What are molecularly imprinted polymers and how are they made?
The MIP Discovery Video Series gives an introduction to Molecularly Imprinted Polymers, explaining what they are, how they are made and their applications in medical diagnostics and healthcare. In this first instalment, Senior Scientist Rhiannon Johnson explains exactly what molecularly imprinted polymers (MIPs) are and how they can be manufactured. Rhiannon also discusses the techniques used to characterise MIPs at MIP Diagnostics.
Hi, welcome to the MIP Discovery video series. I am Rhiannon Johnson, a senior scientist here at MIP Diagnostics, and in today’s video I am going to be discussing exactly what molecularly imprinted polymers are and how they are made.
Molecularly imprinted polymers are unique types of polymers that are made around a specific molecule of interest to leave an ‘imprint’ in their structure. The most simple way to think about it, is taking a piece of modelling clay and molding it around your thumb – when you pull it out there is a specific thumb print that is unique to your thumb. That is exactly how molecularly imprinted polymers work.
MIPs are often referred to as synthetic antibodies because they work in a very similar way. Their binding pocket is highly specific to the molecule of interest and has an extremely high affinity. They can be used in various applications such as in-vitro diagnostic devices, environmental sensors or for sequestering of a compound of interest.
MIPs were first developed almost a century ago, and since then various types of MIP have been created. The first types of MIP is what we call a bulk polymer. This is where a selection of monomers and a cross linker combine with a template in solution, and the polymerization is then initiated using UV radiation or heat. Once the block polymer is created it is essentially a large block of polymer which is then ground and sieved down to release the template molecule and to also make the MIPs a more uniform size.This method is relatively simple, however the griding process is very labor intensive and quite wasteful of materials.
Since bulk polymers, other techniques have been developed to enable better control over the MIPs that are produced. Suspension, emulsion, and precipitation polymerization all create spherical polymers with a more uniformed shape and size. In these methods, the functional monomers are suspended in solution with a suspending agent to stop the particles clumping together. The template molecule, cross-linker and other additional elements such as surfactants and progens are added to optimize the polymerization process. When the template is removed the remaining MIPs are of a consistent spherical shape and the binding pockets are specific to the target of interest.
MIPs produced using these methods are typically in the uM scale, however the demand for smaller MIPs for applications such as in-vitro diagnostics has led to the development of another method – solid phase synthesis. MIP Diagnostics proprietary solid phase synthesis method gives rise to nanoMIPs, that are uniform spheres typically under 60nM in size with discreet binding sites.In this method, the template molecule is suspended on a solid phase support such as glass beads. A mixture of pre-selected monomers and cross linkers are then added and begin to self-assemble around the target analyte via a range of interactions. These include hydrogen bonds, Van der Waals forces, electrostatic and hydrophobic interactions. Free radical polymerization is then initiated followed by a series of temperature-controlled elution steps to release the nanoMIPs from the template.
nanoMIPs are uniform in size and shape and offer a number of other unique benefits. They are very robust and can perform in extreme temperatures, pressure and pH. In fact, MIP Diagnostics have sent MIPs into space and tested them on their return – they performed in exactly the same manner as before their trip!
Another feature of nanoMIPs when compared to traditional affinity reagents such as antibodies is their supply security. It also means they offer excellent lot-to-lot consistency, making them an ideal alternative to antibodies and other affinity reagents.
A common question we often get asked at MIP Diagnostics is how we characterize our nanoMIPs. Firstly, we check the size of our MIPs using nanoparticle tracking analysis on a representative sample of each batch. We also measure affinity to the target using SPR. To test temperature stability, we can also autoclave our nanoMIPs to over 120 degrees C and test them pre- and post the autoclave cycle.
Thanks for watching this introduction to molecularly imprinted polymers. To learn more about the applications of MIPs remember to check out the other videos in our Discovery series, and please get in touch to discuss your specific projects with our team.