Synthesis and characterisation of silver-polyquaternium nanoparticles: an interesting new family of antimicrobials

Evita Chundoo, Tarnveer Bhamra, Brian J Tighe, Paul D Topham

Research output: Unpublished contribution to conferencePosterpeer-review


Polyquaternium (PQ) antibacterials, particularly PQ-1, are common components of ophthalmic care solutions. Similarly, the antimicrobial applications of silver in medical devices are well-known. The observation that silver nanoparticles (AgNPs) complexed with PHMB show synergistically enhanced activity led us to investigate the families of novel nanostructures formed through complexation of AgNPs with (initially non-antimicrobial) PQs. Interest centres on synergistic activity and potential ophthalmic applications.

Silver nanoparticles were synthesised from silver nitrate with sodium borohydride reducing agent and one of the following polyquaterniums: polyquaternium-4 (PQ-4), polyquaternium-10 (PQ-10) and polyquaternium-46 (PQ-46). The filtered nanoparticles were then characterised using dynamic light scattering (DLS) and UV-Visible spectroscopy. Initial studies of antimicrobial activity were carried out with Staphylococcus Aureus, a common ocular pathogen.

Successful synthesis of silver-PQ nanoparticles was confirmed by UV-Visible spectroscopy, which indicated a surface plasmon resonance (SPR) band of 402 nm ± 1 nm for silver-PQ-10 nanoparticles, a SPR band of 406 nm ± 3 nm for silver-PQ-4 nanoparticles and a SPR band of 447 nm ± 24 nm for silver-PQ-46 nanoparticles. Antimicrobial activity was assessed with zone of inhibition (ZOI) measurements. Silver-PQ-46 nanoparticles displayed a level of antimicrobial activity (12 mm ± 0.5 mm) higher than that of silver nanoparticles synthesised without any polyquaternium (9 mm ± 1 mm) and silver nanoparticles made with PQ-4 and PQ-10 (8 mm ± 1 mm and 7 mm ± 1 mm respectively) exhibited a slightly lower level of activity. None of the polyquaterniums displayed antimicrobial activity alone.

Novel hybrid antimicrobials, in the form of silver-PQ46 nanoparticles, demonstrated an enhanced level of activity when compared with the unmodified polyquaterniums. This provided an interesting new platform to improve the efficacy of current ocular antimicrobials. These complexes -especially those based on PQs with inherent antimicrobial activity – may have potential for use in ophthalmic devices.
Original languageEnglish
Publication statusPublished - 30 May 2019


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