Cryogenic electron microscopy for native state analysis of nanoparticles in liquids

The success of a nanoparticle system designed for a specific application is contingent on controlling the interfacial chemistry (e.g. colloidal stability, overall size, etc). To truly understand this, we require approaches to probe and understand the interactions between nanoparticles and the environments they are dispersed in.

This project will focus on developing methods to characterise nanoparticles dispersed in liquids. Electron microscopy is ideally suited to the analysis of nanoparticles, with the required spatial resolution to investigate the size and structure of nanoparticles, and the associated analytical tools, energy dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies, which provide composition and bonding information at the single particle level. The limitation, however, is the vacuum level required in an electron microscope therefore necessitates dry samples. This project will utilise a biological sample preparation approach where nanoparticles dispersed in a liquid are frozen and then analysed in an electron microscope at cryogenic temperatures, with the analytical capabilities used to probe the interactions between different nanoparticles, and between the nanoparticles and components of the liquid media they are suspended in.

Two types of cryogenic (cryo-) electron microscopy will be investigated in this project; (scanning) transmission electron microscopy ((S)TEM) and focused ion beam scanning electron microscopy (FIB-SEM), with the limits of the techniques applied to frozen samples established. Rigorous characterisation of nanoparticles will enable understanding of their impact and prediction of behaviour. Two nanoparticle systems with biomedical applications will be used as model systems; for representative analysis this characterisation must be conducted in biologically relevant liquid media, and at the scale of the individual nanoparticle. The outcome of the project will be understanding the structure and dispersion of two model nanoparticle system when suspended in liquids, and the development and assessment of this nanoscale analytical approach, which can then be applied to further systems of importance.

This project will develop the use of cryogenic electron microscopy for the native state analysis of nanoparticles in liquids. This research will generate broad and significant impact across the four key categories of Economic, Knowledge, Societal and People.

Directly related to the biomedical application of the two systems to be examined in this project, economic benefits will be gained by nanoparticle manufacturers and related industries. Users of nanoparticles include academic groups (such as the University of Leeds research group led by Dr Olivier Cayre), and research associated with Centres for Doctoral Training (CDT) such as those based at (Complex Particulate Products & Processes), or associated with (Soft Matter and Functional Interfaces), the University of Leeds. These CDTs will provide the opportunity to interact with potential future industry collaborations; however the research in this proposal is primarily fundamental method development (and hence there are no letters of support from industry, as the project will focus on the model systems detailed). Looking forward, benefits to industry may be felt in pharmaceutical companies such as AstraZeneca, GlazoSmithKline and Pfizer, and to nanomedicine producers such as Shield Therapeutics, who develop ferric based therapies and phosphate binders, and CytImmune Sciences, who make targeted gold nanoparticle-based therapeutics. Beyond the scope of nano- or bio-medicine, the innovative methods will be applicable to the quantitative characterisation of nanoparticles in complex suspensions, with benefits to the fields of agrochemicals (Syngenta), petroleum additives (Infineum) and consumer goods (Proctor & Gamble).

There will be Knowledge benefits through the utilisation of the methodologies and approaches developed during this project. Current limitations in the nanoscale study of nanoparticles in liquids will be overcome, by capturing the nanoparticles of interest in the native state (i.e. frozen in place). The approach to appropriately freeze the samples and examine using electrons without causing damage is well established in the biological sciences (and was awarded the 2017 Nobel Prize for Chemistry), and this project will determine the limits of analytical (spatial, elemental) and three-dimensional (spatial, volume) approaches. This native state analysis will enable characterisation and understanding of systems in real-world use, extending beyond the design in the laboratory; thereby bringing nanoparticle applications to the general public.

Broadly, Societal benefits will be achieved through the implementation of the methodology on a variety of systems, thereby reducing safety concerns regarding nanomaterials for the general public. Specific benefits to healthcare relate to: the use of the developed analytical electron microscopy techniques to identify the nanoparticle systems most likely to yield positive results; with the systems used as therapeutics providing targeted treatments, therefore reducing side effects.

The People involved with this project will benefit from career development. As the Primary Investigator I will acquire expertise not only in my research area, but also as group leader managing research staff and students. I will also use this as an opportunity to engage with industry and the general public as the project progresses. I will cultivate a research environment that ensures the development of high quality skills and career advancement for the appointed postdoctoral researcher and PhD student. The high impact research conducted will result in quality publications and conference presentations, raising the international profile of all involved with the project.