The RVC has developed a novel nanoparticle-based-system for delivery of nucleic acids into cells, often called "transfection".  The technology is applicable to a wide range of cell types, with potential in vivo applications.

Challenge       

Professor Liam Good joined the RVC in 2007 to add a new dimension to RVC’s research addressing the global issue of antimicrobial resistance. Good’s expertise in antisense approaches to inhibit essential genes in bacteria provided several new possibilities for development. In particular, the work led-on to the development of peptide nucleic acid fluorescence in situ hybridisation (PNA-FISH) probes for bacteria detection and his idea of overcoming cell delivery barriers by linking oligomers to cell wall active peptides has enabled drug target validation through RNA silencing – a method now widely used in early-stage drug development.

That work showed that relatively large molecules can enter microbes and cationic peptides can even act as carriers to deliver reagents and drugs. A major research goal of Professor Good was to devise ways to improve the delivery of antisense oligonucleotides into bacteria, since he had shown they could be used to provide remarkable selectivity of antibacterial activity, something lacking from conventional antimicrobial drugs. To this end, he examined polymers that offered similar structural properties to the carrier peptides, but which could provide affordable, stable and safe solutions.

The group was attracted to the polymer, polyhexanide biguanide (PHMB), also known as polyhexanide, which is widely used in industrial applications for its antimicrobial properties (e.g. in wound care and as contact lens disinfectant). Such cationic polymers are generally believed to provide antimicrobial effects through preferential targeting of the negatively charged lipids within bacterial cells; however, the team’s experience with peptides suggested that the mechanism(s) may be more nuanced and involve cell entry.

Solution      

The first direct insight came from constructing a fluoro-tagged version of the polymer and tracking the localisation in pathogens and host cells. The results were surprising and striking, showing that PHMB efficiently enters all microbial and mammalian cells types examined. This raised new questions about its mechanism(s) of antimicrobial action and safety profile and raised possibilities for diverse practical applications that could potentially address otherwise intractable delivery challenges.

To further investigate mechanisms, the team studied the uptake pathways, tracked localisation over time and measured the effects on cell membrane integrity. The results revealed that the polymer enters bacterial cells with little damage to cell membranes but then condenses chromosomes]. In mammalian cells, the polymer enters via dynamin-dependent endocytosis and is largely retained in endosomes and excluded from the nucleus, explaining its selective toxicity against microbes. This supported the idea that the polymer can be used as a delivery technology and greatly broadened the scope for applications.

In follow-on studies, the team assessed whether the polymer could be used to form complexes (nanoparticles) with reagents and drugs and mediate delivery into bacteria, fungi, parasites and mammalian cells. In addition, the team demonstrated that the polymer is directly antimicrobial against hard to inhibit intracellular pathogens.

With these observations in place, multiple academic and industrial research collaborations have ensued to further define the antimicrobial mechanisms and understand opportunities for practical applications of the polymer-mediated delivery approach. The work has also influenced regulatory agencies’ decisions and guidance. Thus, what commenced as research into efficient carriers to enhance cell penetration into bacteria led to the discovery of PHMB’s novel mechanisms of action involving cell uptake and this knowledge has underpinned a range of impacts. Promising work with long-term potential for impact continues at the RVC, to pursue the original aim of reagent and drug delivery into bacteria, specifically to develop alternatives to traditional antibiotic-based strategies for infection control.

Impact      

Novel mechanisms of action for the antimicrobial polymer polyhexanide biguanide (PHMB) have been identified through RVC research demonstrating its penetration into cells, formation of nanoparticles with a range of compounds and mediation of functional delivery into cells.

Following patent filings and company creation to commercialise the technology, impacts include investment from private individuals and venture capital; sales of research kits and services; influence on regulatory agencies’ decisions and guidance, and out-licensing for both human and veterinary product applications. In addition to three (two completed) clinical trials in human health, the technology platform has been developed via a multi-million dollar (USD) license deal to a global animal health business for both production and companion animal applications.

When the research team recognised the ability to improve cell and tissue delivery using a polymer with an excellent safety profile, the RVC protected the relevant intellectual property through patent filing (WO2013054123) in all major territories and licensed the technology to a spin-out company, Tecrea Ltd, formed in 2012, as a vehicle for commercialisation and out-licensing of the platform technology in several sectors.

Tecrea’s progress in animal health has led to formation of a progeny spin-out: Tecrea Animal Health Ltd. Activities have delivered multiple impacts in the form of company formation, jobs created, inward investments, product sales, services sales, influence on court decisions, royalties to RVC, and progress in the development of new therapies for human (reaching clinical trial stage IIb) and animal health.

Partners      

AstraZeneca

Cobra Biologics

Nanoptima Ltd

LifFull Ltd

Toleranzia AB

Blueberry Therapeutics Ltd

Publications     

Title Publication Year

Polyhexamethylene Biguanide and Nadifloxacin Self-Assembled Nanoparticles: Antimicrobial Effects against Intracellular Methicillin-Resistant Staphylococcus aureus

Polymers

2018

Bactericidal and Anti-biofilm Effects of Polyhexamethylene Biguanide in Models of Intracellular and Biofilm of Staphylococcus aureus Isolated from Bovine Mastitis

Frontiers in Microbiology.

2017

Bactericidal effects of Polyhexamethylene Biguanide against intracellular Staphylococcus aureus EMRSA-15 and USA 300

Journal of Antimicrobial Chemotherapy

2016

Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB)

PLoS Negl Trop Dis

2015

 

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