Biosensor technology Flashcards
What is the difference between data and information?
Data can be raw figures and facts that are not put in a context, while information is data that is structured and put in a context
What is the definition of a biosensor?
A self-contained integrated device that can provide specific quantitative analytical data and uses a biorecognition element
What are the components of a biosensor?
Biorecognition element: enables specific recognition of the analyte
Interfacial component: facilitates immobilization of the bioreceptor and prevents unspecific binding of analyte
Transducer: converts the recognition event into a measurable signal
List some biorecognition elements
- Antibodies
- Enzymes
- DNA
- Aptamers
- Peptides
- Organelles
- Cells
List some transducer technologies
- Surface Plasmon Resonance
- Fluorescence
- Colorimetric
- Amperometric
- Potentiometric
- Piezoelectric
- Calorimetric
What are some differences between a biosensor and a bioassay?
An assay is an analytic procedure for quantitatively assessing the presence, amount or activity of a target. Uses BRE and is never an isolated process
What are some advantages of a biosensor compared to a clinical lab?
From a biosensor you can get real-time information and point of care. It is easier to obtain multi-time-point data.
What is a biorecognition element (BRE)?
Interactions between the recognition element and the analyte
Why does affinity matter for a affinity-based BRE?
A higher affinity, which means lower dissociation constant, of the bioregocnition for the analyte results in a larger sensor signal for a given analyte conc.
How does the turnover (kcat) affect the sensor signal?
The turnover is the maximum number of chemical conversions of substrate per second.
A higher kcat results in more product and therefore a larger sensor signal
What is unspecific binding?
It is binding of anything else than the analyte to the sensor or binding of the analyte to other parts of the signal generating components of the transducer.
What do you have to consider about the sample that you will use?
You must take the sample matrix and the analyte into consideration. Some properties that you have to consider are:
- Analyte size
- Chemical properties of analyte
- Range of analyte conc
- Which specificity and selectivity is required
- Complexity of the sample
What is the specificity of a sensor what is important to. consider?
The specificity of a sensor is the ability to explicitly assess the analyte in the presence of other components. The affinity for the analyte must be much higher than for binding other molecules that can bind to the BRE.
For detection of multiple different analyte we need multiple BRE for the specific analytes
What is selectivity?
A sensor array is selective if it can discriminate between different substances in the sample
What is the limit-of-detection (LOD)?
The lowest conc. of a substance that can be distinguished from the absence of that substance within a stated confidence limit.
Y(LOD) = y(blank) + k*σ(blank)
k is usually 3
What is the limit-of-quantification (LOQ)?
More reliable analytical results are obtained when the conc. is above a higher limit, LOQ.
Y(LOQ) = y(blank) + 10*σ(blank)
What is the dynamic range of the sensor?
The ratio between the upper and lower detection limits. The lower limit is the LOD/LOQ and the upper limit is where the response deviates from the assumed calibration function, due to saturation of BRE.
How can you decrease the LOD/LOQ?
Use a BRE with higher affinity for the analyte. For an enzymatic BRE you can use a BRE with higher turnover (kcat). You can also reduce noise-lever of the sensor, so you decrease the 3*σ
How do you prevent saturation of BRE?
Use BRE with lower affinity for the analyte (large KD) or dilute the sample or increase the sensor surface area
What is the sensitivity of a sensor?
The slope of the linear region.
The steeper slope the higher the sensitivity is. This means that there is a better possibility to distinguish small changes in the analyte conc = resolution.
The resolution is the smallest detectable change in analyte conc.
What is sensor noise and what can cause it?
The noise is random variation of sensor output that are unrelated to the sensor input. The noise can arise from random processes in the sensor function from electronic noise in the readout equipment.
It is important to look at the signal-to-noise ratio. A high sensitivity and low noise level gives a high resolution
What is accuracy, precision and reproducibility?
Accuracy: closeness of the measurements to a specific value
Precision: closeness of the measurements to each other
Reproducibility: ability if the sensor to produce identical results whenever the same sample is measured more than once
How can one improve the reproducibility?
The main reason for poor reproducibility is manual handling. So minimize manual handling.
Factors that affect the sensor robustness are environmental changes (temp and storage conditions) and sample interference
What are the different transducer categories and what do they measure?
- Electrochemical: detects redox reactions. Enzymatic reaction that generates electrochemical active species
- Optical: detects changes in wavelength or intensity. Analyte that are either colored or fluorescent or labeled or analyte-binding induces a change in refractive index.
- Gravimetric: detects changes in mass or viscoelastic properties. The change in the resonance frequency of an oscillating senor surface when the mass changes upon analyte binding