An interferometric reflectance imaging sensor for point of care viral diagnostics

Abstract

The use of in vitro diagnostic devices is transitioning from the laboratory to the primary care setting to address early disease detection needs. Time critical viral diagnoses are often made without support due to the experimental time required in today's standard tests. Available rapid point of care (POC) viral tests are less reliable, requiring a follow-on confirmatory test before conclusions can be drawn. The development of a reliable POC viral test for the primary care setting would decrease the time for diagnosis leading to a lower chance of transmission and improve recovery. The single particle interferometric reflectance imaging sensor (SP-IRIS) has been shown to be a sensitive and specific-detection platform in serum and whole blood. This paper presents a step towards a POC viral assay through a SP-IRIS prototype with automated data acquisition and analysis and a simple, easy-to-use software interface. Decreasing operation complexity highlights the potential of SP-IRIS as a sensitive and specific POC diagnostic tool. With the integration of a microfluidic cartridge, this automated instrument will allow an untrained user to run a sample-to-answer viral assay in the POC setting.

Fig. 1

(a) Image of the prototype. (b) Patterned chip loaded into the sample holder. The center square region is for spotting. (c) Image of an antibody spot on the prototype.

Fig. 2

Interferometric particle response. Simulated response of viral nanoparticles to a 528 nm center wavelength source. A contrast of one corresponds to an unperturbed background response.

Fig. 3

Theoretical response of a 100 nm virus when the NA of the objective is varied. The dashed horizontal bar indicates an SNR of three above the background noise. The dotted vertical line indicates the selected NA, 0.8.

Fig. 4

User Interface. The software shown here simplifies acquisition and analysis for untrained to minimally trained users. The user defines the array geometry (array size and spot pitch), loads the sensor chip, and then clicks once for acquisition and analysis. When the instrument finishes, results are reported in the table and saved into a spreadsheet. Additional functionalities are included in other tabs for advanced users but not required for typical operation.

Fig. 5

Simulated response of a 100 nm spherical viral particle in the SP-IRIS system.

Fig. 6

Nanoparticle filtering at artifact edges is illustrated with these cropped images. (a) Expected gradient behavior is relaxed leading to a large number of false signals near the artifact edge. (b) Tightening the constraint eliminates these false-edge signals

Fig. 7

Anomaly Filtering. (a) Detected anomaly map of nonspecific structures. (b) Using the anomaly map to discard particles within those regions, the nanoparticles of interest (green circles) are accurately identified.

Fig. 8

Simulated response of a 100 nm spherical virus at different z-planes. The sensor surface is defined as z = 0. The detectable window (contrast > 1.02) is between −700 and 500 nm with the peak response occurring at −100 nm.

Fig. 9

Specific virus capture and detection. The panels show detection of wtVSV (circled in green) for 0 and 10⁶ PFU/ml concentrations in 65 μm × 65 μm area.

Fig. 10

Benchmark comparison for 5 × 10⁵ PFU/mL of wtVSV. Identical areas of the wtVSV antibody and controls spots were analyzed on the prototype and laboratory SP-IRIS platforms. The number of particles detected between 90 and 140 nm were tallied. The mean and standard deviation for each condition were determined from particle counts on five replicate spots.