key: cord-0204922-8ijw1okd
authors: Wu, Kai; Chugh, Vinit Kumar; Girolamo, Arturo di; Liu, Jinming; Saha, Renata; Su, Diqing; Krishna, Venkatramana D.; Nair, Abilash; Davies, Will; Wang, Andrew Yongqiang; Cheeran, Maxim C-J; Wang, Jian-Ping
title: Portable Magnetic Particle Spectrometer (MPS) for Future Rapid and Wash-free Bioassays
date: 2020-11-20
journal: nan
DOI: nan
sha: c6aa41e03fc4f9a798b119476cbec7914b9d4a94
doc_id: 204922
cord_uid: 8ijw1okd

Nowadays, there is an increasing demand for more accessible routine diagnostics for patients with respect to high accuracy, ease of use, and low cost. However, the quantitative and high accuracy bioassays in large hospitals and laboratories usually require trained technicians and equipment that is both bulky and expensive. In addition, the multi-step bioassays and long turnaround time could severely affect the disease surveillance and control especially in pandemics such as influenza and COVID-19. In view of this, a portable, quantitative bioassay device will be valuable in regions with scarce medical resources and help relieve burden on local healthcare systems. Herein, we introduce the MagiCoil diagnostic device, an inexpensive, portable, quantitative and rapid bioassay platform based on magnetic particle spectrometer (MPS) technique. MPS detects the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses the harmonics from oscillating MNPs as metrics for sensitive and quantitative bioassays. This device does not require trained technicians to operate and employs a fully automatic, one-step, wash-free assay with user friendly smartphone interface. Using a streptavidin-biotin binding system as a model, we show that the detection limit of the current portable device for streptavidin is 64 nM (equal to 5.12 pmole). In addition, this MPS technique is very versatile and allows for the detection of different diseases just by changing the surface modifications on MNPs.

The past decade has seen the continuous advancing of disease diagnostic platforms in a wide variety of research areas such as magnetic, optical, mechanical, and electrochemical sensing systems. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] However, the processes of developing these platforms towards point-of-care (POC) devices for field testing are largely delayed despite their promising high sensitivity. [14] [15] [16] [17] Most of the diagnostic platforms are complicated to use on site since they rely on expensive and/or bulky laboratory equipment as well as trained technicians to operate. Furthermore, biological samples often need to be pre-processed to remove substances such as blood cells from whole blood samples that may interfere with the fluorescence signal. These factors lead to relatively expensive diagnostics and long turnaround time. Although there are strip tests available in the market for at-home pregnancy and common diseases testing that are easy-to-use and inexpensive, 18, 19 these strip tests are only limited to certain diseases and there is a big concern raised by researchers on the accuracy such as high false-positive rates. 20, 21 Furthermore, the strip test results are often qualitative (or binary) which limits their capability for daily monitoring of chronic disease and in-depth disease analysis.

In recent years, the demand for high accuracy, inexpensive, and easy-to-use POC devices for routine daily diagnostics that are more accessible to patients is tremendously increasing. During the COVID-19 pandemic, the inaccessibility to portable diagnostic devices has put great pressure on the local healthcare systems especially in developing countries and rural areas. [22] [23] [24] [25] Diagnostic platforms that combine the accessibility of strip tests and the high accuracy and quantitative nature of laboratory-based tests will greatly change current situation.

Herein, we introduce a portable, quantitative diagnostic platform based on a magnetic particle spectrometer (MPS) called MagiCoil, that can be operated by layperson in non-clinical settings such as schools, homes, and offices, etc., without much training requirements. This technique relies on detecting dynamic magnetic responses of magnetic nanoparticles (MNPs) from biological samples. 10, [26] [27] [28] [29] [30] [31] [32] [33] [34] Since MNPs are the sole sources of magnetic signal and most biological samples are non-magnetic or paramagnetic, this MPS platform is naturally immune to the background noise from biological samples and thus, it does not require sample pre-processing and allows onestep and wash-free bioassays. Furthermore, by surface functionalizing MNPs with different ligands (e.g., carboxylic acid, amine), nucleic acids (i.e., DNA, RNA), and proteins (e.g., antibodies, streptavidin, protein A, etc.), the MNPs can be specifically modified for detecting different target analytes as well as diseases. 10 harmonic) between 5 kHz and 7 kHz. More details on the 3D models and user interfaces are given in Supporting Information S1. Figure 2 shows the block level breakdown of the developed MagiCoil device. One of the key requirements for MagiCoil modality for bioassay applications is the generation of phase stable magnetic fields. DDS IC from Analog Devices AD9833 is used to generate stable low frequency (fL) and high frequency (fH) sinusoid fields for this application. Frequencies fL and fH are kept at 50 Hz and 5 kHz, respectively. DC-shift and gain stages are implemented to obtain suitable signal amplitudes using ultra-high precision operational amplifiers OPA189 before feeding the signal to voltage source implementation using highvoltage, high-current operational amplifier from Texas Instruments (TI) OPA548. For the application presented in this work, the magnitude of low frequency field is kept at 250 Oe and that of high frequency field is kept at 25

Oe.

Differential voltage signal generated form balanced pick-up coils (Figure 3 along the external magnetic field direction, this process generate dynamic magnetic responses that can be detected by the pick-up coils. [38] [39] [40] [41] As a result, MNPs generate higher harmonics that are observed from the MPS spectra.

In the results reported in this work, we only analyze the higher harmonics at fH+2fL (the 3 rd harmonic), fH+4fL (the 5 th harmonic), fH+6fL (the 7 th harmonic), fH+8fL (the 9 th harmonic), fH+10fL (the 11 th harmonic), fH+12fL (the 13 th harmonic), and fH+14fL (the 15 th harmonic) as highlighted in grey region from Figure 3 (b). It is worth mentioning that most of the previous research work rely on the 3 rd and the 5 th harmonics as metrics for quantitative bioassays. Herein, we used higher order harmonics (from the 3 rd up to the 15 th harmonics) as reliable metrics to achieve highly sensitive and quantitative bioassay purposes. Compared to most bioassay techniques, this MPS-based bioassay does not require to remove unbound target analytes. Making it wash-free, one-step testing that is accessible by layperson in non-clinical settings.

In addition, this kind of MPS platform can be customized to detect a wide range of biomarkers as well as diseases. A more generalized detection scheme for detecting antigens using antibody-antigen interactions is given 7 in Figure 3 (d): xii). MNPs can be surface functionalized with polyclonal antibodies (pAb). In the presence of target antigens, these pAb will specifically bind to different epitopes from the antigens. 10 Table 1 ) are measured at 300 K using a physical properties measurement system (PPMS) integrated with a vibrating sample magnetometer (Quantum Design). As plotted in Figure S2 from Supporting Information. The magnetic field is swept from -2000 Oe to +2000 Oe with a step of 2 Oe (or -300 Oe to +300 Oe with a step of 1 Oe), and the averaging time for each step is 100 ms. The dc magnetic properties of MNPs such as coercivities and saturation magnetizations are listed in Table 1 .

The hydrodynamic size distribution of MNP sample is characterized using dynamic light scattering (DLS) particle tracking analyzer (Model: Microtac Nanoflex). 150 µL of samples I, III, V, VII, and X (listed in Table 2 ) is diluted in 1.35 mL of PBS, reaching a total sample volume of 1.5 mL mixture. This is followed by ultra-sonication for 30 minutes before the DLS characterization. Table 1 . Sample C with highest MNP concentration yields highest magnetic moment per microliter volume (unit: µemu/µL). The magnetic moment per volume of MNPs from highest to lowest are ranked as: C > A > B ~ D > E. All the MNP samples show negligible coercivities. Nine independent MPS measurements are carried on each sample and the averaged harmonic amplitudes (3 rd , 5 th , 7 th , 9 th , 11 th , 13 th , 15 th ) are summarized in Figure 4 Table 1 for comparison. The 3 rd harmonic amplitude shows similar trend with respect to the magnetic moment per volume. 

To demonstrate the sensitivity of our MagiCoil portable device in detecting the lowest amount of iron oxide MNPs. 80 µL of SHB30 iron oxide MNP samples are prepared by two-fold dilutions, as listed in Table 2 . From samples 1 to 5, the MNP weight per vial drops from 64 µg to 4 µg. Sample index Blank is a glass vial containing 80 µL of PBS. As shown in Figure 4 (b), the higher harmonics from samples 1 -5 are summarized and compared with the blank sample.

It's clearly seen that sample 1 shows highest MPS signals, followed by samples 2 and 3. Although samples 4 and 5 show similar harmonic amplitudes compared to blank sample as shown in Figure 4(c) . The two-sample t-test results show that the 9 th and the 11 th harmonics from sample 4 are significantly different from the blank sample, with p-values of 0.034 and 0.01, respectively. In addition, the 11 th harmonic from sample 5 is significantly MNPs with 80 µL of PBS. The MNP to streptavidin ratios are also listed in Table 3 . All the samples are incubated at room temperature for 30 min to allow the binding of streptavidin molecules to biotins from MNP surface. We carried out six independent MPS measurements on each sample, as shown in the scatter plots in Figure   5 (a). Two-sample t-test is carried out on each sample to compare with the control group (sample index X, 0 nM).

As shown in Figure 5 As we increase the amount of streptavidin, the distribution of particle sizes becomes wider and particles with several hundreds and thousands of nanometers' sizes are observed. The two-sample t-test on samples V and X shows a p-value of 0.58 and this small difference can be explained by the peak tail in Figure 6 (c) within a size range of 100 nm -300 nm. From sample III in Figure 6 (d), we observed a second particle size peak at ~175 nm.

On the other hand, a second particle size peak is also observed at ~300 nm from sample I in Figure 6 (e). The insets in Figure 6 As seen from the p-value heatmap in Figure 7 (b), all the higher harmonics from samples I and II are significantly different from the control sample X, with p-values smaller than 0.001. For samples III -V, the 3 rd harmonics are significantly different from control sample X. It's worth to mention that, the 7 th , the 11 th , and the 15 th harmonics of sample VI are significantly different from control sample X with p-values smaller than 0.05, demonstrating that by using multiple higher harmonics as metrics, our MagiCoil portable device is able to detect as low as 64 nM of streptavidin (equal to 5.12 pmole). The streptavidin concentration response curves are plotted in Supporting Information S5 based on the 3 rd , the 5 th , and the 7 th harmonic amplitudes from samples I to X. All the harmonic metrics show a linear dynamic range from 500 nM to 2000 nM. We also demonstrated the feasibility of this platform for bioassay application by using the streptavidin-biotin

binding system as a model. The streptavidin caused cross-linking of MNPs results in weaker dynamic magnetic responses and lower harmonic amplitudes. By analyzing the reduction of harmonic amplitudes, we can quantitatively detect the concentration/amount of target biomarkers. The streptavidin concentration response curves show a linear detection range from 500 nM to 2000 nM. Based on the 3 rd harmonic as the sole metric, we obtained a detection limit of 128 nM (equal to 10.24 pmole). By analyzing multiple higher harmonics as metrics and using the two-sample t-test, we observed a detection limit of 64 nM for streptavidin (equal to 5.12 pmole).

To sum up, the higher harmonics from MPS spectra such as the 3 rd to the 15 th harmonics can be used as metrics to quantitatively characterize target biomarkers. By applying two-sample t-test on samples' higher harmonics, we can achieve better sensitivity from the MagiCoil device. In addition to the sample incubation time, the data collection step is fully automatic and raw data is transferred to laptop in 0.54 s. At current stage, the time domain discrete signal requires further processing such as discrete Fourier transform (DFT) to get frequency domain MPS spectra. In the future, this part of data processing can be combined in smartphone user applications.

Furthermore, we will extend the application of detecting different types of protein biomarkers by conjugating corresponding pAb onto MNPs. Two of the major issues leading to a sensitivity hit for current implementation of S2 S1. 3D model of MagiCoil portable device and smartphone application user interface. Table 1 .

The dc hysteresis loops of samples A -E (listed in Table 1 ) are measured at 300 K using a physical properties measurement system (PPMS) integrated with a vibrating sample magnetometer (Quantum Design). The magnetic field is swept from -2000 Oe to +2000 Oe with a step of 2 Oe (or -300 Oe to +300 Oe with a step of 1 Oe), and the averaging time for each step is 100 ms. Oe. In (f) -(j), the magnetic field is swept from -300 Oe to +300 Oe.

S3: Two-sample t-test for samples 4 and 5 from Table 2 and Figure 3 .

Two-sample t-test is carried out to analyze the differences in harmonic amplitudes between sample 4 (sample 5) and blank sample. The p-values are listed in Table S1 . Two-sample t-test is carried out on each sample compared with the control sample X. *** p < 0.001; ** p < 0.01; * p <0.05. Error bars represent standard deviations.

The streptavidin concentration response curves are plotted based on the 3 rd , the 5 th , and the 7 th harmonic amplitudes from samples I to X. Detection limit is calculated by harmonic amplitudes from sample X subtracting two times of standard deviation. As shown in Figure S4 , the blue dotted lines represent detection limits. Overall, all the harmonic metrics show a linear dynamic range from 500 nM to 2000 nM. The 3 rd harmonic metric shows a detection limit of 128 nM. Figure S4 . Streptavidin concentration response curves based on (a) the 3 rd harmonic, (b) the 5 th harmonic, and (c) the 7 th harmonic. Error bars represent standard deviations.

A Multichannel Smartphone Optical Biosensor for High-Throughput Point-of-Care Diagnostics

Smartphone Based Optical Biosensor for the Detection of Urea in Saliva

Wearable-Band Type Visible-near Infrared Optical Biosensor for Non-Invasive Blood Glucose Monitoring

Nucleic Acid-Functionalized Metal-Organic Framework-Based Homogeneous Electrochemical Biosensor for Simultaneous Detection of Multiple Tumor Biomarkers

Electrical Pulse-Induced Electrochemical Biosensor for Hepatitis E Virus Detection

Gold Nanoparticles Superlattices Assembly for Electrochemical Biosensor Detection of MicroRNA-21

Magnetic Impedance Biosensor: A Review

One-Step, and Rapid GMR Biosensor Platform with Smartphone Interface

Portable GMR Handheld Platform for the Detection of Influenza A Virus

Magnetic Particle Spectroscopy for Detection of Influenza A Virus Subtype H1N1

H7 Bacteria Sensing Using Microfluidic MEMS Biosensor

MEMS Based Impedance Biosensor for Rapid Detection of Low Concentrations of Foodborne Pathogens

Ultrahigh-Frequency, Wireless MEMS QCM Biosensor for Direct, Label-Free Detection of Biomarkers in a Large Amount of Contaminants

Point of Care-a Novel Approach to Periodontal Diagnosis-a Review

Detection Platforms for Point-of-Care Testing Based on Colorimetric, Luminescent and Magnetic Assays: A Review

A Critical Insight into the Development Pipeline of Microfluidic Immunoassay Devices for the Sensitive Quantitation of Protein Biomarkers at the Point of Care

Readiness of Magnetic Nanobiosensors for Point-of-Care Commercialization

Blood Glucose Meters and Test Strips: Global Market and Challenges to Access in Low-Resource Settings

A New Point-of-Care Test for the Diagnosis of Infectious Diseases Based on Multiplex Lateral Flow Immunoassays

False-Positive Results of a Rapid K39-Based Strip Test and Chagas Disease

Accuracy of Rapid Tests Used for Analysis of Advanced Onsite Wastewater Treatment System Effluent

Point-of-Care RNA-Based Diagnostic Device for COVID-19

Simple, Inexpensive, and Mobile Colorimetric Assay COVID-19-LAMP for Mass On-Site Screening of COVID-19

The Vision of Point-of-Care PCR Tests for the COVID-19 Pandemic and Beyond

Diagnosing COVID-19: The Disease and Tools for Detection

Rapid Lateral Flow Assays Based on the Quantification of Magnetic Nanoparticle Labels for Multiplexed Immunodetection of Small Molecules: Application to the Determination of Drugs of Abuse

Ultrasensitive Quantitative Detection of Small Molecules with Rapid Lateral-Flow Assay Based on High-Affinity Bifunctional Ligand and Magnetic Nanolabels

Multiplex Biosensing with Highly Sensitive Magnetic Nanoparticle Quantification Method

Molecular Sensing with Magnetic Nanoparticles Using Magnetic Spectroscopy of Nanoparticle Brownian Motion

Magnetic Nanoparticle Relaxation Dynamics-Based Magnetic Particle Spectroscopy for Rapid and Wash-Free Molecular Sensing

Magnetic Particle Spectroscopy-Based Bioassays: Methods, Applications, Advances, and Future Opportunities

Multiplex Biosensing Based on Highly Sensitive Magnetic Nanolabel Quantification: Rapid Detection of Botulinum Neurotoxins A, B, and E in Liquids

Nanomagnetic Lateral Flow Assay for High-Precision Quantification of Diagnostically Relevant Concentrations of Serum TSH

Analytical Platform with Selectable Assay Parameters Based on Three Functions of Magnetic Nanoparticles: Demonstration of Highly Sensitive Rapid Quantitation of Staphylococcal Enterotoxin B in Food

Brief Communication: Magnetic Immuno-Detection of SARS-CoV-2 Specific Antibodies

Wash-Free Detection of Biological Target Using Cluster Formation of Magnetic Markers

Magnetic Particle Spectroscopy-Based Handheld Device for Wash-Free, Easy-to-Use, and Solution-Phase Immunoassay Applications

Magnetic Particle Detection by Frequency Mixing for Immunoassay Applications

New Type of Biosensor Based on Magnetic Nanoparticle Detection

Harmonic Phase Angle as a Concentration-Independent Measure of Nanoparticle Dynamics

Biological Sensing with Magnetic Nanoparticles Using Brownian Relaxation