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Biosensors, Volume 10, Issue 1 (January 2020) – 7 articles

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Cover Story (view full-size image) Graphene is a one-atom-thick, two-dimensional, honey-comb arrangement of hybridized carbon atoms [...] Read more.
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Open AccessArticle
Disturbing-Free Determination of Yeast Concentration in DI Water and in Glucose Using Impedance Biochips
Biosensors 2020, 10(1), 7; https://doi.org/10.3390/bios10010007 - 19 Jan 2020
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Abstract
Deionized water and glucose without yeast and with yeast (Saccharomyces cerevisiae) of optical density OD600 that ranges from 4 to 16 has been put in the ring electrode region of six different types of impedance biochips and impedance has been [...] Read more.
Deionized water and glucose without yeast and with yeast (Saccharomyces cerevisiae) of optical density OD600 that ranges from 4 to 16 has been put in the ring electrode region of six different types of impedance biochips and impedance has been measured in dependence on the added volume (20, 21, 22, 23, 24, 25 µL). The measured impedance of two out of the six types of biochips is strongly sensitive to the addition of both liquid without yeast and liquid with yeast and modelled impedance reveals a linear relationship between the impedance model parameters and yeast concentration. The presented biochips allow for continuous impedance measurements without interrupting the cultivation of the yeast. A multiparameter fit of the impedance model parameters allows for determining the concentration of yeast (cy) in the range from cy = 3.3 × 107 to cy = 17 × 107 cells/mL. This work shows that independent on the liquid, i.e., DI water or glucose, the impedance model parameters of the two most sensitive types of biochips with liquid without yeast and with liquid with yeast are clearly distinguishable for the two most sensitive types of biochips. Full article
(This article belongs to the Special Issue Electrochemical (Bio)sensors for Environmental and Food Analyses II)
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Open AccessArticle
High-Yield Production of Aqueous Graphene for Electrohydrodynamic Drop-on-Demand Printing of Biocompatible Conductive Patterns
Biosensors 2020, 10(1), 6; https://doi.org/10.3390/bios10010006 - 17 Jan 2020
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Abstract
Presented here is a scalable and aqueous phase exfoliation of graphite to high yield and quality of few layer graphene (FLG) using Bovine Serum Albomine (BSA) and wet ball milling. The produced graphene ink is tailored for printable and flexible electronics, having shown [...] Read more.
Presented here is a scalable and aqueous phase exfoliation of graphite to high yield and quality of few layer graphene (FLG) using Bovine Serum Albomine (BSA) and wet ball milling. The produced graphene ink is tailored for printable and flexible electronics, having shown promising results in terms of electrical conductivity and temporal stability. Shear force generated by steel balls which resulted in 2–3 layer defect-free graphene platelets with an average size of hundreds of nm, and with a concentration of about 5.1 mg/mL characterized by Raman spectroscopy, atomic force microscopy (AFM), transmittance electron microscopy (TEM) and UV-vis spectroscopy. Further, a conductive ink was prepared and printed on flexible substrate (Polyimide) with controlled resolution. Scanning electron microscopy (SEM) and Profilometry revealed the effect of thermal annealing on the prints to concede consistent morphological characteristics. The resulted sheet resistance was measured to be R s   =   36.75   Ω / sqr for prints as long as 100 mm. Printable inks were produced in volumes ranging from 20 mL to 1 L, with potential to facilitate large scale production of graphene for applications in biosensors, as well as flexible and printable electronics. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Biosensors in 2019
Biosensors 2020, 10(1), 5; https://doi.org/10.3390/bios10010005 - 16 Jan 2020
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Abstract
The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal’s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not [...] Full article
Open AccessFeature PaperReview
Grafting of Diazonium Salts on Surfaces: Application to Biosensors
Biosensors 2020, 10(1), 4; https://doi.org/10.3390/bios10010004 - 15 Jan 2020
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Abstract
This review is divided into two parts; the first one summarizes the main features of surface modification by diazonium salts with a focus on most recent advances, while the second part deals with diazonium-based biosensors including small molecules of biological interest, proteins, and [...] Read more.
This review is divided into two parts; the first one summarizes the main features of surface modification by diazonium salts with a focus on most recent advances, while the second part deals with diazonium-based biosensors including small molecules of biological interest, proteins, and nucleic acids. Full article
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Open AccessArticle
Fabrication, Characterization and Application of Biomolecule Micropatterns on Cyclic Olefin Polymer (COP) Surfaces with Adjustable Contrast
Biosensors 2020, 10(1), 3; https://doi.org/10.3390/bios10010003 - 28 Dec 2019
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Abstract
Peptide and protein micropatterns are powerful tools for the investigation of various cellular processes, including protein–protein interactions (PPIs). Within recent years, various approaches for the production of functional surfaces have been developed. Most of these systems use glass as a substrate, which has [...] Read more.
Peptide and protein micropatterns are powerful tools for the investigation of various cellular processes, including protein–protein interactions (PPIs). Within recent years, various approaches for the production of functional surfaces have been developed. Most of these systems use glass as a substrate, which has several drawbacks, including high fragility and costs, especially if implemented for fluorescence microscopy. In addition, conventional fabrication technologies such as microcontact printing (µCP) are frequently used for the transfer of biomolecules to the glass surface. In this case, it is challenging to adjust the biomolecule density. Here, we show that cyclic olefin polymer (COP) foils, with their encouraging properties, including the ease of manufacturing, chemical resistance, biocompatibility, low water absorption, and optical clarity, are a promising alternative to glass substrates for the fabrication of micropatterns. Using a photolithography-based approach, we generated streptavidin/biotinylated antibody patterns on COPs with the possibility of adjusting the pattern contrast by varying plasma activation parameters. Our experimental setup was finally successfully implemented for the analysis of PPIs in the membranes of live cells via total internal reflection fluorescence (TIRF) microscopy. Full article
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Open AccessReview
Nanomaterials for Biosensing Lipopolysaccharide
Biosensors 2020, 10(1), 2; https://doi.org/10.3390/bios10010002 - 21 Dec 2019
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Abstract
Lipopolysaccharides (LPS) are endotoxins, hazardous and toxic inflammatory stimulators released from the outer membrane of Gram-negative bacteria, and are the major cause of septic shock giving rise to millions of fatal illnesses worldwide. There is an urgent need to identify and detect these [...] Read more.
Lipopolysaccharides (LPS) are endotoxins, hazardous and toxic inflammatory stimulators released from the outer membrane of Gram-negative bacteria, and are the major cause of septic shock giving rise to millions of fatal illnesses worldwide. There is an urgent need to identify and detect these molecules selectively and rapidly. Pathogen detection has been done by traditional as well as biosensor-based methods. Nanomaterial based biosensors can assist in achieving these goals and have tremendous potential. The biosensing techniques developed are low-cost, easy to operate, and give a fast response. Due to extremely small size, large surface area, and scope for surface modification, nanomaterials have been used to target various biomolecules, including LPS. The sensing mechanism can be quite complex and involves the transformation of chemical interactions into amplified physical signals. Many different sorts of nanomaterials such as metal nanomaterials, magnetic nanomaterials, quantum dots, and others have been used for biosensing of LPS and have shown attractive results. This review considers the recent developments in the application of nanomaterials in sensing of LPS with emphasis given mainly to electrochemical and optical sensing. Full article
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Open AccessArticle
Complexity Measures of Voice Recordings as a Discriminative Tool for Parkinson’s Disease
Biosensors 2020, 10(1), 1; https://doi.org/10.3390/bios10010001 - 20 Dec 2019
Viewed by 753
Abstract
In this paper, we have investigated the differences in the voices of Parkinson’s disease (PD) and age-matched control (CO) subjects when uttering three phonemes using two complexity measures: fractal dimension (FD) and normalised mutual information (NMI). Three sustained phonetic voice recordings, /a/, /u/ [...] Read more.
In this paper, we have investigated the differences in the voices of Parkinson’s disease (PD) and age-matched control (CO) subjects when uttering three phonemes using two complexity measures: fractal dimension (FD) and normalised mutual information (NMI). Three sustained phonetic voice recordings, /a/, /u/ and /m/, from 22 CO (mean age = 66.91) and 24 PD (mean age = 71.83) participants were analysed. FD was first computed for PD and CO voice recordings, followed by the computation of NMI between the test groups: PD–CO, PD–PD and CO–CO. Four features reported in the literature—normalised pitch period entropy (Norm. PPE), glottal-to-noise excitation ratio (GNE), detrended fluctuation analysis (DFA) and glottal closing quotient (ClQ)—were also computed for comparison with the proposed complexity measures. The statistical significance of the features was tested using a one-way ANOVA test. Support vector machine (SVM) with a linear kernel was used to classify the test groups, using a leave-one-out validation method. The results showed that PD voice recordings had lower FD compared to CO (p < 0.008). It was also observed that the average NMI between CO voice recordings was significantly lower compared with the CO–PD and PD–PD groups (p < 0.036) for the three phonetic sounds. The average NMI and FD demonstrated higher accuracy (>80%) in differentiating the test groups compared with other speech feature-based classifications. This study has demonstrated that the voices of PD patients has reduced FD, and NMI between voice recordings of PD–CO and PD–PD is higher compared with CO–CO. This suggests that the use of NMI obtained from the sample voice, when paired with known groups of CO and PD, can be used to identify PD voices. These findings could have applications for population screening. Full article
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