The development of molecularly imprinted polymer (MIP) nanomaterials for disease biomarker detection has emerged as a promising approach in diagnostics, offering high specificity, stability, and cost-effectiveness. These synthetic receptors mimic natural molecular recognition systems, enabling selective binding of target biomarkers such as proteins, nucleic acids, and small molecule metabolites. Advances in imprinting strategies and nanomaterial integration have expanded their utility in point-of-care diagnostics and multiplexed detection platforms.
Imprinting strategies vary depending on the biomarker class. For proteins, epitope imprinting is widely used, where a short peptide sequence representing the target protein's binding site is imprinted instead of the whole protein. This approach circumvents challenges associated with the size and structural complexity of proteins. Alternatively, surface imprinting techniques create cavities on nanomaterial surfaces, preserving the protein's native conformation. For nucleic acids, MIPs are designed to recognize specific sequences or structural motifs, such as single-stranded DNA or microRNA. Small molecule metabolites, due to their lower molecular weight and structural simplicity, are imprinted using bulk polymerization or sol-gel methods, often with covalent imprinting to enhance specificity.
The integration of MIP nanomaterials into point-of-care diagnostic formats has been demonstrated in lateral flow assays, electrochemical sensors, and microfluidic devices. Lateral flow assays incorporating MIPs have achieved detection limits comparable to antibody-based tests, with the added advantage of robustness under harsh conditions. Electrochemical sensors leverage the conductivity of MIP nanomaterials for label-free detection, enabling real-time monitoring of biomarkers. Microfluidic platforms combine MIPs with miniaturized detection systems, facilitating rapid analysis of complex biological samples. Multiplexing capabilities have been enhanced by spatially patterning different MIPs on sensor arrays or using distinguishable nanomaterials, such as quantum dots or magnetic nanoparticles, for simultaneous detection of multiple biomarkers.
Despite these advances, challenges remain in imprinting large biomolecules. The flexibility and conformational variability of proteins can lead to heterogeneity in binding sites, reducing MIP specificity. Additionally, the hydrophilic nature of biological fluids can interfere with hydrophobic interactions critical for MIP recognition. Strategies to address these challenges include incorporating hydrophilic monomers, using zwitterionic polymers to resist nonspecific adsorption, and optimizing crosslinking density to balance cavity rigidity and accessibility.
Clinical validation studies have demonstrated the potential of MIP nanomaterials in real-world applications. For example, MIP-based sensors for cardiac troponin I achieved a detection limit of 0.2 ng/mL in serum, with a linear range covering clinically relevant concentrations. In another study, MIPs targeting prostate-specific antigen showed 95% concordance with ELISA results in patient samples. For small molecule detection, MIP nanomaterials have been validated for therapeutic drug monitoring, such as imprinted polymers for theophylline with recovery rates exceeding 90% in blood samples.
The robustness of MIP nanomaterials in complex matrices has been further validated in studies involving saliva, urine, and whole blood. For instance, a MIP-based sensor for cortisol in saliva demonstrated a correlation coefficient of 0.92 with LC-MS measurements. Similarly, MIPs for glucose detection in whole blood showed less than 5% interference from common metabolites like ascorbic acid and uric acid.
Future directions include improving imprinting efficiency for larger biomarkers, enhancing signal transduction mechanisms, and scaling up production for commercialization. The combination of MIP nanomaterials with emerging technologies, such as wearable sensors and artificial intelligence-based data analysis, could further revolutionize disease biomarker detection. With continued development and validation, molecularly imprinted polymer nanomaterials are poised to become a cornerstone of next-generation diagnostic systems.