Traditional antibodies are widely used in industry and academia but require the use of animals in their production and are estimated to waste up to $800 million/year due to inaccurate results. There is an increasing trend to replace these antibodies with “plastic” antibodies that are low-cost, very stable, and can be manufactured in bulk quantities. We offer a new biosensing platform utilising plastic antibodies that is compatible with both electrochemical detection and a novel thermal technique. The sensor platform can be tailored to any application: by altering the plastic antibody, different biological targets (from small molecules to cells) can be measured.
There is a growing market to develop tests for the straightforward, fast and low-cost detection of biomolecules. The recognition element in these tests is traditionally based on antibodies, which are expensive, relatively unstable and require the use of animals in their production. Polymers, or “plastic” antibodies, are able to mimic the properties of natural antibodies and are able to overcome these drawbacks. These synthetic antibodies, referred to as molecularly imprinted polymers (MIPs), are made by polymerizing vinylic monomers in the presence of a specific target . After removal of the target, a porous structure is obtained with imprints that have a high specificity towards the target.
Molecular imprinting technology is versatile and it is possible to tailor the polymer for specific targets; meaning it is possible to detect a wide range of biological targets from small ions to larger proteins, bacteria and cells. At Manchester Metropolitan University, MIPs are integrated into Screen-Printed Electrodes (SPEs) by mixing the imprinted polymer particles with screen-printing ink  and transferring it onto a substrate. This process is one of the most promising approaches for production of biosensors as it ensures rapid, accurate and low-cost (disposable sensors) in situ analysis and is easily integrated into portable devices. Printing can be done on a variety of polymer and metallic substrates and allows fine tuning of the sensor to the required application.
This novel procedure for the production of MIP sensors is very straightforward and has a high commercial potential. The SPEs, functionalised with the plastic antibodies, are incubated with the analyte and binding of targets to the polymer layer is reflected in temperature changes in the liquid above the electrode. The temperature changes are measured with a set up developed at MMU that analyses the transport of heat-flow through the samples, and this is used to determine the concentration of the analyte. This can be done with two different thermal methods, which are both patented and referred to as the Heat-Transfer Method (HTM) and Thermal Wave Transport Analysis (TWTA) [3,4]. The developed sensors are versatile and can be measured with other read-out strategies, such as optical methods (change in colour), gravimetry (extremely sensitive mass balance) and electrochemical techniques such as chronoamperometry [3, 4].
Antibodies are widely used in academia, health services and industry for the detection of biomolecules. A 2015 report stated that the market for antibodies in the United States was up to $2.5 billion per year and growing . Besides ethical concerns as antibodies are obtained from animals, they are expensive and unstable, which has an effect on reliability . The loss in time and resources from poorly characterised antibodies is estimated at $800 million per year, which does not take into account the waste of samples and false conclusions from experiments . MIPs are an emerging technology that are finding their first commercial applications; chromatography columns packed with MIP particles used for extraction can be obtained from companies such as Biotage and Sigma Aldrich .
Advantages of MIPs over antibodies include superior stability; MIPs can operate up to 100˚C and are stable in organic solvents and extremes of pH. In addition, they are prepared in bulk quantities and give consistent results, contrary to batch-to-batch variability observed in the case of antibodies. These recognition elements are polymers, which makes them fundamentally different to other high affinity synthetic receptors, including affimers (protein complexes) or aptamers (oligonucleotide or peptide-based).
We have developed a complete biosensor platform; this includes disposable polymer-functionalised electrodes as recognition elements (£1/sample cost) and using heat as a read-out technology. The latter is performed with a patented thermal device, which costs only £1000, is portable and can be brought on-site to perform measurements in real-time. Commonly, MIP sensors use optical methods such as chromatography coupled to a fluorescent detector or Surface Plasmon Resonance (as available by Biacore). Microcalorimetry is another thermal method, but this looks at the development of heat in the liquid and not at the thermal resistance at the solid-liquid interface. In addition, it requires sophisticated equipment that is not standardly available in labs. The measurement time of our biosensor platform is approximately 2 min/sample , which is similar to standard point-of-care tests. In the future, we foresee expansion to an array format that can target a variety of molecules at the same time, replacing the use of multiple traditional antibodies.
The unique advantage of using polymer antibodies is that they can be tailored for multiple applications. We have experience in measuring small neurotransmitters, bacteria, and even whole cells; ensuring the developed MIPs and sensor platform will appeal to a large audience. Because of the low cost of the developed method and ability to measure samples on-site, it is extremely suitable for screening purposes and is particularly useful in remote geographical areas and laboratories with limited resources. It is faster and cheaper (£1 per sample) than traditional ELISA antibody assays that are widely used in laboratories and the life science industry. In addition, there is the possibility to detect a wide variety of compounds in array format; such as determining various contaminants (heavy metal, pollutants, organic dyes) in wastewater.
The thermal detection is performed by automated software, is easy to use, and measurements can be directly transferred to other locations.
This project is a unique collaboration between chemists, biophysicists and engineers. We are now seeking additional academic partners, as well as industry partners, to further validate and develop our approach to ensure maximum uptake of the technology.
We are seeking partners from academia and industry for:
- Access to biological samples. We are particularly interested in blood or serum samples from patients with bacterial infections or irregularities in neurotransmitter levels.
- Engineering/software expertise. For this we are interested in additional support in the miniaturisation of the set up and development of an app that improves usability and can work alongside the sensor to transform the raw data into a value, such as a number (as with the glucose sensor) or a colour.
- Expertise in and/or equipment for high-throughput screening.
Users to implement the methodology to replace existing immunoassay tests. For this we offer both a licence to use the system in house or a contract service where measurement of samples is carried out within our lab.
The project partners from the UK (along with collaborators from The Netherlands) have more than 10 patents in the area of thermal detection with biomimetic receptors (which are shared in supporting information). In addition, the researchers are keen to develop new IP for specific applications that are not in the portfolio yet.
Antibody generation for research and development currently requires between one and five animals (including mice, rabbits, goats and primates) to be immunised and ultimately sacrificed for each batch. For every MIP that is produced for a specific target, we avoid the immunisation and subsequent sacrifice of these animals. In 2013, nearly 10,000 animals were used in the UK for the production of monoclonal and polyclonal antibodies . In The Netherlands, this number was greater than 25,000  – meaning there is high potential across Europe for a large reduction in animal use for antibody production. Since our polymer technology is extremely versatile and can be applied to a wide range of biomolecules, there is the possibility to directly replace the use of traditional antibodies for use in bioassays in the area of diagnostics, clinical applications (healthcare), and also throughout the food, chemical and pharmaceutical industries.
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