Antiviral Nanostructures

The overwhelming majority of viruses exhibit a net negative charge in solution (zeta potential) over a wide pH range¹. This means that viruses are attracted to positively charges surfaces in solution and this has led to the development of positively charged filter membranes by Invitrogen (Bright Star), 3M (Zeta Plus) and NanoCeram for virus filtration. A key advantage of such a technology is that virus retention is not achieved through size exclusion, but electrostatics, allowing much higher flow rates and smaller pressure differentials.<br/>Few materials exhibit positive zeta potentials in water over a significant pH range, the most common examples being Alumina, Ceria, MgO, Carbon, nanodiamond etc. By self-assembling nanoparticles of the above materials onto conventional depth filter materials such as quartz fibre, it is possible to reverse the filter zeta potential from negative to positive charge, thus making it attract viruses. It should be noted that without these nanoparticles, these filters have 10µm pores which are unable to remove 10-200nm sized viruses from water.<br/>We will demonstrate the efficacy of virus filtration with positively charged filter membranes fabricated by the above process in comparison with conventional filter materials and incumbent technologies such as those by NanoCeram, Invitrogen and 3M. In particular, we will show that nanodiamond modified filter membranes can remove in excess of log6 (99.9999%) of viruses (MS2 bacteriophage) from water over an unrivalled pH range. The diamond modified filter exhibits a significantly higher positive zeta potential across a wider pH range than other commercial membranes such as NanoCeram. We will show similar performance against Acid Black II, a dye significantly smaller that viruses.<br/>¹ B. Michen, J. Appl. Microbiol. <b>109</b>, 388 (2010).<br/>² H.A. Bland, ACS Appl. Nano Mater. <b>4</b>, 3252 (2021).