Most methods for the detection of nucleic acids require many reagents and expensive and bulky instrumentation. Here, we report the development and testing of a graphene-based field-effect transistor that uses clustered regularly interspaced short palindromic repeats (CRISPR) technology to enable the digital detection of a target sequence within intact genomic material. Termed CRISPR-Chip, the biosensor uses the gene-targeting capacity of catalytically deactivated CRISPR-associated protein 9 (Cas9) complexed with a specific single-guide RNA and immobilized on the transistor to yield a label-free nucleic-acid-testing device whose output signal can be measured with a simple handheld reader. We used CRISPR-Chip to analyse DNA samples collected from HEK293T cell lines expressing blue fluorescent protein, and clinical samples of Reprints and permissions information is available at www.nature.com/reprints. * kiana_aran@kgi.edu. Correspondence and requests for materials should be addressed to K.A. Author contributions R.H. optimized the CRISPR-Chip design, performed the CRISPR-Chip DMD experiments, data collection and analysis, LOD optimization, HEK-BFP calibration methodologies in the presence and absence of contamination, and kinetic analysis, and prepared the manuscript. S.B. assisted in optimization of the CRISPR-Chip assay protocols, performed the MB-dRNP studies, DMD patient sample analysis, HEK-BFP PCR experiments and analysis, and prepared the manuscript. T.T. assisted with the initial CRISPR-Chip design, performed initial CRISPR-Chip protocols for HEK-BFP studies, and prepared the manuscript. T.d. performed the synthesis of sgRNA for the bfp and Scram studies, genomic purification and initial system design, and helped with manuscript preparation. J.E. contributed to the design of the DMD-based validation of CRISPR-Chip and provided the PCR and sequencing data for the DMD studies. M.S. contributed to the design of the DMD-based validation of CRISPR-Chip and assisted in manuscript preparation. N.A.W. and J.-Y.C. assisted T.D. with the synthesis of sgRNAs for bfp studies and assisted with sample preparation. J.N. and B.G. assisted with CRISPR-Chip data analysis and manuscript preparation. M.A. and J.P. assisted with manuscript preparation and data analysis. R.P. assisted with the design of threshold experiments, data analysis and CRISPR-Chip validation. N.M. supervised the synthesis of sgRNAs for the bfp and Scram studies. I.M.C. assisted with technology design, DMD validation and manuscript preparation. K.A. designed and developed the technology, planned and supervised the project, analysed, interpreted and integrated the data, and prepared the manuscript.

No abstract

Neste trabalho, a interação de doxorrubicina com DNA (obtido de timo de bezerro) em fita dupla foi investigada através de técnicas de espectrofotometria UV-Vis, voltametria e espectrofluorometria, usando azul de metrileno (MB) como marcador. O comportamento voltamétrico da doxorrubicina foi investigado em eletrodo de carbono vítreo usando voltametria de pulso diferencial. A doxorrubicina é reduzida, produzindo um pico de redução. Os dois estudos, espectrofotometria UV-Vis e voltametria de pulso diferencial, confirmam a reação de intercalação. Os resultados mostraram que a doxorrubicina e a molécula de MB foram intercaladas na dupla hélice do DNA. A constante de ligação aparente de doxorrubicina com DNA foi 3,2 × 10 4 L mol -1 . O sinal de fluorescência da doxorrubicina e azul de metileno é suprimido com a adição de DNA. A equação de Stern-Volmer baseou-se na supressão do sinal de fluorescência da doxorrubicina.In this work, the interaction of doxorubicin with calf thymus double strand Deoxyribonucleic acid (ds-DNA) has been investigated with the use of Methylene Blue (MB) dye as a probe by the application of UV-Vis spectrophotometry, voltammetry and spectrofluorometry. The voltammetric behavior of doxorubicin has been investigated at glassy carbon electrode using differential pulse voltammetry. Doxorubicin is reduced, yielding one reduction peak. Both UV-Vis spectrophotometry and differential pulse voltammetry studies confirm the intercalation reaction. The results showed that both doxorubicin and the MB molecule could intercalate into the double helix of the DNA. The apparent binding constant of doxorubicin with DNA has been found to be 3.2 × 10 4 L mol -1 . The fluorescence signal of doxorubicin and methylene blue was quenched with DNA addition. The Stern-Volmer equation was plotted based on quenching fluorescence signal of doxorubicin.Keywords: doxorubicin, DNA, chemotherapy, spectrophotometry, voltammetry, spectrofluorometry IntroductionStudy of interactions between drugs and DNA is very interesting and significant not only in understanding the mechanism of interaction, but also for the design of new drugs. 1,2 However mechanism of interactions between drug molecules and DNA is still relatively little known. It is necessary to introduce more simple methods for investigating the mechanism of interaction. By understanding the mechanism of interaction, designing of new DNA-targeted drugs and the screening of these in vitro will be possible.A great variety of substances, including several agents of importance in cancer chemotherapy, 3 are known to bind to DNA by intercalation. 4 Attention has been concentrated on the classical intercalating drugs, acridines and ethidium bromide. [4][5][6] Studies on the binding of various dyes, drugs and antibiotics to DNA and chromatin have contributed to the understanding of the structure of these macromolecules, 6-14 and have suggested possible mechanisms of the biological activity of some drugs. 3 Molecular models of the intercalation of some drugs into DNA have been describ...