A Macrophages-Enriched Head and Neck Tumor Spheroid Model to Study Foslip® Behavior in Tumor Microenvironment

Purpose

The tumor microenvironment (TME) is composed of various stromal components, including immune cells such as tumor-associated macrophages (TAMs), which play a crucial role in cancer initiation and progression. TAMs can exhibit either a tumor-suppressive M1 or a tumor-promoting M2 phenotype. First, we aimed to develop a 3D human heterotypic model consisting of head and neck squamous cell carcinoma (HNSCC) cells and different subtypes of macrophages to replicate the interactions between immune cells and cancer cells. We further investigated the behavior of Foslip®, a liposomal formulation of temoporfin, using a macrophage-enriched 3D model.

Methods

Monocytes were differentiated into M1 and M2 macrophages, which represent two distinct subtypes. Following histological and molecular characterization, these macrophages were used to establish a 3D spheroid model of HNSCC enriched with either polarized macrophages or conditioned media. Flow cytometry and fluorescence microscopy were used to assess the accumulation and distribution of Foslip®. The cytotoxic effect of Foslip®-mediated photodynamic therapy (PDT) was evaluated using flow cytometry.

Results

We developed heterotypic spheroids characterized by a mixed phenotype of evenly distributed macrophages. In this 3D co-culture model, both M1 and M2 macrophages showed significantly higher accumulation of Foslip® compared to the cancer cells. Although this differential accumulation did not drastically affect the overall PDT efficiency, spheroids generated with conditioned media exhibited a significant enhancement in photo-induced cell death, suggesting that the microenvironment could modulate the response to Foslip®-PDT.

Conclusion

3D models of HNSCC cells and macrophages provide valuable insights into the complex response of HNSCC cells to PDT using Foslip® in vitro. This model can be used to screen immunomodulatory nanomedicines targeting TAMs in solid head and neck tumors, either alone or in combination with standard therapies.

A Coculture Based, 3D Bioprinted Ovarian Tumor Model Combining Cancer Cells and Cancer Associated Fibroblasts

Ovarian cancer remains a major public health issue due to its poor prognosis. To develop more effective therapies, it is crucial to set-up reliable models that closely mimic the complexity of the ovarian tumor's microenvironment. 3D bioprinting is currently a promising approach to build heterogenous and reproducible cancer models with controlled shape and architecture. However, this technology is still poorly investigated to model ovarian tumors. In this study, a 3D bioprinted ovarian tumor model combining cancer cells (SKOV-3) and cancer associated fibroblasts (CAFs) are described. The resulting tumor models show their ability to maintain cell viability and proliferation. Cells are observed to self-assemble in heterotypic aggregates. Moreover, CAFs are observed to be recruited and to circle cancer cells reproducing an in vivo process taking place in the tumor microenvironment. Interestingly, this approach also shows its ability to rapidly generate a high number of reproducible tumor models that can be subjected to usual characterizations (cell viability and metabolic activity; histology and immunological studies; and real-time imaging). Therefore, these ovarian tumor models can be an interesting tool for high throughput drug screening applications.

Phototoxicity of temoporfin-loaded cyclodextrin nanosponges in stroma-rich three-dimensional models of head and neck cancer

Photodynamic therapy is a multistage treatment, in which cancerous and precancerous cells are destroyed by light activation of a drug (photosensitizer). For a long time, high cellular uptake of the photosensitizer was an important indication of efficient PDT, while the role of photosensitizer penetration was unexplored. Recently, we have demonstrated that nanosponges based on hypercrosslinked β-cyclodextrin polymer (β-CDp) can increase drug penetration at the cost of their cellular uptake in multicellular spheroids, paving the way for studying the impact of penetration on PDT response. In the present work, we used β-CDp nanosponges to deliver temoporfin to the depth of stroma-rich head and neck cancer multicellular spheroids and then assess PDT response. Encapsulation of temoporfin in β-CDp nanosponges resulted in increased penetration and more uniform distribution of temoporfin in spheroids, however, was also associated with a two-fold reduction of cellular uptake compared to the free drug. Nevertheless, we demonstrated that β-CDp nanosponges possess similar PDT efficiency as the free drug in stroma-rich head and neck cancer multicellular spheroids. Overall, this study suggests that β-CDp nanosponges are a strong candidate for in vivo studies as they have fewer "off-target" effects while providing a similar therapeutic response.

Antitumor Effect and Induced Immune Response Following Exposure of Hexaminolevulinate and Blue Light in Combination with Checkpoint Inhibitor in an Orthotopic Model of Rat Bladder Cancer

Previous studies have found that use of hexaminolevulinate (HAL) and blue light cystoscopy (BLC) during treatment of bladder cancer had a positive impact on overall survival after later cystectomy, indicating a potential treatment effect beyond improved diagnostic accuracy. The aim of our study was to determine whether HAL and BL mimicking clinically relevant doses in an orthotopic rat model could have therapeutic effect by inducing modulation of a tumor-specific immune response. We also assessed whether administration with a checkpoint inhibitor could potentiate any effects observed. Rats were subjected to HAL BL alone and in combination with anti-PD-L1 and assessed for anti-tumor effects and effects on immune markers. Positive anti-tumor effect was observed in 63% and 31% of rats after, respectively, 12 and 30 days after the procedure, together with a localization effect of CD3+ and CD8+ cells after 30 days. Anti-tumor effect at 30 days increases from 31% up to 38% when combined with intravesical anti-PD-L1. In conclusion, our study demonstrated treatment effects with indications of systemic immune activation at diagnostic doses of HAL and blue light. The observed treatment effect seemed to be enhanced when used in combination with intravesically administrated immune checkpoint inhibitor.

Ionizing radiations induce shared epigenomic signatures unraveling adaptive mechanisms of cancerous cell lines with or without methionine dependency

BACKGROUND

Although radiation therapy represents a core cancer treatment modality, its efficacy is hampered by radioresistance. The effect of ionizing radiations (IRs) is well known regarding their ability to induce genetic alterations; however, their impact on the epigenome landscape in cancer, notably at the CpG dinucleotide resolution, remains to be further deciphered. In addition, no evidence is available regarding the effect of IRs on the DNA methylome profile according to the methionine dependency phenotype, which represents a hallmark of metabolic adaptation in cancer.

METHODS

We used a case-control study design with a fractionated irradiation regimen on four cancerous cell lines representative of HCC (HepG2), melanoma (MeWo and MeWo-LC1, which exhibit opposed methionine dependency phenotypes), and glioblastoma (U251). We performed high-resolution genome-wide DNA methylome profiling using the MethylationEPIC BeadChip on baseline conditions, irradiated cell lines (cumulative dose of 10 Gy), and non-irradiated counterparts. We performed epigenome-wide association studies to assess the effect of IRs and methionine-dependency-oriented analysis by carrying out epigenome-wide conditional logistic regression. We looked for epigenome signatures at the locus and single-probe (CpG dinucleotide) levels and through enrichment analyses of gene ontologies (GO). The EpiMet project was registered under the ID#AAP-BMS_003_211.

RESULTS

EWASs revealed shared GO annotation pathways associated with increased methylation signatures for several biological processes in response to IRs, including blood circulation, plasma membrane-bounded cell projection organization, cell projection organization, multicellular organismal process, developmental process, and animal organ morphogenesis. Epigenome-wide conditional logistic regression analysis on the methionine dependency phenotype highlighted several epigenome signatures related to cell cycle and division and responses to IR and ultraviolet light.

CONCLUSIONS

IRs generated a variation in the methylation level of a high number of CpG probes with shared biological pathways, including those associated with cell cycle and division, responses to IRs, sustained angiogenesis, tissue invasion, and metastasis. These results provide insight on shared adaptive mechanisms of the epigenome in cancerous cell lines in response to IR. Future experiments should focus on the tryptic association between IRs, the initiation of a radioresistance phenotype, and their interaction with methionine dependency as a hallmark of metabolic adaptation in cancer.

Analysis of Fluorescence Decay Kinetics of Indocyanine Green Monomers and Aggregates in Brain Tumor Model In Vivo

Spectroscopic approach with fluorescence time resolution allows one to determine the state of a brain tumor and its microenvironment via changes in the fluorescent dye's fluorescence lifetime. Indocyanine green (ICG) is an acknowledged infra-red fluorescent dye that self-assembles into stable aggregate forms (ICG NPs). ICG NPs aggregates have a tendency to accumulate in the tumor with a maximum accumulation at 24 h after systemic administration, enabling extended intraoperative diagnostic. Fluorescence lifetime analysis of ICG and ICG NPs demonstrates different values for ICG monomers and H-aggregates, indicating promising suitability for fluorescent diagnostics of brain tumors due to their affinity to tumor cells and stability in biological tissue.

Fluorescence imaging analysis of distribution of indocyanine green in molecular and nanoform in tumor model

BACKGROUND

The efficient intraoperative identification of tumors requires the development of highly specific near-infrared (NIR) probes as contrast agents. One of the most effective dyes existing in clinic oncology is Indocyanine Green (ICG). However, ICG has a rapid excretion, thus ruling out its extended accumulation in pathological tissues therefore limiting its clinical applications. ICG colloid solution (ICG NPs) consists predominantly of J-aggregates and to a lesser extent of H-aggregates and monomers. In the present study we assessed the spectral properties of ICG nanoforms in preclinical models.

METHODS

We used optical spectroscopy and video fluorescence navigation to monitor accumulation and distribution of ICG monomers and ICG NPs in various tissues in mice with xenografted laryngopharyngeal carcinoma after intravenous drugs injection.

RESULTS

After i.v. injection, the molecular form of ICG was not retained in the tumor and its circulation cycle averaged 5 min. Alternatively, the nanoform of the drug had a different pharmacokinetics, reaching maximum accumulation 24 h after intravenous injection. Moreover, once in the circulation, we observed a progressive accumulation in the tumor of both ICG H-aggregates and ICG monomers, but not J-aggregates.

CONCLUSION

Spectral characteristics of ICG NPs indicated the presence of several fractions, namely, J- and H-aggregates along with molecular forms. These fractions had different fluorescence spectra, allowing us to track the transformation of the drug in vivo conditions. After ICG NPs administration, J-aggregates induce accumulation of monomeric forms in the tumor, enabling extended intraoperative diagnostic, and as such further studies of J-aggregates for theranostic applications in oncological surgery are of great interest.

Validation of a Three-Dimensional Head and Neck Spheroid Model to Evaluate Cameras for NIR Fluorescence-Guided Cancer Surgery

Near-infrared (NIR) fluorescence-guided surgery is an innovative technique for the real-time visualization of resection margins. The aim of this study was to develop a head and neck multicellular tumor spheroid model and to explore the possibilities offered by it for the evaluation of cameras for NIR fluorescence-guided surgery protocols. FaDu spheroids were incubated with indocyanine green (ICG) and then included in a tissue-like phantom. To assess the capability of Fluobeam® NIR camera to detect ICG in tissues, FaDu spheroids exposed to ICG were embedded in 2, 5 or 8 mm of tissue-like phantom. The fluorescence signal was significantly higher between 2, 5 and 8 mm of depth for spheroids treated with more than 5 µg/mL ICG (p < 0.05). The fluorescence intensity positively correlated with the size of spheroids (p < 0.01), while the correlation with depth in the tissue-like phantom was strongly negative (p < 0.001). This multicellular spheroid model embedded in a tissue-like phantom seems to be a simple and reproducible in vitro tumor model, allowing a comparison of NIR cameras. The ideal configuration seems to be 450 μm FaDu spheroids incubated for 24 h with 0.05 mg/mL of ICG, ensuring the best stability, toxicity, incorporation and signal intensity.

Effect of stroma on the behavior of temoporfin-loaded lipid nanovesicles inside the stroma-rich head and neck carcinoma spheroids

Background

Despite the highly expected clinical application of nanoparticles (NPs), the translation of NPs from lab to the clinic has been relatively slow. Co-culture 3D spheroids account for the 3D arrangement of tumor cells and stromal components, e.g., cancer-associated fibroblasts (CAFs) and extracellular matrix, recapitulating microenvironment of head and neck squamous cell carcinoma (HNSCC). In the present study, we investigated how the stroma-rich tumor microenvironment affects the uptake, penetration, and photodynamic efficiency of three lipid-based nanoformulations of approved in EU photosensitizer temoporfin (mTHPC): Foslip^® (mTHPC in conventional liposomes), drug-in-cyclodextrin-in-liposomes (mTHPC-DCL) and extracellular vesicles (mTHPC-EVs).

Results

Collagen expression in co-culture stroma-rich 3D HNSCC spheroids correlates with the amount of CAFs (MeWo cells) in individual spheroid. The assessment of mTHPC loading demonstrated that Foslip^®, mTHPC-DCL and mTHPC-EVs encapsulated 0.05 × 10^− 15 g, 0.07 × 10^− 15 g, and 1.3 × 10^− 15 g of mTHPC per nanovesicle, respectively. The mid-penetration depth of mTHPC NPs in spheroids was 47.8 µm (Foslip^®), 87.8 µm (mTHPC-DCL), and 49.7 µm (mTHPC-EVs), irrespective of the percentage of stromal components. The cellular uptake of Foslip^® and mTHPC-DCL was significantly higher in stroma-rich co-culture spheroids and was increasing upon the addition of serum in the culture medium. Importantly, we observed no significant difference between PDT effect in monoculture and co-culture spheroids treated with lipid-based NPs. Overall, in all types of spheroids mTHPC-EVs demonstrated outstanding total cellular uptake and PDT efficiency comparable to other NPs.

Conclusions

The stromal microenvironment strongly affects the uptake of NPs, while the penetration and PDT efficacy are less sensitive to the presence of stromal components. mTHPC-EVs outperform other lipid nanovesicles due to the extremely high loading capacity. The results of the present study enlarge our understanding of how stroma components affect the delivery of NPs into the tumors.

Advanced co-culture 3D breast cancer model for investigation of fibrosis induced by external stimuli: optimization study

Radiation-induced fibrosis (RIF) is the main late radiation toxicity in breast cancer patients. Most of the current 3D in vitro breast cancer models are composed by cancer cells only and are unable to reproduce the complex cellular homeostasis within the tumor microenvironment to study RIF mechanisms. In order to account complex cellular interactions within the tumor microenvironment, an advanced 3D spheroid model, consisting of the luminal breast cancer MCF-7 cells and MRC-5 fibroblasts, was developed. The spheroids were generated using the liquid overlay technique in culture media into 96-well plates previously coated with 1% agarose (m/v, in water). In total, 21 experimental setups were tested during the optimization of the model. The generated spheroids were characterized using fluorescence imaging, immunohistology and immunohistochemistry. The expression of ECM components was confirmed in co-culture spheroids. Using α-SMA staining, we confirmed the differentiation of healthy fibroblasts into myofibroblasts upon the co-culturing with cancer cells. The induction of fibrosis was studied in spheroids treated 24 h with 10 ng/mL TGF-β and/or 2 Gy irradiation. Overall, the developed advanced 3D stroma-rich in vitro model of breast cancer provides a possibility to study fibrosis mechanisms taking into account 3D arrangement of the complex tumor microenvironment.

ICG-induced NIR fluorescence mapping in patients with head & neck tumors after the previous radiotherapy

BACKGROUND

The distinction between tumor and healthy tissues is complicated in the areas previously subjected to radiation therapy (RT). This is related to the fact that tissues can undergo delayed and irreversible deterioration such as inflammation, vascular alteration and fibrosis. The trials related to the fluorescence -guided surgery (FSG) in Head and Neck Squamous Cell Carcinoma (HNSCC) patients, previously subjected to RT, have not yet been reported. The present study addresses for the first time the possibilities of tumor near-infrared (NIR) imaging using Indocynaine Green (ICG) in irradiated areas.

METHODS

Four patients with histologically confirmed HNSCC were included in this study. All included patients were previously treated with RT with at least 50 Gy. RT-radiation fields from original treatment fully encompassed the second tumor or recurrence. ICG was injected via cephalic vein 45 min before the images were captured using a NIR camera system Artemis. The images were also captured before ICG injection serving as background signal. The fluorescence intensity measurements were carried out using specially designed software.

RESULTS

ICG fluorescence clearly demonstrated a significant difference in fluorescence intensity between healthy and tumor tissues in 2 of 4 patients. Histology post-resection analysis confirmed a complete tumor resection with safe surgical margins. No difference between tumor and surrounding healthy tissue was detected in patients with an epidermoid carcinoma developed from sclerohypertrophic lichen.

CONCLUSIONS

In our pilot study, we clearly established the feasibility of using NIR FGS with ICG to delineate tumor and healthy tissues in irradiated areas in infiltrating lichen-free tumors.

Trials of a Fluorescent Endoscopic Video System for Diagnosis and Treatment of the Head and Neck Cancer

This article presents the results of intraoperative fluorescent diagnostics via the endoscopic system for assessing the quality of photodynamic therapy (PDT) of head and neck cancer. The diagnosis and PDT procedures were performed on the five patients with malignant neoplasms of the vocal cords, lateral surface of the tongue, and trachea and cancer of the left parotid salivary gland. Molecular form of chlorin E6 (Ce6) was intravenously administered with a 1.0–1.1 mg/kg concentration for PDT. Fluorescent diagnostics (FD) was conducted before PDT and after PDT procedures. Control of PDT efficiency was carried out by evaluating the photobleaching of the drug (photosensitizer). The method of intraoperative fluorescent imaging allows determining the exact location of the tumor and its boundaries. The assessment of photosensitizer photobleaching in real time regime allows making quick decisions during PDT procedure, which helps improving the quality of patients’ treatment. The results showed the convenience of endoscopic fluorescent video system in various nosologies of head and neck cancer. Therefore, this diagnostic approach will improve the effectiveness of cancer treatment.

NIR fluorescence-guided tumor surgery: new strategies for the use of indocyanine green

Surgery is the frontline treatment for a large number of cancers. The objective of these excisional surgeries is the complete removal of the primary tumor with sufficient safety margins. Removal of the entire tumor is essential to improve the chances of a full recovery. To help surgeons achieve this objective, near-infrared fluorescence-guided surgical techniques are of great interest. The concomitant use of fluorescence and indocyanine green (ICG) has proved effective in the identification and characterization of tumors. Moreover, ICG is authorized by the Food and Drug Administration and the European Medicines Agency and is therefore the subject of a large number of studies. ICG is one of the most commonly used fluorophores in near-infrared fluorescence-guided techniques. However, it also has some disadvantages, such as limited photostability, a moderate fluorescence quantum yield, a high plasma protein binding rate, and undesired aggregation in aqueous solution. In addition, ICG does not specifically target tumor cells. One way to exploit the capabilities of ICG while offsetting these drawbacks is to develop high-performance near-infrared nanocomplexes formulated with ICG (with high selectivity for tumors, high tumor-to-background ratios, and minimal toxicity). In this review article, we focus on recent developments in ICG complexation strategies to improve near-infrared fluorescence-guided tumor surgery. We describe targeted and nontargeted ICG nanoparticle models and ICG complexation with targeting agents.

Doxorubicin-Loaded Thermoresponsive Superparamagnetic Nanocarriers for Controlled Drug Delivery and Magnetic Hyperthermia Applications

This study reports on the development of thermoresponsive core/shell magnetic nanoparticles (MNPs) based on an iron oxide core and a thermoresponsive copolymer shell composed of 2-(2-methoxy)ethyl methacrylate (MEO₂MA) and oligo(ethylene glycol)methacrylate (OEGMA) moieties. These smart nano-objects combine the magnetic properties of the core and the drug carrier properties of the polymeric shell. Loading the anticancer drug doxorubicin (DOX) in the thermoresponsive MNPs via supramolecular interactions provides advanced features to the delivery of DOX with spatial and temporal controls. The so coated iron oxide MNPs exhibit superparamagnetic behavior with a saturation magnetization of around 30 emu g^-1. Drug release experiments confirmed that only a small amount of DOX was released at room temperature, while almost 100% drug release was achieved after 52 h at 42 °C with Fe_3-δO₄@P(MEO₂MA₆₀OEGMA₄₀), which grafted polymer chains displaying a low critical solution temperature of 41 °C. Moreover, the MNPs exhibit magnetic hyperthermia properties as shown by specific absorption rate measurements. Finally, the cytotoxicity of the core/shell MNPs toward human ovary cancer SKOV-3 cells was tested. The results showed that the polymer-capped MNPs exhibited almost no toxicity at concentrations up to 12 μg mL^-1, whereas when loaded with DOX, an increase in cytotoxicity and a decrease of SKOV-3 cell viability were observed. From these results, we conclude that these smart superparamagnetic nanocarriers with stealth properties are able to deliver drugs to tumor and are promising for applications in multimodal cancer therapy.

Current state of the nanoscale delivery systems for temoporfin-based photodynamic therapy: Advanced delivery strategies

Enthusiasm for photodynamic therapy (PDT) as a promising technique to eradicate various cancers has increased exponentially in recent decades. The majority of clinically approved photosensitizers are hydrophobic in nature, thus, the effective delivery of photosensitizers at the targeted site is the main hurdle associated with PDT. Temoporfin (mTHPC, medicinal product name: Foscan®), is one of the most potent clinically approved photosensitizers, is not an exception. Successful temoporfin-PDT requires nanoscale delivery systems for selective delivery of photosensitizer. Over the last 25 years, the number of papers on nanoplatforms developed for mTHPC delivery such as conjugates, host-guest inclusion complexes, lipid-and polymer-based nanoparticles and carbon nanotubes is burgeoning. However, none of them appeared to be "ultimate". The present review offers the description of different challenges and achievements in nanoparticle-based mTHPC delivery focusing on the synergetic combination of various nano-platforms to improve temoporfin delivery at all stages of biodistribution. Furthermore, the association of different nanoparticles in one nanoplatform might be considered as an advanced strategy allowing the combination of several treatment modalities.

mTHPC-loaded extracellular vesicles outperform liposomal and free mTHPC formulations by an increased stability, drug delivery efficiency and cytotoxic effect in tridimensional model of tumors

Efficient photodynamic therapy with meta-tetra(hydroxyphenyl)chlorine requires the application of specific nanoformulations. mTHPC liposomal formulation (Foslip®) demonstrated favorable pharmacokinetics properties. However, rapid liposomes destruction in circulation and rapid mTHPC release impedes Foslip® applications. Alternatively, mTHPC nanovectorization using extracellular vesicles (EVs) could be an attractive option. EVs are naturally secreted by the organism to play a role in intercellular communication due to the capacity to transport proteins and nucleic acids. EVs also possess a natural ability to deliver therapeutic molecules into cancer cells. The aim of the present study was to evaluate photophysical and photobiological properties of mTHPC loaded in endothelial EVs as nanocarriers. We also studied efficiency of nanovectorisation on mTHPC distribution and PDT activity in multicellular tumor spheroids (MCTSs). MCTS is a nonvascularized in vitro 3D model of cells that mimics a similar microenvironment to in vivo situation. mTHPC-EVs were characterized by means of spectroscopic techniques, flow cytometry and nanoparticle tracking analysis. Compared with Foslip®, mTHPC-EVs are stable in murine plasma. Better mTHPC accumulation and penetration (up to 100 µm) in MCTS was observed for mTHPC-EVs compared with liposomal mTHPC. These factors could explain enhanced photodynamic activity of mTHPC-EVs compared with free and liposomal mTHPC. The light dose inducing 50% of cell death with mTHPC-EVs was 4 and 2.5-times lower than that of free and liposomal mTHPC. The obtained results demonstrate that EVs should be considered as perspective nanocarriers for mTHPC-mediated PDT.

Temoporfin-in-Cyclodextrin-in-Liposome-A New Approach for Anticancer Drug Delivery: The Optimization of Composition

The main goal of this study was to use hybrid delivery system for effective transportation of temoporfin (meta-tetrakis(3-hydroxyphenyl)chlorin, mTHPC) to target tissue. We suggested to couple two independent delivery systems (liposomes and inclusion complexes) to achieve drug-in-cyclodextrin-in-liposome (DCL) nanoconstructs. We further optimized the composition of DCLs, aiming to alter in a more favorable way a distribution of temoporfin in tumor tissue. We have prepared DCLs with different compositions varying the concentration of mTHPC and the type of β-cyclodextrin (β-CD) derivatives (Hydroxypropyl-, Methyl- and Trimethyl-β-CD). DCLs were prepared by thin-hydration technique and mTHPC/β-CD complexes were added at hydration step. The size was about 135 nm with the surface charge of (−38 mV). We have demonstrated that DCLs are stable and almost all mTHPC is bound to β-CDs in the inner aqueous liposome core. Among all tested DCLs, trimethyl-β-CD-based DCL demonstrated a homogenous accumulation of mTHPC across tumor spheroid volume, thus supposing optimal mTHPC distribution.

Fluorescent Nanoparticles for the Guided Surgery of Ovarian Peritoneal Carcinomatosis

Complete surgical resection is the ideal cure for ovarian peritoneal carcinomatosis, but remains challenging. Fluorescent guided surgery can be a promising approach for precise cytoreduction when appropriate fluorophore is used. In the presence paper, we review already developed near- and short-wave infrared fluorescent nanoparticles, which are currently under investigation for peritoneal carcinomatosis fluorescence imaging. We also highlight the main ways to improve the safety of nanoparticles, for fulfilling prerequisites of clinical application.

5-Aminolevulinic Acid-Squalene Nanoassemblies for Tumor Photodetection and Therapy: In Vitro Studies

Protoporphyrin IX (PpIX) as natural photosensitizer derived from administration of 5-aminolevulinic acid (5-ALA) has found clinical use for photodiagnosis and photodynamic therapy of several cancers. However, broader use of 5-ALA in oncology is hampered by its charge and polarity that result in its reduced capacity for passing biological barriers and reaching the tumor tissue. Advanced drug delivery platforms are needed to improve the biodistribution of 5-ALA. Here, we report a new approach for the delivery of 5-ALA. Squalenoylation strategy was used to covalently conjugate 5-ALA to squalene, a natural precursor of cholesterol. 5-ALA-SQ nanoassemblies were formed by self-assembly in water. The nanoassemblies were monodisperse with average size of 70 nm, polydispersity index of 0.12, and ζ-potential of + 36 mV. They showed good stability over several weeks. The drug loading of 5-ALA was very high at 26%. In human prostate cancer cells PC3 and human glioblastoma cells U87MG, PpIX production was monitored in vitro upon the incubation with nanoassemblies. They were more efficient in generating PpIX-induced fluorescence in cancer cells compared to 5-ALA-Hex at 1.0 to 3.3 mM at short and long incubation times. Compared to 5-ALA, they showed superior fluorescence performance at 4 h which was diminished at 24 h. 5-ALA-SQ presents a novel nano-delivery platform with great potential for the systemic administration of 5-ALA.

Drug delivery to solid tumors: the predictive value of the multicellular tumor spheroid model for nanomedicine screening

The increasing number of publications on the subject shows that nanomedicine is an attractive field for investigations aiming to considerably improve anticancer chemotherapy. Based on selective tumor targeting while sparing healthy tissue, carrier-mediated drug delivery has been expected to provide significant benefits to patients. However, despite reduced systemic toxicity, most nanodrugs approved for clinical use have been less effective than previously anticipated. The gap between experimental results and clinical outcomes demonstrates the necessity to perform comprehensive drug screening by using powerful preclinical models. In this context, in vitro three-dimensional models can provide key information on drug behavior inside the tumor tissue. The multicellular tumor spheroid (MCTS) model closely mimics a small avascular tumor with the presence of proliferative cells surrounding quiescent cells and a necrotic core. Oxygen, pH and nutrient gradients are similar to those of solid tumor. Furthermore, extracellular matrix (ECM) components and stromal cells can be embedded in the most sophisticated spheroid design. All these elements together with the physicochemical properties of nanoparticles (NPs) play a key role in drug transport, and therefore, the MCTS model is appropriate to assess the ability of NP to penetrate the tumor tissue. This review presents recent developments in MCTS models for a better comprehension of the interactions between NPs and tumor components that affect tumor drug delivery. MCTS is particularly suitable for the high-throughput screening of new nanodrugs.

PAMAM G4.5-chlorin e6 dendrimeric nanoparticles for enhanced photodynamic effects

There is currently great interest in the development of efficient and specific carrier delivery platforms for systemic photodynamic therapy. Therefore, we aimed to develop covalent conjugates between the photosensitizer chlorin e6 (Ce6) and PAMAM G4.5 dendrimers. Singlet oxygen generation (SOG) efficiency and fluorescence emission were moderately affected by the covalent binding of the Ce6 to the dendrimer. Compared to free Ce6, PAMAM anchored Ce6 displays a much higher photodynamic effect, which is ascribable to better internalization in a tumor cell model. Intracellular fate and internalization pathway of our different compounds were investigated using specific inhibition conditions and confocal fluorescence microscopy. Free Ce6 was shown to enter the cells by a simple diffusion mechanism, while G4.5-Ce6-PEG internalization was dependent on the caveolae pathway, whereas G4.5-Ce6 was subjected to the clathrin-mediated endocytosis pathway. Subcellular localization of PAMAM anchored Ce6, PEGylated or not, was very similar suggesting that the nanoparticles behave similarly in the cells. As a conclusion, we have demonstrated that PEGylated G4.5 PAMAM-Ce6 dendrimers may offer effective biocompatible nanoparticles for improved photodynamic treatment in a preclinical tumor model.

Anticancer Drug Delivery: An Update on Clinically Applied Nanotherapeutics

The development of chemotherapy using conventional anticancer drugs has been hindered due to several drawbacks related to their poor water solubility and poor pharmacokinetics, leading to severe adverse side effects and multidrug resistance in patients. Nanocarriers were developed to palliate these problems by improving drug delivery, opening the era of nanomedicine in oncology. Liposomes have been by far the most used nanovectors for drug delivery, with liposomal doxorubicin receiving US FDA approval as early as 1995. Antibody drug conjugates and promising drug delivery systems based on a natural polymer, such as albumin, or a synthetic polymer, are currently undergoing advanced clinical trials or have received approval for clinical applications. However, despite attractive results being obtained in preclinical studies, many well-designed nanodrugs fell short of expectations when tested in patients, evidencing the gap between nanoparticle design and their clinical translation. The aim of this review is to evaluate the extent of nanotherapeutics used in oncology by providing an insight into the most successful concepts. The reasons that prevent nanodrugs from expanding to clinic are discussed, and the efforts that must be taken to take full advantage of the great potential of nanomedicine are highlighted.

Targeted photodynamic therapy in head and neck squamous cell carcinoma: heading into the future

The aim of this article is to give an insight into the future of photodynamic therapy (PDT) in head and neck squamous cell carcinoma (HNSCC). Through the combination of a photosensitizing agent with light and oxygen, PDT produces highly cytotoxic reactive oxygen species leading to selective tumor eradication. PDT is an attractive treatment for focal therapy of localized tumors, especially in the case of unresectable tumors. In HNSCC, over 1500 patients have been treated by PDT, and the majority of them responded quite favorably to this treatment. However, the non-negligible photosensitization of healthy tissue is a major limitation for the clinical application of PDT. Improvement in tumor selectivity is the main challenge that can be taken up by the use of a new generation of photosensitizing nanoparticles. Passive targeting, by using functionalised nanocarriers to target to overexpressed transmembrane receptors afford attractive solutions. To this day, epidermal growth factor receptor (EGFR) remains the only validated molecular target for HNSCC, and photosensitizer immunoconjugates to EGFR have been developed for the intracellular delivery of photosensitizing agents. Depending on coordinated research between biomarkers, specific ligands, and photosensitizers, similar approaches could be rapidly developed. In addition, some photosensitizers hold high fluorescence yield and therefore could emerge as theranostic agents.

A novel orthotopic bladder tumor model with predictable localization of a solitary tumor

An ideal bladder tumor model consists in an orthotopic solitary tumor with a well-defined localization and stage, as well as unaltered normal mucosa. None of the existing models covers all these requirements. We have created a new model, suitable for diagnostic and therapeutic purposes. Female Fisher rats were divided into different groups according to bladder preconditioning and tumor cell (AY27) administration. Generalized desepithelialization was obtained by an intravesical instillation of HCl, neutralized by NaOH. Localized desepithelialization of the bladder fundus was the result of application of a micro-swab, imbibed with the same chemicals. Tumor cells administration was either generalized (intravesical instillation) or focal (micro swab). No bladder perforations were observed. Generalized desquamation always produced multifocal tumors, whereas focal application of HCl/NaOH resulted in solitary tumors of the bladder fundus, irrespective of the method of tumor cell administration. Only hyperplasia could be detected at day 3. AY27 cells were covered by umbrella cells at day 5 and subepithelial AY 27 tumor nests, covered by full thickness epithelium were observed day 7.

Multimodal Mn-doped I-III-VI quantum dots for near infrared fluorescence and magnetic resonance imaging: from synthesis to in vivo application

The development of sensitive multimodal contrast agents is a key issue to provide better global, multi-scale images for diagnostic or therapeutic purposes. Here we present the synthesis of Zn-Cu-In-(S, Se)/Zn(1-x)Mn(x)S core-shell quantum dots (QDs) that can be used as markers for both near-infrared fluorescence imaging and magnetic resonance imaging (MRI). We first present the synthesis of Zn-Cu-In-(S, Se) cores coated with a thick ZnS shell doped with various proportions of Mn. Their emission wavelengths can be tuned over the NIR optical window suitable for deep tissue imaging. The incorporation of manganese ions (up to a few thousand ions per QD) confers them a paramagnetic character, as demonstrated by structural analysis and electron paramagnetic resonance spectroscopy. These QDs maintain their optical properties after transfer to water using ligand exchange. They exhibit T1-relaxivities up to 1400 mM(-1) [QD] s(-1) at 7 T and 300 K. We finally show that these QDs are suitable multimodal in vivo probes and demonstrate MRI and NIR fluorescence detection of regional lymph nodes in mice.

Factors affecting the selectivity of nanoparticle-based photoinduced damage in free and xenografted chorioallantoïc membrane model

BACKGROUND

Photodynamic therapy (PDT) is a minimally invasive treatment modality for selective destruction of tumours. Critical anatomical structures, like blood vessels in close proximity to the tumour, could be harmed during PDT.

PURPOSE

This study aims to discriminate the photoinduced response of normal and cancerous tissues to photodamage induced by liposomal formulations of meta-tetra(hydroxyphenyl)chlorin (mTHPC).

METHODS

Normal vascular and cancerous tissues were represented, respectively, by free and xenografted in vivo model of chick chorioallantoïc membrane (CAM). Eggs received an intravenous administration of plain (Foslip®) or stabilised formulations (Fospeg®). Drug release and liposome destruction were, respectively, determined by photoinduced quenching and nanoparticle tracking analysis. PDT was performed at different drug-light intervals (DLI) with further assessment of photothrombic activity, tumoritropism and photoinduced necrosis.

RESULTS

Compared to Foslip®, Fospeg® demonstrated significantly higher stability, slower drug release, better tumoricidal effect and lower damage to the normal vasculature at already 1 h DLI.

DISCUSSION

This work suggests that nanoparticle-based PDT selectivity could be optimised by analyzing the photoinduced damage of healthy and tumour tissues.

CONCLUSION

In fine, Fospeg® appeared to be the ideal candidate in clinical context due to its potential to destroy tumours and reduce vascular damage to normal tissues at short DLI.

Surface chemistry architecture of silica nanoparticles determine the efficiency of in vivo fluorescence lymph node mapping

Near-infrared (NIR) imaging of the lymphatic system offers a sensitive, versatile, and accurate lymph node mapping to locate the first, potentially metastatic, draining nodes in the operating room. Many luminescent nanoprobes have received great attention in this field, and the design of nontoxic and bright nanosystems is of crucial importance. Fluorescent NIR-emitting dye doped silica nanoparticles represent valuable platforms to fulfill these scopes, providing sufficient brightness, resistance to photobleaching, and hydrophilic nontoxic materials. Here, we synthesized these highly stable core-shell nanoparticles with a programmable surface charge positioning and determined the effect of these physicochemical properties on their in vivo behavior. In addition, we characterized their fluorescence kinetic profile in the right axillary lymph node (RALN) mapping. We found that nanoparticles with negative charges hidden by a PEG shell are more appropriate than those with external negative charges in the mapping of lymph nodes. We also demonstrated the efficient excretion of these nanostructures by the hepatobiliary route and their nontoxicity in mice up to 3 months postinjection. These results indicate the potential future development of these fluorescent nanosystems for LN mapping.

Photodynamic therapy with conventional and PEGylated liposomal formulations of mTHPC (temoporfin): comparison of treatment efficacy and distribution characteristics in vivo

A major challenge in the application of a nanoparticle-based drug delivery system for anticancer agents is the knowledge of the critical properties that influence their in vivo behavior and the therapeutic performance of the drug. The effect of a liposomal formulation, as an example of a widely-used delivery system, on all aspects of the drug delivery process, including the drug’s behavior in blood and in the tumor, has to be considered when optimizing treatment with liposomal drugs, but that is rarely done. This article presents a comparison of conventional (Foslip®) and polyethylene glycosylated (Fospeg®) liposomal formulations of temoporfin (meta-tetra[hydroxyphenyl]chlorin) in tumor-grafted mice, with a set of comparison parameters not reported before in one model. Foslip® and Fospeg® pharmacokinetics, drug release, liposome stability, tumor uptake, and intratumoral distribution are evaluated, and their influence on the efficacy of the photodynamic treatment at different light–drug intervals is discussed. The use of whole-tumor multiphoton fluorescence macroscopy imaging is reported for visualization of the in vivo intratumoral distribution of the photosensitizer. The combination of enhanced permeability and retention-based tumor accumulation, stability in the circulation, and release properties leads to a higher efficacy of the treatment with Fospeg® compared to Foslip®. A significant advantage of Fospeg® lies in a major decrease in the light–drug interval, while preserving treatment efficacy.

Aptamers as remarkable diagnostic and therapeutic agents in cancer treatment

Nucleic acid aptamers are molecules that are being used in a large number of biomedical applications. Aptamers have the properties to bind to a wide range of molecules with high specificity and affinity for their target. These properties together with their small size and their ease of synthesis make them very attractive and promising for targeting diseases and therapeutic applications. Aptamers can serve as cancer diagnostic tools by detecting specific biomarkers, circulating cancer cells or imaging diseased tissue. On the other hand, aptamers can be used as therapeutic agents due to their potential antagonist activity, or as targeting agents. Therefore, they can be designed to deliver antitumor molecules such as chemotherapeutic drugs, siRNA or photodynamic therapy sensitizers to diseased tissues. Attempts are also made to synthesize aptamers-targeted nanoplatforms capable to ferry cargo and load onto them both imaging and therapeutic functions creating so called nanotheragnostics agents. In the future, its seems likely that aptamers will play an important role in diagnosis and treatment of several pathologies including cancer.

Design of new quantum dot materials for deep tissue infrared imaging

Near infrared fluorescence offers several advantages for tissue and in vivo imaging thanks to deeper photon penetration. In this article, we review a promising class of near infrared emitting probes based on semiconductor quantum dots (QDs), which have the potential to considerably improve in vivo fluorescence imaging thanks to their high brightness and stability. We discuss in particular the different criteria to optimize the design of near infrared QDs. We present the recent developments in the synthesis of novel QD materials and their different in vivo imaging applications, including lymph node localization, vasculature imaging, tumor localization, as well as cell tracking and QD-based multimodal probes.

How to avoid local side effects of bladder photodynamic therapy: impact of the fluence rate

PURPOSE

We studied how to avoid irritative bladder symptoms after bladder photodynamic therapy, such as urgency, frequency and pain, which are associated with the inflammation and destruction of normal urothelium.

MATERIALS AND METHODS

Rats bearing orthotopic bladder tumors were instilled with hexyl-aminolevulinate and illuminated with red light at a high vs low (100 vs 15 mW/cm(2)) fluence rate. Cystectomy specimens 48 hours after treatment were subjected to anatomopathological examination. Inflammatory reaction and apoptosis were evaluated. In vivo photobleaching was assessed during illumination at each fluence rate.

RESULTS

All superficial tumors were eradicated irrespective of light dose and fluence rate. High fluence rates induced necrosis with inflammatory reaction and absent normal urothelium. Low fluence rates did not provoke inflammation and resulted in apoptotic cell death with preserved urothelial integrity. This could be attributable to faster photobleaching of the photosensitizer in normal urothelium at low fluence rates.

CONCLUSIONS

Bladder photodynamic therapy at a low fluence rate minimizes side effects without hampering therapeutic efficacy.

Visualisation of sentinel lymph node with indium-based near infrared emitting Quantum Dots in a murine metastatic breast cancer model

Due to its non-invasiveness, high temporal resolution and lower cost, fluorescence imaging is an interesting alternative to the current method (blue dye and radiocolloid) of sentinel lymph node (SLN) mapping in breast cancer. Near-infrared (NIR) emitting cadmium-based Quantum Dots (QDs) could be used for this purpose; however, their wide application is limited because of the toxicity of heavy metals composing the core. Our recent work demonstrated that indium-based QDs exhibit a weak acute local toxicity in vivo compared to their cadmium-based counterparts. In the present study we confirmed the weak toxicity of CuInS(2)/ZnS QDs in different in vitro models. Further in vivo studies in healthy mice showed that In-based QDs could be visualised in SLN in a few minutes after administration with a progressive increase in fluorescence until 8 h. The quantity of indium was assessed in selected organs and tissues by inductively coupled plasma - mass spectroscopy (ICP-MS) as a function of post-injection time. QD levels decrease rapidly at the injection point in the first hours after administration with a parallel increase in the lymph nodes and to a lesser extent in the liver and spleen. In addition, we observed that 3.5% of the injected indium dose was excreted in faeces in the first 4 days, with only trace quantities in the urine. Metastatic spread to the lymph nodes may hamper its visualisation. Therefore, we further performed non-invasive fluorescence measurement of QDs in SLN in tumour-bearing mice. Metastatic status was assessed by immunohistology and molecular techniques and revealed the utmost metastatic invasion of 36% of SLN. Fluorescence signal was the same irrespective of SLN status. Thus, near-infrared emitting cadmium-free QDs could be an excellent SLN tracer.

Interaction of liposomal formulations of meta-tetra(hydroxyphenyl)chlorin (temoporfin) with serum proteins: protein binding and liposome destruction

mTHPC is a non polar photosensitizer used in photodynamic therapy. To improve its solubility and pharmacokinetic properties, liposomes were proposed as drug carriers. Binding of liposomal mTHPC to serum proteins and stability of drug carriers in serum are of major importance for PDT efficacy; however, neither was reported before. We studied drug binding to human serum proteins using size-exclusion chromatography. Liposomes destruction in human serum was measured by nanoparticle tracking analysis (NTA). Inclusion of mTHPC into conventional (Foslip(®)) and PEGylated (Fospeg(®)) liposomes does not affect equilibrium serum protein binding compared with solvent-based mTHPC. At short incubation times the redistribution of mTHPC from Foslip(®) and Fospeg(®) proceeds by both drug release and liposomes destruction. At longer incubation times, the drug redistributes only by release. The release of mTHPC from PEGylated vesicles is delayed compared with conventional liposomes, alongside with greatly decreased liposomes destruction. Thus, for long-circulation times the pharmacokinetic behavior of Fospeg(®) could be influenced by a combination of protein- and liposome-bound drug. The study highlights the modes of interaction of photosensitizer-loaded nanovesicles in serum to predict optimal drug delivery and behavior in vivo in preclinical models, as well as the novel application of NTA to assess the destruction of liposomes.

mTHPC-based photodynamic therapy induction of autophagy and apoptosis in cultured cells in relation to mitochondria and endoplasmic reticulum stress

Photodynamic therapy (PDT), an approved anticancer treatment, is reported as a potent inducer of programmed cell death (PCD) by both apoptosis and autophagy. The present study investigated the kinetics of both autophagy and caspase activation in MCF-7 cells submitted to mTHPC-PDT upon condition of treatment promoting ER accumulation of mTHPC. Fluence-dependent immediate cytochrome c (cyt C) release followed by caspase-9 and -7 activation at 1 h post-PDT evidenced a mitochondrial oxidative stress triggered by high light doses leading to >90% of cell death. ER oxidative stress was monitored by the induction of the glucose-related protein chaperone GRP78. From 6 h post-PDT, GRP78 induction was accompanied by the conversion of LC3-I into LC3-II, the hallmark of autophagosome formation. The formation of acid vesicles evidenced by fluorescence microscopy was obvious from 22 h post-PDT. Twenty-four hours post-PDT, cyt C release decreased and caspase-9 cleavage disappeared, while the expression of cleaved caspase-7 remained significant. At the same time, the profiles of GRP78, cleaved caspase-7 and LC3-II expression were similar irrespective of light doses. In contrast to an inhibitor of caspase activation Z-VAD-FMK, the use of autophagy inhibitor, Wortmannin, impaired cytotoxicity along with an increase in caspase-7 activation. These results demonstrate a valuable contribution of autophagy to cell death in mTHPC-photosensitized MCF-7 cells.

Evaluation of combined matrix-assisted laser desorption/ionization time-of-flight and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry experiments for peptide mass fingerprinting analysis

Peptide Mass Fingerprinting (PMF) is still of significant interest in proteomics because it allows a large number of complex samples to be rapidly screened and characterized. The main part of post-translational modifications is generally preserved. In some specific cases, PMF suffers from ambiguous or unsuccessful identification. In order to improve its reliability, a combined approach using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICRMS) was evaluated. The study was carried out on bovine serum albumin (BSA) digest. The influence of several important parameters (the matrix, the sample preparation method, the amount of the analyte) on the MOWSE score and the protein sequence coverage were evaluated to allow the identification of specific effects. A careful investigation of the sequence coverage obtained by each kind of experiment ensured the detection of specific peptides for each experimental condition. Results highlighted that DHB-FTICRMS and DHB- or CHCA-TOFMS are the most suited combinations of experimental conditions to achieve PMF analysis. The association (convolution) of the data obtained by each of these techniques ensured a significant increase in the MOWSE score and the protein sequence coverage.

Compartmental targeting for mTHPC-based photodynamic treatment in vivo: Correlation of efficiency, pharmacokinetics, and regional distribution of apoptosis

PURPOSE

The present study investigates the efficacy of compartmental targeting in xenografted tumors treated by meta-tetra(hydroxyphenyl)chlorin (mTHPC)-mediated photodynamic therapy (PDT). The therapeutic efficacy was, furthermore, related to a regional photoinduced distribution of apoptosis and an mTHPC biodistribution profile.

METHODS AND MATERIALS

Mice bearing EMT6 tumors were subjected to a single irradiation (10 J/cm(2)) of red laser light (652 nm) at different intervals after a single- (0.3 mg/kg or 0.15 mg/kg) or double-intravenous (2 × 0.15 mg/kg) injection(s) of mTHPC. Efficiency of the treatment was evaluated by monitoring tumor regrowth. mTHPC pharmacokinetics were assessed by high-performance liquid chromatography analysis of excised organs. The regional distribution of apoptosis in tumor sections was investigated with a newly developed colabelling immunohistochemistry technique.

RESULTS

A fractionated double-injection protocol of mTHPC with 24-h and 3-h drug-light intervals (DLI) yielded 100% tumor cure, with tumors presenting a massive apoptosis of neoplastic cells along with a distortion of vessels. The best efficiency for a single injection (0.3 mg/kg) was about 54% tumor cure and corresponded to a DLI of 3 h. At this DLI, tumors showed apoptosis of endothelial cells in residual vessels. Concentrations of mTHPC observed in plasma and tumor for the fractionated injection were not statistically different and were less than the total drug dose in each compartment.

CONCLUSIONS

The present work suggests that clinical PDT protocols with mTHPC could be greatly improved by fractionation of the drug administration. Time points should be chosen based on the intratumoral spatiotemporal drug distribution.

Cadmium-free CuInS2/ZnS quantum dots for sentinel lymph node imaging with reduced toxicity

Semiconductor quantum dots (QDs) could significantly impact the performance of biomedical near-infrared (NIR) imaging by providing fluorescent probes that are brighter and more photostable than conventional organic dyes. However, the toxicity of the components of NIR emitting II-VI and IV-VI QDs that have been made so far (Cd, Hg, Te, Pb, etc.) has remained a major obstacle to the clinical use of QDs. Here, we present the synthesis of CuInS(2)/ZnS core/shell QDs emitting in the NIR ( approximately 800 nm) with good quantum yield and stability even after transfer into water. We demonstrate the potential of these QDs by imaging two regional lymph nodes (LNs) in vivo in mice. We then compare the inflammatory response of the axillary LN induced by different doses of CuInS(2)/ZnS and CdTeSe/CdZnS QDs and show a clear difference in acute local toxicity, the onset of inflammation only occurring at a 10 times more concentrated dose for CuInS(2)/ZnS QDs than for their Cd-containing counterparts.

Quantification techniques and biodistribution of semiconductor quantum dots

Quantum dots (QDs) are fluorescent inorganic nanocrystals with advantageous optical properties, which have been applied for biomedical purposes including imaging, diagnostic, drug delivery or therapy. Potential toxicity of QDs remains the major barrier to clinical translation, and as such the precise analysis of in vivo QDs distribution and pharmacokinetics is of major importance. Biodistribution studies in animal models are, however, sparse. The present review provides in a first lieu a summary of different techniques, which are currently used for relative quantification of QDs in vivo or their absolute quantification ex vivo. Fluorescence and radioactivity based techniques along with mass-spectrometry detection at the elementary level are addressed in this review. We further introduce biodistribution studies in animal models and discuss the possibilities to modify quantum dots biodistribution in function of different injection ways.