Paramagnetic particles carried by cell-penetrating peptide tracking of bone marrow mesenchymal stem cells, a research in vitro

Solid phase synthesis in the development of magnetic resonance imaging probes

We review the use of the solid phase synthesis methodology for the preparation of diverse and potent MRI probes.

Cell penetrating peptides: efficient vectors for delivery of nanoparticles, nanocarriers, therapeutic and diagnostic molecules

Efficient delivery of therapeutic and diagnostic molecules to the cells and tissues is a difficult challenge. The cellular membrane is very effective in its role as a selectively permeable barrier. While it is essential for cell survival and function, also presents a major barrier for intracellular delivery of cargo such as therapeutic and diagnostic agents. In recent years, cell-penetrating peptides (CPPs), that are relatively short cationic and/or amphipathic peptides, received great attention as efficient cellular delivery vectors due to their intrinsic ability to enter cells and mediate uptake of a wide range of macromolecular cargo such as plasmid DNA (pDNA), small interfering RNA (siRNAs), drugs, and nanoparticulate pharmaceutical carriers. This review discusses the various uptake mechanisms of these peptides. Furthermore, we discuss recent advances in the use of CPP for the efficient delivery of nanoparticles, nanocarriers, DNA, siRNA, and anticancer drugs to the cells. In addition, we have been highlighting new results for improving endosomal escape of CPP-cargo molecules. Finally, pH-responsive and activable CPPs for tumor-targeting therapy have been described.

Lanthanide-based imaging of protein-protein interactions in live cells

In order to deduce the molecular mechanisms of biological function, it is necessary to monitor changes in the subcellular location, activation, and interaction of proteins within living cells in real time. Förster resonance energy-transfer (FRET)-based biosensors that incorporate genetically encoded, fluorescent proteins permit high spatial resolution imaging of protein-protein interactions or protein conformational dynamics. However, a nonspecific fluorescence background often obscures small FRET signal changes, and intensity-based biosensor measurements require careful interpretation and several control experiments. These problems can be overcome by using lanthanide [Tb(III) or Eu(III)] complexes as donors and green fluorescent protein (GFP) or other conventional fluorophores as acceptors. Essential features of this approach are the long-lifetime (approximately milliseconds) luminescence of Tb(III) complexes and time-gated luminescence microscopy. This allows pulsed excitation, followed by a brief delay, which eliminates nonspecific fluorescence before the detection of Tb(III)-to-GFP emission. The challenges of intracellular delivery, selective protein labeling, and time-gated imaging of lanthanide luminescence are presented, and recent efforts to investigate the cellular uptake of lanthanide probes are reviewed. Data are presented showing that conjugation to arginine-rich, cell-penetrating peptides (CPPs) can be used as a general strategy for the cellular delivery of membrane-impermeable lanthanide complexes. A heterodimer of a luminescent Tb(III) complex, Lumi4, linked to trimethoprim and conjugated to nonaarginine via a reducible disulfide linker rapidly (∼10 min) translocates into the cytoplasm of Maden Darby canine kidney cells from the culture medium. With this reagent, the intracellular interaction between GFP fused to FK506 binding protein 12 (GFP-FKBP12) and the rapamycin binding domain of mTOR fused to Escherichia coli dihydrofolate reductase (FRB-eDHFR) were imaged at high signal-to-noise ratio with fast (1-3 s) image acquisition using a time-gated luminescence microscope. The data reviewed and presented here show that lanthanide biosensors enable fast, sensitive, and technically simple imaging of protein-protein interactions in live cells.

Mesenchymal stem cells: a potential targeted-delivery vehicle for anti-cancer drug, loaded nanoparticles

The targeted delivery of anticancer agents is a promising field in anticancer therapy. Mesenchymal stem cells (MSCs) have inherent tumor-tropic and migratory properties, which allow them to serve as vehicles for targeted drug delivery systems for isolated tumors and metastatic diseases. MSCs have been successfully studied and discussed as a vehicle for cancer gene therapy. However, MSCs have not yet been discussed adequately as a potential vehicle for traditional anticancer drugs. In this review, we will examine the potential of MSCs as a targeted-delivery vehicle for anticancer drug-loaded nanoparticles (NPs), summarize various challenges, and discuss possible solutions for these challenges.

FROM THE CLINICAL EDITOR

In this review, the feasibility of mesenchymal stem cell-based targeted delivery of anticancer agents is discussed.

Targeting the Tumour: Cell Penetrating Peptides for Molecular Imaging and Radiotherapy

Over the last couple of years, the number of original papers and reviews discussing various applications of cell penetrating peptides (CPPs) has grown exponentially. This is not remarkable since CPPs are capable of transporting the most varying cargo across cell membranes which is one of the biggest problems in drug delivery and targeted therapy. In this review, we focus on the use of CPPs and related peptides for delivery of imaging contrast agents and radionuclides to cells and tissues with the ultimate goal of in vivo molecular imaging and molecular radiotherapy of intracellular and even intranuclear targets.