Electrostatic and hydrophobic interactions involved in CNT biofunctionalization with short ss-DNA

This work is aimed at studying the adsorption mechanism of short chain 20-mer pyrimidinic homoss-DNA (oligodeoxyribonucleotide, ODN: polyC20 and polyT20) onto CNT by reflectometry. To analyze the experimental data, the effective-medium theory using the Bruggemann approximation represents a suitable optical model to account for the surface properties (roughness, thickness, and optical constants) and the size of the adsorbate. Systematic information about the involved interactions is obtained by changing the physicochemical properties of the system. Hydrophobic and electrostatic interactions are evaluated by comparing the adsorption on hydrophobic CNT and on hydrophilic silica and by modulating the ionic strength with and without Mg2+. The ODN adsorption process on CNT is driven by hydrophobic interactions only when the electrostatic repulsion is suppressed. The adsorption mode results in ODN molecules in a side-on orientation with the bases (nonpolar region) toward the surface. This unfavorable orientation is partially reverse by adding Mg2+. On the other hand, the adsorption on silica is dominated by the strong repulsive electrostatic interaction that is screened at high ionic strength or mediated by Mg2+. The cation-mediated process induces the interaction of the phosphate backbone (polar region) with the surface, leaving the bases free for hybridization. Although the general adsorption behavior of the pyrimidine bases is the same, polyC20 presents higher affinity for the CNT surface due to its acid-base properties.Authors acknowledge the financial contributions of FONCyT, SeCyT-UNC, CONICET, the International Exchange Collaboration between CAPES (Brazil) and SPU (Argentine) (Grant No. 025/05), and National Institute of General Medical Sciences (NIGMS)/National Institutes of Health (1SC3GM081085) (C.D.G). M.J.E. thanks the Ministry of Education and Science of Spain (Project NAN2004-093006-C05-03) and the “Ramón and Cajal” Program. M.L.C. thanks CONICET for the fellowship granted.Peer Reviewe

Electrostatic and Hydrophobic Interactions Involved in CNT Biofunctionalization with Short ss-DNA

This work is aimed at studying the adsorption mechanism of short chain 20-mer pyrimidinic homoss-DNA (oligodeoxyribonucleotide, ODN: polyC(20) and polyT(20)) onto CNT by reflectometry. To analyze the experimental data, the effective-medium theory using the Bruggemann approximation represents a Suitable optical model to account for the surface properties (roughness, thickness, and optical constants) and the size of the adsorbate. Systematic information about the involved interactions is obtained by changing the physicochemical properties of the system. Hydrophobic and electrostatic interactions are evaluated by comparing the adsorption oil hydrophobic CNT and oil hydrophilic silica and by Modulating the ionic Strength With and without Mg(2+). The ODN adsorption process oil CNT is driven by hydrophobic interactions only when the electrostatic repulsion is Suppressed. The adsorption mode results in ODN molecules in a side-on orientation with the bases (nonpolar region) toward the surface. This unfavorable orientation is partially reverse by adding Mg(2+). On the other hand, the adsorption oil silica is dominated by the strong repulsive electrostatic interaction that is screened at high ionic strength or mediated by Mg(2+). The cation-mediated process induces the interaction of the phosphate backbone (polar region) with the surface, leaving the bases free for hybridization. Although the general adsorption behavior of the pyrimidine bases is the same, polyC(20) presents higher affinity for the CNT Surface due to its acid-base properties.FONcyTFONcyTSeCyT-UNCSeCyT-UNCCONICETCONICETCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CAPES (Brazil)SPU (Argentine)[025/05]SPU (Argentine)National Institute of General Medical Sciences (NIGMS)/National Institutes of Health (NIH)National Institute of General Medical Sciences (NIGMS)/National Institutes of Health (NIH)[ISC3GM081085]Education and Science of SpainEducation and Science of Spain[NAN2004-093006-C05-03]Ramon and Cajal Program""Ramon and Cajal"" Progra