Induction of Platinum(II) Coordination-Bonded Network Formation in Coacervates of Single-Stranded DNAs

Coacervates are dense aqueous phases that form by liquid-liquid phase separation. Seven Pt(II) complexes with different charges and nucleotide reactivities were examined for their ability to induce coacervate formation in a 21-mer single-stranded DNA (ssDNA). Only AMPZ ([<i>cis</i>-{Pt(NH₃)₂}₂(μ-pyrazolato)(μ-OH)](NO₃)₂), a cationic dinuclear Pt(II) complex, efficiently induced coacervate formation in ssDNA containing only thymine (T21-DNA). AMPZ has very low reactivity with thymine but relatively high reactivity with guanine, and when three of the thymines in T21-DNA were substituted with a guanine to produce T18-G3-DNA, the resulting coacervate was observed to undergo gelation via the formation of an extensive Pt-DNA coordination-bonded network. We then examined the construction of coacervates that comprise multiple phases by adding AMPZ to a mixture of two types of ssDNAs, a highly reactive T10-G11-DNA and a minimally reactive T21-DNA, and found that two distinct assembly states─a cell mimetic assembly and a DNA-encapsulating gel─could be formed.