Unexpected Like-Charge Self-Assembly of a Biguanide-Based Antimicrobial Polyelectrolyte.
Polyelectrolyte chains dissolved in good solvent are expected to collapse in compact configurations in the presence of multivalent ions. Here, we show that a weakly charged, hydrophilic polyelectrolyte containing biguanide groups self-assembles in water also in the presence of monovalent counterions, even at low salt concentrations. The polymer assembles in a compact, ordered, hairpin-like shape that, with increasing the ionic strength of the solution, can collapse further in three- or five-folded structures. Neither water nor ions mediate the self-assembly which, instead, is driven by the like-charge pairing of the biguanide units. The thermodynamics of the self-assembly show that the self-association is enthalpically driven, is isodesmic (at least at low aggregation number), and is favored by increasing salt concentration. This unique self-assembly behavior may be linked to the well-known polymer's antimicrobial properties and could help in rationalizing its biological activity.
School of Chemical Engineering and Analytical Science, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.|Department of Chemistry and Centre for Scientific Computing, University of Warwick , Coventry CV4 7AL, United Kingdom.
Afroditi Maria
AM
Zaki
School of Chemical Engineering and Analytical Science, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.|Department of Chemistry and Centre for Scientific Computing, University of Warwick , Coventry CV4 7AL, United Kingdom.
Alessandro
A
Troisi
School of Chemical Engineering and Analytical Science, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.|Department of Chemistry and Centre for Scientific Computing, University of Warwick , Coventry CV4 7AL, United Kingdom.
Paola
P
Carbone
D000890:Anti-Infective Agents / Q000737:chemistry*; D001645:Biguanides / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions / Q000737:chemistry; D000071228:Polyelectrolytes / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D000890:Anti-Infective Agents; D001645:Biguanides; D007477:Ions; D000071228:Polyelectrolytes; D014867:Water