Paired Agent Fluorescence Imaging of Cancer in a Living Mouse Using Preassembled Squaraine Molecular Probes with Emission Wavelengths of 690 and 830 nm

New methods are described for the construction of targeted fluorescence probes for imaging cancer and the assessment of tumor targeting performance in a living mouse model. A novel noncovalent assembly process was used to fabricate a set of structurally related targeted fluorescent probes with modular differences in three critical assembly components: the emission wavelength of the squaraine fluorochrome, the number of cRGDfK peptide units that target the cancer cells, and the length of the polyethylene glycol chains as pharmacokinetic controllers. Selective targeting of cancer cells was proven by a series of cell microscopy experiments followed by in vivo imaging of subcutaneous tumors in living mice. The mouse imaging studies included a mock surgery that completely removed a fluorescently labeled tumor. Enhanced tumor accumulation due to probe targeting was first evaluated by conducting Single Agent Imaging (SAI) experiments that compared tumor imaging performance of a targeted probe and untargeted probe in separate mouse cohorts. Although there was imaging evidence for enhanced tumor accumulation of the targeted probe, there was moderate scatter in the data due to tumor-to-tumor variability of the vasculature structure and interstitial pressure. A subsequent Paired Agent Imaging (PAI) study coinjected a binary mixture of targeted probe (with emission at 690 nm) and untargeted probe (with emission at 830 nm) into the same tumor-burdened animal. The conclusion of the PAI experiment also indicated enhanced tumor accumulation of the targeted probe, but the statistical significance was much higher, even though the experiment required a much smaller cohort of mice. The imaging data from the PAI experiment was analyzed to determine the targeted probe's Binding Potential (BP) for available integrin receptors within the tumor tissue. In addition, pixelated maps of BP within each tumor indicated a heterogeneous spatial distribution of BP values. The results of this study show that the combination of fluorescent probe preassembly and PAI is a promising new way to rapidly develop targeted fluorescent probes for tumors with high BP and eventual use in clinical applications such as targeted therapy, image guided surgery, and personalized medicine.

Targeting integrins for cancer management using nanotherapeutic approaches: Recent advances and challenges

Integrins are the main cell surface receptors and execute multifaceted functions such as the bidirectional transmission of signals (i.e., inside-out and outside-in) and provide communication between cells and their microenvironments. Integrins are the key regulators of critical biological functions and contribute significantly to the promotion of cancer at almost every stage of disease progression from initial tumor formation to metastasis. Integrin expressions are frequently altered in different cancers, and consequently, several therapeutic strategies targeting integrins have been developed. Furthermore, nanotechnology-based approaches have been devised to overcome the intrinsic limitations of conventional therapies for cancer management, and have been shown to more precise, safer, and highly effective therapeutic tools. Although nanotechnology-based approaches have achieved substantial success for the management of cancer, certain obstacles remain such as inadequate knowledge of nano-bio interactions and the challenges associated with the three stages of clinical trials. This review highlights the different roles of integrins and of integrin-dependent signaling in various cancers and describes the applications of nanotherapeutics targeting integrins. In addition, we discuss RGD-based approaches and challenges posed to cancer management.

In situ dual-crosslinked nanoparticles for tumor targeting gene delivery

The instability of gene delivery systems and their "off-target" features are among the major hurdles in gene therapy. In this study, a facile fabrication platform is constructed to endow the gene delivery system with high stability in the circulation system and achieve targeted delivery of plasmid DNA (pDNA) into cancer cells. Aldehyde groups-bearing hyaluronic acid (HA-CHO) is initially synthesized through oxidation, and is then shielded on polyethylenimine/DNA (PEI/DNA) complex particles to form dual-crosslinked nanoparticles in situ. These nanoparticles simultaneously possess electrostatic and chemical crosslinks between outer layers and cores. The dual-crosslinking system further offers the following advantages when used for gene delivery. First, the two different in situ crosslinking routes strengthen nanoparticle stability. Second, targeting ligands on HA layers mediate specific recognition toward cancer cells. Cell and animal experiments demonstrate that the as-prepared complex particles exhibit enhanced stability in serum and excellent long circulation behavior in vivo. Third, the dual-crosslinked nanoparticles present good accumulation ability in tumors after intravenous injection into nude mice bearing HeLa tumors. Overall, the dual-crosslinking strategy is a promising solution for constructing an efficient gene delivery system.

STATEMENT OF SIGNIFICANCE

This manuscript focused on the in situ dual-crosslinked nanoparticles for tumor targeting pDNA delivery. The novel system is prepared by in situ shielding HA-CHO on PEI/DNA complexes. The electrostatic crosslink formed between carboxyl groups on HA-CHO and amine groups on PEI as well as the reaction between aldehyde groups on HA-CHO and amine groups on PEI contributes to the chemical crosslink. By introduction of HA-CHO on PEI/DNA complexes, they show promoting colloidal stability, enhanced cellular uptake and tumor targeting ability. The in vivo experiments further confirm the excellent ability of long circulation and tumor accumulation. Accordingly, HA-CHO2/PEI/DNA has great potential for tumor targeting antitumor therapy.