Intraoperative identification of esophageal sentinel lymph nodes with near-infrared fluorescence imaging

Current concepts and future perspectives on surgical optical imaging in cancer

There are vibrant developments of optical imaging systems and contrast-enhancing methods that are geared to enhancing surgical vision and the outcome of surgical procedures. Such optical technologies designed for intraoperative use can offer high integration in the operating room compared to conventional radiological modalities adapted to intraoperative applications. Simple fluorescence epi-illumination imaging, in particular, appears attractive but may lead to inaccurate observations due to the complex nature of photon-tissue interaction. Of importance therefore are emerging methods that account for the background optical property variation in tissues and can offer accurate, quantitative imaging that eliminates the appearance of false negatives or positives. In parallel, other nonfluorescent optical imaging methods are summarized and overall progress in surgical optical imaging applications is outlined. Key future directions that have the potential to shift the paradigm of surgical health care are also discussed.

Gadolinium chloride augments tumor-specific imaging of targeted quantum dots in vivo

Nonspecific sequestration of nanoparticles by the reticulo-endothelial system (RES) results in the degradation of image quality of nanoparticle-based imaging. We demonstrate that gadolinium chloride (GdCl3) pretreatment inactivates RES macrophages, thereby increasing circulatory time and amplifying the tumor-specific signal of conjugated nanoparticles in vivo. The experimental results were validated using compartmental modeling, and the rate parameters for the observed kinetics pattern were estimated. This pretreatment strategy could have broad applicability across biomedical applications utilizing theranostic nanoparticles that are sequestered by the RES.

Real-time optical imaging using quantum dot and related nanocrystals

Biomedical optical imaging is rapidly evolving because of its desirable features of rapid frame rates, high sensitivity, low cost, portability and lack of radiation. Quantum dots are attractive as imaging agents owing to their high brightness, and photo- and bio-stability. Here, the current status of in vitro and in vivo real-time optical imaging with quantum dots is reviewed. In addition, we consider related nanocrystals based on solid-state semiconductors, including upconverting nanoparticles and bioluminescence resonance energy transfer quantum dots. These particles can improve the signal-to-background ratio for real-time imaging largely by suppressing background signal. Although toxicity and biodistribution of quantum dots and their close relatives remain prime concerns for translation to human imaging, these agents have many desirable features that should be explored for medical purposes.

Clinical potential of quantum dots

Advances in nanotechnology have led to the development of novel fluorescent probes called quantum dots. Quantum dots have revolutionalized the processes of tagging molecules within research settings and are improving sentinel lymph node mapping and identification in vivo studies. As the unique physical and chemical properties of these fluorescent probes are being unraveled, new potential methods of early cancer detection, rapid spread and therapeutic management, that is, photodynamic therapy are being explored. Encouraging results of optical and real time identification of sentinel lymph nodes and lymph flow using quantum dots in vivo models are emerging. Quantum dots have also superseded many of the limitations of organic fluorophores and are a promising alternative as a research tool. In this review, we examine the promising clinical potential of quantum dots, their hindrances for clinical use and the current progress in abrogating their inherent toxicity.

Therapeutic sentinel lymph node imaging

Improving existing means of sentinel lymph node identification in non-small cell lung cancer will allow for molecular detection of occult micrometastases that may cause recurrence in early stage non-small cell lung cancer. Furthermore, targeted application of chemical and biological cytotoxic agents can potentially improve outcomes in patients with lymph node (LN) metastases. "Therapeutic Sentinel Lymph Node Imaging" incorporates these modalities into a single agent thereby identifying which LNs harbor tumor cells and simultaneously eradicating metastatic disease. In this review, we summarize the novel preclinical agents for identification and treatment of tumor bearing LNs and discuss their potential for clinical translation.

Image-guided sentinel lymph node mapping and nanotechnology-based nodal treatment in lung cancer using invisible near-infrared fluorescent light

Current methods for sentinel lymph node (SLN) mapping and nodal treatment in lung cancer remain inadequate for routine clinical use. In this study, we discuss the potential for using the combination of invisible near-infrared (NIR) fluorescent light and nanotechnology for these applications. NIR fluorescence imaging has recently received significant attention for in vivo imaging applications because of its low tissue autofluorescence, high photon penetration into living tissue, and high signal-to-background ratio. Our large animal in vivo studies have been able to successfully identify SLNs in lung tissue, and several clinical studies have examined the use of NIR fluorescence imaging systems for SLN mapping in breast and gastric cancer. Promising new nanoparticle technologies, when combined with NIR fluorescence imaging, offer the potential for image-guided treatment of lymph nodes at high risk for tumor recurrence. This review provides a theoretic and empiric framework for developing the next generation of diagnostic and therapeutic agents for lung cancer.

Nanotechnology applications in surgical oncology

Surgery is currently the most effective and widely used procedure in treating human cancers, and the single most important predictor of patient survival is a complete surgical resection. Major opportunities exist to develop new and innovative technologies that could help the surgeon to delineate tumor margins, to identify residual tumor cells and micrometastases, and to determine if the tumor has been completely removed. Here we discuss recent advances in nanotechnology and optical instrumentation, and how these advances can be integrated for applications in surgical oncology. A fundamental rationale is that nanometer-sized particles such as quantum dots and colloidal gold have functional and structural properties that are not available from either discrete molecules or bulk materials. When conjugated with targeting ligands such as monoclonal antibodies, peptides, or small molecules, these nanoparticles can be used to target malignant tumor cells and tumor microenvironments with high specificity and affinity. In the "mesoscopic" size range of 10-100 nm, nanoparticles also have large surface areas for conjugating to multiple diagnostic and therapeutic agents, opening new possibilities in integrated cancer imaging and therapy.

Near-infrared quantum dots for deep tissue imaging

Developments in nanotechnology have paved the way for the early detection, treatment, and prevention of several tumors which affect mankind. In the past few years, near-infrared (NIR) fluorescence imaging techniques have emerged that enable the in vivo imaging of physiological, metabolic, and molecular function. The NIR window, also known as the diagnostic window (700-900 nm), can be explored for sensitive detection techniques. Nanoparticles, particularly semiconductor quantum dots (QDs), can be utilized for the purpose of optical imaging. These semiconductor QDs possess novel electronic, optical, magnetic, and structural properties which are quite different from those of bulk materials. NIR QDs with these unique properties can be utilized as contrast agents for optical imaging, particularly for deep tissue imaging. Deep tissue imaging provides more information about the pathological status of the disease, which makes the treatment more effective and efficient. In this review we highlight the importance of NIR QDs as probes for optical imaging. We describe the different types of NIR QDs, their synthesis, and their application for deep tissue imaging along with recently developed self-illuminating NIR QDs.

Optical small animal imaging in the drug discovery process

Molecular imaging of tumors in preclinical models is of the utmost importance for developing innovative cancer treatments. This field is moving extremely rapidly, with recent advances in optical imaging technologies and sophisticated molecular probes for in vivo imaging. The aim of this review is to provide a succinct overview of the imaging modalities available for rodents and with focus on describing optical probes for cancer imaging.

Transfer of quantum dots from pregnant mice to pups across the placental barrier

Fluorescent quantum dots (QDs) have great potential for in vivo biomedical imaging and diagnostic applications. However, these nanoparticles are composed of heavy metals and are very small in diameter, and their possible toxicity must therefore be considered. As yet, no studies have reported the transfer of QDs between mother and fetus. The transfer of CdTe/CdS QDs of different sizes and dosages, and with different outer capping materials, from pregnant mice to fetuses is investigated. It is shown that QDs may be transferred from female mice to their fetuses across the placental barrier. Smaller QDs are more easily transferred than larger QDs and the number of QDs transferred increases with increasing dosage. Capping with an inorganic silica shell or organic polyethylene glycol reduces QD transfer but does not eliminate it. These results suggest that the clinical utility of QDs could be limited in pregnant women.

Evaluation of sentinel node biopsy by combined fluorescent and dye method and lymph flow for breast cancer

BACKGROUND

Conservative breast resection with subsequent sentinel lymph node biopsy (SNB) is an increasingly popular initial approach for the treatment of breast cancer due to decreased invasiveness. SNB is a shorter procedure with fewer side effects than more substantial surgical procedures, but it sometimes fails to identify metastatic disease. Therefore, a highly sensitive and convenient method is needed to identify sentinel lymph nodes (SLN) with a high probability of containing disease in SNB. We compared the combination of radioisotope or dye with a fluorescence compound to analyze lymph flow to identify targets for SNB.

MATERIALS AND METHODS

We examined patients with breast cancer lacking metastases in the axillary lymph node (ALN). Two methods for targeted SNB were developed: (1) Indocyanine Green (ICG) and Patent blue were injected into the skin overlying the tumor and sub-areolar region just before the surgical procedure. (2) ICG and radiocolloid were injected into the skin overlying the tumor and sub-areolar region. The draining fluorescent lymphatic duct was visualized using a Photodynamic Eye (PDE). We removed the SLNs that were identified by the dye and fluorescence imaging methods. Method 1 was applied to 113 patients undergoing SNB, and 29 patients were treated with Method 2. In our study, patients were grouped by lymph flow into two types: Type C demonstrated convergence to one lymph duct. Type S demonstrated separate lymph ducts.

RESULTS

Using the fluorescence imaging method, 99.3% of SLNs were identified, and 3.8 SLNs per patient were seen. The SLN identification rates for Patent blue dye and radiocolloid were 92.9% and 100%, respectively, while 1.9 and 2.0 SLNs per patient, respectively, were seen with these methods. We classified two types of lymph flow based on the pattern of lymphatic drainage. Type C converged to a single lymph duct, while Type S drained to separate ducts. Type S lymph drainage was seen in 29/142 patients (20.4%), and Type C drainage was found in 113/141 patients (79.6%). Of the patients with Type S drainage, there were 4.1 SLNs per patient, but only 3.4 SLNs per patient were seen in individuals with Type C drainage. Forty cases had metastases found in the ALNs, and five of these cases were dye-negative and fluorescence-positive. Among these cases, the average number of SLNs identified was one.

CONCLUSION

The combination of fluorescence with a visible dye is a highly sensitive method for SLN identification. When SNB is guided by only the dye method, there is a risk of missing appropriate SLNs in patients with Type S lymph drainage or weak dye staining. The use of a fluorescence method together with dye could increase sensitivity of detection in these cases. Furthermore, fluorescent methods are ideal for hospitals that cannot use conventional radioactive measures.

Multicolor fluorescent intravital live microscopy (FILM) for surgical tumor resection in a mouse xenograft model

Background

Complete surgical resection of neoplasia remains one of the most efficient tumor therapies. However, malignant cell clusters are often left behind during surgery due to the inability to visualize and differentiate them against host tissue. Here we establish the feasibility of multicolor fluorescent intravital live microscopy (FILM) where multiple cellular and/or unique tissue compartments are stained simultaneously and imaged in real time.

Methodology/Principal Findings

Theoretical simulations of imaging probe localization were carried out for three agents with specificity for cancer cells, stromal host response, or vascular perfusion. This transport analysis gave insight into the probe pharmacokinetics and tissue distribution, facilitating the experimental design and allowing predictions to be made about the localization of the probes in other animal models and in the clinic. The imaging probes were administered systemically at optimal time points based on the simulations, and the multicolor FILM images obtained in vivo were then compared to conventional pathological sections. Our data show the feasibility of real time in vivo pathology at cellular resolution and molecular specificity with excellent agreement between intravital and traditional in vitro immunohistochemistry.

Conclusions/Significance

Multicolor FILM is an accurate method for identifying malignant tissue and cells in vivo. The imaging probes distributed in a manner similar to predictions based on transport principles, and these models can be used to design future probes and experiments. FILM can provide critical real time feedback and should be a useful tool for more effective and complete cancer resection.

Fluorescence imaging and whole-body biodistribution of near-infrared-emitting quantum dots after subcutaneous injection for regional lymph node mapping in mice

PURPOSE

This study compares fluorescence imaging to mass spectroscopy (inductively coupled plasma-mass spectroscopy, ICP-MS) for detection of quantum dots (QDs) in sentinel lymph node (LN) mapping of breast cancer.

PROCEDURES

We study the accumulation of near-infrared-emitting QDs into regional LNs and their whole-body biodistribution in mice after subcutaneous injection, using in vivo fluorescence imaging and ex vivo elemental analysis by ICP-MS.

RESULTS

We show that the QD accumulation in regional LNs is detectable by fluorescence imaging as early as 5 min post-delivery. Their concentration reaches a maximum at 4 h then decreases over a 10-day observation period. These data are confirmed by ICP-MS. The QD uptake in other organs, assessed by ICP-MS, increases steadily over time; however, its overall level remains rather low.

CONCLUSIONS

Fluorescence imaging can be used as a non-invasive alternative to ICP-MS to follow the QD accumulation kinetics into regional LNs.

The use of fluorescent dyes and probes in surgical oncology

AIMS AND BACKGROUND

Improved visualization of surgical targets inside of the patient helps to improve radical resection of the tumor while sparing healthy surrounding tissue. In order to achieve an image, optical contrast must be generated by properties intrinsic to the tissue, or require the attachment of special visualization labels to the tumor. In this overview the current status of the clinical use of fluorescent dyes and probes are reviewed.

METHODS

In this review, all experimental and clinical studies concerning fluorescent imaging were included. In addition, in the search for the optimal fluorescent imaging modality, all characteristics of a fluorescent dye were described.

FINDINGS AND CONCLUSIONS

Although the technique of imaging through fluorescence sounds promising and several animal models show efficacy, official approval of these agents for further clinical evaluation, is eagerly awaited.

Intraoperative fluorescent imaging using indocyanine green for liver mapping and cholangiography

BACKGROUND

Preoperative imaging is widely used and extremely helpful in hepatobiliary surgery. However, transfer of preoperative data to a intraoperative situation is very difficult. Surgeons need intraoperative anatomical information using imaging data for safe and precise operation in the field of hepatobiliary surgery. We have developed a new system for mapping liver segments and cholangiograms using intraoperative indocyanine green (ICG) fluorescence under infrared light observation.

METHOD

The imaging technique for mapping liver segments and cholangiogram based on ICG fluorescence used an infrared-based navigation system. Eighty one patients with liver tumors underwent hepatectomy from 2006, January to 2009, March. In liver surgery, 1 ml of ICG was injected via the portal vein under observation by the fluorescent imaging system. Fourteen patients were underwent laparoscopic cholecystectomy for chronic cholecystitis with gallstones. In laparoscopic cholecystectomy, 5 ml of ICG was administered intravenously just before operation and the bile duct was observed using the infrared-based navigation system.

RESULT

This new technique successfully identified stained subsegments and segments of the liver in 73 of 81 patients (90.1%). Moreover, clear mapping of liver segments was obtained even against a background of liver cirrhosis. Fluorescent cholangiography clearly showed the common bile duct and cystic duct in 10 of 14 patients (71.4%). No adverse reactions to the ICG were encountered.

CONCLUSION

Application of this technique allows intraoperative identification of anatomical landmark in hepatobiliary surgery.

Sentinel lymph node mapping using near-infrared fluorescent methylene blue

Methylene blue (MB) is a safe, low cost, and common blue dye remaining a popular choice for sentinel lymph node (SLN) mapping. However, the blue-dyed SLN in deep animal tissue could be seen only after a surgical management. Here the fluorescence properties of MB were investigated using a fluorescence spectrometer and a wavelength-resolved fluorescence spectral in vivo imaging system, and MB has been demonstrated for near-infrared (NIR) fluorescence mapping of SLN. When MB was injected intradermally into the second row breast of a rabbit, the lymphatic flow and axillary SLN could be observed directly through the NIR fluorescence emitted from the MB trapped in the deep tissue, which would eliminate the need for surgical management, and this fluorescence without any radioactivity was retained in the SLN for hours. The node also could be identified synchronously by the blue color and fluorescence of the MB after a surgical management. Using MB NIR fluorescence for SLN mapping may have great advantages over the traditional method.

The FLARE intraoperative near-infrared fluorescence imaging system: a first-in-human clinical trial in breast cancer sentinel lymph node mapping

BACKGROUND

Invisible NIR fluorescent light can provide high sensitivity, high-resolution, and real-time image-guidance during oncologic surgery, but imaging systems that are presently available do not display this invisible light in the context of surgical anatomy. The FLARE imaging system overcomes this major obstacle.

METHODS

Color video was acquired simultaneously, and in real-time, along with two independent channels of NIR fluorescence. Grayscale NIR fluorescence images were converted to visible "pseudo-colors" and overlaid onto the color video image. Yorkshire pigs weighing 35 kg (n = 5) were used for final preclinical validation of the imaging system. A six-patient pilot study was conducted in women undergoing sentinel lymph node (SLN) mapping for breast cancer. Subjects received (99m)Tc-sulfur colloid lymphoscintigraphy. In addition, 12.5 microg of indocyanine green (ICG) diluted in human serum albumin (HSA) was used as an NIR fluorescent lymphatic tracer.

RESULTS

The FLARE system permitted facile positioning in the operating room. NIR light did not change the look of the surgical field. Simultaneous pan-lymphatic and SLN mapping was demonstrated in swine using clinically available NIR fluorophores and the dual NIR capabilities of the system. In the pilot clinical trial, a total of nine SLNs were identified by (99m)Tc- lymphoscintigraphy and nine SLNs were identified by NIR fluorescence, although results differed in two patients. No adverse events were encountered.

CONCLUSIONS

We describe the successful clinical translation of a new NIR fluorescence imaging system for image-guided oncologic surgery.

Fluorescent tumour imaging of type I IGF receptor in vivo: comparison of antibody-conjugated quantum dots and small-molecule fluorophore

Background:

The type I insulin-like growth factor receptor (IGF1R) is a transmembrane tyrosine kinase involved in cancer proliferation, survival, and metastasis.

Methods:

In this study, we used two different fluorescent technologies (small-molecule fluorophores and quantum dot (QD) nanoparticles) to detect receptor expression and its downregulation by antibodies in vivo.

Results:

After conjugation with AVE-1642, a humanised anti-IGF1R monoclonal antibody, both QDs (705 nm) or Alexa 680 (small-molecule fluorophore) detected expression and downregulation of IGF1R in vitro. To examine their utility in vivo, either AVE-1642 conjugates were intravenously delivered to mice bearing xenograft tumours of mouse embryo fibroblasts expressing human IGF1R or MCF-7 human breast cancer cells. Quantum dot fluorescence was mainly localised to the reticuloendothelial system in several organs and engulfed by macrophages, with only very small amount of QDs detected in the xenograft tumours. Depletion of macrophages by clodronate liposomes did not alter the nonspecific uptake of QDs. In contrast, AVE-1642-conjugated Alexa 680 solely targeted to xenograft tumour and was able to detect IGF1R downregulation, with little nonspecific targeting to other tissues or organs in mice.

Conclusion:

Taken together, our data suggest that small-molecule fluorophores, not QDs, are suitable to detect the expression and downregulation of IGF1R in vivo.

Nanoparticles and cancer therapy: a concise review with emphasis on dendrimers

The emergence of nanotechnology has had a profound effect on many areas of healthcare and scientific research. Having grown exponentially, the focus of nanotechnology has been on engineering diversified novel applications that even go beyond therapeutic activity; nanotechnology also offers the ability to detect diseases, such as cancer, much earlier than ever imaginable. Often, patients diagnosed with breast, lung, colon, prostate, and ovarian cancer have hidden or overt metastatic colonies. With the advent of diagnostic nanotechnology, these numbers are expected to greatly diminish. This review provides a brief description of nanoparticle (liposome, quantum dot, and dendrimer)-mediated cancer therapy in the last decade with an emphasis on the development and use of dendrimers in cancer therapeutics.

Immune response induced by fluorescent nanocrystal quantum dots in vitro and in vivo

Fluorescent nanocrystal quantum dots (QDs) are widely used as novel tools in various biological fields including cellular biology, molecular biology, and even in basic and clinical medical fields, due to their far brighter photoemission and photostability. Although many amounts of biological studies, including in vivo experiments, were circumstantially investigated, there is no informative report that investigates whether the QDs affect the mammalian immune system. This study investigated the immune response and biological behavior of QDs in vitro and in vivo. The immune response to QDs by both lymphocytes and kinds of macrophages in vitro and in vivo was investigated. Co-culture of QDs with immune cells showed that apparently normal production of cytokines and chemokines in both mouse CD4+ lymphocytes and peritoneal F4/80+ macrophages (PM phi). In addition, the bionanocomplex of QDs with enhanced-green-fluorescent-protein (eGFP)-encoding nucleotides successfully induced the expression of eGFP protein by PM phi. However, direct injection of QD+nucleotides bionanocomplex aqueous solution into the peritoneal cavity of mice resulted in the inflammation with the infiltration of inflammatory cells into the peritoneal cavity. Furthermore, QD+nucleotides bionanocomplex (but not QD bionanocomplex without nucleotides), induced the production of both proinflammatory cytokines and chemokines by PM phi in vitro. These results indicated that QDs covered with nucleotides caused the peritoneal inflammation in vivo via activation of PM phi and probably nonimmune cells. Taken together, these data indicated that QDs affect the proliferation of immune cells, but not in immune response including cytokine production. We propose here that all nanotechnology researchers should confirm the biological responses of their nanoscale products, because the biological response against nanoscale products can be occurred by not only in immune cells but also other nonimmune cells.

Lymphatic imaging in humans with near-infrared fluorescence

While the lymphatic system is increasingly associated with diseases of prevalence, study of these diseases is difficult owing to the paucity of imaging techniques with the sensitivity and temporal resolution to discriminate lymphatic function. Herein, we review the known, pertinent features of the human lymphatic system in health and disease and set the context for a number of emerging studies that use near-infrared fluorescence imaging to non-invasively assess tumor draining lymphatic basins in cancer patients, intraoperatively guide resection of first draining lymph nodes, and to interrogate the difference between normal and aberrant lymphatic structure and function.

Image-guided liver mapping using fluorescence navigation system with indocyanine green for anatomical hepatic resection

BACKGROUND

In malignant hepatic neoplasm, anatomic resection could improve survival and limit complications from hepatectomy. Our purpose was to develop an intraoperative method for identifying segment and subsegment of the liver with high-sensitivity near-infrared fluorescence imaging.

METHODS

The subjects were 35 patients with hepatic malignant liver disease who received hepatectomy in 2006. The segments of liver method of identification that used infrared observation camera system termed Photo Dynamic Eye-2 (PDE-2) with indocianine green (ICG) for the patient with malignant liver tumor (hepatocellular carcinoma: 13 cases; metastatic liver cancer: 18 cases; intrahepatic cholangio carcinoma: 4 cases) were performed before liver resection.

RESULTS

Although greenish stain of the liver surface after the injection of ICG via portal vein is not visible clearly without infrared observation camera system PDE-2, 1 minute after injection of ICG with fluorescent using infrared observation camera system PDE-2, demarcation of liver segment and subsegment was clearly detected. Ten minutes after injection of ICG with fluorescent using infrared observation camera system PDE-2, fluorescence of liver subsegment remained. Stained subsegment and segment of liver were identifiable in 33 (94.3%) of the 35 patients. There were no complications or side-effects related to the injection of patent blue dye.

CONCLUSION

We demonstrated here that near-infrared fluorescence imaging system is a novel and reliable intraoperative technique to identify hepatic segment and subsegment for anatomical hepatic resection.

Imaging vasculature and lymphatic flow in mice using quantum dots

Quantum dots are ideal probes for fluorescent imaging of vascular and lymphatic tissues. On injection into appropriate sites, red- and near-infrared-emitting quantum dots provide excellent definition of vasculature, lymphoid organs, and lymph nodes draining both normal tissues and tumors. We detail methods for use with commercially available quantum dots and discuss common difficulties.

Particle size, surface coating, and PEGylation influence the biodistribution of quantum dots in living mice

This study evaluates the influence of particle size, PEGylation, and surface coating on the quantitative biodistribution of near-infrared-emitting quantum dots (QDs) in mice. Polymer- or peptide-coated 64Cu-labeled QDs 2 or 12 nm in diameter, with or without polyethylene glycol (PEG) of molecular weight 2000, are studied by serial micropositron emission tomography imaging and region-of-interest analysis, as well as transmission electron microscopy and inductively coupled plasma mass spectrometry. PEGylation and peptide coating slow QD uptake into the organs of the reticuloendothelial system (RES), liver and spleen, by a factor of 6-9 and 2-3, respectively. Small particles are in part renally excreted. Peptide-coated particles are cleared from liver faster than physical decay alone would suggest. Renal excretion of small QDs and slowing of RES clearance by PEGylation or peptide surface coating are encouraging steps toward the use of modified QDs for imaging living subjects.

Fluorescent labeled anti-EGFR antibody for identification of regional and distant metastasis in a preclinical xenograft model

BACKGROUND

Detection of regional and distant metastatic disease has significant implications for patient management. Fluorescent imaging may be a useful technique for metastasis detection and removal.

METHODS

Anti-epidermal growth factor receptor antibody (cetuximab) and isotype-matched control antibody (immunoglobulin G [IgG]) were labeled with a near-infrared fluorophore (Cy5.5), then systemically administered to mice with tumors resulting from either intraoral or intravenous injections of head and neck squamous cell carcinoma. Mice were sacrificed before undergoing fluorescent stereomicroscopy to assess pulmonary or cervical lymph node metastasis. Fluorescent areas were serially excised until wound bed demonstrated negative fluorescence.

RESULTS

Mice bearing pulmonary metastases displayed diffuse background after IgG-Cy5.5 injection, but demonstrated a speckled fluorescent pattern across lung surface following cetuximab-Cy5.5 injection. Mice bearing cervical metastases demonstrated clear fluorescence of primary tongue tumor and bilateral cervical nodes. Fluorescence correlated with histopathology.

CONCLUSION

These data suggest that cetuximab-Cy5.5 may have clinical utility in the detection and guided the removal of regional and distant micrometastasis.

New technologies for human cancer imaging

Despite technical advances in many areas of diagnostic radiology, the detection and imaging of human cancer remains poor. A meaningful impact on cancer screening, staging, and treatment is unlikely to occur until the tumor-to-background ratio improves by three to four orders of magnitude (ie, 10(3)- to 10(4)-fold), which in turn will require proportional improvements in sensitivity and contrast agent targeting. This review analyzes the physics and chemistry of cancer imaging and highlights the fundamental principles underlying the detection of malignant cells within a background of normal cells. The use of various contrast agents and radiotracers for cancer imaging is reviewed, as are the current limitations of ultrasound, x-ray imaging, magnetic resonance imaging (MRI), single-photon emission computed tomography, positron emission tomography (PET), and optical imaging. Innovative technologies are emerging that hold great promise for patients, such as positron emission mammography of the breast and spectroscopy-enhanced colonoscopy for cancer screening, hyperpolarization MRI and time-of-flight PET for staging, and ion beam-induced PET scanning and near-infrared fluorescence-guided surgery for cancer treatment. This review explores these emerging technologies and considers their potential impact on clinical care. Finally, those cancers that are currently difficult to image and quantify, such as ovarian cancer and acute leukemia, are discussed.

Functionalized-quantum-dot-liposome hybrids as multimodal nanoparticles for cancer

Functionalized-quantum-dot-liposome (f-QD-L) hybrid nanoparticles are engineered by encapsulating poly(ethylene glycol)-coated QD in the internal aqueous phase of different lipid bilayer vesicles. f-QD-L maintain the QD fluorescence characteristics as confirmed by fluorescence spectroscopy, agarose gel electrophoresis, and confocal laser scanning microscopy. Cationic f-QD-L hybrids lead to dramatic improvements in cellular binding and internalization in tumor-cell monolayer cultures. Deeper penetration into three-dimensional multicellular spheroids is obtained for f-QD-L by modifying the lipid bilayer characteristics of the hybrid system. f-QD-L are injected intratumorally into solid tumor models leading to extensive fluorescent staining of tumor cells compared to injections of the f-QD alone. f-QD-L hybrid nanoparticles constitute a versatile tool for very efficient labeling of cells ex vivo and in vivo, particularly when long-term imaging and tracking of cells is sought. Moreover, f-QD-L offer many opportunities for the development of combinatory therapeutic and imaging (theranostic) modalities by incorporating both drug molecules and QD within the different compartments of a single vesicle.

Bioconjugated quantum dots for in vivo molecular and cellular imaging

Semiconductor quantum dots (QDs) are tiny light-emitting particles on the nanometer scale, and are emerging as a new class of fluorescent labels for biology and medicine. In comparison with organic dyes and fluorescent proteins, they have unique optical and electronic properties, with size-tunable light emission, superior signal brightness, resistance to photobleaching, and broad absorption spectra for simultaneous excitation of multiple fluorescence colors. QDs also provide a versatile nanoscale scaffold for designing multifunctional nanoparticles with both imaging and therapeutic functions. When linked with targeting ligands such as antibodies, peptides or small molecules, QDs can be used to target tumor biomarkers as well as tumor vasculatures with high affinity and specificity. Here we discuss the synthesis and development of state-of-the-art QD probes and their use for molecular and cellular imaging. We also examine key issues for in vivo imaging and therapy, such as nanoparticle biodistribution, pharmacokinetics, and toxicology.

New horizons for imaging lymphatic function

In this review, we provide a comprehensive summary of noninvasive imaging modalities used clinically for the diagnosis of lymphatic diseases, new imaging agents for assessing lymphatic architecture and cancer status of lymph nodes, and emerging near-infrared (NIR) fluorescent optical imaging technologies and agents for functional lymphatic imaging. Given the promise of NIR optical imaging, we provide example results of functional lymphatic imaging in mice, swine, and humans, showing the ability of this technology to quantify lymph velocity and frequencies of propulsion resulting from the contractility of lymphatic structures.

Imaging epidermal growth factor receptor expression in vivo: pharmacokinetic and biodistribution characterization of a bioconjugated quantum dot nanoprobe

PURPOSE

To develop and validate an optical imaging nanoprobe for the discrimination of epidermal growth factor (EGF) receptor (EGFR)-overexpressing tumors from surrounding normal tissues that also expresses EGFR.

EXPERIMENTAL DESIGN

Near-infrared (NIR) quantum dots (QD) were coupled to EGF using thiol-maleimide conjugation to create EGF-QD nanoprobes. In vitro binding affinity of these nanoprobes and unconjugated QDs was evaluated in a panel of cell lines, with and without anti-EGFR antibody pretreatment. Serial optical imaging of HCT116 xenograft tumors was done after systemic injection of QD and EGF-QD.

RESULTS

EGF-QD showed EGFR-specific binding in vitro. In vivo imaging showed three distinct phases, tumor influx ( approximately 3 min), clearance ( approximately 60 min), and accumulation (1-6 h), of EGF-QD nanoprobes. Both QD and EGF-QD showed comparable nonspecific rapid tumor influx and clearance followed by attainment of an apparent dynamic equilibrium at approximately 60 min. Subsequently (1-6 h), whereas QD concentration gradually decreased in tumors, EGF-QDs progressively accumulated in tumors. On delayed imaging at 24 h, tumor fluorescence decreased to near-baseline levels for both QD and EGF-QD. Ex vivo whole-organ fluorescence, tissue homogenate fluorescence, and confocal microscopic analyses confirmed tumor-specific accumulation of EGF-QD at 4 h. Immunofluorescence images showed diffuse colocalization of EGF-QD fluorescence within EGFR-expressing tumor parenchyma compared with patchy perivascular sequestration of QD.

CONCLUSION

These results represent the first pharmacokinetic characterization of a robust EGFR imaging nanoprobe. The measurable contrast enhancement of tumors 4 h after systemic administration of EGF-QD and its subsequent normalization at 24 h imply that this nanoprobe may permit quantifiable and repetitive imaging of EGFR expression.

Semiconductor quantum dots and metal nanoparticles: syntheses, optical properties, and biological applications

We review the syntheses, optical properties, and biological applications of cadmium selenide (CdSe) and cadmium selenide-zinc sulfide (CdSe-ZnS) quantum dots (QDs) and gold (Au) and silver (Ag) nanoparticles (NPs). Specifically, we selected the syntheses of QDs and Au and Ag NPs in aqueous and organic phases, size- and shape-dependent photoluminescence (PL) of QDs and plasmon of metal NPs, and their bioimaging applications. The PL properties of QDs are discussed with reference to their band gap structure and various electronic transitions, relations of PL and photoactivated PL with surface defects, and blinking of single QDs. Optical properties of Ag and Au NPs are discussed with reference to their size- and shape-dependent surface plasmon bands, electron dynamics and relaxation, and surface-enhanced Raman scattering (SERS). The bioimaging applications are discussed with reference to in vitro and in vivo imaging of live cells, and in vivo imaging of cancers, tumor vasculature, and lymph nodes. Other aspects of the review are in vivo deep tissue imaging, multiphoton excitation, NIR fluorescence and SERS imaging, and toxic effects of NPs and their clearance from the body.

Real-time intraoperative assessment of the extrahepatic bile ducts in rats and pigs using invisible near-infrared fluorescent light

BACKGROUND

Currently, only x-ray fluoroscopy is available for visualization of the extrahepatic bile ducts intraoperatively. We hypothesized that with an appropriate fluorophore and imaging system, invisible near-infrared (NIR) light could be used for image-guided procedures on the extrahepatic bile ducts.

METHODS

We quantified the performance of three 800 nm NIR fluorophores, differing primarily in their degree of hydrophilicity, for real-time imaging of the extrahepatic bile ducts in rats and pigs: IR-786, indocyanine green (ICG), and the carboxylic form of IRDyetrade mark 800CW (CW800-CA). The signal-to-background ratio (SBR) of the common bile duct relative to liver and pancreas was measured as a function of the dose of contrast agent, injection site, and kinetics using an intraoperative NIR fluorescence imaging system described previously. Bile samples were examined by high performance liquid chromatography tandem mass spectrometry (HPLC/MS) to determine the chemical form of fluorophores in bile.

RESULTS

Non-sulfonated (IR-786) and di-sulfonated (ICG) NIR fluorophores had poor efficiency and kinetics of excretion into bile. Tetra-sulfonated CW800-CA, however, provided sensitive, specific, and real-time visualization of the extrahepatic bile ducts after a single low-dose given either intraportally or intravenously via systemic vein. A SBR >/=2 provided sensitive assessment of extrahepatic bile duct anatomy and function for over 30 min post-injection, including the detection of millimeter-sized, radiolucent inclusions in pigs. CW800-CA remained intact chemically after secretion into bile.

CONCLUSION

The combination of invisible NIR light and an IV injection of CW800-CA provides prolonged, real-time visualization of the extrahepatic bile duct, without ionizing radiation and without changing the look of the operative field.

Quantum dots for cancer diagnosis and therapy: biological and clinical perspectives

Quantum dots (QDs) are semiconductor nanocrystals that emit fluorescence on excitation with a light source. They have excellent optical properties, including high brightness, resistance to photobleaching and tunable wavelength. Recent developments in surface modification of QDs enable their potential application in cancer imaging. QDs with near-infrared emission could be applied to sentinel lymph-node mapping to aid biopsy and surgery. Conjugation of QDs with biomolecules, including peptides and antibodies, could be used to target tumors in vivo. In this review, we summarize recent progress in developing QDs for cancer diagnosis and treatment from a clinical standpoint and discuss future prospects of further improving QD technology to identify metastatic cancer cells, quantitatively measure the level of specific molecular targets and guide targeted cancer therapy by providing biodynamic markers for target inhibition.

Quantum dots in axillary lymph node mapping: biodistribution study in healthy mice

Background

Breast cancer is the first cause of cancer death among women and its incidence doubled in the last two decades. Several approaches for the treatment of these cancers have been developed. The axillary lymph node dissection (ALND) leads to numerous morbidity complications and is now advantageously replaced by the dissection and the biopsy of the sentinel lymph node. Although this approach has strong advantages, it has its own limitations which are manipulation of radioactive products and possible anaphylactic reactions to the dye. As recently proposed, these limitations could in principle be by-passed if semiconductor nanoparticles (quantum dots or QDs) were used as fluorescent contrast agents for the in vivo imaging of SLN. QDs are fluorescent nanoparticles with unique optical properties like strong resistance to photobleaching, size dependent emission wavelength, large molar extinction coefficient, and good quantum yield.

Methods

CdSe/ZnS core/shell QDs emitting around 655 nm were used in our studies. 20 μL of 1 μM (20 pmol) QDs solution were injected subcutaneously in the anterior paw of healthy nude mice and the axillary lymph node (ALN) was identified visually after injection of a blue dye. In vivo fluorescence spectroscopy was performed on ALN before the mice were sacrificed at 5, 15, 30, 60 min and 24 h after QDs injection. ALN and all other organs were removed, cryosectioned and observed in fluorescence microscopy. The organs were then chemically made soluble to extract QDs. Plasmatic, urinary and fecal fluorescence levels were measured.

Results

QDs were detected in ALN as soon as 5 min and up to 24 h after the injection. The maximum amount of QDs in the ALN was detected 60 min after the injection and corresponds to 2.42% of the injected dose. Most of the injected QDs remained at the injection site. No QDs were detected in other tissues, plasma, urine and feces.

Conclusion

Effective and rapid (few minutes) detection of sentinel lymph node using fluorescent imaging of quantum dots was demonstrated. This work was done using very low doses of injected QDs and the detection was done using a minimally invasive method.

Optical molecular imaging: from single cell to patient

Optical imaging is an emerging field with a wide range of biomedical research and clinical applications, both current and future. It comprises several classes of techniques that are capable of providing information at the molecular, cellular, tissue, and whole-animal levels. These techniques match well with emerging genomic and proteomic technologies that enable development of optical "probes," as well as with nanotechnologies for multifunctional imaging and drug delivery. These advances have enormous potential to accelerate drug discovery/development by providing predictive information on mechanisms of action and biological responses.

Intraoperative identification of sentinel lymph nodes by near-infrared fluorescence imaging in patients with breast cancer

We present a novel method for sentinel lymph node (SLN) identification by fluorescence imaging that provides a high detection rate and a low false-negativity rate. Twenty-five breast cancer patients with tumors less than 3 cm in diameter were enrolled. A combination of indocyanine green and indigo carmine was injected subdermally in the areola. Subcutaneous lymphatic channels draining from the areola to the axilla were immediately showed by fluorescence imaging. After incising the axillary skin near the point of disappearance of the fluorescence, the SLN was dissected under fluorescence guidance. In all patients, the lymphatic channels and SLN were successfully visualized. The mean number of fluorescent SLN and blue-dyed SLN were 5.5 and 2.3. Eight patients were found to have lymph node metastases pathologically. All of them were recognized by fluorescence imaging. This method is feasible and safe for intraoperative detection of SLN allowing real-time observation without any need for training.

Optical agents

Optical imaging is an emerging modality in the growing field of biomedical diagnostics. The past decade has witnessed the development of a variety of promising strategies for optical imaging techniques. Fundamental to these techniques is the design and application of novel fluorescent markers to allow molecular level in-vivo studies of disease in animal models in the laboratory and eventually in human clinical studies. This review surveys the range of fluorophores employed in these probes and the alternative probe systems in which they are used: non-specific, targeted and activatable; recent developments in the area of fluorescent nanoprobes and multimodality constructs are also reviewed.

Endoscopic imaging: emerging optical techniques for the detection of colorectal neoplasia

PURPOSE OF REVIEW

Advances in bioengineering have spawned various imaging modalities which have revolutionized endoscopy. Some of these technologies provide real-time, high-resolution, subcellular imaging. This review provides an update on these technologies and their role in the evaluation of colorectal neoplasia.

RECENT FINDINGS

Narrow band imaging has been shown to visualize capillary patterns in early cancer and is complementary to magnification endoscopy. Optical coherence tomography has been used to evaluate neoplastic progression and distinguish Crohn's from ulcerative colitis. Confocal endomicroscopy has been shown to accurately predict neoplastic changes in polyps and identify areas of neoplasia in patients with colitis. Among the spectroscopic techniques, autofluorescence is best studied in the colon and has been used to identify adenomas and dysplasia in inflammatory bowel disease. Endocytoscopy is a relatively new technology but shows promise in distinguishing neoplastic lesions.

SUMMARY

Recently a number of imaging technologies have arisen that have the potential to enhance our detection of colorectal neoplasia. Several of these, such as autofluorescent imaging and narrow band imaging, are 'red flag' techniques which enhance our visualization of mucosal change(s). Complementary technologies, such as confocal endomicroscopy and endocytoscopy, provide subcellular imaging. Combined with a 'red flag' technique, these may transform our approach to colonoscopy, allowing the real-time detection and diagnosis of neoplasia.

Sentinel lymph node mapping with type-II quantum dots

Sentinel lymph node (SLN) mapping is an important cancer surgery during which the first lymph node draining the site of a tumor is identified, resected, and analyzed for the presence or absence of malignant cells. Fluorescent semiconductor nanocrystals (quantum dots [QDs]) of the appropriate size, charge, and emission wavelength permit this surgery to be performed rapidly, with high sensitivity and under complete image guidance. We describe the materials and methods necessary for the production and characterization of type-II near-infrared fluorescent QDs, which have been optimized for SLN mapping. They contain a CdTe core, CdSe shell, and a highly anionic, oligomeric phosphine organic coating. We also describe how to utilize such QDs in animal model systems of SLN mapping.

[Molecular and parametric imaging with iron oxides]

Superparamagnetic iron oxide (SPIO) contrast agents, clinically established for high resolution magnetic resonance imaging of reticuloendothelial system containing anatomical structures, can additionally be exploited for the non-invasive characterization and quantification of pathology down to the molecular level. In this context, SPIOs can be applied for non-invasive cell tracking, quantification of tissue perfusion and target specific imaging, as well as for the detection of gene expression. This article provides an overview of new applications for clinically approved iron oxides as well of new, modified SPIO contrast agents for parametric and molecular imaging.

Whole-body optical imaging in animal models to assess cancer development and progression

Different optical-based imaging models were used to investigate tumor progression and metastasis with particular emphasis on metastasis to bone and bone marrow. We describe how optical imaging can be used to follow important processes in tumor development and treatment response, including angiogenesis, apoptosis, and proteolysis. Finally, we discuss the translation of one optical imaging modality, near-IR fluorescence, from animal validation studies to applications in the clinic related to cancer management.

Use of fluorescent quantum dot bioconjugates for cellular imaging of immune cells, cell organelle labeling, and nanomedicine: surface modification regulates biological function, including cytotoxicity

With the development of nanotechnology, nanoscale products that are smaller than several hundred nanometers have been applied to all areas of science and technology. Nanoscale products, including carbon nanotubes, fullerene derivatives, and nanocrystal quantum dots (QDs), are wide spread as novel tools in various fields, not only in materials engineering, electronics, plastics, and the automobile and aerospace industries, but also in molecular biology and medicine. At present, QDs have been widely used in biological and medical studies because of their superior photoemission and photostability. Although the physical and chemical properties of QDs have been circumstantially investigated, little is known about any harmful effects of QDs on human health. Here we report on the toxicity and biological behavior of QDs in vitro and in vivo. The toxicity of the core constituent chemicals such as cadmium and selenium has been identified. Recently, the surface molecules surrounding QDs have been intensively investigated. Accumulating evidence that toxic surface-covering molecules showed their cytotoxicity and biomolecules conjugated with QDs maintained their biological effects indicates that at least the biological properties of QDs are attributable to the QD-capping material rather than to the core metalloid complex itself.