The advancement of human serum albumin-based molecular probes for molecular imaging.

Human serum albumin (HSA) is an abundant protein in blood and tissue fluids and has been used as a carrier for drug delivery. HSA can improve the pharmacokinetic profiles of drugs, such as extending the blood half-life of existing drugs and reducing toxic side effects. At the same time, more and more molecular imaging probes conjugated or fused with HSA have been studied to achieve higher specificity and better pharmacokinetic performance. These molecular probes can be attached to HSA covalently or non-covalently. They can also be fused with HSA as a fusion protein or coupled with HSA in vivo. Importantly, HSA conjugated probes have been applied to many imaging modalities such as the single photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), positron emission tomography (PET) and optical imaging alone or in combination with more than one modality. Besides in vivo molecular imaging, HSA conjugated probes can be used for molecular therapeutics, image-guided therapy, such as photodynamic imaging and photodynamic therapy (PDI/PDT). Some potential problems also need to be considered when using of HSA based probe strategy which are discussed in detail in the paper. Overall, HSA based probe design represents a very useful and powerful strategy for developing more molecular probes for theranostics of diseases.