Multiplexed detection and quantification of human antibody response to COVID-19 infection using a plasmon enhanced biosensor platform

The 2019 SARS CoV-2 (COVID-19) pandemic has illustrated the need for rapid and accurate diagnostic tests. In this work, a multiplexed grating-coupled fluorescent plasmonics (GC-FP) biosensor platform was used to rapidly and accurately measure antibodies against COVID-19 in human blood serum and dried blood spot samples. The GC-FP platform measures antibody-antigen binding interactions for multiple targets in a single sample, and has 100% selectivity and sensitivity (n = 23) when measuring serum IgG levels against three COVID-19 antigens (spike S1, spike S1S2, and the nucleocapsid protein). The GC-FP platform yielded a quantitative, linear response for serum samples diluted to as low as 1:1600 dilution. Test results were highly correlated with two commercial COVID-19 antibody tests, including an enzyme linked immunosorbent assay (ELISA) and a Luminex-based microsphere immunoassay. To demonstrate test efficacy with other sample matrices, dried blood spot samples (n = 63) were obtained and evaluated with GC-FP, yielding 100% selectivity and 86.7% sensitivity for diagnosing prior COVID-19 infection. The test was also evaluated for detection of multiple immunoglobulin isotypes, with successful detection of IgM, IgG and IgA antibody-antigen interactions. Last, a machine learning approach was developed to accurately score patient samples for prior COVID-19 infection, using antibody binding data for all three COVID-19 antigens used in the test.

Hot Electron Driven Photocatalysis on Plasmon-Resonant Grating Nanostructures

We demonstrate the hot electron injection of photoexcited carriers in an Ag-based plasmon resonant grating structure. By varying the incident angle of irradiation, sharp dips are observed in the reflectance with p-polarized light (electric field perpendicular to grating lines) when there is wavevector matching between the incident light and the plasmon resonant modes of the grating and no angle dependence is observed with s-polarized light. This configuration enables us to compare photoelectrochemical current produced by plasmon resonant excitation with that of bulk metal interband absorption simply by rotating the polarization of the incident light while keeping all other parameters of the measurement fixed. With 633 nm light, we observed a 12-fold enhancement in the photocurrent (i.e., reaction rate) between resonant and nonresonant polarizations at incident angles of ±7.6° from normal. At 785 nm irradiation, we observed similar resonant profiles to those obtained with 633 nm wavelength light but with a 44-fold enhancement factor. Using 532 nm light, we observed two resonant peaks (with approximately 10× enhancement) in the photocurrent at 19.4° and 28.0° incident angles, each corresponding to higher order modes in the grating with more nodes per period. The lower enhancement factors observed at shorter wavelengths are attributed to interband transitions, which provide a damping mechanism for the plasmon resonance. Finite difference time domain (FDTD) simulations of these grating structures confirm the resonant profiles observed in the angle-dependent spectra of these gratings and provide a detailed picture of the electric field profiles on and off resonance.

A fluorescent plasmonic biochip assay for multiplex screening of diagnostic serum antibody targets in human Lyme disease

Lyme disease (LD) diagnosis using the current two-tier algorithm is constrained by low sensitivity for early-stage infection and ambiguity in determining treatment response. We recently developed a protein microarray biochip that measures diagnostic serum antibody targets using grating-coupled fluorescent plasmonics (GC-FP) technology. This strategy requires microliters of blood serum to enable multiplexed biomarker screening on a compact surface and generates quantitative results that can be further processed for diagnostic scoring. The GC-FP biochip was used to detect serum antibodies in patients with active and convalescent LD, as well as various negative controls. We hypothesized that the quantitative, high-sensitivity attributes of the GC-FP approach permit: 1) screening of antibody targets predictive for LD status, and 2) development a diagnostic algorithm that is more sensitive, specific, and informative than the standard ELISA and Western blot assays. Notably, our findings led to a diagnostic algorithm that may be more sensitive than the current standard for detecting early LD, while maintaining 100% specificity. We further show that analysis of relative antibody levels to predict disease status, such as in acute and convalescent stages of infection, is possible with a highly sensitive and quantitative platform like GC-FP. The results from this study add to the urgent conversation regarding better diagnostic strategies and more effective treatment for patients affected by tick-borne disease.

Hot electron-driven photocatalysis and transient absorption spectroscopy in plasmon resonant grating structures

We have developed a method to measure photocurrents produced by photoexcited hot electrons and holes in bulk metal films.

Development of an inservice educational program for clinical staff

Inservice education is potentially one of the most effective tools of the clinical engineer. A good technical inservice program can significantly reduce the amount of time engineers and technicians must spend on repetitive, corrective tasks, allowing them to be of greater value to their institutions in more creative ways. A complete technical inservice education program has been designed for the University of Connecticut Health Center's John Dempsey Hospital. To design such a program, one must first assess current inservice practices and any associated problems, as well as the educational needs of the clinical staff. The assessment is done by examining past equipment repair records, and by surveying nurses and other clinicians within the hospital, clinical engineers from outside hospitals, and equipment vendors. A sample program is then carried out to gather additional information and gain the acceptance and support of key hospital personnel. Based on the compiled data, an inservice program is proposed that is streamlined to maintain a desirable level of efficacy without requiring an inordinate amount of time. Quantitative analyses of costs and benefits confirm that the proposed program will have a net positive effect.

Setting up a clinical engineering department

The problems of cost, personnel qualifications, task assignment, and productivity involved in establishing a clinical engineering department are addressed in this paper. A basic department consisting of a Clinical Engineer, a Biomedical Equipment Technician, a Testing Technician and a Clerical Assistant can provide a full range of clinical engineering services to a hospital with 225 instruments. The annual cost of such a department, including materials, would be approximately $90,000. The average capital investment in a selection of 225 instruments would be on the order of $860,000. This paper discusses levels of skills within a clinical engineering department, and the services that a hospital could expect from a four-man department.