Photoinduced in†Vivo Magnetic Resonance Imaging (MRI) with Rapid CO Release from an MnCO-Protein Needle Composite.

Construction of an artificial protein needle (PN), which includes the membrane puncturing needle domain of bacteriophage T4 conjugated to Mn carbonyl (MnCO) complexes, is reported. The responsiveness to visible light of the MnCO complex makes it useful as a photoinduced in vivo magnetic resonance imaging contrast reagent (MRI CR), because the PN carrier has the potential to deliver the MnCO complex into mouse tumors with retention of coordination structure within the in vivo environment. Moreover, the composite has higher relaxivity and longer circulation as an MRI CR than the corresponding MnCO complex. These results demonstrate construction of a responsive in vivo MRI CR by using an artificial metalloprotein.

Intracellular CO release from composite of ferritin and ruthenium carbonyl complexes.

Protein cages have been utilized as templates in the development of biomaterials. Here we report protein engineering of the ferritin (Fr) cage for encapsulating carbon monoxide releasing molecules (CORMs) and release of CO gas which serves as a cell signaling molecule. The protein cages enable us to increase the half-life for CO release, providing a release rate that is 18-fold slower than the rate of a typical CORM, Ru(CO)3Cl(glycinate) (CORM-3). Moreover, the uptake ratio of the composite is about 4-fold greater than that of CORM-3. We found that these effects enhance the activation of nuclear factor κB 10-fold higher than CORM-3. The protein cage of Fr thus provides the basis for new CORMs that can be used for in vitro cell research.

A metal carbonyl-protein needle composite designed for intracellular CO delivery to modulate NF-κB activity.

Carbon monoxide (CO) has been recognized as a messenger for signal transduction in living cells and tissues. For intracellular CO delivery, several metal carbonyl complexes have been used as CO-releasing molecules (CO-RMs). To improve the properties of CO-RMs, such as the stability and the CO release rate, ligands and carriers of the metal complexes have been exploited. Here we report the development of an efficient intracellular CO delivery system using a protein scaffold. We used a protein needle reconstructed from gene product 5 of bacteriophage T4, which has high cellular permeability and stability. When ruthenium carbonyl complexes are conjugated to the needle using a His-tag triad at the C-terminus, the resulting composite has a significantly higher cellular uptake efficiency of Ru carbonyl and a 12-fold prolonged CO release rate relative to Ru(CO)3Cl(glycinate), a widely used CO-RM. We demonstrate that CO delivered by the composite activates the transcriptional factor nuclear factor-kappaB (NF-κB), which in turn leads to significant induction of expression of its target genes, HO1, NQO1, and IL6, through generation of reactive oxygen species (ROS). The signaling pathway is distinct from that of tumor necrosis factor (TNF)-α-induced activation of NF-κB. The protein needle-based CO-RM can be exploited to elucidate the biological functions of CO and used in the development of protein-based organometallic tools for modulation of cellular signaling.