Development of a Label-Free LSPR-Apta Sensor for Staphylococcus aureus Detection

Abstract

The risk of foodborne diseases has increased over the last years. We have developed a simple, portable, and label-free optical sensor via aptamer recognition of Staphylococcus aureus at nanostructured plasmonic elements. The developed aptamers conjugated to a localized surface plasmon resonance (LSPR) sensing device were applied in both pure culture and artificially contaminated milk samples enabling a limit of detection of 10 3 CFU/mL for S. aureus in milk. There was no need for a preenrichment step, and the total analysis time decreased from 30 min to 120 s. Finitedifference time-domain was used to simulate the experimentally measured optical responses for a range of different sensor designs (100 and 200 nm disks), addressing the role of the near field and intrinsic refractive index sensitivity. A comparison of the aptamer to antibody-based recognition approaches showed that the thickness of the sensing layer was critical with a significantly larger response for the thinner aptamer layer. Comparison of differently sized metal nanostructures showed a significantly higher sensitivity for 200 nm diameter compared to 100 nm diameter disk structures resulting from both increases in bulk refractive index sensitivity and the extent to which the local field extends out from the metal surface. These findings confirmed that the developed gold nanodisk-based LSPR sensing chips could facilitate sensitive detection of S. aureus in food samples.

Rapid point‐of‐need detection of bacteria and their toxins in food using gold nanoparticles

“…Recently, a portable, and label-free gold nanodisk-based LSPR sensing chip was reported for sensitive detection of S. aureus in milk (Khateb et al, 2020). The sensor performance was optimized through different designs specifically addressing the role of the near-field and intrinsic refractive index sensitivity.…”

Biosensing Applications Using Nanostructure-Based Localized Surface Plasmon Resonance Sensors

“…As mentioned above, the array pattern size, shape, and spacing affect the LSPR signal intensity. By taking advantage of the distinct size-, shape-, and spacing-dependent properties of these materials, periodically ordered arrays have been used for the fabrication of flexible, tunable, uniform 3D structure-based platforms [ 67 , 68 , 69 , 70 , 71 , 72 ]. For example, a recent study reported the synthesis of an inverted ‘L’-shaped nanostructure with a nanograting pattern consisting of an Au-deposited portion on the top and a PDMS layer on the sidewall surface ([ 54 ]; Figure 3 A).…”

“…Anti-human IgG antibodies were attached to an as-prepared platform, resulting in a 1.5 μg/mL limit of detection. Arrays of Au nanodisks with uniform and tunable structure were also fabricated on polymethylmethacrylate (PMMA) on glass substrate and applied to detect bacterial cells of Staphylococcus aureus in milk [ 72 ]. Varying diameters of Au disks could be achieved by using hole-mask colloidal lithography, in which PS was used as a mask to fabricate arrays of Au disks.…”

Aptasensors for Staphylococcus aureus Risk Assessment in Food

“…The aptamer was applied to detect S. aureus in milk by resonance combination with localized surface plasmon resonance (LSPR). It should be pointed out that the LOD of aptasensors was 10 3 CFU/ml, and the analysis time was only 120 s ( Khateb et al, 2020 ).…”