High Biological Affinity Research Articles

Fluorescent aptasensor based on competitive recognition strategies and point-of-care testing system for brain natriuretic peptide detection

Brain natriuretic peptide (BNP) is the preferred biomarker for clinical analysis, widely used in early screening and prognostic monitoring of cardiovascular and neurological diseases. Due to the low concentration and short half-life of BNP in the blood, its sensitive detection remains a challenge that must be overcome. With the rapid development of molecular diagnosis and point-of-care testing (POCT), developing a BNP biosensor with high sensitivity, good stability, accuracy, speed, and low-cost is of great significance for clinical applications and emergency diagnosis. However, BNP in human blood exists in various forms, and traditional fluorescence sensors may lead to overestimation of the concentration. In this work, we constructed an “on” fluorescent aptasensor based on competitive recognition strategy for quantitative detection of BNP, and built a fluorescence sensing detection system based on smartphone to achieve rapid on-site detection. We designed a specific aptamer labeled with carboxyfluorescein (FAM) with a simple structure and high biological affinity for selective capture of BNP, and utilized the large specific surface area and excellent fluorescence quenching effect of carboxylated graphene oxide (GO-COOH) as a carrier and quencher for the aptasensor. By optimizing experimental parameters such as aptamer and GO-COOH concentrations, as well as quenching/recovery time, linear sensitive detection of BNP was achieved in the concentration range of 0.01 ng/mL–10 ng/mL, with a detection limit as low as 10 pg/mL, good specificity, and excellent application potential in artificial serum spiking experiments. Additionally, a stable and sensitive fluorescence signal collection system has been developed to meet the needs of portable detection, breaking through the usage environment of traditional fluorescence detection equipment and filling the gap of portable fluorescence biosensing. In summary, we have creatively proposed a fluorescent aptasensor that enables rapid and sensitive detection of BNP and the development of low-cost fluorescent biosensors. The combination with POCT has shown broad application prospects and also provides some ideas for the fluorescence detection of other protein biomarkers.

Sex estimation using long bones in the largest burial site of the Copper Age: Linear discriminant analysis and random forest

Sex estimation of the individuals in a sample is fundamental for any bioarchaeological study to define a particular demographic assemblage or to classify isolated remains. Long bones are an excellent alternative for sex estimation when the most dimorphic anatomical parts are not preserved or are highly altered. Here we propose a set of discriminant functions and classification models to estimate the sex of prehistoric individuals using linear discriminant analysis and machine learning approaches. Different osteometric variables were taken from the humeri, ulnae, radii, femurs and tibias of a sample of 109 articulated skeletons buried in the collective tomb of Camino del Molino (Region of Murcia, SE-Spain), dated to the 3rd millennium BC. Sex was estimated based on standard anthropological methods and ancient DNA analysis of a control sample. Fifty-two discriminant functions with prediction thresholds higher than 0.8 on the ROC curve were obtained using independent (22) and combined variables (30). The best LDA models for sex prediction were those based on proximal epiphyseal widths or their combination with other variables, reaching values close to 0.98 on the ROC curve. The random forest-based model obtained an accuracy of 0.94 and confirmed the importance of epiphyseal widths in sex classification. This analysis is more comprehensive than univariate LDA, as it allows for ranking the importance of bones in sex discrimination and considers correlations between long bones rather than treating them as independent observations. In contrast, applying LDA to each bone makes it easier to predict the sex of other coeval collections that do not have such a complete sample. This work aims to overcome the scarcity of methods that can be applied to sex estimation of the large volume of isolated remains from Camino del Molino and for other Mediterranean skeletal series from the Late Prehistory with high biological affinity and that share similar environmental conditions.

Artificial intelligence for prediction of biological activities and generation of molecular hits using stereochemical information

In this work, we develop a method for generating targeted hit compounds by applying deep reinforcement learning and attention mechanisms to predict binding affinity against a biological target while considering stereochemical information. The novelty of this work is a deep model Predictor that can establish the relationship between chemical structures and their corresponding pIC_{50} values. We thoroughly study the effect of different molecular descriptors such as ECFP4, ECFP6, SMILES and RDKFingerprint. Also, we demonstrated the importance of attention mechanisms to capture long-range dependencies in molecular sequences. Due to the importance of stereochemical information for the binding mechanism, this information was employed both in the prediction and generation processes. To identify the most promising hits, we apply the self-adaptive multi-objective optimization strategy. Moreover, to ensure the existence of stereochemical information, we consider all the possible enumerated stereoisomers to provide the most appropriate 3D structures. We evaluated this approach against the Ubiquitin-Specific Protease 7 (USP7) by generating putative inhibitors for this target. The predictor with SMILES notations as descriptor plus bidirectional recurrent neural network using attention mechanism has the best performance. Additionally, our methodology identify the regions of the generated molecules that are important for the interaction with the receptor’s active site. Also, the obtained results demonstrate that it is possible to discover synthesizable molecules with high biological affinity for the target, containing the indication of their optimal stereochemical conformation.

Rapid screening, isolation, and activity evaluation of potential xanthine oxidase inhibitors in Polyporus umbellatus and mechanism of action in the treatment of gout.

Studies show that Polyporus umbellatus has some pharmacological effects in enhancing immunity and against gout. We aimed to establish new techniques for extraction, biological activity screening, and preparation of xanthine oxidase inhibitors (XODIs) from P.umbellatus. First, the extraction of P.umbellatus was investigated using the back propagation (BP) neural network genetic algorithm mathematical regression model, and the extraction variables were optimised to maximise P.umbellatus yield. Second, XODIs were rapidly screened using ultrafiltration, and the change of XOD activity was tested by enzymatic reaction kinetics experiment to reflect the inhibitory effect of active compounds on XOD. Meanwhile, the potential anti-gout effects of the obtained active substances were verified using molecular docking, molecular dynamics simulations, and network pharmacology analysis. Finally, with activity screening as guide, a high-speed countercurrent chromatography (HSCCC) method combined with consecutive injection and two-phase solvent system preparation using the UNIFAC mathematical model was successfully developed for separation and purification of XODIs, and the XODIs were identified using MS and NMR. The results verified that polyporusterone A, polyporusterone B, ergosta-4,6,8(14),22-tetraen-3-one, and ergosta-7,22-dien-3-one of P.umbellatus exhibited high biological affinity towards XOD. Their structures have been further identified by NMR, indicating that the method is effective and applicable for rapid screening and identification of XODIs. This study provides new ideas for the search for natural XODIs active ingredients, and the study provide valuable support for the further development of functional foods with potential therapeutic benefits.

医用セラミックスに関する基礎研究とバイオインスパイアード材料開発への展開

Certain types of ceramics have property that shows direct bonding to living bone tissue in vivo, and are referred to as bioactive materials. As a bioactive material, Bioglass® was discovered and developed in early 1970’s, inorganic glasses and materials based on them have been studied for bone substitutes for tissue repairing. In addition, elucidation of the mechanism by which they express their high biological affinity has been studied. The author has been interested in elucidating the mechanisms by which inorganic glasses show high biological affinity to bond to living bone, and has carried out fundamental research, as well as developing novel biomaterials based on the materials chemistry of glasses and ceramics. The science and technology of the bioactive glasses have made a significant contribution to the field of medicine. Whilst, 2022 has been designated as the International Year of Glass by the United Nations General Assembly, and events commemorating the science, technology and art associated with glass are being held around the world. As part of these events, a special feature on glass science and bioinspired materials was also held at the 2022 Spring Meeting of the Japan Society of Powder and Powder Metallurgy. Against this background, this paper describes the review of the author’s achievement awards, with a particular focus on glass and biomaterials, and the development of novel materials using bioinspired methods.

Ultrathin Mo2S3 Nanowire Network for High-Sensitivity Breathable Piezoresistive Electronic Skins.

Flexible piezosensing electronic skins (e-skins) have attracted considerable interest owing to their applications in real-time human-health monitoring, human-machine interactions, and soft bionic robot perception. However, the fabrication of piezosensing e-skins with high sensitivity, biological affinity, and good permeability at the same time is challenging. Herein, we designed and synthesized Mo2S3 nanowires by inserting ∞1[Mo2+S] chains between MoS2 interlayers. The resulting Mo2S3 nanowires feature high conductivity (4.9 × 104 S m-1) and a high aspect ratio (∼200). An ultrathin (∼500 nm) Mo2S3 nanowire network was fabricated using a simple liquid/liquid interface self-assembly method, showing high piezoresistive sensitivity (5.65 kPa-1), a considerably low pressure detection limit (0.08 Pa), and gratifying air permeability. Moreover, this nanowire network can be directly attached to human skin for real-time human pulse detection, finger movement monitoring, and sign language recognition, exhibiting excellent potential for health monitoring and human-machine interactions.

Aqueous mechano-bactericidal action of acicular aragonite crystals

Nanoneedle structures on dragonfly and cicada wing surfaces or black silicon nanoneedles demonstrate antibacterial phenomena, namely mechano-bactericidal action. These air-exposed, mechano-bactericidal surfaces serve to destroy adherent bacteria, but their bactericidal action in the water is no precedent to report. Calcium carbonate easily accumulates on solid surfaces during long-term exposure to hard water. We expect that aragonite nanoneedles, in particular, which grow on TiO2 during the photocatalytic treatment of calcium-rich groundwater, exhibit mechano-bactericidal action against bacteria in water. Here, we showed that acicular aragonite modified on TiO2 ceramics prepared from calcium bicarbonate in mineral water by photocatalysis exhibits mechanical bactericidal activity against E. coli in water. Unmodified, calcite-modified and aragonite-modified TiO2 ceramics were exposed to water containing E. coli (in a petri dish), and their bactericidal action over time was investigated under static and agitated conditions. The surfaces of the materials were observed by scanning electron microscopy, and the live/dead bacterial cells were observed by confocal laser scanning microscopy. As a result, the synergistic bactericidal performance achieved by mechano-bactericidal action and photocatalysis was demonstrated. Aragonite itself has a high biological affinity for the human body different from the other whisker-sharpen nanomaterials, therefore, the mechano-bactericidal action of acicular aragonite in water is expected to inform the development of safe water purification systems for use in developing countries.

Effect of protein adsorption on electrospun hemoglobin/gelatin-MWCNTs microbelts modified electrode: Toward electrochemical measurement of hydrogen peroxide

The on-line electrochemical analysis is one of powerful strategies in analytical chemistry and pathophysiology. To achieve high sensitivity and long-term stability of electrochemical biosensor, the bottleneck challenge is the spontaneous proteins adsorption onto the electrode surface within the biological fluids or in vivo environments. In this work, a hemoglobin/gelatin-multiwalled carbon nanotubes microbelts modified electrode (Hb/gelatin-MWCNTs/GC electrode) was successfully fabricated via one-step electrospinning process. The results of atomic force microscopy (AFM), scanning electron microscopy (SEM) and water contact angle test confirmed the electrospun Hb/gelatin-MWCNTs microbelts possessed smooth and hydrophilic surfaces. Furthermore, the electrospun Hb/gelatin-MWCNTs/GC electrode after protein adsorption displayed an excellent electrocatalytic sensitivity toward the reduction of hydrogen peroxide (H2O2). Moreover, the Hb/gelatin-MWCNTs/GC electrode presented very high biological affinity to H2O2 (Kmapp=503.4 ± 2.8 μmol L−1) after 360 min protein adsorption compared to that of the electrode before protein adsorption (Kmapp=298.1 ± 3.1 μmol L−1). The microbelts constructed H2O2 biosensor showed high selectivity, stability and reproducibility after protein adsorption. Therefore, this work provided the proof of the concept that the electrospun Hb/gelatin-MWCNTs/GC electrode displayed excellent sensing performance to H2O2 after protein adsorption, which could enable the implantable electrochemical biosensor for the on-line analysis.

Zencefil (Zingiber Officinale) Kök Ekstresi Kullanılarak Çinko Oksit Nanoparçacıkların Yeşil Sentezi ve Glikoz Biyosensörü Olarak Uygulaması

Green synthesis of nanoparticles via plant extracts has become an important research field in nanotechnology. In the present study, a novel amperometric glucose biosensor based on the green synthesized zinc oxide (ZnO) nanoparticles by using Zingiber officinale root was fabricated. Glucose oxidase (GOx) was immobilized onto the ZnO-modified carbon paste electrode (CPE) via cross-linking with glutaraldehyde. The prepared biosensor (GOx-ZnO/CPE) exhibited a good electrocatalytic ability to the determination of glucose. The biosensor also showed a low detection limit (14.7 μM), a rapid response (less than 1 second), high sensitivity (15.98 µA mM−1 cm−2), and higher biological affinity (the Michaelis−Menten constant was estimated as 0.99 mM). Moreover, the prepared biosensor exhibited good anti-interference capability in relation to ascorbic acid (AA) and uric acid (UA). These results demonstrated that a simple and a cost effectiveness biosensor was fabricated for the determination of glucose.

Effect of protein adsorption on bioelectrochemistry of electrospun core-shell MWCNTs/gelatin-Hb nanobelts on electrode surface

Implantable electrochemical biosensor is one powerful tool for the accurate and reliable measurements of small molecules in vivo. However, the electrode is inevitably subjected to the protein adsorption when implanted into the living animals, affecting the sensitivity and stability of biosensor. Herein, we designed the multi-walled carbon nanotubes/gelatin-hemoglobin (MWCNTs/gelatin-Hb) core-shell nanobelts constructed on glassy carbon electrode (GC) using the one-step electrospinning technique for studying the effect of protein adsorption on the electrode surface properties. The results of the water contact angle and the scanning electron microscopy (SEM) showed that the electrospun core-shell MWCNTs/gelatin-Hb nanobelts present hydrophilic and certain anti-protein adsorption properties. Direct electron transfer between the Hb molecules in the electrospun core-shell nanobelts and electrode and catalysis of hydrogen peroxide (H2O2) can be still achieved after the electrospun core-shell MWCNTs/gelatin-Hb nanobelts adsorbed protein. Moreover, compared with before protein adsorption (Kmapp =0.0155 mmol/L), the electrospun core-shell MWCNTs/gelatin-Hb nanobelts after protein adsorption still displayed high biological affinity to H2O2 (Kmapp =0.0382 mmol/L). The constructed H2O2 biosensor by using the electrospun core-shell MWCNTs/gelatin-Hb nanobelts showed high sensitivity, great reproducibility and stability after protein adsorption. This study provides a novel design and an effective platform for the development of implantable electrochemical biosensors.

Preparation of a gel-type microbial-missile for biodegradation of oil pollution

The removal of oil spill pollution is a global problem. In order to solve the problem of low biodegradation efficiency, a series of microbial-missile materials with high floatability, hydrophobicity and biological affinity were prepared to enhance the degradation of oil spill. Hydrophobic macroporous materials with polar groups inside and hydrophobic aliphatic polyester outside were prepared by physical and chemical methods using SA/PVA as substrate for gel-type microbial-missile. The experimental results show that the saturated adsorption rate of macroporous gel-type microbial-missile to oil particles is as high as 18.17 g/g, the contact angle is 149.300°, the average density is 0.5883 g/cm3, the average mechanical strength is 2.52 mN, the penetration rate of 40 s is 82.72%, and the degradation rate of crude oil in 7 days is 88.95%.

Preparation of metal phthalocyanine (MPc)–polymer complexes: the possible anti-cancer properties of FePc–polymer complexes

We have succeeded in preparing various water-soluble metal phthalocyanine (MPc)–polymer complexes, wherein the metal moiety is lithium, iron, cobalt, copper, zinc, or tin, and the polymer is one of the following water-soluble polymers: polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), or polyvinyl alcohol (PVA). Among all MPc–polymer complexes, the iron phthalocyanine (FePc)–PVP complex in water showed the largest and sharpest absorption peak at ∼700 nm in UV–Vis absorption spectrum, which indicates that FePc–polymer complexes in water are easily prepared and the degree of stacking of FePc in the complexes, very small, such as that of a monomer or a similar structure. Conversely, the polymer chains including those of PEG, PVP, and dextran have high biological affinity as well as flexibility. Speculatively, the FePc–polymer (e.g., PEG, PVP, and dextran) complexes adsorbed onto the surface of a cancer cell might break it via the irradiation of near-infrared light having a wavelength of ∼700 nm. Furthermore, chlorophyll a–polymer complexes, previously prepared by our group, might similarly break a cancer cell because these complexes showed a large and sharp absorption peak at ∼700 nm in UV–Vis spectrum.

CMKLR1-targeting peptide tracers for PET/MR imaging of breast cancer.

Background: Molecular targeting remains to be a promising approach in oncology. Overexpression of G protein-coupled receptors (GPCRs) in human cancer is offering a powerful opportunity for tumor-selective imaging and treatment employing nuclear medicine. We utilized novel chemerin-based peptide conjugates for chemokine-like receptor 1 (CMKLR1) targeting in a breast cancer xenograft model.Methods: By conjugation with the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), we obtained a family of five highly specific, high-affinity tracers for hybrid positron emission tomography/magnetic resonance (PET/MR) imaging. A xenograft model with target-positive DU4475 and negative A549 tumors in immunodeficient nude mice enabled CMKLR1-specific imaging in vivo. We acquired small animal PET/MR images, assessed biodistribution by ex vivo measurements and investigated the tracer specificity by blocking experiments.Results: Five CMKLR1-targeting peptide tracers demonstrated high biological activity and affinity in vitro with EC50 and IC50 values below 2 nM. Our target-positive (DU4475) and target-negative (A549) xenograft model could be validated by ex vivo analysis of CMKLR1 expression and binding. After preliminary PET imaging, the three most promising tracers [68Ga]Ga-DOTA-AHX-CG34, [68Ga]Ga-DOTA-KCap-CG34 and [68Ga]Ga-DOTA-ADX-CG34 with best tumor uptake were further analyzed. Hybrid PET/MR imaging along with concomitant biodistribution studies revealed distinct CMKLR1-specific uptake (5.1% IA/g, 3.3% IA/g and 6.2% IA/g 1 h post-injection) of our targeted tracers in DU4475 tumor tissue. In addition, tumor uptake was blocked by excess of unlabeled peptide (6.4-fold, 5.5-fold and 3.4-fold 1 h post-injection), further confirming CMKLR1 specificity. Out of five tracers, we identified these three tracers with moderate, balanced hydrophilicity to be the most potent in receptor-mediated tumor targeting.Conclusion: We demonstrated the applicability of 68Ga-labeled peptide tracers by visualizing CMKLR1-positive breast cancer xenografts in PET/MR imaging, paving the way for developing them into theranostics for tumor treatment.

Cholestane-3β, 5α, 6β-triol suppresses neuronal hyperexcitability via binding to voltage-gated sodium channels

Neuronal hyperexcitability is identified as a critical pathological basis of epileptic seizures. Cholestane-3β, 5α, 6β-triol (Triol) is a major metabolic oxysterol of cholesterol. Although its neuroprotective effect on ischemia-induced neuronal injury and negative modulation of voltage-gated sodium (Nav) channels were well established, the physical binding site of triol to sodium channels and its effects on neuronal hyperexcitability have not yet been explored. In this study, we utilized molecular docking and molecular dynamics simulation to investigate the interaction between triol and Nav Channels. Our results demonstrated that triol binds to the indole ring of Trp122 of the Nav Channel in silico with a high biological affinity. We further found that triol negatively modulates the action potentials bursts of hippocampal neurons by cell-attached patch recording. Moreover, triol significantly inhibits low Mg2+-induced hyperexcitability in vitro. In addition, triol attenuates pentylenetetrazole (PTZ)-induced convulsive-form behavioral deficits in vivo. Together, our results suggest that triol suppresses neuronal hyperexcitability via binding to Nav channel, indicating that triol might be an attractive lead compound for the treatment of neuronal hyperexcitability-related neurological disorders, especially epileptic seizures.

Orbital Floor Reconstruction Using a Dynamic Titanium Mesh Following a Total Maxillectomy

When a total maxillectomy is performed in patients with maxillary cancer, it is important to preserve visual function and maintain the patient’s facial features, since both orbital floors are removed. Various reconstruction methods have been reported. We have performed reconstructions of the orbital floor using a dynamic titanium mesh. The results have been satisfactory in terms of function and cosmetic appearance, since neither diplopia nor infectious symptoms have been observed and minimal post-surgical cheek deformation has occurred. The prosthesis were prepared so as to cover the resected area of the hard palate. The removal of the prosthesis facilitated observations of the cavity. Also, the presence or absence of recurrences and the condition of the reconstruction site could be assessed visually. The titanium mesh that was employed was useful for preserving postoperative visual function, since it has a high biological affinity and can be easily used to replicate the 3D structure of the orbital floors. Compared with a vascularized composite-free tissue transfer, surgery using this mesh requires only a short operative time and the sacrifice of fewer autografts. In contrast to bone grafting, the restoration of ocular alignment is possible, since the mesh can easily replicate the 3D structure of the orbital floors. The mesh, however, may be exposed on the surface of the skin or cause infection if used over a wide area extending to the zygomatic bones, since it is an artificial material. It is important to take the area of reconstruction into consideration when using this mesh, as in the present cases. Here, we report three postoperative cases with follow-up periods of more than 5 years. A lengthy and meticulous follow-up period is necessary for such cases.

EGAR, A Food Protein-Derived Tetrapeptide, Reduces Seizure Activity in Pentylenetetrazole-Induced Epilepsy Models Through α-Amino-3-Hydroxy-5-Methyl-4-Isoxazole Propionate Receptors.

A primary pathogeny of epilepsy is excessive activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPARs). To find potential molecules to inhibit AMPARs, high-throughput screening was performed in a library of tetrapeptides in silico. Computational results suggest that some tetrapeptides bind stably to the AMPAR. We aligned these sequences of tetrapeptide candidates with those from in vitro digestion of the trout skin protein. Among salmon-derived products, Glu-Gly-Ala-Arg (EGAR) showed a high biological affinity toward AMPAR when tested in silico. Accordingly, natural EGAR was hypothesized to have anticonvulsant activity, and in vitro experiments showed that EGAR selectively inhibited AMPAR-mediated synaptic transmission without affecting the electrophysiological properties of hippocampal pyramidal neurons. In addition, EGAR reduced neuronal spiking in an in vitro seizure model. Moreover, the ability of EGAR to reduce seizures was evaluated in a rodent epilepsy model. Briefer and less severe seizures versus controls were shown after mice were treated with EGAR. In conclusion, the promising experimental results suggest that EGAR inhibitor against AMPARs may be a target for antiepilepsy pharmaceuticals. Epilepsy is a common brain disorder characterized by the occurrence of recurring, unprovoked seizures. Twenty to 30% of persons with epilepsy do not achieve adequate seizure control with any drug. Here we provide a possibility in which a natural and edible tetrapeptide, EGAR, can act as an antiepileptic agent. We have combined computation with in vitro experiments to show how EGAR modulates epilepsy. We also used an animal model of epilepsy to prove that EGAR can inhibit seizures in vivo. This study suggests EGAR as a potential pharmaceutical for the treatment of epilepsy.

Combinatorial Library Screening Coupled to Mass Spectrometry to Identify Valuable Cyclic Peptides

Combinatorial library screening coupled to mass spectrometry (MS) analysis is a practical approach to identify useful peptides. Cyclic peptides can have high biological activity, selectivity, and affinity for target proteins, and high stability against proteolytic degradation. Here we describe two strategies to prepare combinatorial libraries suitable for MS analysis to accelerate the discovery of cyclic peptide structures. Both approaches use ChemMatrix resin and the linker 4-hydroxymethylbenzoic acid. One strategy involves the synthesis of a one-bead-two-peptides library in which each bead contains both the cyclic peptide and its linear counterpart to facilitate MS analysis. The other protocol is based on the synthesis of a cyclic depsipeptide library in which a glycolamidic ester group is incorporated by adding glycolic acid. After library screening, the ring is opened and the peptide is released simultaneously for subsequent MS analysis. © 2016 by John Wiley & Sons, Inc.

Mesoporous carbon-containing voltammetric biosensor for determination of tyramine in food products.

A voltammetric biosensor based on tyrosinase (TYR) was developed for determination of tyramine. Carbon material (multi-walled carbon nanotubes or mesoporous carbon CMK-3-type), polycationic polymer—i.e., poly(diallyldimethylammonium chloride) (PDDA), and Nafion were incorporated into titania dioxide sol (TiO2) to create an immobilization matrix. The features of the formed matrix were studied by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The analytical performance of the developed biosensor was evaluated with respect to linear range, sensitivity, limit of detection, long-term stability, repeatability, and reproducibility. The biosensor exhibited electrocatalytic activity toward tyramine oxidation within a linear range from 6 to 130 μM, high sensitivity of 486 μA mM−1 cm−2, and limit of detection of 1.5 μM. The apparent Michaelis–Menten constant was calculated to be 66.0 μM indicating a high biological affinity of the developed biosensor for tyramine. Furthermore, its usefulness in determination of tyramine in food product samples was also verified.Graphical abstractDifferent food samples were analyzed to determine tyramine using biosensor based on tyrosinaseElectronic supplementary materialThe online version of this article (doi:10.1007/s00216-016-9612-y) contains supplementary material, which is available to authorized users.

Immobilization of collagen on hydroxyapatite discs by covalent bonding and physical adsorption and their interaction with MC3T3-E1 osteoblasts

Hydroxyapatite (HA), a type of calcium phosphate mineral, shows high biological affinity to living bone and is widely used as a substitute for filling bone defects. The purpose of this study was to immobilize collagen on HA discs via covalent bonding and physical adsorption and to evaluate their interaction with MC3T3-E1 osteoblasts. Type I collagen was immobilized on the surface of sintered HA discs in two ways. The first way was to immobilize collagen covalently on the surface of a HA disc (HA-C) through a coupling agent, 3-aminopropyltriethoxysilane. The second one was to immobilize collagen on the surface of a HA disc in the manner of physical adsorption (HAhC). The surface properties of HA immobilized with collagen were characterized and compared with non-immobilized HA (control). The potentiality of collagen-immobilized HA discs for use as bone substitutes or scaffolds were assessed by culturing MC3T3-E1 osteoblasts on the discs. The osteoblasts were cultured for 4 and 68 h on HA discs to examine cell adhesion and proliferation, respectively. Alkaline phosphatase (ALP) activity assay was used to study the in vitro differentiation of MC3T3-E1 osteoblasts when cultured on the modified HA discs. From the results, it was apparent that the osteoblasts had proliferated more on the HA-C disc than on the HA-hC disc. The better proliferation was probably attributed to the higher amount of collagen covalently immobilized than that immobilized by physical adsorption. It was found, from the ALP activity assay, that HA-C showed better osteoblastic differentiation than HA-hC. It was considered that the higher ALP activity of HA-C was mainly expressed by the larger amount of collagen immobilized on the HA surface.

미생물연료전지의 성능향상을 위한 하이드로젤 및 다중벽 탄소나노튜브를 이용한 산화전극의 표면개질

The surface of graphite fiber fabric anode was modified with a hydrogel and a mixture of hydrogel and multiwall carbon nanotube, and their effectiveness were compared to the unmodified anodes in a batch microbial fuel cell (microbial fuel cells). The maximum power density of the MFC was determined by both performance of the anode and cathode. The maximum power density for the MFC with the anode modified with the mixture of hydrogel and multiwall carbon nanotube was 1,162 mW/m which was 27.7% higher than that with the unmodified graphite fiber fabric anode. “The mixture of hydrogel and multiwall carbon nanotube is a good surface modifier for anode with high biological affinity and low activation losses.”