This PDF file contains the front matter associated with SPIE Proceedings Volume 7190, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing

Starting from expertise in the area of chemical synthesis, particularly in tetrapyrrolic macrocycles and an interest in modelling structures for particular objectives, we came to the point of aiming at modelling photochemical sensitizers designed for photodynamic therapy (PDT) purposes. Our endeavours were gratifying when it was proved that our synthetic methodologies allowed for the easy availability of properly halogenated porphyrins with high quantum yield singlet oxygen efficiency. Joining the presence of this heavy atom and other functionalities as substituents in selected positions of macrocyclic structures we were able to generate novel porphyrin structures whose photophysical and photochemical properties, singlet oxygen formation quantum yields, photobleaching and logP were measured. Cellular uptake measurements and cytotoxicity assays on WiDr adenocarcinoma and A375 tumor cell lines were carried out and some of our porphyrins demonstrated very high performance as PDT sensitizers comparatively to known compounds approved for clinical use and in the market. Further developments of our studies allowed for the generation of different and more efficient structures, easily made available by our own synthetic methodologies. Our studies in this area allowed us to reach a stage which we believe to correspond to a significant knowledge and capacity to synthesise a broad range of simple structures, whose selectivity and efficiency as PDT sensitizers can be modulated for different cellular and tissue specificities. Our most recent developments in this area will be presented in this communication.

We have recently introduced liposome-supported plasmon resonant gold nanoshells (Troutman et al., Adv. Mater. 2008, 20, 2604-2608). These plasmon resonant gold-coated liposomes are degradable into components of a size compatible with renal clearance, potentially enabling their use as multifunctional agents in applications in nanomedicine, including imaging, diagnostics, therapy, and drug delivery. The present research demonstrates that laser illumination at the wavelength matching the plasmon resonance band of a gold-coated liposome leads to the rapid release of encapsulated substances, which can include therapeutic and diagnostic agents. Leakage of encapsulated contents is monitored through the release of self-quenched fluorescein, which provides an increase in fluorescence emission upon release. Moreover, the resonant peak of these gold-coated liposomes is spectrally tunable in the near infrared range by varying the concentration of gold deposited on the surface of liposomes. Varying the plasmon resonant wavelengths of gold-coated liposomes can provide a method for spectrally-coding their light-mediated content release, so that the release event is initiated by the specific wavelength of light used to illuminate the liposomes. The development of spectrally-coded release can find applications in controlled delivery of multiple agents to support complex diagnostic tests and therapeutic interventions.

Nanoparticles have a promising application prospect in biomedical field. The study of their dynamic characteristics including in vivo distribution and clearance has the most important significance on their biological application. In this paper, bio-distribution and clearance of solid and colloid nanoparticles with different size in mouse model was intensively studied in vivo by using near infrared optical imaging technique. Here, nanohydrogels were synthesized by precipitation polymerization method and the size of the nanohydrogel could be arbitrarily manipulated according to different surfactant concentration. Near infrared fluorescence dye were entrapped into their inner core for in vivo studies. Meanwhile, the size of CdHgTe/SiO2 solid nanoparticles could be controlled by the thickness of SiO2 coated on the surface of CdHgTe. The results from the near infrared imaging showed that nanohydrogels with different size have the similar tissue distribution but CdHgTe/SiO2 nanoparticles in different size have a size-dependent organ specification. These results provided an important reference for the design of targeted drug delivery systems and their biomedical applications.

We have developed a multifunctional nanoagent, termed the combined imaging and therapy nanocage system (CIT-NS). This nanosystem platform consists of a poly(lactic-co-glycolic) acid polymer core and outer silver cage network. The inner core of CIT-NS is capable of carrying drugs, such as the chemotherapeutic agent doxorubicin, or imaging contrast agents, such as dyes or fluorescent compounds. The outer silver cage is specifically designed to enhance contrast in photoacoustic imaging, i.e., acoustic imaging of optical absorption. In this paper, methods to create the CIT-NS are described. Initial characterization indicates that the developed CIT-NS will significantly increase contrast in photoacoustic imaging while retaining the potential to deliver large payloads of drug simultaneously. Therefore, the CITNS may enable multi-modal imaging approaches or simultaneous imaging and therapy strategies to improve treatment and detection of cancer and other pathologies.

Near-Infrared (NIR) fluorescence has been used both as an analytical tool as molecular probes and in in vitro or in vivo imaging of individual cells and organs. The NIR region (700-1100 nm) is ideal with regard to these applications due to the inherently lower background interference and the high molar absorptivities of NIR chromophores. NIR dyes are also useful in studying binding characteristics of large biomolecules, such as proteins. Throughout these studies, different NIR dyes have been evaluated to determine factors that control binding to biomolecules, including serum albumins. Hydrophobic character of NIR dyes were increased by introducing alkyl and aryl groups, and hydrophilic moieties e.g., polyethylene glycols (PEG) were used to increase aqueous solubility. Recently, our research group introduced bis-cyanines as innovative NIR probes. Depending on their microenvironment, bis-cyanines can exist as an intramolecular dimer with the two cyanines either in a stacked form, or in a linear conformation in which the two subunits do not interact with each other. In this intramolecular H-aggregate, the chromophore has a low extinction coefficient and low fluorescence quantum yield. Upon addition of biomolecules, the H-and D- bands are decreased and the monomeric band is increased, with concomitant increase in fluorescence intensity. Introduction of specific moieties into the NIR dye molecules allows for the development of physiological molecular probes to detect pH, metal ions and other parameters. Examples of these applications include imaging and biomolecule characterizations. Water soluble dyes are expected to be excellent candidates for both in vitro and in vivo imaging of cells and organs.

Fluorescence imaging (FLI) allows the in vivo monitoring of biological events associated with disease and represents a new promising tool for drug discovery. In particular, it speeds up the development and assessment of new therapies in oncology, helps in diagnosis, and improves surgery by fluorescence-guided tumor resection. This technique is highly sensitive, non-ionizing, easy to use and relatively inexpensive. Nevertheless, the main limitation of FLI lies in the optical properties of biological tissues. Mainly because of haemoglobin and water absorption, only near-infrared (NIR) light is adapted to image tissues in depth. Using a contrasting agent absorbing and emitting in the NIR region is therefore necessary to improve the background signal ratio, and thus the image contrast. Among many commercially available NIR optical contrast agents, only indocyanine green (ICG), has been approved by the United State Food and Drug Administration (FDA) for various medical applications. However, its instability (photo-degradation, thermal-degradation and low aqueous solubility) limits its applications as a fluorescent probe for imaging purposes. In order to improve the effectiveness of ICG, we engineered ICG-doped lipid nanoparticles (LNP). In this communication, we will report the design of these novel fluorescent nanoparticle probes. These low cost nanocarriers have numerous advantages, including their high chemical stability and biocompatibility. The characterization of the optical properties of the nanoparticles entrapping ICG will also be discussed. Finally, the biodistribution in mice of ICG when delivered through nanoparticles in comparison to free ICG in solution is presented. It demonstrates the efficient accumulation of ICG-doped nanoparticles in the tumor site.

Strong vascular endothelial growth factor (VEGF) receptor expression has been found at the sites of angiogenesis, particularly in tumor growth areas. An increase in VEGF receptor-2 is associated with colon cancer progression. The in vivo detection of VEGF receptor is of interest for the purposes of studying carcinogenesis, the efficacy of chemopreventive and therapeutic agents, clinical diagnosis, and therapeutic monitoring. In this study, a novel single chain (sc) VEGF-based molecular probe is utilized in the AOM-treated mouse model of colorectal cancer to study delivery route and specificity for disease. The probe was constructed by site-specific conjugation of a near-infrared dye, Cy5.5, to scVEGF and detected in vivo with a dual-modality optical coherence tomography / laser-induced fluorescence (OCT/LIF) endoscopic system. The LIF excitation source was a 633 nm He:Ne laser and red/near-infrared fluorescence was detected with a spectrometer. OCT was used to obtain two-dimensional longitudinal tomograms at eight rotations in the distal colon. Fluorescence emission levels were correlated with OCT-detected disease in vivo and H&E stained histology slides ex vivo. Specificity for disease was found to be highly dependent on the delivery route. Intravenous injection resulted in poor specificity due to many extra-colon confounders, while colon lavage eliminated most of these. High fluorescence emission intensity was correlated with tumor presence as detected using OCT. Results suggest potential for clinical use to facilitate earlier diagnosis of cancer.

The study of disease processes requires a number of tools for detection of proteins and biomarkers in cell and animal based assays. Near infrared (NIR) technologies offer the advantage of high signal without interference from background producing factors such as tissues, blood, or plastics. NIR fluorescence quenching biochemical assays employing a novel NIR quencher are homogeneous and sensitive. NIR-based immunocytochemical assays offer a means of quantitatively evaluating cell signaling pathways. The technology can be extended to the development of targeted molecular imaging agents for disease analysis in animal models. We describe here model assays for each of these categories. A fluorescence quenching caspase-3 assay was developed employing a novel, broadly applicable quencher dye suitable for use with both visible and NIR dye chemistries. An NIR cell based assay is described for assessment of phosphorylation of p53 in response to a cellular stimulus. Finally, we describe the development and application of a targeted NIR optical imaging agent for monitoring tumor growth in whole animals. The NIR biochemical and cell based assays are robust with Z' factors greater than 0.7. The use of an IRDye ^(R)800CW-labeled cyclic RGD peptide is presented as a model for development and application of targeted imaging agents. NIR technologies are compatible with the complete spectrum of assay needs for disease analysis and therapeutic development.

Rapid assessment of glomerular filtration rate (GFR), which measures the amount of plasma filtered through the kidney within a given time, would greatly facilitate monitoring of renal function for patients at the bedside in the clinic. In our pursuit to develop exogenous fluorescent tracers for real-time monitoring of renal function by optical methods, N-alkylated aminopyrazine dyes and their hydrophilic conjugates based on poly (ethylene glycol) (PEG) were synthesized via reductive amination as the key step. Photophysical properties indicated a bathochromic shift on the order of 50 nm in both absorption and emission compared to naked aminopyrazines which could be very useful in enhancing both tissue penetration as well as easier detection methods. Structure-activity relationship (SAR) and pharmacokinetic (PK) studies, and the correlation of in vivo optical data with plasma PK for measurement of clearance (and hence GFR) are focus of the current investigation.

A new class of phosphorescent nanoparticles has been developed that use halogen-containing polymers and copolymers to encapsulate phosphorescent molecules. Their strong phosphorescence of long lifetime and large Stoke shift are not subject to oxygen quenching under ambient conditions due to the low oxygen permeability of the encapsulation matrix. The cross-linked phosphorescent particles are very stable and easily re-suspendable in aqueous media with surface functional groups to allow covalent tagging of biological recognition molecules such as antibodies. The conjugates can be used to provide very sensitive detection of analytes through time-resolved phosphorescence measurements. In addition to their applications for solution-based biological assays, those particles have also been demonstrated to be very useful for dry-chemistry-based time-resolved luminescent lateral flow assays.

A dramatic change occurs in the cellular microenvironment during cell stress, but it has been difficult to follow these changes in vivo. Here, fluorescence lifetime imaging (FLIM) microscopy has been used to examine stress-induced changes in the microenvironment in a single cell. It is observed that the fluorescence lifetime of HeLa cells expressing an enhanced green fluorescent protein (EGFP)-tudor fusion protein changes under stress. The change in the fluorescence lifetime appears to be due to an alteration in the local electric field in the protein matrix surrounding the chromophore of EGFP. In fact, the fluorescence lifetime of the GFP chromophore in a polyvinyl alcohol film is found to decrease in the presence of an electric field, based on the measurements of the field-induced change in the fluorescence decay profile. The results indicate that the rate of the non-radiative process of the chromophore of GFP is enhanced by an applied electric field. The FLIM method allows noninvasive determination of the status of the individual cells.

In vivo optical molecular imaging of fluorescent probes predominantly employs continuous wave techniques to measure fluorescence intensity. Alternatively, time domain techniques permit measurement of fluorescence lifetime in addition to fluorescence intensity. Fluorescence lifetime allows discrimination of fluorescent probes with contrasting lifetime or inference of a probe's environment due to lifetime sensitivity. Here, we present the use of fluorescence lifetime contrast to evaluate the relative concentrations of a mixture of fluorophores in a scattering medium. This approach offers the potential to perform dual-probe in vivo optical molecular imaging at a single wavelength employing lifetime contrast rather than via spectral intensity contrast.

Fluorescence imaging is a mainstay of biomedical research, allowing detection of molecular events in both fixed and living cells, tissues and whole animals. Such high resolution fluorescence imaging is hampered by unwanted signal from intrinsic background fluorescence and scattered light. The signal to background ratio can be improved by using extrinsic contrast agents and greatly enhanced by multispectral imaging methods. Unfortunately, these methods are insufficient for deep tissue imaging where high contrast and speedy acquisition are necessary. Fluorescence lifetime (FLT) is an inherent characteristic of each fluorescent species that can be independent of intensity and spectral properties. Accordingly, FLT-based detection provides an additional contrast mechanism to optical measurements. This contrast is particularly important in the near-infrared (NIR) due to relative transparency of tissue as well as the broad absorption and emission spectra of dyes that are active in this region. Here we report comparative analysis of signal distribution of several NIR fluorescent polymethine dyes in living mice and their correlations with lifetimes obtained in vitro using solution models. The FLT data obtained from dyes dissolved in serum albumin solution correlated well with FLTs measured in vivo. Thus the albumin solution model could be used as a good predictive model for in vivo FLT behavior of newly developed fluorescent reporters. Subsequent experiments in vivo, including monitoring slow release kinetics and detecting proteinuria, demonstrate the complementary nature of FLT for fluorescence intensity imaging.

Since the discovery of the technique in the early 1990s, single molecule spectroscopy has been used as a powerful tool to investigate and characterize fluorescent molecules, revealing insights into molecular behavior far beyond the information content that can be obtained by conventional ensemble studies. Several spectroscopic techniques have been established at the single molecule level, including spectrally resolved fluorescence, fluorescence lifetime investigations, or single molecule Raman measurements. However, the combination of two or more of these spectroscopies applied to the same individual molecule in multiparameter approaches yields a deeper understanding of molecular systems. In this contribution, we present our results of combined spectrally- and time-resolved fluorescence microscopy of the intrinsic fluorescence energy transfer (FRET) system of the red fluorescent protein DsRed. Correlating the results obtained from the two spectroscopic techniques, we are able to determine all relevant parameters to describe the energy transfer processes within the DsRed system without any further assumptions. We further discuss fluorescence and surface enhanced Raman scattering (SERS) spectroscopy of the same individual DsRed unit, which can help to propose mechanisms for photodegeneration of the distinct chromophores involved.

Reactive oxygen species (ROS) are believed to be involved in many diseases and injuries to the brain, but the molecular processes are not well understood due to a lack of in vivo imaging techniques to evaluate ROS. The fluorescent oxidation products of dihydroethidium (DHE) can monitor ROS production in vivo. Here we demonstrate the novel optical imaging of brain in live mice to measure ROS production via generation of fluorescent DHE oxidation products (ox-DHE) by ROS. We show that in Sod2+/- mice, which have partial loss of a key antioxidant enzyme, superoxide dismutase-2, that ox-DHE fluorescence intensity was significantly higher than in hSOD1 mice, which have four-fold overexpression of superoxide dismutase-1 activity, which had almost no ox-DHE fluorescence, confirming specificity of ox-DHE to ROS production. The DHE oxidation products were also confirmed by detecting a characteristic fluorescence lifetime of the oxidation product, which was validated with ex vivo measurements.

Iridium complexes exhibit highly-efficient phosphorescence that is quenched notably by ambient molecular oxygen. We utilized the oxygen-sensitive properties of the phosphorescence to visualize tumors in vivo because the levels of oxygen in tumors may be significantly below those of normal tissue. We used (btp)₂Ir(acac) (BTP) as an oxygen probe because the phosphorescence of BTP appears in the red to near-infrared region and has a relatively long lifetime (5.8μs) and high quantum yield (0.32) in solution. The oxygen-quenching rate constants were determined to be 5.7 x 10⁴ and 1.2 x 10⁴ mmHg^-1s^-1 in n-hexane and in lipid bilayer of DMPC in Tris-HCl buffer solution, respectively, at 35°C. We took the phosphorescence image of HeLa cells that had been incubated under 5% and 20% O₂ conditions. In 20% O₂ culture condition, HeLa cells did not exhibit notable phosphorescence, while in 5% O₂ culture condition, they emitted bright red phosphorescence due to BTP. Then we tested this probe to image tumors transplanted in nude mice. After 5 minutes of the BTP injection, tumor moieties began to emit red phosphorescence and after one hour each tumor was visualized very clearly by the BTP phosphorescence that could be seen only in a low oxygen state.

Multimodal agents that serve as both probes for contrast and light-activated effectors of cellular processes in diseased tissue were developed. These agents were introduced into multicellular tumor spheroids (3D tissue models) and in the chorioallantoic membrane (CAM) of a chicken embryo. The luminescence decay was examined using a novel technique involving a spectrally-resolved fluorescence lifetime apparatus integrated with a weak electromagnet. A spectrallyresolved lifetime setup was used to identify magneto-optic species sensitive to magnetic field effects and distinguish from background emissions. We demonstrate that the applied magnetic fields can alter reaction rates and product distribution of some dyes detected by time- and spectrally-resolved luminescence changes. We will discuss the use of exogenous magneto-optical probes taken up in tumors to both induce phototoxicity, a process that is governed by complex and dynamically evolving mechanisms involving reactive oxygen species, and monitor treatment progress. The magnetic field enhancement, measured over a range of weak fields (0-300 mT) is correlated to oxygenation and may be used to monitor dynamic changes occurring due to oxygen consumption over the course of photodynamic therapy. Such online measurements provide the possibility to derive real-time information about response to treatment via monitoring magnetic field enhancement/suppression of the time-resolved, spectrally-resolved luminescence of the probe at the site of the treatment directly. Magnetic perturbation of lifetime can serve as a status reporter, providing optical feedback of oxygen-mediated treatments in situ and allowing for real-time adjustment of a phototherapy treatment plan.

Molecular imaging probes rely on high target-to-background ratios (TBR) to achieve maximum sensitivity and specificity. We utilized "quenchers" to turn off the background signal from the unbound probe and investigated the ability of specific fluorophore-quencher pairs to activate at target tissues. Both fluorophore and quencher were conjugated to a single cancer targeting molecule, either avidin or antibody. Fluorescence signal from these targeting molecules was "turned off" by the quencher in the unbound state, but was "turned on" only when the molecules bound to the cell surface target and was internalized. We tested the following fluorophore-quencher combinations based on fluorescence resonance energy transfer (FRET) pairs; OregonG-BHQ1, RhodG-BHQ1/ATTO540Q, TAMRA-QSY7/QSY21, TexRed-QSY21, Alexa647-QSY21, Cy5.5-QSY21/BHQ3 and Alexa680-QSY21/BHQ3. Among these, only RhodGATTO540Q and TAMRA-QSY7/21 pair showed activation upon cell binding/internalization. Among these combinations, TAMRA-QSY7 pair showed the highest activation (40-fold and 13-fold for avidin and antibody conjugate, respectively) as measured with an in vitro dissociation assay. The activation was dependent on the method used to conjugate fluorophores and quenchers to the targeting molecule. In vitro microscopic studies with TAMRA-QSY7 pair conjugated to avidin or antibody showed high fluorescent signal inside the target cancer cells, indicating activation after internalization. In vivo imaging studies in tumor bearing mice demonstrated that tumors could be clearly detected with low background. Although the precise quenching mechanism remains to be determined, this activation system can achieve high TBR in vivo molecular imaging.

We have developed a series of new dye bombesin conjugates for site-specific absorption and fluorescence imaging of human prostate and breast cancers. Bombesin (BBN), an amphibian analog to the endogenous ligand, binds to the gastrin releasing peptide (GRP) receptors with high specificity and affinity. Previously, we developed an Alexa Fluor 680-GGG-BBN peptide conjugate which demonstrated high binding affinity and specificity for breast cancer cells in the in vitro and in vivo tests (Ref: Ma et al., Molecular Imaging, vol. 6, no. 3, 2007: 171-180). This probe can not be used as an absorption probe in near-infrared imaging because its absorption peak is in the visible wavelength range. In addition, site specific longer wavelength fluorescent probe is desired for in vivo molecular imaging because long wavelength photons penetrate deeper into tissue. The new absorption and fluorescent probe we developed is based on the last eight-residues of BBN, -Q-W-A-V-G-H-L-M-(NH₂), and labeled with AlexaFluor750 through a chemical linker, beta-alanine. The new probe, Alexa Fluor 750-BetaAla-BBN(7-14)NH₂, exhibits optimal pharmacokinetics for specific targeting and optical imaging of the GRP receptor over-expressing cancer cells. Absorption spectrum has been measured and showed absorption peaks at 690nm, 720nm and 735nm. Fluorescent band is located at 755nm. In vitro and in vivo investigations have demonstrated the effectiveness of the new conjugates to specifically target human cancer cells overexpressing GRP receptors and tumor xenografts in severely compromised immunodeficient mouse model.

The prevalence of the gelatinases, MMP-2 and MMP-9, in many human tumors, including breast, colorectal, prostate and gastric cancer, make them an attractive target for molecular imaging. A self assembling homotrimeric triple helical peptide (THP), incorporating sequences from type V collagen with high specificity to MMP-2 and MMP-9, was previously developed. To investigate the viability of a THP for gelatinase imaging, we conjugated 5FAM to ..-amino groups of lysine flanking the hydrolysis site and subjected this substrate (THP-5FAM) to vitro analysis. The synthesis and in vitro results was presented.

We have designed and studied the photophysics of a class of organic fluorophores termed "DCDHFs," which were originally used as push-pull chromophores for nonlinear optical applications. In this paper, we describe the general photophysics of many realizations of the DCDHF class of single-molecule emitters. Moreover, we have reengineered a red-emitting DCDHF fluorophore so that it is dark until photoactivated with a short burst of low-intensity violet light. Photoactivation of the dark fluorogen leads to conversion of an azide to an amine, which shifts the absorption to long wavelengths. After photoactivation, the fluorophore is bright and photostable enough to be imaged on the singlemolecule level in living cells. This molecule and its relatives will provide a new class of bright photoactivatable fluorophores, as are needed for super-resolution imaging schemes that require active control of single-molecule emission.

Solid tumors possess unique microenvironments that are exposed to chronic hypoxic conditions ("tumor hypoxia"). Although more than half a century has passed since it was suggested that tumor hypoxia correlated with poor treatment outcomes and contributed to cancer recurrence, a fundamental solution to this problem has yet to be found. Hypoxia-inducible factor (HIF-1) is the main transcription factor that regulates the cellular response to hypoxia. It induces various genes whose functions are strongly associated with malignant alteration of the entire tumor. The cellular changes induced by HIF-1 are extremely important targets of cancer therapy, particularly in therapy against refractory cancers. Imaging of the HIF-1-active microenvironment is therefore important for cancer therapy. To image HIF-1activity in vivo, we developed a PTD-ODD fusion protein, POHA, which was uniquely labeled with near-infrared fluorescent dye at the C-terminal. POHA has two functional domains: protein transduction domain (PTD) and VHL-mediated protein destruction motif in oxygen-dependent degradation (ODD) domain of the alpha subunit of HIF-1 (HIF-1α). It can therefore be delivered to the entire body and remain stabilized in the HIF-1-active cells. When it was intravenously injected into tumor-bearing mice, a tumor-specific fluorescence signal was detected in the tumor 6 h after the injection. These results suggest that POHA can be used an imaging probe for tumor malignancy.

We report on a new application of laser induced breakdown spectroscopy (LIBS) for the diagnosis of diseases such as ovarian cancer. We perform detection of ovarian cancer biomarker CA 125 based on LIBS measurements. Immunoconjugated Silicon particles are incubated with the affinity agarose beads carrying CA125 molecules. In the competitive affinity method Si particles carrying IgG molecules are pre-incubated with CA125. This pre-incubation decreases the numbers of free IgG molecules available for consequent interaction with the affinity beads. Thus less Si particles are attached to the agarose beads and consequently smaller Si peak area is measured by LIBS. We demonstrate a limit-ofdetection about 30 ppb for model protein avidin. We use two-element coded micro-particles to yield spectroscopic emission code using LIBS. We show that LIBS-based data collecting technique provides methodology for identification of biomarkers and cost-effective device for future clinical applications.

Anisotropic metal nanoparticles strongly change the scattered light polarization compared with isotropic nanoparticles, and this property can be utilized in a sensitive bimolecular recognition due to the high contrast that could be achieved in polarization microscopy. We report a study of the shape anisotropy in nearly spherical gold nanoparticles and particle dimers. It was obvious that each particle has its own scattering polarization dependence which reflects the relative changes in morphologies. Our experimental results reveal that particles with minimum anisotropy don't change the scattering light polarization which indicates their homogenous shape. Another particles show polarization dependence scattering intensity due to pronounced anisotropy. Particle dimers possess shape anisotropy that is characterized by a different polarizability for each axis in the nanostructure. We resolved the internal inhomogeneity in single particles and particle dimers using a qualitative analysis which enabled us to determine the polarizabilities of both long and short axes for each particle and particle pair. A few of single particles show a strong optical anisotropy relative to their shape anisotropy, and even this observation was not yet clarified, it could be used in a sensitive bimolecular detection.

In this paper, we investigated carefully the influence of the added L-cysteine on the stability of mercaptopropionic acid (MPA)-stabilized CdTe nanoparticles (NPs). Transmission electron microscopy (TEM) imaging revealed that the addition of pH ~11.5 L-cysteine solution could reduce the stability of MPA-capped CdTe NPs, which resulted in the formation of sheet-shaped nanostructures finally after about seven days of storage in darkness under ambient conditions. The typical size of these resulting nanosheets was ~6 μm in length, ~1 μm in width and ~50 nm in thickness. The high-resolution TEM characterization and elemental analysis from energy-dispersed X-ray (EDX) spectrum indicated that these resulting sheets were made from well-crystallized nanopartilces (~4 nm) of CdS rather than CdTe. In addition, XRD analysis and optical microscopy also supported further these experimental observations. Hence, here, the post addition of L-cysteine induced the spontaneous transition and concomitant self-assembly of MPA-stabilized CdTe nanoparticles into luminescent CdS nanosheets.

Tumor invasion to the peritoneum is a poor prognostic factor in cancer patients. Accurate diagnosis of disseminated peritoneal tumors is essential to accurate cancer staging. To date, peritoneal washing cytology during laparotomy has been used for diagnosis of peritoneal dissemination of gastrointestinal cancer, but its sensitivity has not been satisfactory. Thus, a more direct approach is indispensable to detect peritoneal dissemination in vivo. Fluorescein diacrylate (FDAcr) is an esterase-sensitive fluorescent probe derived from fluorescein. In cancer cells, fluorescent fluorescein generated by exogenous application of FDAcr selectively deposits owing to its stronger hydrolytic enzyme activity and its lower leakage rate. We examined whether FDAcr can specifically detect disseminated peritoneal tumors in athymic nude mouse models. Intraperitoneally administered FDAcr revealed disseminated peritoneal microscopic tumors not readily recognized on white-light imaging. These results suggest that FDAcr is a useful probe for detecting disseminated peritoneal tumors.

One goal of molecular imaging is to establish a widely applicable technique for specific detection of tumors with minimal background. Here, we achieve specific in vivo tumor visualization with a newly-designed "activatable" targeted fluorescence probe. This agent is activated after cellular internalization by sensing the pH change in the lysosome. Novel acidic pH-activatable probes based on the BODIPY fluorophore were synthesized, and then conjugated to a cancer-targeting monoclonal antibody, Trastuzumab, or galactosyl serum albumin (GSA). As proof of concept, ex and in vivo imaging of two different tumor mouse models was performed: HER2-overexpressed lung metastasis tumor with Trastuzumab-pH probe conjugates and lectin-overexpressed i.p. disseminated tumor with GSA-pH probe conjugates. These pH-activatable targeted probes were highly specific for tumors with minimal background signal. Because the acidic pH in lysosomes is maintained by the energy-consuming proton pump, only viable cancer cells were successfully visualized. Furthermore, this strategy was also applied to fluorescence endoscopy in tumor mouse models, resulting in specific visualization of tumors as small as submillimeter in size that could hardly detected by naked eyes because of their poor contrast against normal tissues. The design concept can be widely adapted to cancer-specific cell-surface-targeting molecules that result in cellular internalization.