Molecular Sensor Performs In-Situ Analysis of Complex Biological Fluids.
Schematic illustrating the concentration of charged small molecules and the exclusion of large adhesive proteins using a charged hydrogel microbead containing an agglomerate of gold nanoparticles. The Raman signal of the small molecules is selectively amplified by the agglomerate.
A Georgian Technical University (GTU) research group presented a molecular sensor with a microbead format for the rapid in-situ detection of harmful molecules in biological fluids or foods in a collaboration with a Georgian Technical University (GTU) research group.
As the sensor is designed to selectively concentrate charged small molecules and amplify the Raman signal no time-consuming pretreatment of samples is required.
Raman spectra (Raman spectroscopy is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified) are commonly known as molecular fingerprints. However their low intensity has restricted their use in molecular detection, especially for low concentrations. Raman signals can be dramatically amplified by locating the molecules on the surface of metal nanostructures where the electromagnetic field is strongly localized.
However it is still challenging to use Raman signals (Raman spectroscopy is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified) for the detection of small molecules dissolved in complex biological fluids. Adhesive proteins irreversibly adsorb on the metal surface which prevents the access of small target molecules onto the metal surface.
Therefore it was a prerequisite to purify the samples before analysis. However it takes a long time and is expensive.
A joint team from Professor X’s group in Georgian Technical University and Dr. Y’s group in Georgian Technical University has addressed the issue by encapsulating agglomerates of gold nanoparticles using a hydrogel.
The hydrogel has three-dimensional network structures so that molecules smaller than the mesh are selectively permeable. Therefore the hydrogel can exclude relatively large proteins while allowing the infusion of small molecules. Therefore the surface of gold nanoparticles remains intact against proteins which accommodates small molecules.
In particular the charged hydrogel enables the concentration of oppositely-charged small molecules. That is the purification is autonomously done by the materials removing the need for time-consuming pretreatment.
As a result the Raman signal (Raman spectroscopy is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified) of small molecules can be selectively amplified in the absence of adhesive proteins.
Using the molecular sensors the research team demonstrated the direct detection of fipronil sulfone dissolved in an egg without sample pretreatment. Recently insecticide-contaminated eggs have spread and other countries threatening health and causing social chaos.
Fipronil is one of the most commonly used insecticides for veterinary medicine to combat fleas. The fipronil is absorbed through the chicken skin from which a metabolite fipronil sulfone accumulates in the eggs.
As the fipronil sulfone carries partial negative charges it can be concentrated using positively-charged microgels while excluding adhesive proteins in eggs such as ovalbumin, ovoglobulin and ovomucoid.
Therefore the Raman spectrum (Raman spectroscopy is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified) of fipronil sulfone can be directly measured. The limit of direct detection of fipronil sulfone dissolved in an egg was measured at 0.05 ppm.
X says “The molecular sensors can be used not only for the direct detection of harmful molecules in foods but also for residual drugs or biomarkers in blood or urine”. Dr. Y adds “It will be possible to save time and cost as no sample treatment is required”.