DNA-Modified Plasmonic Sensor for the Direct Detection of Virus Biomarkers from the Blood.

The rapid spread of viral infections demands early detection strategies to minimize proliferation of the disease. Here, we demonstrate a plasmonic biosensor to detect Dengue virus, which was chosen as a model, via its nonstructural protein NS1 biomarker. The sensor is functionalized with a synthetic single-stranded DNA oligonucleotide and provides high affinity toward NS1 protein present in the virus genome. We demonstrate the detection of NS1 protein at a concentration of 0.1-10 µg/mL in bovine blood using an on-chip microfluidic plasma separator integrated with the plasmonic sensor which covers the clinical threshold of 0.6 µg/mL of high risk of developing Dengue hemorrhagic fever. The conceptual and practical demonstration shows the translation feasibility of these microfluidic optical biosensors for early detection of a wide range of viral infections, providing a rapid clinical diagnosis of infectious diseases directly from minimally processed biological samples at point of care locations.

Multiplex Viral Detection Platform Based on a Aptamers-Integrated Microfluidic Channel.

A polydimethylsiloxane-based microfluidic device has been developed for the multiplex detection of viral envelope proteins such as Zika and chikungunya on a single platform using aptamer-analyte interactions. The channel is integrated with microsized pillars that increase the surface area allowing more aptamers to attach to the incoming envelope protein molecules, thus increasing the overall sensitivity of the system. The working of the device depends on the formation of protein-mediated sandwich morphology that is obtained using an aptamer and aptamer-functionalized gold nanoparticle (AuNP) pair. The colorimetric signal is obtained upon introduction of silver reagents into the channel, which are selectively deposited on the AuNP surface, providing a gray contrast in the testing zone. The microfluidic channel approach successfully detected clinically relevant concentrations of Zika and chikungunya envelope proteins in phosphine-buffered saline (1 pM) and calf blood (100 pM) with high specificity using gold-decorated aptamers integrated in a microfluidic channel.

Aptamer-gold nanoparticle conjugates for the colorimetric detection of arboviruses and vector mosquito species.

The real-time, colorimetric detection of analytes via aptamer-gold nanoparticle technology has proven to be an important, emerging technique within the medical field. Of global health importance, the ability to detect vector mosquito species, such as the Aedes (Ae.) aegypti mosquito, and transmitted arboviruses, such as Zika virus, is paramount to mosquito control and surveillance efforts. Herein, we describe the detection of Ae. aegypti salivary protein for vector identification and the detection of Zika virus to assess mosquito infection status by aptamer-gold nanoparticle conjugates. Key to optimization of these diagnostics were gold nanoparticle capping agents and aptamer degree of labelling (i.e., the amount of aptamers per gold nanoparticle). In the present study, detection was achieved for as little as 10 ng Ae. aegypti salivary protein and 1.0 × 105 PFU live Zika virus. These aptamer-gold nanoparticle conjugate diagnostics could one day prove to be useful as deployable nano-based biosensors that provide easy-to-read optical read outs through a straightforward red-to-blue colour change either within a diagnostic solution or atop a card/membrane-based biosensor.

Highly selective aptamer based organic electrochemical biosensor with pico-level detection.

An organic aptamer functionalized electrochemical transistor has been developed to detect the presence of epinephrine molecule which acts as an excitatory neurotransmitter. The abnormalities in the level of epinephrine are the direct symptoms of some diseases such as Takotsubo cardiomyopathy, myocardial infarction, arrhythmias and other heart related diseases. The present approach is based on immobilization of aptamers on the gate electrode which selectively binds to epinephrine with high affinity. The introduction of epinephrine in the system causes screening of negative charge of aptamers as well as the production of Faradaic current due to oxidation of epinephrine. The synergistic effect of these two events decreases the overall channel current which was seen in both transfer characteristics and current-time curve. Additional experiments against common interfering agents (dopamine, ascorbic acid, DOPAC etc) showed no decrease in the current which indicates high specificity of the sensor. Overall, the incorporation of aptamers in the transistor has allowed us to obtain a sensor exhibiting the lowest limit of detection for epinephrine (90 pM) till date which is comparable to normal physiological level. This approach provides a real-time detection of a large range of biomolecules and viral proteins in a time and cost-effective manner and has applications in point-of-care testing tool for several diagnostic applications.