20.109(F08):EL-KW Module3

The Problem of Drug-Resistant Staff
Methicillin-Resistant Staphylococcus aureus, or MRSA, is form of Staphylococcus aureus. Infection with MRSA can cause painful skin and soft tissue conditions and, if untreated, blood infections or bacterial pneumonia. Hospital-acquired MRSA (HA-MRSA) is increasingly common due to lack of following sterile procedures, the great number of open wounds/medical procedures, and a higher number of immuno-compromised patients. Approximately 31.8 MRSA infections per 100,000 people were estimated to have occurred in 2005, translating to 94,360 total infections. 86% of these were hostpial-acquired.

Currently, MRSA is detected in hospitals after a patient becomes infected by performing analysis on a tissue sample. Due to the scope of the MRSA problem, research is being done to develop increasingly faster detection methods. The most reliable method of MRSA detection by cell culture, but this process takes 1-2 days. New techniques involve the use of chromatography or genetic tests.

Biological Sensors
Ideally, the presence of MRSA could be detected in hospitals before patients became infected, in order to control the spread of the bacteria. Biological sensors are being developed for a number of purposes and could potentially be applied to MRSA detection in hospitals.

One type of sensor involves an electronic signal. Protein is bound to an electrode surface, and the ligand is modified to have a charged particle on it. The proximity of the particle to the electrode affects the electrode's conductivity. If the protein moves when bound to its antigen, then the charged particle will move as well, changing the conductivity of the electrode and creating a detectable signal.. This type of biological sensor could potentially be applied MRSA detection.

Electronic Sensing of Staff Binding
S. aureus can bind to plasma fibronectin. Fibronectin is an elastic and flexible protein that can stretch up to 4 times its relaxed length. Human fibronectin has also been shown to demonstrate hinge motion upon binding to.  This hinge motion could be capitalized upon for use in a bioelectronic sensor, as described above.

If fibronectin proteins were modified to bind directionally to gold, and also modified to have a charged component, then these modified fibronectin proteins could be used in a bioelectronic sensor like the one described above. Binding to S. aureus would induce a conformational change in fibronectin, bringing the charged particle closer to or further from the gold electrode.

Some of the design issues would include:

- the addition of a gold affinity pocket and the charged tag would have to not interfere with fibronectin-S.aureus binding.

- the movement of the charged tag relative to the gold electrode upon binding would have to be characterized

- the amount of unspecific fibronectin binding would have to be characterized

Biosensor Background Articles
Fluorescent Proteins as Biomarkers and Biosensors

Biomolecule immobilization in biosensor development: tailored strategies based on affinity interactions. <--- restricted access

Reagentless optical biosensors for organic compounds based on auto-indicating proteins.

Protein Engineering and Electrochemical Biosensors, Book Chapter

Protein hinges for bioelectronics

Biosensor technology: Technology push versus market pull

[http://www.lsbu.ac.uk/biology/enztech/biosensors.html What are biosensors? ]

Fibronectin Binding
Fibronectin binding to Integrin(Elasticity of Fn type3)

Dynamics of the interaction between a fibronectin molecule and a living bacterium under mechanical force

Fibronectin binding to Staphylococcus aureus

Hinge bending within the cytokine receptor superfamily revealed by the 2.4 A crystal structure of the extracellular domain of rabbit tissue factor

Fibronectin Structure

Crystal structures of fibronectin-binding sites from Staphylococcus aureus FnBPA in complex with fibronectin domains

Bioelectronics and Hinge Bending
Design of Bioelectronic Interfaces by Exploiting Hinge-Bending Motions in Proteins

Fibronectin Gold Adhesion
Fibronectin adsorption on gold, Ti-, and Ta-oxide investigated by QCM-D and RSA modelling

Force Microscopy Studies of Fibronectin Adsorption and Subsequent Cellular Adhesion to Substrates with Well-Defined Surface Chemistries