Improving Calcium Carbonate Based Porous Media for Lateral Flow Assays

Abstract

Nitrocellulose is currently the most common porous material used in commercially available lateral flow assays. It is, however, unsafe to manufacture and time consuming to incorporate into multi-component assay devices. Precipitated calcium carbonate is a material produced from naturally occurring lime that can be suspended in a binder and extruded onto a surface. This extruded suspension forms a porous coating through which a solution can be wicked. The physical characteristics of three different types of calcium carbonate types were investigated to determine differences that may yield better lateral flow. The capillary flow rate through the coating was found to be largely affected by the calcium carbonate type used, the binder concentration and whether any post-printing treatment was applied, specifically heating the print. Calcium carbonate has a high specific surface area, which results in a high protein binding capacity. To prevent protein binding, pre-treating calcium carbonate particles prior to forming the suspension in a binder was attempted. Pre-treatment with bovine serum albumin, casein or methoxy-PEG phosphate did not show prevention of protein binding. Furthermore, by treating the calcium carbonate particles with a protein before suspension formulation, the wicking rate after printing was found to be diminished.