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

pH-responsive membranes: Mechanisms, fabrications, and applications

Understanding the mechanisms of pH-responsiveness allows researchers to design and fabricate membranes with specific functionalities for various applications. The pH-responsive membranes (PRMs) are particular categories of membranes that have an amazing aptitude to change their properties such as permeability, selectivity and surface charge in response to changes in pH levels. This review provides a brief introduction to mechanisms of pH-responsiveness in polymers and categorizes the applied polymers and functional groups. After that, different techniques for fabricating pH-responsive membranes such as grafting, the blending of pH-responsive polymers/microgels/nanomaterials, novel polymers and graphene-layered PRMs are discussed. The application of PRMs in different processes such as filtration membranes, reverse osmosis, drug delivery, gas separation, pervaporation and self-cleaning/antifouling properties with perspective to the challenges and future progress are reviewed. Lastly, the development and limitations of PRM fabrications and applications are compared to provide inclusive information for the advancement of next-generation PRMs with improved separation and filtration performance.

Titania-Graphene Oxide Nanocomposite-Based Philadelphia-Positive Leukemia Therapy

Philadelphia-positive (Ph+) leukemia is a type of blood cancer also known as acute lymphoblastic leukemia (ALL), affecting 20-30% of adults diagnosed worldwide and having an engraved prognosis as compared to other types of leukemia. The current treatment regimens mainly rely on tyrosine kinase inhibitors (TKIs) and bone marrow transplants. To date, several generations of TKIs have been developed due to associated resistance and frequent relapse, with cardiovascular system anomalies being the most devastating complication. Nanotechnology has the potential to address these limitations by the targeted drug delivery and controlled release of TKIs. This study focused on the titanium dioxide (TiO2) and graphene oxide (GO) nanocomposite employment to load nilotinib and ponatinib TKIs for therapy of Ph+ leukemia cell line (K562) and Ba/F3 cells engineered to express BCR-ABL oncogene. Meanwhile, after treatment, the oncogene expressing fibroblast cells (Rat-1 P185) were evaluated for their colony formation ability under 3D conditions. To validate the nanocomposite formation, the TiO2-GO nanocomposites were characterized by scanning electron microscope, DLS, XRD, FTIR, zeta potential, EDX, and element mapping. The TKI-loaded TiO2-GO was not inferior to the free drugs after evaluating their effects by a cell viability assay (XTT), apoptosis induction, and colony formation inhibition. The cell signaling pathways of the mammalian target of rapamycin (mTOR), signal transducers and activators of transcription 5 (STAT5), and extracellular signal-regulated kinase (Erk1/2) were also investigated by Western blot. These signaling pathways were significantly downregulated in the TKI-loaded TiO2-GO-treated groups. Based on the findings above, we can conclude that TiO2-GO exhibited excellent drug delivery potential that can be used for Ph+ leukemia therapy in the future, subject to further investigations.

Advancements and Perspectives in Optical Biosensors

Optical biosensors exhibit immense potential, offering extraordinary possibilities for biosensing due to their high sensitivity, reusability, and ultrafast sensing capabilities. This review provides a concise overview of optical biosensors, encompassing various platforms, operational mechanisms, and underlying physics, and it summarizes recent advancements in the field. Special attention is given to plasmonic biosensors and metasurface-based biosensors, emphasizing their significant performance in bioassays and, thus, their increasing attraction in biosensing research, positioning them as excellent candidates for lab-on-chip and point-of-care devices. For plasmonic biosensors, we emphasize surface plasmon resonance (SPR) and its subcategories, along with localized surface plasmon resonance (LSPR) devices and surface enhance Raman spectroscopy (SERS), highlighting their ability to perform diverse bioassays. Additionally, we discuss recently emerged metasurface-based biosensors. Toward the conclusion of this review, we address current challenges, opportunities, and prospects in optical biosensing. Considering the advancements and advantages presented by optical biosensors, it is foreseeable that they will become a robust and widespread platform for early disease diagnostics.

Advancement in Biosensor Technologies of 2D MaterialIntegrated with Cellulose-Physical Properties

This review paper provides an in-depth analysis of recent advancements in integrating two-dimensional (2D) materials with cellulose to enhance biosensing technology. The incorporation of 2D materials such as graphene and transition metal dichalcogenides, along with nanocellulose, improves the sensitivity, stability, and flexibility of biosensors. Practical applications of these advanced biosensors are explored in fields like medical diagnostics and environmental monitoring. This innovative approach is driving research opportunities and expanding the possibilities for diverse applications in this rapidly evolving field.

A Point-of-Care Testing Device Utilizing Graphene-Enhanced Fiber Optic SPR Sensor for Real-Time Detection of Infectious Pathogens

Timely detection of highly infectious pathogens is essential for preventing and controlling public health risks. However, most traditional testing instruments require multiple tedious steps and ultimately testing in hospitals and third-party laboratories. The sample transfer process significantly prolongs the time to obtain test results. To tackle this aspect, a portable fiber optic surface plasmon resonance (FO-SPR) device was developed for the real-time detection of infectious pathogens. The portable device innovatively integrated a compact FO-SPR sensing component, a signal acquisition and processing system, and an embedded power supply unit. A gold-plated fiber is used as the FO-SPR sensing probe. Compared with traditional SPR sensing systems, the device is smaller size, lighter weight, and higher convenience. To enhance the detection capacity of pathogens, a monolayer graphene was coated on the sensing region of the FO-SPR sensing probe. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was used to evaluate the performance of the portable device. The device can accurately detect the SARS-CoV-2 spike S1 protein in phosphate-buffered saline (PBS) and artificial saliva within just 20 min, and the device successfully detected cultured SARS-CoV-2 virus. Furthermore, the FO-SPR probe has long-term stability, remaining stable for up to 8 days. It could distinguish between the SARS-CoV-2 spike protein and the MERS-CoV spike protein. Hence, this FO-SPR device provides reliable, rapid, and portable access to test results. It provides a promising point-of-care testing (POCT) tool for on-site screening of infectious pathogens.

Visible and angular interrogation of Kretschmann-based SPR using hybrid Au-ZnO optical sensor for hyperuricemia detection

Uric acid is a waste product of the human body where high levels of it or hyperuricemia can lead to gout, kidney disease and other health issues. In this paper, Finite Difference Time Doman (FDTD) simulation method was used to develop a plasmonic optical sensor to detect uric acid with molarity ranging from 0 to 3.0 mM. A hybrid layer of gold-zinc oxide (Au-ZnO) was used in this Kretschmann-based Surface Plasmon Resonance (K-SPR) technique with angular interrogation at 670 nm and 785 nm visible optical wavelengths. The purpose of this study is to observe the ability of the hybrid material as a sensing performance enhancer for differentiating between healthy and unhealthy uric acid levels based on the refractive index values from previous study. Upon exposure to 670 nm wavelength, the average sensitivity of this sensor was found to be 0.028°/mM with a linearity of 98.67 % and Q-factor value of 0.0053 mM - 1 . While at 785 nm, the average sensitivity is equal to 0.0193°/mM with slightly lower linearity at 94.46 % and Q-factor value of 0.0076 mM - 1 . The results have proven the ability of hybrid material Au-ZnO as a sensing performance enhancer for detecting uric acid when compared with bare Au and can be further explored in experimental work.

A review on hybridization of plasmonic and photonic crystal biosensors for effective cancer cell diagnosis

Cancer causes one in six deaths worldwide, and 1.6 million cancer patients face annual out-of-pocket medical expenditures. In response to these, portable, label-free, highly sensitive, specific, and responsive optical biosensors are under development. Therefore, in this review, the recent advances, advantages, performance analysis, and current challenges associated with the fabrication of plasmonic biosensors, photonic crystals, and the hybridization of both for cancer diagnosis are assessed. The primary focus is on the development of biosensors that combine different shapes, sizes, and optical properties of metallic and dielectric nanoparticles with various coupling techniques. The latter part discusses the challenges and prospects of developing effective biosensors for early cancer diagnosis using dielectric and metallic nanoparticles. These data will help the audience advance research and development of next-generation plasmonic biosensors for effective cancer diagnosis.

Highly sensitive label-free biosensor: graphene/CaF2 multilayer for gas, cancer, virus, and diabetes detection with enhanced quality factor and figure of merit

One of the primary goals for the researchers is to create a high-quality sensor with a simple structure because of the urgent requirement to identify biomolecules at low concentrations to diagnose diseases and detect hazardous chemicals for health early on. Recently graphene has attracted much interest in the field of improved biosensors. Meanwhile, graphene with new materials such as CaF2 has been widely used to improve the applications of graphene-based sensors. Using the fantastic features of the graphene/CaF2 multilayer, this article proposes an improvement sensor in the sensitivity (S), the figure of merit (FOM), and the quality factor (Q). The proposed sensor is based on the five-layers graphene/dielectric grating integrated with a Fabry-Perot cavity. By tuning graphene chemical potential (µc), due to the semi-metal features of graphene, the surface plasmon resonance (SPR) waves excited at the graphene/dielectric boundaries. Due to the vertical polarization of the source to the gratings and the symmetry of the electric field, both corners of the grating act as electric dipoles, and this causes the propagation of plasmonic waves on the graphene surface to propagate towards each other. Finally, it causes Fabry-Perot (FP) interference on the surface of graphene in the proposed structure's active medium (the area where the sample is located). In this article, using the inherent nature of FP interference and its S to the environment's refractive index (RI), by changing a minimal amount in the RI of the sample, the resonance wavelength (interferometer order) shifts sharply. The proposed design can detect and sense some cancers, such as Adrenal Gland Cancer, Blood Cancer, Breast Cancer I, Breast Cancer II, Cervical Cancer, and skin cancer precisely. By optimizing the structure, we can achieve an S as high as 9000 nm/RIU and a FOM of about 52.14 for the first resonance order (M1). Likewise, the remarkable S of 38,000 nm/RIU and the FOM of 81 have been obtained for the second mode (M2). In addition, the proposed label-free SPR sensor can detect changes in the concentration of various materials, including gases and biomolecules, hemoglobin, breast cancer, diabetes, leukemia, and most alloys, with an accuracy of 0.001. The proposed sensor can sense urine concentration with a maximum S of 8500 nm/RIU and cancers with high S in the 6000 nm/RIU range to 7000 nm/RIU. Also, four viruses, such as M13 bacteriophage, HIV type one, Herpes simplex type 1, and influenza, have been investigated, showing Maximum S (for second resonance mode of λR(M2) of 8000 nm/RIU (λR(M2) = 11.2 µm), 12,000 nm/RIU (λR(M2) = 10.73 µm), 38,000 nm/RIU (λR(M2) = 11.78 µm), and 12,000 nm/RIU (λR(M2) = 10.6 µm), respectively, and the obtained S for first resonance mode (λR(M1)) for mentioned viruses are 4740 nm/RIU (λR(M1) = 8.7 µm), 8010 nm/RIU (λR(M1) = 8.44 µm), 8100 nm/RIU (λR(M1) = 10.15 µm), and 9000 (λR(M1) = 8.36 µm), respectively.

Numerical Investigation on High-Performance Cu-Based Surface Plasmon Resonance Sensor for Biosensing Application

This numerical research presents a simple hybrid structure comprised of TiO2-Cu-BaTiO3 for a modified Kretschmann configuration that exhibits high sensitivity and high resolution for biosensing applications through an angular interrogation method. Recently, copper (Cu) emerged as an exceptional choice as a plasmonic metal for developing surface plasmon sensors (SPR) with high resolution as it yields finer, thinner SPR curves than Ag and Au. As copper is prone to oxidation, especially in ambient conditions, the proposed structure involves the utilization of barium titanate (BaTiO3) film as a protection layer that not only preserves Cu film from oxidizing but enhances the performance of the sensor to a great extent. Numerical results also show that the utilization of a thin adhesive layer of titanium dioxide (TiO2) between the prism base and Cu film not only induces strong interaction between them but also enhances the performance of the sensor. Such a configuration, upon suitable optimization of the thickness of each layer, is found to enhance sensitivity as high as 552°/RIU with a figure of merit (FOM) of 136.97 RIU-1. This suggested biosensor design with enhanced sensitivity is expected to enable long-term detection with greater accuracy and sensitivity even when using Cu as a plasmonic metal.

A single-mode tunable plasmonic sensor based on an 8-shaped resonator for cancer cell detection

In this paper, a novel 8-shaped resonator coupled to metal-insulator-metal waveguides is used for designing plasmonic filters and sensors. The resonator supports two resonance modes, which result in peaks in the transmission spectrum of the structure. A Q-factor of 247.4 which can reach up to 270 at the wavelength of 1187.5 nm is observed. By placing vertical and horizontal metal blades in the resonator, two tunable single-mode plasmonic filters are obtained at the first and second resonance modes, respectively. The effect of structural parameters on the transmission spectrum is investigated using the finite-difference time-domain (FDTD) method. Based on the obtained results, the proposed plasmonic structure can be used for biosensing applications such as the detection of basal cancer cells with a sensitivity of 1200 nm/RIU. It is of great significance that both the sensitivity and Q-factor values for the proposed structure are higher than most recent sensors reported in the literature. Therefore, the proposed structure is a potentially promising candidate for filtering and sensing applications.

Ultrasensitive Surface Plasmon Resonance Sensor with a Feature of Dynamically Tunable Sensitivity and High Figure of Merit for Cancer Detection

Cancer is one of the leading causes of death worldwide, and it is well known that an early detection of cancer in a human body will provide an opportunity to cure the cancer. Early detection of cancer depends on the sensitivity of the measuring device and method, where the lowest detectable concentration of the cancerous cell in a test sample becomes a matter of high importance. Recently, Surface Plasmon Resonance (SPR) has proven to be a promising method to detect cancerous cells. The SPR method is based on the detection of changes in refractive indices of samples under testing and the sensitivity of such a SPR based sensor is related to the smallest detectable change in the refractive index of the sample. There exist many techniques where different combinations of metals, metal alloys and different configurations have been shown to lead to high sensitivities of the SPR sensors. Based on the difference in the refractive index between a normal healthy cell and a cancerous cell, recently, SPR method has been shown to be applicable to detect different types of cancers. In this work, we propose a new sensor surface configuration that comprises of gold-silver-graphene-black phosphorus to detect different cancerous cells based on the SPR method. Additionally, recently we proposed that the application of electric field across gold-graphene layers that form the SPR sensor surface can provide enhanced sensitivity than that is possible without the application of electrical bias. We utilized the same concept and numerically studied the impact of electrical bias across the gold-graphene layers combined with silver and black Phosphorus layers which forms the SPR sensor surface. Our numerical results have shown that electrical bias across the sensor surface in this new heterostructure can provide enhanced sensitivity compared to the original unbiased sensor surface. Not only that, our results have shown that as the electrical bias increases, the sensitivity increases up to a certain value and stabilizes at a still improved sensitivity value. Such dependence of sensitivity on the applied bias provides a dynamic tunability of the sensitivity and figure-of-merit (FOM) of the sensor to detect different types of cancer. In this work, we used the proposed heterostructure to detect six different types of cancers: Basal, Hela, Jurkat, PC12, MDA-MB-231, and MCF-7. Comparing our results to work published recently, we were able to achieve an enhanced sensitivity ranging from 97.2 to 1851.4 (deg/RIU) and FOM values ranging from 62.13 to 89.81 far above the values presented recently by other researchers.

Numerical Study of Titanium Dioxide and MXene Nanomaterial-Based Surface Plasmon Resonance Biosensor for Virus SARS-CoV-2 Detection

A novel surface plasmon resonance-based biosensor for SARS-CoV-2 virus is proposed in this article. The biosensor is a Kretschmann configuration-based structure that consists of CaF2 prism as base, at which silver (Ag), TiO2, and MXene nanolayers are used to enhance the performance. Theoretically, the performance parameters have been investigated by means of Fresnel equations and transfer matrix method (TMM). The TiO2 nanolayer not only prevents oxidation of Ag layer but also enhances the evanescent field in its vicinity. The sensor provides an ultrahigh angular sensitivity of 346°/RIU for the detection of SARS-CoV-2 virus. Some other performance parameters, including FWHM (full width at half maxima), detection accuracy (DA), limit of detection (LOD), and quality factor (QF) have also been calculated for proposed SPR biosensor with their optimized values 2.907°, 0.3439 deg-1, 1.445 × 10-5, and 118.99 RIU-1, respectively. The obtained results designate that the proposed surface plasmon resonance (SPR) based biosensor has notably enhanced angular sensitivity as compared to previous results reported in the literatures till date. This work may facilitate a significant biological sample sensing device for fast and accurate diagnosis at early stage of SARS-CoV-2 virus.

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.

Nanotechnology-Enabled Biosensors: A Review of Fundamentals, Design Principles, Materials, and Applications

Biosensors are modern engineering tools that can be widely used for various technological applications. In the recent past, biosensors have been widely used in a broad application spectrum including industrial process control, the military, environmental monitoring, health care, microbiology, and food quality control. Biosensors are also used specifically for monitoring environmental pollution, detecting toxic elements' presence, the presence of bio-hazardous viruses or bacteria in organic matter, and biomolecule detection in clinical diagnostics. Moreover, deep medical applications such as well-being monitoring, chronic disease treatment, and in vitro medical examination studies such as the screening of infectious diseases for early detection. The scope for expanding the use of biosensors is very high owing to their inherent advantages such as ease of use, scalability, and simple manufacturing process. Biosensor technology is more prevalent as a large-scale, low cost, and enhanced technology in the modern medical field. Integration of nanotechnology with biosensors has shown the development path for the novel sensing mechanisms and biosensors as they enhance the performance and sensing ability of the currently used biosensors. Nanoscale dimensional integration promotes the formulation of biosensors with simple and rapid detection of molecules along with the detection of single biomolecules where they can also be evaluated and analyzed critically. Nanomaterials are used for the manufacturing of nano-biosensors and the nanomaterials commonly used include nanoparticles, nanowires, carbon nanotubes (CNTs), nanorods, and quantum dots (QDs). Nanomaterials possess various advantages such as color tunability, high detection sensitivity, a large surface area, high carrier capacity, high stability, and high thermal and electrical conductivity. The current review focuses on nanotechnology-enabled biosensors, their fundamentals, and architectural design. The review also expands the view on the materials used for fabricating biosensors and the probable applications of nanotechnology-enabled biosensors.

Plasmonic Refractive Index Sensor Enhanced with Chitosan/Au Bilayer Thin Film for Dopamine Detection

Surface plasmonic sensors have received considerable attention, found extensive applications, and outperformed conventional optical sensors. In this work, biopolymer chitosan (CS) was used to prepare the bilayer structure (CS/Au) of a plasmonic refractive index sensor for dopamine (DA) detection. The sensing characteristics of the developed plasmonic sensor were evaluated. Increasing DA concentrations significantly shifted the SPR dips. The sensor exhibited stability and a refractive index sensitivity of 8.850°/RIU in the linear range 0.1 nM to 1 µM with a detection limit of 0.007 nM and affinity constant of 1.383 × 10⁸ M^-1. The refractive index and thickness of the CS/Au structure were measured simultaneously by fitting the obtained experimental findings to theoretical data based on Fresnel equations. The fitting yielded the refractive index values n (1.5350 ± 0.0001) and k (0.0150 ± 0.0001) for the CS layer contacting 0.1 nM of DA, and the thickness, d was (15.00 ± 0.01) nm. Then, both n and d values increased by increasing DA concentrations. In addition, the changes in the FTIR spectrum and the variations in sensor surface roughness and structure obtained by AFM analysis confirmed DA adsorption on the sensing layer. Based on these observations, CS/Au bilayer has enhanced the performance of this plasmonic sensor, which showed promising importance as a simple, low-cost, and reliable platform for DA sensing.

Combination of an optical waveguide platform and ultra-thin spectrometer that enables increased surface plasmon resonance sensor compactness

A novel integrated surface plasmon resonance (SPR) sensor that combines an optical waveguide platform and an ultra-thin spectrometer is proposed. The core of the proposed method is a special-shaped optical waveguide structure that employs a wedge-shaped incident surface, which changes the position of the total reflection of the incident light on the sagittal plane without affecting the direction of propagation on the tangential plane. The parameters of the sensing module with the integrated SPR sensor and spectrometer module were designed and optimized to achieve higher performance in a compact optical waveguide platform. An experimental system was built based on the theoretical model, and the spectral sensitivity of the system was analyzed before sample detection, and the results showed that the spectral resolution in the working range could reach 9.9 nm. The refractive index sensitivity of this novel SPR sensor was 3186 nm/RIU with good stability by detecting different concentrations of sodium chloride samples. This new structure does not require an external spectrometer, thereby enabling an increase in the compactness of the SPR sensing system. The proposed method can provide a novel idea for the miniaturization of SPR sensors.