Natural fluorescence properties of brome mosaic virus protein

Optical Characteristics and Tumor Imaging Capabilities of Near Infrared Dyes in Free and Nano-Encapsulated Formulations Comprised of Viral Capsids

Near infrared (NIR) fluorescent molecules and nanosized structures can serve as potential optical probes for image-guided removal of small tumor nodules (≲ 1 mm diameter). Although indocyanine green (ICG) remains as the only FDA-approved NIR dye, other organic dyes are under extensive development for enhanced imaging capabilities. One such dye is BrCy106-NHS where bromine is substituted for aromatic structures in cyanine dyes. Herein, we investigate the absorption and fluorescence characteristics of ICG and BrCy106-NHS, and quantitatively assess their tumor imaging capabilities in free (non-encapsulated) and a nano-encapsulated form that utilizes the capsid protein (CP) from genome-depleted plant-infecting brome mosaic virus as the encapsulating shell. We refer to these nanoconstructs as optical viral ghosts (OVGs). For example, when fabricated at CP to dye concentration ratio of 200, value of the spectrally integrated fluorescence emission for BrCy106-NHS-doped OVGs is ∼60 times higher than that of ICG-doped OVGs. Our analysis of homogenized mice intraperitoneal tumors indicate that the averaged total fluorescence emission associated with the use of BrCy106-NHS-doped can be at least about 44 times greater than that of ICG-doped OVGs. Our results suggest that OVGs containing BrCy106-NHS may potentially serve as effective optical probes for tumor imaging.

Virus-resembling nano-structures for near infrared fluorescence imaging of ovarian cancer HER2 receptors

Ovarian cancer remains the dominant cause of death due to malignancies of the female reproductive system. The capability to identify and remove all tumors during intraoperative procedures may ultimately reduce cancer recurrence, and lead to increased patient survival. The objective of this study is to investigate the effectiveness of an optical nano-structured system for targeted near infrared (NIR) imaging of ovarian cancer cells that over-express the human epidermal growth factor receptor 2 (HER2), an important biomarker associated with ovarian cancer. The nano-structured system is comprised of genome-depleted plant-infecting brome mosaic virus doped with NIR chromophore, indocyanine green, and functionalized at the surface by covalent attachment of monoclonal antibodies against the HER2 receptor. We use absorption and fluorescence spectroscopy, and dynamic light scattering to characterize the physical properties of the constructs. Using fluorescence imaging and flow cytometry, we demonstrate the effectiveness of these nano-structures for targeted NIR imaging of HER2 receptors in vitro. These functionalized nano-materials may provide a platform for NIR imaging of ovarian cancer.

Endocytosis at the nanoscale

Endocytosis is a fundamental process in which eukaryotic cells internalise molecules and macromolecules via deformation of the membrane and generation of membrane-bound carriers. Functional aspects are not only limited to uptake of nutrients, but also play a primary role in evolutionary conserved processes such as the regulation of plasma membrane protein activity (i.e. signal-transducing receptors, small-molecule transporters and ion channels), cell motility and mitosis. The macromolecular nature of the material transported by endocytosis makes this route one of the most important targets for nanomedicine. Indeed, many nanoparticle formulations have been customised to enter cells through endocytosis and deliver the cargo within the cell. In this critical review, we present an overview of the biology of endocytosis and discuss its implications in cell internalisation of nanoparticles. We discuss how nanoparticle size, shape and surface chemistry can control this process effectively. Finally, we discuss different drug delivery strategies on how to evade lysosomal degradation to promote effective release of the cargo (376 references).

Intrinsic fluorescence of a non-myelin apoproteolipid and evidence for the existence of conformational flexibility

An extremely hydrophobic protein (Mr = 16000), which in its native form is only soluble in organic solvents and which differs from the myelin proteolipid (Mr = 24000), was purified to homogeneity. Intrinsic fluorescence studies on this apoproteolipid have revealed a large conformational flexibility. In the water-soluble form the emitting residues appear to be buried in a hydrophobic core while in organic solvents they are exposed to the external medium. Structural changes depending on the organic solvent are also observed. The emission characteristics of reconstituted proteoliposomes may be due to the formation of a membrane-linked complex between several proteolipid monomers.

Phosphorescence and optical detection of magnetic resonance of cowpea chlorotic mottle virus

Phosphorescence spectra of the tryptophan residues in cowpea chlorotic mottle virus were recorded at 77 K and the influence of the quaternary structure on the emission characteristics was investigated. The position of the phosphorescence maxima appeared to be invariant under changes in the aggregation state of the virus particle. In contrast to the results of fluorescence experiments, the phosphorescence probably originates from tryptophan residues, buried in the hydrophobic interior of the virus. Optical detection of magnetic resonance on the triplet state of the tryptophan residues at 1.2 K shows a slight shift in the zero-field transitions, when the interaction between the protein and the RNA is abolished. This shift is discussed in relation with changes in polarity and in polarizability of the environment of the phosphorescing tryptophan residues when the interaction between RNA and the protein subunits decreases. The zero-field transitions in the virus are further characterized by a large linewidth, when comparisons are made with similar transitions observed in other proteins. This shows great heterogeneity in the environment of tryptophan residues, and makes the recognition and interpretation of changes in the transitions very complicated.