Smartphone Biosensor System with Multi-Testing Unit Based on Localized Surface Plasmon Resonance Integrated with Microfluidics Chip

Recent advancements of smartphone-based sensing technology for diagnosis, food safety analysis, and environmental monitoring

The emergence of computationally powerful smartphones, relatively affordable high-resolution camera, drones, and robotic sensors have ushered in a new age of advanced sensible monitoring tools. The present review article investigates the burgeoning smartphone-based sensing paradigms, including surface plasmon resonance (SPR) biosensors, electrochemical biosensors, colorimetric biosensors, and other innovations for modern healthcare. Despite the significant advancements, there are still scarcity of commercially available smart biosensors and hence need to accelerate the rates of technology transfer, application, and user acceptability. The application/necessity of smartphone-based biosensors for Point of Care (POC) testing, such as prognosis, self-diagnosis, monitoring, and treatment selection, have brought remarkable innovations which eventually eliminate sample transportation, sample processing time, and result in rapid findings. Additionally, it articulates recent advances in various smartphone-based multiplexed bio sensors as affordable and portable sensing platforms for point-of-care devices, together with statistics for point-of-care health monitoring and their prospective commercial viability.

Gradient Guided-Mode Resonance Biosensor with Smartphone Readout

Integrating biosensors with smartphones is becoming an increasingly popular method for detecting various biomolecules and could replace expensive laboratory-based instruments. In this work, we demonstrate a novel smartphone-based biosensor system with a gradient grating period guided-mode resonance (GGP-GMR) sensor. The sensor comprises numerous gratings which each correspond to and block the light of a specific resonant wavelength. This results in a dark band, which is observed using a CCD underneath the GGP-GMR sensor. By monitoring the shift in the dark band, the concentration of a molecule in a sample can be determined. The sensor is illuminated by a light-emitting diode, and the light transmitted through the GGP-GMR sensor is directly captured by a smartphone, which then displays the results. Experiments were performed to validate the proposed smartphone biosensor and a limit of detection (LOD) of 1.50 × 10-3 RIU was achieved for sucrose solutions. Additionally, multiplexed detection was demonstrated for albumin and creatinine solutions at concentrations of 0-500 and 0-1 mg/mL, respectively; the corresponding LODs were 1.18 and 20.56 μg/mL.

Plasmonic Nanoparticle-Enhanced Optical Techniques for Cancer Biomarker Sensing

This review summarizes recent advances in leveraging localized surface plasmon resonance (LSPR) nanotechnology for sensitive cancer biomarker detection. LSPR arising from noble metal nanoparticles under light excitation enables the enhancement of various optical techniques, including surface-enhanced Raman spectroscopy (SERS), dark-field microscopy (DFM), photothermal imaging, and photoacoustic imaging. Nanoparticle engineering strategies are discussed to optimize LSPR for maximum signal amplification. SERS utilizes electromagnetic enhancement from plasmonic nanostructures to boost inherently weak Raman signals, enabling single-molecule sensitivity for detecting proteins, nucleic acids, and exosomes. DFM visualizes LSPR nanoparticles based on scattered light color, allowing for the ultrasensitive detection of cancer cells, microRNAs, and proteins. Photothermal imaging employs LSPR nanoparticles as contrast agents that convert light to heat, producing thermal images that highlight cancerous tissues. Photoacoustic imaging detects ultrasonic waves generated by LSPR nanoparticle photothermal expansion for deep-tissue imaging. The multiplexing capabilities of LSPR techniques and integration with microfluidics and point-of-care devices are reviewed. Remaining challenges, such as toxicity, standardization, and clinical sample analysis, are examined. Overall, LSPR nanotechnology shows tremendous potential for advancing cancer screening, diagnosis, and treatment monitoring through the integration of nanoparticle engineering, optical techniques, and microscale device platforms.

The Application of Graphene Field-Effect Transistor Biosensors in COVID-19 Detection Technology: A Review

Coronavirus disease 2019 (COVID-19) is a disease caused by the infectious agent of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). The primary method of diagnosing SARS-CoV-2 is nucleic acid detection, but this method requires specialized equipment and is time consuming. Therefore, a sensitive, simple, rapid, and low-cost diagnostic test is needed. Graphene field-effect transistor (GFET) biosensors have become the most promising diagnostic technology for detecting SARS-CoV-2 due to their advantages of high sensitivity, fast-detection speed, label-free operation, and low detection limit. This review mainly focus on three types of GFET biosensors to detect SARS-CoV-2. GFET biosensors can quickly identify SARS-CoV-2 within ultra-low detection limits. Finally, we will outline the pros and cons of the diagnostic approaches as well as future directions.

Synergetic-effect-enhanced electrochemiluminescence of zein-protected Au-Ag bimetallic nanoclusters for CA15-3 detection

In this work, a sandwich-type electrochemiluminescence (ECL) system was constructed for the detection of CA15-3. Gold-silver bimetallic nanoclusters (Au-Ag BNCs) with zein as a protective ligand were synthesized, and the excellent ECL performance of this material was demonstrated for the first time. Zein carrying a variety of groups that ligated with Au-Ag BNCs, forming a protective shell of zein, effectively prevented clusters from aggregating or growing into larger nanoparticles. The synergistic effect of the bimetal promotes the ECL emission, making this nanoscale material an ideal ECL probe. GO-PANI, which effectively promoting the production of sulfate radicals of the co-reactant and significantly increasing the ECL strength, was a good sensing platform for antibody immobilization. Consequently, we constructed an ECL sensor with GO-PANI as the sensing platform and Au-Ag BNCs@zein as the ECL probe, with a detection range of 0.001-100 U mL-1 and a detection limit of 0.0003 U mL-1, provided a strong support for the sensor for future CA15-3 detection applications.

Sample-to-answer sensing technologies for nucleic acid preparation and detection in the field

Efficient sample preparation and accurate disease diagnosis under field conditions are of great importance for the early intervention of diseases in humans, animals, and plants. However, in-field preparation of high-quality nucleic acids from various specimens for downstream analyses, such as amplification and sequencing, is challenging. Thus, developing and adapting sample lysis and nucleic acid extraction protocols suitable for portable formats have drawn significant attention. Similarly, various nucleic acid amplification techniques and detection methods have also been explored. Combining these functions in an integrated platform has resulted in emergent sample-to-answer sensing systems that allow effective disease detection and analyses outside a laboratory. Such devices have a vast potential to improve healthcare in resource-limited settings, low-cost and distributed surveillance of diseases in food and agriculture industries, environmental monitoring, and defense against biological warfare and terrorism. This paper reviews recent advances in portable sample preparation technologies and facile detection methods that have been / or could be adopted into novel sample-to-answer devices. In addition, recent developments and challenges of commercial kits and devices targeting on-site diagnosis of various plant diseases are discussed.

Fiber-Optic-Based Biosensor as an Innovative Technology for Point-of-Care Testing Detection of Foodborne Pathogenic Bacteria To Defend Food and Agricultural Product Safety

Food safety is a concerning issue globally. Foodborne-pathogenic-bacteria-derived foodborne disease outbreaks have increased the threat to human health. The accurate and rapid detection of foodborne bacteria is of great significance for food safety. A fiber-optic-based biosensor has emerged as a powerful technique for the point-of-care testing of foodborne bacteria in food and agricultural products. This Perspective discusses the opportunities and challenges of fiber-optic-based biosensors for foodborne bacteria detection. The corresponding solution strategies to promote the application of this innovative technology in food and agricultural product detection for food safety and human health are also discussed and proposed.

Ultrasensitive detection of CA125 based on a triple signal amplification strategy with a huge number of loaded probes via exonuclease cyclic cleavage, rolling cyclic amplification and strand self-growth

A novel electrochemiluminescence (ECL) aptamer biosensor with high sensitivity and selectivity for the detection of tumor biomarker carbohydrate antigen 125 (CA125) was constructed, and a strategy of triple amplification of signals was proposed using an exonuclease cyclic cleavage aptamer, combined with rolling ring amplification technologies, generating multi-branched dendritic double-stranded DNA to load a large number of probes through "strand self-growth". The double-stranded DNA, which is abbreviated as CP/CA dsDNA, formed by hybridizing the single strand of capture DNA (CP DNA) with the single strand DNA of the CA125 aptamer (CA Apt) was modified on Fe₃O₄@Au. When CA125 was added, CP/CA dsDNA was unwound, and CA125 specifically combined with CA Apt to form a protein-aptamer complex, leaving only CP DNA on the surface of Fe₃O₄@Au. RecJ_f exonuclease cleaved the aptamer in the protein-aptamer complex and released CA125, which recombined with other CA125 aptamers, to form a cycle that produces more CP DNA on Fe₃O₄@Au. Three ssDNA (H1, H2, and H3) were introduced and hybridized with CP DNA to form a dsDNA with a "+" configuration structure. Then phi29 DNA polymerase, T4 DNA ligase, deoxy-ribonucleoside triphosphate (dNTP) and padlock probes were added to form a large number of complementary strands of padlock probes (CS padlock probes) by rolling cyclic amplification. CS padlock probes were linked to the "+" type dsDNA; then ssDNA H4 was added and hybridized with the CS padlock probe to form multi-branched dendritic dsDNA. A large number of tris(2,2'-bipyridyl)ruthenium(II) probes were embedded in the double strands, resulting in an extremely strong ECL signal in the presence of the co-reactant tri-n-propylamine (TPA). There is a linear relationship between the ECL signals and CA125 concentrations in the range of 1.0 × 10^-15-1.0 × 10^-8 mg mL^-1, and the detection limit was 2.38 × 10^-16 mg mL^-1. It has been used for the determination of CA125 in serum samples.

A smartphone-based fluorospectrophotometer and ratiometric fluorescence nanoprobe for on-site quantitation of pesticide residue

Cost-effective and user-friendly quantitation at points-of-need plays an important role in food safety inspection, environmental monitoring, and biomedical analysis. This study reports a stand-alone smartphone-based fluorospectrophotometer (the SBS) installed with a custom-designed application (the SBS-App) for on-site quantitation of pesticide using a ratiometric sensing scheme. The SBS can collect fluorescence emission spectra in the wavelength range of 380-760 nm within 5 s. A ratiometric fluorescence probe is facilely prepared by directly mixing the blue-emissive carbon nanodots (the Fe3+-specific fluorometric indicator) and red-emissive quantum dots (the internal standard) at a ratio of 11.6 (w/w). Based on the acetylcholinesterase/choline oxidase dual enzyme-mediated cascade catalytic reactions of Fe2+/Fe3+ transformation, a ratiometric fluorescence sensing scheme is developed. The practicability of the SBS is validated by on-site quantitation of chlorpyrifos in apple and cabbage with a comparable accuracy to the GC-MS method, offering a scalable solution to establish a cost-effective surveillance system for pesticide pollution.

Smartphone-based platforms implementing microfluidic detection with image-based artificial intelligence

The frequent outbreak of global infectious diseases has prompted the development of rapid and effective diagnostic tools for the early screening of potential patients in point-of-care testing scenarios. With advances in mobile computing power and microfluidic technology, the smartphone-based mobile health platform has drawn significant attention from researchers developing point-of-care testing devices that integrate microfluidic optical detection with artificial intelligence analysis. In this article, we summarize recent progress in these mobile health platforms, including the aspects of microfluidic chips, imaging modalities, supporting components, and the development of software algorithms. We document the application of mobile health platforms in terms of the detection objects, including molecules, viruses, cells, and parasites. Finally, we discuss the prospects for future development of mobile health platforms.

Smartphone surface plasmon resonance imaging for the simultaneous and sensitive detection of acute kidney injury biomarkers with noninvasive urinalysis

A surface plasmon resonance imaging (SPRi) platform integrated with a smartphone was constructed for the simultaneous and sensitive detection of acute kidney injury (AKI) biomarkers. The smartphone SPRi platform was developed without the requirement of additional light and power sources. The LED flash of the smartphone was used as the light source for the excitation of surface plasmon resonance of a gold sensor chip based on the Kretschmann configuration, while the reflected light was collected by the camera of the smartphone. This smartphone SPRi system was conveniently fabricated by 3D printing and showed a sensitivity of 1.78 × 10^-5 refractive index unit (RIU). In addition, based on a magnetic nanoparticle-enhanced sandwich immunoassay, the smartphone SPRi system with a gold array chip was employed for the detection of multiple AKI biomarkers, with a low limit of detection (LOD) of 0.19 ng ml^-1, 0.51 ng ml^-1 and 0.7 ng ml^-1 for the simultaneous detection of neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18) and retinol-binding protein (RBP) in urine, respectively. The biosensors demonstrated high specificity and sensitivity for the simultaneous detection of multiple AKI biomarkers in PBST and urine. The smartphone SPRi system provided a portable and cost-effective platform for point-of-care diagnosis, in-field healthcare and environmental monitoring.

Photonic Sensors in Chemical and Biological Applications

Biosensors are described as analytical devices in which biological substances are detected by using various physicochemical detection systems [...].

An LSPR Sensor Integrated with VCSEL and Microfluidic Chip

The work introduces a localized surface plasmon resonance (LSPR) sensor chip integrated with vertical-cavity surface-emitting lasers (VCSELs). Using VCSEL as the light source, the hexagonal gold nanoparticle array was integrated with anodic aluminum oxide (AAO) as the mask on the light-emitting end face. The sensitivity sensing test of the refractive index solution was realized, combined with microfluidic technology. At the same time, the finite-difference time- domain (FDTD) algorithm was applied to model and simulate the gold nanostructures. The experimental results showed that the output power of the sensor was related to the refractive index of the sucrose solution. The maximum sensitivity of the sensor was 1.65 × 106 nW/RIU, which gives it great application potential in the field of biomolecular detection.

Smartphone-based Surface Plasmon Resonance Sensors: a Review

The surface plasmon resonance (SPR) is a phenomenon based on the combination of quantum mechanics and electromagnetism, which leads to the creation of charge oscillations on a metal-dielectric interface. The SPR phenomenon creates a signal which measures refractive index change at the metal-dielectric interface. SPR-based sensors are being developed for real-time and label-free detection of water pollutants, toxins, disease biomarkers, etc., which are highly sensitive and selective. Smartphones provide hardware and software capability which can be incorporated into SPR sensors, enabling the possibility of economical and accurate on-site portable sensing. The camera, screen, and LED flashlight of the smartphone can be employed as components of the sensor. The current article explores the recent advances in smartphone-based SPR sensors by studying their principle, components, application, and signal processing. Furthermore, the general theoretical and practical aspects of SPR sensors are discussed.

Microfluidic Biosensor-Based Devices for Rapid Diagnosis and Effective Anti-cancer Therapeutic Monitoring for Breast Cancer Metastasis

Breast cancer with unpredictable metastatic recurrence is the leading cause of cancer-related mortality. Early cancer detection and optimized therapy are the principal determining factors for increased survival rate. Worldwide, researchers and clinicians are in search of efficient strategies for the timely management of cancer progression. Efficient preclinical models provide information on cancer initiation, malignancy progression, relapse, and drug efficacy. The distinct histopathological features and clinical heterogeneity allows no single model to mimic breast tumor. However, engineering three-dimensional (3D) in vitro models incorporating cells and biophysical cues using a combination of organoid culture, 3D printing, and microfluidic technology could recapitulate the tumor microenvironment. These models serve to be preferable predictive models bridging the translational research gap in drug development. Microfluidic device is a cost-effective advanced in vitro model for cancer research, diagnosis, and drug assay under physiologically relevant conditions. Integrating a biosensor with microfluidics allows rapid real-time analytical validation to provide highly sensitive, specific, reproducible, and reliable outcomes. In this manner, the multi-system approach in identifying biomarkers associated with cancer facilitates early detection, therapeutic window optimization, and post-treatment evaluation.This chapter showcases the advancements related to in vitro breast cancer metastasis models focusing on microfluidic devices. The chapter aims to provide an overview of microfluidic biosensor-based devices for cancer detection and high-throughput chemotherapeutic drug screening.

Integrated plasmonic biosensor on a vertical cavity surface emitting laser platform

Plasmonic devices can modulate light beyond the diffraction limit and thus have unique advantages in realizing an ultracompact feature size. However, in most cases, external light coupling systems are needed, resulting in a prohibitively bulky footprint. In this paper, we propose an integrated plasmonic biosensor on a vertical cavity surface emitting laser (VCSEL) platform. The plasmonic resonant wavelength of the nanohole array was designed to match (detune) with the emission peak wavelength of the VCSEL before (after) binding the molecules, thus the refractive index that represents the concentration of the molecule could be measured by monitoring the light output intensity. It shows that high contrast with relative intensity difference of 98.8% can be achieved for molecular detection at conventional concentrations. The size of the device chip could be the same as a VCSEL chip with regular specification of hundreds of micrometers in length and width. These results suggest that the proposed integrated sensor device offers great potential in realistic applications.

COVID-19 Biomarkers and Advanced Sensing Technologies for Point-of-Care (POC) Diagnosis

COVID-19, also known as SARS-CoV-2 is a novel, respiratory virus currently plaguing humanity. Genetically, at its core, it is a single-strand positive-sense RNA virus. It is a beta-type Coronavirus and is distinct in its structure and binding mechanism compared to other types of coronaviruses. Testing for the virus remains a challenge due to the small market available for at-home detection. Currently, there are three main types of tests for biomarker detection: viral, antigen and antibody. Reverse Transcription-Polymerase Chain Reaction (RT-PCR) remains the gold standard for viral testing. However, the lack of quantitative detection and turnaround time for results are drawbacks. This manuscript focuses on recent advances in COVID-19 detection that have lower limits of detection and faster response times than RT-PCR testing. The advancements in sensing platforms have amplified the detection levels and provided real-time results for SARS-CoV-2 spike protein detection with limits as low as 1 fg/mL in the Graphene Field Effect Transistor (FET) sensor. Additionally, using multiple biomarkers, detection levels can achieve a specificity and sensitivity level comparable to that of PCR testing. Proper biomarker selection coupled with nano sensing detection platforms are key in the widespread use of Point of Care (POC) diagnosis in COVID-19 detection.

Smartphone-based optical spectroscopic platforms for biomedical applications: a review [Invited]

Rapid advancements in smartphone technology have enabled the integration of many optical detection techniques that leverage the embedded functional components and software platform of these sophisticated devices. Over the past few years, several research groups have developed high-resolution smartphone-based optical spectroscopic platforms and demonstrated their usability in different biomedical applications. Such platforms provide unprecedented opportunity to develop point-of-care diagnostics systems, especially for resource-constrained environments. In this review, we discuss the development of smartphone systems for optical spectroscopy and highlight current challenges and potential solutions to improve the scope for their future adaptability.

How Nanophotonic Label-Free Biosensors Can Contribute to Rapid and Massive Diagnostics of Respiratory Virus Infections: COVID-19 Case

The global sanitary crisis caused by the emergence of the respiratory virus SARS-CoV-2 and the COVID-19 outbreak has revealed the urgent need for rapid, accurate, and affordable diagnostic tests to broadly and massively monitor the population in order to properly manage and control the spread of the pandemic. Current diagnostic techniques essentially rely on polymerase chain reaction (PCR) tests, which provide the required sensitivity and specificity. However, its relatively long time-to-result, including sample transport to a specialized laboratory, delays massive detection. Rapid lateral flow tests (both antigen and serological tests) are a remarkable alternative for rapid point-of-care diagnostics, but they exhibit critical limitations as they do not always achieve the required sensitivity for reliable diagnostics and surveillance. Next-generation diagnostic tools capable of overcoming all the above limitations are in demand, and optical biosensors are an excellent option to surpass such critical issues. Label-free nanophotonic biosensors offer high sensitivity and operational robustness with an enormous potential for integration in compact autonomous devices to be delivered out-of-the-lab at the point-of-care (POC). Taking the current COVID-19 pandemic as a critical case scenario, we provide an overview of the diagnostic techniques for respiratory viruses and analyze how nanophotonic biosensors can contribute to improving such diagnostics. We review the ongoing published work using this biosensor technology for intact virus detection, nucleic acid detection or serological tests, and the key factors for bringing nanophotonic POC biosensors to accurate and effective COVID-19 diagnosis on the short term.