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New rapid lab-on-a-chip detects dengue antibodies from saliva.

Finding out whether you have been infected with dengue may soon be as easy as spitting into a rapid test kit. The Institute of Bioengineering and Nanotechnology (IBN) of A*STAR has developed a paper-based disposable device that will allow dengue-specific antibodies to be detected easily from saliva within 20 minutes. This device is currently undergoing further development for commercialization.

The rapid diagnostic kit can detect a key dengue antibody from saliva that is present in early-stage secondary infection. The ability to differentiate between primary and secondary dengue infections makes it a valuable early diagnosis tool that would help to ensure timely treatment and proper care of patients.  Patients with secondary infection, who have previously been infected with other serotypes of dengue virus, stand a higher risk of developing dengue hemorrhagic fever or dengue shock syndrome.

According to Singapore’s National Environment Agency, dengue fever and its more severe form, dengue hemorrhagic fever, are the most common mosquito-borne viral diseases in the world. This disease poses a serious health threat, and is a leading cause of illness and death in tropical and subtropical climates. There are four known serotypes of the dengue virus but no vaccine or medicine has been developed to treat the illness. The incubation period before symptoms develop generally ranges from 4 to 10 days after infection. Therefore, early diagnosis would enable the patient to receive prompt medical attention and avoid further complications.

Currently, dengue infection is diagnosed in the laboratory by testing the patient’s blood sample for the presence of dengue antigens or antibodies. IBN’s device, on the other hand, is capable of detecting IgG, a dengue-specific antibody found at the onset of secondary infections, directly from saliva in one step.

Unlike blood samples, saliva can be collected easily and painlessly for rapid point-of-care diagnostics. However, unlike other body fluids, it cannot be applied directly to commercially available test kits as it would cause the sensor nanoparticles to stick haphazardly to the test strip. In addition, conventional paper-based tests are not designed to handle the larger sample volume of saliva required.

As described in the journal Lab on a Chip, the researchers used an innovative stacking flow design to overcome key challenges faced by existing lateral flow designs, such as those used in pregnancy test kits.

In the current study the device has different flow paths created for samples and reagents through a multiple stacked system. This allows the saliva sample to flow separately through a fiber glass matrix, which removes the substances that would interfere with the nanoparticle-based sensing system before it mixes with the sensor nanoparticles. The new device configuration also helps to regulate the flow in the test strip, generating uniform test lines for more accurate results.

The new diagnostic device can also be adapted to detect other infectious diseases such as HIV and Syphilis. The researchers are also investigating the use of other common fluid samples, such as blood, urine and serum for rapid, high-sensitivity test kits.

The Institute is currently collaborating with ARKRAY Inc., a pioneer in the field of automated analysis systems, to commercialize its paper-based diagnostic technology. The ARKRAY Inc research center is focused on developing novel detection kits for infectious diseases based on IBN’s innovative diagnostic platforms.

Source:  The Institute of Bioengineering and Nanotechnology (IBN) of A*STAR

 

Paper-based immunoassays, usually in the form of lateral flow tests, are currently the standard platform for home diagnostics. However, conventional lateral tests are often complicated by severe non-specific adsorption of detector particles when applied to test samples containing salivary fluid. It is believed that a high concentration of proteinaceous substances in salivary fluid causes particle aggregation and adhesion. In this study, we developed a stacking flow platform for single-step detection of a target antibody in salivary fluid. Stacking flow circumvents the need for separate sample pre-treatments, such as filtration or centrifugation, which are often required prior to testing saliva samples using paper-based immunoassays. This is achieved by guiding the samples and reagents to the test strip through different paths. By doing so, salivary substances that interfere with the particle-based sensing system are removed before they come into contact with the detection reagents, which greatly reduces the background. In addition, the stacking flow configuration enables uniform flow with a unique flow regulator, which leads to even test lines with good quantification capability, enabling the detection of ~20 ng mL−1 α-fetoprotein in the serum. We have successfully applied the stacking flow device to detect dengue-specific immunoglobulins that are present in salivary fluid.  A stacking flow immunoassay for the detection of dengue-specific immunoglobulins in salivary fluid.  Ying et al 2015.
Paper-based immunoassays, usually in the form of lateral flow tests, are currently the standard platform for home diagnostics. However, conventional lateral tests are often complicated by severe non-specific adsorption of detector particles when applied to test samples containing salivary fluid. It is believed that a high concentration of proteinaceous substances in salivary fluid causes particle aggregation and adhesion. In this study, we developed a stacking flow platform for single-step detection of a target antibody in salivary fluid. Stacking flow circumvents the need for separate sample pre-treatments, such as filtration or centrifugation, which are often required prior to testing saliva samples using paper-based immunoassays. This is achieved by guiding the samples and reagents to the test strip through different paths. By doing so, salivary substances that interfere with the particle-based sensing system are removed before they come into contact with the detection reagents, which greatly reduces the background. In addition, the stacking flow configuration enables uniform flow with a unique flow regulator, which leads to even test lines with good quantification capability, enabling the detection of ~20 ng mL−1 α-fetoprotein in the serum. We have successfully applied the stacking flow device to detect dengue-specific immunoglobulins that are present in salivary fluid. A stacking flow immunoassay for the detection of dengue-specific immunoglobulins in salivary fluid. Ying et al 2015.

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