A point-of-care electrochemical biosensor for the rapid and sensitive detection of biomarkers in murine models with LPS-induced sepsis.

Sepsis is a life-threatening condition, which is irreversible if diagnosis and intervention are delayed. The response of the immune cells towards an infection triggers widespread inflammation through the production of cytokines, which may result in multiple organ dysfunction and eventual death. Conventional detection techniques fail to provide a rapid diagnosis because of their limited sensitivity and tedious protocol. This study proposes a point-of-care (POC) electrochemical biosensor that overcomes the limitations of current biosensing technologies in the clinical setting by its integration with electrokinetics, enhancing the sensitivity to picogram level compared with the nanogram limit of current diagnostic technologies. This biosensor promotes the use of a microelectrode strip to address the limitations of conventional photolithographic fabrication methods. Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and microRNA-155 (miR-155) were monitored in a lipopolysaccharide (LPS)-induced septic mouse model. The optimum target hybridization time in a high conductivity medium was observed to be 60 s leading to the completion of the whole operation within 5 min compared with the 4-h detection time of the traditional enzyme-linked immunosorbent assay (ELISA). The limit of detection (LOD) was calculated to be 0.84, 0.18, and 0.0014 pg mL-1, respectively. This novel sensor may have potential for the early diagnosis of sepsis in the clinical setting.

Voltage-modulated surface plasmon resonance biosensors integrated with gold nanohole arrays.

Surface plasmon resonance (SPR) has emerged as one of the most efficient and attractive techniques for optical sensors in biological applications. The traditional approach of an EC (electrochemical)-SPR biosensor to generate SPR is by adopting a prism underneath the sensing substrate, and an angular scan is performed to characterize the reflectivity of target analytes. In this paper, we designed and investigated a novel optical biosensor based on a hybrid plasmonic and electrochemical phenomenon. The SPR was generated from a thin layer of gold nanohole array on a glass substrate. Using C-Reactive Protein (CRP) as the target analyte, we tested our device for different concentrations and observed the optical response under various voltage bias conditions. We observed that SPR response is concentration-dependent and can be modulated by varying DC voltages or AC bias frequencies. For CRP concentrations ranging from 1 to 1000 µg/mL, at the applied voltage of -600 mV, we obtained a limit of detection for this device of 16.5 ng/mL at the resonance peak wavelength of 690 nm. The phenomenon is due to spatial re-distribution of electron concentration at the metal-solution interface. The results suggest that CRP concentration can be determined from the SPR peak wavelength shift by scanning the voltages. The proposed new sensor structure is permissible for various future optoelectronic integration for plasmonic and electrochemical sensing.

An AC electrokinetics-based electrochemical aptasensor for the rapid detection of microRNA-155.

Traditional immunosensors are often limited by low sensitivity and long detection times, for they usually depend on passive diffusion-dominated transport of target analytes for the binding reaction with a bio-recognition element such as enzymes, antibodies, and aptamers. Numerous studies rely on electric field manipulation by using alternating current (AC) electrokinetics to enhance the hybridization rate and reduce the hybridization time for faster and more efficient detection. This study demonstrated a rapid electrochemical aptasensor integrated with an AC electroosmotic (ACEO) flow phenomenon for the enhanced target hybridization of microRNA-155 (miR-155). Optimization of the electrokinetic conditions for target collection resulted in a saturation point after 75 s miR-155 was detected within the range of 1 aM-10 pM with a detection limit of 1 aM, which is 100 times lower and about 50 times faster compared with the conventional diffusion-dependent detection done for 1 h. The detection was also done in spiked serum samples, and a concentration range within the required detection range was obtained. The highly sensitive and specific results allow for the rapid and real-time sensing of target biomarkers, which can be used for the early detection of infection.

Simple In-House Fabrication of Microwells for Generating Uniform Hepatic Multicellular Cancer Aggregates and Discovering Novel Therapeutics.

Three-dimensional (3D) cell culture models have become powerful tools because they better simulate the in vivo pathophysiological microenvironment than traditional two-dimensional (2D) monolayer cultures. Tumor cells cultured in a 3D system as multicellular cancer aggregates (MCAs) recapitulate several critical in vivo characteristics that enable the study of biological functions and drug discovery. The microwell, in particular, has emerged as a revolutionary technology in the generation of MCAs as it provides geometrically defined microstructures for culturing size-controlled MCAs amenable for various downstream functional assays. This paper presents a simple and economical microwell fabrication methodology that can be conveniently incorporated into a conventional laboratory setting and used for the discovery of therapeutic interventions for liver cancer. The microwells were 400-700 µm in diameter, and hepatic MCAs (Huh-7 cells) were cultured in them for up to 5 days, over which time they grew to 250-520 µm with good viability and shape. The integrability of the microwell fabrication with a high-throughput workflow was demonstrated using a standard 96-well plate for proof-of-concept drug screening. The IC50 of doxorubicin was determined to be 9.3 µM under 2D conditions and 42.8 µM under 3D conditions. The application of photothermal treatment was demonstrated by optimizing concanavalin A-FITC conjugated silica-carbon hollow spheres (SCHSs) at a concentration of 500:200 µg/mL after a 2 h incubation to best bind with MCAs. Based on this concentration, which was appropriate for further photothermal treatment, the relative cell viability was assessed through exposure to a 3 W/cm2 near-infrared laser for 20 min. The relative fluorescence intensity showed an eight-fold reduction in cell viability, confirming the feasibility of using photothermal treatment as a potential therapeutic intervention. The proposed microwell integration is envisioned to serve as a simple in-house technique for the generation of MCAs useful for discovering therapeutic modalities for liver cancer treatment.

In situ study of EDC/NHS immobilization on gold surface based on attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS).

In this study, the time-dependent reaction between 11-mercaptoundecanoic acid (11-MUA) and 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide (EDC/NHS) is precisely characterized using surface enhanced infrared absorption spectroscopy (SEIRAS). According to the high correlation between the spectral results of SEIRAS and the electrochemical behavior, it strongly demonstrates that the EDC/NHS reaction would be obviously interfered by phosphate ions in the neutral pH condition (pH = 7.0).

Aptamer-based sensor for quantitative detection of mercury (II) ions by attenuated total reflection surface enhanced infrared absorption spectroscopy.

A sensing platform based on the attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) technique and immobilized aptamer has been proposed herein for the selective detection of mercury ions (Hg2+). In the proposed platform, 5' thiolated 32-mer DNA probes with methylene blue at the 3' end were immobilized on a thin gold (Au) surface layer. Following Hg2+ ions interacting with T bases of the aptamer, T-Hg-T bonds are formed; resulting in a hairpin-shaped formation of the DNA and a detectable change in the IR absorbance of the sensing interface. Notably, the background noise produced by external molecules (e.g., water, non-specific binding molecules and bulk solution) is reduced to a negligible level by means of the ATR detection mode. It is shown that the proposed sensor has a linear response (R2 = 0.986) with high sensitivity and good selectivity over the Hg2+ range of 0.01 µM-50 µM.

Chemo-photothermal effects of doxorubicin/silica-carbon hollow spheres on liver cancer.

Chemo-photothermal therapy, which exhibits synergistic effects, is more effective than either of the treatments administered alone because of its superior ability to target and destroy cancer cells. An anti-cancer compound (doxorubicin, DOX) was embedded in silica-carbon hollow spheres (SCHSs) using heat and vacuum to integrate multi-therapeutic effects onto one platform and subsequently improve the anti-cancer efficacy. SCHSs were synthesized via a surface activation method and its highly porous surface enhanced the loading content of the desired drug. SCHSs are an infrared photothermal material that can destroy targeted cells by heating under near-infrared (NIR) laser illumination at 808 nm. NIR laser illumination also enhances DOX release from SCHSs to increase the anti-cancer efficiency of DOX-loaded SCHSs (DOX-SCHSs) in both two-dimensional and three-dimensional multicellular tumor spheroid cultures. SCHSs exhibited high heat-generating ability and pH-responsive drug delivery. In conclusion, this study demonstrated that DOX-SCHSs represent a potential tool for chemo-photothermal therapy due to its photothermal effects. Thus, our findings imply that the high cancer cell killing efficiency of DOX-SCHSs induced by NIR illumination can be used for the treatment of tumors.

A bead-based immunofluorescence-assay on a microfluidic dielectrophoresis platform for rapid dengue virus detection.

The proof of concept of utilizing a microfluidic dielectrophoresis (DEP) chip was conducted to rapidly detect a dengue virus (DENV) in vitro based on the fluorescence immunosensing. The mechanism of detection was that the DEP force was employed to capture the modified beads (mouse anti-flavivirus monoclonal antibody-coated beads) in the microfluidic chip and the DENV modified with fluorescence label, as the detection target, can be then captured on the modified beads by immunoreaction. The fluorescent signal was then obtained through fluorescence microscopy, and then quantified by ImageJ freeware. The platform can accelerate an immuno-reaction time, in which the on-chip detection time was 5min, and demonstrating an ability for DENV detection as low as 104 PFU/mL. Furthermore, the required volume of DENV samples dramatically reduced, from the commonly used ~50µL to ~15µL, and the chip was reusable (>50x). Overall, this platform provides a rapid detection (5min) of the DENV with a low sample volume, compared to conventional methods. This proof of concept with regard to a microfluidic dielectrophoresis chip thus shows the potential of immunofluorescence based-assay applications to meet diagnostic needs.

Dielectrophoresis System for Testing Antimicrobial Susceptibility of Gram-Negative Bacteria to ß-Lactam Antibiotics.

Gram-negative bacteria (GNBs) are common pathogens causing severe sepsis. Rapid evaluation of drug susceptibility would guide effective antibiotic treatment and promote life-saving. A total of 78 clinical isolates of 13 Gram-negative species collected between April 2013 and November 2013 from two medical centers in Tainan were tested. Bacterial morphology changes in different concentrations of antibiotics were observed under the electric field of a quadruple electrode array using light microscopy. The minimal inhibitory concentrations (MICs) of four antimicrobial agents, namely, cefazolin, ceftazidime, cefepime, and doripenem, were determined by the dielectrophoretic antimicrobial susceptibility testing (dAST) and by the conventional broth dilution testing (BDT). The antibiotics at the concentration of 1× MIC induced obvious morphological changes in susceptible GNBs, including cell elongation, cell swelling, or lysis, at 90 min. In contrast, resistant strains remained unchanged. The MIC results measured by dAST were in good agreement with those of BDT (essential agreement 95.6%). The category agreement rate was 89.2%, and the very major errors rate for dAST was 2.9%. In conclusion, dAST could accurately determine drug susceptibility within 90 min. Comprehensive tests by dAST for more drugs against more GNB species are possible in the future.

Identification of Staphylococcus spp. and detection of mecA by an oligonucleotide array.

Phenotypic identification of coagulase-negative staphylococci (CoNS) is difficult and many staphylococcal species carry mecA. This study developed an array that was able to detect mecA and identify 30 staphylococcal species by targeting the internal transcribed spacer regions. A total of 129 target reference strains (30 species) and 434 clinical isolates of staphylococci were analyzed. Gene sequencing of 16S rRNA, gap or tuf genes was the reference method for species identification. All reference strains (100%) were correctly identified, while the identification rates of clinical isolates of S. aureus and CoNS were 98.9% and 98%, respectively. The sensitivity and specificity for mecA detection were 99% and 100%, respectively, in S. aureus isolates, and both values were 100% in isolates of CoNS. The assay takes 6 h from a purified culture isolate, and so far it has not been performed directly on patient samples.

Optimization of the score cutoff value for routine identification of Staphylococcus species by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry.

Staphylococcus species are important pathogens. We evaluated 2 score cutoffs (2.0 and 1.7) and the replicate number (a single or a duplicate test) on the identification of staphylococci using the Bruker matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). A collection of 440 clinical isolates (11 species) and 144 reference strains (36 species) was evaluated. For clinical isolates using a cutoff of 2.0 and duplicate tests, the rates of species, genus, and unreliable identifications were 93.4%, 5.7%, and 0.9% respectively, while the respective values were 99.3%, 0.2%, and 0.5% when the cutoff was 1.7. The species identification rates were significantly higher (P<0.01) when a cutoff of 1.7 or a duplicate test was used. Similar results were obtained for reference strains. In conclusion, a cutoff of 1.7 and duplicate tests are recommended for identification of staphylococci using MALDI-TOF MS.

Characterization of the elastic and viscoelastic properties of dentin by a nanoindentation creep test.

Dentin is the main supporting structure of teeth, but its mechanical properties may be adversely affected by pathological demineralization. The purposes of this study were to develop a quantitative approach to characterize the viscoelastic properties of dentin after de- and re-mineralization, and to examine the elastic properties using a nanoindentation creep test. Dentin specimens were prepared to receive both micro- and nano-indentation tests at wet and dry states. These tests were repeatedly performed after demineralization (1% citric acid for 3 days) and remineralization (artificial saliva immersion for 28 days). The nanoindentation test was executed in a creep mode, and the resulting displacement-time responses were disintegrated into primary (transient) and secondary (viscous) creep. The structural changes and mineral densities of dentin were also examined under SEM and microCT, respectively. The results showed that demineralization removed superficial minerals of dentin to the depth of 400 µm, and affected its micro- and nano-hardness, especially in the hydrate state. Remineralization only repaired the minerals at the surface layer, and partially recovered the nanohardness. Both the primary the secondary creep increased in the demineralized dentin, while the hydration further enhanced creep deformation of untreated and remineralized dentin. Remineralization reduced the primary creep of dentin, but did not effectively increase the viscosity. In conclusion, water plasticization increases the transient and viscous creep strains of demineralized dentin and reduces load sustainability. The nanoindentation creep test is capable of analyzing the elastic and viscoelastic properties of dentin, and reveals crucial information about creep responses.

The photothermal effect of silica-carbon hollow sphere-concanavalin A on liver cancer cells.

Hepatocellular carcinoma (HCC) is one of the most common cancers and causes of death by cancer. Concanavalin A (ConA) lectin can specifically bind to the glycoprotein receptors of HCC, which are produced by the aberrant overexpression of liver cancer cells. ConA was used in the current study to conjugate on silica-carbon hollow spheres (SCHSs) and applied in the thermal ablation therapy of liver cancer cell lines under near-infrared (NIR) laser irradiation. We found that the amount of ConA-SCHS complex binding to hepatoma cells was significantly higher than that seen with normal hepatocytes, based on flow cytometric analysis and confocal imaging. Hepatoma cells incubated with ConA-SCHSs were thus more easily killed by the subsequent irradiation with a NIR laser. The results show that the ConA-SCHS complex may enhance the interaction with highly expressed ConA receptors on hepatoma cells, and thus serve as an effective photothermal therapy agent for liver cancer treatment.

Rapid detection of dermatophytes and Candida albicans in onychomycosis specimens by an oligonucleotide array.

BACKGROUND: Onychomycosis is a fungal infection of nails, leading to the gradual destruction of the nail plate. Treatment of onychomycosis may need long-time oral antifungal therapy that can have potential side effects, thus accurate diagnosis of the disease before treatment is important. Culture for diagnosis of onychomycosis is time-consuming and has high false-negative rates. To expedite the diagnosis, an oligonucleotide array, based on hybridization between immobilized oligonucleotide probes and PCR products, for direct detection of dermatophytes and Candida albicans in clinical specimens was evaluated. METHODS: Species-specific oligonucleotide probes designed from the internal transcribed spacer (ITS) regions of the rRNA gene were immobilized on a nylon membrane. The assay procedures consisted of PCR amplification of the ITS using universal primers, followed by hybridization of the digoxigenin-labeled amplicons to probes on the array. Thirty two nail samples (29 patients) were analyzed by the array, and the results were compared with those obtained by culture. Array-positive but culture-negative samples were confirmed by cloning and re-sequencing of the amplified ITS and by reviewing patient's clinical data. The total recovery of culture and confirmed array-positive but culture-negative results was considered 100% and was used for performance evaluation of both methods. RESULTS: Concordant results were obtained in 21 samples (10 positives and 11 negatives) by both methods. Eleven samples were array-positive but culture-negative; among them, 9 samples were considered true positives after discrepant analysis. Comparing with culture, the array had significantly higher sensitivity [100% (95% CI 82.2% -100%) vs 52.6% (28.9% -75.5%), p <0.001] and negative predictive value [100% (71.3% -100%) vs 59.1% (36.4% -79.3%), p <0.05), while no significant differences were observed in specificity (84.6% vs 100%, p =0.48) and positive predictive value (90.5% vs 100%, p =1.0). The whole procedures of the array were about 24 h, whilst results from culture take 1 to 3 weeks. CONCLUSIONS: The array offers an accurate and rapid alternative to culture. Rapid diagnosis can expedite appropriate antifungal treatment of onychomycosis. However, the single site nature of this study conducted at a referral hospital invites caution.

Physicochemical properties and osteogenic activity of radiopaque calcium silicate-gelatin cements.

The purpose of this study is to evaluate the physicochemical properties and in vitro osteogenic activity of radiopaque calcium silicate-gelatin cements. The radiopacity, setting time, working time, flow, diametral tensile strength, pH value, washout resistance and morphology of the cements with gelatin (0, 5 and 10% by weight) were measured, which compared to a popular endodontic material, ProRoot white-colored mineral trioxide aggregate (WMTA). The cell morphology, cell attachment and proliferation, alkaline phosphatase and osteocalcin levels on the cements were measured by culturing the specimens with dental pulp cells. The results indicated that the presence of gelatin significantly (P < 0.05) reduced radiopacity and diametral tensile strength and prolonged setting time. Nevertheless, the 5 wt% gelatin cement had a radiopacity (5.1 mm of Al thickness) higher than ISO 6876:2001 standards (3 mm of Al thickness). The setting time (33 min), working time (9 min) and flow value (17.4 mm) of the 5 wt% gelatin cement were significantly (P < 0.05) better than those of WMTA (corresponding 165, 6 min and 14.2 mm). The fresh WMTA completely degraded after soaking in a physiological solution for 1 h, while the gelatin cements resisted washout, showing no noticeable breakdown even after 1 day of soaking. The gelatin cement enhanced the higher expression of cell attachment, proliferation and differentiation as compared to WMTA. It was concluded that the 5 wt% gelatin-calcium silicate hybrid cement appears to be promising as a radiopaque biomaterial for medical applications such as endodontics and vertebroplasty.

A filter-like AuNPs@MS SERS substrate for Staphylococcus aureus detection.

An accurate, highly sensitive and rapid identification assay of cells is extremely important in areas such as medical diagnosis, biological research, and environmental monitoring. Laboratory examinations of clinical isolates require time-consuming and complex processes to identify the colony count, with approximately 10(6)-10(8) cells needed for the characterization of strains. In the present study, a highly sensitive SERS filter-like substrate is prepared with AuNPs embedded in mesoporous silica (denoted as AuNPs@MS) synthesized by a simple one-spot method, and an example of its use for the filtration and concentration of analytes from aqueous samples is reported. In an application for Staphylococcus aureus SERS discrimination, the results show that the target cells can be concentrated on the filter-like AuNPs@MS substrates within a few seconds, with much better reproducibility with regard to the SERS spectra that are obtained. The experimental findings suggest that the AuNPs@MS substrate supports much higher intensity with more distinguishable peaks compared to Au/Cr-coated substrate, and the reproducibility is also significantly improved. The substrates investigated in this study generated 900 times more SERS signals at a concentration of 10(6)CFU/mL in the detection of S. aureus on mesoporous silica (Au wt%=0) when using AuNPs@MS with 16 wt% AuNPs. The limitation of this filter-like SERS substrate can be applicable for small volume samples (few to hundred microliter).

Composition-dependent protein secretion and integrin level of osteoblastic cell on calcium silicate cements.

The purpose of this study was to investigate the responses of the human osteosarcoma cell line MG63 to calcium silicate cements with different Si/Ca molar ratios and different surface roughness. In particular, the study evaluated integrin subunit levels, phosphor-focal adhesion kinase (pFAK) levels and protein production at the cell attachment stage. The results indicated that the surface roughness (variations within a factor of 10) of the cements did not play a prominent role in cell attachment and proliferation, but the effect of composition was highlighted. Increased pFAK and total integrin levels and promoted cell attachment and cell cycle progression were observed upon an increase in cement Si content. Cement with a higher Si content was beneficial for collagen Type I (COL I) adsorption, COL I secretion, and αlibß3 subintegrin expression, whereas cement with a higher Ca content increased fibronectin (FN) adsorption, FN secretion, and enhanced αvß1 subintegrin levels. These results establish composition-dependent differences in integrin binding as a mechanism regulating cellular responses to biomaterial surfaces.

Ripple structure-generated hybrid electrokinetics for on-chip mixing and separating of functionalized beads.

We present an electrokinetics-based microfluidic platform that is capable of on-chip manipulating, mixing, and separating microparticles through adjusting the interrelated magnitudes of dielectrophoresis and AC electroosmosis. Hybrid electrokinetic phenomenon is generated from an electric field-induced micro-ripple structure made of ultraviolet-curable glue. Size-dependent particle separation and selective removal over the ripple structure is demonstrated successfully. Varying the waveform from sine-wave to square-wave allows generating a fluid convection at specific positions to mix the antibody-functionalized beads and antigen. Potential application in the bead-based immunoassay was also demonstrated for immuno-reaction and subsequently separating the bead-bead aggregate and non-binding beads on-chip.

Quantitative determination of salvinorin A, a natural hallucinogen with abuse liability, in Internet-available Salvia divinorum and endemic species of Salvia in Taiwan.

In recent years, recreational use of Salvia divinorum (Lamiaceae), a herbal drug that contains a hallucinogenic ingredient, salvinorin A, has become a new phenomenon among young drug users. In Taiwan, as in many other countries, dry leaves of S. divinorum and its related concentrated extract products are available via the Internet. Besides S. divinorum, there are many endemic Salvia species whose salvinorin A content is yet unknown. To understand the abuse liability of these products, the aim of this study was to assess the concentration of salvinorin A in endemic Salvia species and Internet-available salvinorin A-related products. Samples of S. divinorum were purchased via the Internet and samples of eight endemic species of Salvia were collected in Taiwan, including S. arisanensis Hayata, S. coccinea Juss. ex Murr, S. hayatana Makino ex Hayata, S. japonica Thumb. ex Murr, S. nipponica Miq. Var. formosana (Hayata) Kudo, S. scapiformis Hance, S. tashiroi Hayata. Icon. PI. Formosan, and S. keitaoensis Hayata. The content of salvinorin A was determined by high performance liquid chromatography (HPLC). Salvinorin A was extracted from the dry leaves of S. divinorum and endemic species of Salvia with methanol and analyzed on a C-18 column by isocratic elution with a mobile phase of acetonitrile-water. Salvinorin A was detected in S. divinorum, but not in the endemic Salvia species of Taiwan. Therefore, endemic species of Salvia in Taiwan may not possess hallucinogenic potential. However, the potential harm from S. divinorum available via the Internet should be thoroughly assessed in Taiwan, and control measures similar to those implemented in many other countries should be considered.