Clinical Chemistry: Challenges for Analytical Chemistry and the Nanosciences from Medicine

Evaluating the effectiveness of a new student-centred laboratory training strategy in clinical biochemistry teaching

BACKGROUND

The error-proneness in the preanalytical and postanalytical stages is higher than that in the analytical stage of the total testing process. However, preanalytical and postanalytical quality management has not received enough attention in medical laboratory education and tests in clinical biochemistry courses.

METHODS/APPROACH

Clinical biochemistry teaching program aim to improve students' awareness and ability of quality management according to international organization for standardization 15,189 requirements. We designed a student-centred laboratory training program, according to case-based learning that included 4 stages: "establish an overall testing process based on the patient's clinical indicator, clarify principles, improve operational skills, and review process and continuous improvement". The program was implemented in our college during the winter semesters of 2019 and 2020. A total of 185 undergraduate students majoring in medical laboratory science participated in the program as a test group, and the other 172 students were set up as the control group and adopted the conventional method. The participants were asked to finish an online survey to evaluate the class at the end.

RESULTS/OUTCOMES

The test group had significantly better examination scores not only in experimental operational skills (89.27 ± 7.16 vs. 77.51 ± 4.72, p < 0.05 in 2019 grade, 90.31 ± 5.35 vs. 72.87 ± 8.41 in 2020 grade) but also in total examination (83.47 ± 6.16 vs. 68.90 ± 5.86 in 2019 grade, 82.42 ± 5.72 vs. 69.55 ± 7.54 in 2020 grade) than the control group. The results of the questionnaire survey revealed that the students in the test group better achieved classroom goals than those in the control group (all p < 0.05).

CONCLUSIONS

The new student-centred laboratory training program based on case-based learning in clinical biochemistry is an effective and acceptable strategy compared with the conventional training program.

Difunctional Hydrogel Optical Fiber Fluorescence Sensor for Continuous and Simultaneous Monitoring of Glucose and pH

It is significant for people with diabetes to know their body's real-time glucose level, which can guide the diagnosis and treatment. Therefore, it is necessary to research continuous glucose monitoring (CGM) as it gives us real-time information about our health condition and its dynamic changes. Here, we report a novel hydrogel optical fiber fluorescence sensor segmentally functionalized with fluorescein derivative and CdTe QDs/3-APBA, which can continuously monitor pH and glucose simultaneously. In the glucose detection section, the complexation of PBA and glucose will expand the local hydrogel and decrease the fluorescence of the quantum dots. The fluorescence can be transmitted to the detector by the hydrogel optical fiber in real time. As the complexation reaction and the swelling-deswelling of the hydrogel are all reversible, the dynamic change of glucose concentration can be monitored. For pH detection, the fluorescein attached to another segment of the hydrogel exhibits different protolytic forms when pH changes and the fluorescence changes correspondingly. The significance of pH detection is compensation for pH errors in glucose detection because the reaction between PBA and glucose is sensitive to pH. The emission peaks of the two detection units are 517 nm and 594 nm, respectively, so there is no signal interference between them. The sensor can continuously monitor glucose in 0-20 mM and pH in 5.4-7.8. The advantages of this sensor are multi-parameter simultaneous detection, transmission-detection integration, real-time dynamic detection, and good biocompatibility.

Microfluidic systems in clinical diagnosis

The use of microfluidic devices is highly attractive in the field of biomedical and clinical assessments, as their portability and fast response time have become crucial in providing opportune therapeutic treatments to patients. The applications of microfluidics in clinical diagnosis and point-of-care devices are continuously growing. The present review article discusses three main fields where miniaturized devices are successfully employed in clinical applications. The quantification of ions, sugars, and small metabolites is examined considering the analysis of bodily fluids samples and the quantification of this type of analytes employing real-time wearable devices. The discussion covers the level of maturity that the devices have reached as well as cost-effectiveness. The analysis of proteins with clinical relevance is presented and organized by the function of the proteins. The last section covers devices that can perform single-cell metabolomic and proteomic assessments. Each section discusses several strategically selected recent reports on microfluidic devices successfully employed for clinical assessments, to provide the reader with a wide overview of the plethora of novel systems and microdevices developed in the last 5 years. In each section, the novel aspects and main contributions of each reviewed report are highlighted. Finally, the conclusions and future outlook section present a summary and speculate on the future direction of the field of miniaturized devices for clinical applications.

Stoichiometric approach to quantitative analysis of biomolecules: the case of nucleic acids

Majority of protocols for quantitative analysis of biomarkers (including nucleic acids) require calibrations and target standards. In this work, we developed a principle for quantitative analysis that eliminates the need for a standard of a target molecule. The approach is based on stoichiometric reporting. While stoichiometry is a simple and robust analytical platform, its utility toward the analysis of biomolecules is very limited due to the lack of general methodologies for detecting the equivalence point. In this work, we engineer a new target/probe-binding model that enables detecting the equivalence point while maintaining an appropriate level of specificity. We establish the probe design principles through theoretical simulations and experimental confirmation. Further, we demonstrate the utility of the stoichiometric analysis via a proof-of-concept system based on oligonucleotide hybridization. Overall, the approach that requires neither standard nor calibration yields quantitative results with an adequate accuracy (> 90-110%) and a high specificity. The principles established in our work are very general and can extend beyond oligonucleotide targets toward quantitative analysis of many other biomolecules such as antibodies and proteins.

Colorimetric determination of Listeria monocytogenes using aptamer and urease dual-labeled magnetic nanoparticles and cucurbit[7]uril-mediated supramolecular assembly of gold nanoparticle

A host-guest colorimetric strategy is described for the detection of Listeria monocytogenes (L. monocytogenes). The optical probes were self-assembled based on the supramolecular interactions between the carbonyl groups of cucurbit[7]uril portals and gold nanoparticles (CB[7]-AuNPs). Aptamer and urease modified magnetic nanoparticles were used to specifically recognize and binding to L. monocytogenes, simultaneously hydrolyzing urea to produce ammonium ion (NH₄⁺) that can reverse CB[7] induced AuNPs aggregation. In the presence of L. monocytogenes, the above-mentioned magnetic conjugates preferentially bind to the bacterial surface, which results in blocking the catalytic active sites, thus inhibiting the production of ammonium ions. The normalized absorbance ratio of A_{700 nm}/A_{525 nm} was proportional to the L. monocytogenes concentration ranging from 10 to 10⁶ cfu·mL^-1, and the visual determination can be done down to 10 cfu·mL^-1. For spiked food samples analyzed without pre-enrichment, recoveries of 98.4% to 99.3% were achieved could be verified and RSD were less than 10%. This work may offer a broad prospect for sensitive and specific determination  of pathogens.

Monolithic integration of nanorod arrays on microfluidic chips for fast and sensitive one-step immunoassays

Here, we present integrated nanorod arrays on microfluidic chips for fast and sensitive flow-through immunoassays of physiologically relevant macromolecules. Dense arrays of Au nanorods are easily fabricated through one-step oblique angle deposition, which eliminates the requirement of advanced lithography methods. We report the utility of this plasmonic structure to improve the detection limit of the cardiac troponin I (cTnI) assay by over 6 × 105-fold, reaching down to 33.9 fg mL-1 (~1.4 fM), compared with an identical assay on glass substrates. Through monolithic integration with microfluidic elements, the device enables a flow-through assay for quantitative detection of cTnI in the serum with a detection sensitivity of 6.9 pg mL-1 (~0.3 pM) in <6 min, which was 4000 times lower than conventional glass devices. This ultrasensitive detection arises from the large surface area for antibody conjugation and metal-enhanced fluorescent signals through plasmonic nanostructures. Moreover, due to the parallel arrangement of flow paths, simultaneous detection of multiple cancer biomarkers, including prostate-specific antigen and carcinoembryonic antigen, has been fulfilled with increased signal-to-background ratios. Given the high performance of this assay, together with its simple fabrication process that is compatible with standard mass manufacturing techniques, we expect that the prepared integrated nanorod device can bring on-site point-of-care diagnosis closer to reality.

Prevention of extra-analytical phase errors by non-analytical automation in clinical laboratory

During previous decades, significant improvements in laboratory errors have become a substantial part of reducing preventable diagnostic errors. In clinical laboratory practice, the errors in the testing process are primarily associated with extra-analytical phase error sources, influencing the test result quality profoundly. Thus, the management of these critical error sources makes their effects preventable thanks to automation and computer sciences. The implementation of non-analytical automated systems requires a risk management strategy based on laboratory’s workflow and bottlenecks. Then, the improvements can be measured and evaluated by the usage of quality indicators (QI). Consequently, the total quality of laboratory diagnostics and higher patient safety is closely dependent on this type of automation. This review will help laboratory professionals, managers, and directors improve the total testing processes (TTP). The automation technologies have added a serious impact on the proficiency of laboratory medicine. Several instrumentations have now partially or entirely automated many manual tasks to improve standardization, organization, efficiency, and TTP quality. The implementation of non-analytical automation has made them manageable. As a result, non-analytical automation within and outside the clinical laboratory will necessarily lessen the error sources’ effect on the total test process, enhancing the quality of the test results.

Ophthalmic Sensors and Drug Delivery

Advances in multifunctional materials and technologies have allowed contact lenses to serve as wearable devices for continuous monitoring of physiological parameters and delivering drugs for ocular diseases. Since the tear fluids comprise a library of biomarkers, direct measurement of different parameters such as concentration of glucose, urea, proteins, nitrite, and chloride ions, intraocular pressure (IOP), corneal temperature, and pH can be carried out non-invasively using contact lens sensors. Microfluidic contact lens sensor based colorimetric sensing and liquid control mechanisms enable the wearers to perform self-examinations at home using smartphones. Furthermore, drug-laden contact lenses have emerged as delivery platforms using a low dosage of drugs with extended residence time and increased ocular bioavailability. This review provides an overview of contact lenses for ocular diagnostics and drug delivery applications. The designs, working principles, and sensing mechanisms of sensors and drug delivery systems are reviewed. The potential applications of contact lenses in point-of-care diagnostics and personalized medicine, along with the significance of integrating multiplexed sensing units together with drug delivery systems, have also been discussed.

The comparison between light-scattering detectors based on LED and photodiode for immunoprecipitation assays of transferrin and ferritin

Undoubtedly, light-emitting diodes (LEDs) and photodiodes (PDs) are indispensable optoelectronic devices in modern analytical chemistry. LEDs can serve as either light emitters or detectors, thus being an alternative to the most popular detection systems consisted of PD. In this contribution, a comparison between LED-LED and LED-PD detectors, operating in turbidimetric and nephelometric modes, has been carried out for immunoprecipitation detection of transferrin and ferritin. The greatest emphasis was placed on the study of detectors responses under different measurement conditions including current powering an emitter, amplification gain in the case of PD as detector or the construction of detection cells designed for the Multicommutated Flow Analysis (MCFA). The assumption was to obtain the fully-mechanized system with simple but efficient detection system to enable the determination of iron-binding proteins occurring at different concentration ranges in human body. As a result, the optimized arrangements of LED-LED and LED-PD setups were characterized by similar analytical characteristics, enabling the determination of transferrin with the detection limit (LOD) of 0.2 mg/L and RSDs of 2.8-4.8% for LED-LED, and LOD of 0.1 mg/L and RSDs of 0.9-3.6% for LED-PD. In the case of ferritin detection, only the response of the LED-PD detector was statistically distinguishable in the range of 130-198 μg/L of protein with recorded analytical signal change of 20 mV value. The addition of polymer for signal enhancement provided the increase of response range to 107-253 μg/L, enabling the developed system for detection of pathological serum ferritin levels.

An alternate methodology for studying diffusion and elution kinetics of dimethacrylate monomers through dentinal tubules

OBJECTIVE

Ethoxylated bisphenol A dimethacrylate (bisEMA) is a base monomer in several dental resin composites. It was the main aim of the present study to determine if bisEMA can reach the dental pulp by generally passive diffusion through the coronal dentinal tubules stimulated via eluent liquids surrounding the root structures only.

METHODS

In 20 human third molar teeth, standard Class-I occlusal cavities were prepared and provided either with an adhesive system alone or additionally with a composite restoration, according to the instructions of the manufacturer. The teeth were placed in an elution chamber such that the elution media only came into contact with the tooth root/tooth base where they were incubated at 37 °C for up to 7 d. Samples were taken after 1, 2, 4 and 7 d. Gas chromatography/mass spectrometry was used to identify bisEMA and other monomers in ethanol/water (3:1) and aqueous eluates.

RESULTS

bisEMA was only found in ethanol/water eluates, where the teeth had received a composite restoration. Traces of bisEMA with up to three ethylene oxide units could be detected in these eluates. Depending on the dentin thickness, different elution kinetics of bisEMA were determined. Regardless of the treatment of teeth, triethylene glycol dimethacrylate (TEGDMA) and tetraethylene glycol dimethacrylate (TEEGDMA) were found in ethanolic/aqueous eluates in equal amounts. Most TEGDMA and TEEGDMA diffused through the dentin within the first 24 h.

SIGNIFICANCE

Depending on the dentin layer thickness, bisEMA was released for varied time periods, resulting in varied concentrations and exposure times for the different cells of the dental pulp. The concentrations of TEGDMA and TEEGDMA were greatest for cells of the dental pulp within the first 24 h.

High-throughput genetic newborn screening for spinal muscular atrophy by rapid nucleic acid extraction from dried blood spots and 384-well qPCR

Establishing nucleic acid-based assays for genetic newborn screening (NBS) provides the possibility to screen for genetically encoded diseases like spinal muscular atrophy (SMA), best before the onset of symptoms. Such assays should be easily scalable to 384-well reactions that make the screening of up to 2000 samples per day possible. We developed a test procedure based on a cleanup protocol for dried blood spots and a quantitative (q)PCR to screen for a homozygous deletion of exon 7 of the survival of motor neuron 1 gene (SMN1) that is responsible for >95% of SMA patients. Performance of this setup is evaluated in detail and tested on routine samples. Our cleanup method for nucleic acids from dried blood spots yields enough DNA for diverse subsequent qPCR applications. To date, we have applied this approach to test 213,279 samples within 18 months. Thirty patients were identified and confirmed, implying an incidence of 1:7109 for the homozygous deletion. Using our cleanup method, a rapid workflow could be established to prepare nucleic acids from dried blood spot cards. Targeting the exon 7 deletion, no invalid, false-positive, or false-negative results were reported to date. This allows timely identification of the disease and grants access to the recently introduced treatment options, in most cases before the onset of symptoms. Carriers are not identified, thus, there are no concerns of whether to report them.

Wearable Contact Lens Biosensors for Continuous Glucose Monitoring Using Smartphones

Low-cost, robust, and reusable continuous glucose monitoring systems that can provide quantitative measurements at point-of-care settings is an unmet medical need. Optical glucose sensors require complex and time-consuming fabrication processes, and their readouts are not practical for quantitative analyses. Here, a wearable contact lens optical sensor was created for the continuous quantification of glucose at physiological conditions, simplifying the fabrication process and facilitating smartphone readouts. A photonic microstructure having a periodicity of 1.6 μm was printed on a glucose-selective hydrogel film functionalized with phenylboronic acid. Upon binding with glucose, the microstructure volume swelled, which modulated the periodicity constant. The resulting change in the Bragg diffraction modulated the space between zero- and first-order spots. A correlation was established between the periodicity constant and glucose concentration within 0-50 mM. The sensitivity of the sensor was 12 nm mM^-1, and the saturation response time was less than 30 min. The sensor was integrated with commercial contact lenses and utilized for continuous glucose monitoring using smartphone camera readouts. The reflected power of the first-order diffraction was measured via a smartphone application and correlated to the glucose concentrations. A short response time of 3 s and a saturation time of 4 min was achieved in the continuous monitoring mode. Glucose-sensitive photonic microstructures may have applications in point-of-care continuous monitoring devices and diagnostics at home settings.

A DNA-Based Assay for Digoxin Detection

The most common method for quantifying small-molecule drugs in blood samples is by liquid chromatography in combination with mass spectrometry. Few immuno-based assays are available for the detection of small-molecule drugs in blood. Here we report on a homogeneous assay that enables detection of the concentration of digoxin spiked into in a plasma sample. The assay is based on a shift in the equilibrium of a DNA strand displacement competition reaction, and can be performed in 30 min for concentrations above 10 nM. The equilibrium shift occurs upon binding of anti-digoxigenin antibody. As a model, the assay provides a potential alternative to current small-molecule detection methods used for therapeutic drug monitoring.

Combination of Mass Signal Amplification and Isotope-Labeled Alkanethiols for the Multiplexed Detection of miRNAs

We report a fast and sensitive method for the multiplexed detection of miRNAs by combining mass signal amplification and isotope-labeled signal reporter molecules. In our strategy, target miRNAs are captured specifically by immobilized DNAs on gold nanoparticles (AuNPs), which carry a large number of small molecules, called amplification tags (Am-tags), as the reporter for the detection of target miRNAs. For multiplexed detection, we designed and synthesized four Am-tags containing 0, 4, 8, 12 isotopes so that they had same molecular properties but different molecular weights. By observing the mass signals of the Am-tags on AuNPs decorated along with different probe DNAs, four types of miRNAs in a sample could be easily discriminated, and the relative amounts of these miRNAs could be quantified. The practicability of our strategy was further verified by measuring the expression levels of two miRNAs in HUVECs in response to different CuSO₄ concentrations.

Glucose-Sensitive Hydrogel Optical Fibers Functionalized with Phenylboronic Acid

Hydrogel optical fibers are utilized for continuous glucose sensing in real time. The hydrogel fibers consist of poly(acrylamide-co-poly(ethylene glycol) diacrylate) cores functionalized with phenylboronic acid. The complexation of the phenylboronic acid and cis-diol groups of glucose enables reversible changes of the hydrogel fiber diameter. The analyses of light propagation loss allow for quantitative glucose measurements within the physiological range.

Dual Electrophoresis Detection System for Rapid and Sensitive Immunoassays with Nanoparticle Signal Amplification

An electrophoretic technique was combined with an enzyme-linked immunosorbent assay (ELISA) system to achieve a rapid and sensitive immunoassay. A cellulose acetate filter modified with polyelectrolyte multilayer (PEM) was used as a solid substrate for three-dimensional antigen-antibody reactions. A dual electrophoresis process was used to induce directional migration and local condensation of antigens and antibodies at the solid substrate, avoiding the long diffusion times associated with antigen-antibody reactions in conventional ELISAs. The electrophoretic forces drove two steps in the ELISA process, namely the adsorption of antigen, and secondary antibody-labelled polystyrene nanoparticles (NP-Ab). The total time needed for dual electrophoresis-driven detection was just 4 min, nearly 2 h faster than a conventional ELISA system. Moreover, the rapid NP-Ab electrophoresis system simultaneously achieved amplification of the specific signal and a reduction in noise, leading to a more sensitive NP-Ab immunoassay with a limit of detection (LOD) of 130 fM, and wide range of detectable concentrations from 0.13 to 130 pM. These results suggest that the combination of dual electrophoresis detection and NP-Ab signal amplification has great potential for future immunoassay systems.

In-electrode vs. on-electrode: ultrasensitive Faraday cage-type electrochemiluminescence immunoassay

A new-concept of an "in-electrode" Faraday cage-type electrochemiluminescence immunoassay (ECLIA) method for the ultrasensitive detection of neurotensin (NT) was reported with capture antibody (Ab1)-nanoFe3O4@graphene (GO) and detector antibody (Ab2)&N-(4-aminobutyl)-N-ethylisoluminol (ABEI)@GO, which led to about 1000-fold improvement in sensitivity by extending the Helmholtz plane (OHP) of the proposed electrode assembly effectively.

Immobilization of Carbon Dots in Molecularly Imprinted Microgels for Optical Sensing of Glucose at Physiological pH

Nanosized carbon dots (CDs) are emerging as superior fluorophores for biosensing and a bioimaging agent with excellent photostability, chemical inertness, and marginal cytotoxicity. This paper reports a facile one-pot strategy to immobilize the biocompatible and fluorescent CDs (∼6 nm) into the glucose-imprinted poly(N-isopropylacrylamide-acrylamide-vinylphenylboronic acid) [poly(NIPAM-AAm-VPBA)] copolymer microgels for continuous optical glucose detection. The CDs designed with surface hydroxyl/carboxyl groups can form complexes with the AAm comonomers via hydrogen bonds and, thus, can be easily immobilized into the gel network during the polymerization reaction. The resultant glucose-imprinted hybrid microgels can reversibly swell and shrink in response to the variation of surrounding glucose concentration and correspondingly quench and recover the fluorescence signals of the embedded CDs, converting biochemical signals to optical signals. The highly imprinted hybrid microgels demonstrate much higher sensitivity and selectivity for glucose detection than the nonimprinted hybrid microgels over a clinically relevant range of 0-30 mM at physiological pH and benefited from the synergistic effects of the glucose molecular contour and the geometrical constraint of the binding sites dictated by the glucose imprinting process. The highly stable immobilization of CDs in the gel networks provides the hybrid microgels with excellent optical signal reproducibility after five repeated cycles of addition and dialysis removal of glucose in the bathing medium. In addition, the hybrid microgels show no effect on the cell viability in the tested concentration range of 25-100 μg/mL. The glucose-imprinted poly(NIPAM-AAm-VPBA)-CDs hybrid microgels demonstrate a great promise for a new glucose sensor that can continuously monitor glucose level change.

Multiplexed DNA detection using a gold nanorod-based fluorescence resonance energy transfer technique

A fluorescence resonance energy transfer method for multiplex detection DNA based on gold nanorods had been successfully constructed. This method is simple, easy to operate, good selectivity, no requirement to label the probe molecule and can analyze simultaneously multiple targets of DNA in one sample. The limit of detection for the 18-mer, 27-mer and 30-mer targets is 0.72, 1.0 and 0.43 nM at a signal-to-noise ratio of 3. The recoveries of three targets were 96.57-98.07%, 99.12-100.04% and 97.29-99.93%, respectively. The results show that the method can be used to analyze a clinical sample or a biological sample; it also can be used to develop new probes for rapid, sensitive and highly selective multiplex detection of analytes in real samples.

Toward point-of-care diagnostics with consumer electronic devices: the expanding role of nanoparticles

A review of the role that nanoparticles can play in point-of-care diagnostics that utilize consumer electronic devices such as cell phones and smartphones for readout, including an overview of important concepts and examples from the literature.

High throughput immunosenor based on multi-label strategy and a novel array electrode

Accurate prediction of a particular cancer can be achieved by measuring multiplex biomarkers. Traditional methods for multi-biomarkers detection are either multi-spots assay with chip or multi-label assay with one detection spot. However, the detection throughput of these two approaches is limited by the substrate area and the numbers of available label respectively. To solve this problem, in the present study, an immunoassay was firstly prepared by combining multi-label strategy and multi-spot assay with a novel array electrode for simultaneous detection of six biomarkers for hepatocellular carcinoma (HCC). The detection throughput of the proposed method was doubled in comparison with traditional multi-spots assay (one target protein was detected on each analytic spot), which could greatly enhance the sensitivity and specificity of HCC diagnosis. This detection model may serve as the starting point for high throughput of multianalyte assay.

Responsive materials for self-regulated insulin delivery

With diabetes mellitus becoming an important public health concern, insulin-delivery systems are attracting increasing interest from both scientific and technological researchers. This feature article covers the present state-of-the-art glucose-responsive insulin-delivery system (denoted as GRIDS), based on responsive polymer materials, a promising system for self-regulated insulin delivery. Three types of GRIDS are discussed, based on different fundamental mechanisms of glucose-recognition, with: a) glucose enzyme, b) glucose binding protein, and c) synthetic boronic acid as the glucose-sensitive component. At the end, a personal perspective on the major issues yet to be worked out in future research is provided.

Porous bead-based diagnostic platforms: bridging the gaps in healthcare

Advances in lab-on-a-chip systems have strong potential for multiplexed detection of a wide range of analytes with reduced sample and reagent volume; lower costs and shorter analysis times. The completion of high-fidelity multiplexed and multiclass assays remains a challenge for the medical microdevice field; as it struggles to achieve and expand upon at the point-of-care the quality of results that are achieved now routinely in remote laboratory settings. This review article serves to explore for the first time the key intersection of multiplexed bead-based detection systems with integrated microfluidic structures alongside porous capture elements together with biomarker validation studies. These strategically important elements are evaluated here in the context of platform generation as suitable for near-patient testing. Essential issues related to the scalability of these modular sensor ensembles are explored as are attempts to move such multiplexed and multiclass platforms into large-scale clinical trials. Recent efforts in these bead sensors have shown advantages over planar microarrays in terms of their capacity to generate multiplexed test results with shorter analysis times. Through high surface-to-volume ratios and encoding capabilities; porous bead-based ensembles; when combined with microfluidic elements; allow for high-throughput testing for enzymatic assays; general chemistries; protein; antibody and oligonucleotide applications.

Ultrasensitive and real-time detection of proteins in blood using a potentiometric carbon-nanotube aptasensor

Potentiometric sensing represents the preferred technique in many routine measurements of pH and ions. Unfortunately, the simplicity of the technique has not been exploited so far in high throughput biomolecular sensing. In this work, we demonstrate the capabilities of the hybrid functional material carbon nanotubes/aptamer for the creation of a new generation of nuclease-resistant aptasensors using the potentiometric transduction capabilities of single-walled carbon nanotubes in combination with the recognition capabilities of a protein-specific RNA aptamer. The aptasensor was used to detect and identify disease-related proteins at attomolar concentration values in a rapid and non-expensive way. The variable surface glycoprotein from African Trypanosomes was chosen as an ideal model system for a pathogenic exoantigen protein in a clinical sample. Variations in the electromotive force are achieved in real-time upon the direct addition of diluted real blood samples containing the target protein thus eliminating the need of preliminary matrix removal. This work would open the door to real-time diagnostic assays for a wide range of diseases, but also to the rapid molecular detection of several proteins in truly customizable protein biosensing platforms.

Cytokine release from human leukocytes exposed to silorane- and methacrylate-based dental materials

OBJECTIVES

Silorane-based dental monomers contain an epoxy functional group. Less is known about the toxicological and inflammatory potential of silorane-based composites. Therefore we compared the release of 24 cytokines from human leukocytes after incubation with silorane-based Filtek™ Silorane (Silo) and methacrylate-based TetricEvo Flow® (TC).

METHODS

Leukocytes from nine healthy test persons (P) were incubated with Silo or TC for up to 72h. All 24h cytokines were quantified with a magnetic bead assay.

RESULTS

Silo stimulates the leukocytes to higher release of cytokines when compared to TC. 72h after beginning the experiment, leukocytes from P6 incubated with Silo secreted more than an 18-fold amount of interleukin (IL)-6 when compared with leukocytes incubated with TC (771.8 vs 42.1pg/ml). Only leukocytes from P8 incubated with Silo release up to 14.4pg/ml IL-2 after 72h.

SIGNIFICANCE

The significantly higher induction of cytokines with Silo in comparison to TC is test person independent. This indicates a higher sensitization potential for Silo. Because of the cytokine release pattern (especially the release of T-cell dependent IL-2) from leukocytes from P8 after incubation with Silo it is likely that P8 can develop an allergic Type IV sensitization to Silo. Therefore the cytokine release assay is a helpful tool for providing information about possible immunological reactions to dental resins in individual cases as well as for a general risk assessment and comparison between different dental materials.

Liquid-phase microextraction and desorption electrospray ionization mass spectrometry for identification and quantification of basic drugs in human urine

Hollow fibre liquid-phase microextraction (LPME) and desorption electrospray ionization mass spectrometry (DESI-MS) were evaluated for the identification and quantification of basic drugs in human urine samples. The selective extraction capabilities of three-phase LPME provided a significant reduction in the matrix effects otherwise observed in direct DESI-MS analysis of urine samples. Aqueous LPME extracts (in 10 mM HCl) were deposited on porous Teflon, dried at room temperature, and the dried spots were then analyzed directly with DESI-MS in full scan mode. Pethidine, diphenhydramine, nortriptyline, and methadone were used as model compounds for identification, and their limits of identification were determined to be 100, 25, 100, and 30 ng/mL, respectively. In a reliability test with 19 spiked urine samples, 100% of the positive samples containing the model drugs in concentrations at or above the limit of identification were identified. Diphenhydramine was used as a model compound for quantitative analysis with diphenhydramine-d(5) as an internal standard. The calibration curve was linear in the range 50-2000 ng/mL (R(2) = 0.992) with a limit of quantification at approximately 140 ng/mL. The intra- and inter-day relative standard deviations were <9.5%. In a reliability test with six spiked urine samples, deviations between the measured and the true values for diphenhydramine were in the range 0.2-22.9%.

Iron core/shell nanoparticles as magnetic drug carriers: possible interactions with the vascular compartment

Aims: Nanomagnets with metal cores have recently been shown to be promising candidates for magnetic drug delivery due to higher magnetic moments compared with commonly used metal oxides. Successful application strongly relies on a safe implementation that goes along with detailed knowledge of interactions and effects that nanomagnets might impart once entering the body. Materials & Methods: In this work, we put a particular focus on the interactions of ultra-strong metal nanomagnets (≥ three-times higher in magnetization compared with oxide nanoparticles) within the vascular compartment. Individual aspects of possible effects are addressed, including interactions with the coagulation cascade, the complement system, phagocytes and toxic or inflammatory reactions both by blood and endothelial cells in response to nanomagnet exposure. Results: We show that carbon-coated metal nanomagnets are well-tolerated by cells of the vascular compartment and have only minor effects on blood coagulation. Conclusion: These findings provide the fundament to initiate successful first in vivo evaluations opening metal nanomagnets with improved magnetic properties to fascinating applications in nanomedicine.

Microfluidic chips for point-of-care immunodiagnostics

We might be at the turning point where research in microfluidics undertaken in academia and industrial research laboratories, and substantially sponsored by public grants, may provide a range of portable and networked diagnostic devices. In this Progress Report, an overview on microfluidic devices that may become the next generation of point-of-care (POC) diagnostics is provided. First, we describe gaps and opportunities in medical diagnostics and how microfluidics can address these gaps using the example of immunodiagnostics. Next, we conceptualize how different technologies are converging into working microfluidic POC diagnostics devices. Technologies are explained from the perspective of sample interaction with components of a device. Specifically, we detail materials, surface treatment, sample processing, microfluidic elements (such as valves, pumps, and mixers), receptors, and analytes in the light of various biosensing concepts. Finally, we discuss the integration of components into accurate and reliable devices.

Versatile immunoassays based on isomagnetophoresis

We report an isomagnetophoretic immunoassay capable of detecting an attomolar level of proteins and adjusting the dynamic range of target analytes. Here, the magnetic nanoparticles are used as labels on microbeads in sandwich-type immunoassay, detecting the amount of bound analytes by isomagnetophoretic focusing the solid-support microbeads under the magnetic susceptibility gradient and magnetic field in a microchannel. For the practical purpose, this platform was applied to detect three types of breast cancer biomarkers.

Real-time potentiometric detection of bacteria in complex samples

Detecting and identifying pathogen bacteria is essential to ensure quality at all stages of the food chain and to diagnose and control microbial infections. Traditional detection methods, including those based on cell culturing, are tedious and time-consuming, and their further application in real samples generally implies more complex pretreatment steps. Even though state-of-the-art techniques for detecting microorganisms enable the quantification of very low concentrations of bacteria, to date it has been difficult to obtain successful results in real samples in a simple, reliable, and rapid manner. In this Article, we demonstrate that the label-free detection and identification of living bacteria in real samples can be carried out in a couple of minutes and in a direct, simple, and selective way at concentration levels as low as 6 colony forming units/mL (CFU) in complex matrices such as milk or 26 CFU/mL in apple juice where the pretreatment step of samples is extremely easy. We chose Escherichia coli ( E. coli ) CECT 675 cells as a model organism as a nonpathogenic surrogate for pathogenic E. coli O157:H7 to test the effectiveness of a potentiometric aptamer-based biosensor. This biosensor uses single-walled carbon nanotubes (SWCNT) as excellent ion-to-electron transducers and covalently immobilized aptamers as biorecognition elements. The selective aptamer-target interaction significantly changes the electrical potential, thus allowing for both interspecies and interstrain selectivity and enabling the direct detection of the target. This technique is therefore a powerful tool for the immediate identification and detection of microorganisms. We demonstrate the highly selective detection of living bacteria with an immediate linear response of up to 10(4) CFU/mL. The biosensor can be easily built and used, is regenerated without difficulty, and can be used at least five times with no loss in the minimum amount of detected bacteria.