In-situ monitoring of breast cancer cell (MCF-7) growth and quantification of the cytotoxicity of anticancer drugs fluorouracil and cisplatin

A cost-effective smartphone-based device for rapid C-reaction protein (CRP) detection using magnetoelastic immunosensor

C-Reaction protein (CRP) is a marker of nonspecific immunity for vital signs and wound assessment, and it can be used to diagnose infections in clinical medicine. However, measuring CRP level currently requires hospital-based instruments, high-cost reagents, and a complex process, all of which have limited its full capabilities for self-detection, a growing trend in modern medicine. In this study, we developed a novel smartphone-based device using advanced methods of magnetoelastic immunosensing to mitigate these limitations. We combined a system-on-chip (SoC) hardware architecture with smartphone apps to realize the sampling of resonance frequency shift on magnetoelastic chips, which can determine the ultra-sensitivity to mass change caused by the binding of anti-CRP antibody and CRP. Through detecting a multi-group of samples, we found that the resonance frequency shift was linearly proportional to the CRP concentration in the range from 0.1 to 100 μg mL^-1, with a sensitivity of 12.90 Hz μg^-1 mL^-1 and a detection limit of 2.349 × 10^-4 μg mL^-1. Meanwhile, compared with the large-scale instrument used in clinical settings, the performance of our device was stable and significantly more portable, rapid and cost-effective, offering excellent potential for modern home-based diagnosis.

Magnetoelastic Monitoring System for Tracking Growth of Human Mesenchymal Stromal Cells

Magnetoelastic sensors, which undergo mechanical resonance when interrogated with magnetic fields, can be functionalized to measure various physical quantities and chemical/biological analytes by tracking their resonance behaviors. The unique wireless and functionalizable nature of these sensors makes them good candidates for biological sensing applications, from the detection of specific bacteria to tracking force loading inside the human body. In this study, we evaluate the viability of magnetoelastic sensors based on a commercially available magnetoelastic material (Metglas 2826 MB) for wirelessly monitoring the attachment and growth of human mesenchymal stromal cells (hMSCs) in 2D in vitro cell culture. The results indicate that the changes in sensor resonance are linearly correlated with cell quantity. Experiments using a custom-built monitoring system also demonstrated the ability of this technology to collect temporal profiles of cell growth, which could elucidate key stages of cell proliferation based on acute features in the profile. Additionally, there was no observed change in the morphology of cells after they were subjected to magnetic and mechanical stimuli from the monitoring system, indicating that this method for tracking cell growth may have minimal impact on cell quality and potency.

Magnetoelastic Sensor Optimization for Improving Mass Monitoring

Magnetoelastic sensors, typically made of magnetostrictive and magnetically-soft materials, can be fabricated from commercially available materials into a variety of shapes and sizes for their intended applications. Since these sensors are wirelessly interrogated via magnetic fields, they are good candidates for use in both research and industry, where detection of environmental parameters in closed and controlled systems is necessary. Common applications for these sensors include the investigation of physical, chemical, and biological parameters based on changes in mass loading at the sensor surface which affect the sensor’s behavior at resonance. To improve the performance of these sensors, optimization of sensor geometry, size, and detection conditions are critical to increasing their mass sensitivity and detectible range. This work focuses on investigating how the geometry of the sensor influences its resonance spectrum, including the sensor’s shape, size, and aspect ratio. In addition to these factors, heterogeneity in resonance magnitude was mapped for the sensor surface and the effect of the magnetic bias field strength on the resonance spectrum was investigated. Analysis of the results indicates that the shape of the sensor has a strong influence on the emergent resonant modes. Reducing the size of the sensor decreased the sensor’s magnitude of resonance. The aspect ratio of the sensor, along with the bias field strength, was also observed to affect the magnitude of the signal; over or under biasing and aspect ratio extremes were observed to decrease the magnitude of resonance, indicating that these parameters can be optimized for a given shape and size of magnetoelastic sensor.

Magnetoelastic Immunosensor via Antibody Immobilization for the Specific Detection of Lysozymes

Lysozymes in human urine have crucial clinical significance as an indicator of renal tubular and glomerular diseases. Most lysozyme detection methods rely on the enzyme-linked immunosorbent assay (ELISA), which is usually a tedious procedure. Meanwhile, aptamer sensors and fluorescence-based techniques for lysozyme detection have emerged in recent studies. However, these methods are time-consuming and highly complex in operation, and some even require exorbitant reagents and instruments, which restricts real-time clinical monitoring as diagnostic approaches. Therefore, a rapid and low-cost lysozyme detection method with facile preparation is still in demand for modern precision medicine. Herein, we propose a magnetoelastic (ME) immunosensor for lysozyme detection by detecting changes in resonance frequency under a magnetostrictive effect. The detection system is composed of a magnetoelastic chip with an immobilized lysozyme antibody, a solenoid coil, and a vector network analyzer. Since the ME sensor is ultrasensitive to mass change, the frequency offset caused by mass change can be utilized to detect the content of lysozyme. The immunosensor is evaluated to possess superior sensitivity of 138 Hz/μg mL^-1 in terms of the resonance frequency shift (RFS). In addition, our sensor displays an outstanding performance in specificity experiments and shows a relatively lower detection limit (1.26 ng/mL) than other conventional lysozyme detection methods (such as ELISA, chemiluminescence assay, fluorescence, and aptamer biosensors).

Biocompatibility and degradation of gold-covered magneto-elastic biosensors exposed to cell culture

Magneto-elastic materials (ME) have important advantages when applied as biosensors due to the possibility of wireless monitoring. Commercial Metglas 2826MB3™ (FeNiMoB) is widely used, however sensor stabilization is an important factor for biosensor performance. This study compared the effects of biocompatibility and degradation of the Metglas 2826MB3™ alloy, covered or not with a gold layer, when in contact with cell culture medium. Strips of amorphous Metglas 2826MB3™ were cut and coated with thin layers of Cr and Au, as verified by Rutherford Backscattering Spectroscopy (RBS). Using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), the presence of metals in the culture medium was quantitatively determined for up to seven days after alloy exposure. Biocompatibility of fibroblast Chinese Hamster Ovary (CHO) cultures was tested and cytotoxicity parameters were investigated by indirect means of reduction of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) at 1, 2 and 7 days. Cell death was further evaluated through in situ analysis using Acridine Orange/Ethidium Bromide (AO/EB) staining and images were processed with ImageJ software. Ions from Metglas(®) 2826MB3™ induced a degradation process in living organisms. The cytotoxicity assay showed a decrease in the percentage of live cells compared to control for the ME strip not coated with gold. AO/EB in situ staining revealed that most of the cells grown on top of the gold-covered sensor presented a normal morphology (85.46%). Covering ME sensors with a gold coating improved their effectiveness by generating protection of the transducer by reducing the release of ions and promoting a significant cell survival.

Direct chemosensitivity monitoring ex vivo on undissociated melanoma tumor tissue by impedance spectroscopy

Stage III/IV melanoma remains incurable in most cases due to chemotherapeutic resistance. Thus, predicting and monitoring chemotherapeutic responses in this setting offer great interest. To overcome limitations of existing assays in evaluating the chemosensitivity of dissociated tumor cells, we developed a label-free monitoring system to directly analyze the chemosensitivity of undissociated tumor tissue. Using a preparation of tumor micro-fragments (TMF) established from melanoma biopsies, we characterized the tissue organization and biomarker expression by immunocytochemistry. Robust generation of TMF was established successfully and demonstrated on a broad range of primary melanoma tumors and tumor metastases. Organization and biomarker expression within the TMF were highly comparable with tumor tissue, in contrast to dissociated, cultivated tumor cells. Using isolated TMF, sensitivity to six clinically relevant chemotherapeutic drugs (dacarbazine, doxorubicin, paclitaxel, cisplatin, gemcitabine, and treosulfan) was determined by impedance spectroscopy in combination with a unique microcavity array technology we developed. In parallel, comparative analyses were performed on monolayer tumor cell cultures. Lastly, we determined the efficacy of chemotherapeutic agents on TMF by impedance spectroscopy to obtain individual chemosensitivity patterns. Our results demonstrated nonpredictable differences in the reaction of tumor cells to chemotherapy in TMF by comparison with dissociated, cultivated tumor cells. Our direct impedimetric analysis of melanoma biopsies offers a direct ex vivo system to more reliably predict patient-specific chemosensitivity patterns and to monitor antitumor efficacy.

Application of sub-micrometer vibrations to mitigate bacterial adhesion

As a prominent concern regarding implantable devices, eliminating the threat of opportunistic bacterial infection represents a significant benefit to both patient health and device function. Current treatment options focus on chemical approaches to negate bacterial adhesion, however, these methods are in some ways limited. The scope of this study was to assess the efficacy of a novel means of modulating bacterial adhesion through the application of vibrations using magnetoelastic materials. Magnetoelastic materials possess unique magnetostrictive property that can convert a magnetic field stimulus into a mechanical deformation. In vitro experiments demonstrated that vibrational loads generated by the magnetoelastic materials significantly reduced the number of adherent bacteria on samples exposed to Escherichia coli, Staphylococcus epidermidis and Staphylococcus aureus suspensions. These experiments demonstrate that vibrational loads from magnetoelastic materials can be used as a post-deployment activated means to deter bacterial adhesion and device infection.

Selective identification of macrophages and cancer cells based on thermal transport through surface-imprinted polymer layers

In this article, we describe a novel straightforward method for the specific identification of viable cells (macrophages and cancer cell lines MCF-7 and Jurkat) in a buffer solution. The detection of the various cell types is based on changes of the heat transfer resistance at the solid-liquid interface of a thermal sensor device induced by binding of the cells to a surface-imprinted polymer layer covering an aluminum chip. We observed that the binding of cells to the polymer layer results in a measurable increase of heat transfer resistance, meaning that the cells act as a thermally insulating layer. The detection limit was found to be on the order of 10(4) cells/mL, and mutual cross-selectivity effects between the cells and different types of imprints were carefully characterized. Finally, a rinsing method was applied, allowing for the specific detection of cancer cells with their respective imprints while the cross-selectivity toward peripheral blood mononuclear cells was negligible. The concept of the sensor platform is fast and low-cost while allowing also for repetitive measurements.

Rapid and sensitive detection of Salmonella Typhimurium on eggshells by using wireless biosensors

This article presents rapid, sensitive, direct detection of Salmonella Typhimurium on eggshells by using wireless magnetoelastic (ME) biosensors. The biosensor consists of a freestanding, strip-shaped ME resonator as the signal transducer and the E2 phage as the biomolecular recognition element that selectively binds with Salmonella Typhimurium. This ME biosensor is a type of mass-sensitive biosensor that can be wirelessly actuated into mechanical resonance by an externally applied timevarying magnetic field. When the biosensor binds with Salmonella Typhimurium, the mass of the sensor increases, resulting in a decrease in the sensor's resonant frequency. Multiple E2 phage-coated biosensors (measurement sensors) were placed on eggshells spiked with Salmonella Typhimurium of various concentrations (1.6 to 1.6 × 10(7) CFU/cm(2)). Control sensors without phage were also used to compensate for environmental effects and nonspecific binding. After 20 min in a humidity-controlled chamber (95%) to allow binding of the bacteria to the sensors to occur, the resonant frequency of the sensors was wirelessly measured and compared with their initial resonant frequency. The resonant frequency change of the measurement sensors was found to be statistically different from that of the control sensors down to 1.6 × 10(2) CFU/cm(2), the detection limit for this work. In addition, scanning electron microscopy imaging verified that the measured resonant frequency changes were directly related to the number of bound cells on the sensor surface. The total assay time of the presented methodology was approximately 30 min, facilitating rapid detection of Salmonella Typhimurium without any preceding sampling procedures.