Amphiphilic Counterion Activators for DNA: Stimuli‐Responsive Cation Transporters and Biosensors in Bulk and Lipid Bilayer Membranes

Abstract

We report that amphiphilic counterions can enable DNA to act as cation carrier, enzyme detector and biosensor. Calf thymus DNA is used as example throughout the study. Evaluation of a series of counterion activators suggests that strong amphiphilicity, alkyl or calix[4]arene tails and guanidinium cations give best results, whereas weak amphiphilicity, bola-amphiphilicity, planar aryl tails and ammonium cations are less satisfactory for various reasons. In the U-tube, DNA-counterion complexes can carry cations such as safranin O or p-xylene-bis-pyridinium bromide (DPX) across bulk chloroform membranes, whereas anions such as carboxyfluorescein (CF) and (8-Hydroxy-1,3,6-pyrenetrisulfonate (HPTS) are not transported. Uptake of DNA-counterion complexes into intact vesicles is demonstrated by DNA trapping experiments with internal polylysine. Comparison of results from different assays suggests that DNA-counterion complexes act as cation carriers under mild conditions, whereas pore formation and lysis dominate at higher concentrations. Applicability of DNA-counterion transporters for the detection of enzyme activity is demonstrated with phytate as an inactivating substrate and phytase as a reactivating enzyme. Compatibility with biosensing is exemplified with the fluorometric monitoring of phytate levels in almond extracts. The conceptual significance of these findings is briefly discussed, as are promising perspectives such as the application of DNA chemistry to multianalyte sensing in fluorogenic vesicles.

Dynamic Octopus Amphiphiles as Powerful Activators of DNA Transporters: Differential Fragrance Sensing and Beyond

“…However, previous controls in the U-tube have confirmed that counterion-activated DNA can act as cation carrier at low concentrations. [20] In a typical procedure, octopus amphiphile G1H4O8 was added as concentrated stock solution in DMSO to the stirred and thermostated suspension of fluorogenic vesicles (Figure 2). Unchanged fluorescence at this point confirmed that octopus amphiphiles G1H4O8 alone are not active in lipid bilayer membranes.…”

“…[2][3][4] The synthesis of transport systems [5][6][7][8][9][10][11][12][13][14][15][16][17] that respond to chemical stimulation was the first key step to achieve this goal. [18][19][20] In sensing systems, these stimuli-responsive transporters function as signal transducers. Their combination with enzymes as signal generators [21,22] afforded the first functional sensors that are operational in complex matrices from the supermarket to hospitals.…”

Pattern generation with synthetic sensing systems in lipid bilayer membranes

“…S4A †; previous U-tube analysis has shown that countercation-activated ctDNA transports the cationic DPX but not the anionic HPTS across bulk liquid membranes). 31 Before the addition of DNA polyions, cationic amphiphiles A1H1O1-G1H3O30 did not cause a fluorescence response and were thus membrane-inactive under the selected, optimized conditions (Figs. S4A, S6A, S7A, S8A †).…”

“…[29][30][31] This problem has been solved with the in situ introduction of hydrophilic headgroups that can react with hydrophobic analytes to afford amphiphilic counterions which, in turn, can activate polyion transporters and generate a ''turnon'' fluorescent response (Fig. 1).…”

Single‐Nucleotide‐Resolution DNA Differentiation by Pattern Generation in Lipid Bilayer Membranes

“…To ensure biological compatibility of our liposome assay we employed osmotic balanced (isotonic) vesicles suspensions in Tris buffered media (pH = 7.4). This routine assay report on internal dyes release as an increase in the HPTS fluorescence (Figure B) . The typical transport experiment consisted in measuring the HPTS fluorescence kinetics of a suspension of liposomes (EYPC‐LUVs⊃HPTS/DPX) in Tris buffer (pH = 7.4) upon addition (at t = 25 s) of amphiphile [ (OxTy) m Arg n , in which y denotes the number of aldehyde carbon atoms], followed by the anionic biopolymer (i.e., Herr‐DNA at t = 50 s) and finally, excess of Triton‐X (at t = 250 s) ( Figure A and Supporting Information).…”