Application of Molecularly Imprinted Polymers in POC Diagnostics

Standard disposable point-of-care diagnostic (POCD) devices are making a positive impact on patient-based healthcare settings worldwide. These devices are convenient and economical, and they provide rapid results. Both clinicians and patients use them to diagnose a range of conditions. But in certain situations, these diagnostic devices have limitations.

For example, the short shelf life of these devices has proven to be problematic in the field, where keeping these products refrigerated in transport and storage is challenging. Another potential problem with some point-of-care testing devices is their inability to withstand harsh chemical conditions, such as extreme changes in pH, saltwater, or high concentrations of organic solvents.

Novel and Flexible Sensing Elements in POCD Devices

Molecularly imprinted polymers (MIPs) are innovative polymer structures that can maintain stability both at room temperature and in challenging environments. They also mimic biological sensing elements such as antibodies and receptors. And due to their low-cost materials, they are inexpensive to manufacture. 

In point-of-care diagnostics, MIPs are highly versatile and have been developed for diagnostic biosensors and assays that cover several diseases. Because they aren't based on antibodies or other biological elements, they can be tailored for relatively high selectivity and specificity.

Molecularly imprinted polymer nanoparticles, in particular, are even more selective and specific, since they contain only one binding site for a target molecule such as an enzyme or a protein. Nanoparticles such as these have been proven to provide the single-molecule sensitivity needed for high accuracy in diagnostic testing. Another advantage of MIP nanoparticles is that they can be attached to a solid substrate, as for a sensor.

How Molecular Imprinting Technology Works

In the past few decades, molecular imprinting technology (MIT) has been added to an assortment of techniques in which synthetic materials with biomimetic properties have been produced. It has been described as devising a molecular lock to match a molecular key.

The method starts with an impression that is created in a gel or solid. The size, shape, and function of this impression correspond to that of a template molecule, which has been formed during polymerization. This results in a synthetic receptor that is able to bind to a target molecule and fits into the binding site with specificity and affinity.

Recent Research Examples of MIPs for POC Diagnostics

In the past few years, researchers have developed sensors that incorporate MIPS for rapid detection of several conditions. The success of using MIPs in sensors can be attributed, at least in some part, to MIPs' good reproducibility and ease of control of film thickness in the detection device.

These polymer structures have used in the detection of cardiovascular conditions with excellent results. For example, a low-cost POCD device was developed to detect myoglobin, a protein marker for Acute Coronary Syndrome. Another example was the detection of cardiac troponin T for myocardial infarction using an inexpensive and quick POC device.

Other MIP-based sensors have been developed for sepsis markers with success. This is an essential development since sepsis is one of the primary causes of death among newborns worldwide. There is a great need for economical detection devices at the point-of-care where refrigeration is not usually available in transport and on-site.

Challenges of MIPs

Assays incorporating MIPs are proving to be a reasonable alternative to traditional diagnostic tests in point-of-care settings where conditions are less than forgiving. But at least a few practical difficulties related to MIPs still need to be addressed.

One problem is template leakage that occurs following MIP preparation. The template may be challenging to extract completely, and the remaining parts of it may gradually release from the MIP during its use. The leaked portions of the template interact with target sensing and negatively affect the accuracy of detection.

Another challenge is the lack of a platform for the assay formats and development for MIPs. If these polymer structures could be generalized and cataloged, they are more likely to be readily adopted by the scientific community.

Future Trends

As with other techniques of in vitro diagnostic device development, nanotechnology will ultimately change how molecularly imprinted polymers are created. It is a trend that will most likely shift the production of MIPs from a bulk process toward the development of MIP nanoparticles. These nanoparticles are easily integrated into current assay formats. Composite structures that use other nanomaterials such as quantum dots (microscopic semiconductor particles) or various nanoparticles containing gold, silica, or other materials may be combined with MIPs to aid in new ways of detection as well as improved sensitivity.

Another trend is towards homogeneous assays using MIPs. They usually do not require washing and separation steps in sample processing, which would simplify analysis and reduce the likelihood of errors in measurement.

Conclusion

The continued refinement of molecularly imprinted polymers holds enormous promise in introducing tools that provide inexpensive, rapid, and sensitive detection of serious medical conditions in demanding environments where the need is greatest.