Nanomaterials in Imaging and Diagnostics

Introduction

Nanomaterials are the essential part of nanotechnology which have been extensively studied by the scientists for its use in the field of nanomedicine for imaging, diagnosis and treatment (Rani et al., 2019). Nanomaterials are defined as the substances whose at least one external dimension measures 100 nanometers or less (Turney, 2009). Nanomaterials offer properties like enhanced diagnostic specificity, increased blood circulation time and organ specific delivery (Patra et al., 2018).

Nanomaterials can be functionalized or conjugate with variety of agents that would increase their compatibility in a biological environment, can enhances targeting capability and better cellular uptake in desired cancerous cells. Physiochemical properties of nanomaterials like size and shape, texture of surface, atomic arrangement, composition of materials, charge of particles and system in which they are suspended are the most important consideration for better design and formulation of nanoparticles.

Bio-imaging or medical imaging is a method to visualize into the body non-surgically to gain predictive data about the affected region. From last 20 years, nanomaterials-based drugs have altered the way of bio-imaging (Subhra et al., 2021). Figure 1 depicts the general considerations of designing nanomaterials used for imaging.

Figure 1.

General considerations of nanomaterials used in imaging

Recent advance in bioimaging is multimodal imaging, it overcomes the limitations of existing bioimaging (visualizing one organ at a time). Multimodal imaging allows simultaneous production of signals for several imaging techniques at a time. Multimodal imaging is defined as combination of images from several modalities to form one combined image, it allows combinative structure and efficient information about the disease. To overcome the disadvantages associated with individual modality, multi-modal imaging systems such as Proton Emission Tomography-Computed Tomography (PET-CT), Computed Tomography-optical Proton Emission Tomography-Magnetic Resonance Imaging (CT-oPET-MRI) are currently in clinical usage (Subhra et al., 2021).

Every diagnostic method is designed to generate accurate results in early stage of disease. For this high quality, sensitive, specific imaging probe are required. Contrast agents, also known as imaging probes, are the substances that aids in visualization of X-rays or other imaging tools’ interactions with the body for a definite period of time. They assist in enhancement of the diagnostic value of the imaging techniques. Prior to imaging, these agents are administered in the body which makes certain body tissues to be seen different than without introduction of the contrast media. It helps the doctors to diagnose the medical conditions by increasing the organ or tissue visibility (Richard Heller, 2022). The prerequisite properties for contrast agents are (Rani et al., 2019):

• 1.

  It must be stable in physiological environment in different pH, temperature and ionic strength.

• 2.

  It must keep colloidal solution stable with proper dispersion.

• 3.

  It must have high retention time in bloodstream to achieve high quality imaging.

• 4.

  Along with high retention it needs to be excrete from body via suitable route to minimize toxicological events.

• 5.

  It must have proper retention time within specific organ or location with proper contrast to ensure high quality imaging.

• 6.

  It must be biocompatible to minimize adverse reactions.

Figure 2 shows types of nanomaterials.

Figure 2.

Types of nanomaterials