Magnetic Nanoparticles: A Review on Synthesis, Characterization, Functionalization, and Biomedical Applications.

Nowadays, magnetic nanoparticles (MNPs) are applied in numerous fields, especially in biomedical applications. Since biofluidic samples and biological tissues are nonmagnetic, negligible background signals can interfere with the magnetic signals from MNPs in magnetic biosensing and imaging applications. In addition, the MNPs can be remotely controlled by magnetic fields, which make it possible for magnetic separation and targeted drug delivery. Furthermore, due to the unique dynamic magnetizations of MNPs when subjected to alternating magnetic fields, MNPs are also proposed as a key tool in cancer treatment, an example is magnetic hyperthermia therapy. Due to their distinct surface chemistry, good biocompatibility, and inducible magnetic moments, the material and morphological structure design of MNPs has attracted enormous interest from a variety of scientific domains. Herein, a thorough review of the chemical synthesis strategies of MNPs, the methodologies to modify the MNPs surface for better biocompatibility, the physicochemical characterization techniques for MNPs, as well as some representative applications of MNPs in disease diagnosis and treatment are provided. Further portions of the review go into the diagnostic and therapeutic uses of composite MNPs with core/shell structures as well as a deeper analysis of MNP properties to learn about potential biomedical applications.

Giant Magnetoresistance Based Biosensors for Cancer Screening and Detection.

Early-stage screening of cancer is critical in preventing its development and therefore can improve the prognosis of the disease. One accurate and effective method of cancer screening is using high sensitivity biosensors to detect optically, chemically, or magnetically labeled cancer biomarkers. Among a wide range of biosensors, giant magnetoresistance (GMR) based devices offer high sensitivity, low background noise, robustness, and low cost. With state-of-the-art micro- and nanofabrication techniques, tens to hundreds of independently working GMR biosensors can be integrated into fingernail-sized chips for the simultaneous detection of multiple cancer biomarkers (i.e., multiplexed assay). Meanwhile, the miniaturization of GMR chips makes them able to be integrated into point-of-care (POC) devices. In this review, we first introduce three types of GMR biosensors in terms of their structures and physics, followed by a discussion on fabrication techniques for those sensors. In order to achieve target cancer biomarker detection, the GMR biosensor surface needs to be subjected to biological decoration. Thus, commonly used methods for surface functionalization are also reviewed. The robustness of GMR-based biosensors in cancer detection has been demonstrated by multiple research groups worldwide and we review some representative examples. At the end of this review, the challenges and future development prospects of GMR biosensor platforms are commented on. With all their benefits and opportunities, it can be foreseen that GMR biosensor platforms will transition from a promising candidate to a robust product for cancer screening in the near future.

A performance comparison of heterostructure surface plasmon resonance biosensor for the diagnosis of novel coronavirus SARS-CoV-2.

This paper presents a performance comparison of heterostructure surface plasmon resonance (SPR) biosensors for the application of Novel Coronavirus SARS-CoV-2 diagnosis. The comparison is performed and compared with the existing literature based on the performance parameters in terms of several prisms such as BaF2, BK7, CaF2, CsF, SF6, and SiO2, several adhesion layers such as TiO2, Chromium, plasmonic metals such as Ag, Au, and two-dimensional (2D) transition metal dichalcogenides materials such as BP, Graphene, PtSe2 MoS2, MoSe2, WS2, WSe2. To study the performance of the heterostructure SPR sensor, the transfer matrix method is applied, and to analyses, the electric field intensity near the graphene-sensing layer contact, the finite-difference time-domain approach is utilized. Numerical results show that the heterostructure comprised of CaF2/TiO2/Ag/BP/Graphene/Sensing-layer has the best sensitivity and detection accuracy. The proposed sensor has an angle shift sensitivity of 390°/refractive index unit (RIU). Furthermore, the sensor achieved a detection accuracy of 0.464, a quality factor of 92.86/RIU, a figure of merit of 87.95, and a combined sensitive factor of 85.28. Furthermore, varied concentrations (0-1000 nM) of biomolecule binding interactions between ligands and analytes have been observed for the prospects of diagnosis of the SARS-CoV-2 virus. Results demonstrate that the proposed sensor is well suited for real-time and label-free detection particularly SARS-CoV-2 virus detection.

Highly Sensitive TiO2/Au/Graphene Layer-Based Surface Plasmon Resonance Biosensor for Cancer Detection.

In this article, a hybrid TiO2/Au/graphene layer-based surface plasmon resonance (SPR) sensor with improved sensitivity and capability for cancer detection is presented. The finite element method (FEM) was used for numerical analysis. The proposed SPR biosensor was structured based on the angular analysis of the attenuated total reflection (ATR) method for the detection of various types of cancer using the refractive index component. The resonance angle shifted owing to the increment of normal and cancerous cells' refractive index, which varied between 1.36 and 1.401 for six different types of normal and cancerous cells. According to numerical results, the obtained sensitivities for skin (basal), cervical (HeLa), adrenal gland (PC12), blood (Jurkat), and breast (MCF-7 and MDA-MB-231) cancer cells were 210 deg/RIU, 245.83 deg/RIU, 264.285 deg/RIU, 285.71 deg/RIU, 292.86 deg/RIU, and 278.57 deg/RIU, respectively. Furthermore, the detection accuracy (DA), figure of merits (FOM), and signal-to-noise ratio (SNR) were also obtained, with values of 0.263 deg-1, 48.02 RIU-1, and 3.84, respectively. Additionally, the distribution of the electric field and the propagation of the magnetic field for resonant and non-resonant conditions of the proposed structure were illustrated. It was found that an enhanced field was exhibited on the surface of the plasmonic material for resonant conditions. We also measured the penetration depth of 180 nm using decayed electric field intensity. Furthermore, the impact of using a TiO2/Au/graphene layer was demonstrated. We further conducted analyses of the effects of the thickness of the gold layer and the effects of additional graphene layers on overall sensitivities for six different types of cancer. The proposed TiO2/Au/graphene layered structure exhibited the highest overall sensitivity in terms of detecting cancerous cells from healthy cells. Moreover, the proposed sensor was numerically analyzed for a wide range of biological solutions (refractive index 1.33-1.41), and the sensor linearity was calculated with a linear regression coefficient (R2) of 0.9858. Finally, numerical results obtained in this manuscript exhibited high sensitivity in comparison with previously reported studies.