Development of SPR biosensor for the detection of human hepatitis B virus using plasma-treated parylene-N film

Advancing Sensitivity in Guided-Wave Surface Plasmon Resonance Sensor through Integration of 2D BlueP/MoS2 Hybrid Layers

The surface plasmon resonance (SPR) signal, generated from the Kretschmann configuration, has been developed as an effective detection technology in chemical and biological sensors. The sensitivity of SPR signals to changes in the surrounding media makes it a valuable tool, as even a slight variation in refractive index can cause a significant change in SPR signals, such as phase, intensity, and resonance angle. However, the detection of ultralow changes in refractive index, which occur in chemical reactions or biological actions, remains a challenge for conventional SPR sensors due to their limited sensitivity. To overcome this limitation, we theoretically propose a novel guided-wave SPR (GWSPR) configuration coated with a few-layer blue phosphorene (blueP)/MoS2 hybrid structure. This configuration aims to enhance the electric field and subsequently achieve a significant improvement in sensitivity. The results of our study demonstrate that the proposed blueP/MoS2-based GWSPR sensor exhibits a high sensitivity of 290°/RIU, which represents an impressive enhancement of approximately 82.4% compared to the conventional Au-based SPR sensor. This advancement addresses the challenge of detecting ultralow changes in refractive index and offers significant potential for enhancing the performance of chemical and biological sensors.

Functionalized Parylene Films for Enhancement of Antibody Production by Hybridoma Cells

In this study, the influence of microenvironments on antibody production of hybridoma cells was analyzed using six types of functionalized parylene films, parylene-N and parylene-C (before and after UV radiation), parylene-AM, and parylene-H, and using polystyrene as a negative control. Hybridoma cells were cultured on modified parylene films that produced a monoclonal antibody against the well-known fungal toxin ochratoxin-A. Surface properties were analyzed for each parylene film, such as roughness, chemical functional groups, and hydrophilicity. The proliferation rate of the hybridoma cells was observed for each parylene film by counting the number of adherent cells, and the total amount of produced antibodies from different parylene films was estimated using indirect ELISA. In comparison with the polystyrene, the antibody-production by parylene-H and parylene-AM was estimated to be observed to be as high as 210-244% after the culture of 24 h. These results indicate that the chemical functional groups of the culture plate could influence antibody production. To analyze the influence of the microenvironments of the modified parylene films, we performed cell cycle analysis to estimate the ratio of the G0/G1, S, and G2/M phases of the hybridoma cells on each parylene film. From the normalized proportion of phases of the cell cycle, the difference in antibody production from different surfaces was considered to result from the difference in the proliferation rate of hybridoma cells, which occurred from the different physical and chemical properties of the parylene films. Finally, protein expression was analyzed using an mRNA array to determine the effect of parylene films on protein expression in hybridoma cells. The expression of three antibody production-related genes (CD40, Sox4, and RelB) was analyzed in hybridoma cells cultured on modified parylene films.

Plasma Surface Engineering of Natural and Sustainable Polymeric Derivatives and Their Potential Applications

Recently, natural as well as synthetic polymers have been receiving significant attention as candidates to replace non-renewable materials. With the exponential developments in the world each day, the collateral damage to the environment is incessant. Increased demands for reducing pollution and energy consumption are the driving force behind the research related to surface-modified natural fibers (NFs), polymers, and various derivatives of them such as natural-fiber-reinforced polymer composites. Natural fibers have received special attention for industrial applications due to their favorable characteristics, such as low cost, abundance, light weight, and biodegradable nature. Even though NFs offer many potential applications, they still face some challenges in terms of durability, strength, and processing. Many of these have been addressed by various surface modification methodologies and compositing with polymers. Among different surface treatment strategies, low-temperature plasma (LTP) surface treatment has recently received special attention for tailoring surface properties of different materials, including NFs and synthetic polymers, without affecting any of the bulk properties of these materials. Hence, it is very important to get an overview of the latest developments in this field. The present article attempts to give an overview of different materials such as NFs, synthetic polymers, and composites. Special attention was placed on the low-temperature plasma-based surface engineering of these materials for diverse applications, which include but are not limited to environmental remediation, packaging, biomedical devices, and sensor development.

SPR Based Biosensing Chip for COVID-19 Diagnosis-A Review

Surface Plasmon Resonance (SPR) techniques are highly accurate in detecting biomolecular like blood group measurement, food adulteration, milk adulteration and recently developing as a rapid detection for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. In order to validate the clinical diagnosis, Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) of nasopharyngeal swabs has been utilized, which is time consuming and expensive. For fast and accurate detection of the SARS-CoV-2 virus, SPR based biosensing chips are described in this review article. SPR sensors have the potential to be employed for fast, accurate, and portable SARS-CoV-2 virus diagnosis. To combat the SARS-CoV-2 pandemic, there is considerable interest in creating innovative biosensors that are quick, reliable, and sensitive for COVID-19 diagnosis.

SPR-Based Sensor for the Early Detection or Monitoring of Kidney Problems

SPR-based technology has emerged as one of the most versatile optical tools for analyzing the binding mechanism of molecular interaction due to its inherent advantages in sensing applications, such as real-time, label-free, and high sensitivity characteristics. SPR is widely used in various fields, including healthcare, environmental management, and food-borne illness analysis. Meanwhile, kidney disease has grown to be one of the world's most serious public health problems in recent decades, resulting in physical degeneration and even death. As a result, several studies have published their findings regarding developing of reliable sensor technology based on the SPR phenomenon. However, an integrated and comprehensive discussion regarding the application of SPR-based sensors for detecting of kidney disease has not yet been found. Therefore, this review will discuss the recent advancements in the development of SPR-based sensors for monitoring kidney-related diseases. Numerous SPR configurations will be discussed, including Kretschmann, Otto, optical fiber-based SPR, and LSPR, which are all used to detect analytes associated with kidney disease, including urea, creatinine, glucose, uric acid, and dopamine. This review aims to show the broad application of SPR sensors which encouraged the development of SPR sensors for kidney problems monitoring.

Surface plasmon resonance biosensor with laser heterodyne feedback for highly-sensitive and rapid detection of COVID-19 spike antigen

The ongoing outbreak of the COVID-19 has highlighted the importance of the pandemic prevention and control. A rapid and sensitive antigen assay is crucial in diagnosing and curbing pandemic. Here, we report a novel surface plasmon resonance biosensor based on laser heterodyne feedback interferometry for the detection of SARS-CoV-2 spike antigen, which is achieved by detecting the tiny difference in refractive index between different antigen concentrations. The biosensor converts the refractive index changes at the sensing unit into the intensity changes of light through surface plasmon resonance, achieving label-free and real-time detection of biological samples. Moreover, the gain amplification effect of the laser heterodyne feedback interferometry further improved the sensitivity of this biosensor. The biosensor can rapidly respond to continuous and periodic changes in the refractive index with a high resolution of 3.75 × 10-8 RIU, demonstrating the repeatability of the biosensor. Afterwards, the biosensor is immobilized by the anti-SARS-CoV-2 spike monoclonal antibodies, thus realizing the specific recognition of the antigen. The biosensor exhibited a high sensitivity towards the concentration of the antigen with a linear dynamic range of five orders of magnitude and a resolution of 0.08 pg/mL. These results indicate that this principle can be used as a rapid diagnostic method for COVID-19 antigens without sample labelling.

Flexible terahertz metamaterial biosensor for label-free sensing of serum tumor marker modified on a non-metal area

Terahertz (THz) metamaterials for rapid label-free sensing show application potential for the detection of cancer biomarkers. A novel flexible THz metamaterial biosensor based on a low refraction index parylene-C substrate is proposed. The biomarkers are modified on non-metal areas by a three-step modification method that simplifies the modification steps and improves the modified effectivity. Simulation results for non-metal modification illustrate that a bulk refractive index sensitivity of 325 GHz/RIU is achieved, which is larger than that obtained for the traditional metal modification (147 GHz/RIU). Meanwhile, several fluorescence experiments proved the uniform modification effect and selective adsorption capacity of the non-metal modification method. The concentration of the carcinoembryonic antigen (CEA) biomarkers for breast cancer patients tested using this THz biosensor is found to be consistent with results obtained from traditional clinical tests. The limit of detection reaches 2.97 ng/mL. These findings demonstrate that the flexible THz metamaterial biosensor can be extensively used for the rapid detection of cancer biomarkers in the future.

In Situ Regeneration of Silicon Microring Biosensors Coated with Parylene C

Optical biosensors support disease diagnostic applications, offering high accuracy and sensitivity due to label-free detection and their optical resonance enhancement. However, optical biosensors based on noble metal nanoparticles and precise micro-electromechanical system technology are costly, which is an obstacle for their applications. Here, we proposed a biosensor reuse method with nanoscale parylene C film, taking the silicon-on-insulator microring resonator biosensor as an example. Parylene C can efficiently adsorb antibody by one-step modification without any surface treatment, which simplifies the antibody modification process of sensors. Parylene C (20 nm thick) was successfully coated on the surface of the microring to modify anti-carcinoembryonic antigen (anti-CEA) and specifically detect CEA. After sensing, parylene C was successfully removed without damaging the sensing surface for the sensor reusing. The experimental results demonstrate that the sensing response did not change significantly after the sensor was reused more than five times, which verifies the repeatability and reliability of the reusable method by using parylene C. This framework can potentially reduce the cost of biosensors and promote their further applications.

Optical Biosensors for Diagnostics of Infectious Viral Disease: A Recent Update

The design and development of biosensors, analytical devices used to detect various analytes in different matrices, has emerged. Biosensors indicate a biorecognition element with a physicochemical analyzer or detector, i.e., a transducer. In the present scenario, various types of biosensors have been deployed in healthcare and clinical research, for instance, biosensors for blood glucose monitoring. Pathogenic microbes are contributing mediators of numerous infectious diseases that are becoming extremely serious worldwide. The recent outbreak of COVID-19 is one of the most recent examples of such communal and deadly diseases. In efforts to work towards the efficacious treatment of pathogenic viral contagions, a fast and precise detection method is of the utmost importance in biomedical and healthcare sectors for early diagnostics and timely countermeasures. Among various available sensor systems, optical biosensors offer easy-to-use, fast, portable, handy, multiplexed, direct, real-time, and inexpensive diagnosis with the added advantages of specificity and sensitivity. Many progressive concepts and extremely multidisciplinary approaches, including microelectronics, microelectromechanical systems (MEMSs), nanotechnologies, molecular biology, and biotechnology with chemistry, are used to operate optical biosensors. A portable and handheld optical biosensing device would provide fast and reliable results for the identification and quantitation of pathogenic virus particles in each sample. In the modern day, the integration of intelligent nanomaterials in the developed devices provides much more sensitive and highly advanced sensors that may produce the results in no time and eventually help clinicians and doctors enormously. This review accentuates the existing challenges engaged in converting laboratory research to real-world device applications and optical diagnostics methods for virus infections. The review's background and progress are expected to be insightful to the researchers in the sensor field and facilitate the design and fabrication of optical sensors for life-threatening viruses with broader applicability to any desired pathogens.

Advances and Future Perspective on Detection Technology of Human Norovirus

Human norovirus (HuNoV) is a food-borne pathogen that causes acute gastroenteritis in people of all ages worldwide. However, no approved vaccines and antiviral drugs are available at present. Therefore, the development of accurate and rapid detection technologies is important in controlling the outbreak of HuNoVs. This paper reviewed the research progress on HuNoV detection, including immunological methods, molecular detection and biosensor technology. Immunological methods and molecular detection technologies are still widely used for HuNoV detection. Furthermore, biosensors will become an emerging developmental direction for the rapid detection of HuNoVs because of their high sensitivity, low cost, easy operation and suitability for onsite detection.

Plasmonic Metasurfaces Based on Pyramidal Nanoholes for High-Efficiency SERS Biosensing

An inverted pyramidal metasurface was designed, fabricated, and studied at the nanoscale level for the development of a label-free pathogen detection on a chip platform that merges nanotechnology and surface-enhanced Raman scattering (SERS). Based on the integration and synergy of these ingredients, a virus immunoassay was proposed as a relevant proof of concept for very sensitive detection of hepatitis A virus, for the first time to our best knowledge, in a very small volume (2 μL), without complex signal amplification, allowing to detect a minimal virus concentration of 13 pg/mL. The proposed work aims to develop a high-flux and high-accuracy surface-enhanced Raman spectroscopy (SERS) nanobiosensor for the detection of pathogens to provide an effective method for early and easy water monitoring, which can be fast and convenient.

Enhenced cell adhesion on collagen I treated parylene-C microplates

On account of unique mechanical property and inertia, parylene-C has become a promising material for microdevices especially in three-dimensional microstructures loaded with cells. However, parylene-C is not favorable for cell adhesion, and a routine procedure is to modify it with a new adhesive layer. Herein, the parylene-C substrates with or without collagen Ӏ (Col-I) coating were adopted to estimate the influence of micro-environment change on cell attachment and spreading. After modification with Col-I, cauliflower-like particles presented on the substrate surface. Contact angle was significantly decreased after Col-I modification, which suggested the surface hydrophilicity was enhanced. Furthermore, cells cultured on parylene-C surface with Col-I treatment showed increased proliferation rate and spreading areas. In order to test the adhesion strength, a series of fixed size parylene-C microplates was fabricated, and cell suspension concentration was adjusted to culture a single cell on one microplate. The microplate was folded by the autogenous shrinkage force of cell. The folding angles of parylene-C microplates with Col-I treatment exhibited higher folding angle (112.6 ± 15.6°) than untreated samples (46.7 ± 5.9°). The work proved the existence of Col-I layer was particularly important, especially in analysis of cells mechanics using parylene-C microplate as a substrate.

Role of plasmonics in detection of deadliest viruses: a review

Viruses have threatened animal and human lives since a long time ago all over the world. Some of these tiny particles have caused disastrous pandemics that killed a large number of people with subsequent economic downturns. In addition, the quarantine situation itself encounters the challenges like the deficiency in the online educational system, psychiatric problems and poor international relations. Although viruses have a rather simple protein structure, they have structural heterogeneity with a high tendency to mutation that impedes their study. On top of the breadth of such worldwide worrying issues, there are profound scientific gaps, and several unanswered questions, like lack of vaccines or antivirals to combat these pathogens. Various detection techniques like the nucleic acid test, immunoassay, and microscopy have been developed; however, there is a tradeoff between their advantages and disadvantages like safety in sample collecting, invasiveness, sensitivity, response time, etc. One of the highly resolved techniques that can provide early-stage detection with fast experiment duration is plasmonics. This optical technique has the capability to detect viral proteins and genomes at the early stage via highly sensitive interaction between the biological target and the plasmonic chip. The efficiency of this technique could be proved using commercialized techniques like reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) techniques. In this study, we aim to review the role of plasmonic technique in the detection of 11 deadliest viruses besides 2 common genital viruses for the human being. This is a rapidly moving topic of research, and a review article that encompasses the current findings may be useful for guiding strategies to deal with the pandemics. By investigating the potential aspects of this technique, we hope that this study could open new avenues toward the application of point-of-care techniques for virus detection at early stage that may inhibit the progressively hygienic threats.

Nano-layered surface plasmon resonance-based highly sensitive biosensor for virus detection: A theoretical approach to detect SARS-CoV-2

The outbreak of the coronavirus disease (COVID-19) pandemic has become a worldwide health catastrophe instigated by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Countries are battling to slow the spread of this virus by testing and treating patients, along with other measures such as prohibiting large gatherings, maintaining social distance, and frequent, thorough hand washing, as no vaccines or medicines are available that could effectively treat infected people for different types of SARS-CoV-2 variants. However, the testing procedure to detect this virus is lengthy. This study proposes a surface plasmon resonance-based biosensor for fast detection of SARS-CoV-2. The sensor employs a multilayered configuration consisting of TiO₂-Ag-MoSe₂ graphene with a BK7 prism. Antigen-antibody interaction was considered the principle for this virus detection. Immobilized CR3022 antibody molecules for detecting SARS-CoV-2 antigens (S-glycoprotein) are used for this sensor. It was found that the proposed sensor's sensitivity (194°/RIU), quality factor (54.0390 RIU^-1), and detection accuracy (0.2702) outperformed those of other single and multilayered structures. This study could be used as a theoretical base and primary step in constructing an actual sensor.

Future antiviral polymers by plasma processing

Coronavirus disease 2019 (COVID-19) is largely threatening global public health, social stability, and economy. Efforts of the scientific community are turning to this global crisis and should present future preventative measures. With recent trends in polymer science that use plasma to activate and enhance the functionalities of polymer surfaces by surface etching, surface grafting, coating and activation combined with recent advances in understanding polymer-virus interactions at the nanoscale, it is promising to employ advanced plasma processing for smart antiviral applications. This trend article highlights the innovative and emerging directions and approaches in plasma-based surface engineering to create antiviral polymers. After introducing the unique features of plasma processing of polymers, novel plasma strategies that can be applied to engineer polymers with antiviral properties are presented and critically evaluated. The challenges and future perspectives of exploiting the unique plasma-specific effects to engineer smart polymers with virus-capture, virus-detection, virus-repelling, and/or virus-inactivation functionalities for biomedical applications are analysed and discussed.

Monitoring hepatitis B by using point-of-care testing: biomarkers, current technologies, and perspectives

Introduction: Liver diseases caused by hepatitis B virus (HBV) are pandemic infectious diseases that seriously endanger human health, conventional diagnosis methods can not meet the requirements in resource-limited areas. The point of acre detection methods can easily resolve those problems. Herein, we review the most recent advances in POC-based hepatitis B detection methods and present some recommendations for future development. It aims to provide ideas for future research.Areas covered: Epidemiological data on Hepatitis B, conventional diagnostic methods for hepatitis B detection, some latest point of care detection methods for hepatitis B detection and list out the recommendations for future development.Expert opinion: This manuscript summarized traditional biomarkers of different hepatitis B stages and recent-developed POCT platforms (including microfluidic platforms and lateral-flow strips) and discuss the challenges associated with their use. Some emerging biomarkers that can be used in hepatitis B diagnosis are also listed. This manuscript has certain guiding significance to the development of hepatitis B detection.

Simultaneous Analysis of Multiple Cancer Biomarkers Using MALDI-TOF Mass Spectrometry Based on a Parylene-Matrix Chip

Recently, the parylene-matrix chip was developed for quantitative analysis of small molecules less than 1 kDa. In this study, MALDI-TOF MS based on the parylene-matrix chip was performed to clinically diagnose intrahepatic cholangiocarcinoma (IHCC) and colorectal cancer (CRC). The parylene-matrix chip was applied for the detection of small cancer biomarkers, including N-methyl-2-pyridone-5-carboxamide (2PY), glutamine, lysophosphatidylcholine (LPC) 16:0, and LPC 18:0. The feasibility of MALDI-TOF MS based on the parylene-matrix chip was confirmed via analysis of spot-to-spot and shot-to-shot reproducibility. Serum metabolite markers of IHCC, N-methyl-2-pyridone-5-carboxamide (2PY), and glutamine were quantified using MALDI-TOF MS based on the parylene-matrix chip. For clinical diagnosis of CRC, two water-insoluble (barely soluble) biomarkers, lysophosphatidylcholine (LPC) 16:0 and LPC 18:0, were quantified. Finally, glutamine and LPC 16:0 were simultaneously detected at a range of concentrations in sera from colon cancer patients using the parylene-matrix chip. Thus, this method yielded high-throughput detection of cancer biomarkers for the mixture samples of water-soluble analytes (2PY and glutamine) and water-insoluble analytes (LPC 16:0 and LPC 18:0).

Plasmonic-based platforms for diagnosis of infectious diseases at the point-of-care

Infectious diseases such as HIV-1/AIDS, tuberculosis (TB), hepatitis B (HBV), and malaria still exert a tremendous health burden on the developing world, requiring rapid, simple and inexpensive diagnostics for on-site diagnosis and treatment monitoring. However, traditional diagnostic methods such as nucleic acid tests (NATs) and enzyme linked immunosorbent assays (ELISA) cannot be readily implemented in point-of-care (POC) settings. Recently, plasmonic-based biosensors have emerged, offering an attractive solution to manage infectious diseases in the developing world since they can achieve rapid, real-time and label-free detection of various pathogenic biomarkers. Via the principle of plasmonic-based optical detection, a variety of biosensing technologies such as surface plasmon resonance (SPR), localized surface plasmon resonance (LSPR), colorimetric plasmonic assays, and surface enhanced Raman spectroscopy (SERS) have emerged for early diagnosis of HIV-1, TB, HBV and malaria. Similarly, plasmonic-based colorimetric assays have also been developed with the capability of multiplexing and cellphone integration, which is well suited for POC testing in the developing world. Herein, we present a comprehensive review on recent advances in surface chemistry, substrate fabrication, and microfluidic integration for the development of plasmonic-based biosensors, aiming at rapid management of infectious diseases at the POC, and thus improving global health.

Liquid gated ZnO nanorod FET sensor for ultrasensitive detection of Hepatitis B surface antigen with vertical electrode configuration

Detection of the Hepatitis-B surface antigen at the attomolar level is demonstrated using antibody functionalized liquid gated ZnO nanorods field effect transistor (FET) biosensor with vertical electrode configuration. The sensor is operated in heterodyne mode at high frequency to overcome the problem of Debye screening effect in physiological analyte. Enhanced penetration of the electric field lines through the nanorods enables significant improvement in the limit of detection and sensitivity compared to that of the conventional lateral electrode configuration. The combined effect of the probable change in the threshold voltage and the carrier mobility for vertical electrode configuration lead to a sensitivity of around 75% at 1 fM (which is an enhancement by 200%) and a detection limit of 20 aM with a dynamic range from 20 aM to 1 pM. The detection limit which is achieved with the proposed label free sensor in physiological analyte using antibodies is lowered by more than three orders of magnitude compared to the existing reports.

Chronoamperometry-Based Redox Cycling for Application to Immunoassays

In this work, the chronoamperometry-based redox cycling of 3,3',5,5'-tetramethylbenzidine (TMB) was performed by using interdigitated electrode (IDE). The signal was obtained from two sequential chronoamperometric profiles: (1) with the generator at the oxidative potential of TMB and the collector at the reductive potential of TMB, and (2) with the generator at the reductive potential of TMB and the collector at the oxidative potential of TMB. The chronoamperometry-based redox cycling (dual mode) showed a sensitivity of 1.49 μA/OD, and the redox cycling efficiency was estimated to be 94% (n = 10). The sensitivities of conventional redox cycling with the same interdigitated electrode and chronoamperometry using a single working electrode (single mode) were estimated to be 0.67 μA/OD and 0.18 μA/OD, respectively. These results showed that the chronoamperometry-based redox cycling (dual mode) could be more effectively used to quantify the oxidized TMB than other amperometric methods. The chronoamperometry-based redox cycling (dual mode) was applied to immunoassays using a commercial ELISA kit for medical diagnosis of the human hepatitis B virus surface antigen (hHBsAg). Finally, the chronoamperometry-based redox cycling (dual mode) provided more than a 10-fold higher sensitivity than conventional chronoamperometry using a single working electrode (single mode) when applied to a commercial ELISA kit for medical diagnosis of hHBsAg.

Silica nanoparticles coated by poly(acrylic acid) brushes via host-guest interactions for detecting DNA sequence of Hepatitis B virus

Poly(acrylic acid) (PAA) brushes coated onto silica nanoparticles have been widely utilized in bioassays due to their abilities of providing favorable microenvironments and ensuring good biological activities for biomolecules. However, traditional PAA brushes are synthesized by reversible addition-fragmentation chain transfer polymerization. Hence, it is generally difficult to control and characterize the molecular weight of the PAA brushes, which may depress the reproducibility and bring more uncertain results. Herein, atom transfer radical polymerization method is employed to synthesize β-cyclodextrin-cored PAA with uniform and controllable molecular weight. After loading on the surfaces of adamantane-functionalized silica nanoparticles via host-guest interactions, glucose oxidase and probe single strand DNA (ssDNA) are further immobilized on the as-prepared nanoparticles. Meanwhile, capture ssDNA is functionalized on amino modified magnetic beads. In the presence of ssDNA sequence of Hepatitis B Virus (HBV) containing completely matched sequence of both probe and capture ssDNA, a bioconjugate is formed and can be separated by an external magnet. The isolated glucose oxidase can further catalyze glucose into gluconic acid and H₂O₂, and then reduce HAuCl₄ on Au seeds. By monitoring the absorption intensity change of the Au NPs at 530nm, the proposed biosensor with novel signal amplification probes can be used to detect DNA sequence of HBV with high sensitivity and selectivity in both buffer and serum samples. This developed strategy has presented a new way to construct silica nanoparticles coated by PAA brushes for the fields of clinical diagnosis and other life sciences.

Wide dynamic range of surface-plasmon-resonance-based assay for hepatitis B surface antigen antibody optimal detection in comparison with ELISA

Limit of detection (LOD), limit of quantification, and the dynamic range of detection of hepatitis B surface antigen antibody (anti-HBs) using a surface plasmon resonance (SPR) chip-based approach with Pichia pastoris-derived recombinant hepatitis B surface antigen (HBsAg) as recognition element were established through the scouting for optimal conditions for the improvement of immobilization efficiency and in the use of optimal regeneration buffer. Recombinant HBsAg was immobilized onto the sensor surface of a CM5 chip at a concentration of 150 mg/L in sodium acetate buffer at pH 4 with added 0.6% Triton X-100. A regeneration solution of 20 mM HCl was optimally found to effectively unbind analytes from the ligand, thus allowing for multiple screening cycles. A dynamic range of detection of ∼0.00098-0.25 mg/L was obtained, and a sevenfold higher LOD, as well as a twofold increase in coefficient of variance of the replicated results, was shown as compared with enzyme-linked immunosorbent assay (ELISA). Evaluation of the assay for specificity showed no cross-reactivity with other antibodies tested. The ability of SPR chip-based assay and ELISA to detect anti-HBs in human serum was comparable, indicating that the SPR chip-based assay with its multiple screening capacity has greater advantage over ELISA.

Enhanced Fluorescence ELISA Based on HAT Triggering Fluorescence "Turn-on" with Enzyme-Antibody Dual Labeled AuNP Probes for Ultrasensitive Detection of AFP and HBsAg

At present, enzyme-linked immunosorbent assay (ELISA) is considered to be the most appropriate approach in clinical biomarker detection, with good specificity, low cost, and straightforward readout. However, unsatisfactory sensitivity severely hampers its wide application in clinical diagnosis. Herein, we designed a new kind of enhanced fluorescence enzyme-linked immunosorbent assay (FELISA) based on the human alpha-thrombin (HAT) triggering fluorescence "turn-on" signals. In this system, detection antibodies (Ab₂) and HAT were labeled on the gold nanoparticles (AuNPs) to form the detection probes, and a bisamide derivative of Rhodamine₁₁₀ with fluorescence quenched served as the substrate of HAT. After the sandwich immunoreaction, HAT on the sandwich structure could catalyze the cleavage of the fluorescence-quenched substrate, leading to a strong fluorescence signal for sensing ultralow levels of alpha fetoprotein (AFP) and hepatitis B virus surface antigen (HBsAg). Under the optimized reaction conditions, AFP and HBsAg were detected at the ultralow concentrations of 10^-8 ng mL^-1 and 5 × 10^-4 IU mL^-1, respectively, which were at least 10⁴ times lower than those of the conventional fluorescence assay and 10⁶ times lower than those of the conventional ELISA. In addition, we further discussed the efficiency of the sensitive FELISA in clinical serum samples, showing great potential in practical applications.

Label-free detection of hepatitis B virus using solution immersed silicon sensors

Highly sensitive solution immersed silicon (SIS) biosensors were developed for detection of hepatitis B virus (HBV) infection in the early stage. The ultrasensitivity for overlayer thickness at the nonreflecting condition for the p-polarized wave is the basis of SIS sensing technology. The change in thickness due to biomolecular interactions and change in refractive index of the surrounding buffer medium were assessed simultaneously using two separate ellipsometric parameters (Ψ and Δ), respectively, from a single sensing spot. A direct antigen-antibody affinity assay was used to detect and quantify hepatitis B surface antigen (HBsAg), which is the early stage biomarker for HBV infection. The detection limit of 10 pg/ml was achieved for HBsAg in the human blood serum, which is comparable with the results of enzyme-linked immunosorbent assay and other hybrid assays. The SIS sensor's response time was less than 10 min. The SIS sensors exhibit excellent stability and high signal-to-noise ratio, and are cost-effective, which makes them a suitable candidate for point-of-care applications.

Plasmonic Hepatitis B Biosensor for the Analysis of Clinical Saliva

A biosensor for the detection of hepatitis B antibodies in clinical saliva was developed. Compared to conventional analysis of blood serum, it offers the advantage of noninvasive collection of samples. Detection of biomarkers in saliva imposes two major challenges associated with the low analyte concentration and increased surface fouling. The detection of minute amounts of hepatitis B antibodies was performed by plasmonically amplified fluorescence sandwich immunoassay. To have access to specific detection, we prevented the nonspecific adsorption of biomolecules present in saliva by brushes of poly[(N-(2-hydroxypropyl) methacrylamide)-co-(carboxybetaine methacrylamide)] grafted from the gold sensor surface and post modified with hepatitis B surface antigen. Obtained results were validated against the response measured with ELISA at a certified laboratory using serum from the same patients.

Dispersion Curve Engineering of TiO₂/Silver Hybrid Substrates for Enhanced Surface Plasmon Resonance Detection

As surface plasmon resonance (SPR)-based biosensors are well translated into biological, chemical, environmental, and clinical fields, it is critical to further realize stable and sustainable systems, avoiding oxidation susceptibility of metal films—in particular, silver substrates. We report an enhanced SPR detection performance by incorporating a TiO₂ layer on top of a thin silver film. A uniform TiO₂ film fabricated by electron beam evaporation at room temperature is an effective alternative in bypassing oxidation of a silver film. Based on our finding that the sensor sensitivity is strongly correlated with the slope of dispersion curves, SPR sensing results obtained by parylene film deposition shows that TiO₂/silver hybrid substrates provide notable sensitivity improvement compared to a conventional bare silver film, which confirms the possibility of engineering the dispersion characteristic according to the incidence wavelength. The reported SPR structures with TiO₂ films enhance the sensitivity significantly in water and air environments and its overall qualitative trend in sensitivity improvement is consistent with numerical simulations. Thus, we expect that our approach can extend the applicability of TiO₂-mediated SPR biosensors to highly sensitive detection for biomolecular binding events of low concentrations, while serving a practical and reliable biosensing platform.

A magnetite suspension-based washing method for immunoassays using Escherichia coli cells with autodisplayed Z-domains

Escherichia coli cells with autodisplayed Z-domains have been used for immunoassays of specific target analytes. In this study, a magnetite suspension was used for the washing step in immunoassays of E. coli cells with autodisplayed Z-domains. This approach enhanced the washing conditions for these immunoassays by determining (1) the optimal concentration of the magnetite suspension, (2) the capacity of the magnetite suspension-based washing method to recover E. coli cells, and (3) the level at which the activity of autodisplayed Z-domains is maintained. In immunoassays of C-reactive protein (CRP), the immunoassay incorporating the magnetite suspension-based washing method showed a sensitivity and limit of detection considerably higher than those of the conventional centrifugation-based washing method. The results indicated that immunoassays incorporating the magnetite suspension-based washing method are effective for medical diagnoses based on CRP assay.

Hepatitis B plasmonic biosensor for the analysis of clinical serum samples

A plasmonic biosensor for rapid detection of protein biomarkers in complex media is reported. Clinical serum samples were analyzed by using a novel biointerface architecture based on poly[(N-(2-hydroxypropyl) methacrylamide)-co-(carboxybetaine methacrylamide)] brushes functionalized with bioreceptors. This biointerface provided an excellent resistance to fouling even after the functionalization and allowed for the first time the direct detection of antibodies against hepatitis B surface antigen (anti-HBs) in clinical serum samples using surface plasmon resonance (SPR). The fabricated SPR biosensor allowed discrimination of anti-HBs positive and negative clinical samples in 10min. Results are validated by enzyme-linked immunoassays of the sera in a certified laboratory. The sensor could be regenerated by simple treatment with glycine buffer.

Analysis of benzylpenicillin in milk using MALDI-TOF mass spectrometry with top-down synthesized TiO2 nanowires as the solid matrix

In this work, the wet-corrosion process for the synthesis of titanium oxide (TiO2) nanowires in the anatase phase was optimized as the solid matrix in MALDI-TOF mass spectrometry, and the solid matrix of the TiO2 nanowires was applied to the detection of antibiotics in a daily milk sample. The influence of the alkali concentration and the heat treatment temperature on the crystal structure of the TiO2 nanowires was investigated. The ionization activity of the TiO2 nanowires was estimated for each synthetic condition using amino acids as model analytes with low molecular weights. For the detection of antibiotics in milk, benzylpenicillin was spiked in daily milk samples, and MALDI-TOF mass spectrometry with the TiO2 nanowires was demonstrated to detect the benzylpenicillin at the cut-off concentration of the EU directive.

Recent Progress in Lectin-Based Biosensors

This article reviews recent progress in the development of lectin-based biosensors used for the determination of glucose, pathogenic bacteria and toxins, cancer cells, and lectins. Lectin proteins have been widely used for the construction of optical and electrochemical biosensors by exploiting the specific binding affinity to carbohydrates. Among lectin proteins, concanavalin A (Con A) is most frequently used for this purpose as glucose- and mannose-selective lectin. Con A is useful for immobilizing enzymes including glucose oxidase (GOx) and horseradish peroxidase (HRP) on the surface of a solid support to construct glucose and hydrogen peroxide sensors, because these enzymes are covered with intrinsic hydrocarbon chains. Con A-modified electrodes can be used as biosensors sensitive to glucose, cancer cells, and pathogenic bacteria covered with hydrocarbon chains. The target substrates are selectively adsorbed to the surface of Con A-modified electrodes through strong affinity of Con A to hydrocarbon chains. A recent topic in the development of lectin-based biosensors is a successful use of nanomaterials, such as metal nanoparticles and carbon nanotubes, for amplifying output signals of the sensors. In addition, lectin-based biosensors are useful for studying glycan expression on living cells.

Unveiling the hyperbolic thermal behaviour of poly(p-phenylene alkylene)s

A series of poly(p-phenylene alkylene)s with methylene run lengths ranging from 8 to 40 were obtained by ADMET polymerization of symmetrical α,ω-diene monomers and subsequent exhaustive hydrogenation.