Multi-dye theranostic nanoparticle platform for bioimaging and cancer therapy

Alkyl Chain Appended Fe(III) Catecholate Complex as a Dual-Modal T1 MRI-NIR Fluorescence Imaging Agent via Second Sphere Water Interactions

The C₁₂-alkyl chain-conjugated Fe(III) catecholate complex [Fe(C₁₂CAT)₃]^3-, Fe(C₁₂CAT)₃ [C₁₂CAT = N-(3,4-dihydroxyphenethyl)dodecanamide], was synthesized and characterized, reported as a dual-modal T₁-MRI and an optical imaging probe. The DFT-optimized structure of Fe(C₁₂CAT)₃ reveals a distorted octahedral coordination geometry around the high spin Fe(III) center. The formation constant (-log K) of Fe(C₁₂CAT)₃ was calculated as 45.4. The complex exhibited r₁-relaxivity values of 2.31 ± 0.12 and 1.52 ± 0.06 mM^-1 s^-1 at 25 and 37 °C, respectively, on 1.41 T at pH 7.3 via second-sphere water interactions. The interaction of Fe(C₁₂CAT)₃ with human serum albumin showed concomitant enhancement of r₁-relaxivity to 6.44 ± 0.15 mM^-1 s^-1. The MR phantom images are significantly brighter and directly correlate to the concentration of Fe(C₁₂CAT)₃. Adding an external fluorescent marker IR780 dye to Fe(C₁₂CAT)₃ leads to the formation of self-assembly by C₁₂-alkyl chains. It resulted in the fluorescence quenching of the dye, and its critical aggregation concentration was calculated as 70 μM. The aggregated matrix of Fe(C₁₂CAT)₃ and IR780 dye is spherical, with an average hydrodynamic diameter of 189.5 nm. This self-assembled supramolecular system is found to be non-fluorescent and was "turn-on" under acidic pH via dissociation of aggregates. The r₁-relaxivity is found to be unchanged during the matrix aggregation and disaggregation. The probe showed MRI ON and fluorescent OFF under physiological conditions and MRI ON and fluorescent ON under acidic pH. The cell viability experiments showed that the cells are 80% viable at 1 mM probe concentration. Fluorescence experiments and MR phantom images showed that Fe(C₁₂CAT)₃ is a potential dual model imaging probe to visualize the acidic pH environment of the cells.

Towards the Use of Individual Fluorescent Nanoparticles as Ratiometric Sensors: Spectral Robustness of Ultrabright Nanoporous Silica Nanoparticles

Here we address an important roadblock that prevents the use of bright fluorescent nanoparticles as individual ratiometric sensors: the possible variation of fluorescence spectra between individual nanoparticles. Ratiometric measurements using florescent dyes have shown their utility in measuring the spatial distribution of temperature, acidity, and concentration of various ions. However, the dyes have a serious limitation in their use as sensors; namely, their fluorescent spectra can change due to interactions with the surrounding dye. Encapsulation of the d, e in a porous material can solve this issue. Recently, we demonstrated the use of ultrabright nanoporous silica nanoparticles (UNSNP) to measure temperature and acidity. The particles have at least two kinds of encapsulated dyes. Ultrahigh brightness of the particles allows measuring of the signal of interest at the single particle level. However, it raises the problem of spectral variation between particles, which is impossible to control at the nanoscale. Here, we study spectral variations between the UNSNP which have two different encapsulated dyes: rhodamine R6G and RB. The dyes can be used to measure temperature. We synthesized these particles using three different ratios of the dyes. We measured the spectra of individual nanoparticles and compared them with simulations. We observed a rather small variation of fluorescence spectra between individual UNSNP, and the spectra were in very good agreement with the results of our simulations. Thus, one can conclude that individual UNSNP can be used as effective ratiometric sensors.

Nanostructured Organosilica Nitric Oxide Donors Intrinsically Regulate Macrophage Polarization with Antitumor Effect

Nitric oxide (NO) has many important biological functions; however, it has been a long-standing challenge to utilize the exogenous NO donor itself in the activation of macrophages for cancer immunotherapy. Herein, we report the synthesis of a nanoparticle-based NO delivery platform with a rational design for effective NO delivery and macrophage activation. S-Nitrosothiol (SNO) modified organosilica nanoparticles with a tetrasulfide-containing composition produced a higher level of intracellular NO than their bare silica counterparts in macrophages. Enhanced intracellular delivery of NO resulted in mitochondrial dysfunction and disruption of the tricarboxylic acid cycle, leading to macrophage activation and delayed tumor growth. This study provides insights on intracellularly delivered NO for regulating the polarization of macrophages and cancer immunotherapy.

Mesoporous Silica Nanoparticle-Based Imaging Agents for Hepatocellular Carcinoma Detection

Hepatocellular carcinoma (HCC) is characterized by poor prognosis and high mortality. The treatment of HCC is closely related to the stage, and the early-stage of HCC patients usually accompanies a more long-term survival rate after clinical treatment. Hence, there are critical needs to develop effective imaging agents with superior diagnostic precision for HCC detection at an early stage. Recently, mesoporous silica nanoparticles (MSNs) based imaging agents have gained extensive attentions in HCC detection, which can serve as a multifunctional nanoplatform with controllable size and facile surface functionalization. This perspective summarizes recent advances in MSNs based imaging agents for HCC detection by the incorporation of several clinical imaging modalities. Multi-modal imaging system has been developed for higher spatial resolution and sensitivity. Even though some limitations and challenges need to be overcome, we envision the development of novel MSNs based imaging agents will offer great potential applications in clinical HCC detection.

Harvesting Light To Produce Heat: Photothermal Nanoparticles for Technological Applications and Biomedical Devices

The photothermal properties of nanoparticles (NPs), that is, their ability to convert absorbed light into heat, have been studied since the end of the last century, mainly on gold NPs. In the new millennium, these studies have developed into a burst of research dedicated to the photothermal ablation of tumors. However, beside this strictly medical theme, research has also flourished in the connected areas of photothermal antibacterial surface coatings, gels and polymers, of photothermal surfaces for cell stimulation, as well as in purely technological areas that do not involve medical biotechnology. These include the direct conversion of solar light into heat, a more efficient sun-powered generation of steam and the use of inkjet-printed patterns of photothermal NPs for anticounterfeit printing based on temperature reading, to cite but a few. After an analysis of the photothermal effect (PTE) and its mechanism, this minireview briefly considers the antitumor-therapy theme and takes an in-depth look at all the other technological and biomedical applications of the PTE, paying particular attention to photothermal materials whose NPs have joined those based on Au.

Sequence-Defined Nanotubes Assembled from IR780-Conjugated Peptoids for Chemophototherapy of Malignant Glioma

Near-infrared (NIR) laser-induced phototherapy through NIR agents has demonstrated the great potential for cancer therapy. However, insufficient tumor killing due to the nonuniform heat or cytotoxic singlet oxygen (1O2) distribution over tumors from phototherapy results in tumor recurrence and inferior outcomes. To achieve high tumor killing efficacy, one of the solutions is to employ the combinational treatment of phototherapy with other modalities, especially with chemotherapeutic agents. In this paper, a simple and effective multimodal therapeutic system was designed via combining chemotherapy, photothermal therapy (PTT), and photodynamic therapy (PDT) to achieve the polytherapy of malignant glioma which is one of the most aggressive tumors in the brain. IR-780 (IR780) dye-labeled tube-forming peptoids (PepIR) were synthesized and self-assembled into crystalline nanotubes (PepIR nanotubes). These PepIR nanotubes showed an excellent efficacy for PDT/PTT because the IR780 photosensitizers were effectively packed and separated from each other within crystalline nanotubes by tuning IR780 density; thus, a self-quenching of these IR780 molecules was significantly reduced. Moreover, the efficient DOX loading achieved due to the nanotube large surface area contributed to an efficient and synergistic chemotherapy against glioma cells. Given the unique properties of peptoids and peptoid nanotubes, we believe that the developed multimodal DOX-loaded PepIR nanotubes in this work offer great promises for future glioma therapy in clinic.

Application of phototherapeutic-based nanoparticles in colorectal cancer

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second leading cause of cancer death, which accounts for approximately 10% of all new cancer cases worldwide. Surgery is the main method for treatment of early-stage CRC. However, it is not effective for most metastatic tumors, and new treatment and diagnosis strategies need to be developed. Photosensitizers (PSs) play an important role in the treatment of CRC. Phototherapy also has a broad prospect in the treatment of CRC because of its low invasiveness and low toxicity. However, most PSs are associated with limitations including poor solubility, poor selectivity and high toxicity. The application of nanomaterials in PSs has added many advantages, including increased solubility, bioavailability, targeting, stability and low toxicity. In this review, based on phototherapy, we discuss the characteristics and development progress of PSs, the targeting of PSs at organ, cell and molecular levels, and the current methods of optimizing PSs, especially the application of nanoparticles as carriers in CRC. We introduce the photosensitizer (PS) targeting process in photodynamic therapy (PDT), the damage mechanism of PDT, and the application of classic PS in CRC. The action process and damage mechanism of photothermal therapy (PTT) and the types of ablation agents. In addition, we present the imaging examination and the application of PDT / PTT in tumor, including (fluorescence imaging, photoacoustic imaging, nuclear magnetic resonance imaging, nuclear imaging) to provide the basis for the early diagnosis of CRC. Notably, single phototherapy has several limitations in vivo, especially for deep tumors. Here, we discuss the advantages of the combination therapy of PDT and PTT compared with the single therapy. At the same time, this review summarizes the clinical application of PS in CRC. Although a variety of nanomaterials are in the research and development stage, few of them are actually on the market, they will show great advantages in the treatment of CRC in the near future.

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

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

Importance of Theranostics in Rare Brain-Eating Amoebae Infections

Pathogenic free-living amoebae including Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri cause infections of the central nervous system (CNS), which almost always prove fatal. The mortality rate is high with the CNS infections caused by these microbes despite modern developments in healthcare and antimicrobial chemotherapy. The low awareness, delayed diagnosis, and lack of effective drugs are major hurdles to overcome these challenges. Nanomaterials have emerged as vital tools for concurrent diagnosis and therapy, which are commonly referred to as theranostics. Nanomaterials offer highly sensitive diagnostic systems and viable therapeutic effects as a single modality. There has been good progress to develop nanomaterials based efficient theranostic systems against numerous kinds of tumors, but this field is yet immature in the context of infectious diseases, particularly parasitic infections. Herein, we describe the potential value of theranostic applications of nanomaterials against brain infections due to pathogenic amoebae.

Photothermal and photodynamic activity of polymeric nanoparticles based on α-tocopheryl succinate-RAFT block copolymers conjugated to IR-780

The aim of this work was the generation of a multifunctional nanopolymeric system that incorporates IR-780 dye, a near-infrared (NIR) imaging probe that exhibits photothermal and photodynamic properties; and a derivate of α-tocopheryl succinate (α-TOS), a mitochondria-targeted anticancer compound. IR-780 was conjugated to the hydrophilic segment of copolymer PEG-b-polyMTOS, based on poly(ethylene glycol) (PEG) and a methacrylic derivative of α-tocopheryl succinate (MTOS), to generate IR-NP, self-assembled nanoparticles (NPs) in aqueous media which exhibit a hydrophilic shell and a hydrophobic core. During assembly, the hydrophobic core of IR-NP could encapsulate additional IR-780 to generate derived subspecies carrying different amount of probe (IR-NP-eIR). Evaluation of photo-inducible properties of IR-NP and IR-NP-eIR were thoroughly assessed in vitro. Developed nanotheranostic particles showed distinct fluorescence and photothermal behavior after excitation by a laser light emitting at 808nm. Treatment of MDA-MB-453 cells with IR-NP or IR-NP-eIR resulted in an efficient internalization of the IR-780 dye, while subsequent NIR-laser irradiation led to a severe decrease in cell viability. Photocytoxicity conducted by IR-NP, which could not be attributed to the generation of lethal hyperthermia, responded to an increase in the levels of intracellular reactive oxygen species (ROS). Therefore, the fluorescence imaging and inducible phototoxicity capabilities of NPs derived from IR-780-PEG-b-polyMTOS copolymer confer high value to these nanotheranostics tools in clinical cancer research.

STATEMENT OF SIGNIFICANCE

Multifunctional polymeric nanoparticles (NPs) that combine imaging and therapeutic properties are highly valuable in cancer treatment. In this paper we describe the development of NPs that are fluorescent in the near-infrared (NIR). This is important for their visualization in living tissues that present low absorption and low autofluorescence in this wavelength region (between 700 and 1000nm). Moreover, NPs present photothermal and photodynamic properties when NIR irradiated: the NPs produce an efficient increment of temperature and increase the intracellular reactive oxygen species (ROS) when laser irradiated at 808nm. These tuneable photoinduced properties make the NPs highly cytotoxic after NIR irradiation and provide a new tool for highly precise cancer treatment.

Exceptionally High Payload of the IR780 Iodide on Folic Acid-Functionalized Graphene Quantum Dots for Targeted Photothermal Therapy

The IR780 iodide (IR780) is recognized as an effective theranostic agent for simultaneous near-infrared fluorescence imaging and photothermal therapy (PTT). However, the rigid chloro-cyclohexenyl ring makes IR780 insoluble in almost all pharmaceutically acceptable solvents, which inevitably limits its clinical application. We report folic acid (FA)-functionalized graphene quantum dots (GQDs-FA) containing a large and intact sp² domain with carboxyl groups around the edge. Such GQDs-FA possess exceptionally high loading capacity for IR780 via strong π-π stacking interactions, and the water solubility of IR780 is improved by over 2400-fold after loading onto GQDs-FA (IR780/GQDs-FA). IR780/GQDs-FA with an improved photostability, an enhanced tumor-targeting ability, and a high photothermal conversion efficiency of 87.9% were capable of producing sufficient hyperthermia to effectively kill cancer cells and completely eradicate tumors upon 808 nm laser irradiation. The present IR780/GQDs-FA may open up great opportunities for the effective PTT to treat cancer.

NIRF Heptamethine Cyanine Dye Nanocomplexes for Multi Modal Theranosis of Tumors

Heptamethine cyanine dyes are categorized as a class of near infrared fluorescent (NIRF) dyes which have been discovered to have tumor targeting and accumulation capability. This unique feature of NIRF dye makes it a promising candidate for imaging, targeted therapy and also as a drug delivery vehicle for various types of cancers. The favored uptake of dyes only in cancer cells is facilitated by several factors which include organic anion-transporting polypeptides, high mitochondrial membrane potential and tumor hypoxia in cancer cells. Currently nanotechnology has opened possibilities for multimodal or multifunctional strategies for cancer treatment. Including heptamethine cyanine dyes in nanoparticle based delivery systems have generally improved its theranostic ability by several fold owing to the multiple functionalities and structural features of heptamethine dyes. For this reason, nanocomplexes with NIRF heptamethine cyanine dye probe are preferred over non-targeting dyes such as indo cyanine green (ICG). This review sums up current trends and progress in NIRF heptamethine cyanine dye, including dye properties, multifunctional imaging and therapeutic applications in cancer.

Hydrophobic IR-780 Dye Encapsulated in cRGD-Conjugated Solid Lipid Nanoparticles for NIR Imaging-Guided Photothermal Therapy

This is high demand to enhance the accumulation of near-infrared theranostic agents in the tumor region, which is favorable to the effective phototherapy. Compared with indocyanine green (a clinically applied dye), IR-780 iodide possesses higher and more stable fluorescence intensity and can be utilized as an imaging-guided PTT agent with laser irradiation. However, lipophilicity and short circulation time limit its applications in cancer imaging and therapy. Moreover, solid lipid nanoparticles (SLNs) conjugated with c(RGDyK) was designed as efficient carriers to improve the targeted delivery of IR-780 to the tumors. The multifunctional cRGD-IR-780 SLNs exhibited a desirable monodispersity, preferable stability and significant targeting to cell lines overexpressing α_vβ₃ integrin. Additionally, the in vitro assays such as cell viability and in vivo PTT treatment denoted that U87MG cells or U87MG transplantation tumors could be eradicated by applying cRGD-IR-780 SLNs under laser irradiation. Therefore, the resultant cRGD-IR-780 SLNs may serve as a promising NIR imaging-guided targeting PTT agent for cancer therapy.

In vitro and in vivo targeting imaging of pancreatic cancer using a Fe3O4@SiO2 nanoprobe modified with anti-mesothelin antibody

Pancreatic cancer is a highly malignant disease with a 5-year survival rate <5% mainly due to lack of early diagnosis and effective therapy. In an effort to improve the early diagnostic rate of pancreatic cancer, a nanoprobe Fe₃O₄@SiO₂ modified with anti-mesothelin antibody (A-MFS) was prepared to target cells and tumor tissues highly expressing mesothelin in vitro (human pancreatic cancer cell line SW1990) and in vivo (subcutaneously transplanted tumors) studies. The A-MFS probe was successfully prepared and was spherical and uniform with a hydrodynamic diameter between 110 and 130 nm. Cell Counting Kit-8 testing indicated that A-MFS was nontoxic in vitro and in vivo studies. The in vitro study showed that the A-MFS probe specifically targeted SW1990 cells with high mesothelin expression. The in vivo study was conducted in Siemens 3.0 T magnetic resonance imaging. The average T2-weighted signal values of the xenografts were 966.533±31.56 before injecting A-MFS and 691.133±56.84 before injecting saline solution. After injection of 0.1 mL A-MFS via nude mouse caudal vein for 2.5 hours, the average T2-weighted signal of the xenograft decreased by 342.533±42.6. The signal value decreased by −61.233±33.9 and −58.7±19.4 after injection of the saline and Fe₃O₄@SiO₂. The decrease of tumor signal by A-MFS was much more significant than that by saline and Fe₃O₄@SiO₂ (P<0.05). The results demonstrated the high stability and nontoxicity of A-MFS, which effectively targeted pancreatic cancer in vitro and in vivo. A-MFS is a promising agent for diagnosis of pancreatic cancer.

Fabrication of photoactive heterostructures based on quantum dots decorated with Au nanoparticles

Silica based multifunctional heterostructures, exhibiting near infrared (NIR) absorption (650-1200 nm) and luminescence in the visible region, represent innovative nanosystems useful for diagnostic or theranostic applications. Herein, colloidal synthetic procedures are applied to design a photoactive multifunctional nanosystem. Luminescent silica (SiO2) coated quantum dots (QDs) have been used as versatile nanoplatforms to assemble on their surface gold (Au) seeds, further grown into Au spackled structures. The synthesized nanostructures combine the QD emission in the visible region, and, concomitantly, the distinctive NIR absorption of Au nanodomains. The possibility of having multiple QDs in a single heterostructure, the SiO2 shell thickness, and the extent of Au deposition onto SiO2 surface have been carefully controlled. The work shows that a single QD entrapped in 16 nm thick SiO2 shell, coated with Au speckles, represents the most suitable geometry to preserve the QD emission in the visible region and to generate NIR absorption from metal NPs. The resulting architectures present a biomedical potential as an effective optical multimodal probes and as promising therapeutic agents due to the Au NP mediated photothermal effect.

IR-780 Loaded Phospholipid Mimicking Homopolymeric Micelles for Near-IR Imaging and Photothermal Therapy of Pancreatic Cancer

IR-780 iodide, a near-infrared (near-IR) fluorescent dye, can be utilized as an effective theranostic agent for both imaging and photothermal therapy. However, its lipophilicity limits its further biomedical applications. Herein, we synthesized a phospholipid mimicking amphiphilic homopolymer poly(12-(methacryloyloxy)dodecyl phosphorylcholine) (PMDPC) via reversible addition-fragmentation chain transfer (RAFT) polymerization. The amphiphilic homopolymer PMDPC can be self-assembled into micelles and used for the encapsulation of IR-780. The IR-780 loaded micelles (PMDPC-IR-780) exhibited low cytotoxicity in the dark, whereas remarkable photothermal cytotoxicity to pancreatic cancer cells (BxPC-3) was observed upon near-IR laser irradiation. We further investigated in vivo biodistribution of PMDPC-IR-780 micelles. Higher accumulation of PMDPC-IR-780 than that of free IR-780 in tumor tissue was verified, which might be ascribed to the enhanced permeability and retention (EPR) effect and long circulation time benefiting from the zwitterionic phosphorylcholine surface. Therefore, the IR-780 loaded phospholipid mimicking homopolymeric micelles could have great potential for cancer theranostics.

Stimuli-responsive cross-linked micelles for on-demand drug delivery against cancers

Stimuli-responsive cross-linked micelles (SCMs) represent an ideal nanocarrier system for drug delivery against cancers. SCMs exhibit superior structural stability compared to their non-cross-linked counterpart. Therefore, these nanocarriers are able to minimize the premature drug release during blood circulation. The introduction of environmentally sensitive cross-linkers or assembly units makes SCMs responsive to single or multiple stimuli present in tumor local microenvironment or exogenously applied stimuli. In these instances, the payload drug is released almost exclusively in cancerous tissue or cancer cells upon accumulation via enhanced permeability and retention effect or receptor mediated endocytosis. In this review, we highlight recent advances in the development of SCMs for cancer therapy. We also introduce the latest biophysical techniques, such as electron paramagnetic resonance (EPR) spectroscopy and fluorescence resonance energy transfer (FRET), for the characterization of the interactions between SCMs and blood proteins.

Two-photon-triggered drug delivery in cancer cells using nanoimpellers

A therapy of cancer cells: Two-photon-triggered camptothecin delivery with nanoimpellers was studied in MCF-7 breast cancer cells. A fluorophore with a high two-photon absorption cross-section was first incorporated in the nanoimpellers. Fluorescence resonance energy transfer (FRET) from the fluorophore to the azobenzene moiety was demonstrated.

Delivery of cancer therapeutics using nanotechnology

Nanoparticles have been investigated as drug carriers, because they provide a great opportunity due to their advantageous features: (i) various formulations using organic/inorganic materials, (ii) easy modification of targeting molecules, drugs or other molecules on them, (iii) effective delivery to target sites, resulting in high therapeutic efficacy and (iv) controlling drug release by external/internal stimuli. Because of these features, therapeutic efficacy can be improved and unwanted side effects can be reduced. Theranostic nanoparticles have been developed by incorporating imaging agents in drug carriers as all-in-one system, which makes it possible to diagnose and treat cancer by monitoring drug delivery behavior simultaneously. Recently, stimuli-responsive, activatable nanomaterials are being applied that are capable of producing chemical or physical changes by external stimuli. By using these nanoparticles, multiple tasks can be carried out simultaneously, e.g., early and accurate diagnosis, efficient cataloguing of patient groups of personalized therapy and real-time monitoring of disease progress. In this paper, we describe various types of nanoparticles for drug delivery systems, as well as theranostic systems.

Upconverting organic dye doped core-shell nano-composites for dual-modality NIR imaging and photo-thermal therapy

Nanotechnology approaches offer the potential for creating new optical imaging agents with unique properties that enable uses such as combined molecular imaging and photo-thermal therapy. Ideal preparations should fluoresce in the near-infrared (NIR) region to ensure maximal tissue penetration depth along with minimal scattering and light absorption. Due to their unique photophysical properties, upconverting ceramics such as NaYF₄:Er³⁺,Yb³⁺ nanoparticles have become promising optical materials for biological imaging. In this work, the design and synthesis of NaYF₄:Er³⁺,Yb³⁺@SiO₂ core-shell nano-composites, which contain highly absorbing NIR carbocyanine dyes in their outer silica shell, are described. These materials combine optical emission (from the upconverting core nanoparticle) with strong NIR absorption (from the carbocyanine dyes incorporated into the shell) to enable both optical imaging and photo-thermal treatment, respectively. Ultimately, this hybrid composite nanomaterial approach imparts the ability to both visualize, via upconversion imaging, and treat, via photo-thermal heating, using two distinct optical channels. Proof-of-principle in vitro experiments are presented to demonstrate the combined imaging and photo-thermal properties of this new functional nano-composite.

Nanomaterials for photo-based diagnostic and therapeutic applications

Photo-based diagnosis and treatment methods are gaining prominence due to increased spatial imaging resolution, minimally invasive modalities involved as well as localized treatment. Recently, nanoparticles (NPs) have been developed and used in photo-based therapeutic applications. While some nanomaterials have inherent photo-based imaging capabilities, others including polymeric NPs act as nanocarriers to deliver various fluorescent dyes or photosensitizers for photoimaging and therapeutic applications. These applications can vary from Magnetic Resonance Imaging (MRI) and optical imaging to photothermal therapy (PTT) and chemotherapy. Materials commonly used for development of photo-based NPs ranges from metal-based (gold, silver and silica) to polymer-based (chitosan, dextran, poly ethylene glycol (PEG) and poly lactic-co-glycolic acid (PLGA)). Recent research has paved the way for multi-modal 'theranostic' (a combination of therapy and diagnosis) nano-carriers capable of active targeting using cell-specific ligands and carrying multiple therapeutic and imaging agents for accurate diagnosis and controlled drug delivery. This review summarizes the different materials used today to synthesize photo-based NPs, their diagnostic and therapeutic applications as well as the current challenges faced in bringing these novel nano-carriers into clinical practices.

Luminescent silica nanoparticles for cancer diagnosis

Fluorescence imaging techniques are becoming essential for preclinical investigations, necessitating the development of suitable tools for in vivo measurements. Nanotechnology entered this field to help overcome many of the current technical limitations, and luminescent nanoparticles (NPs) are one of the most promising materials proposed for future diagnostic implementation. NPs also constitute a versatile platform that can allow facile multi-functionalization to perform multimodal imaging or theranostics (simultaneous diagnosis and therapy). In this contribution we have mainly focused on dye doped silica or silica-based NPs conjugated with targeting moieties to enable imaging of specific cancer cells. We also cite and briefly discuss a few non-targeted systems for completeness. We summarize common synthetic approaches to these materials, and then survey the most recent imaging applications of silica-based nanoparticles in cancer. The field of theranostics is particularly important and stimulating, so, even though it is not the central topic of this paper, we have included some significant examples. We conclude with a short section on NP-based systems already in clinical trials and examples of specific applications in childhood tumors. This review aims to describe and discuss, through focused examples, the great potential of these materials in the medical field, with the aim to encourage further research to implement applications, which today are still rare.

Fractionated photothermal antitumor therapy with multidye nanoparticles

Purpose

Photothermal therapy is an emerging cancer treatment paradigm which involves highly localized heating and killing of tumor cells, due to the presence of nanomaterials that can strongly absorb near-infrared (NIR) light. In addition to having deep penetration depths in tissue, NIR light is innocuous to normal cells. Little is known currently about the fate of nanomaterials post photothermal ablation and the implications thereof. The purpose of this investigation was to define the intratumoral fate of nanoparticles (NPs) after photothermal therapy in vivo and characterize the use of novel multidye theranostic NPs (MDT-NPs) for fractionated photothermal antitumor therapy.

Methods

The photothermal and fluorescent properties of MDT-NPs were first characterized. To investigate the fate of nanomaterials following photothermal ablation in vivo, novel MDT-NPs and a murine mammary tumor model were used. Intratumoral injection of MDT-NPs and real-time fluorescence imaging before and after fractionated photothermal therapy was performed to study the intratumoral fate of MDT-NPs. Gross tumor and histological changes were made comparing MDT-NP treated and control tumor-bearing mice.

Results

The dual dye-loaded mesoporous NPs (ie, MDT-NPs; circa 100 nm) retained both their NIR absorbing and NIR fluorescent capabilities after photoactivation. In vivo MDT-NPs remained localized in the intratumoral position after photothermal ablation. With fractionated photothermal therapy, there was significant treatment effect observed macroscopically (P = 0.026) in experimental tumor-bearing mice compared to control treated tumor-bearing mice.

Conclusion

Fractionated photothermal therapy for cancer represents a new therapeutic paradigm enabled by the application of novel functional nanomaterials. MDT-NPs may advance clinical treatment of cancer by enabling fractionated real-time image guided photothermal therapy.