Click-Functionalized Compact Quantum Dots Protected by Multidentate-Imidazole Ligands: Conjugation-Ready Nanotags for Living-Virus Labeling and Imaging

PSMA-targeted SPECT agents: mode of binding effect on in vitro performance

BACKGROUND

The enzyme-biomarker prostate-specific membrane antigen (PSMA) is an active target for imaging and therapeutic applications for prostate cancer. The internalization of PSMA has been shown to vary with inhibitors' mode of binding: irreversible, slowly reversible, and reversible.

METHODS

In the present study, PSMA-targeted clickable derivatives of an irreversible phosphoramidate inhibitor DBCO-PEG(4) -CTT-54 (IC(50) = 1.0 nM) and a slowly reversible phosphate inhibitor, DBCO-PEG(4) -CTT-54.2 (IC(50) = 6.6 nM) were clicked to (99m) Tc(CO)(3) -DPA-azide to assemble a PSMA-targeted SPECT agent. The selectivity, percent uptake, and internalization of these PSMA-targeted SPECT agents were evaluated in PSMA-positive and PSMA-negative cells.

RESULTS

In vitro studies demonstrated that PSMA-targeted SPECT agents exhibited selective cellular uptake in the PSMA-positive LNCaP cells compared to PSMA-negative PC3 cells. More importantly, it was found that (99m) Tc(CO)(3) -DPA-DBCO-PEG(4) -CTT-54 based on an irreversible PSMA inhibitor core, exhibited greater uptake and internalization than (99m) Tc(CO)(3) -DPA-DBCO-PEG(4) -CTT-54.2 constructed from a slowly reversible PSMA inhibitor core.

CONCLUSIONS

We have demonstrated that a PSMA-targeted SPECT agent can be assembled efficiently using copper-less click chemistry. In addition, we demonstrated that mode of binding has an effect on internalization and percent uptake of PSMA-targeted SPECT agents; with the irreversible targeting agent demonstrating superior uptake and internalization in PSMA+ cells. The approach demonstrated in this work now supports a modular approach for the assembly of PSMA-targeted imaging and therapeutic agents.

Quantum dot and gold nanoparticle immobilization for biosensing applications using multidentate imidazole surface ligands

A facile approach for modification of solid substrates with multidentate imidazole ligands was developed for immobilization of high densities of quantum dots (QDs) that were capped with hydrophilic thiol-based ligands, and for immobilization of noble metal nanoparticles. Imidazole polymer was synthesized using poly(acrylic acid) as a backbone, and grafted on amine functionalized substrate in a two-step approach. The polymer-modified surface was characterized using ellipsometry, water contact angle, and X-ray photoelectron spectroscopy. Fluorescence spectroscopy and scanning electron microscopy were used to evaluate nanoparticle immobilization. Homogeneous, high density (ca. 5 × 10(11) cm(-2)) QD films formed via self-assembly were obtained within 4-6 h. Similarly, the imidazole polymer was also shown to be effective for immobilization of gold nanoparticles as a uniform film. By making use of the pH-sensitive affinity of the imidazole rings to zinc on the surface of QDs, it was possible to achieve regeneration of functional ligands suitable for subsequent immobilization of new QDs. Immobilized QDs were used as a platform for bioconjugation with oligonucleotides and peptides. The transduction of nucleic acid hybridization and enzyme activity using QDs as energy donors in interfacial fluorescence resonance energy transfer (FRET) indicated that the immobilization strategy preserved the functional properties of the QDs. The multidentate imidazole ligands used for QD immobilization offer the highest denticity of binding in comparison to the currently available approaches without compromise in their optical properties and ability to interact with biomolecules in solution.

A mild and reliable method to label enveloped virus with quantum dots by copper-free click chemistry

Real-time tracking of the dynamic process of virus invasion is crucial to understanding the infection mechanism. For successful tracking, efficient labeling methods are indispensable. In this paper, we report a mild and reliable method for labeling viruses, especially with regard to easily disabled enveloped viruses. The copper-free click chemistry has been used to label enveloped viruses with quantum dots (QDs) by linking virions modified with azide to the QDs derived with dibenzocyclooctynes (DBCO). Both vaccinia virus (VACV) and avian influenza A virus (H9N2) can be specifically and rapidly labeled under mild conditions, with a labeling efficiency of more than 80%. The labeled virions were of intact infectivity, and their fluorescence was strong enough to realize single-virion tracking. Compared to previously reported methods, our method is less destructive, reliable, and universal, without specific requirements for the type and structure of viruses to be labeled, which has laid the foundation for long-term dynamic visualization of virus infection process.