New generation fluorophores, also termed upconversion nanoparticles (UCNPs), have the ability to convert near infrared radiations with lower energy into visible radiations with higher energy via a non-linear optical process. Recently, these UCNPs have evolved as alternative fluorescent labels to traditional fluorophores, showing great potential for imaging and biodetection assays in both in vitro and in vivo applications. UCNPs exhibit unique luminescent properties, including high penetration depth into tissues, low background signals, large Stokes shifts, sharp emission bands, and high resistance to photo-bleaching, making UCNPs an attractive alternative source for overcoming current limitations in traditional fluorescent probes. In this review, we discuss the recent progress in the synthesis and surface modification of rare earth doped UCNPs with a specific focus on their biological applications.

The development of nanoarchitectured functional materials continues to receive tremendous attention in bionanotechnology, because such materials offer great potential for applications in catalysis, batteries, microelectronics, nonlinear optics, and nanosensors.[1-5] The layer-by-layer (LBL) assembly technique was introduced to construct a multilayered nanocomposite film by alternately dipping a substrate in positively and then negatively charged polyelectrolyte solutions.[6] This approach is simple and can be applied using a wide range of materials. Moreover, the surface charges and thicknesses of the films produced can be easily tuned. One can easily engineer the properties of the multilayered films by controlling the spatial arrangement of materials with different functionalities in the films.

A photosensitizer, pyropheophorbid‐a (PPa), is conjugated to SKBR‐3 breast cancer cell‐specific biological nanowire phage, to form a novel PPa‐phage complex, which is further successfully used in selectively killing SKBR‐3 breast cancer cells by the mechanism of photodynamic therapy (PDT).

Filamentous phage as a bacteria-specific virus can be conjugated with an anti-cancer drug and has been proposed to serve as a carrier to deliver drugs to cancer cells for targeted therapy. However, how cell-targeting filamentous phage alone affects cancer cell biology is unclear. Phage libraries provide an inexhaustible reservoir of new ligands against tumor cells and tissues that have potential therapeutic and diagnostic applications in cancer treatment. Some of these identified ligands might stimulate various cell responses. Here we identified new cell internalizing peptides (and the phages with such peptides fused to each of ~3900 copies of their major coat protein) using landscape phage libraries and for the first time investigated the actin dynamics when selected phages are internalized into the SKBR-3 breast cancer cells. Our results show that phages harboring VSSTQDFP and DGSIPWST peptides could selectively internalize into the SKBR-3 breast cancer cells with high affinity, and also show rapid involvement of membrane ruffling and re-arrangements of actin cytoskeleton during the phage entry. The actin dynamics was studied by using live cell and fluorescence imaging. The cell-targeting phages were found to enter breast cancer cells through energy dependent mechanism and phage entry interferes with actin dynamics, resulting in reorganization of actin filaments and increased membrane rufflings in SKBR-3 cells. These results suggest that, when phage enters epithelial cells, it triggers transient changes in the host cell actin cytoskeleton. This study also shows that using multivalent phage libraries considerably increases the repertoire of available cell-internalizing ligands with potential applications in targeted drug delivery, imaging, molecular monitoring and profiling of breast cancer cells.