Introduction

Developments in biomedical imaging enables the visualization, evaluation, and quantification of biological processes at the molecular and cellular levels in a noninvasive means, and shows great potential in the earlier diagnosis of diseases, on-going assessment of treatments, and optimization of disease therapeutic protocols, greatly encouraging the diagnosis of diseases. Imaging agents, such as fluorescent small molecules and imaging contrast agents are the core and foundation of biomedical imaging, which are employed to generate signals or enhance the signal contrast in targeted tissues. In the past decade, MOFs and COFs have been shown great potential for used as imaging agents and have been extensively investigated in this field.

Application of MOFs in Biomedical Imaging

In the past several years, owing to the facile functionalization, diversiform structures and compositions, and large porosities of MOFs, MOF-incorporated imaging techniques are widely used in optical imaging, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) imaging^[1].

• Optical Imaging: Optical imaging is a minimally invasive technique whereby light illumination is used to visualize tissue. In general, luminescent MOF materials are being extensively researched at the moment in the context of several optical imaging applications.

• CT Imaging: CT imaging provides a direct 3D visualization of the internal structures of a scanned object based on X-ray attenuation. The high-Z number elements such as iodine, barium, and bismuth in MOFs can be chosen as CT contrast agents. For example, a gold-nanoparticle-incorporated MIL-88 MOF as a multifunctional diagnostic agent to give high-quality CT scans.
• MRI: The signals of MRI provide precise anatomical-structure maps and help to detect diseases and other anomalies. Gadolinium-based small molecules are the most commonly used contrast agents; thus, Gd-based MOFs arose as logical MRI contrast agent candidates. To avoid toxicity concerns with Gd, some researchers have switched their attention to other metal-based MOFs such as Fe-based MOFs and Mn-based MOFs.
• PET imaging: PET relies on the accumulation of positron-emitting radionucleotides at target organs, which emit detectable gamma-ray photons on decay. Compared with other imaging techniques, PET imaging has better detection sensitivity in the picomolar range. MOFs with positron imaging radioisotopes are suitable choices for PET.

Application of COFs in Biomedical imaging

COFs have good photostability owing to the long-range crystal domain and eclipsed π-π stacking structure. In addition to, the tunable structure and constituent make it has adjustable fluorescence, functionalized surface chemistry. Therefore, COFs are used as potential agents for fluorescence imaging. Fluorescence imaging is a forceful technology for achieving accurate diagnosis and visualize therapeutic process. Fluorescence imaging is also employed to investigate the functions of biological molecules in an inherent microenvironment on account of its high sensitivity, noninvasiveness, rapid response capability, and real-time performance analysis. Some typical examples of use of COFs for fluorescence imaging are shown in Table 1^[2].

Fig.1 Two-photon and one-photon fluorescence imaging of TPI-COF incubated cells

What Can Alfa Chemistry Do

Alfa Chemistry has a profound research foundation in the field of biomedical imaging, and our high-quality MOFs and COFs work well in the biomedical imaging. Our professional technology team that can also provide customers various MOFs and COFs design and customization services, no matter what design ideas you have, we will implement them together with you. Alfa Chemistry will serve you with the most abundant experience and the most affordable price. If you have any problems, we will provide technical support for you. If you have special needs, we will develop a unique solution for you. Please don't hesitate to contact us.