Optical system design for biosensors based on CCD detection

Detection of volatile organic compounds as biomarkers in breath analysis by different analytical techniques

Breath is a rich mixture containing numerous volatile organic compounds at trace amounts (ppbv–pptv level) such as: hydrocarbons, alcohols, ketones, aldehydes, esters or heterocycles. The presence of some of them depends on health status. Therefore, breath analysis might be useful for clinical diagnostics, therapy monitoring and control of metabolic or biochemical cell cycle products. This Review presents an update on the latest developments in breath analysis applied to diagnosing different diseases with the help of high-quality equipment. Efforts were made to fully and accurately describe traditional and modern techniques used to determine the components of breath. The techniques were compared in terms of design, function and also detection limit of different volatile organic compounds. GC with different detectors, MS, optical sensor and laser spectroscopic detection techniques are also discussed.

A portable bioluminescence engineered cell-based biosensor for on-site applications

We have developed a portable biosensing device based on genetically engineered bioluminescent (BL) cells. Cells were immobilized on a 4 × 3 multiwell cartridge using a new biocompatible matrix that preserved their vitality. Using a fiber optic taper, the cartridge was placed in direct contact with a cooled CCD sensor to image and quantify the BL signals. Yeast and bacterial cells were engineered to express recognition elements, whose interaction with the analyte led to luciferase expression, via reporter gene technology. Three different biosensors were developed. The first detects androgenic compounds using yeast cells carrying a green-emitting P. pyralis luciferase regulated by the human androgen receptor and a red mutant of the same species as internal vitality control. The second biosensor detects two classes of compounds (androgens and estrogens) using yeast strains engineered to express green-or red-emitting mutant firefly luciferases in response to androgens or estrogens, respectively. The third biosensor detects lactose analogue isopropyl β-d-1-thiogalactopyranoside using two E. coli strains. One strain exploits the lac operon as recognition element for the expression of P. pyralis luciferase. The other strain serves as a vitality control expressing Gaussia princeps luciferase, which requires a different luciferin substrate. The immobilized cells were stable for up to 1 month. The analytes could be detected at nanomolar levels with good precision and accuracy when the specific signal was corrected using the internal vitality control. This portable device can be used for on-site multiplexed bioassays for different compound classes.

Selective immobilization of oligonucleotide-modified gold nanoparticles by electrodeposition on screen-printed electrodes

Here, we describe a proof of concept procedure for the selective immobilization of oligonucleotides functionalized gold nanoparticle probes (affinity modules) on arrayed screen-printed gold electrodes. Current microarrays are using many different ways to address their DNA probes onto the transducer area. For that reason, we have mixed the electrodeposition of metals, which is a very well known process, in addition with the DNA-gold nanoparticles formation, which is an area of great interest in biosensing applications in the field of genomics, clinical and warfare applications. Combining these fields, we have developed a novel method for the immobilization of gold nanoparticles conjugated with oligonucleotides (affinity modules) onto screenprinting gold electrodes through electrodeposition at a current positive potential of 800mV vs. Ag/AgCl. The modules were selectively immobilized onto the electrode surface being, afterwards, ready for a successful hybridization. The gold colloids take the advantage of being a carrier that allows the immobilization of any kind of bioreceptor in the same conditions and the capability of quality control analysis before the electrodeposition procedure. With this system, we avoided non-specific interactions between the transduction layer and the bioreceptor and in the case of DNA oligonucleotides allowed us the immobilization of multiple sequences in a multimodular device for a further industrial process of cheaper biochip fabrication.