Enzyme activity is often a key measurement to make in a biological sample

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Many disease states can be indicated by the relative activity of a particular enzyme and many drugs are targeted to up- or down-regulate enzyme activity. Enzymes are now also being used beyond biomedical science, in industrial processes, being synthetically modified to target the degradation and recycling of plastics and production of fuels. Therefore, we aim to develop simple, accurate enzyme activity assays that can ultimately be (1) multiplexed to detect several different enzymes at once and (2) miniaturised into high-throughput devices. These assays are based on the modification of the surface of luminescent nanomaterials such as "quantum dots" to create enzyme sensors. For example, a peptide bearing a terminal dye can be bound to the surface of a quantum dot nanoparticle. The dye fluorescence is excited by the luminescence from the nanoparticle (via resonant energy transfer). On cleavage of the peptide by a target enzyme (a hydrolase), the dye is dissociated from the nanoparticle and the dye emission is quenched - measuring the rate of this quenching gives an indication of enzyme activity. Such nanotechnologies have been demonstrated for the sensing of several different proteases (protein cleaving enzymes), and in our work we hope to demonstrate that the technique is extensible to luminescent nanomaterials beyond quantum dots, that display new and exciting optical properties (e.g. the very sharp emission of quantum plates for high degrees of multiplexing, or upconverting lanthanide nanoparticles for sensing in highly scattering media). We will generate novel surface chemistries of these nanoparticles to produce the best sensing results. The PhD student will synthesise enzyme reactive nanoparticles that operate on the mechanism described above, starting with quantum dots and moving on to explore quantum nanoplatelets and upconverting lanthanide nanoparticles as novel alternatives. The surface chemistry will be designed to measure the activity of enzyme Matrix Metalloprotease 1 (MMP1) or human pancreatic lipase - blood biomarkers of markers of liver fibrosis and pancreatitis respectively. The student will demonstrate proof-of-concept of sensing in blood, and begin working to incorporate the nanoparticles into practical assays. This will be undertaken with collaborators in biomedical engineering (microfluidics and nanofabrication) and medicine. During the project, the student will gain practical skills in nanomaterials synthesis, modification and characterisation; and will have opportunities to apply their modified nanoparticles to a range of related projects. For example, it will be of interest to investigate (with collaborators) if the developed nanotechnology can be made compatible with high throughput screening of modified and evolved enzymes for treating plastic waste, as an alternative application. The work fits within EPSRC themes of Healthcare Technologies, Physical Sciences and Manufacturing the Future (areas include: Chemical Biology, Analytical Science, Sensors and Instrumentation). We aim to provide tools that will contribute to the ongoing paradigm shift in medicine towards stratified/personalised treatment. By enabling the rapid screening of enzyme activity in a near-patient format, diagnosis, drug selection, and dosage monitoring can be improved. During the course of this work we will also advance our understanding of nanoparticle surfaces and their interaction with biological agents such as enzymes. This new knowledge will be disseminated widely, via work with collaborators, in the scientific literature and at relevant conferences.