Biomimetic Bacterial Identification Platform Based on Thermal Wave Transport Analysis (TWTA) through Surface-Imprinted Polymers

This paper introduces a novel bacterial identification assay based on thermal wave analysis through surfaceimprinted polymers (SIPs). Aluminum chips are coated with SIPs, serving as synthetic cell receptors that have been combined previously with the heat-transfer method (HTM) for the selective detection of bacteria. In this work, the concept of bacterial identification is extended toward the detection of nine different bacterial species. In addition, a novel sensing approach, thermal wave transport analysis (TWTA), is introduced, which analyzes the propagation of a thermal wave through a functional interface. The results presented here demonstrate that bacterial rebinding to the SIP layer resulted in a measurable phase shift in the propagated wave, which is most pronounced at a frequency of 0.03 Hz. In this way, the sensor is able to selectively distinguish between the different bacterial species used in this study. Furthermore, a dose−response curve was constructed to determine a limit of detection of 1 × 104 CFU mL−1 , indicating that TWTA is advantageous over HTM in terms of sensitivity and response time. Additionally, the limit of selectivity of the sensor was tested in a mixed bacterial solution, containing the target species in the presence of a 99-fold excess of competitor species. Finally, a first application for the sensor in terms of infection diagnosis is presented, revealing that the platform is able to detect bacteria in clinically relevant concentrations as low as 3 × 104 CFU mL−1 in spiked urine samples

A Novel Biomimetic Tool for Assessing Vitamin K Status Based on Molecularly Imprinted Polymers

Vitamin K was originally discovered as a cofactor required to activate clotting factors and has recently been shown to play a key role in the regulation of soft tissue calcification. This property of vitamin K has led to an increased interest in novel methods for accurate vitamin K detection. Molecularly Imprinted Polymers (MIPs) could offer a solution, as they have been used as synthetic receptors in a large variety of biomimetic sensors for the detection of similar molecules over the past few decades, because of their robust nature and remarkable selectivity. In this article, the authors introduce a novel imprinting approach to create a MIP that is able to selectively rebind vitamin K 1. As the native structure of the vitamin does not allow for imprinting, an alternative imprinting strategy was developed, using the synthetic compound menadione (vitamin K 3) as a template. Target rebinding was analyzed by means of UV-visible (UV-VIS) spectroscopy and two custom-made thermal readout techniques. This analysis reveals that the MIP-based sensor reacts to an increasing concentration of both menadione and vitamin K 1. The Limit of Detection (LoD) for both compounds was established at 700 nM for the Heat Transfer Method (HTM), while the optimized readout approach, Thermal Wave Transport Analysis (TWTA), displayed an increased sensitivity with a LoD of 200 nM. The sensor seems to react to a lesser extent to Vitamin E, the analogue under study. To further demonstrate its potential application in biochemical research, the sensor was used to measure the absorption of vitamin K in blood serum after taking vitamin K supplements. By employing a gradual enrichment strategy, the sensor was able to detect the difference between baseline and peak absorption samples and was able to quantify the vitamin K concentration in good agreement with a validation experiment using High-Performance Liquid Chromatography (HPLC). In this way, the authors provide a first proof of principle for a low-cost, straightforward, and label-free vitamin K sensor

Real-time analysis of microbial growth by means of the Heat-Transfer Method (HTM) using Saccharomyces cerevisiae as model organism

In this manuscript, we explore the use of the Heat-Transfer Method (HTM) for the real-time analysis of microbial growth using Saccharomyces cerevisiae as a model organism. The thermal responses of gold electrodes upon exposure to suspensions of S. cerevisiae (wild type strain DLY640) concentrations were monitored, demonstrating an increase in thermal resistance at the solid-liquid interface with higher concentrations of the microorganism. Flow cells were manufactured using 3D-printing to facilitate longitudinal experiments. We can clearly discriminate between the growth of S. cerevisiae under optimal conditions and under the influence of factors that inhibit the replication process, such as the use of nutrient depleted growth medium, elevated temperature, and the presence of toxic compounds. In addition, it is possible to determine the kinetics of the growth process and quantify yeast replication which was demonstrated by measuring a mutant temperature sensitive strain. This is the first time HTM has been used for the real-time determination of factors that impact microbial growth. Thermal sensing is low-cost, offers straightforward analysis and measurements can be performed on-site. Due to the versatility of this method, this platform can be extended to monitor other microorganisms and in particular to study the response of bacteria to selected antibiotics

Label-Free Detection of Escherichia coli Based on Thermal Transport through Surface Imprinted Polymers

This work focuses on the development of a label-free biomimetic sensor for the specific and selective detection of bacteria. The platform relies on the rebinding of bacteria to synthetic cell receptors, made by surface imprinting of polyurethane-coated aluminum chips. The heat-transfer resistance (Rth) of these so-called surface imprinted polymers (SIPs) was analyzed in time using the heat-transfer method (HTM). Rebinding of target bacteria to the synthetic receptor led to a measurable increase in thermal resistance at the solid–liquid interface. Escherichia coli and Staphylococcus aureus were used as model organisms for several proof-of-principle experiments, demonstrating the potential of the proposed platform for point-of-care bacterial testing. The results of these experiments indicate that the sensor is able to selectively detect bacterial rebinding to the SIP surface, distinguishing between dead and living E. coli cells on one hand and between Gram-positive and Gram-negative bacteria on the other hand (E. coli and S. aureus). In addition, the sensor was capable of quantifying the number of bacteria in a given sample, enabling detection at relatively low concentrations (104 CFU mL–1 range). As a first proof-of-application, the sensor was exposed to a mixed bacterial solution containing only a small amount (1%) of the target bacteria. The sample was able to detect this trace amount by using a simple gradual enrichment strategy

Evaluatie van de nota Duurzame gewasbescherming

Dankzij wetgeving voor gewasbescherming is de waterkwaliteit vooruit gegaan, al zijn de beleidsdoelen voor de ecologische kwaliteit van het oppervlaktewater en voor de drinkwaterwinning niet bereikt. Ook bevat het oppervlaktewater op de helft van de meetlocaties nog te veel gewasbeschermingsmiddel. Wel zijn de beleidsdoelen voor voedselveiligheid en economie gehaald. De meeste zorg zit bij arbeidsveiligheid, vooral in de tuinbouw

Fingerprints for Structural Defects in Poly(thienylene vinylene) (PTV): A Joint Theoretical–Experimental NMR Study on Model Molecules

In the field of plastic electronics, low band gap conjugated polymers like poly(thienylene vinylene) (PTV) and its derivatives are a promising class of materials that can be obtained with high molecular weight via the so-called dithiocarbamate precursor route. We have performed a joint experimental- theoretical study of the full NMR chemical shift assignment in a series of thiophene-based model compounds, which aims at (i) benchmarking the quantum-chemical calculations against experiments, (ii) identifying the signature of possible structural defects that can appear during the polymerization of PTV's, namely head-to-head and tail-to-tail defects, and (iii) defining a criterion regarding regioregularity

Label-free protein detection based on the heat-transfer method-a case study with the peanut allergen Ara h 1 and aptamer-based synthetic receptors

© 2015 American Chemical Society. Aptamers are an emerging class of molecules that, because of the development of the systematic evolution of ligands by exponential enrichment (SELEX) process, can recognize virtually every target ranging from ions, to proteins, and even whole cells. Although there are many techniques capable of detecting template molecules with aptamer-based systems with high specificity and selectivity, they lack the possibility of integrating them into a compact and portable biosensor setup. Therefore, we will present the heat-transfer method (HTM) as an interesting alternative because this offers detection in a fast and low-cost manner and has the possibility of performing experiments with a fully integrated device. This concept has been demonstrated for a variety of applications including DNA mutation analysis and screening of cancer cells. To the best our knowledge, this is the first report on HTM-based detection of proteins, in this case specifically with aptamer-type receptors. For proof-of-principle purposes, measurements will be performed with the peanut allergen Ara h 1 and results indicate detection limits in the lower nanomolar regime in buffer liquid. As a first proof-of-application, spiked Ara h 1 solutions will be studied in a food matrix of dissolved peanut butter. Reference experiments with the quartz-crystal microbalance will allow for an estimate of the areal density of aptamer molecules on the sensor-chip surface

Kalibratie van het Landelijk KRW-Verkenner Model 2.0

Bij de laatste validatie van het Landelijk KRW-Verkenner Model (Cleij et al. 2014) is gebleken dat de concentraties voor N-totaal en P-totaal vaak matig tot slecht voorspeld worden. Eén van de manieren om de voorspellende waarde van een model te verhogen is kalibratie. Het LKM is echter modelparameter-arm, en de enige 'knoppen', waaraan wat betreft modelparameters gedraaid kan worden zijn de parameters van het eerste-orde afbraak proces voor -totaal en -totaal de a raakconstante ij en de temperatuurco ici nt De tot nu toe gebruikte retentieparameters zijn afkomstig van een vertaling van de retentieparameters van het KRW-ECHO systeem naar de retentieparameters voor de KRWVerkenner (Roovaart et al. 2012). Het in dit rapport beschreven onderzoek is via kalibratie gezocht naar een nieuwe set retentieparameters voor N-totaal en P-totaal, uitgaande van de tot nu toe gehanteerde parameterwaarden met als doel het voorspellend vermogen van het LKM op dit punt te verbeteren

The quality of drinking water in the Netherlands in 1998

Order at the ministry of VROM<br>Het rapport is gebaseerd op de resultaten van de monitoringsprogramma's over 1998, die de waterleidingbedrijven uitvoeren ter controle van de drinkwaterkwaliteit en de gebruikte grondstof. Deze meetgegevens worden jaarlijks op grond van de Waterleidingwet aan de Regionale Inspecties Milieuhygiene gerapporteerd. Het RIVM heeft de gegevens in samenwerking met de Inspectie Milieuhygiene verwerkt tot een rapport ten behoeve van de Minister, Tweede Kamer, producenten en consumenten van drinkwater. Naar mening van de Inspectie Milieuhygiene blijkt uit de gegevens dat ook voor 1998 de wettelijke voorschriften voor de controle van het drinkwater goed zijn nageleefd. Het aantal pompstations waar in 1998 een normoverschrijding is vastgesteld, is ten opzichte van 1997 toegenomen. Dit aantal varieert in de afgelopen periode (1992-1998) van circa 60 tot 90 pompstations. De normwaarden van de parameters ijzer en mangaan worden het vaakst overschreden. Bij tenminste drie grondwaterpompstations wordt minstens 1 bestrijdingsmiddel structureel in het drinkwater aangetoond. Er vindt onderzoek plaats om dit probleem op de lange termijn op te lossen. De oorzaak is een verontreiniging van de grondstof, in deze gevallen dus het grondwater. De concentratie van de gemeten stoffen in het drinkwater is ten opzichte van voorgaande jaren nauwelijks toe- of afgenomen. Er is geen sprake geweest van een bedreiging van de volksgezondheid. De kwaliteit van het drinkwater is in het algemeen goed. Het voortzetten van een goede en betrouwbare drinkwatervoorziening blijft de voortdurende aandacht vragen van de bedrijfstak en van de overheid. Voor de waarborging van de drinkwaterkwaliteit op de langere termijn is het naar mening van de Inspectie Milieuhygiene noodzakelijk dat het milieubeleid gericht blijft op bescherming van de bronnen.The minister for Housing, Physical Planning and Environment promised to inform The Parlement every year about the quality of the drinking water in the Netherlands. The report " The drinking water quality in the Netherlands in 1998" is based on the informati-on from the Water Supply Companies to the Inspectorates for Public Health and Environmental Protection. Non-compliances of drinking water samples to the drinking water standards are incidentally. Only non-complaince of bacteriological parameters has impact on public health, however there have been no hazardous situations at all. Most cases of non-complaince deal with ethic and easthetic standards. Non-complaince of drinking water standards were solved with adequate measures.HIMHDGM-DVE