibit a hollow lumen with an inner diameter of 15 nm. This intrinsic mesoporous morphology of HNTs combined with their adsorptive silica surface renders the clay ideal for carrying various antimicrobial cargoes. The desired specific antibacterial effect is based on the selective binding of the clay to the target bacteria which is realized by antibodies we immobilize onto the HNTs’ surface². Next, we investigate the loading of the antibody-functionalized HNTs with two separate antimicrobial payloads: (1) the potent antibiotic ciprofloxacin (CIP) to be gradually released near the target bacteria³, or (2) plasmonic gold nanorods (AuNR) to be activated by near-infrared irradiation for a local photothermal effect.<br/><br/>The selective binding of the Ab-functionalized HNTs to their target bacteria is confirmed by fluorescence and electron microscopy along with high-throughput imaging flow cytometry⁴. Consequently, CIP-loaded Ab-HNTs exert a two-fold higher potency against the target bacteria, whereas in the same heterogeneous culture, the inhibition of non-target bacteria is decreased by 50-90%. Regarding the AuNR-Ab-HNTs hybrids, upon irradiation with a near-infrared laser, a superior antibacterial activity is observed in comparison to free AuNR, despite the 5-fold higher increase in bulk temperature induced by the latter⁴. In addition, the biocompatibility of the multifunctional clay is studied towards a physiologically relevant co-culture of human colon epithelial cells (Caco-2 / HT29) and the localization of the particles after administration is investigated.<br/><br/>In this presentation, I will discuss our findings as well as the preceding considerations involved from the bioconjugation step to the loading of the clay for obtaining the desired bio-nano interactions. We believe this work signifies the potential in comprehending the interface between biological cells and natural nanomaterials, which are abundant and easily obtainable, to utilize the latter for novel biomedical applications.<br/><br/><u><u>References:</u></u><br/>1) Prinz Setter, O., Segal, E., 2020. Halloysite nanotubes - the nano-bio interface. Nanoscale 12, 23444–23460. https://doi.org/10.1039/d0nr06820a<br/><br/>2) Prinz Setter, O., Movsowitz, A., Goldberg, S., Segal, E., 2021. Antibody-Functionalized Halloysite Nanotubes for Targeting Bacterial Cells. ACS Appl. Bio Mater. 4, 4094–4104. https://doi.org/10.1021/acsabm.0c01332<br/><br/>3) Prinz Setter, O., Dahan, L., Abu Hamad, H., Segal, E., 2022. Acid-etched Halloysite Nanotubes as Superior Carriers for Ciprofloxacin. Appl. Clay Sci. 228, 106629. https://doi.org/10.1016/j.clay.2022.106629<br/><br/>4) Prinz Setter, O., Snoyman, I., Shalash, G., Segal, E., 2022. Gold Nanorod-Incorporated Halloysite Nanotubes Functionalized with Antibody for Superior Antibacterial Photothermal Treatment. Pharm. 2022, Vol. 14, Page 2094 14, 2094. https://doi.org/10.3390/PHARMACEUTICS14102094