## 4 MIPs as Theranostic Platforms  
MIPs can also be employed as building blocks for advanced theranostic systems. The concept of theranostics is defined by integrating both diagnostics and targeted therapy in a single platform, which leads to enhanced therapy and simultaneous imaging. This novel approach brings significant advantages to drug delivery, such as real-time treatment monitoring, real-time surgical guidance, evaluation of disease prognosis, and drug biodistribution assessment [47, 48]. Given the versatility of MIPs, regarding the nature of the imprinted template, they can also be loaded with bioimaging markers. MIPs have become valuable tools, not only for therapeutic purposes, but also for diagnosing diverse pathologies. Among these, it has been reported that _Pseudomonas aeruginosa_ and _Helicobacter pylori_ infections can be diagnosed and treated using fluorescent MIPs by targeting specific biomarkers of the pathogens [48]. Oncology is particularly benefiting from the theranostic approach, due to the possibility of loading both cytostatic drugs and imaging compounds. This newly emerging field brings together two vital steps in cancer management guided drug delivery and optical imaging by targeting overexpressed glycans or surface receptors of the tumoral cells [48]. Imaging methods include any scanning techniques that provide two-dimensional images, such as fluorescence, luminescence, infra-red or Raman spectroscopy, magnetic resonance imaging (MRI), radionuclide-based imaging, computer tomography (CT), positron electron tomography (PET), electrochemical, ultrasound or X-ray technology [49]. MIP-based imaging provides highly efficient localization of tumors. Imaging agents include organic dyes, silica NPs, carbon nanodots, gold and silver NPs, radioisotopes, magnetic iron oxide NPs, rhodamine B, fluorescein isothiocyanate (FTIC), gold nanorods, \({}^{14}\)C-labelled acrylamide [49]. According to imagistic experts, the ideal imaging nanoparticle for clinical applications should be biodegradable or quickly cleared from the body, with no to low toxicity, and the ability to generate a strong imaging signal. The main issues with fluorescent imaging lie in the strength of the detected signal, which is directly related to the depth of the tumoral tissue of interest, and in the interference of autofluorescence coming from endogenous molecules. Therefore, one of the necessary characteristics of MIPs used in bioimaging includes the use of fluorophores that emit in the near-infrared (NIR) range, to facilitate deep tissular scanning, avoid autofluorescence, and acquire a strong fluorescent signal. Moreover, particles below 100 nm are preferred for in vivo imagistic purposes, mainly because smaller particles give higher resolution images [48]. In terms of the targeted delivery of therapeutical agents, MIPs can be designed for active or passive targeting. Active targeting implies the imprinting of a specific sequence, for example, an epitope that would specifically target an overexpressed biomarker, where the nanoMIPs would release their payload. For passive targeting, however, MIPs would have to exploit the EPR effect to reach the targeted tissue and unload the theranostic agents [48]. The application of MIPs in bioimaging is primarily focused on fluorescence techniques, due to their inherent benefits: low instrumental and operating costs and high resolution of scanned images. For this purpose, MIPs can be fabricated either by copolymerization of fluorescent monomers or loading of fluorophores. The resulting MIPs can be used for both the in vitro and in vivo study of viable cells, tissue imaging, and the assessment of drug biodistribution [48]. Quantum dots (QDs) or N-fluoresceinacrylamide-, indocyanine green-, or Cy5 NIR dye labelling are widely used for in vivo fluorescence imaging, whereas other materials have also been proven to be highly efficient, including iron or gadolinium contrast agents for MRI, 124I labelling for PET imaging [48,49].