A Novel Tumor Targeting Drug Carrier for Optical Imaging and Therapy

Abstract

Human serum albumin (HSA), a naturally abundant protein in blood plasma and tissue fluids, has an extraordinary ligand-binding capacity and is advocated as a drug carrier to facilitate drug delivery. To render it tumor targeting specificity, we generated a recombinant HSA fused with the amino-terminal fragment (ATF) of urokinase, allowing the fusion protein to bind to urokinase receptor (uPAR), which is shown to have a high expression level in many tumors, but not in normal tissues. To test the efficacy of this bifunctional protein (ATF-HSA), a hydrophobic photosensitizer (mono-substituted β-carboxy phthalocyanine zinc, CPZ) was chosen as a cytotoxic agent. A dilution-incubation-purification (DIP) strategy was developed to load the ATF-HSA with this CPZ, forming a 1:1 molecular complex (ATF-HSA:CPZ). We demonstrated that CPZ was indeed embedded inside ATF-HSA at the fatty acid binding site 1 (FA1) of HSA, giving a hydrodynamic radius of 7.5 nm, close to HSA's (6.5 nm). ATF-HSA:CPZ showed high stability and remarkable optical and photophysical properties in aqueous solution. In addition, the molecular complex ATF-HSA:CPZ can bind to recombinant uPAR in vitro and uPAR on tumor cell surfaces, and was efficient in photodynamic killing of tumor cells. The tumor-killing potency of this molecular complex was further demonstrated in a tumor-bearing mouse model at a dose of 0.080 μmol / kg, or 0.050 mg CPZ / kg of mouse body weight. Using fluorescent molecular tomography (FMT), ATF-HSA:CPZ was shown to accumulate specifically in tumors, and importantly, such tumor retention was higher than that of HSA:CPZ. Together, these results indicate that ATF-HSA:CPZ is not only an efficient tumor-specific cytotoxic agent, but also an useful tumor-specific imaging probe. This bifunctional protein ATF-HSA can also be used as a drug carrier for other types of cytotoxic or imaging agents to render them specificity for uPAR-expressing tumors.

ROS-Responsive Mitochondria-Targeting Blended Nanoparticles: Chemo- and Photodynamic Synergistic Therapy for Lung Cancer with On-Demand Drug Release upon Irradiation with a Single Light Source

“…Thus, it is possible to develop a platform for combining ROS-responsive chemotherapy and photodynamic therapy with a single light source. Zinc phthalocyanine (ZnPc), a photosensitizer with high singlet oxygen quantum yield, is frequently used for photodynamic therapy 34, 35.…”

Binding and Anticancer Properties of Plumbagin with Human Serum Albumin

“…Remarkably, HSA possesses several amino acid residues, including Lys, Asp, Glu, and Cys. These residues are conveniently able to form complexes with targeting molecules such as antibodies and various overexpressed receptors . In terms of biomedical applications, HSA has an immense potential in the field of drug delivery.…”

Dual actions of albumin packaging and tumor targeting enhance the antitumor efficacy and reduce the cardiotoxicity of doxorubicin in vivo

“…30 A major challenge to embed DOX into ATF-HSA is that DOX has a strong tendency to Notes: DOX tends to form aggregates, hindering its embedding inside the carrier. The DOX aggregates can be dissociated by a simple dilution, and the dissociated DOX can then be loaded into HSA at a major drug binding site (Sudlow site I) at the subdomain IIA (located in the domain II, DII) and near W214 amino acid.…”

“…ATF has been used as a target agent for uPAR in a number of studies. 30,31 Therefore, ATF-HSA possesses dual properties: uPAR targeting by ATF and drug binding by HSA.…”