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Multimodal imaging removes the intrinsic limitations of individual modalities, while the multipurpose nanoagents reduce the toxicity associated with the use of multiple contrast agents. However, limited functionality, inefficient or incompatible targeting, and unknown biodistribution are significant drawbacks for such complicated nanodesigns. We report a biofriendly pentamodal imaging agent with the synergistic dual-targeting ability (passive and active) based on fluoromagnetic NaGdF4:Yb,Er upconverting nanoparticles (UCNPs). Besides the nano-enabled passive targeting, the apo-human serum transferrin protein (Tf) conjugation actively targets the transferrin receptors (TfR) over-expressed on different cancer cells. The radiolabel, 99mTc, chelates in the Tf core increase the radiolabeling efficiency (∼95%) and stability (∼100% for 24 h), enabling efficient single-photon emission computed tomography imaging. Deep-penetrating 980 nm excited UCNPs are inherently active luminescent and photothermal agents enabling fluorescence and photothermal imaging, respectively. The Gd in UCNPs produces a T1-weighted MRI signal, and the Yb helps in computed tomography (CT) as contrast agents. A pentamodal imaging agent (UCNP@Tf-99mTc) with synergistic dual-targeting ability is thus designed. In vitro studies demonstrated receptor-mediated endocytosis and minimal cytotoxicity of the UCNP@Tf-99mTc nanoformulation (>75% cell viability at 1000 ppm). The in vivo biodistribution studies in the mice model under SPECT/CT revealed its near-ideal bioavailability and renal clearance behavior. The MRI investigation on 4 T1 tumor-bearing mice brought direct evidence of passive and synergistic passive-active targeted tumor accumulation of the nanoformulation. The in vivo multimodal tumor imaging (MRI/SPECT/thermal-camera/CT) demonstrates the potency of UCNP@Tf-99mTc as a single replacement for multiple imaging agents and a perfect candidate for the ultramodern Advanced Multimodality Image Guided Operating (AMIGO) suite. [ABSTRACT FROM AUTHOR]

A biosensor can sense biological elements after interaction with the recognition element. The signal produced due to interaction of the analyte with its biochemical element is transduced by a transducer and detected by appropriate modes. The miniaturization of these biosensors at the nano level using nanostructures as a platform for sensing the analyte or its detection is called a nanobiosensor. Several biological elements can be detected like nucleic acids, enzymes, antibodies, microorganisms, toxins, cells etc. with high specificity. This mini review focuses on the different types of nanobiosensors based on the type of analyte and the type of transducer used for detection. The different types of fluorescence based design of biosensors are also discussed along with the metal enhanced fluorescence based nanobiosensors. The application of biosensors towards the diagnosis of various diseases, targeted drug delivery and imaging is also discussed. [ABSTRACT FROM AUTHOR]