Mark Howarth lab

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Bionanotechnology against Cancer

Bionanotechnology involves manipulating and modifying components of living organisms, to generate tools on the 1-100 nanometre scale with new desirable activities. Inspired by extraordinary molecular features from the natural world, our goal is to develop new biological and chemical approaches for disease diagnosis and fundamental  insight into how cells function.

Circulating tumour cells and engineering new antibody technologies

Capturing the circulating tumour cells (CTCs) from blood samples is one of the most promising approaches to enable early diagnosis of cancer. CTC testing is already allowing rapid feedback on how a patient is responding to therapy. Existing magnetic CTC isolation approaches only capture the cells expressing high levels of tumour marker. We have shown how improving antibody affinity and cholesterol loading makes it possible to recover low-expressing cancer cells. 

To improve further the isolation of CTCs, we are developing antibody technologies with new protein architectures and modes of target binding. This includes a novel class of antibodies/affibodies that form covalent bonds to endogenous protein targets. Even high affinity antibodies generally dissociate from their targets on the time-scale of minutes. Antibodies that do not dissociate from their targets should reduce the detection limit for soluble or cell-associated tumour markers.

 

Fluorescent Nanoparticles to analyse receptors at the single molecule level

Most biological experiments observe the behaviour of hundreds to millions of molecules. Being able to study molecules one at a time can give dramatic new insights into the cell's function. We have developed new ways to target quantum dots (QDots) and conjugated polymer dots (Pdots), ultra-bright nanoparticles, to study cell surface receptors. In particular we have used QDs to understand the LDL receptor, which has a central role in preventing heart disease and may also be important in the capture of lipid-soluble antigens to activate the anti-tumour immune response.


		
 

Nanohubs and the limits of protein interaction strength

The interaction of streptavidin with biotin is one of the strongest non-covalent interactions in nature. Streptavidin is a central tool for assembly and purification in biological research, as well as showing success in radiotherapy clinical trials. We were able to make a version of streptavidin with 10-fold slower biotin dissociation. We have been investigating this interaction to understand mechanical strength of protein-ligand interactions by single-molecule force spectroscopy with Vincent Moy in Miami and by crash-testing using bacterial DNA pumps with David Sherratt in this department. We are also developing the use of streptavidin as an ultra-stable hub for nanoassembly.

 

Designing protein superglue from bacteria

Peptides are central to protein analysis and isolation, but they are also “slippery”- it is hard to get a strong grip on them. We have harnessed and adapted an amazing feature of the bacterium Streptococcus pyogenes, which can cause the "flesh-eating disease" necrotizing fasciitis. This synthetic biology approach enabled us to achieve an irreversible covalent bond between genetically-encoded protein (SpyCatcher) and peptide (SpyTag) partners; this bond is stable over time, at high temperatures, and against the forces in biological systems (blood flow, cell migration, molecular motors). We are extending the scope of this reaction, to be able to investigate force generation inside the cell and to create new protein architectures for CTC isolation.

 

Contact me for further information about any of these projects, or to discuss the possibility of working on other projects in the area of bionanotechnology / chemical biology.

 

 Copyright © 2014 Mark Howarth. All rights reserved.