FDA-approved Dye Research Articles

Superconducting nanowire single-photon detector enhanced near-infrared II portable confocal microscopy for tissue imaging with indocyanine green

In this Letter a novel, to our knowledge, approach for near-infrared (NIR) fluorescence portable confocal microscopy is introduced, aiming to enhance fluorescence imaging of biological samples in the NIR-II window. By integrating a superconducting nanowire single-photon detector (SNSPD) into a confocal microscopy, we have significantly leveraged the detection efficiency of the NIR-II fluorescence signal from indocyanine green (ICG), an FDA-approved dye known for its NIR-II fluorescence capabilities. The SNSPD, characterized by its extremely low dark count rate and optimized NIR system detection efficiency, enables the excitation of ICG with 1 mW and the capture of low-light fluorescence signals from deep regions (up to 512 µm). Consequently, our technique was able to produce high-resolution images of bio samples with a superior signal-to-noise ratio, making a substantial advancement in the field of fluorescence microscopy and offering a promising opportunity for future clinical study.

Using kraft lignin nanoparticles for the stabilization of nano/micro wax carriers

Due to its amphiphilic structure, lignin has the potential to stabilize emulsions via adsorption at the oil/water interface. By converting lignin into nanoparticles, we can significantly enhance its emulsion-stabilizing capabilities through a Pickering-type stabilization mechanism. Two essential elements may be modified to fine-tune emulsion stability: the size of the lignin nanoparticles (LNPs) and the physicochemical nature of the lipid phase. In this context, we highlight the behavior and utility of unmodified LNPs in the preparation of Pickering emulsions made up of water and a complex bio-based pharmaceutical-grade wax that can be used for the formulation of lipid carriers. As a proof-of-concept, we employ the developed Pickering emulsions to encapsulate indocyanine green (ICG), an FDA-approved dye commonly used in medical imaging applications. We demonstrate that ultra-small LNPs are well-suited for the colloidal stabilization of pharmaceutical wax ester micro beads. This stabilization does not require any lignin modification. Additionally, we present evidence that our new lipid/lignin hybrid carrier has potential as a new drug delivery system.

Enhancing Tumor Immunotherapy by Multivalent Anti-PD-L1 Nanobody Assembled via Ferritin Nanocage.

Increasing immunotherapy response rate and durability can lead to significant improvements in cancer care. To address this challenge, a novel multivalent immune checkpoint therapeutic platform is constructed through site-specific ligation of anti-PD-L1 nanobody (Nb) on ferritin (Ftn) nanocage. Nb-Ftn blocks PD-1/PD-L1 interaction and downregulates PD-L1 levels via endocytosis-induced degradation. In addition, the cage structure of Ftn allows encapsulation of indocyanine green (ICG), an FDA-approved dye. Photothermal treatment with Nb-Ftn@ICG induces immunogenic death of tumor cells, which improves systemic immune response via maturation of dendritic cells and enhanced infiltration of T cells. Moreover, Nb-Ftn encapsulation significantly enhances cellular uptake, tumor accumulation and retention of ICG. In vivo assays showed that this nanoplatform ablates the primary tumor, suppresses abscopal tumors and inhibits tumor metastasis, leading to a prolonged survival rate. This work presents a novel strategy for improving cancer immunotherapy using multivalent nanobody-ferritin conjugates as immunological targeting and enhancing carriers.

Rapid screening of dyes for self-aggregation, adsorption and metabolic integrity – Quantitative metrics as a prelude to biological studies

The traditional development of dyes for biological applications typically begins with synthesis, is followed by spectroscopic/photophysical characterization, and culminates in testing with cultured cells or in animals. The present work describes a set of facile, low-technology, invitro, largely quantitative absorption spectrophotometric assays in aqueous solution as a prelude to biological studies. The assays include the following: (1) Self-aggregation in phosphate-buffered saline (PBS), with or without the presence of 3 % bovine serum albumin (BSA), via reciprocal change in concentration and pathlength; (2) Adsorption to solid materials as biomolecular surrogates, including cellulose, chitosan, polyethylene (PE), styrene-divinylbenzene beads (XAD-4), polyacrylic beads (XAD-7), anion exchange beads (IRA-67), cation exchange beads (CG-50), polytetrafluoroethylene (PTFE) membranes, and Nylon membranes; (3) Hydrophilicity/hydrophobicity assessment, by measurement (not calculation) of logP values; and (4) Metabolic integrity, by exposure to a rat liver homogenate. Twenty-two dyes were examined in the assays. The dyes represent diverse classes (acridine, anthraquinone, azo, benzimidazole, coumarin, cyanine, flavonoid, naphthalene, phthalocyanine, polyene, tetrapyrrole, triarylmethine, xanthene), polarity (anionic, cationic, nonionic, hydrophobic, amphipathic), and absorption (ultraviolet, visible, near-infrared). As one example, indocyanine green (ICG), an FDA-approved dye for invivo use, (i) aggregates at the concentration of 5 μM but disaggregates in the presence of BSA; (ii) in PBS is very adsorptive (>80 % binding) to various materials (cellulose, chitosan, PE, IRA-67, CG-50, PTFE, Nylon) and quite adsorptive (50–80 % binding) to XAD-4 and XAD-7, (iii) exhibits only marginal preference for water versus 1-octanol (1.5:1), and (iv) is largely digested by rat liver homogenate. A single dye can be examined in the span of one day. The quantitative metrics should prove valuable for establishing biologically relevant features of diverse dyes by simple studies in aqueous solution.

Multispectral confocal endomicroscopy in lung biopsy guidance

There is a critical need for a technology that can assist doctors in more accurately evaluating lung nodules at the time of biopsy. To address this need, a multispectral fluorescence line-scan confocal endomicroscope was developed that employs a fiber bundle probe to image tissue at the distal tip of the biopsy introducer needle. The multispectral nature of the instrument allows the simultaneous use of multiple FDA-approved dyes that stain different cellular/tissue compartments in different spectral regions to distinguish between lung cancer and benign conditions of the lung. The imaging system has been used to image normal rat lung as well as ex vivo human core-biopsy lung tissue.

Confocal laser endomicroscope with distal MEMS scanner for real-time histopathology

Confocal laser endomicroscopy is an emerging methodology to perform real time optical biopsy. Fluorescence images with histology-like quality can be collected instantaneously from the epithelium of hollow organs. Currently, scanning is performed at the proximal end of probe-based instruments used routinely in the clinic, and flexibility to control the focus is limited. We demonstrate use of a parametric resonance scanner packaged in the distal end of the endomicroscope to perform high speed lateral deflections. An aperture was etched in the center of the reflector to fold the optical path. This design reduced the dimensions of the instrument to 2.4 mm diameter and 10 mm length, allowing for forward passage through the working channel of a standard medical endoscope. A compact lens assembly provides lateral and axial resolution of 1.1 and 13.6 μm, respectively. A working distance of 0 μm and field-of-view of 250 μm × 250 μm was achieved at frame rates up to 20 Hz. Excitation at 488 nm was delivered to excite fluorescein, an FDA-approved dye, to generate high tissue contrast. The endomicroscope was reprocessed using a clinically-approved sterilization method for 18 cycles without failure. Fluorescence images were collected during routine colonoscopy from normal colonic mucosa, tubular adenomas, hyperplastic polyps, ulcerative colitis, and Crohn’s colitis. Individual cells, including colonocytes, goblet cells, and inflammatory cells, could be identified. Mucosal features, such as crypt structures, crypt lumens, and lamina propria, could be distinguished. This instrument has potential to be used as an accessory during routine medical endoscopy.

Dual-Wavelength Photoacoustic Computed Tomography with Piezoelectric Ring-Array Transducer for Imaging of Indocyanine Green Liposomes Aggregation in Tumors.

Recently, indocyanine green (ICG), as an FDA-approved dye, has been widely used for phototherapy. It is essential to obtain information on the migration and aggregation of ICG in deep tissues. However, existing fluorescence imaging platforms are not able to obtain the structural information of the tissues. Here, we prepared ICG liposomes (ICG-Lips) and built a dual-wavelength photoacoustic computed tomography (PACT) system with piezoelectric ring-array transducer to image the aggregation of ICG-Lips in tumors to guide phototherapy. Visible 780 nm light excited the photoacoustic (PA) effects of the ICG-Lips and near-infrared 1064 nm light provided the imaging of the surrounding tissues. The aggregation of ICG-Lips within the tumor and the surrounding tissues was visualized by PACT in real time. This work indicates that PACT with piezoelectric ring-array transducer has great potential in the real-time monitoring of in vivo drug distribution.

An antigen-strengthened dye-modified fully-human-nanobody-based immunoprobe for second near infrared bioimaging of metastatic tumors

Conventional immunoprobes have absorption capabilities across the visible to near infrared (NIR-I, 650–900 nm) region. Recently, second near infrared (NIR-II, 1000–1700 nm) window have gained much attention due to their deeper penetration depth and improved visualization. Here, we describe the design and synthesis of a fully human nanobody-based fluorescent immunoprobe (ICGM-n501) for NIR-II bioimaging with strengthened fluorescent emission by antigen for the first time. By site-directed conjugation of an FDA-approved dye analogue, indocyanine green decorated with maleimide (ICGM), into a tumor-specific n501, ICGM-n501 provides real-time monitoring of abdominal transportation pathway of antibody-based bioagents with high resolution (0.21 mm), presents better accuracy and lower dosage (0.21 μmol kg−1) in bioimaging of peritoneal metastatic tumors than bioluminescence agent D-luciferin. In this work, ICGM-n501 demonstrates its potential in clinical surgery guidance, provide an expanded category of available NIR-II fluorophores and a template for next-generation immunoassay bioagents.

Vehicle-Free Nanotheranostic Self-Assembled from Clinically Approved Dyes for Cancer Fluorescence Imaging and Photothermal/Photodynamic Combinational Therapy.

Phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT) has attracted growing attention as a noninvasive option for cancer treatment. At present, researchers have developed various “all-in-one” nanoplatforms for cancer imaging and PTT/PDT combinational therapy. However, the complex structure, tedious preparation procedures, overuse of extra carriers and severe side effects hinder their biomedical applications. In this work, we reported a nanoplatform (designated as ICG-MB) self-assembly from two different FDA-approved dyes of indocyanine green (ICG) and methylene blue (MB) without any additional excipients for cancer fluorescence imaging and combinational PTT/PDT. ICG-MB was found to exhibit good dispersion in the aqueous phase and improve the photostability and cellular uptake of free ICG and MB, thus exhibiting enhanced photothermal conversion and singlet oxygen (1O2) generation abilities to robustly ablate cancer cells under 808 nm and 670 nm laser irradiation. After intravenous injection, ICG-MB effectively accumulated at tumor sites with a near-infrared (NIR) fluorescence signal, which helped to delineate the targeted area for NIR laser-triggered phototoxicity. As a consequence, ICG-MB displayed a combinational PTT/PDT effect to potently inhibit tumor growth without causing any system toxicities in vivo. In conclusion, this minimalist, effective and biocompatible nanotheranostic would provide a promising candidate for cancer phototherapy based on current available dyes in clinic.

2-((E)-2-((E)-4-Chloro-5-(2-((E)-5-methoxy-3,3-dimethyl-1-(3-phenylpropyl)indolin-2-ylidene) ethylidene)-1,1-dimethyl-1,2,5,6-tetrahydropyridin-1-ium-3-yl)vinyl)-5-methoxy-3,3-dimethyl-1-(3-phenylpropyl)-3H-indol-1-ium

A heptamethine fluorophore, ERB-60, has been synthesized efficiently in four steps in a good yield. The structure of this fluorophore consists of an electron-donating group (methoxy), a hydrophobic moiety (phenylpropyl) with a rotatable bond, a quaternary ammonium fragment, and indolium rings at the terminal ends connected via polymethine chain. All these inherent chemical features fine-tuned the optical properties of the fluorophore. This compound was characterized by both 1H NMR, 13C NMR and mass spectra. The optical properties, including molar absorptivity, fluorescence, Stokes’s shift, and quantum yield, were measured in different solvents such as DMSO, DMF, MeCN, i-PrOH, MeOH, and H2O. The wavelengths of maximum absorbance of ERB-60 were found to be in the range of 745–770 nm based on the solvents used. In decreasing order, the maximum wavelength of absorbance of ERB-60 in the tested solvents was DMSO > DMF > i-PrOH > MeOH > MeCN > H2O while the decreasing order of the extinction coefficient was found to be MeCN > MeOH > DMSO > i-PrOH > H2O > DMF. ERB-60 was found to be more photostable than IR-786 iodide, a commercially available dye, and brighter than the FDA-approved dye, indocyanine green (ICG).

Multi-wavelength fluorescence imaging with a da Vinci Firefly\u2014a technical look behind the scenes

The field of fluorescence-guided surgery builds on colored fluorescent tracers that have become available for different clinical applications. Combined use of complementary fluorescent emissions can allow visualization of different anatomical structures (e.g. tumor, lymphatics and nerves) in the same patient. With the aim to assess the requirements for multi-color fluorescence guidance under in vivo conditions, we thoroughly characterized two FDA-approved laparoscopic Firefly camera systems available on the da Vinci Si or da Vinci Xi surgical robot. In this process, we studied the cameras’ performance with respect to the photophysical properties of the FDA-approved dyes Fluorescein and ICG. Our findings indicate that multi-wavelength fluorescence imaging of Fluorescein and ICG is possible using clinical-grade fluorescence laparoscopes, but critical factors for success include the photophysical dye properties, imaging system performance and the amount of accumulated dye. When comparing the camera performance, the Xi system provided more effective excitation (adaptions in the light source) and higher detection sensitivity (chip-on-a-tip and/or enhanced image processing) for both Fluorescein and ICG. Both systems can readily be used for multi-wavelength fluorescence imaging of Fluorescein and ICG under clinically relevant conditions. With that, another step has been made towards the routine implementation of multi-wavelength image-guided surgery concepts.

Characterization of single channel liquid light guide coupling and SPAD array imaging for tumour margin estimation using fluorescence lifetime

Surgery remains one of the key treatment options for tumour removal, and surgeons primarily rely on eye and touch to assess the boundary between healthy and cancerous tissue with no cellular information as guidance. There is therefore a need for a device or instrument that can be used by the surgeon in real-time during the surgical procedure to ensure as many of the cancerous cells and as few of the healthy cells have been removed as possible. Fluorescence approaches have previously demonstrated significant promise in this application, but clinical take-up has been limited and much more characterization of critical parameters needed before robotic surgery can be contemplated. Here we investigate two time-correlated single-photon counting (TCSPC) fluorescence lifetime systems for the detection of phantom tumour margins derived from silica sol-gels. A simple and low-cost liquid light guide system (LLG) incorporating a single photomultiplier detection channel and translational stage was developed. This provided a useful reference for a compact single-photon avalanche diode (SPAD) array camera system for fluorescence lifetime imaging microscopy (FLIM) which permits up to ∼25 000 in-pixel timing measurements at video rates in ambient light using only low energy (∼30 pJ) diode laser pulses to minimize cell and dye degradation. Measurements of phantom margins with sol-gel doped Rhodamine 6G (R6G) of fluorescence lifetime ∼4 ns using the LLG system demonstrates that for 7 mm excitation diameter and over 5–15 mm sol-gel LLG separation the sol-gel only region could be clearly identified 1 mm after the margin position, a widely accepted minimum surgical resolution. A comparison between measurements with the LLG and SPAD FLIM system using the sub-ns fluorescence lifetime of the FDA-approved dye indocyanine green (ICG) demonstrates that the minimum workable spatial resolution and sufficient speed are only achievable with such faster lifetimes using the SPAD FLIM system.

Optical mapping of the pig heart in situ under artificial blood circulation

The emergence of optical imaging has revolutionized the investigation of cardiac electrical activity and associated disorders in various cardiac pathologies. The electrical signals of the heart and the propagation pathways are crucial for elucidating the mechanisms of various cardiac pathological conditions, including arrhythmia. The synthesis of near-infrared voltage-sensitive dyes and the voltage sensitivity of the FDA-approved dye Cardiogreen have increased the importance of optical mapping (OM) as a prospective tool in clinical practice. We aimed to develop a method for the high-spatiotemporal-resolution OM of the large animal hearts in situ using di-4-ANBDQBS and Cardiogreen under patho/physiological conditions. OM was adapted to monitor cardiac electrical behaviour in an open-chest pig heart model with physiological or artificial blood circulation. We detail the methods and display the OM data obtained using di-4-ANBDQBS and Cardiogreen. Activation time, action potential duration, repolarization time and conduction velocity maps were constructed. The technique was applied to track cardiac electrical activity during regional ischaemia and arrhythmia. Our study is the first to apply high-spatiotemporal-resolution OM in the pig heart in situ to record cardiac electrical activity qualitatively under artificial blood perfusion. The use of an FDA-approved voltage-sensitive dye and artificial blood perfusion in a swine model, which is generally accepted as a valuable pre-clinical model, demonstrates the promise of OM for clinical application.

Innovative Device for Indocianyne Green Navigational Surgery

Dynamic reality has been integrated into developing surgical techniques, with the goals of providing increased intraoperative accuracy, easier detection of critical anatomical landmarks, and better general results for the patient. Enhancement of the reality in surgical theaters using single or multi sensorial augmenters (haptic, thermic and visual) has been reported with various degrees of success. This paper presents a novel device for navigational surgery and ancillary clinical applications based on the fluorescent properties of Indocyanine Green (ICG), a safe, FDA-approved dye that emits fluorescence at higher wavelengths than endogenous proteins. The latest technological developments and the aforementioned convenient quantum behavior of ICG allow for its effective identification in tissues by means of a complementary metal-oxide semiconductor (CMOS) infrared camera. Following fundamental research on the fluorophor in different biological suspensions and at various concentrations, our team has built a device that casts a beam of excitation light at 780nm and collects emission light at 810-830nm, filtering ambient light and endogenous autofluorescence. The emission light is fluorescent and infrared, unlike visible light. It can penetrate tissues up to 1.6cm in depth, providing after digitization into conventional imaging anatomical and functional data of immense intra-operative value.

Functionalized erythrocyte-derived optical nanoparticles to target ephrin-B2 ligands.

.Over- or under-expression of erythropoietin-production human hepatocellular receptors (Eph) and their ligands are associated with various diseases. Therefore, these molecular biomarkers can potentially be used as binding targets for the delivery of therapeutic and/or imaging agents to cells characterized by such irregular expressions. We have engineered nanoparticles derived from erythrocytes and doped with the near-infrared (NIR) FDA-approved dye, indocyanine green. We refer to these nanoparticles as NIR erythrocyte-derived transducers (NETs). We functionalized the NETs with the ligand-binding domain of a particular Eph receptor, EphB1, to target the genetically modified human dermal microvascular endothelial cells (hDMVECs) with coexpression of EphB1 receptor and its ligand ephrin-B2. This cell model mimics the pathological phenotypes of lesional endothelial cells (ECs) in port wine stains (PWSs). Our quantitative fluorescence imaging results demonstrate that such functionalized NETs bind to the ephrin-B2 ligands on these hDMVECs in a dose-dependent manner that varies sigmoidally with the number density of the particles. These nanoparticles may potentially serve as agents to target PWS lesional ECs and other diseases characterized with over-expression of Eph receptors or their associated ligands to mediate phototherapy.

Optical pH measurement system using a single fluorescent dye for assessing susceptibility to dental caries.

.Sugar-rich diets and poor dental hygiene promote the formation of a biofilm (plaque) that strongly adheres to the dental enamel surface and fosters the evolution of aciduric bacteria. The acid contributes to demineralization of the exterior tooth enamel, which accelerates after the pH drops below a critical value () for extended time periods resulting in the need for restorative procedures. Preventative techniques to alert the dentist and caries-susceptible patients regarding vulnerability to dental decay require a clinical measure of plaque activity. Therefore, there is a need to evaluate the acid production capability of plaque deposits in the pits and fissures of occlusal and interproximal regions. A ratiometric fluorescence pH-sensing device has been developed using an FDA-approved dye and LED excitation. Fluorescein spectral profiles were collected using a spectrometer and analyzed with a spectral unmixing algorithm for calibration over the pH range of 4.5 to 7. An in vivo pilot study on human subjects was performed using a sucrose rinse to accelerate bacterial metabolism and to measure the time-dependent drop in pH. The optical system is relatively immune to confounding factors such as photobleaching, dye concentration, and variation in excitation intensity associated with earlier dye-based pH measurement techniques.

NIR-II fluorescence imaging using indocyanine green nanoparticles

Fluorescence imaging in the second near-infrared window (NIR-II) holds promise for real-time deep tissue imaging. In this work, we investigated the NIR-II fluorescence properties of a liposomal formulation of indocyanine green (ICG), a FDA-approved dye that was recently shown to exhibit NIR-II fluorescence. Fluorescence spectra of liposomal-ICG were collected in phosphate-buffered saline (PBS) and plasma. Imaging studies in an Intralipid® phantom were performed to determine penetration depth. In vivo imaging studies were performed to test real-time visualization of vascular structures in the hind limb and intracranial regions. Free ICG, NIR-I imaging, and cross-sectional imaging modalities (MRI and CT) were used as comparators. Fluorescence spectra demonstrated the strong NIR-II fluorescence of liposomal-ICG, similar to free ICG in plasma. In vitro studies demonstrated superior performance of liposomal-ICG over free ICG for NIR-II imaging of deep (≥4 mm) vascular mimicking structures. In vivo, NIR-II fluorescence imaging using liposomal-ICG resulted in significantly (p < 0.05) higher contrast-to-noise ratio compared to free ICG for extended periods of time, allowing visualization of hind limb and intracranial vasculature for up to 4 hours post-injection. In vivo comparisons demonstrated higher vessel conspicuity with liposomal-ICG-enhanced NIR-II imaging compared to NIR-I imaging.

Combined application of Indocyanine green (ICG) and laser lead to targeted tumor cell destruction

PurposePrecise excision of neuroblastoma is challenging, especially when tumors adhere to vital structures. Indocyanine green (ICG), an FDA-approved dye with absorption peaking at 800 nm, can absorb the near IR laser energy and release heat in the dyed tissue. We hypothesize that by injecting ICG at tumor sites followed by precise laser application, tumor cell death can be selectively targeted. MethodsOrthotopic neuroblastoma tumors were created in the adrenal gland of immunocompromised mice. Tumor, liver, kidney, and muscle tissues were chosen for ICG injection. Intervention variables included presence of tumor capsule, continuous vs. pulsed laser treatment and total energy delivered. Control groups included laser or ICG only. Tissues were stained with hematoxylin/eosin. ResultsContinuous wave laser generated excessive heat, causing damage in all tissues. When using pulsed laser treatment, liver, kidney, muscle, and intact tumor tissues showed no cell death when treated with laser alone or laser plus ICG. Tumor tissue with the capsule removed, however, showed cell death on histology. ConclusionsPulsed laser treatment combined with ICG causes targeted tumor cell death in neuroblastoma tumor without capsule. No cell death was observed when tumor capsule was present, when only laser was used, or when applied over non-tumor tissues.

Real-Time Imaging of Electrical Signals with an Infrared FDA-Approved Dye

Clinical methods used to assess the electrical activity of excitable cells are often limited by their poor spatial resolution or their invasiveness. One promising solution to this problem is to optically measure membrane potential using a voltage-sensitive dye, but thus far, none of these dyes have been available for human use. Here we report that indocyanine green (ICG), an infrared fluorescent dye with FDA approval as an intravenously administered contrast agent, is voltage-sensitive. The fluorescence of ICG can follow action potentials in artificial neurons and cultured rat neurons and cardiomyocytes. ICG also visualized electrical activity induced in living explants of rat brain. In humans, ICG labels excitable cells and is routinely visualized transdermally with high spatial resolution. As an infrared voltage-sensitive dye with a low toxicity profile that can be readily imaged in deep tissues, ICG may have significant utility for clinical and basic research applications previously intractable for potentiometric dyes.

Identification and Usage of Fluorescent Probes as Nanoparticle Contrast Agents in Detecting Cancer

As advancements in the field of nanoparticle imaging science are made, one of the first benefits will be in open and endoscopic conditions. There is considerable evidence indicating that the use of injected contrast agents can improve the detection of tumor margins and small metastases. New and innovative targeting and contrast agents including small molecules, antibodies and nanoparticles have to be developed for a broad range of tumor types such as breast, brain, pancreatic, and ovarian cancers. At present, a number of organic dye molecules have been approved for human use including (1) indocyanine green (ICG), a near-infrared fluorescent dye; (2) fluorescein, a green fluorescent dye; (3) photofrin, a mixture of fluorescent protoporphyrin oligomers approved for photodynamic therapy, and (4) 5-aminolevulinic acid (ALA), a small molecule that is preferentially taken up by tumor cells leading to biosynthesis and accumulation of protoporphyrin IX, a natural fluorophore with red fluorescence emission. On the other hand, nanoparticles have not received FDA approval for clinical imaging, as this technology needs a lot of development and lot of research is being carried out in this unexplored area. A major task is, therefore to develop biocompatible and nontoxic nanoparticle contrast agents with the potential for FDA approval and human use. Such agents need to show improved sensitivity and specificity for tumor imaging in comparison with small-molecule-dyes. In this regard, it is highly promising to develop smart or activatable nanoparticles with improved pharmacokinetic, tumor targeting and organ clearance properties, based on the use of natural, biodegradable polymers (dextran and heparin). Dextran-based particles are sensitive to pH, and can be rapidly broken down under acidic conditions. Under neutral or slightly basic conditions, on the other hand, the dextran nanoparticles are stable and are able to circulate systemically in blood for 14 to 15 hours. In contrast, self-assembled heparin nanoparticles have much shorter blood circulation half-lives (about 60-80 min). For intra-operative use, this short circulation time could be beneficial because the probes will be cleared from the body quickly, so that surgical operations and treatment can start without much delay or waiting. For near-term clinical applications, it is important that both the dextran and heparin particles are able to trap as FDA-approved dye (such as indocyanine green), leading to new class of imaging contrast agents with improved bio distribution and photo physical properties. This class of nanoparticle contrast agents could also be conjugated with tumor targeting ligands such as folate, Epidermal Growth Factor (EGF), or RGD (recognition sequence for integrins that contains Arg-Gly-Asp attachment site) for improved sensitivity and specificity in perfect cancer imaging technique agents. This review article actually highlights the new developments occurring in this area of imaging techniques in cancer research and the author himself is using the technique for developing newer fluorescent molecules for molecular imaging using nanotechnology.