Nanoparticle-Mediated Capture and Electrochemical Detection of

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Nanoparticle-Mediated Microfluidic Capture and Electrochemical Detection of Methicillin-Resistant Staphylococcus Aureus Carine R. Nemr, Sarah J. Smith, Wenhan Liu, Adam H. Mepham, Reza M Mohamadi, Mahmoud Labib, and Shana O. Kelley Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.8b04792 • Publication Date (Web): 24 Jan 2019 Downloaded from http://pubs.acs.org on January 25, 2019

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Analytical Chemistry

Nanoparticle-Mediated Microfluidic Capture and Electrochemical Detection of Methicillin-Resistant Staphylococcus Aureus Carine R. Nemr‡, Sarah J. Smith⊥†, Wenhan Liu§, Adam H. Mepham§, Reza M. Mohamadi⊥, Mahmoud Labib⊥, Shana O. Kelley*‡⊥§ ‡Department

of Chemistry, Faculty of Arts and Science, ⊥Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, §Institute for Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3M2, Canada ABSTRACT: The spread of antibiotic-resistant bacteria poses a global threat to public health. Conventional bacterial detection and identification methods often require pre-enrichment and/or sample preprocessing and purification steps that can prolong diagnosis by days. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most widespread antibiotic-resistant bacteria and is the leading cause of hospital-acquired infections. Here, we have developed a method to specifically capture and detect MRSA directly from patient nasal swabs with no prior culture and minimal processing steps using a microfluidic device and antibodyfunctionalized magnetic nanoparticles. Bacteria are captured based on antibody recognition of a membrane-bound protein marker that confers β-lactam antibiotic resistance. MRSA identification is then achieved by the use of a strain-specific antibody functionalized with alkaline phosphatase for electrochemical detection. This approach ensures that only those bacteria which belong to the correct strain and resistance profile are measured. The method has a limit of detection of 845 CFU/mL and excellent discrimination against high concentrations of common non-target nasal flora in under 4.5 hours. This detection method was successfully validated using clinical nasal swab specimens (n= 30) and has the potential to be tailored to various bacterial targets. Hospital-acquired infections are among the leading causes of death worldwide. In the United States, approximately 2 million patients suffer from hospitalacquired infections, with about 4.5% of cases leading to death.1 Methicillin-resistant Staphylococcus aureus (MRSA) is the most common cause of severe hospitalacquired infections and community-acquired infections.2,3 Timely detection of MRSA is critical i) for appropriate antibiotics to be administered, ii) to reduce the spread of infection and iii) to improve patient outcomes.4,5 Routine clinical MRSA screening often occurs via nasal swab, as nostrils are a primary site of S. aureus colonization and nasal carriage is recognized to be a main risk factor for infection.6–9 Direct detection of bacteria is complicated by the heterogeneity of nasal matrices and the low bacterial counts collected by swabs. Conventional clinical approaches for bacterial identification (ID) and antibiotic-susceptibility testing (AST) include culturing on selective agar10, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS)11–13, polymerase chain reaction (PCR) 5,14–16 and latex agglutination tests.17 Many of these techniques rely on pre-enrichment to increase bacterial counts and to isolate pure colonies, which delays diagnosis by anywhere between 24 hours and a few days.5 Due to the lag between sample collection and patient diagnosis, there is a large demand to develop simple and

rapid diagnostic techniques that can measure clinically relevant levels of bacteria directly from patient samples. Penicillin-binding protein 2a (PBP2a) causes methicillin resistance in S. aureus and is encoded by the mecA gene. 18 As a result, mecA is often employed to detect MRSA, alongside S. aureus-specific genes. This method of detection is susceptible to false-positive results caused by bacterial strains harboring antibiotic-resistance genes but not expressing the corresponding proteins. Consequently, additional phenotypic testing is required to confirm diagnosis.19–22 The ability to directly detect protein markers conferring antibiotic resistance,23,24 or performing AST by measuring bacterial growth in the presence of antibiotics, can circumvent this25,26; yet, such approaches cannot distinguish between different strains that express the same antibiotic-resistance markers.17–19 As a result, further tests are required for strain ID, increasing the cost and time to diagnosis.27 Recent work has demonstrated the promise of microfluidic approaches for bacterial detection platforms through simplifying user input, concentrating targets in reduced volumes for growth and increasing the rate of biochemical reactions.25,28–30 Microfluidic bacterial sensing platforms utilizing DNA amplification methods to simultaneously detect strain-specific and antibioticresistance genetic markers can be rapid and have shown excellent sensitivity.31–36 However, requirements for precise temperature control and genomic DNA extraction

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Analytical Chemistry detection. Samples are incubated with magnetic nanoparticles (MNPs) with anti-PBP2a antibodies and flowed through the capture device in the presence of a magnetic field. Upon capture, MRSA is detected electrochemically in a sandwich assay using an alkaline phosphatase (ALP)-functionalized anti-S. aureus antibodies. The device provides a portable and miniaturized platform for AST and ID of MRSA from nasal swabs in a single test in less than 4.5 hours, with limited sample preprocessing.

necessitate additional instrumentation and complex fabrication, ultimately increasing costs. In contrast, pairing microfluidic devices with electrochemical detection methods, which use simple, sensitive and relatively inexpensive instrumentation, can be advantageous for lowcost bacteria detection platforms.37–40 Here, we have developed a microfluidic platform to capture MRSA directly from nasal swabs, without preenrichment, based on its expression of membrane-bound PBP2a, followed by strain specific electrochemical

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Figure 1. Bacterial capture and electrochemical detection. A) Schematic of bacterial capture device fabricated in PDMS. B) Flow profile of capture device simulated on COMSOL Multiphysics. X-shaped features create areas of reduced flow velocity. C) Photograph of bacterial capture device filled with food colouring in the absence and presence of an array of external magnets (above and below images, respectively). Scale is 10 mm. D) Filtered nasal swab specimen is incubated with anti-PBP2a MNPs for one hour. The solution is then flowed through the device, where magnetically-labelled bacteria are captured in areas of low flow velocity. After wash steps, anti-S. aureus antibodies functionalized with ALP are flowed through the device and washed. E) The substrate p-APP is introduced to the device, where it is converted to electrochemically active p-AP by ALP. p-AP is oxidized to quinonimine at a potential of 10 mV against a gold reference electrode. F) Schematic (left) and photograph (right) of electrochemical detector chip. A PDMS channel allows simple transfer of


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Analytical Chemistry electrochemical readout solution from the capture device. Detection utilizes on-chip working and reference gold electrodes and an external Pt counter electrode. Scale is 10 mm. G) Differential pulse voltammogram displaying signal from p-APP (blue) and p-AP (red). The measured current correlates to number of captured bacteria.

EXPERIMENTAL SECTION Materials. Acetone, isopropyl alcohol (IPA), Pluronic F68, bovine serum albumin (BSA), Tween® 20, sodium chloride, magnesium chloride solution (1.00 M), Trishydrochloride, tryptic soy broth (TSB), Mueller-Hinton agar and 3 µm hydrophilic Isopore™ membrane filters were purchased from Millipore Sigma, MO. 1x phosphate buffered saline (PBS), granulated agar, oxacillin discs (1 mcg), Oxoid™ PBP2’ latex agglutination test kit were obtained from Thermofisher Scientific, MA. Paraformaldehyde, glutaraldehyde, sodium cacodylate, osmium tetroxide, propylene oxide and Quetol-Spurr were purchased from Electron Microscopy Sciences, PA. Ethanol was acquired from Commercial Alcohols, Canada. Anti-biotin microbeads (50 nm magnetic nanoparticles, MNPs) and MACs LS Columns were procured from Miltenyi Biotec, CA. A Chemicell MagnetoPURE Separator was obtained from Chemicell, Germany. Alkaline phosphatase (ALP) conjugation kit and p-aminophenyl phosphate (p-APP) monosodium salt were acquired from Abcam, MA. ESwab™ Liquid Amies collection and transport system was purchased from Copan, CA. Silicone glue (Dow Corning 3145 RTV Clear) and polydimethyl siloxane (PDMS, Sylgard 184 silicone elastomer kit) were procured from Dow Corning, MI. Rabbit polyclonal antipenicillin binding protein 2a (PBP2a) [+biotin] (13010073B-50) was obtained from Ray Biotech, GA. Rabbit polyclonal Staphylococcus aureus antibody (20CCR1274RP) was obtained from Fitzgerald, MA. NdFeB N52 magnets (1/16” diameter by 1/4” thick) were purchased from KJ Magnetics, PA. HelixMark standard silicon tubing was procured from Freudenberg medical, CA. Positive photoresist coated gold-chromium-glass wafers were acquired from Telic, CA. SU-8 2100, SU-8 2002 and SU-8 3050 were purchased from Microchem, MA. Silicon wafers were obtained from University Wafer, MA. Bacterial culture. Uninduced methicillin-susceptible S. aureus (MSSA, ATCC 29213), methicillin-resistant S. aureus (MRSA, ATCC 43300), methicillin-susceptible S. epidermidis (MSSE, ATCC 14990) and methicillinresistant S. epidermidis (MRSE, ATCC 51625) were cultured on tryptic soy agar (TSA) for 24 hours at 37ºC. Induced bacteria were cultured on Mueller-Hinton agar with a 1 mcg oxacillin disc. Bacteria were spiked and diluted in Amies media. Techniques including optical density measurements of solutions at 600 nm, serial dilutions and culture growth on TSA plates were used to obtain colony forming unit (CFU) counts. PBP2a latex agglutination test. PBP2a latex agglutination tests were performed on induced bacteria following kit manufacturer instructions. SU-8 master mold fabrication. The capture device master mold (250 µm thick) was made on a silicon wafer

using two spin coat cycles with SU-8 2100 (3000 RPM, 30 seconds). After the first spin coating step, the wafer was softbaked for 25 minutes at 95 ˚C. The wafer was softbaked for an additional 30 minutes at 95 ˚C after the second spin coating step. The electrochemical chip channel master mold (100 µm thick) was made on a silicon wafer with SU-8 3050 (1000 RPM, 30 seconds) and was softbaked for 45 minutes at 95 ˚C. Features were patterned on the master molds by standard photolithographic methods using a MA6 Mask Aligner (Suss MicroTec, Germany). Wafers were postbaked and developed with manufacturer recommended times based on thickness. Microfluidic capture device fabrication. PDMS (1:10 curing agent to base) microfluidic capture devices were fabricated using soft-lithography processes with the capture device master mold. The PDMS capture devices were pierced for inlet and outlet tubing connections and plasma treated with the power setting on high (Plasma Cleaner PDC-32G, Harrick Plasma, NY) for bonding to a PDMS-coated glass slide. Tubing was inserted into the device and sealed with silicon glue. Capture devices were treated with 1% Pluronic F68 in 0.1x PBS overnight to limit non-specific adsorption and washed with 1x PBS prior to use. Electrochemical detector chip fabrication. Standard photolithographic methods were employed to fabricate electrochemical detector chips. Briefly, seven gold working electrodes (0.45mm x 0.34 mm) and a gold reference (8.96 mm x 0.47 mm) electrode were patterned on glass wafers and were passivated with SU-8 2002. On the day of measurements, electrodes were washed with acetone, IPA and ddH2O, dried with N2 and cleaned with plasma with the power setting on high for 1 minute. A plasma-treated PDMS microfluidic channel, fabricated using the electrochemical chip channel master mold, was glued to the electrochemical chip and tubing was inserted into the inlet and outlet. Antibody functionalization. MNPs functionalized with capture antibodies were prepared by incubating antibiotin MNPs with biotinylated rabbit anti-PBP2a antibodies (100 µg/mL) at a volume ratio of 10:1 for 1 hour at room temperature. Detection antibodies, rabbit polyclonal anti-S. aureus, were functionalized with ALP using a conjugation kit as instructed by the manufacturer. Bacterial capture and detection. Samples containing either bacteria spiked in Amies media or nasal swabs collected in Amies media were incubated with 5 µL antiPBP2a MNPs per mL of sample for 1 hour. Samples were introduced at 0.6 mL/hr into capture devices that were sandwiched between arrays of NdFeB magnets with alternating polarity using a syringe pump (Chemyx, TX). Devices were washed three times with a solution of 0.1%


Analytical Chemistry Tween® 20 and 1% BSA in 1x PBS (wash buffer; 0.1 mL, 0.6 mL/hr). Anti-S. aureus-ALP diluted in wash buffer (1 µg/mL) was introduced into the devices (0.1 mL, 0.3 mL/hr). Devices were washed three times using wash buffer (0.1 mL, 0.6 mL/hr) and flushed with 50mM TrisHCl, 10 mM NaCl, 10 mM MgCl2, pH 9.0 (TSB; 0.1 mL; 0.6 mL/hr). A readout solution containing 0.5 mM p-APP in TBS, introduced to the device in fresh uncontaminated tubing, was incubated 5 minutes before being transferred to the electrochemical detector chip, via fresh tubing, for electrochemical measurements. Capture efficiency experiments. Bacteria were spiked into Amies media and colony counts were obtained using TSA plates. Dilutions were performed as necessary to obtain single bacterial colonies that numbered in a countable range.41 The initial bacteria counts (Ci) were obtained by plating aliquots of samples prior to incubation with MNPs. Bacteria incubated with antiPBP2a MNPs for 1 hour were introduced to the capture device under a magnetic field and washed three times with wash buffer to remove uncaptured bacteria. Uncaptured bacteria counts (Cu) were obtained by plating bacteria collected from the device outlet after the washing. MNPs do not significantly affect bacteria viability (Figure SI-1). Capture efficiency was calculated as:

% capture efficiency = (𝐶𝑖 ― 𝐶𝑢)/𝐶𝑖 ∗ 100 where Ci is initial bacteria count and Cu is uncaptured bacteria count. Dilution factors were taken into account when performing calculations. Transmission electron microscopy (TEM) imaging. Bacteria spiked into 1x PBS (109 CFU/mL) were incubated with anti-PBP2a MNPs for 1 hour. Samples were then centrifuged at 5000 RPM for 5 minutes and washed with 1x PBS three times. Bacteria pellets were fixed with 2% paraformaldehyde and 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer pH 7.3 and post-fixed in 1% osmium tetroxide in 0.1M sodium cacodylate buffer pH 7.3. Samples were dehydrated in a graded ethanol series, followed by propylene oxide and embedded with Quetol-Spurr. Samples were sectioned (90 nm thick) with a Leica EM UC7 ultramicrotome (Leica Microsystems, Germany) and imaged using a FEI Tecnai 20TEM (ThermoFisher Scientific, OR). Electrochemical measurements. Electrochemical measurements were performed using an Epsilon Potentiostat (Bioanlytical Systems, Inc., IN) with on-chip gold working and reference electrodes and an external Pt counter electrode (0.2 mm diameter). Differential pulse voltammetry (DPV) was employed for signal acquisition using -200 mV to 200 mV potential scan, 50 ms pulse width, 50 mV pulse amplitude and 5 mV step interval. Analysis of clinical specimens. Patient nasal swab specimens were obtained from Mount Sinai Hospital (Toronto, Canada). Swab collection was performed using ESwab™ Liquid Amies collection and transport system (Copan, CA). Samples were cultured on denim blue agar

(Oxoid Co., Canada) for at 37 ˚C for 24 hours in the dark to differentiate MRSA-positive and -negative samples. Plates with blue colonies (MRSA-positive) were further analyzed by Matrix Assisted Laser Desorption Ionization Time-of-Flight mass spectrometry (MALDI-TOF MS) (VITEK® MS, BioMérieux, France) and MRSA latex test (Denka Seiken Co., LTD, Japan) to confirm methicillin resistance. Bacterial capture and detection using the described microfluidic platform were performed on the remaining sample volume within 48 hours of sample collection. Samples were filtered using 3 µm filter membranes prior to MNP incubation. Capture device flow profile simulation. The linear velocities experienced by the bacteria flowing through the capture device were simulated using COMSOL Multiphysics (COMSOL Inc., MA). RESULTS AND DISCUSSION Design of microfluidic capture system. A microfluidic device was designed for the capture and concentration of MRSA (Figure 1A) based on a chip previously reported for the capture of circulating tumor cells.42,43 This capture approach relies on an external magnetic field to overcome the drag force experienced by magnetically labelled targets as they flow through the device. X-shaped structures patterned in the PDMS capture device cause a reduction in the local fluid velocity (Figure 1B), decreasing the drag force experienced by bacteria flowing through the microfluidic channel.42 Magnets placed above and below the capture device (Figure 1C) exert a magnetic field to overcome the weakened drag force and lead to capture and concentration of magnetically-labelled bacteria. The microfluidic capture device improved bacteria capture efficiency compared to conventional magnetic separation using magnetic stands and columns (Figure SI-2). Furthermore, it allows for concentration of bacteria in a chip volume of

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induced bacteria, a strong positive result was observed for MRSA, a weak positive result was obtained using MRSE and MSSA/MSSE yielded negative results. Capture efficiency of MRSA and non-target bacteria. TEM imaging confirmed anti-PBP2a MNP binding to whole MRSA, compared to non-target bacteria (Figure 2A, SI-5). Specific MRSA capture in the microfluidic system was compared against MSSA, MSSE and MRSE bacterial strains. Capture efficiencies of 99% were achieved for MRSA counts between 103-105 CFU/mL (Figure 2B). Low nonspecific capture ( 12%) was observed for uninduced non-target bacteria at high concentrations (105 CFU/mL) (Figure 2B). Negligible

Figure 2. Bacterial capture and TEM images. A) TEM images of bacteria incubated with anti-PBP2a MNPs. Scale bar is 200 nm. B) MRSA capture efficiency at three concentrations. Non-target bacteria MSSA, MSSE and MRSE (uninduced and induced) capture efficiency at high concentration only. Error bars represent standard error, n=3.

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Prior to capture, samples containing spiked bacteria or nasal swabs collected in Amies media were incubated with anti-PBP2a functionalized MNPs (Figure 1D). The target, PBP2a, is the main source of β-lactam antibiotic resistance in MRSA and other bacterial strains such as MRSE.17–19 Furthermore, since PBP2a is membranebound, whole bacteria can be captured, which eliminates the need for bacterial lysis or further processing steps. Electrochemical assay for MRSA detection. Upon bacterial capture by targeting PBP2a, anti-S. aureus detection antibodies functionalized with ALP are used for electrochemical identification of MRSA (Figure 1D). Utilization of a strain-specific detection antibody leverages the selectivity of the assay, enabling this method to differentiate MRSA from other β-lactamresistant bacteria that may express PBP2a and be present in nasal swab specimens.18,44,45 The pairing of AST and bacterial strain ID reduces the need to perform multiple laboratory tests, reducing costs and diagnostic times.27 Upon conjugation with detection antibodies, captured bacteria are incubated with p-APP, which is converted to electrochemically active p-aminophenol (p-AP) by ALP (Figure 1E). After 5 minutes of incubation at room temperature, the electrochemically active solution is transferred from the capture device to the detection chip comprised of a microfluidic channel on top of patterned gold reference and working electrodes (Figure 1F). A Pt reference electrode is placed in the inlet of the detection chip to complete the electrochemical cell during measurements. Physical separation of the electrodes from the biological components, which remain in the capture device, prevents fouling of electrode surfaces and improve signal-to-noise of current measurements. Electrochemical signals resulting from the oxidation of the p-AP product are detected by differential pulse voltammetry, with current measurements correlating with MRSA concentration (Figure 1G, SI-3). Selection of bacterial strains for validation. The selectivity of the assay for MRSA capture and detection was assessed using three closely related non-target bacterial strains commonly found in nasal cavities including MSSA, MSSE and MRSE.46,47 Antibiotic susceptibility and resistance in each strain was confirmed by oxacillin disc diffusion tests (Figure SI-4A) and PBP2a latex agglutination tests (Figure SI-4B). MRSE, a coagulase-negative staphylococcus, commonly exhibits low PBP2a expression and requires induction via penicillinase-resistant penicillins, such as oxacillin, to increase PBP2a production.18,44 Induced and uninduced MRSE were employed in experiments, as specified. Based on the PBP2a latex agglutination tests, performed on

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agglutination tests. MRSA was detected directly from filtered swabs using the detection platform.

Figure 3. Assay sensitivity and specificity. A) Assay selectivity of MRSA against non-target bacteria (MSSA, MSSE, MRSE) at concentrations of 105 CFU/mL. B) Assay sensitivity of MRSA detection at concentrations of 103-105 CFU/mL. Dotted line represents limit of detection. C) Assay selectivity for MRSA (103 CFU/mL) in the presence of non-target bacteria (105 CFU/mL). Error bars represent standard error, n=3.

To ensure selective MRSA detection, electrochemical signals were obtained under incubation with high concentrations (105 CFU/mL) of pure MSSA, MSSE and MRSE (both uninduced and induced) cultures (Figure 3A, SI-6). These current measurements were below the limit of detection, confirming assay specificity in the presence of high concentrations of non-target bacterial species commonly found in nasal cavities. Furthermore, electrochemical measurements were obtained for low concentrations of MRSA in the presence of high concentrations of non-target bacteria (Figure 3C), confirming minimal signal interference from non-target bacteria. Validation with patient nasal swab specimens. Human nasal swab specimens collected in Amies media using the Copan ESwab system were employed to assess the performance of the MRSA detection platform. A total of 30 aliquots of MRSA-positive and -negative nasal swab samples were acquired from Mount Sinai Hospital (Toronto, Canada). Clinical analysis of nasal swabs was done through routine testing consisting of culturing on chromogenic MRSA screening agar, MALDI-TOF MS and PBP2a latex agglutination testing (summarized in Table 1 for samples tested blindly on the MRSA detection platform and Table SI-1 with samples used to establish a threshold for the MRSA detection platform). Remaining sample volumes were tested using the developed assay within 48 hours of collection. Prior to incubation with anti-PBP2a MNPs, nasal swab specimens were filtered using 3 m Isopore membranes to remove large debris that may obstruct flow and cause fouling of the device. The MRSA loss by filtration with these membranes is

Inducing MRSE with oxacillin to increase PBP2a expression caused its capture efficiency to increase to approximately 35% at 105 CFU/mL (Figure 2B). Even with induction, low capture efficiency was likely attributed to heterogeneous and weak PBP2a expression.18,44 Weak PBP2a expression was confirmed by the latex agglutination test (Figure SI-4B). Despite increased capture upon MRSE induction, specificity of the detection antibody for S. aureus prevented false-positive results (Figure 3A). Sensitivity and specificity of MRSA detection. Electrochemical measurements were performed using MRSA concentrations between 103-105 CFU/mL. A limit of detection (blank + 3 standard deviations) of 845 CFU/mL was established (Figure 3B). Reported clinical MRSA nasal burdens vary broadly.48,49 Two studies of note measured a median of 2.14 x 104 CFU/nostril and 708 CFU/nares culture, respectively. It is likely that specimen quantification will vary significantly based on sampling conditions.48,50 The MRSA detection platform developed here is not sensitive enough to detect the lowest reported levels of bacterial load, but was validated with clinical samples and was in good agreement with much lengthier detection methods. Table 1. MRSA detection in patient nasal swab specimens.

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Figure 4. MRSA detection in blinded patient nasal swab specimens using detection platform. MRSA was detected directly from filtered swabs using the detection platform. Dotted line represents cut-off value established using unblinded patient data (Figure SI-6).


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Analytical Chemistry Out of the 30 aliquots of patient specimens received, 11 were MRSA-positive and 19 MRSA-negative. 11 randomly chosen MRSA-negative specimens were used to empirically establish a current threshold accounting for matrix effects (Table SI-1, Figure SI-7) and 5 additional randomly selected MRSA-positive samples were used to validate the cutoff threshold. Afterwards, the platform was challenged to blinded tests using 14 patient specimens (6 positive and 8 negative) and produced good agreement with clinical analyses (Figure 4). These results show promise for the developed MRSA detection platform to guide clinical decisions for antibiotic selection, though further validation with a larger sample size is necessary to accurately assess analytical figures of merit. CONCLUSIONS We have developed a MRSA detection platform that pairs microfluidic bacterial capture and concentration with electrochemical detection. This method has shown specificity and sensitivity for MRSA detection compared to non-target bacterial strains in spiked Amies media in under 4.5 hour. The resistance-based capture followed by strain-specific detection provides antibiotic susceptibility testing and strain identification in a single test. Furthermore, the platform was validated for MRSA detection directly from pre-filtered clinical nasal swab specimens. This portable detection platform can be operated using simple instrumentation and only requires filtration for sample preprocessing, eliminating time and labor-intensive steps that are necessary for conventional methods. The platform can also easily be modified to capture various bacterial strains of interest by selecting appropriate capture and detection antibody pairs.

Research council (Postgraduate Scholarship- Doctoral Program). Research reported in this publication was supported in part by the Canadian Institutes of Health Research (grant no. FDN-148415), the Natural Sciences and Engineering Research Council of Canada (grant no. RGPIN-2016-06090). Authors wish to thank Dr. Tony Mazzulli at Mount Sinai Hospital for access to clinical samples.

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ASSOCIATED CONTENT Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website. SI Figure 1, determination of antibiotic resistance in bacterial strains used for device validation; SI Figure 2, capture efficiency and electrochemical detection of MRSE cultured in the absence (uninduced) and presence (induced) of antibiotics. (PDF)

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AUTHOR INFORMATION Corresponding Author

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* Email: [email protected]

Present Addresses † Department

of Chemistry, Bucknell University, Lewisburg PA

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17837, USA

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

ACKNOWLEDGMENTS C.R.N acknowledges support from the Walter C. Sumner Memorial Fellowship and the Natural Sciences and Engineering

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Perl, T. M.; et al. Quantitative Analysis and Molecular Fingerprinting of Methicillin-Resistant Staphylococcus Aureus Nasal Colonization in Different Patient Populations: A Prospective, Multicenter Study. Infect. Control Hosp. Epidemiol. 2010, 31, 592–597. Smismans, A.; Verhaegen, J.; Schuermans, A.; Frans, J.

TOC Graphic MRSA -

Redox reporter

Redox signal

MRSA Nasal swab

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Magnetic capture

Potential


Nanoparticle-Mediated Capture and Electrochemical Detection of

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