With the development of molecular imaging and material science, single domain antibody (sdAb)-targeted imaging technology has attracted extensive attention in the academic area. Many sdAb-based tracers using either nuclear, fluorescent labels or nanobubble/microbubble have been heavily investigated pre-clinically and are currently making their way into the clinic. Armed with rich experience in the production of sdAb and non-invasive molecular imaging research, Creative Biolabs provides customized nano-tracer development services with various labels. We provide tailored imaging tools to support your research in different fields ranging from cancer, inflammation, tumor extracellular matrix, to checkpoint molecules and immune responses.
Nuclear molecular imaging requires the targeting moiety, in our case is a sdAb, to be labeled with a diagnostic radioisotope. The latter can either be a gamma-emitting isotope for single photon emission computed tomography (SPECT) or a positron-emitting isotope for positron emission tomography (PET). 99mTc-tricarbonyl reacts site-specifically with a genetically inserted C-terminal hexahistidine tag, which can also be used for purification purposes via immobilized metal affinity chromatography. Radiolabeling of proteins with other radiometals (such as 64Cu, 68Ga, and 89Zr for PET or 67Ga and 111In for SPECT) or radiohalogens (such as 18F and 124I for PET and 123/131I for SPECT) usually necessitates the use of a chelator for complexation or a prosthetic group for electrophilic substitution, respectively.
Different from radiolabeled imaging, fluorescence imaging requires the presence of a fluorescent label for sensitive detection. Though a wide range of fluorescent dyes are available for biotechnological purposes, for in vivo imaging applications, the choice of fluorophore is limited to those emitting in the near-infrared (NIR) region, and more specifically, those with a maximal excitation and emission wavelength between 650 and 900 nm. Commonly, hydrophilic (sulfonated) variants of cyanine dyes with a penta- or heptamethine chain are used, such as Cy5, Alexa Fluor 680, IRDye680RD, IRDye700DX or IRDye800CW.
Fig.1 Bioluminescence Imaging of Inflammation by decorated nanobubble. (Liu, 2019)
Active targeting rapidly and selectively enhances tumor accumulation and tumor retention. These processes could be also visualized and quantified in real-time with ultrasound. Ultrasound imaging makes use of sound waves which are reflected differently by different tissues and organs. Microbubbles are generally used as contrasting agents and sdAb mediated guidance can further aid in improving contrast at the desired location. Due to the micrometer size, the proteins targeted should be located in the vasculature of the tumor such as VCAM-1 and PSMA. The application of sdAb-targeted microbubbles is beneficial since it can provide safe, fast and inexpensive scanning together with relatively high-quality images.
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