Polymeric nanoparticles for molecular imaging

Abstract

Conventional imaging technologies (X-ray computed tomography, magnetic resonance, and optical) depend on contrast agents to visualize a target site or organ of interest. The imaging agents currently used in clinics for diagnosis suffer from disadvantages including poor target specificity and in vivo instability. Consequently, delivery of low concentrations of contrast agents to region of interest affects image quality. Therefore, it is important to selectively deliver high payload of contrast agent to obtain clinically useful images. Nanoparticles offer multifunctional capabilities to transport high concentrations of imaging probes selectively to diseased site inside the body. Polymeric nanoparticles, incorporated with contrast agents, have shown significant benefits in molecular imaging applications. These materials possess the ability to encapsulate different contrast agents within a single matrix enabling multimodal imaging possibilities. The materials can be surface conjugated to target-specific biomolecules for controlling the navigation under in vivo conditions. The versatility of this class of nanomaterials makes them an attractive platform for developing highly sensitive molecular imaging agents. The research community's progress in the area of synthesis of polymeric nanomaterials and their in vivo imaging applications has been noteworthy, but it is still in the pioneer stage of development. The challenges ahead should focus on the design and fabrication of these materials including burst release of contrasts agents, solubility, and stability issues of polymeric nanomaterials.

A neutral polydisulfide containing Gd(III) DOTA monoamide as a redox‐sensitive biodegradable macromolecular MRI contrast agent

“…This allows the agents to have significantly improved physicochemical and biological properties, including a two‐ to fourfold relaxivity increase due to the reduced molecular tumbling of Gd(III) chelates . Additionally, macromolecular MRI agents have been shown to have an enhanced tumor accumulation by the enhanced permeability and retention (EPR) effect, as well as a prolonged blood pool circulation . While macromolecular agents have been successful in preclinical studies, their translation into clinical application has been hindered owing to safety concerns arising from their ineffective excretion, which can cause the release and long‐term deposition of the toxic Gd 3+ ions .…”

Submicron polycaprolactone particles as a carrier for imaging contrast agent for in vitro applications

“…These are noninvasive techniques and allow the visualization of target tissues [4,5]. Various imaging technologies (Magnetic resonance, optical etc) depend on contrast agent to visualize the organ of interest [6]. Contrast agents could augment the efficiency of imaging techniques by highlighting the differences between tissues [3], without contrast agent such information-rich images would be unobtainable.…”

“…These particles have shown many potential benefits, such as, (i) they restrict the delivery of imaging agent to a small area thus reducing the systemic side effects (ii) they can deliver high payload of imaging agent at target site selectively (iii) they can travel through blood vessels and protect the encapsulated agent until delivery (iv) polymeric particles provide high surface area that allows the attachment of appropriate targeting agent and enhance the release properties (v) they can modify the biodistribution of active agent in controlled manner. Moreover, polymeric materials have the ability to encapsulate different contrast agents and active molecules in a single particle enabling multifunctional particles possibilities [6][7][8][9], with a capacity for targeted site imaging and delivery of therapeutic agents [8]. Standard process allow for the encapsulation of lipophilic molecules into a multitude of particulate materials, however their application to hydrophilic compounds encapsulation is limited due to uncontrolled leakage of entrapped compounds during the preparation process [10][11][12].…”

Polymeric Nanostructures for Imaging and Therapy

“…168 CT is one of the most popular imaging modalities in clinical settings. Nano-sized CT contrast agents have been developed by many research groups to increase the sensitivity of CT imaging.…”