Virus Capture by Nanodiamond Modified Membranes

Nanoscale contaminants such as viruses, industrial dyes and pharmaceutical by-products present serious challenges to health in the water supply, drug manufacture and blood filtration. Of the existing filtration platforms, only ultrafiltration or reverse osmosis can achieve high retention levels of such nanoscale pathogens. These systems are expensive and complex, being mostly limited to centralised water treatment systems. This has led to the development of adsorptive depth filtration (ADF) where contaminants are targeted by van der Waals / electrostatics forces, hydrophobic interactions etc driving contaminant adsorption to the membrane surface. A key advantage of such a technology is that retention is not achieved through size exclusion, allowing much higher flow rates and smaller pressure differentials. It can also enable the removal of nanoscale contaminants by charge whilst allowing larger bodies to pass though the filter. Such approaches are used in blood filtration, virus capture during drug manufacture and virus preconcentration in water monitoring.<br/> <br/>In this work¹, quartz filters were modified with hydrogenated diamond nanoparticles, reversing the zeta potential of the membranes from negative to positive across a wide pH range. Untreated quartz filters demonstrate log0.2 (35%) retention of viruses (MS2 bacteriophage) whereas the diamond modified ones exhibit at least log6.2 (&gt;99.9999%) reduction from feed waters. This is due to the MS2 bateriophage exhibiting a low isoelectric point, in common with the overwhelming majority of viruses. Thus, is has a negative zeta potential in water and is attracted to the positively charged diamond modified membrane. The modified membrane was also tested with far smaller contaminants such as acid black 2 dye and demonstrated &gt;90% higher retention over the unmodified filter. Finally, the diamond modified filter was compared to commercially available electropositive filter membranes where it demonstrated a consistently higher positive zeta potential over a larger pH range. Thus, diamond modified filters offer higher zeta potentials vs pH and thus higher virus retention over current ADF technologies. These filters are also stable over a wider temperature range and flow than the currently available technology.<br/> <br/>¹ H.A. Bland, ACS Appl. Nano Mater. <b>4</b>, 3252 (2021).