Nanoprecision in antibiotic delivery using targeted nanoparticles

Secondary Supervisor(s): Professor Jessica Blair

University of Registration: University of Birmingham

BBSRC Research Themes: Understanding the Rules of Life (Microbiology)

Project Outline

Gram-negative bacterial species, including E. coli, are major causes of infectious diseases worldwide and account for all organisms in the “critical” category of the WHO list of antibiotic-resistant "priority pathogens".1 These bacteria are intrinsically drug-resistant due to the presence of an impermeable outer membrane. The design of novel antibiotics with activity against Gram-negative bacteria can be challenging due to the drug’s size and hydrophobicity properties for crossing the membrane and accessing intracellular targets. Most antibiotics work by entering bacterial cells and interacting with specific targets to kill or inhibit cell growth. However Gram-negative bacteria are also especially adept at limiting intracellular antibiotic accumulation with a suite of efflux pumps that export a broad range of antimicrobials. A multi-targeted approach of local delivery is necessary to increase efficiency of drug localisation and effective drug activity which will lead in limiting drug dose and new methods of therapies.

Nanoscale materials are attractive vehicles for the delivery of therapeutic agents with wide chemical versatility which provides potential to overcome multi-drug resistance mechanisms. Recently we have developed functional nanoparticles for targeted therapeutic properties based on either functional modification of their surface to allow membrane penetration2,3 or internal modification of the structural framework to encapsulate drugs.4 Silica nanoparticles are attractive vehicles which can encapsulate antibiotics in their framework, they have excellent biocompatibility, facile synthesis with tunability of their size and surface chemistry for functionalisation. This project will investigate novel nanoparticle designs using supramolecular chemistry principles for molecular encapsulation in the nanoparticle framework of drugs and inhibitors of efflux pumps but also bioinorganic chemistry approaches to intervene with receptors present in bacterial membranes to allow both efficient cross of the nano-platform in the bacterial cell, limitation of drug exportation and efficient drug delivery. The project builds on recent results on drug encapsulation and release.3,4

Hypothesis

In this project we will develop a set of nanoparticles with iron siderophores that target specific proteins in the bacterial cell membrane to increase the uptake of antibiotics inside the cell. We will design nanoparticle networks incorporating inhibitors to efflux pumps to limit antibiotic expulsion. We will use supramolecular recognition principles to select efficient pairs of drugs and inhibitors.

Methods

The project includes molecular synthesis of ligands and metal complexes, nanoparticle modification and characterisation as well as advanced spectroscopic techniques to study molecular interactions and drug release. Biophysical studies of interaction of surface groups with membrane proteins and drug-inhibitor interactions will provide background for subsequent analysis of the nanoparticles in their membrane interactions with advance microscopy techniques and examination of the nanoparticle activity in bacterial cells.

References

1. E. M Darby, E. Trampari, P. Siasat, M. Solsona Gaya, I. Alav, M. A Webber, J.M.A. Blair, Nat. Rev.Microbiol., 2023, 5, 280-295

2. A. R. Muguruza, A. di Maio, N. J. Hodges, J. M. A. Blair, Z. Pikramenou. Nanoscale Adv 2023, 5, 2453-2461. DOI: 10.1039/D2NA00884J

3. L. S. Watson, J. Hughes, S. T. Rafik, S.T., A. R. Muguruza, P. M. Girio, G. Rochford, G, A. J. MacRobert, N. J. Hodges, E. Yaghini, Z. Pikramenou Nanoscale, 2024, 16, 16500–16509. https://doi.org/10.1039/D4NR01901F

4. A. R. Muguruza, M. L. Odyniec, M. Manhota, Z. Habib, K. Rurack, J.M.A. Blair., S. A. Kuehne, A. D. Walmsley, Z. Pikramenou Microporous Mesoporous Mater., 2024, 363, 112841. DOI: 10.1016/j.micromeso.2023.112841.

Metal nanoparticles for photobiomodulation localised therapy of brain injury

Secondary Supervisor(s): Professor William Palin

University of Registration: University of Birmingham

BBSRC Research Themes: Integrated Understanding of Health (Pharmaceuticals)

Project Outline

Traumatic Brain Injury is a significant global health problem with no disease modifying treatment shown to improve outcomes. The pathophysiological mechanisms include factors such as raised intracranial pressure and cerebral hypoxia, but also mitochondrial dysfunction, neuroinflammation, and oxidative stress. Pharmacological therapeutics typically target discrete pathways or mechanisms, but have thus far failed to demonstrate clear benefit in the context of this multi-faceted pathology.

Photobiomodulation (PBM) is an optical therapy gaining recent attention based on the delivery of red or near-infrared wavelength light (600-1000 nm) for a therapeutic effect. A proposed mechanism of action is based on the chromophore activity of cytochrome c oxidase, which influences mitochondrial function that averts the overproduction of reactive oxygen, reducing local oxidative stress. Via modulation of apoptotic pathways [1], cell survival is increased. PBM has also been demonstrated to reduce microglia activation after traumatic brain injury and ameliorate the local inflammatory response.

Currently, its translational potential is severely limited due to current approaches which use transcranial (non-invasive) application that restricts light delivery and optimal energy dose at the injurious target site and cellular level.[2]

Nanoparticles have emerged with attractive properties for crossing the Brain Blood Barrier, making them good candidates for non-invasive therapy approaches. [3] Gold nanoparticles are attractive probes with photothermal effect due to their surface plasmon resonance and provide possibilities for down and upconversion of light with functionalisation to allow localised light delivery on the cellular level. Recent results of modified nanoparticles show therapeutic action by light excitation.[4]

Aims and Hypothesis

The project will develop a novel class of nanoparticles which will target mitochondria at the injury site. Nanoparticles will be modified with photoactivatable probes to down convert to either 660 nm or 810 nm to enable precise photobiomodulation at the cellular level. This approach will improve the therapeutic efficiency of PBM by directly stimulating mitochondrial activity, leading to increased ATP production, reduced oxidative stress, and enhanced cellular repair, thereby offering new possibilities for treating conditions involving mitochondrial dysfunction.

Methods

Nanoparticles Synthesis and Characterisation: Gold nanoparticles will be modified with metal complexes tailor the nanoparticle photophysical properties based on light excitation and down-upconversion used in photobiomodulation experiments. Multi-shell nanoparticle approaches with upconverting nanoparticles will also be used.

Photobiomodulation: 2D mixed co-cultures of human neural cell lines and animal astrocytes will be established in cell culture plates. Electrophysiological recordings and morphological analysis will be performed and cellular uptake and mitochondrial localisation will be studied together with mitochondrial function.

Optical characterisation: Light delivered to the cell culture plates and at mitochondrial levels will be determined.

References

[1] Yang B, Xu J, Li Y, Dong Y, Li Y, Tucker L, et al. J Biophotonics 2020;13. https://doi.org/10.1002/JBIO.201960117.

[2] Stevens AR, Hadis M, Milward MR, Ahmed Z, Belli A, Palin WM, et al. Https://HomeLiebertpubCom/Neu 2022. https://doi.org/10.1089/NEU.2022.0140.

[3] Zha S, Wong, K. L Homayoun All, A, ACS Nano 2024, 18, 1820–1845. https://pubs.acs.org/doi/10.1021/acsnano.3c10674?ref=recommended

[4] L. S. Watson, J. Hughes, S. T. Rafik, S.T., A. R. Muguruza, P. M. Girio, G. Rochford, G, A. J. MacRobert, N. J. Hodges, E. Yaghini, Z. Pikramenou Nanoscale, 2024, 16, 16500–16509. https://doi.org/10.1039/D4NR01901F.