Indocyanine green angiography in the presence of subretinal or intraretinal haemorrhages: clinical and experimental investigations

Indocyanine Green Loaded Modified Mesoporous Silica Nanoparticles as an Effective Photothermal Nanoplatform

Photothermal therapy possesses great advantages for the treatment of drug-resistant tumors. Herein, Near Infrared (NIR)-triggered photothermal nanoparticles were developed through loading indocyanine green (ICG), a kind of NIR dye, into amino group-modified silica nanoparticles (SiO₂-NH₂ NPs). SiO₂-NH₂ NPs were prepared with immobilization of the amino groups into the framework of silica nanoparticles (SiO₂ NPs) by employing (3-aminopropyl)-triethoxysilane (APTES). Before and after the modification of the amino group, the particle sizes of SiO₂ NPs showed similar value, around 100 nm. ICG was further adsorbed into SiO₂-NH₂ NPs by electrostatic attraction to enable SiO₂-NH₂@ICG NPs as a kind of photothermal agent. The loading rate of ICG to SiO₂-NH₂ was greatly increased compared to unmodified SiO₂, and the stability of ICG was also improved. Moreover, the SiO₂-NH₂@ICG NPs exhibited efficient photothermal effects due to ICG transforming laser power into local heat through the connected ICG, when NIR laser irradiation turned on for a couple of minutes. Finally, the in vitro antitumor efficacy of SiO₂-NH₂@ICG NPs was investigated by recording cell proliferation rate and further chronicled the apoptotic morphology evidence by a Calcein-AM/PI fluorescent staining assay, indicating the efficient photothermal targeted therapy for the HepG2 tumor cells.

Near-Infrared Activated Cyanine Dyes As Agents for Photothermal Therapy and Diagnosis of Tumors

Today, it has become apparent that innovative treatment methods, including those involving simultaneous diagnosis and therapy, are particularly in demand in modern cancer medicine. The development of nanomedicine offers new ways of increasing the therapeutic index and minimizing side effects. The development of photoactivatable dyes that are effectively absorbed in the first transparency window of biological tissues (700-900 nm) and are capable of fluorescence and heat generation has led to the emergence of phototheranostics, an approach that combines the bioimaging of deep tumors and metastases and their photothermal treatment. The creation of near-infrared (NIR) light-activated agents for sensitive fluorescence bioimaging and phototherapy is a priority in phototheranostics, because the excitation of drugs and/or diagnostic substances in the near-infrared region exhibits advantages such as deep penetration into tissues and a weak baseline level of autofluorescence. In this review, we focus on NIR-excited dyes and discuss prospects for their application in photothermal therapy and the diagnosis of cancer. Particular attention is focused on the consideration of new multifunctional nanoplatforms for phototheranostics which allow one to achieve a synergistic effect in combinatorial photothermal, photodynamic, and/or chemotherapy, with simultaneous fluorescence, acoustic, and/or magnetic resonance imaging.

Submacular hemorrhage in neovascular age-related macular degeneration: A synthesis of the literature

Large submacular hemorrhage, an uncommon manifestation of neovascular age-related macular degeneration, may also occur with idiopathic polypoidal choroidal vasculopathy. Submacular hemorrhage damages photoreceptors owing to iron toxicity, fibrin meshwork contraction, and reduced nutrient flux, with subsequent macular scarring. Clinical and experimental studies support prompt treatment, as tissue damage can occur within 24 hours. Without treatment the natural history is poor, with a mean final visual acuity (VA) of 20/1600. Reported treatments include retinal pigment epithelial patch, macular translocation, pneumatic displacement, intravitreal or subretinal tissue plasminogen activator, intravitreal anti-vascular endothelial growth factor (VEGF) drugs, and combinations thereof. In the absence of comparative studies, we combined eligible studies to assess the VA change before and after each treatment option. The greatest improvement occurred after combined pars plana vitrectomy, subretinal tissue plasminogen activator, intravitreal gas, and anti-vascular endothelial growth factor treatment, with VA improving from 20/1000 to 20/400. The best final VA occurred using combined intravitreal tissue plasminogen activator, gas, and anti-vascular endothelial growth factor therapy, with VA improving from 20/200 to 20/100. Both treatments had an acceptable safety profile, but most studies were small, and larger randomized controlled trials are needed to determine both safety and efficacy.

Gadolinium-doped silica nanoparticles encapsulating indocyanine green for near infrared and magnetic resonance imaging

Clinical applications of the indocyanine green (ICG) dye, the only near infrared (NIR) imaging dye approved by the Food and Drug Administration (FDA) in the USA, are limited due to rapid protein binding, fast clearance, and instability in physiologically relevant conditions. Encapsulating ICG in silica particles can enhance its photostability, minimize photobleaching, increase the signal-to-noise (S/N) ratio and enable in vivo studies. Furthermore, a combined magnetic resonance (MR) and NIR imaging particulate can integrate the advantage of high-resolution 3D anatomical imaging with high-sensitivity deep-tissue in-vivo fluorescent imaging. In this report, a novel synthesis technique that can achieve these goals is presented. A reverse-microemulsion-based synthesis protocol is employed to produce 25 nm ICG-doped silica nanoparticles (NPs). The encapsulation of ICG is achieved by manipulating coulombic attractions with bivalent ions and aminated silanes and carrying out silica synthesis in salt-catalyzed, mildly basic pH conditions using dioctyl sulfosuccinate (AOT)/heptane/water microemulsion system. Furthermore, paramagnetic properties are imparted by chelating paramagnetic Gd to the ICG-doped silica NPs. Aqueous ICG-dye-doped silica NPs show increased photostability (over a week) and minimal photobleaching as compared to the dye alone. The MR and optical imaging capabilities of these particles are demonstrated through phantom, in vitro and in vivo experiments. The described particles have the potential to act as theranostic agents by combining photodynamic therapy through the absorption of NIR irradiated light.

Near infrared dye indocyanine green doped silica nanoparticles for biological imaging

Indocyanine green (ICG) is an FDA-approved near infrared (NIR) fluorescent dye used in clinical imaging. However, its applications remain limited due to its short half-life, nonspecific plasma binding, optical instability, and poor aqueous stability. Dye doped silica nanoparticles provide an effective barrier in keeping the dye away from the surrounding environment, but ICG cannot be encapsulated into silica easily by conventional methods. In this study, ICG molecules ion-paired with a cationic polymer polyethylenimine (PEI) were successfully encapsulated into a silica matrix to form ICG doped silica nanoparticles by using the Stöber method. Pairing with PEI reduced self-quenching of fluorescence by preventing the aggregation of ICG molecules in silica nanoparticles. Dye leakage was also reduced to the level of 3-6% loss in 5 days. NIR fluorescence images of ICG doped silica NPs below a 2.0 cm thick porcine muscle sample illuminated by NIR light were obtained.

Giant and uniform fluorescence enhancement over large areas using plasmonic nanodots in 3D resonant cavity nanoantenna by nanoimprinting

Using a new nanoplasmonic architecture and an optimized spacer, we observed the following: (a) the average fluorescence of an infrared dye (indocyanine green) is enhanced by 2970 fold uniformly (variation < 11%) over a large sample area and over a wide range of dye concentrations (380 to 380,000 molecule µm(-2)), laser excitation powers and laser beam sizes; and (b) for a single molecule placed at a 'hot spot', the fluorescence enhancement is 4.5 × 10(6) fold. The giant and uniform enhancements (orders of magnitude higher than before), plus easy and inexpensive large area fabrication ( > 4″ wafers), should open up wide applications.

Near-infrared emitting fluorophore-doped calcium phosphate nanoparticles for in vivo imaging of human breast cancer

Early detection is a crucial element for the timely diagnosis and successful treatment of all human cancers but is limited by the sensitivity of current imaging methodologies. We have synthesized and studied bioresorbable calcium phosphate nanoparticles (CPNPs) in which molecules of the near-infrared (NIR) emitting fluorophore, indocyanine green (ICG), are embedded. The ICG-CPNPs demonstrate exceptional colloidal and optical characteristics. Suspensions consisting of 16 nm average diameter particles are colloidally stable in physiological solutions (phosphate buffered 0.15 M saline (PBS), pH 7.4) with carboxylate or polyethylene glycol (PEG) surface functionality. ICG-doped CPNPs exhibit significantly greater intensity at the maximum emission wavelength relative to the free constituent fluorophore, consistent with the multiple molecules encapsulated per particle. The quantum efficiency per molecule of the ICG-CPNPs is 200% greater at 0.049 +/- 0.003 over the free fluorophore in PBS. Photostability based on fluorescence half-life of encapsulated ICG in PBS is 500% longer under typical clinical imaging conditions relative to the free dye. PEGylated ICG-CPNPs accumulate in solid, 5 mm diameter xenograft breast adenocarcinoma tumors via enhanced retention and permeability (EPR) within 24 h after systemic tail vein injection in a nude mouse model. Ex situ tissue imaging further verifies the facility of the ICG-CPNPs for deep-tissue imaging with NIR signals detectable from depths up to 3 cm in porcine muscle tissue. Our ex vivo and in vivo experiments verify the promise of the NIR CPNPs for diagnostic imaging in the early detection of solid tumors.

Rapid deposition of triangular silver nanoplates on planar surfaces: application to metal-enhanced fluorescence

A simple and rapid wet-chemical technique for the deposition of silver triangles on conventional glass substrates, which alleviates the need for lithography, has been developed. The technique is based on the seed-mediated cetyltrimethylammonium-bromide-directed growth of silver triangles on glass surfaces, where smaller spherical silver seeds that were attached to the surface were subsequently converted and grown into silver triangles in the presence of a cationic surfactant and silver ions. The size of the silver triangles was controlled by sequential immersion of silver seed-coated glass substrates into a growth solution and by the duration time of immersion. Atomic force microscopy studies revealed that the size of the silver triangles ranged between 100 and 500 nm. Interestingly, these new surfaces are a significant improvement over traditional silver island films for applications in metal-enhanced fluorescence. A routine 16-fold enhancement in emission intensity was typically observed, for protein-immobilized indocyanine green, with a relatively very low loading density of silver triangles on the glass surface.

Fast and slow deposition of silver nanorods on planar surfaces: application to metal-enhanced fluorescence

Two methods have been considered for the deposition of silver nanorods onto conventional glass substrates. In the first method, silver nanorods were deposited onto 3-(aminopropyl)triethoxysilane-coated glass substrates simply by immersing the substrates into the silver nanorod solution. In the second method, spherical silver seeds that were chemically attached to the surface were subsequently converted and grown into silver nanorods in the presence of a cationic surfactant and silver ions. The size of the silver nanorods was controlled by sequential immersion of silver seed-coated glass substrates into a growth solution and by the duration of immersion, ranging from tens of nanometers to a few micrometers. Atomic force microscopy and optical density measurements were used to characterize the silver nanorods deposited onto the surface of the glass substrates. The application of these new surfaces is for metal-enhanced fluorescence (MEF), whereby the close proximity of silver nanostructures can alter the radiative decay rate of fluorophores, producing enhanced signal intensities and an increased fluorophore photostability. In this paper, it is indeed shown that irregularly shaped silver nanorod-coated surfaces are much better MEF surfaces as compared to traditional silver island or colloid films. Subsequently, these new silver nanorod preparation procedures are likely to find a common place in MEF, as they are a quicker and much cheaper alternative as compared to surfaces fabricated by traditional nanolithographic techniques.

Metal-Enhanced Fluorescence (MEF) Due to Silver Colloids on a Planar Surface: Potential Applications of Indocyanine Green to in Vivo Imaging

We examined the effects of metallic silver colloids on the fluorescence spectral properties of indocyanine green (ICG), which is a dye widely used for in vivo medical testing. Silver colloids from a suspension bind spontaneously to amine-coated surfaces. These colloid-coated surfaces were found to cause a 30-fold increase in the intensity of ICG, which was held close to the metal surface by adsorbed albumin. The increased intensities of ICG were also associated with decreased lifetimes and increased photostability, which are indicative of modifying the fluorophores radiative decay rate. These results suggest the use of metal colloid-enhanced ICG for applications to retinal angiography and vascular imaging and as a contrast agent for optical tomography.