Nanomaterials for pregnancy detection

Abstract

Point of care (POC) is a powerful tool as a diagnostic test because of its advantage of being small, portable device and rapid results obtained. One major class of POC is the lateral flow assay (LFA), which is widely used for protein determinations. A home pregnancy test is the most successful example of the LFAs. A limitation of being quantitative or at best semi quantitative assay leads to improve the assay performance and to enhance its sensitivity. Hence, for this project, a switch from visual detections to electrochemical measurements is the primary goal, which occurred by developing the assay’ concept with keeping the ease and robustness of the traditional LF assay. The integration of streptavidin lateral flow with electrochemical measurements (in particular voltammetric techniques) is the key element to introduce an electrochemical lateral flow assay (ELFA). This concept was based on the amplification of the polymer nanoparticles. A pH responsive eudragit S- 100 was synthesized by nanoprecipitation process. These PNPs are encapsulated with redox active probe such as hydroxylmethyl ferrocene. Eudragit S-100 is dissolved at pH > 7 and it is insoluble in an acidic condition. This dissolution mechanism is preferable since the release of entrapped probe can be controlled until it is being detectable at the test line. Our findings summarized as follows; nanoprecipitation process is able to synthesis PNPs encapsulated both hydroxylmethyl ferrocene and methylene blue. These small-sized particles (~200 nm and ~300 nm) have a highly value negative zeta potentials (-34 mV and -29 mV). These two proprieties respectively, are important in enhancing the probe loading efficiency and in efficient adsorption with the antibody. From our data, it was found that more than 50% of the probes were encapsulated. Further characterizations were performed to investigate the probes’ electroactivity as well as their electrochemical behavior. These voltammetric techniques include cyclic voltammetry and square wave voltammetry, the results suggested good electrochemical behaviors of both probes in respect of their release form the PNPs in immobilized format as well as in the aqueous phase. Importantly, an electrochemical lateral flow assay (ELFA) was investigated the FcMeOH-PNPs and was successfully demonstrated in the presence of varied concentrations of hCG compared to the control (absence of hCG). This indicates that the applied approach was proven. However, further improvements are needed. This led to move toward the screen-printed technology to realize a point of care device.