Biosensor Research Facilitated by LVEM5

Field-portable biosensing is a field with significant progress and promise. The ability to detect for analytes with portable equipment enables real-time information gathering, analysis, and decision-making. Recently, a label-free gold nanoprism aptamer-based biosensor was developed for the detection of ochratoxin A, or OTA. (Hernández, 2020) The sensors are able to trap the target molecules between the points of the prisms, which allows portable Surface Enhanced Raman Spectroscopy (SERS) equipment to gain molecular fingerprint signatures on the target analyte and confirm its presence in the range of 10 to 250 ppb. OTA is a naturally occurring mycotoxin produced by Aspergillus and Penicillium species that can contaminate foods including coffee, cereals, wine and beer. Traditional detection approaches require sending samples to laboratories for mass spectrometry or fluorescence spectrometry analysis, a time-consuming process.

Aptamer-based recognition

The biosensors utilize DNA aptamers, short sequences that fold upon themselves into three dimensional structures that specifically recognize targets of interest. Aptamers are also more robust for transport than antibodies, with broader ambient temperature ranges being better tolerated. In this study, aptamers specific to OTA were utilized, which traps the molecule between the points of the nanoprisms.

LVEM Confirms Sensor-Analyte Assemblies

To confirm that the analytes were trapped between the points of the nanoprisms, the LVEM5 was used to visualize the resulting nanosensor-analyte assembly structures. The gold nanoprisms provide a naturally strong dark contrast for TEM imaging. Since low voltage electron microscopy provides enhanced contrast of carbon-based materials, the aptamers on the surfaces of the nanoprisms were easily visualized, as were the presence of analyte molecules sandwiched between two prisms. 

(Hernández, 2020)

TEM imaging is a powerful confirmation that the proposed mechanisms are indeed working. While the majority of the data presented in the publication validating the performance of the system focuses on determining detection limits and performance in complex matrices, the role of LVEM in providing an orthogonal characterization technique that visually demonstrates the assembled biosensor is of pivotal importance.

Conclusion

Direct imaging of biosensor structures provides a high degree of confidence confirming other validation data during sensor development studies. The LVEM5 provides excellent contrast of carbon base materials, allowing imaging of target analyte molecules and surface coatings on nanostructured assemblies used for novel sensor structures.

References:

Hernández Y, Lagos LK, Galarreta BC. Development of a label-free-SERS gold nanoaptasensor for the accessible determination of ochratoxin A. Sensing and Bio-Sensing Research. 2020 Jun 1;28:100331.

About the author:

Robert I. MacCuspie, Ph.D., has over twenty years of experience in nanotechnology and materials characterization, at national laboratories, academia and corporations, working at the interface of business and science.