The piperazine functional group has found applications in the structure of novel antidepressants, chemotherapeutics, stimulants, and more recently as antimicrobial agents. Inclusion of piperazine in a material also leads to the chelation of metals (including toxic metals), which would have several environmental applications as fiber mats or bioengineering scaffolding materials. Thus, we synthesized the first aliphatic polyester polypiperazines directly from the Ti(IV) condensation of 1,4-Bis(1-propanol)piperazine, 1,4-Bis(3-aminopropyl)piperazine, or 1,4-Bis(1-hexanol)piperazine with either adipic acid or succinic acid. We characterized these novel polymeric materials using NMR, IR, gel permeation chromatography, thermal gravimetric analysis and differential scanning calorimetry. Since the biodegradation of these polymeric materials could lead to the release of a toxic by-product (the bis piperazine compounds), we analyzed the anti-microbial activities of the diol and diamine piperazines using E. coli AG100 as planktonic cultures (using the starting bis alcohols and bis amine compounds), and as biofilms on the thermocast polypiperazines. We determined the anti-microbial activities using growth inhibition assays (with and without Levofloxacin) as well as live/dead fluorescence staining of planktonic and biofilms of each organism. We calculated the IC50 of each piperazine alcohol or amine and concluded that these compounds show no significant anti-microbial properties at concentrations as high as 4.5mM. We compared our growth inhibition results to 1-napthylpiperazine; a published anti-microbial agent. These collective data suggest polyester polypiperazines could be a novel thermoplastic, bioinert, biodegradable, scaffolding material for tissue engineering and environmental applications.

Direct polymerization of aliphatic bis-piperazines compounds and their non-anti-microbial properties

ACS Spring 2022

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