We present anew class of DNA-based nanoswitches that, upon enzymatic repair,c ould undergo ac onformational change mechanism leading to ac hange in fluorescent signal. Such folding-upon-repair DNAn anoswitches are synthetic DNAs equences containing O 6-methyl-guanine (O 6-MeG) nucleobases and labelled with af luorophore/quencher optical pair.T he nanoswitches are rationally designed so that only upon enzymatic demethylation of the O 6-MeG nucleobases they can form stable intramolecular Hoogsteen interactions and fold into an optically active triplex DNAs tructure.W e have first characterized the folding mechanism induced by the enzymatic repair activity through fluorescent experiments and Molecular Dynamics simulations.W et hen demonstrated that the folding-upon-repair DNAn anoswitches are suitable and specific substrates for different methyltransferase enzymes including the human homologue (hMGMT) and they allow the screening of novel potential methyltransferase inhibitors.

We demonstrate here the use of DNA repair enzymes to control the assembly of DNA‐based structures. To do so, we employed uracil‐DNA glycosylase (UDG) and formamidopyrimidine DNA glycosylase (Fpg), two enzymes involved in the base excision repair (BER) pathway. We designed two responsive nucleic acid modules containing mutated bases (deoxyuridine or 8‐oxo‐7,8‐dihydroguanine recognized by UDG and Fpg, respectively) that, upon the enzyme repair activity, release a nucleic acid strand that induces the self‐assembly of DNA tiles into tubular structures. The approach is programmable, specific and orthogonal and the two responsive modules can be used in the same solution without crosstalk. This allows to assemble structures formed by two different tiles in which the tile distribution can be accurately predicted as a function of the relative activity of each enzyme. Finally, we show that BER‐enzyme inhibitors can also be used to control DNA‐tile assembly in a specific and concentration‐dependent manner.

usually proceeds through the formation of non-covalent reversible interactions, they can also be designed to undergo a change in their structural configuration or functionality in response to multiple chemical and environmental stimuli. [15,16] Rational and programmable control of these supramolecular functional bio-scaffolds remain, however, challenging, and it is often difficult to achieve higher-order organization of multiple labeling groups in a versatile and dynamic way.Compared to other biomolecules employed for the self-assembly of structures and scaffolds, the use of synthetic DNA as a building block presents several advantages. First, the predictable and programmable nature of DNA-DNA base pairing allows the rational design of DNAbased structures with well-defined 2D and 3D geometry. [17,18] Second, the sequencespecific addressability of DNA strands together with the possibility to covalently attach different functional moieties on the backbone of a DNA oligonucleotide permits the controlled nanoscale decoration at specific locations on the DNA structure with several molecular labels. The above features have been successfully exploited in the last years to make DNA-based scaffolds decorated with a variety of different chemical and biological species such as antibodies, [19,20] signaling moieties, [21,22] aptamers, [23,24] virus capsids, [25,26] and proteins [27,28] that have found applications in bioimaging, drug delivery, and cancer therapeutics. [21,29,30] Despite the above examples clearly illustrating the versatility of synthetic DNA as building blocks to create molecular bio-scaffolds, the methods employed so far for the decoration of DNA-based assemblies often lack versatility and programmability, they are "static" and do not allow the replacement of the labels "on the fly" without prior structure disassembly. Developing novel approaches to control the decoration and labeling of DNA scaffolds with multiple functional moieties in a dynamic way will allow for achieving functional biomaterials with improved adaptability, precision, and sensing capabilities.Motivated by the above arguments, we demonstrate here a strategy to achieve dynamic and site-specific decoration of DNAbased scaffolds. To do so, we employed a model scaffold system DNA structure formed through the self-assembly of DNA tiles. More specifically, we have employed anti parallel double-crossover DNA tiles (DAE-E) formed through the hybridization of five different DNA strands. [31][32][33] These tiles display 4 singlestranded sticky ends (each of 5 nucleotides) that induce their An approach to achieving dynamic and reversible decoration of DNA-based scaffolds is demonstrated here. To do this, rationally engineered DNA tiles containing enzyme-responsive strands covalently conjugated to different molecular labels are employed. These strands are designed to be recognized and degraded by specific enzymes (i.e., Ribonuclease H, RNase H, or Uracil DNA Glycosylase, UDG) inducing their spontaneous de-hybridization from the assembled tile and rep...

We present a new class of DNA‐based nanoswitches that, upon enzymatic repair, could undergo a conformational change mechanism leading to a change in fluorescent signal. Such folding‐upon‐repair DNA nanoswitches are synthetic DNA sequences containing O6‐methyl‐guanine (O6‐MeG) nucleobases and labelled with a fluorophore/quencher optical pair. The nanoswitches are rationally designed so that only upon enzymatic demethylation of the O6‐MeG nucleobases they can form stable intramolecular Hoogsteen interactions and fold into an optically active triplex DNA structure. We have first characterized the folding mechanism induced by the enzymatic repair activity through fluorescent experiments and Molecular Dynamics simulations. We then demonstrated that the folding‐upon‐repair DNA nanoswitches are suitable and specific substrates for different methyltransferase enzymes including the human homologue (hMGMT) and they allow the screening of novel potential methyltransferase inhibitors.

To assess the efficacy, tolerability, and clinical outcome of high dose IV Vitamin C administration in patients suffering from acute respiratory distress syndrome (ARDS). A prospective, randomized, controlled, open-label study was conducted at the Intensive Care Unit of the National Center for Allergy and Chest Diseases, Cairo, Egypt. Forty clinically and radiologically diagnosed cases of eligible ARDS patients were randomized to either, Group 1 (Control); 20 patients received conventional ARDS management, or Group 2 (Test); 20 ARDS patients received 10 g IV Vitamin C on two divided doses, both for 10 days. Vitamin C, Interleukin 8 (IL8), and nuclear factor erythroid 2-related factor 2 (NRf2) levels together with PaO 2 /FiO 2 were all measured for both groups at baseline and after 10 days from study start. Both groups were comparable at baseline. After 10 days of Vitamin C administration, a significant increase (P<0.001) in levels of Vitamin C, NRf2, and PaO 2 /FiO 2 together with a significant decrease (P<0.001) in IL8 was noted in the test versus the control group. The number of patients weaned off mechanical ventilation MV was significantly higher in the test versus the control groups (15 versus 6, P= 0.004, respectively). Survival and occurrence of side effects were comparable across groups. In conclusion, Administration of 10 g IV Vitamin C in 2 divided doses daily for 10 days in ARDS patients improved lung functions, pulmonary oxygenation, oxidative stress, and inflammatory markers. High-dose vitamin C reduced IL8 levels and facilitated weaning off MV. Vitamin C was tolerable with no significant side effects or drug interactions reported throughout the 10 daystreatment. (Clinicaltrials.gov Registration number: NCT03780933).