Flexible nanopillar-based immunoelectrochemical biosensor for noninvasive detection of Amyloid beta

The noninvasive early detection of biomarkers for Alzheimer's disease (AD) is essential for the development of specific treatment strategies. This paper proposes an advanced method for fabricating highly ordered and flexible nanopillar-based electrochemical biosensors by the combination of soft/photolithography and metal evaporation. The nanopillar array (NPA) exhibits high surface area containing 1500 nm height and 500 nm diameter with 3:1 ratio. In regard with physical properties of polyurethane (PU) substrate, the developed NPA is sustainable and durable to external pressure such as bending and twisting. To manipulate the NPA surface to biocompatible, the gold was uniformly deposited on the PU substrate. The thiol chemistry which is stably modified on the gold surface as a form of self-assembled monolayer was employed for fabricating the NPA as a biocompatible chip by covalently immobilize the antibodies. The proposed nanopillar-based immunoelectrochemical biosensor exhibited good and stable electrochemical performance in β-amyloid (Aβ) detection. Moreover, we successfully confirmed the performance of the as-developed sensor using the artificial injection of Aβ in human tear, with sensitivity of 0.14 ng/mL and high reproducibility (as a standard deviation below 10%). Our findings show that the developed nanopillar-based sensor exhibits reliable electrochemical characteristics and prove its potential for application as a biosensor platform for testing at the point of care.

Antibacterial Nanopillar Array for an Implantable Intraocular Lens

Postsurgical intraocular lens (IOL) infection caused by pathogenic bacteria can result in blindness and often requires a secondary operation to replace the contaminated lens. The incorporation of an antibacterial property onto the IOL surface can prevent bacterial infection and postoperative endophthalmitis. This study describes a polymeric nanopillar array (NPA) integrated onto an IOL, which captures and eradicates the bacteria by rupturing the bacterial membrane. This is accomplished by changing the behavior of the elastic nanopillars using bending, restoration, and antibacterial surface modification. The combination of the polymer coating and NPA dimensions can decrease the adhesivity of corneal endothelial cells and posterior capsule opacification without causing cytotoxicity. An ionic antibacterial polymer layer is introduced onto an NPA using an initiated chemical vapor deposition process. This improves bacterial membrane rupture efficiency by increasing the interactions between the bacteria and nanopillars and damages the bacterial membrane using quaternary ammonium compounds. The newly developed ionic polymer-coated NPA exceeds 99% antibacterial efficiency against Staphylococcus aureus, which is achieved through topological and physicochemical surface modification. Thus, this paper provides a novel, efficient strategy to prevent postoperative complications related to bacteria contamination of IOL after cataract surgery.

An electrophoretic DNA extraction device using a nanofilter for molecular diagnosis of pathogens

Rapid and efficient nucleic acid (NA) extraction and concentration are required for point-of-care analysis in order to prevent an epidemic/pandemic disease outbreak. Typical silica-based NA extraction methods have limitations such as being time-consuming, requiring human intervention, and resulting in a low recovery yield. In this study, we have developed a pathogenic DNA extraction device based on electrokinetic separation incorporated with a silicon nitride (SiNx) nanofilter, which expedites the DNA extraction procedure with advantages of being convenient, efficient, and inexpensive. This DNA extraction device consists of a computer numerical control (CNC) milled-Teflon gadget with a cis-chamber as a cell lysate reservoir and a trans-chamber as a elution solution reservoir, with the SiNx nanofilter being inserted between the two chambers. The SiNx nanofilter was fabricated using a photolithographic method in conjunction with nanoimprinting. Approximately 7.2 million nanopores of 220 nm diameter were located at the center of the nanofilter. When a DC electric field is applied through the nanopores, DNA is transferred from the cis-chamber to the trans-chamber to isolate the DNA from the cell debris. To demonstrate the DNA extraction performance, we measured the absorbances at 260 and 280 nm and performed a real-time polymerase chain reaction (real-time PCR) using the recovered DNA to verify its feasibility for downstream genetic analysis. Moreover, the DNA extraction device was successfully operated using a 1.5 V alkaline battery, which verifies the portability of the device for point-of-care testing. Such an advanced DNA extraction system can be utilized in various fields including clinical analysis, pathogen detection, forensic analysis, and on-site detection.

Extremely Fast Self-Healable Bio-Based Supramolecular Polymer for Wearable Real-Time Sweat-Monitoring Sensor

Sensors with autonomous self-healing properties offer enhanced durability, reliability, and stability. Although numerous self-healing polymers have been attempted, achieving sensors with fast and reversible recovery under ambient conditions with high mechanical toughness remains challenging. Here, a highly sensitive wearable sensor made of a robust bio-based supramolecular polymer that is capable of self-healing via hydrogen bonding is presented. The integration of carbon fiber thread into a self-healing polymer matrix provides a new toolset that can easily be knitted into textile items to fabricate wearable sensors that show impressive self-healing efficiency (>97.0%) after 30 s at room temperature for K⁺/Na⁺ sensing. The wearable sweat-sensor system-coupled with a wireless electronic circuit board capable of transferring data to a smart phone-successfully monitors electrolyte ions in human perspiration noninvasively in real time, even in the healed state during indoor exercise. Our smart sensors represent an important advance toward futuristic personalized healthcare applications.

Highly self-healable and flexible cable-type pH sensors for real-time monitoring of human fluids

Development of sensing technology with wearable chemical sensors is realizing non-invasive, real-time monitoring healthcare and disease diagnostics. The advanced sensor devices should be compact and portable for use in limited space, easy to wear on human body, and low-cost for personalized healthcare markets. Here, we report a highly sensitive, flexible, and autonomously self-healable pH sensor cable developed by weaving together two carbon fiber thread electrodes coated with mechanically robust self-healing polymers. The pH sensor cable showed excellent electrochemical performances of sensitivity, repeatability, and durability. Spontaneous and autonomous sensor healing efficiency of the pH sensor cable was demonstrated by measuring sensitivity during four cycles of cutting and healing process. The pH sensor cable could measure pH in small volumes of real human fluid samples, including urine, saliva, and sweat, and the results were similar to those of a commercial pH meter. Taken together, successful real-time pH monitoring for human sweat was demonstrated by fabricating a wearable sensing system in which the pH sensor cable was knitted into a headband integrated with wireless electronics.

Smartphone operable centrifugal system (SOCS) for on-site DNA extraction from foodborne bacterial pathogen

The on-site recovery of nucleic acid from foodborne bacteria is in high demand to further understand on-site molecular diagnosis, which is especially applicable in developing countries. Here, we first proposed a smartphone operable centrifugal system (SOCS) for nucleic acid extraction with the assistance of a low power consumable motor and hydrogel beads. The SOCS consists of a centrifugal motor, 3D-printed cartridge, a nucleic acid collection column, and a smartphone. The SOCS shows excellent DNA extraction performance within 6 min, and it can operate more than 100 times using a smartphone. The purified effluent DNA was accumulated in the nucleic acid collection column. The performance of the SOCS was confirmed by amplifying the recovered DNA from Escherichia coli O157:H7. Moreover, the artificially inoculated food and blood samples also confirmed the performance of SOCS. The proposed SOCS provides an on-site operable nucleic acid separation platform in terms of simplicity, easy usability, cost-effectiveness, and portability in pathogenic point-of-care diagnostics.

Potentiometric performance of flexible pH sensor based on polyaniline nanofiber arrays

We report potentiometric performance of a polyaniline nanofiber array-based pH sensor fabricated by combining a dilute chemical polymerization and low-cost and simple screen printing process. The pH sensor had a two-electrode configuration consisting of polyaniline nanofiber array sensing electrode and Ag/AgCl reference electrode. Measurement of electromotive force between sensing and reference electrodes provided various electrochemical properties of pH sensors. The pH sensor show excellent sensor performances of sensitivity of 62.4 mV/pH, repeatability of 97.9% retention, response time of 12.8 s, and durability of 3.0 mV/h. The pH sensor could also measure pH changes as the milk is spoiled, which is similar to those of a commercial pH meter. The pH sensors were highly flexible, and thus can measure the fruit decay on the curved surface of an apple. This flexible and miniature pH sensor opens new opportunities for monitoring of water, product process, human health, and chemical (or bio) reactions even using small volumes of samples.

A Disposable and Multi-Chamber Film-Based PCR Chip for Detection of Foodborne Pathogen

Since the increment of the threat to public health caused by foodborne pathogens, researches have been widely studied on developing the miniaturized detection system for the on-site pathogen detection. In the study, we focused on the development of portable, robust, and disposable film-based polymerase chain reaction (PCR) chip containing a multiplex chamber for simultaneous gene amplification. In order to simply fabricate and operate a film-based PCR chip, different kinds of PCR chambers were designed and fabricated using polyethylene terephthalate (PET) and polyvinyl chloride (PVC) adhesive film, in comparison with commercial PCR, which employs a stereotyped system at a bench-top scale. No reagent leakage was confirmed during the PCR thermal cycling using the film PCR chip, which indicates that the film PCR chip is structurally stable for rapid heat cycling for DNA amplification. Owing to use of the thin film to fabricate the PCR chip, we are able to realize fast thermal transfer from the heat block that leads to short PCR amplification time. Moreover, using the film PCR chip, we could even amplify the target pathogen with 10 CFU mL⁻¹. The artificially infected milk with various concentration of Bacillus cereus was successfully amplified on a single film PCR chip. On the basis of the reliable results, the developed film PCR chip could be a useful tool as a POCT device to detect foodborne pathogens via genetic analysis.

Flexible nanopillar-based electrochemical sensors for genetic detection of foodborne pathogens

Flexible and highly ordered nanopillar arrayed electrodes have brought great interest for many electrochemical applications, especially to the biosensors, because of its unique mechanical and topological properties. Herein, we report an advanced method to fabricate highly ordered nanopillar electrodes produced by soft-/photo-lithography and metal evaporation. The highly ordered nanopillar array exhibited the superior electrochemical and mechanical properties in regard with the wide space to response with electrolytes, enabling the sensitive analysis. As-prepared gold and silver electrodes on nanopillar arrays exhibit great and stable electrochemical performance to detect the amplified gene from foodborne pathogen of Escherichia coli O157:H7. Additionally, lightweight, flexible, and USB-connectable nanopillar-based electrochemical sensor platform improves the connectivity, portability, and sensitivity. Moreover, we successfully confirm the performance of genetic analysis using real food, specially designed intercalator, and amplified gene from foodborne pathogens with high reproducibility (6% standard deviation) and sensitivity (10 × 1.01 CFU) within 25 s based on the square wave voltammetry principle. This study confirmed excellent mechanical and chemical characteristics of nanopillar electrodes have a great and considerable electrochemical activity to apply as genetic biosensor platform in the fields of point-of-care testing (POCT).

Surface-Modified Mesh Filter for Direct Nucleic Acid Extraction and its Application to Gene Expression Analysis

Rapid and convenient isolation of nucleic acids (NAs) from cell lysate plays a key role for onsite gene expression analysis. Here, this study achieves one-step and efficient capture of NA directly from cell lysate by developing a cationic surface-modified mesh filter (SMF). By depositing cationic polymer via vapor-phase deposition process, strong charge interaction is introduced on the surface of the SMF to capture the negatively charged NAs. The NA capturing capability of SMF is confirmed by X-ray photoelectron spectroscopy, fluorescent microscopy, and zeta potential measurement. In addition, the genomic DNAs of Escherichia Coli O157:H7 can be extracted by the SMF from artificially infected food, and fluorescent signal is observed on the surface of SMF after amplification of target gene. The proposed SMF is able to provide a more simplified, convenient, and fast extraction method and can be applied to the fields of food safety testing, clinical diagnosis, or environmental pollutant monitoring.

Development of bufferless gel electrophoresis chip for easy preparation and rapid DNA separation

This work presents a handy, fast, and compact bufferless gel electrophoresis chip (BGEC), which consists of precast agarose gel confined in a disposable plastic body with electrodes. It does not require large volumes of buffer to fill reservoirs, or the process of immersing the gel in the buffer. It withstands voltages up to 28.4 V/cm, thereby allowing DNA separation within 10 min with a similar separation capability to the standard gel electrophoresis. The results suggest that our BGEC is highly suitable for in situ gel electrophoresis in forensic, epidemiological settings and crime scenes where standard gel electrophoresis equipment cannot be brought in while quick results are needed.

Frank's sign - A dermatological link to coronary artery disease?

Frank's sign, also known as diagonal earlobe crease (DELC), was observed to be an aural sign of coronary artery disease (CAD). Since then, there has been much interest in examining this unique and controversial association. This report describes a patient who has bilateral complete and deep diagonal ear lobe creases, presented with angina and diagnosed to have coronary artery disease on angiography. The characteristics of the sign and its association with atherosclerotic disease were discussed.

Nanopillar films with polyoxometalate-doped polyaniline for electrochemical detection of hydrogen peroxide

Design and fabrication of electrodes is key in the development of electrochemical sensors with superior electrochemical performances. Herein, an enzymeless electrochemical sensor is developed for detection of hydrogen peroxide based on the use of highly ordered polyoxometalate (POM)-doped polyaniline (PANI) nanopillar films. The electrodeposition technique enables the entrapment of POMs into PANI during electropolymerization to produce thin coatings of POM-PANI. Electrochemical investigations of the POM-PANI/nanopillar electrode showed well-defined multiple pairs of redox peaks and rapid electron transfer. The nanopillar structure facilitated the diffusion of the electrolyte and thus, enhanced the redox reaction. In particular, the POM-PANI/nanopillar electrode was incorporated into a flow injection biosensor and it demonstrates its electrocatalytic activity to detect hydrogen peroxide with high sensitivity, rapid response time, and low detection limit.

Flexible and Disposable Sensing Platforms Based on Newspaper

The flexible sensing platform is a key component for the development of smart portable devices targeting healthcare, environmental monitoring, point-of-care diagnostics, and personal electronics. Herein, we demonstrate a simple, scalable, and cost-effective strategy for fabrication of a sensing electrode based on a waste newspaper with conformal coating of parylene C (P-paper). Thin polymeric layers over cellulose fibers allow the P-paper to possess improved mechanical and chemical stability, which results in high-performance flexible sensing platforms for the detection of pathogenic E. coli O157:H7 based on DNA hybridization. Moreover, P-paper electrodes have the potential to serve as disposable, flexible sensing platforms for point-of-care testing biosensors.

High performance flexible pH sensor based on polyaniline nanopillar array electrode

Flexible pH sensor technologies have attracted a great deal of attention in many applications, such as, wearable health care devices and monitors for chemical and biological processes. Here, we fabricated flexible and thin pH sensors using a two electrode configuration comprised of a polyaniline nanopillar (PAN) array working electrode and an Ag/AgCl reference electrode. In order to provide nanostructure, soft lithography using a polymeric blend was employed to create a flexible nanopillar backbone film. Polyaniline-sensing materials were deposited on a patterned-nanopillar array by electrochemical deposition. The pH sensors produced exhibited a near-Nernstian response (∼60.3mV/pH), which was maintained in a bent state. In addition, pH sensors showed other excellent sensor performances in terms of response time, reversibility, repeatability, selectivity, and stability.

Plastic-Chip-Based Magnetophoretic Immunoassay for Point-of-Care Diagnosis of Tuberculosis

Tuberculosis (TB) remains a relevant infectious disease in the 21st century, and its extermination is still far from being attained. Due to the extreme infectivity of incipient TB patients, a rapid sensing system for proficient point-of-care (POC) diagnostics is required. In our study, a plastic-chip-based magnetophoretic immunoassay (pcMPI) is introduced using magnetic and gold nanoparticles (NPs) modified with Mycobacterium tuberculosis (MTB) antibodies. This pcMPI offers an ultrasensitive limit of detection (LOD) of 1.8 pg·ml(-1) for the detection of CFP-10, an MTB-secreted antigen, as a potential TB biomarker with high specificity. In addition, by combining the plastic chip with an automated spectrophotometer setup, advantages include ease of operation, rapid time to results (1 h), and cost-effectiveness. Furthermore, the pcMPI results using clinical sputum culture filtrate samples are competitively compared with and integrated with clinical data collected from conventional tools such as the acid-fast bacilli (AFB) test, mycobacteria growth indicator tube (MGIT), polymerase chain reaction (PCR), and physiological results. CFP-10 concentrations were consistently higher in patients diagnosed with MTB infection than those seen in patients infected with nontuberculosis mycobacteria (NTM) (P < 0.05), and this novel test can distinguish MTB and NTM while MGIT cannot. All these results indicate that this pcMPI has the potential to become a new commercial TB diagnostic POC platform in view of its sensitivity, portability, and affordability.

Fabrication of Flexible, Redoxable, and Conductive Nanopillar Arrays with Enhanced Electrochemical Performance

Highly ordered and flexible nanopillar arrays have received considerable interest for many applications of electrochemical devices because of their unique mechanical and structural properties. Here, we report on highly ordered polyoxometalate (POM)-doped polypyrrole (Ppy) nanopillar arrays produced by soft lithography and subsequent electrodeposition. As-prepared POM-Ppy/nanopillar films show superior electrochemical performances for pseudocapacitor and enzymeless electrochemical sensor applications and good mechanical properties, which allowed them to be easily bent and twisted. Regarding electrochemical characteristics for pseudocapacitive electrodes, the POM-Ppy/nanopillar electrodes are capable of delivering high areal capacitance of 77.0 mF cm(-2), high rate performance, and good cycle life of ∼100% retention over 3500 cycles even when bent. Moreover, the study suggests that the POM-Ppy/nanopillar electrodes have an excellent electrocatalytic activity toward hydrogen.

Protein-directed assembly of cobalt phosphate hybrid nanoflowers

The understanding and controlling of biomimetic hybrid materials are a key objective in bio-nanotechnology, materials chemistry, and colloid science fields. Biomaterials, such as, enzyme, DNA, RNA, and proteins have become important templates for the construction of inorganic-organic hybrid nanoflowers. From this perspective, we present a simple approach to synthesize protein and metal hybrid flower-like structure using bovine serum albumin (BSA) and cobalt phosphate, and the results of our study on the formation mechanism involved. The time dependent growing stage and formation mechanism were analyzed by electron microscopes and spectroscopic techniques. The protein-directed assembly method for preparation of hybrid nanoflowers described in this work could be used to fabricate other bio-metal hybrid materials with possible applications in biosensors, bioanalytical devices, and industrial biocatalyst fields.

Contribution of actin filaments and microtubules to cell elongation and alignment depends on the grating depth of microgratings

Background

It has been reported that both chemical and physical surface patterns influence cellular behaviors, such as cell alignment and elongation. However, it still remains unclear how actin filament and microtubules (MTs) differentially respond to these patterns.

Results

We examined the effects of chemical and physical patterns on cell elongation and alignment by observing actin filament and MTs of retinal pigment epithelium-1(RPE-1) cells, which were cultured on either fibronectin (FN)-line pattern (line width and spacing: 1 μm) or FN-coated 1 μm gratings with two different depths (0.35 or 1 μm). On the surface with either FN-line pattern or micrograting structure, the cell aspect ratios were at least two times higher than those on the surface with no pattern. Cell elongation on the gratings depended on the depth of the gratings. Cell elongation and alignment on both FN-line pattern and 1 μm gratings with 0.35 μm depth were perturbed either by inhibition of actin polymerization or MT depletion, while cell elongation and alignment on 1 μm gratings with 1 μm depth were perturbed only by MT depletion.

Conclusions

Our results suggest that the contribution of actin filaments and MTs to the elongation and alignment of epithelial cells on microgratings depends on the groove depth of these gratings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-016-0187-8) contains supplementary material, which is available to authorized users.