Pairing statistics and melting of random DNA oligomers: Finding your partner in superdiverse environments

Understanding of the pairing statistics in solutions populated by a large number of distinct solute species with mutual interactions is a challenging topic, relevant in modeling the complexity of real biological systems. Here we describe, both experimentally and theoretically, the formation of duplexes in a solution of random-sequence DNA (rsDNA) oligomers of length L = 8, 12, 20 nucleotides. rsDNA solutions are formed by 4L distinct molecular species, leading to a variety of pairing motifs that depend on sequence complementarity and range from strongly bound, fully paired defectless helices to weakly interacting mismatched duplexes. Experiments and theory coherently combine revealing a hybridization statistics characterized by a prevalence of partially defected duplexes, with a distribution of type and number of pairing errors that depends on temperature. We find that despite the enormous multitude of inter-strand interactions, defectless duplexes are formed, involving a fraction up to 15% of the rsDNA chains at the lowest temperatures. Experiments and theory are limited here to equilibrium conditions

Achieving Selective Targeting Using Engineered Nanomaterials

The development of Drug Delivery Systems (DDS) able to selectively deliver a controlled amount of a drug only to diseased cells would represent a dramatic development in nanomedicine. One of the multiple challenges still paving the way towards this goal is the elaboration of strategies that would allow targeting with extreme accuracy specific cells, as cancerous cells, among a large variety of closely related ones. In this work, we review the most recent nanotechnology applications aiming at controlling the selectivity of the interaction of delivery nanosystems with cells, with a focus on multivalent targeting. We briefly review thermodynamic models of multivalent interactions and highlight the challenges that still need to be addressed to transfer theoretical design principles into practical applications. In particular, suitable experimental systems based on multivalent models often require the control of the nanocarrier characteristics at the molecular level. Traditional delivery methods, however, fail to provide such degree of control. DNA nanotechnology is a growing field of nanoscience that has witnessed impressive developments in the past decades and has led to major advances in the fabrication of nanostructures and self-assembled systems. Relying on the possibility of controlling their molecular interactions by sequence design, nucleic acids can serve the drug delivery program by providing desired nanostructures with nearly atomic precision. In combination with the recent achievements in the research on DNA aptamers, short nucleic acid sequences isolated to interact selectively with a specific target, DNA nanotechnology is undoubtedly one of the most promising tools for the development of selective DDS.info:eu-repo/semantics/publishe