Molecular imaging with nanoparticles: giant roles for dwarf actors

Abstract

Molecular imaging, first developed to localise antigens in light microscopy, now encompasses all imaging modalities including those used in clinical care: optical imaging, nuclear medical imaging, ultrasound imaging, CT, MRI, and photoacoustic imaging. Molecular imaging always requires accumulation of contrast agent in the target site, often achieved most efficiently by steering nanoparticles containing contrast agent into the target. This entails accessing target molecules hidden behind tissue barriers, necessitating the use of targeting groups. For imaging modalities with low sensitivity, nanoparticles bearing multiple contrast groups provide signal amplification. The same nanoparticles can in principle deliver both contrast medium and drug, allowing monitoring of biodistribution and therapeutic activity simultaneously (theranostics). Nanoparticles with multiple bioadhesive sites for target recognition and binding will be larger than 20 nm diameter. They share functionalities with many subcellular organelles (ribosomes, proteasomes, ion channels, and transport vesicles) and are of similar sizes. The materials used to synthesise nanoparticles include natural proteins and polymers, artificial polymers, dendrimers, fullerenes and other carbon-based structures, lipid-water micelles, viral capsids, metals, metal oxides, and ceramics. Signal generators incorporated into nanoparticles include iron oxide, gadolinium, fluorine, iodine, bismuth, radionuclides, quantum dots, and metal nanoclusters. Diagnostic imaging applications, now appearing, include sentinal node localisation and stem cell tracking.

Graphene-Based Nanomaterials in Bioimaging

“…It has advantages over other imaging modalities including relatively low cost, high sensitivity (~10 −9 -10 −12 mol/L), nonionizing radiation, real-time imaging; short acquisition time, and multiplexing capability (61). However, this modality suffers from poor tissue penetration (0-2 cm), strong tissue scattering of photons in the visible light region (395-600 nm) (62), and significant background because of tissue autofluorescence and light absorption by proteins (257-280 nm), heme groups (absorbance maximum at 560 nm), and even water (above 900 nm) (63). To address these issues, nearinfrared window (NIR, 650-900 nm) (64) and second NIR window (NIR-II, 1000-1700 nm) (65,66) imaging modalities have been explored with the advantages of reduced autofluorescence, reduced tissue scattering, and greater depth of penetration for in vivo imaging.…”

Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing

“…Common techniques include near infrared fluorescence (NIRF), positron emission tomography (PET), optical acoustic tomography (OAT), photo acoustic tomography (PAT), and magnetic resonance imaging (MRI) [338,[340][341][342][343]. Typically QDs, fluorescent dyes and iodinated agents are used as contrast agents and some methods call for the use of radioactive isotopes [343][344][345][346][347][348][349].…”

Prostate Cancer Imaging and Therapy: Potential Role of Nanoparticles

“…Curcumin has demonstrated the potential to suppress in vitro prostate cancer cell proliferation in both androgensensitive prostate cancer cell line LNCaP and androgen-independent cell line DU145 (67)(68)(69)(70), as well as in vivo tumor growth in a LNCaP xenograft mouse model (71). Dendrimer scaffolds have been commonly used in PET and SPECT studies (72,73). Incorporation of a nuclear imaging reporter into the nanoconstructs is often used to follow the in vivo distribution and to quantify the targeted delivery of the nanoconstruct system and may aid in determining dosimetry of therapeutics at tumor sites.…”