Distance-Independent Contactless Interrogation of Quartz Resonator Sensor with Printed-on-Crystal Coil

A novel quartz crystal resonator sensor, which embeds a conductive printed planar coil that enables electromagnetic contactless interrogation techniques is presented. An aerosol-jet process is used to precisely and accurately deposit electronic inks onto a 330 µm-thick bare piezoelectric quartz crystal to print the planar coil and the electrodes. The proposed interrogation technique enables distance-independent operation, and is based on the measurement of the reflected impedance of the quartz resonator sensor through the planar primary coil of the coupled inductors. The resonant frequency, measured without contact using the primary coil connected to an impedance analyzer, results 4.790260 MHz. Contactless operation distances up to 12.2 mm have been obtained. The experimental results have a maximum deviation of about 50 Hz, i.e. 10.5 ppm, with respect to reference measurements taken via contact probes

Distance-Independent Contactless Interrogation of Quartz Resonator Sensor with Printed-on-Crystal Coil

A novel quartz crystal resonator sensor, which embeds a conductive printed planar coil that enables electromagnetic contactless interrogation techniques is presented. An aerosol-jet process is used to precisely and accurately deposit electronic inks onto a 330 µm-thick bare piezoelectric quartz crystal to print the planar coil and the electrodes. The proposed interrogation technique enables distance-independent operation, and is based on the measurement of the reflected impedance of the quartz resonator sensor through the planar primary coil of the coupled inductors. The resonant frequency, measured without contact using the primary coil connected to an impedance analyzer, results 4.790260 MHz. Contactless operation distances up to 12.2 mm have been obtained. The experimental results have a maximum deviation of about 50 Hz, i.e. 10.5 ppm, with respect to reference measurements taken via contact probes

Separation of supercoiled from open circular forms of plasmid DNA, and biological activity detection

To establish a cost-effective purification process for the large-scale production of plasmid DNA for gene therapy and DNA vaccination, a single anion-exchange chromatography (AEC) step was employed to purify supercoiled plasmid DNA (sc pDNA) from other isoforms and Escherichia coli impurities present in a clarified lysate. Two different size and conformation plasmids were used as model targets, and showed similar elution behavior in this chromatographic operation, in which sc pDNA was effectively separated from open circle plasmid DNA (oc pDNA) in a salt gradient. The process delivered high-purity pDNA of homogeneity of 95 ± 1.1% and almost undetectable levels of endotoxins, genomic DNA, RNA and protein, at a yield of 65 ± 8%. Furthermore, the transfection efficiency (29 ± 0.4%) was significantly higher than that (20 ± 0.1%) of a pDNA control. The present study confirms the possibility of using a single AEC step to purify sc pDNA from other isoforms and host contaminants present in a clarified E. coli lysate

Dextran-based Hydrogel Layers for Biosensors

Biofunctional coatings are key elements of biosensors regulating interactions between the sensing surface and analytes as well as matrix components of the sample. These coatings can improve sensing capabilities both by amplifying the target signal and attenuating interfering signals originating from surface fouling (non-specific binding). Considering the tested materials so far, hydrogel-based layers have been verified to be among the most effective layers in improving biochip performance. The polysaccharide dextran can be efficiently used to form hydrogel layers displaying extended three-dimensional structure on biosensor surfaces. Owing to their high water content and flexible structure, dextran coatings present advanced antifouling abilities, which can be exploited in classic bioanalytical measurements as well as in the development of cell-on-a-chip type biosensors. However, in spite of the numerous applications, the deep characterization of dextran layers has been missing from the literature. This phenomenon can be attributed to the challenging analysis of few nanometer-thick layers with high water content. The lack of available data is more pronounced regarding the layer behaviors under aqueous conditions. In this chapter we present various surface analytical methods (including biosensor-type techniques) suitable for the complex characterization of hydrogel coatings whose thickness ranges from few to several ten nanometers. As a case study, we focus on the analysis of carboxymethyl dextran (CMD) layers developed for waveguide-based label-free optical biosensor applications. Examination methodologies both under dry and aqueous conditions as well as testing of antifouling abilities are also presented

Engineering of bacterial strains and vectors for the production of plasmid DNA

The demand for plasmid DNA (pDNA) is anticipated to increase significantly as DNA vaccines and non-viral gene therapies enter phase 3 clinical trials and are approved for use. This increased demand, along with renewed interest in pDNA as a therapeutic vector, has motivated research targeting the design of high-yield, cost-effective manufacturing processes. An important aspect of this research is engineering bacterial strains and plasmids that are specifically suited to the production of plasmid biopharmaceuticals. This review will survey recent innovations in strain and vector engineering that aim to improve plasmid stability, enhance product safety, increase yield, and facilitate downstream purification. While these innovations all seek to enhance pDNA production, they can vary in complexity from subtle alterations of the host genome or vector backbone to the investigation of non-traditional host strains for higher pDNA yields