Development of electrochemical DNA detection methods to measure circulating tumour DNA for enhanced diagnosis and monitoring cancer

Liquid biopsies are becoming an increasingly important potential replacement for existing biopsy procedures which can be invasive, painful and compromised by tumour heterogeneity. This paper reports a simple electrochemical approach tailored towards point of care cancer detection and treatment monitoring from biofluids using a label free detection strategy. The mutations under test were the KRAS G12D and KRAS G13D mutations which are both important in the development and progression of many human cancers and whose presence correlates with poor outcomes. These common circulating tumour markers were investigated in clinical samples and amplified by standard and specialist PCR methodologies for subsequent electrochemical detection. Following pre-treatment of the sensor to give a clean surface, DNA probes developed specifically for detection of the KRAS G12D and G13D mutations were immobilized onto low cost carbon electrodes using diazonium chemistry and EDC/NHS coupling. Following functionalisation of the sensor it was possible to sensitively and specifically detect mutant KRAS G12D and G13D PCR product from cancer patients against a background of wild type KRAS DNA from the representative sample. Our findings give rise to the basis of a simple and very low cost system for measuring ctDNA biomarkers in patient samples. The current time to result of the system is 4.5 hours with considerable scope for optimisation and already compares favourably to the UK National Health Service biopsy service where patients can wait weeks for their result. The paper will report the technical developments we have made in the production of clean carbon surfaces for functionlisation, show the assay performance data for KRAS G12D and G13D with a range of PCR systems and demonstrate the potential for measuring response to treatment offered by the system

Developing a low-cost, simple-to-use electrochemical sensor for the detection of circulating tumour DNA in human fluids

It is well-known that two major issues, preventing improved outcomes from cancer are late diagnosis and the evolution of drug resistance during chemotherapy, therefore technologies that address these issues can have a transformative effect on healthcare workflows. In this work we present a simple, low-cost DNA biosensor that was developed specifically to detect mutations in a key oncogene (KRAS). The sensor employed was a screen-printed array of carbon electrodes, used to perform parallel measurements of DNA hybridisation. A DNA amplification reaction was developed with primers for mutant and wild type KRAS sequences which amplified target sequences from representative clinical samples to detectable levels in as few as twenty cycles. High levels of sensitivity were demonstrated alongside a clear exemplar of assay specificity by showing the mutant KRAS sequence was detectable against a significant background of wild type DNA following amplification and hybridisation on the sensor surface. The time to result was found to be 3.5 h with considerable potential for optimisation through assay integration. This quick and versatile biosensor has the potential to be deployed in a low-cost, point-of-care test where patients can be screened either for early diagnosis purposes or monitoring of response to therapy

Optimisation of an electrochemical DNA sensor for measuring KRAS G12D and G13D point mutations in different tumour types

Circulating tumour DNA (ctDNA) is widely used in liquid biopsies due to having a presence in the blood that is typically in proportion to the stage of the cancer and because it may present a quick and practical method of capturing tumour heterogeneity. This paper outlines a simple electrochemical technique adapted towards point-of-care cancer detection and treatment monitoring from biofluids using a label-free detection strategy. The mutations used for analysis were the KRAS G12D and G13D mutations, which are both important in the initiation, progression and drug resistance of many human cancers, leading to a high mortality rate. A low-cost DNA sensor was developed to specifically investigate these common circulating tumour markers. Initially, we report on some developments made in carbon surface pre-treatment and the electrochemical detection scheme which ensure the most sensitive measurement technique is employed. Following pre-treatment of the sensor to ensure homogeneity, DNA probes developed specifically for detection of the KRAS G12D and G13D mutations were immobilized onto low-cost screen printed carbon electrodes using diazonium chemistry and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide coupling. Prior to electrochemical detection, the sensor was functionalised with target DNA amplified by standard and specialist PCR methodologies (6.3% increase). Assay development steps and DNA detection experiments were performed using standard voltammetry techniques. Sensitivity (as low as 0.58 ng/μL) and specificity (>300%) was achieved by detecting mutant KRAS G13D PCR amplicons against a background of wild-type KRAS DNA from the representative cancer sample and our findings give rise to the basis of a simple and very low-cost system for measuring ctDNA biomarkers in patient samples. The current time to receive results from the system was 3.5 h with appreciable scope for optimisation, thus far comparing favourably to the UK National Health Service biopsy service where patients can wait for weeks for biopsy results

Molecular characterisation of human pituitary adenylate cyclase activating polypeptide (PACAP) PAC1 receptor null and hop 1 intracellular loop 3 isoforms

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Evaluation of division-arrested cells for cell-based high-throughput screening and profiling.

Just-in-time cell supply for cell-based high-throughput screening (HTS) is frequently problematic. In addition to scheduling and logistical issues, quality issues and variability due to passage effect, cell cycle, or confluency contribute to day-to-day signal variability in the course of cell-based HTS campaigns. Cell division-arrest and cryopreservation technologies permit the use of cells as assay-ready reagents for HTS and other cell-based profiling and structure-activity studies. In this report, the authors compare division-arrested and dividing cells in 2 assay types that are dependent on movement of proteins within or through cell membranes: a receptor tyrosine kinase assay involving A431 cells responsive to epidermal growth factor, and a secretion reporter assay, which measures secretion of a reporter gene, secreted alkaline phosphatase. In both assays, dividing and division-arrested cells yielded similar basal and maximal signals at a given cell density. Similar IC50s were obtained for reference inhibitors in each assay, type in both dividing and division-arrested cells. In addition, for the secretion reporter assay, when comparing IC50s obtained from 44 compounds randomly chosen from a primary screening hit list, the rank order of potency obtained from dividing cells and division-arrested cells was essentially identical. Furthermore, the results show that, under certain assay conditions, data generated using division-arrested cells are less variable than those generated using dividing cells. In summary, the results suggest that, in many cases, division-arrested cells can substitute for dividing cells and offer certain advantages for cell-based assays

Zur Beschreibung der dynamischen Wechselwirkung von Fundamentstrukturen mit dem viskoelastischen Baugrund durch dreidimensionale Randelementformulierungen

SIGLETIB: RN 7563(1990,1) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman