Microelectrical sensors as emerging platforms for protein biomarker detection in point-of-care diagnostics

Impedimetric Sensing: An Emerging Tool for Combating the COVID-19 Pandemic

The COVID-19 pandemic revealed a pressing need for the development of sensitive and low-cost point-of-care sensors for disease diagnosis. The current standard of care for COVID-19 is quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). This method is sensitive, but takes time, effort, and requires specialized equipment and reagents to be performed correctly. This make it unsuitable for widespread, rapid testing and causes poor individual and policy decision-making. Rapid antigen tests (RATs) are a widely used alternative that provide results quickly but have low sensitivity and are prone to false negatives, particularly in cases with lower viral burden. Electrochemical sensors have shown much promise in filling this technology gap, and impedance spectroscopy specifically has exciting potential in rapid screening of COVID-19. Due to the data-rich nature of impedance measurements performed at different frequencies, this method lends itself to machine-leaning (ML) algorithms for further data processing. This review summarizes the current state of impedance spectroscopy-based point-of-care sensors for the detection of the SARS-CoV-2 virus. This article also suggests future directions to address the technology's current limitations to move forward in this current pandemic and prepare for future outbreaks.

Development of Gold Nanoparticle Micropatterns for the Electrical Detection of Proteins

Protein analysis can be used to efficiently detect the early stages of various diseases. However, conventional protein detection platforms require expensive or complex equipment, which has been a major obstacle to their widespread application. In addition, uncertain signals from non-specific adhesion interfere with the precise interpretation of the results. To overcome these problems, the development of a technique that can detect the proteins in a simple method is needed. In this study, a platform composed of gold nanoparticles (GNPs) was fabricated through a simple imprinting method for protein detection. The corrugated surface naturally formed by the nanoparticle assemblies simultaneously increases the efficiency of adhesion and binding with analytes and reduces undesired interactions. After forming the GNP micropatterns, post-functionalization with both cationic and neutral ligands was performed on the surface to manipulate their electrostatic interaction with proteins. Upon protein binding, the change in the electrical values of the micropatterns was recorded by using a resistance meter. The resistance of the positively charged micropatterns was found to increase due to the electrostatic interaction with proteins, while no significant change in resistance was observed for the neutral micropatterns after immersion in a protein solution. Additionally, the selective adsorption of fluorescent proteins onto the micropatterns was captured using confocal microscopy. These simply imprinted GNP micropatterns are sensitive platforms that can detect various analytes by measuring the electrical resistance with portable equipment.

Recent advances in developing biosensing based platforms for neonatal sepsis

Neonatal sepsis is a bloodstream infection primarily caused by Escherichia coli (E. coli), Group B Streptococcus (GBS), Listeria monocytogenes, Haemophilus influenzae, S. aureus, Klebsiella spp. and non-typhoidal Salmonella bacteria. Neonatal Sepsis is referred as a critical response to the infection in the neonatal period that can lead to the failure of body organs and thereby causing damage to the tissues resulting in death of the neonates. Nearly 4 million deaths across the world are occurred due to neonatal sepsis infections. In order to prevent the bloodstream infections in the neonates, it is indispensable to diagnose the disease properly for appropriate treatment during the point of care. Numerous studies have been reported to identify major biomarkers associated with neonatal sepsis including Serum Amyloid A (SAA), C - reactive protein (CRP), Procalcitonin (PCT) and Lipopolysaccharide-binding protein (LBP). Distinct diagnostic platforms have also been developed detecting the presence of bloodstream infections including electrochemical, potentiometric, and impedimetric sensors. Recently, electrochemical biosensors with the integration of nanomaterials have emerged as a better platform for neonatal sepsis biomarkers detection. This review article summarizes the diverse screening platforms, evaluation parameters, and new advances based on implications of nanomaterials for the development of biosensors detecting neonatal sepsis infections. The review further elucidates the significance and future scope of distinctive platforms which are predominantly associated with detection of neonatal sepsis.

Biosensors for Detection of Human Placental Pathologies: A Review of Emerging Technologies and Current Trends

Substantial growth in the biosensor research has enabled novel, sensitive and point-of-care diagnosis of human diseases in the last decade. This paper presents an overview of the research in the field of biosensors that can potentially predict and diagnosis of common placental pathologies. A survey of biomarkers in maternal circulation and their characterization methods is presented, including markers of oxidative stress, angiogenic factors, placental debris, and inflammatory biomarkers that are associated with various pathophysiological processes in the context of pregnancy complications. Novel biosensors enabled by microfluidics technology and nanomaterials is then reviewed. Representative designs of plasmonic and electrochemical biosensors for highly sensitive and multiplexed detection of biomarkers, as well as on-chip sample preparation and sensing for automatic biomarker detection are illustrated. New trends in organ-on-a-chip based placental disease models are highlighted to illustrate the capability of these in vitro disease models in better understanding the complex pathophysiological processes, including mass transfer across the placental barrier, oxidative stress, inflammation, and malaria infection. Biosensor technologies that can be potentially embedded in the placental models for real time, label-free monitoring of these processes and events are suggested. Merger of cell culture in microfluidics and biosensing can provide significant potential for new developments in advanced placental models, and tools for diagnosis, drug screening and efficacy testing.

Role of heat shock proteins 70/90 in exercise physiology and exercise immunology and their diagnostic potential in sports

Heat shock proteins (HSPs) are molecular chaperones facilitating the unfolding or folding of secondary structures of proteins, their client proteins, in cellular stress situations. Various internal and external physiological and mechanical stress factors induce a homeostatic imbalance, followed by an increased expression of HSP70 and HSP90. Exercise is a stress factor, too, and its cumulative physiological perturbation manifests at a cellular level by threatening the protein homeostasis of various cell types. Consequently, an increase of HSP70/90 was described in plasma and mononuclear cells and various organs and tissues, such as muscle, liver, cardiac tissue, and brain, after an acute bout of exercise. The specific response of HSP70/90 seems to be strongly related to the modality of exercise, with several dependent factors such as duration, intensity, exercise type, subjects’ training status, and environmental factors, e.g., temperature. It is suggested that HSP70/90 play a major role in immune regulation and cell protection during exercise and in the efficiency of regeneration and reparation processes. During long-term training, HSP70/90 are involved in preconditioning and adaptation processes that might also be important for disease prevention and therapy. With regard to their highly sensitive and individual response to specific exercise and training modalities, this review discusses whether and how HSP70 and HSP90 can be applied as biomarkers for monitoring exercise and training.

A Hand-Held Point-of-Care Biosensor Device for Detection of Multiple Cancer and Cardiac Disease Biomarkers Using Interdigitated Capacitive Arrays

This paper presents a hand-held point-of-care device that incorporates a lab-on-a-chip module with interdigitated capacitive biosensors for label-free detection of multiple cancer and cardiovascular disease biomarkers. The developed prototype is comprised of a cartridge incorporating capacitive biodetection sensors, a sensitive capacitive readout electronics enclosed in a hand-held unit, and data analysis software calculating the concentration of biomarkers using previously stored reference database. The capacitive biodetection sensors are made of interdigitated circular electrodes, which are preactivated with single (for detecting one biomarker) or multiple specific antibodies (for detecting multiple disease biomarkers). Detection principle of capacitive biosensor is based on measuring the level of capacitance change between interdigitated electrode pairs induced by the change in dielectric constant due to affinity-based electron exchange in between antibodies/antigens and electrodes. The more antibody-antigens binding occurs, the more capacitance change is measured due to the change in dielectric constant of the capacitance media. The device uses preactivated ready-to-use cartridges embedded with capacitive biosensors with shelf-life of three months under optimal conditions, and is capable of onsite diagnosis and can report the result in less than 30 min. The device is verified with real patient blood samples for six different disease biomarkers.

Blood-Based Protein Biomarkers for the Management of Traumatic Brain Injuries in Adults Presenting to Emergency Departments with Mild Brain Injury: A Living Systematic Review and Meta-Analysis

Accurate diagnosis of traumatic brain injury (TBI) is critical to effective management and intervention, but can be challenging in patients with mild TBI. A substantial number of studies have reported the use of circulating biomarkers as signatures for TBI, capable of improving diagnostic accuracy and clinical decision making beyond current practice standards. We performed a systematic review and meta-analysis to comprehensively and critically evaluate the existing body of evidence for the use of blood protein biomarkers (S100 calcium binding protein B [S100B], glial fibrillary acidic protein [GFAP], neuron specific enolase [NSE], ubiquitin C-terminal hydrolase-L1 [UCH-L1]. tau, and neurofilament proteins) for diagnosis of intracranial lesions on CT following mild TBI. Effects of potential confounding factors and differential diagnostic performance of the included markers were explored. Further, appropriateness of study design, analysis, quality, and demonstration of clinical utility were assessed. Studies published up to October 2016 were identified through searches of MEDLINE^®, Embase, EBM Reviews, the Cochrane Library, World Health Organization (WHO), International Clinical Trials Registry Platform (ICTRP), and clinicaltrials.gov. Following screening of the identified articles, 26 were selected as relevant. We found that measurement of S100B can help informed decision making in the emergency department, possibly reducing resource use; however, there is insufficient evidence that any of the other markers is ready for clinical application. Our work pointed out serious problems in the design, analysis, and reporting of many of the studies, and identified substantial heterogeneity and research gaps. These findings emphasize the importance of methodologically rigorous studies focused on a biomarker's intended use, and defining standardized, validated, and reproducible approaches. The living nature of this systematic review, which will summarize key updated information as it becomes available, can inform and guide future implementation of biomarkers in the clinical arena.

Advances in Magnetic Nanoparticles for Biomedical Applications

Magnetic nanoparticles (NPs) are emerging as an important class of biomedical functional nanomaterials in areas such as hyperthermia, drug release, tissue engineering, theranostic, and lab-on-a-chip, due to their exclusive chemical and physical properties. Although some works can be found reviewing the main application of magnetic NPs in the area of biomedical engineering, recent and intense progress on magnetic nanoparticle research, from synthesis to surface functionalization strategies, demands for a work that includes, summarizes, and debates current directions and ongoing advancements in this research field. Thus, the present work addresses the structure, synthesis, properties, and the incorporation of magnetic NPs in nanocomposites, highlighting the most relevant effects of the synthesis on the magnetic and structural properties of the magnetic NPs and how these effects limit their utilization in the biomedical area. Furthermore, this review next focuses on the application of magnetic NPs on the biomedical field. Finally, a discussion of the main challenges and an outlook of the future developments in the use of magnetic NPs for advanced biomedical applications are critically provided.

Label-free electrochemical immunoassay for neuron specific enolase based on 3D macroporous reduced graphene oxide/polyaniline film

The content of neuron specific enolase (NSE) in serum is considered to be an essential indicator of small cell lung cancer (SCLC). Here, a novel label-free electrochemical immunoassay for the detection of NSE based on the three dimensionally macroporous reduced graphene oxide/polyaniline (3DM rGO/PANI) film has been proposed. The 3DM rGO/PANI film was constructed by electrochemical co-deposition of GO and aniline into the interspaces of a sacrificial silica opal template modified Au slice. During the co-deposition, GO was successfully reduced by aniline and PANI could be deposited on the surfaces of rGO sheets. The ratio of rGO and PANI in the composite was also optimized to achieve the maximum electrochemical performance. The 3DM rGO/PANI composite provided larger specific surface area for the antibody immobilization, exhibited enhanced conductivity for electron transfer, and more important was that PANI acted as the electroactive probe for indicating the NSE concentration. Under the optimal conditions, a linear current response of PANI to NSE concentration was obtained over 0.5 pg mL^-1-10.0 ng mL^-1 with a detection limit of 0.1 pg mL^-1. Moreover, the immunosensor showed excellent selectivity, good stability, satisfactory reproducibility and regeneration, and was employed to detect NSE in clinical serum specimens.

Immune-enrichment of insulin in bio-fluids on gold-nanoparticle decorated target plate and in situ detection by MALDI MS

BACKGROUND

Detection of low-abundance biomarkers using mass spectrometry (MS) is often hampered by non-target molecules in biological fluids. In addition, current procedures for sample preparation increase sample consumption and limit analysis throughput. Here, a simple strategy is proposed to construct an antibody-modified target plate for high-sensitivity MS detection of target markers such as insulin, in biological fluids.

METHODS

The target plate was first modified with gold nanoparticle, and then functionalized with corresponding antibody through chemical conjugation. Clinical specimens were incubated onto these antibody-functionalized target plates, and then subjected to matrix assisted laser desorption ionization mass spectrometry analysis.

RESULTS

Insulin in samples was enriched specifically on this functional plate. The detection just required low-volume samples (lower than 5 µL) and simplified handling process (within 40 min). This method exhibited high sensitivity (limit of detection in standard samples, 0.8 nM) and good linear correlation of MS intensity with insulin concentration (R² = 0.994). More importantly, insulin present in real biological fluids such as human serum and cell lysate could be detected directly by using this functional target plate without additional sample preparations.

CONCLUSIONS

Our method is easy to manipulate, cost-effective, and with a potential to be applied in the field of clinical biomarker detection.

The Frequency and Energy of Snoring Sounds Are Associated with Common Carotid Artery Intima-Media Thickness in Obstructive Sleep Apnea Patients

Obstructive sleep apnea (OSA) is a known risk factor for atherosclerosis. We investigated the association of common carotid artery intima-media thickness (CCA-IMT) with snoring sounds in OSA patients. A total of 30 newly diagnosed OSA patients with no history of cardiovascular diseases were prospectively enrolled for measuring mean CCA-IMT with B-mode ultrasonography, body mass index, metabolic syndrome, 10-year cardiovascular disease risk score, high-sensitivity C-reactive protein, and homocysteine. Good-quality signals of full-night snoring sounds in an ordinary sleep condition obtained from 15 participants were further acoustically analyzed (Included group). All variables of interest were not significantly different (all p > 0.05) between the included and non-included groups except for diastolic blood pressure (p = 0.037). In the included group, CCA-IMT was significantly correlated with snoring sound energies of 0–20 Hz (r = 0.608, p = 0.036) and 652–1500 Hz (r = 0.632, p = 0.027) and was not significantly associated with that of 20–652 Hz (r = 0.366, p = 0.242) after adjustment for age and sex. Our findings suggest that underlying snoring sounds may cause carotid wall thickening and support the large-scale evaluation of snoring sound characters as markers of surveillance and for risk stratification at diagnosis.

Portable Enzyme-Paper Biosensors Based on Redox-Active CeO2 Nanoparticles

Portable, nanoparticle (NP)-enhanced enzyme sensors have emerged as powerful devices for qualitative and quantitative analysis of a variety of analytes for biomedicine, environmental applications, and pharmaceutical fields. This chapter describes a method for the fabrication of a portable, paper-based, inexpensive, robust enzyme biosensor for the detection of substrates of oxidase enzymes. The method utilizes redox-active NPs of cerium oxide (CeO2) as a sensing platform which produces color in response to H2O2 generated by the action of oxidase enzymes on their corresponding substrates. This avoids the use of peroxidases which are routinely used in conjunction with glucose oxidase. The CeO2 particles serve dual roles, as high surface area supports to anchor high loadings of the enzyme as well as a color generation reagent, and the particles are recycled multiple times for the reuse of the biosensor. These sensors are small, light, disposable, inexpensive, and they can be mass produced by standard, low-cost printing methods. All reagents needed for the analysis are embedded within the paper matrix, and sensors stored over extended periods of time without performance loss. This novel sensor is a general platform for the in-field detection of analytes that are substrates for oxidase enzymes in clinical, food, and environmental samples.

Functional nanostructures for enzyme based biosensors: properties, fabrication and applications

A review describing functional nanostructures for portable and printable enzyme biosensors. Specific physicochemical and surface properties of nanoparticles used as carriers and sensing components and their assembly are discussed with an overview of current and emerging techniques enabling large scale roll-to-roll fabrication and miniaturization. Their integration in flexible, wearable and inexpensive point-of-use devices, and implementation challenges are also provided with examples of applications.

Quaternized magnetic nanoparticles-fluorescent polymer system for detection and identification of bacteria

Nanomaterial-based 'chemical nose' sensor with sufficient sensing specificity is a useful analytical tool for the detection of toxicologically important substances in complicated biological systems. A sensor array containing three quaternized magnetic nanoparticles (q-MNPs)-fluorescent polymer systems has been designed to identify and quantify bacteria. The bacterial cell membranes disrupt the q-MNP-fluorescent polymer, generating unique fluorescence response array. The response intensity of the array is dependent on the level of displacement determined by the relative q-MNP-fluorescent polymer binding strength and bacteria cells-MNP interaction. These characteristic responses show a highly repeatable bacteria cells and can be differentiated by linear discriminant analysis (LDA). Based on the array response matrix from LDA, our approach has been used to measure bacteria with an accuracy of 87.5% for 10(7) cfu mL(-1) within 20 min. Combined with UV-vis measurement, the method can be successfully performed to identify and detect eight different pathogen samples with an accuracy of 96.8%. The measurement system has a potential for further applications and provides a facile and simple method for the rapid analysis of protein, DNA, and pathogens.

Trapping-assisted sensing of particles and proteins using on-chip optical microcavities

An improved ability to sense particles and biological molecules is crucial for continued progress in applications ranging from medical diagnostics to environmental monitoring to basic research. Impressive electronic and photonic devices have been developed to this end. However, several drawbacks exist. The sensing of molecules is almost exclusively performed via their binding to a functionalized device surface. This means that the devices are seldom reusable, that their functionalization needs to be decided before use, and that they face the diffusion bottleneck. The latter challenge also applies to particle detection using photonic devices. Here, we demonstrate particle sensing using optical forces to trap and align them on waveguide-coupled silicon microcavities. A second probe laser detects the trapped particles by measuring the microcavity resonance shift. We also apply this platform to quantitatively sense green fluorescent proteins by detecting the size distribution of clusters of antibody-coated particles bound by the proteins.

High-sensitivity nanosensors for biomarker detection

High sensitivity nanosensors utilize optical, mechanical, electrical, and magnetic relaxation properties to push detection limits of biomarkers below previously possible concentrations. The unique properties of nanomaterials and nanotechnology are exploited to design biomarker diagnostics. High-sensitivity recognition is achieved by signal and target amplification along with thorough pre-processing of samples. In this tutorial review, we introduce the type of detection signals read by nanosensors to detect extremely small concentrations of biomarkers and provide distinctive examples of high-sensitivity sensors. The use of such high-sensitivity nanosensors can offer earlier detection of disease than currently available to patients and create significant improvements in clinical outcomes.

Detection of target ssDNA using a microfabricated Hall magnetometer with correlated optical readout

Sensing biological agents at the genomic level, while enhancing the response time for biodetection over commonly used, optics-based techniques such as nucleic acid microarrays or enzyme-linked immunosorbent assays (ELISAs), is an important criterion for new biosensors. Here, we describe the successful detection of a 35-base, single-strand nucleic acid target by Hall-based magnetic transduction as a mimic for pathogenic DNA target detection. The detection platform has low background, large signal amplification following target binding and can discriminate a single, 350 nm superparamagnetic bead labeled with DNA. Detection of the target sequence was demonstrated at 364 pM (<2 target DNA strands per bead) target DNA in the presence of 36 μM nontarget (noncomplementary) DNA (<10 ppm target DNA) using optical microscopy detection on a GaAs Hall mimic. The use of Hall magnetometers as magnetic transduction biosensors holds promise for multiplexing applications that can greatly improve point-of-care (POC) diagnostics and subsequent medical care.

Tau elevations in the brain extracellular space correlate with reduced amyloid-β levels and predict adverse clinical outcomes after severe traumatic brain injury

Axonal injury is believed to be a major determinant of adverse outcomes following traumatic brain injury. However, it has been difficult to assess acutely the severity of axonal injury in human traumatic brain injury patients. We hypothesized that microdialysis-based measurements of the brain extracellular fluid levels of tau and neurofilament light chain, two low molecular weight axonal proteins, could be helpful in this regard. To test this hypothesis, 100 kDa cut-off microdialysis catheters were placed in 16 patients with severe traumatic brain injury at two neurological/neurosurgical intensive care units. Tau levels in the microdialysis samples were highest early and fell over time in all patients. Initial tau levels were >3-fold higher in patients with microdialysis catheters placed in pericontusional regions than in patients in whom catheters were placed in normal-appearing right frontal lobe tissue (P = 0.005). Tau levels and neurofilament light-chain levels were positively correlated (r = 0.6, P = 0.013). Neurofilament light-chain levels were also higher in patients with pericontusional catheters (P = 0.04). Interestingly, initial tau levels were inversely correlated with initial amyloid-β levels measured in the same samples (r = -0.87, P = 0.000023). This could be due to reduced synaptic activity in areas with substantial axonal injury, as amyloid-β release is closely coupled with synaptic activity. Importantly, high initial tau levels correlated with worse clinical outcomes, as assessed using the Glasgow Outcome Scale 6 months after injury (r = -0.6, P = 0.018). Taken together, our data add support for the hypothesis that axonal injury may be related to long-term impairments following traumatic brain injury. Microdialysis-based measurement of tau levels in the brain extracellular space may be a useful way to assess the severity of axonal injury acutely in the intensive care unit. Further studies with larger numbers of patients will be required to assess the reproducibility of these findings and to determine whether this approach provides added value when combined with clinical and radiological information.

Real-time detection of β1 integrin expression on MG-63 cells using electrochemical impedance spectroscopy

Beta 1 integrin is a membrane protein responsible for attachment and migration of osteosarcoma cells. In this study, expression of β1 integrin on MG-63 cells, a human osteogenic sarcoma cell line, was monitored using electrochemical impedance spectroscopy (EIS). ITO-based biochips were developed using a semiconductor technique. Differences in electric resistance (ΔR) were measured continuously when cells binding with anti-β1 integrin antibody coagulated with nano-scale gold particles. The results of the EIS system were compared with traditional immunofluorescence staining. We found that sample chambers with higher cell densities had larger ΔR values. When the cell densities increased from 5 × 10(4) cells/ml to 5 × 10(5) cells/ml, the ΔR value dose-dependently increased from 14 Ω to 37 Ω. In addition, a highly linear relationship (correlation coefficient, 0.921) was found between the ΔR values and the corresponding fluorescence intensities (p<0.05). These results suggest that electrochemical impedance spectroscopy can be a useful tool for evaluating β1 integrin expression on cell membranes.

Biosensors in clinical chemistry - 2011 update

Research activity and applications of biosensors for measurement of analytes of clinical interest over the last eight years are reviewed. Nanotechnology has been applied to improve performance of biosensors using electrochemical, optical, mechanical and physical modes of transduction, and to allow arrays of biosensors to be constructed for parallel sensing. Biosensors have been proposed for measurement of cancer biomarkers, cardiac biomarkers as well as biomarkers for autoimmune disease, infectious disease and for DNA analysis. Novel applications of biosensors include measurements in alternate sample types, such as saliva. Biosensors based on immobilized whole cells have found new applications, for example to detect the presence of cancer and to monitor the response of cancer cells to chemotherapeutic agents. The number of research reports describing new biosensors for analytes of clinical interest continues to increase; however, movement of biosensors from the research laboratory to the clinical laboratory has been slow. The greatest impact of biosensors will be felt at point-of-care testing locations without laboratory support. Integration of biosensors into reliable, easy-to-use and rugged instrumentation will be required to assure success of biosensor-based systems at the point-of-care.

Multilayer polymer microchip capillary array electrophoresis devices with integrated on-chip labeling for high-throughput protein analysis

It is desirable to have inexpensive, high-throughput systems that integrate multiple sample analysis processes and procedures, for applications in biology, chemical analysis, drug discovery, and disease screening. In this paper, we demonstrate multilayer polymer microfluidic devices with integrated on-chip labeling and parallel electrophoretic separation of up to eight samples. Microchannels were distributed in two different layers and connected through interlayer through-holes in the middle layer. A single set of electrophoresis reservoirs and one fluorescent label reservoir address parallel analysis units for up to eight samples. Individual proteins and a mixture of cancer biomarkers have been successfully labeled on-chip and separated in parallel with this system. A detection limit of 600 ng/mL was obtained for heat shock protein 90. Our integrated on-chip labeling microdevices show great potential for low-cost, simplified, rapid, and high-throughput analysis.

Microfluidics in macro-biomolecules analysis: macro inside in a nano world

Use of microfluidic devices in the life sciences and medicine has created the possibility of performing investigations at the molecular level. Moreover, microfluidic devices are also part of the technological framework that has enabled a new type of scientific information to be revealed, i.e. that based on intensive screening of complete sets of gene and protein sequences. A deeper bioanalytical perspective may provide quantitative and qualitative tools, enabling study of various diseases and, eventually, may offer support for the development of accurate and reliable methods for clinical assessment. This would open the way to molecule-based diagnostics, i.e. establish accurate diagnosis and disease prognosis based on identification and/or quantification of biomacromolecules, for example proteins or nucleic acids. Finally, the development of disposable and portable devices for molecule-based diagnosis would provide the perfect translation of the science behind life-science research into practical applications dedicated to patients and health practitioners. This review provides an analytical perspective of the impact of microfluidics on the detection and characterization of bio-macromolecules involved in pathological processes. The main features of molecule-based diagnostics and the specific requirements for the diagnostic devices are discussed. Further, the techniques currently used for testing bio-macromolecules for potential diagnostic purposes are identified, emphasizing the newest developments. Subsequently, the challenges of this type of application and the status of commercially available devices are highlighted, and future trends are noted.

Functionalized SiO2 labeled CA19-9 antibodies: a new strategy for signal amplification of antigen-antibody sensing processes

A new strategy was described for amplifying the response of the antigen-antibody sensing processes by functionalizing SiO(2) nanoparticles labeled secondary antibodies based on a sandwich immunoassay in this work. At first, the multi-walled carbon nanotubes (CNTs) were individually dispersed in the aqueous bovine serum albumin (BSA) to obtain BSA molecules coated CNTs (BSA-CNTs). Then the gold colloids (nano-Au) were absorbed on the BSA-CNTs surface by the amido and disulfide groups of BSA. Later, a functionalized gold/carbon nanotube composite nanohybrid (DpAu/nano-Au/BSA-CNTs) modified electrode was developed by electrochemical deposition of Au(3+) onto nano-Au/BSA-MWNTs surface. Thus, a sensitive immunosensor for carbohydrate antigen 19-9 (CA19-9) has been constructed by further employment of Nafion coated SiO(2) nanoparticles labeled secondary antibody (SiO(2)-Ab(2)) for the signal amplification. More importantly, the loading of SiO(2)-Ab(2) can not only cause the construction of the dielectric antigen-antibody immunocomplex layer but also introduce the insulated Nafion coated SiO(2) nanoparticles which demonstrate the relatively high resistance, resulting in a strong detection signal. The proposed sensing strategy provides a wide linear dynamic range from 0.15 to 150 U mL(-1) with a low detection limit of 0.06 U mL(-1) at 3 times the background noise. Moreover, the extremely high stability of the functionalized gold/carbon nanotube composite nanohybrid monolayer allows the designed biosensing interface to obtain a good stability and long-term life.