Small gold nanorods laden macrophages for enhanced tumor coverage in photothermal therapy

Small Gold Nanorods: Recent Advances in Synthesis, Biological Imaging, and Cancer Therapy

Over the past few decades, the synthetic development of ultra-small nanoparticles has become an important strategy in nano-medicine, where smaller-sized nanoparticles are known to be more easily excreted from the body, greatly reducing the risk caused by introducing nano-theranostic agents. Gold nanorods are one of the most important nano-theranostic agents because of their special optical and electronic properties. However, the large size (diameter > 6 nm) of most obtained gold nanorods limits their clinical application. In recent years, more and more researchers have begun to investigate the synthesis and application of small gold nanorods (diameter < 6 nm), which exhibit similar optical and electronic properties as larger gold nanorods. In this review, we summarize the recent advances of synthesis of the small gold nanorods and their application for near-infrared light-mediated bio-imaging and cancer therapy.

Fluorine-free preparation of titanium carbide MXene quantum dots with high near-infrared photothermal performances for cancer therapy

Titanium carbide MXene quantum dots (QDs) were synthesized using an effective fluorine-free method as a biocompatible and highly efficient nanoagent for photothermal therapy (PTT) applications. In contrast to the traditional, hazardous and time-consuming process of HF pretreatment, our fluorine-free method is safe and simple. More importantly, abundant Al oxoanions were found to be modified on the MXene QD surface by the fluorine-free method, which endowed the QDs with strong and broad absorption in the NIR region. As a result, the as-prepared MXene QDs exhibited an extinction coefficient as large as 52.8 Lg^-1 cm^-1 at 808 nm and a photothermal conversion efficiency as high as 52.2%. Both the values are among the best reported so far. The as-prepared MXene QDs achieved simultaneous photoacoustic (PA) imaging and the remarkable PTT effect of tumors. Moreover, MXene QDs showed great biocompatibility without causing noticeable toxicity in vitro and in vivo, indicating their high potential for clinical applications.

Cellular Uptake and Intra-Organ Biodistribution of Functionalized Silica-Coated Gold Nanorods

PURPOSE

To develop a new nanobiosystem based on folate-functionalized silica-coated gold nanorods and to investigate its cellular uptake and intra-organ biodistribution in vitro and in vivo.

PROCEDURES

Ellipsoidal silica-coated gold nanorods (GNRs@SIO2) were prepared by seeded growth method using silicon dioxide (SIO2) as the shell material. Rhodamine-labeled GNRs@SiO2-folic acid (FA) were obtained by reacting the amino group located on GNRs@SiO2-FA with rhodamine isothiocyanate. The characteristics of the prepared GNRs@SiO2-FA were studied using transmission electron microscopy (TEM) and UV spectra. The 3-[4, 5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) colorimetric method was used to assess the biocompatibility of GNRs@SiO2-FA, and their uptake into cells was observed using TEM. In vivo experiments of cellular uptake and study of the intra-organ biodistribution of GNRs@SiO2-FA were detected using intrinsic two-photon luminescence.

RESULTS

Analysis of UV spectra confirmed the successfu1 preparation of GNRs@SiO2-FA. Results of the MTT assay demonstrated that surface modification of GNRs@SiO2-FA resulted in excellent biocompatibility. TEM examination revealed that GNRs@SiO2-FA entered the cells via endocytosis, which could connect to cancer cells with high folic acid expression. We found that GNRs exhibit bright luminescence and could be visualized in vivo by direct imaging of these particles within the tissue. Additionally, GNRs@SiO2-FA could specifically bind to tumor cells. GNRs@SiO2-FA entered tumor cells within 24 h and had a heterogeneous distribution with higher accumulation at the tumor cytoplasm.

CONCLUSION

GNRs@SiO2-FA can bind to cells and were found to be internalized by targeted folate receptor-expressing cells via a ligand-receptor-mediated endocytosis pathway, which is very useful in diagnosing diseases as well as in treating neoplasm with I-125 particles.

Mussel-inspired PLGA/polydopamine core-shell nanoparticle for light induced cancer thermochemotherapy

Most photothermal converting systems are not biodegradable, which bring the uneasiness when they are administered into human body due to the uncertainty of their fate. Hereby, we developed a mussel-inspired PLGA/polydopamine core-shell nanoparticle for cancer photothermal and chemotherapy. With the help of an anti-EGFR antibody, the nanoparticle could effectively enter head and neck cancer cells and convert near-infrared light to heat to trigger drug release from PLGA core for chemotherapy as well as ablate tumors by the elevated temperature. Due to the unique nanoparticle concentration dependent peak working-temperature nature, an overheating or overburn situation can be easily prevented. Since the nanoparticle was retained in the tumor tissue and subsequently released its payload inside the cancer cells, no any doxorubicin-associated side effects were detected. Thus, the developed mussel-inspired PLGA/polydopamine core-shell nanoparticle could be a safe and effective tool for the treatment of head and neck cancer.

STATEMENT OF SIGNIFICANCE

The described EGFR targeted PLGA/polydopamine core-shell nanoparticle (PLGA/PD NP) is novel in the following aspects: Different from most photothermal converting nanomaterials, PLGA/PD NP is biodegradable, which eliminates the long-term safety concerns thwarting the clinical application of photothermal therapy. Different from most photothermal nanomaterials, upon NIR irradiation, PLGA/PD NP quickly heats its surrounding environment to a NP concentration dependent peak working temperature and uniquely keeps that temperature constant through the duration of light irradiation. Due to this unique property an overheating or overburn situation for the adjacent healthy tissue can be easily avoided. The PLGA/PD NP releases its payload through detaching PD shell under NIR laser irradiation. The EGFR-targeted doxorubicin-loaded PLGA/PD NP effectively eradicate head and neck tumor in vivo through the synergism of photothermal therapy and chemotherapy while not introducing doxorubicin associated cardiotoxicity.

Indocyanine green-loaded gold nanostars for sensitive SERS imaging and subcellular monitoring of photothermal therapy

We have demonstrated that a typical nanothermometer was incorporated in a bovine serum albumin stabilized gold nanostar-indocyanine green (denoted as GNS-ICG-BSA) nanoprobe to realize surface-enhanced Raman scattering (SERS) imaging-based real-time sensitive monitoring of intracellular temperature in photothermal therapy (PTT), which significantly improved the spatial resolution compared to infrared thermal imaging. Herein, an exogenous thermosensitive molecule, ICG, acting as a tri-functional agent, was selected as the Raman reporter instead of direct cellular biochemical changes. The triggering of the obtained probe was unaffected by the cellular microenvironment, so it can act as a monitor of PTT in various cell types. High-resolution mass spectrometry (HRMS) was used to investigate the thermosensitive mechanism of ICG. The actively targeted GNS-ICG-BSA nanotags were used to induce SERS mapping-guided in vitro PTT of U87 glioma cells. Meanwhile, small temperature variations within a cell during PTT can be precisely monitored through the SERS fingerprint information, with a spatial resolution at the subcellular level and a sensitivity of 0.37 °C. Thus, the integrated GNS-ICG-BSA nanotags can be treated as a theranostic probe, a SERS imaging probe and an intracellular thermometer. Moreover, the good biocompatibility and the low cytotoxicity of GNS-ICG-BSA nanotags, together with their superior photothermal ablation effect on U87 glioma cells have been confirmed. This suggested that the implanted nanothermometry approach would be promising for a better understanding of the biological processes at subcellular level and provide new insights into the fabrication of a multifunctional nanoplatform. Furthermore, this study revealed that the SERS-based monitoring technique can offer great potential for theranostics as an emerging strategy.

Albumin-Gold Nanorod Nanoplatform for Cell-Mediated Tumoritropic Delivery with Homogenous ChemoDrug Distribution and Enhanced Retention Ability

Recently, living cells with tumor-homing properties have provided an exciting opportunity to achieve optimal delivery of nanotherapeutic agents. However, premature payload leakage may impair the host cells, often leading to inadequate in vivo investigations or therapeutic efficacy. Therefore, a nanoplatform that provides a high drug-loading capacity and the precise control of drug release is required. In the present study, a robust one-step synthesis of a doxorubicin (DOX)-loaded gold nanorod/albumin core-shell nanoplatform (NR@DOX:SA) was designed for effective macrophage-mediated delivery to demonstrate how nanoparticle-loaded macrophages improve photothermal/chemodrug distribution and retention ability to achieve enhanced antitumor effects. The serum albumin shell of these nanoagents served as a drug reservoir to delay the intracellular DOX release and drug-related toxicity that impairs the host cell carriers. Near-infrared laser irradiation enabled on-demand payload release to destroy neighboring tumor cells. A series of in vivo quantitative analyses demonstrated that the nanoengineered macrophages delivered the nanodrugs through tumor-tropic migration to tumor tissues, resulting in the twice homogenous and efficient photothermal activations of drug release to treat prostate cancer. By contrast, localized pristine NR@DOX:SAs exhibit limited photothermal drug delivery that further reduces their retention ability and therapeutic efficacy after second combinational treatment, leading to a failure of cancer therapy. Moreover, the resultant unhealable wounds impair quality of life. Free DOX has rapid clearance and therefore exhibits limited antitumor effects. Our findings suggest that in comparison with pristine nanoparticles or free DOX, the nanoengineered macrophages effectively demonstrate the importance and effect of homogeneous drug distribution and retention ability in cancer therapy.

Near-infrared induced phase-shifted ICG/Fe3O4 loaded PLGA nanoparticles for photothermal tumor ablation

Near-infrared (NIR) laser-induced photothermal therapy (PTT) uses a photothermal agent to convert optical energy into thermal energy and has great potential as an effective local, minimally invasive treatment modality for killing cancer cells. To improve the efficacy of PTT, we developed poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) encapsulating superparamagnetic iron oxide (Fe3O4), indocyanine green (ICG), and perfluoropentane (PFP) as synergistic agents for NIR laser-induced PTT. We fabricated a novel type of phase-shifting fluorescent magnetic NPs, Fe3O4/ICG@PLGA/PFP NPs, that effectively produce heat in response to NIR laser irradiation for an enhanced thermal ablation effect and a phase-shift thermoelastic expansion effect, and thus, can be used as a photothermal agent. After in vitro treatment of MCF-7 breast cancer cells with Fe3O4/ICG@PLGA/PFP NPs and NIR laser irradiation, histology and electron microscopy confirmed severe damage to the cells and the formation of many microbubbles with iron particles at the edge or outside of the microbubbles. In vivo experiments in mice with MCF-7 tumors demonstrated that Fe3O4/ICG@PLGA/PFP NPs could achieve tumor ablation upon NIR laser irradiation with minimal toxicity to non-irradiated tissues. Together, our results indicate that Fe3O4/ICG@PLGA/PFP NPs can be used as effective nanotheranostic agents for tumor ablation.

Photothermal therapy of single cancer cells mediated by naturally created gold nanorod clusters

Gold nanorods (GNRs) are generally considered to be nontoxic to normal and cancer cells. They are usually accumulated at lysosomes after entering into cells, forming GNR clusters in which strong plasmonic coupling between GNRs is expected. We investigated the photothermal therapy of single cancer cells by exploiting the significantly enhanced two-photon-induced absorption of GNR clusters naturally created in the lysosomes of cancer cells. It was revealed numerically that the plasmonic coupling between GNRs in GNR clusters can effectively enhance the photothermal conversion efficiency. As a result, the thermal damage of single cancer cells can be induced by using pulse energy as low as ~70 pJ. In experiments, the locations of GNR clusters can be accurately determined through the detection of the two-photon-induced luminescence, which is also significantly enhanced, by using a confocal laser scanning microscope. The photothermal therapy was conducted by focusing femtosecond laser light on the targeted GNR clusters, generating bubbles and deforming cell membranes. The photothermal therapy proposed in this work can lead to the rapid and acute injury of single cancer cells. The dependence of the apoptosis time on the pulse energy of femtosecond laser light was also examined. Our findings suggest a novel strategy for the photothermal therapy of single cancer cells with ultralow energy.

Comparative Analysis of Methods for Enhancement of the Photostability of CdTe@TGA QD Colloid Solutions

The employment of colloid quantum dots in a number of applications is limited by their instability under light irradiation. Additional methods of photostability enhancement of UV+visible-irradiated TGA-stabilized CdTe quantum dots are investigated. Photostability enhancement was observed via either addition of sodium sulphite in the role of chemical oxygen absorber or addition of 1% gelatin, or, finally, by additional stabilization by bovine serum albumine (BSA). The latter method is the most promising, since it not only enhances the quantum dots' photostability but also makes them more biocompatible and extends the possibilities of their biological applications.

A multifunctional organosilica cross-linker for the bio-conjugation of gold nanorods

We report on the use of organosilica shells to couple gold nanorods to functional peptides and modulate their physiochemical and biological profiles. In particular, we focus on the case of cell penetrating peptides, which are used to load tumor-tropic macrophages and implement an innovative drug delivery system for photothermal and photoacoustic applications. The presence of organosilica exerts subtle effects on multiple parameters of the particles, including their size, shape, electrokinetic potential, photostability, kinetics of endocytic uptake and cytotoxicity, which are investigated by the interplay of colorimetric methods and digital holographic microscopy. As a rule of thumb, as the thickness of organosilica increases from none to ∼30nm, we find an improvement of the photophysical performances at the expense of a deterioration of the biological parameters. Therefore, detailed engineering of the particles for a certain application will require a careful trade-off between photophysical and biological specifications.

Designing Core-Shell Gold and Selenium Nanocomposites for Cancer Radiochemotherapy

Radiotherapy is an important regime for treating malignant tumors. There is interest in the development of radiosensitizers to increase the local treatment efficacy under a relatively low and safe radiation dose. In this study, we designed Au@Se-R/A nanocomposites (Au@Se-R/A NCs) as nano-radiosensitizer to realize synergistic radiochemotherapy based on the radiotherapy sensitization property of Au nanorods (NRs) and antitumor activity of Se NPs. In vitro studies show that the combined treatment of A375 melanoma cells in culture with NCs and X-ray induces cell apoptosis through alteration in expression of p53 and DNA-damaging genes and triggers intracellular ROS overproduction, leading to greatly enhanced anticancer efficacy. Further studies using clinically used radiotherapy equipment demonstrate that the combined treatment of NCs and X-ray significantly inhibits the tumor growth in vivo and shows negligible acute toxicity to the major organs. Taken together, this study provides a strategy for clinical translation application of nanomedicne in cancer radiochemotherapy.

Microfluidic Electroporation-Facilitated Synthesis of Erythrocyte Membrane-Coated Magnetic Nanoparticles for Enhanced Imaging-Guided Cancer Therapy

Biomimetic cell membrane-coated nanoparticles (CM-NPs) with superior biochemical properties have been broadly utilized for various biomedical applications. Currently, researchers primarily focus on using ultrasonic treatment and mechanical extrusion to improve the synthesis of CM-NPs. In this work, we demonstrate that microfluidic electroporation can effectively facilitate the synthesis of CM-NPs. To test it, Fe₃O₄ magnetic nanoparticles (MNs) and red blood cell membrane-derived vesicles (RBC-vesicles) are infused into a microfluidic device. When the mixture of MNs and RBC-vesicles flow through the electroporation zone, the electric pulses can effectively promote the entry of MNs into RBC-vesicles. After that, the resulting RBC membrane-capped MNs (RBC-MNs) are collected from the chip and injected into experimental animals to test the in vivo performance. Owing to the superior magnetic and photothermal properties of the MN cores and the long blood circulation characteristic of the RBC membrane shells, core-shell RBC-MNs were used for enhanced tumor magnetic resonance imaging (MRI) and photothermal therapy (PTT). Due to the completer cell membrane coating, RBC-MNs prepared by microfluidic electroporation strategy exhibit significantly better treatment effect than the one fabricated by conventional extrusion. We believe the combination of microfluidic electroporation and CM-NPs provides an insight into the synthesis of bioinpired nanoparticles to improve cancer diagnosis and therapy.

Cell-borne 2D nanomaterials for efficient cancer targeting and photothermal therapy

Two of the challenges for clinical implementation of nano-therapeutic strategies are optimization of tumor targeting and clearance of the nanoagents in vivo. Herein, a cell-mediated therapy by transporting 2D Bi₂Se₃ nanosheets within macrophage vehicles is described. The Bi₂Se₃ nanosheets with excellent near-infrared photothermal performance exhibit high macrophage uptake and negligible cytotoxicity thus facilitating the fabrication of Bi₂Se₃-laden-macrophages. Compared with bare Bi₂Se₃, the Bi₂Se₃-laden-macrophages after intravenous injection show prolonged blood circulation and can overcome the hypoxia-associated drug delivery barrier to target the tumor efficiently and dramatically enhance the efficiency of photothermal cancer therapy. The Bi₂Se₃-laden-macrophages possess good biocompatibility as demonstrated by the biochemical and histological analyses and furthermore, most of the materials are excreted from the body within 25 days. Our findings reveal a desirable system for highly efficient near-infrared photothermal cancer therapy.

Smart Nanostructures for Cargo Delivery: Uncaging and Activating by Light

Nanotechnology has begun to play a remarkable role in various fields of science and technology. In biomedical applications, nanoparticles have opened new horizons, especially for biosensing, targeted delivery of therapeutics, and so forth. Among drug delivery systems (DDSs), smart nanocarriers that respond to specific stimuli in their environment represent a growing field. Nanoplatforms that can be activated by an external application of light can be used for a wide variety of photoactivated therapies, especially light-triggered DDSs, relying on photoisomerization, photo-cross-linking/un-cross-linking, photoreduction, and so forth. In addition, light activation has potential in photodynamic therapy, photothermal therapy, radiotherapy, protected delivery of bioactive moieties, anticancer drug delivery systems, and theranostics (i.e., real-time monitoring and tracking combined with a therapeutic action to different diseases sites and organs). Combinations of these approaches can lead to enhanced and synergistic therapies, employing light as a trigger or for activation. Nonlinear light absorption mechanisms such as two-photon absorption and photon upconversion have been employed in the design of light-responsive DDSs. The integration of a light stimulus into dual/multiresponsive nanocarriers can provide spatiotemporal controlled delivery and release of therapeutic agents, targeted and controlled nanosystems, combined delivery of two or more agents, their on-demand release under specific conditions, and so forth. Overall, light-activated nanomedicines and DDSs are expected to provide more effective therapies against serious diseases such as cancers, inflammation, infections, and cardiovascular disease with reduced side effects and will open new doors toward the treatment of patients worldwide.

Exploiting the cancer niche: Tumor-associated macrophages and hypoxia as promising synergistic targets for nano-based therapy

The tumor microenvironment has been widely exploited as an active participant in tumor progression. Extensive reports have defined the dual role of tumor-associated macrophages (TAMs) in tumor development. The protumoral effect exerted by the M2 phenotype has been correlated with a negative outcome in most solid tumors. The high infiltration of immune cells in the hypoxic cores of advanced solid tumors leads to a chain reaction of stimuli that enhances the expression of protumoral genes, thrives tumor malignancy, and leads to the emergence of drug resistance. Many studies have shown therapeutic targeting systems, solely to TAMs or tumor hypoxia, however, novel therapeutics that target both features are still warranted. In the present review, we discuss the role of hypoxia in tumor development and the clinical outcome of hypoxia-targeted therapeutics, such as hypoxia-inducible factor (HIF-1) inhibitors and hypoxia-activated prodrugs. Furthermore, we review the state-of-the-art of macrophage-based cancer therapy. We thoroughly discuss the development of novel therapeutics that simultaneously target TAMs and tumor hypoxia. Nano-based systems have been highlighted as interesting strategies for dual modality treatments, with somewhat improved tissue extravasation. Such approach could be seen as a promising strategy to overcome drug resistance and enhance the efficacy of chemotherapy in advanced solid and metastatic tumors, especially when exploiting cell-based nanotherapies. Finally, we provide an in-depth opinion on the importance of exploiting the tumor microenvironment in cancer therapy, and how this could be translated to clinical practice.

Bulk Surfaces Coated with Triangular Silver Nanoplates: Antibacterial Action Based on Silver Release and Photo-Thermal Effect

A layer of silver nanoplates, specifically synthesized with the desired localized surface plasmon resonance (LSPR) features, was grafted on amino-functionalized bulk glass surfaces to impart a double antibacterial action: (i) the well-known, long-term antibacterial effect based on the release of Ag⁺; (ii) an "on demand" action which can be switched on by the use of photo-thermal properties of silver nano-objects. Irradiation of these samples with a laser having a wavelength falling into the so called "therapeutic window" of the near infrared region allows the reinforcement, in the timescale of minutes, of the classical antibacterial effect of silver nanoparticles. We demonstrate how using the two actions allows for almost complete elimination of the population of two bacterial strains of representative Gram-positive and Gram-negative bacteria.

Chemo-photothermal therapy of cancer cells using gold nanorod-cored stimuli-responsive triblock copolymer

The combination of photothermal therapy and chemotherapy, when carefully planned, has been shown to be an effective cancer treatment option clinically and preclinically.

Near-infrared light and pH-responsive Au@carbon/calcium phosphate nanoparticles for imaging and chemo-photothermal cancer therapy of cancer cells

A novel Au@carbon/calcium phosphate core–shell nanoparticles were synthesized for CT imaging and chemo-photothermal cancer therapy in vitro.

Comparison of four methods for the biofunctionalization of gold nanorods by the introduction of sulfhydryl groups to antibodies

Introducing sulfhydryl groups to biomolecules to functionalize gold nanorods (GNRs) is an attractive method that involves the creation of a strong Au-S bond. Previously, we developed a facile method to functionalize GNR surfaces by thiolating antibodies using Traut's reagent. In the current study, we evaluated several methods for the introduction of thiol groups onto the surface of GNRs by using Traut's reagent, dithiotreitol (DTT), dithiolaromatic PEG6-CONHNH₂, and thiol-polyethylene glycolamine (SH-PEG-NH₂) combined with EDC reaction. We showed that the four above-mentioned thiolation methods can efficiently functionalize GNRs and simplify the functionalization procedures. The formed GNR-bioconjugates showed superior stability without compromising the biological activity. The GNR nanochip prepared with these four thiolated antibodies can detect human IgG targets with specificity. However, SH-PEG-NH₂ combined with EDC reaction may affect the amount of functionalized GNRs because of the efficiency of thiol moiety linkage to antibodies, thereby affecting the sensitivity of the GNR sensor. The introduction of a thiol group to antibodies by using Traut's reagent, DTT, and PEG6-CONHNH₂ allowed for direct immobilization onto the GNR surface, improved the efficacy of functionalized GNRs, and increased the sensitivity in response to target detection as a biosensor. Given that PEG6-CONHNH₂ modification requires glycosylated biomolecules, Traut's reagent and DTT thiolation are recommended as universal applications of GNR biofunctionalization and can be easily extended to other sensing applications based on other gold nanostructures or new biomolecules.

Multimodal imaging and photothermal therapy were simultaneously achieved in the core–shell UCNR structure by using single near-infrared light

Core–shell nanostructures consisting of plasmonic materials and lanthanide-doped upconversion nanoparticles (UCNPs) show promising applications in theranostics including bio-imaging, diagnosis and therapy.

Hollow Au loaded with kanamycin for pharmacological and laser-triggered photothermal sterilization

Anti-E. coli-conjugated and kanamycin-loaded hAuNPs (hAuNPs-anti-E. coli-kana) were prepared for sterilization.

Synthesis of a core/satellite-like multifunctional nanocarrier for pH- and NIR-triggered intracellular chemothermal therapy and tumor imaging

A core/satellite-like multifunctional system was developed for synergistic chemothermal therapy and tumor imaging based on the AuNRs capped mesoporous silica nanocarrier with UCNP core.

Bio-inspired synthesis of PEGylated polypyrrole@polydopamine nanocomposites as theranostic agents for T1-weighted MR imaging guided photothermal therapy

Polypyrrole nanoparticle (PPy) based theranostic agents for magnetic resonance imaging (MRI) guided photothermal therapy (PTT) have received increasing attention in recent years.

Composite scaffolds of gelatin and gold nanoparticles with tunable size and shape for photothermal cancer therapy

Photothermal therapy (PTT) has been extensively investigated as a promising strategy for cancer therapy. For successful application of this technique, various nanomaterials have been explored as photothermal conversion agents. Gold nanoparticles (AuNPs), especially Au nanorods and Au nanostars, have received much attention for photothermal therapy because of their facile preparation and high photothermal conversion efficiency. Due to the limited accumulation and easy diffusion of free nanoparticles, incorporation of nanoparticles into scaffolds for direct implantation has been demonstrated as an attractive way for cancer therapy applications. In this study, composite porous scaffolds of gelatin and AuNPs were prepared by introducing Au nanorods and Au nanostars with average sizes of around 35.0, 65.0 and 115.0 nm in gelatin scaffolds. The composite scaffolds were used for the localized PTT application of cancer cells. Gel/AuNP composite scaffolds supported cell adhesion and showed good biocompatibility. Temperature in the composite scaffolds increased quickly upon NIR laser irradiation. Photothermal efficiency and cancer cell killing efficiency were dependent on the shape, size and amount of AuNPs in the composite scaffolds. The composite scaffolds prepared with 65.0 nm Au nanorods showed the highest photothermal efficiency and cell killing efficiency. The results indicated the importance of the shape and size modulation of AuNPs for photothermal therapy applications.

A Porphyrin-Based Conjugated Polymer for Highly Efficient In Vitro and In Vivo Photothermal Therapy

Conjugated polymers have been increasingly studied for photothermal therapy (PTT) because of their merits including large absorption coefficient, facile tuning of exciton energy dissipation through nonradiative decay, and good therapeutic efficacy. The high photothermal conversion efficiency (PCE) is the key to realize efficient PTT. Herein, a donor-acceptor (D-A) structured porphyrin-containing conjugated polymer (PorCP) is reported for efficient PTT in vitro and in vivo. The D-A structure introduces intramolecular charge transfer along the backbone, resulting in redshifted Q band, broadened absorption, and increased extinction coefficient as compared to the state-of-art porphyrin-based photothermal reagent. Through nanoencapsulation, the dense packing of a large number of PorCP molecules in a single nanoparticle (NP) leads to favorable nonradiative decay, good photostability, and high extinction coefficient of 4.23 × 10⁴ m^-1 cm^-1 at 800 nm based on porphyrin molar concentration and the highest PCE of 63.8% among conjugated polymer NPs. With the aid of coloaded fluorescent conjugated polymer, the cellular uptake and distribution of the PorCP in vitro can be clearly visualized, which also shows effective photothermal tumor ablation in vitro and in vivo. This research indicates a new design route of conjugated polymer-based photothermal therapeutic materials for potential personalized theranostic nanomedicine.

Reverse Size Dependences of the Cellular Uptake of Triangular and Spherical Gold Nanoparticles

Gold nanoparticles (GNPs) show promise as both drug and imaging carriers with applications in both diagnosis and therapy. For the safe and effective use of such gold nanomaterials in the biomedical field, it is crucial to understand how the size and shape of the nanomaterials affect their biological features, such as in vitro cellular uptake speed and accumulation as well as cytotoxicity. Herein, we focus on triangular gold nanoparticles (TNPs) of four different sizes (side length 46, 55, 72, and 94 nm; thickness 30 nm) and compare the cellular internalization efficiency with those of spherical nanoparticles (SNPs) of various diameters (22, 39, and 66 nm). Both surfaces were coated with anionic thiol ligands. Inductively coupled plasma-emission spectrometry (ICP-ES) data demonstrated that TNPs with longer sides showed higher levels of uptake into RAW264.7 and HeLa cells. On the other hand, in the case of SNPs, those with smaller diameters showed higher levels of uptake in both cells. Our results support the notion of a reverse size dependence of TNPs and SNPs in terms of cellular uptake. For HeLa cells, in particular, 20-fold more efficient internalization was observed for TNPs with longer sides (72 nm side length) compared to SNPs (66 nm) with a similar surface area. These results highlight the importance of the shape of nanomaterials on their interactions with cells and provide a useful guideline for the use of TNPs.

Biodegradable black phosphorus-based nanospheres for in vivo photothermal cancer therapy

Photothermal therapy (PTT) offers many advantages such as high efficiency and minimal invasiveness, but clinical adoption of PTT nanoagents have been stifled by unresolved concerns such as the biodegradability as well as long-term toxicity. Herein, poly (lactic-co-glycolic acid) (PLGA) loaded with black phosphorus quantum dots (BPQDs) is processed by an emulsion method to produce biodegradable BPQDs/PLGA nanospheres. The hydrophobic PLGA not only isolates the interior BPQDs from oxygen and water to enhance the photothermal stability, but also control the degradation rate of the BPQDs. The in vitro and in vivo experiments demonstrate that the BPQDs/PLGA nanospheres have inappreciable toxicity and good biocompatibility, and possess excellent PTT efficiency and tumour targeting ability as evidenced by highly efficient tumour ablation under near infrared (NIR) laser illumination. These BP-based nanospheres combine biodegradability and biocompatibility with high PTT efficiency, thus promising high clinical potential.

Near infrared light responsive hybrid nanoparticles for synergistic therapy

A near infrared (NIR) light responsive chromophore 7-(diethylamino)-4-(hydroxymethyl)-2H-chromen-2-one (DEACM) was synthesized and incorporated to β-cyclodextrins with cRGD functionalized poly(ethylene glycol), the amphiphiles were coordinated with Au nanorods or nanoparticles to load anticancer drug doxorubicin (DOX) for fabricating hybrid nanoparticles. The π-π stacking interaction between DEACM and DOX was formed in the hybrid nanoparticles, which contributed to the high drug loading content. The Au nanorods or nanoparticles enhanced the photosolvolysis of DEACM under the irradiation of NIR with 808 nm wavelength and triggered the accelerated drug release from the nanoparticles. The drug loaded hybrid nanoparticles with NIR irradiation exhibited efficient inhibition effect on the proliferation of 4T1 breast cancer cells in vitro. The in vivo anticancer activity study on breast cancer bearing mice revealed that the hybrid nanoparticles containing Au nanorods exhibited excellent anticancer activity under the irradiation of 808 nm wavelength NIR with 800 mW.

Current Status and Future Direction of Nanomedicine: Focus on Advanced Biological and Medical Applications

Nanotechnology is the engineering and manipulation of materials and devices with sizes in the nanometer range. Colloidal gold, iron oxide nanoparticles and quantum dot semiconductor nanocrystals are examples of nanoparticles, with sizes generally ranging from 1 to 20 nm. These nanotechnologies have been researched tremendously in the last decade and this has led to a new area of "nanomedicine" which is the application of nanotechnology to human health-care for diagnosis, monitoring, treatment, prediction and prevention of diseases. Recently progress has been made in overcoming some of the difficulties in the human use of nanomedicines. In the mid-1990s, Doxil was approved by the FDA, and now various nanoconstructs are on the market and in clinical trials. However, there are many obstacles in the human application of nanomaterials. For translation to clinical use, a detailed understanding is needed of the chemical and physical properties of particles and their pharmacokinetic behavior in the body, including their biodistribution, toxicity, and biocompatibility. In this review, we provide a broad introduction to nanomedicines and discuss the preclinical and clinical trials in which they have been evaluated.

Preparation of gelatin/Fe3O4 composite scaffolds for enhanced and repeatable cancer cell ablation

Various nanomaterials have been extensively investigated for photothermal ablation of cancer cells because of their high photothermal conversion efficiency. However, the poor targeting specificity and low repeated heating efficiency of nanomaterials restrict their applications in the clinic. In this work, porous gelatin/iron oxide (Gel/Fe₃O₄) composite scaffolds were prepared by a facile ice particulate templating method for efficient and repeatable cancer cell ablation. Gel/Fe₃O₄ composite scaffolds showed controlled porous structure consisting of large pores and interconnecting small pores. The strong absorption in the near-infrared (NIR) region enabled the Gel/Fe₃O₄ composite scaffolds to elevate local temperature quickly under NIR laser irradiation. The composite scaffolds allowed cell adhesion and proliferation showing good biocompatibility. Cancer cells entrapped in the scaffolds could be efficiently killed during laser irradiation. Moreover, the therapeutic efficacy of Gel/Fe₃O₄ composite scaffolds could be enhanced by repeated laser irradiation treatment, which is important for clinical application because of the resistant and recurrent nature of cancer. The results indicated that the porous Gel/Fe₃O₄ composite scaffolds had good biocompatibility and excellent cancer cell ablation efficacy, which may provide an attractive way to use porous scaffolds for cancer therapy application.

Metabolizable Ultrathin Bi2 Se3 Nanosheets in Imaging-Guided Photothermal Therapy

Poly(vinylpyrrolidone)-encapsulated Bi2 Se3 nanosheets with a thickness of 1.7 nm and diameter of 31.4 nm are prepared by a solution method. Possessing an extinction coefficient of 11.5 L g(-1) cm(-1) at 808 nm, the ultrathin Bi2 Se3 nanosheets boast a high photothermal conversion efficiency of 34.6% and excellent photoacoustic performance. After systemic administration, the Bi2 Se3 nanosheets with the proper size and surface properties accumulate passively in tumors enabling efficient photoacoustic imaging of the entire tumors to facilitate photothermal cancer therapy. In vivo biodistribution studies reveal that they are expelled from the body efficiently after 30 d. The ultrathin Bi2 Se3 nanosheets have large clinical potential as metabolizable near-infrared-triggered theranostic agents.

Tubelike Gold Sphere-Attapulgite Nanocomposites with a High Photothermal Conversion Ability in the Near-Infrared Region for Enhanced Cancer Photothermal Therapy

Near-infrared (NIR)-induced photothermal therapy (PTT) is now considered to be a promising and highly efficient method for tumor therapy. Photothermal agents play a crucial role in PTT, and they are required to possess the ability to harvest NIR light and transform the photon energy into heat energy. This work reports a facile method to synthesize a new PTT agent, which is based on the electrostatic binding of the Au nanospheres (Au NSs, ∼15 nm) to the surface of a nanometer-sized mineral, attapulgite, to form tubelike Au-attapulgite nanocomposites. These nanocomposites consist of numerous Au NSs, which are linked to each other along the attapulgite surface. The nanocomposites exhibit similar localized surface plasmon resonance absorption characteristics to those of Au nanorods with a longitudinal absorption mode that shifts to the NIR region (∼670 nm). Moreover, the nanocomposites have a high Cabs/Csca ratio (cross section of absorption to scattering) and photothermal conversion efficiency of 25.6%. Their photothermal therapy effect is studied using A549 cells and A549 cell-bearing nude mice as examples. The results indicate that the nanocomposites can be effectively taken up by the cells, and the nanocomposites show good biocompatibility. The A549 cells almost died after they were incubated with the nanocomposites (at 100 μg mL(-1)) for 12 h and irradiated by an 808 nm laser with a power density of 0.5 W cm(-2) for 15 min. The tumors of nude mice can also be effectively ablated without regrowth during the period of observation (at least 10 d) after photothermal therapy.

Strategies for improving the intratumoral distribution of liposomal drugs in cancer therapy

INTRODUCTION

A major limitation of current liposomal cancer therapies is the inability of liposome therapeutics to penetrate throughout the entire tumor mass. This inhomogeneous distribution of liposome therapeutics within the tumor has been linked to treatment failure and drug resistance. Both liposome particle transport properties and tumor microenvironment characteristics contribute to this challenge in cancer therapy. This limitation is relevant to both intravenously and intratumorally administered liposome therapeutics.

AREAS COVERED

Strategies to improve the intratumoral distribution of liposome therapeutics are described. Combination therapies of intravenous liposome therapeutics with pharmacologic agents modulating abnormal tumor vasculature, interstitial fluid pressure, extracellular matrix components, and tumor associated macrophages are discussed. Combination therapies using external stimuli (hyperthermia, radiofrequency ablation, magnetic field, radiation, and ultrasound) with intravenous liposome therapeutics are discussed. Intratumoral convection-enhanced delivery (CED) of liposomal therapeutics is reviewed.

EXPERT OPINION

Optimization of the combination therapies and drug delivery protocols are necessary. Further research should be conducted in appropriate cancer types with consideration of physiochemical features of liposomes and their timing sequence. More investigation of the role of tumor associated macrophages in intratumoral distribution is warranted. Intratumoral infusion of liposomes using CED is a promising approach to improve their distribution within the tumor mass.