Abstract
Urinary tract infections (UTIs) are one of the major burdens on public healthcare worldwide. One of the primary causes of UTIs is the invasion of the urinary tract by uropathogenic Escherichia coli (UPEC). Improper treatment of bacterial infections like UTIs with broad-spectrum antibiotics has contributed to the rise of antimicrobial resistance, necessitating the development of an inexpensive, rapid and accurate detection of UPEC. Here, we present real-time, selective and label-free detection of UPEC using crossed surface-relief gratings (CSRGs) as nanometallic sensors incorporated into an optical sensing platform. CSRGs enable real-time sensing due to their unique surface plasmon resonance (SPR)-based light energy exchange, resulting in detection of a very-narrow-bandwidth SPR signal after the elimination of residual incident light. The platform’s sensing ability is experimentally demonstrated by the detection of bulk refractive index (RI) changes, with a bulk sensitivity of 382.2 nm/RIU and a resolution in the order of 10−6 RIU. We also demonstrate, for the first time, CSRG-based real-time selective capture and detection of UPEC in phosphate-buffered saline (PBS) solution, in clinically relevant concentrations, as opposed to other UTI-causing Gram-negative bacteria. The platform’s detection limit is calculated to be 105 CFU/mL (concentration on par with the clinical threshold for UTI diagnosis), with a dynamic range spanning four orders of magnitude. This work paves the way for the development of inexpensive point-of-care diagnosis devices focusing on effective treatment of UTIs, which are a burden on public healthcare due to the rise in the number of cases and their recurrences in the recent past.
Highlights
Urinary tract infections (UTIs) are one of the most common bacterial infections worldwide.These infections are associated with escalating healthcare costs, with an estimated 10.5 million hospital visits in the United States alone in 2007, resulting in a direct and nondirect healthcare expenditure of overSensors 2018, 18, 3634; doi:10.3390/s18113634 www.mdpi.com/journal/sensors$2 billion [1,2]
crossed surface-relief gratings (CSRGs) is attributed to the surface plasmon resonance (SPR) energy conversion occurring between the individual surface-relief gratings (SRGs)
For CSRGs, the SPR energy conversion occurs at λSPR when the light momentum is phase-matched between the diffracted incident light and the surface plasmon
Summary
Urinary tract infections (UTIs) are one of the most common bacterial infections worldwide.These infections are associated with escalating healthcare costs, with an estimated 10.5 million hospital visits in the United States alone in 2007, resulting in a direct and nondirect healthcare expenditure of overSensors 2018, 18, 3634; doi:10.3390/s18113634 www.mdpi.com/journal/sensors$2 billion [1,2]. Urinary tract infections (UTIs) are one of the most common bacterial infections worldwide. These infections are associated with escalating healthcare costs, with an estimated 10.5 million hospital visits in the United States alone in 2007, resulting in a direct and nondirect healthcare expenditure of over. UPEC detection in laboratories usually involves biochemical assays like nitrite and/or esterase tests using serological techniques, which suffer from a high probability of false-positive results [7]. Other detection techniques involve established urine culture analysis, which is time consuming (3 to 7 days), laborious and requires specialized laboratory technicians to perform [8]. Genome-based detection techniques employing polymerase chain reaction (PCR) have brought the timeline of detection to a few hours [8]
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