Point-of-care sensors for therapeutic antibotic monitoring

Antibiotics are some of the most effective drugs saving uncountable lives since their introduction more than 70 years ago. However, drug-resistant bacteria are rapidly spreading and posing one of the gravest threats to human health. Furthermore, the evolution of resistance is outpacing the discovery and development of new antibiotics. Therefore, stewardship of our existing and precious antibiotics is urgently needed. The objective of this thesis is to develop point-of-care sensors for therapeutic antibiotic monitoring, particularly for vancomycin, which not only allow prudent antibiotic use, but very importantly lead to better health outcomes associated with lower healthcare costs. The sensor development is approached with two different detection techniques: I) colourimetric detection via visible spectroscopy, and II) nanomechanical detection via cantilever array sensors. I) The thesis’ main focus was to develop a colourimetric vancomycin assay that builds on the point-of-care bench top device ‘Pelorus’ of our industrial partner – Sphere Medical Ltd. in Cambridge, UK. The assay could be successfully developed and benchmarked to UCLH’s gold standard. It includes extraction from whole serum prior to a labelling reaction that permits subsequent quantification via visible spectroscopy. Free and bound drug concentrations can be quantified within minutes, which is crucial for the determination of antibacterial activity and an advantage over current routine assays. Furthermore, the labelling reaction produced a novel molecule, which was structurally characterised. The developed assay could be patented with recent PCT entry. II) Nanomechanical detection of active free antibiotic concentration in human serum via cantilever arrays could be demonstrated. Combined with equilibrium theory, it led to better understanding of the biophysical mode of action improving treatment, dosage and drug discovery. It could be published in an article in Nature Nanotechnology. This project has been early stage proof-of-concept work. The next step towards commercialisation should involve clinical evaluation from whole blood and may further extend to multi-analyte and hand-held sensors for therapeutic monitoring

Sensing surface PEGylation with microcantilevers

Polymers are often used to modify surface properties to control interfacial processes. Their sensitivity to solvent conditions and ability to undergo conformational transitions makes polymers attractive in tailoring surface properties with specific functionalities leading to applications in diverse areas ranging from tribology to colloidal stability and medicine. A key example is polyethylene glycol (PEG), which is widely used as a protein-resistant coating given its low toxicity and biocompatibility. We report here a microcantilever-based sensor for the in situ characterization of PEG monolayer formation on Au using the “grafting to” approach. Moreover, we demonstrate how microcantilevers can be used to monitor conformational changes in the grafted PEG layer in different solvent conditions. This is supported by atomic force microscope (AFM) images and force–distance curve measurements of the microcantilever chip surface, which show that the grafted PEG undergoes a reversible collapse when switching between good and poor solvent conditions, respectively

Thoughts on an education

Research in nanoscience and nanotechnology has grown rapidly in recent years and has provided numerous scientific and technological breakthroughs. The field has also, in some sense, changed the way in which a research topic can be tackled, unconstrained by traditional scientific disciplines. However, what effect have the developments in research had on the curriculum being taught in universities? And what sort of education do the nanotechnologists of the future need to succeed? Nature Nanotechnology asked a range of current, or recently graduated, masters and PhD students about their own experiences, and what, if anything, they would change about the current education system.3 page(s

Surface-stress sensors for rapid and ultrasensitive detection of active free drugs in human serum

here is a growing appreciation that mechanical signals can be as important as chemical and electrical signals in biology. To include such signals in a systems biology description for understanding pathobiology and developing therapies, quantitative experiments on how solution-phase and surface chemistry together produce biologically relevant mechanical signals are needed. Because of the appearance of drug-resistant hospital ‘superbugs’, there is currently great interest in the destruction of bacteria by bound drug–target complexes that stress bacterial cell membranes. Here, we use nanomechanical cantilevers as surface-stress sensors, together with equilibrium theory, to describe quantitatively the mechanical response of a surface receptor to different antibiotics in the presence of competing ligands in solution. The antibiotics examined are the standard, Food and Drug Administration-approved drug of last resort, vancomycin, and the yet-to-be approved oritavancin, which shows promise for controlling vancomycin-resistant infections. The work reveals variations among strong and weak competing ligands, such as proteins in human serum, that determine dosages in drug therapies. The findings further enhance our understanding of the biophysical mode of action of the antibiotics and will help develop better treatments, including choice of drugs as well as dosages, against pathogens