Influence of Salts on Virus Adsorption to Microporous Filters

Abstract

We investigated the direct and indirect effects of mono-, di-, and trivalent salts (NaCl, MgCl 2 , and AlCl 3 ) on the adsorption of several viruses (MS2, PRD-1, X174, and poliovirus 1) to microporous filters at different pH values. The filters studied included Millipore HA (nitrocellulose), Filterite (fiberglass), Whatman (cellulose), and 1MDS (charged-modified fiber) filters. Each of these filters except the Whatman cellulose filters has been used in virus removal and recovery procedures. The direct effects of added salts were considered to be the effects associated with the presence of the soluble salts. The indirect effects of the added salts were considered to be (i) changes in the pH values of solutions and (ii) the formation of insoluble precipitates that could adsorb viruses and be removed by filtration. When direct effects alone were considered, the salts used in this study promoted virus adsorption, interfered with virus adsorption, or had little or no effect on virus adsorption, depending on the filter, the virus, and the salt. Although we were able to confirm previous reports that the addition of aluminum chloride to water enhances virus adsorption to microporous filters, we found that the enhanced adsorption was associated with indirect effects rather than direct effects. The increase in viral adsorption observed when aluminum chloride was added to water was related to the decrease in the pH of the water. Similar results could be obtained by adding HCl. The increased adsorption of viruses in water at pH 7 following addition of aluminum chloride was probably due to flocculation of aluminum, since removal of flocs by filtration greatly reduced the enhancement observed. The only direct effect of aluminum chloride on virus adsorption that we observed was interference with adsorption to microporous filters. Under conditions under which hydrophobic interactions were minimal, aluminum chloride interfered with virus adsorption to Millipore, Filterite, and 1MDS filters. In most cases, less than 10% of the viruses adsorbed to filters in the presence of a multivalent salt and a compound that interfered with hydrophobic interactions (0.1% Tween 80 or 4 M urea).The effects of salts on virus adsorption to microporous filters have been studied for many years and have been discussed in several reviews (4,13,16,17,28). In previous studies, the researchers concluded that addition of aluminum ions (or magnesium ions) enhanced viral adsorption to microporous filters, and from these results it was concluded that the presence of salts is necessary for optimum viral adsorption to the filters (4,13,16,17,27,28). However, we found two problems with the earlier studies. First, relatively few viruses and few microporous filters were studied. Much of the information was information concerning the adsorption of poliovirus to nitrocellulose filters (Millipore filters). However, due to recent developments in filter technology, new filters that have substantially different properties than the filters previously studied are current...

Development and application of a one-step low cost procedure to concentrate viruses from seawater samples

“…This effect is also in agreement with previously studies described by Lukasik et al, (2000). Apparently, the attachment of the viruses to the matrices, which in the first step is of electrostatic nature, is hampered by a high ionic strength and this would explain the low efficiency observed of adsorption-elution methods for the concentration of viruses from seawater (Lukasik et al, 2000). Experiments conducted to determine the time necessary for adenoviruses present in spiked samples to attach to skimmed milk flocs, indicate, as shown figure 1, that approximately five hours of stirring are needed for full attachment.…”

“…Its poor performance in seawater seems to be a general phenomenon concerning many viruses as shown in the present study, the overall recovery of the heterogeneous somatic phage population present in wastewater also decreased in seawater. This effect is also in agreement with previously studies described by Lukasik et al, (2000). Apparently, the attachment of the viruses to the matrices, which in the first step is of electrostatic nature, is hampered by a high ionic strength and this would explain the low efficiency observed of adsorption-elution methods for the concentration of viruses from seawater (Lukasik et al, 2000).…”

Field-based evaluation of a male-specific (F+) RNA coliphage concentration method

“…It was reported that electropositive filters showed low recovery of the GI FRNA coliphage MS2 spiked to a concentration of 10 6 pfu/l in water containing NaCl (Lukasik et al, 2000;Wong et al, 2012). In contrast, excellent adsorption of 10 11 pfu/l of the GIII FRNA coliphage Q␤ to electropositive NanoCeram filters (Argonide, Sanford, FL) in marine water has been reported (Gibbons et al, 2010).…”

Evaluation of positively charged alumina nanofibre cartridge filters for the primary concentration of noroviruses, adenoviruses and male‐specific coliphages from seawater

“…High salts concentrations and a pH below the virus isoelectric point will promote both electrostatic (ionic) and hydrophobic interactions between the viruses and filter. Electronegative cellulose ester filters such as Millipore HA can establish more hydrophobic interactions than electrostatic interactions with the viruses and perform better in samples with high salt concentrations (Lukasik et al 2000). Electropositive 1MDS filters mostly interact with the virus by electrostatic interactions, and the presence of salts in the water adversely interferes with the capacity of the electropositive 1MDS filter to adsorb viruses.…”

“…The adsorption of the virus to the filter matrix is determined by electrostatic and hydrophobic interactions. Sample salt concentrations and pH can influence the adsorption of viruses to electronegative and electropositive filters in different ways (Lukasik et al 2000). High salts concentrations and a pH below the virus isoelectric point will promote both electrostatic (ionic) and hydrophobic interactions between the viruses and filter.…”