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Dias T.M.,INESC MN Microsystems and Nanotechnologies | Dias T.M.,IBB Institute for Biotechnology And Bioengineering | Cardoso F.A.,INESC MN Microsystems and Nanotechnologies | Martins S.A.M.,INESC MN Microsystems and Nanotechnologies | And 5 more authors.
Analytical Methods | Year: 2016

Cell-free DNA (cfDNA) is foreseen as a promising source for liquid biopsies in cancer diagnostics. Despite its promise, methods available for its evaluation lack in robustness or, in the case of next-generation sequencing (NGS), are extremely sensitive but overly complex for routine operation. In contrast to NGS, integrated lab-on-chip devices offer advantages particularly in terms of automation, cost and speed. These devices, however, have rarely demonstrated the detection of biologically relevant DNA fragments originating from blood. To this end, we present a strategy for the magnetic labeling and detection of cfDNA fragments, using an array of 30 magnetoresistive (MR) sensors integrated in a portable biochip platform. As a proof-of-concept, we selected the fragments ALU115 and ALU247, recently identified as promising cancer targets in cfDNA integrity assessment. This work reveals a rational optimization of the DNA probes design and density at the surface which allowed achieving specific target detection and increased inhibition of unspecific interactions, without the need for blocking agents. The developed strategy is adaptable for the detection of mutations, homologous or truncated sequences such as the case of ALU115 and ALU247, sequences that share great similarity. Upon optimization, the MR sensors detected a concentration of the ALU elements within the picomolar range, showing potential for cfDNA analysis in cancer diagnostics. © The Royal Society of Chemistry 2016.

Jolly P.,University of Bath | Damborsky P.,Slovak Academy of Sciences | Madaboosi N.,INESC MN Microsystems and Nanotechnologies | Soares R.R.G.,INESC MN Microsystems and Nanotechnologies | And 6 more authors.
Biosensors and Bioelectronics | Year: 2016

Two novel sandwich-based immunoassays for prostate cancer (PCa) diagnosis are reported, in which the primary antibody for capture is replaced by a DNA aptamer. The assays, which can be performed in parallel, were developed in a microfluidic device and tested for the detection of free Prostate Specific Antigen (fPSA). A secondary antibody (Aptamer-Antibody Assay) or a lectin (Aptamer-Lectin Assay) is used to quantify, by chemiluminescence, both the amount of fPSA and its glycosylation levels. The use of aptamers enables a more reliable, selective and controlled sensing of the analyte. The dual approach provides sensitive detection of fPSA along with selective fPSA glycoprofiling, which is of significant importance in the diagnosis and prognosis of PCa, as tumor progression is associated with changes in fPSA glycosylation. With these approaches, we can potentially detect 0.5. ng/mL of fPSA and 3. ng/mL of glycosylated fPSA using Sambucus nigra (SNA) lectin, both within the relevant clinical range. The approach can be applied to a wide range of biomarkers, thus providing a good alternative to standard antibody-based immunoassays with significant impact in medical diagnosis and prognosis. © 2015 Elsevier B.V.

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