Highly Efficient, Wavelength-Tunable, Gold Nanoparticle Based Optothermal Nanoconvertors

Chitosan- and hyaluronic acid-based nanoarchitectures in phototherapy: Combination cancer chemotherapy, immunotherapy and gene therapy

Cancer phototherapy has been introduced as a new potential modality for tumor suppression. However, the efficacy of phototherapy has been limited due to a lack of targeted delivery of photosensitizers. Therefore, the application of biocompatible and multifunctional nanoparticles in phototherapy is appreciated. Chitosan (CS) as a cationic polymer and hyaluronic acid (HA) as a CD44-targeting agent are two widely utilized polymers in nanoparticle synthesis and functionalization. The current review focuses on the application of HA and CS nanostructures in cancer phototherapy. These nanocarriers can be used in phototherapy to induce hyperthermia and singlet oxygen generation for tumor ablation. CS and HA can be used for the synthesis of nanostructures, or they can functionalize other kinds of nanostructures used for phototherapy, such as gold nanorods. The HA and CS nanostructures can combine chemotherapy or immunotherapy with phototherapy to augment tumor suppression. Moreover, the CS nanostructures can be functionalized with HA for specific cancer phototherapy. The CS and HA nanostructures promote the cellular uptake of genes and photosensitizers to facilitate gene therapy and phototherapy. Such nanostructures specifically stimulate phototherapy at the tumor site, with particle toxic impacts on normal cells. Moreover, CS and HA nanostructures demonstrate high biocompatibility for further clinical applications.

A plasmonic fluorescent ratiometric temperature sensor for self-limiting hyperthermic applications utilizing FRET enhancement in the plasmonic field

Nanoparticle mediated photo-induced hyperthermia holds much promise as a therapeutic solution for the management of diseases like cancer. The conventional methods of temperature measurements do not measure the actual temperature generated in the vicinity of the nanoparticles during illumination. In contrast, nano temperature sensors built on hyperthermic nanoparticles can relay local temperatures around the nanoparticles during thermal induction. In this study, we present a core shell construct consisting of a plasmonic core and a silica shell encapsulating a FRET pair of organic dyes for such application. The plasmonic core imparts photo-induced hyperthermic properties to the nanoconstruct, while the fluorescent shell enables ratiometric sensing of temperature. We see that even at a low dye encapsulation concentration, the shell displays a linear ratiometric fluorescence response to temperature and high energy transfer between the dye pair. Interestingly, Monte Carlo simulations, without considering the plasmonic core, show that the energy transfer in the system should be much smaller than that observed, confirming plasmon enhancement in the FRET energy transfer. We also show the ratiometric temperature measurement using these particles during photoinduced hyperthermia. This study suggests the use of plasmonic nanoparticles in the next generation "self-limiting" photothermal therapy.

Folate targeting self-limiting hyperthermic nanoparticles for controlled photothermal therapy

Photothermal therapy utilizes photothermal agents and the use of nanoparticle agents is deemed advantageous for multiple reasons. Common nano-photothermal agents normally have high conversion efficiencies and heating rates, but bulk temperature measurement methods do not adequately represent the nanoscale temperatures of these nanoheaters. Herein, we report on the fabrication of self-limiting hyperthermic nanoparticles that can simultaneously photoinduce hyperthermia and report back temperature ratiometrically. The synthesized nanoparticles utilize a plasmonic core to achieve the photoinduced hyperthermic property and fluorescent FRET pairs entrapped in a silica shell to impart the ratiometric temperature sensing ability. The studies demonstrate the photoinduced hyperthermia with simultaneous temperature measurement using these particles and show that the particles can achieve a conversion efficiency of 19.5% despite the shell architecture. These folate-functionalized self-limiting photothermal agents are also used to demonstrate targeted photoinduced hyperthermia in a HeLa cell model.

A Synergistic Combination of AuNRs and C Dots as a Multifunctional Material for Ice Recrystallization Inhibition and Rapid Rewarming

Robust platforms and advanced biocompatible materials having diverse performances are in tremendous demand for cryopreservation of biocells, which are greatly limited by the crystallization, formation, and growth of ice crystals. The fickle structure and the arduous extraction process of modern attainable antifreezing proteins cause fatal cryoinjury of the cells making it challenging to develop anti-icing materials. Thus, designing Au colloids is an effective way to combat cell-damaging concerns during the ice freezing-thawing process. Herein, we propose an emerging biomimetic hybrid nanomaterial (AuNR@SiO₂-CDs) prepared by combining the photoheating and rewarming controlling characteristics of carbon dots (CDs) and gold nanorods (AuNRs), respectively, via a SiO₂ scaffold that has an optimal aspect ratio of ∼4.4. The performance of the material is applied in the freezing and resuscitation of Hela cells. The typical linkage between the AuNR and CDs not only retains the stable structure but also possesses the symmetric functional characteristics of affirmative cryoprotectant materials and sustained low cytotoxicity of cell viability >90%. The cell recovery rate of the Hela cell is significantly improved to ∼60%, which is propped up to >4% higher by the laser irradiation dose. The above hybrid material is paving a path toward novel bionic antifreezing proteins and is envisioned for ice recrystallization inhibition and rapid rewarming.

Preparation and Evaluation of 64Cu-Radiolabled Dual-Ligand Multifunctional Gold Nanoparticles for Tumor Theragnosis

Gold nanoparticles (AuNPs) are cutting-edge platforms for combined diagnostic and therapeutic approaches due to their exquisite physicochemical and optical properties. Using the AuNPs physically produced by femtosecond pulsed laser ablation of bulk Au in deionized water, with a capping agent-free surface, the conjugation of functional ligands onto the AuNPs can be tunable between 0% and 100% coverage. By taking advantage of this property, AuNPs functionalized by two different types of active targeting ligands with predetermined ratios were fabricated. The quantitatively controllable conjugation to construct a mixed monolayer of multiple biological molecules at a certain ratio onto the surface of AuNPs was achieved and a chelator-free ⁶⁴Cu-labeling method was developed. We report here the manufacture, radiosynthesis and bioevaluation of three different types of dual-ligand AuNPs functionalized with two distinct ligands selected from glucose, arginine-glycine-aspartate (RGD) peptide, and methotrexate (MTX) for tumor theragnosis. The preclinical evaluation demonstrated that tumor uptakes and retention of two components AuNP conjugates were higher than that of single-component AuNP conjugates. Notably, the glucose/MT- modified dual-ligand AuNP conjugates showed significant improvement in tumor uptake and retention. The novel nanoconjugates prepared in this study make it possible to integrate several modalities with a single AuNP for multimodality imaging and therapy, combining the power of chemo-, thermal- and radiation therapies together.

Size-dependent theoretical and experimental photothermal conversion efficiency of spherical gold nanoparticles

INTRODUCTION

Due to their biocompatible and plasmonic properties, gold nanoparticles (Au NPs) are good candidates to be photosensitizers in photothermal cancer therapy (PTT).

MATERIALS AND METHODS

In this paper, the dependence of the NIR-light-to-heat energy on Au NPs size was investigated. Moreover, to determine the photosensitizing properties of gold nanoparticles, PTT was conducted on two colon cell lines: SW480 and SW620 by irradiating them with two lasers having different wavelengths.

RESULTS

Transmission electron microscopy showed that the respective sizes of Au NPs were 10 nm, 12 nm and 16 nm. Moreover, local as well as global structural measurements showed that all synthesized Au NPs were crystalline and UV-Vis spectroscopy revealed that with increasing nanoparticles size the position of the surface Plasmon resonance (SPR) peaks is shifted to higher wavelengths. Decrease of cells viability was observed, when they were cultured with Au NPs and irradiated by 650 nm and 808 nm lasers. Moreover, FTIR and Raman spectra of cells, showed structural changes in DNA, phospholipids, proteins and cholesterol caused by the addition of nanoparticles and laser irradiation. The chemical changes were more pronounced in the cells cultured with Au NPs and irradiated by 650 nm lasers and these changes were dependent on the nanoparticle size. Moreover, the viability of cells investigated by the MTS assay showed, that the percentage of dead cells (∼40%) is the highest for cells cultured with 8 nm Au NPs and irradiated by the 650 nm laser. The photothermal conversion efficiency calculated from the experimental results showed a decrease of this parameter from 70% to 55% and from 61% to 48% with increasing particle size, for 650 nm and 808 nm lasers, respectively.

CONCLUSIONS

The obtained results showed that the photothermal conversion efficiency of Au NPs is size-tunable, and can be correlated with the absorption/extinction ratios calculated by the Mie theory.

Adsorption of bovine serum albumin on gold nanoprisms: interaction and effect of NIR irradiation on protein corona

Because of their photothermal properties, gold nanoparticles (AuNPs) have gained attention regarding their use in drug delivery and therapeutic applications. In this sense, it is interesting to consider their interactions with biologically available proteins, such as serum albumin, as well as the effects of irradiation and photothermal conversion on the protein structure that can lead to a loss of function or generate an immune response. Gold nanoprisms (AuNPrs) have gained interest due to their low toxicity, ease of synthesis, and excellent stability, promoting their use in bioapplications such as surface-enhanced Raman spectroscopy (SERS), drug delivery, and photothermal therapy. The interaction between AuNPrs, with plasmon bands centred in the near-infrared region (NIR), and bovine serum albumin (BSA) has not been explored yet. UV-Vis spectroscopy, dynamic light scattering (DLS) and fluorescence spectroscopy were used to study the interaction between AuNPrs and BSA in addition to estimation of the adsorption rate and kinetic and thermodynamic parameters (K, ΔH°, ΔG°, ΔS°, and Ea) using adsorption isotherms and Langmuir and Freundlich models. The results suggest spontaneous cooperative binding in multilayer adsorption, achieved by the chemisorption of BSA on the AuNPr surface through the S-Au interaction, as confirmed by Raman spectroscopy. On the other hand, the photothermal conversion efficiency (PE) of the coated nanoparticles after NIR irradiation was assessed, resulting in a slight decrease in the PE of BSA coated on AuNPrs in comparison with that of noncapped nanoparticles. The effect of the irradiation on the protein conformation of capped nanoparticles was also assessed; circular dichroism showed BSA unfolding upon interaction with AuNPrs, with a decrease in the α-helix and β-sheet contents, as well as an increase in random coil conformations. Changes in the Raman spectrum suggest a modification of the disposition of the protein residues exposed to the gold surface after NIR irradiation; but at the secondary structure level, no relevant changes were observed. This provides possibilities for the use of NPs-BSA for bioapplications based on the photothermal effect promoted by laser irradiation, since the biological identity of the protein is preserved after NIR irradiation.

A rapid and sensitive fluorescence biosensor based on plasmonic PCR

Plasmonic PCR utilizing metallic nanoparticles has shown great advantages compared to the commercial thermocycler equipment in terms of cost, size and processing time. However, due to the strong fluorescence quenching, plasmonic nanoparticle-based PCR requires additional post-processing steps such as centrifugation and gel electrophoresis. This process increases the overall diagnostic time, offsetting the benefits of fast thermocycling. Here, we report a rapid and sensitive plasmonic photothermal PCR (PPT-PCR) assay method based on in situ end-point fluorescence detection. By using plasmonic magnetic bi-functional nanoparticles, PPT-PCR involving 30 thermocycles and fluorescence detection following magnetic separation has successfully shown that DNA targets can be detected within 5.5 minutes. The limit of detection (3.3 copies per μL) is comparable with that of the conventional real-time quantitative PCR; however, the assay time is about 5.5 times shorter for the PPT-PCR. The strategy of combining the photothermal effect and magnetic separation into a single particle will open new horizons in the development of fast and sensitive PCR-based biosensors for point-of care testing.

Laser-induced optothermal response of gold nanoparticles: From a physical viewpoint to cancer treatment application

Gold nanoparticles (GNPs)-based photothermal therapy (PTT) is a promising minimally invasive thermal therapy for the treatment of focal malignancies. Although GNPs-based PTT has been known for over two decades and GNPs possess unique properties as therapeutic agents, the delivery of a safe and effective therapy is still an open question. This review aims at providing relevant and recent information on the usage of GNPs in combination with the laser to treat cancers, pointing out the practical aspects that bear on the therapy outcome. Emphasis is given to the assessment of the GNPs' properties and the physical mechanisms underlying the laser-induced heat generation in GNPs-loaded tissues. The main techniques available for temperature measurement and the current theoretical simulation approaches predicting the therapeutic outcome are reviewed. Topical challenges in delivering safe thermal dosage are also presented with the aim to discuss the state-of-the-art and the future perspective in the field of GNPs-mediated PTT.

Machine-Free Polymerase Chain Reaction with Triangular Gold and Silver Nanoparticles

Photothermal effects of metal nanoparticles (NPs) are used for various biotechnological applications. Although NPs have been used in a polymerase chain reaction (PCR), the effects of shape on the photothermal properties and its efficiency on PCR are less explored. The present study reports the synthesis of triangular gold and silver NPs, which can attain temperatures up to ∼90 °C upon irradiation with 808 nm laser. This photothermal property of synthesized nanoparticles was evaluated using various concentrations, irradiation time, and power to create a temperature profile required for variable-temperature PCR. This study reports a cost-effective, machine-free PCR using both gold and silver triangular NPs, with efficiency similar to that of a commercial PCR machine. Interestingly, addition of triangular NPs increases PCR efficiency in commercial PCR reactions. The higher PCR efficiencies are due to the direct binding and unfolding of double-stranded DNA as suggested by circular dichroism and UV spectroscopy. These findings suggest that triangular NPs can be used to develop cost-effective, robust machine-free PCR modules and can be used in various other photothermal applications.

Green Synthesis and Characterization of Gold Nanoparticles Using Lignin Nanoparticles

With the development of nanotechnology, gold nanoparticles (Au NPs) have attracted enormous attention due to their special properties. The green synthesis of Au NPs from lignin would inspire the utilization of lignin and its related functional materials. In this study, a rapid preparation process of Au NPs was investigated by utilizing lignin nanoparticles (LNPs) under room temperature without chemical addition. The LNPs acted as a reducing agent, stabilizing agent, and template for the preparation of LNPs@AuNPs. The obtained LNPs@AuNPs were characterized by UV-Vis spectrum, Transmission Electron Microscope (TEM), and X-ray photoelectron spectroscopy (XPS). The possible mechanism was illustrated by Fourier Transform Infrared Spectroscopy (FT-IR), ³¹P, XPS, and UV analyses. The abundant hydroxyl groups (24.96 mmol/g) favored the preparation of Au NPs. Au NPs diameters of 10–30 nm were well dispersed in the LNPs. The optimal reaction conditions were a ratio of 10 mg of LNPs to 0.05 mmol HAuCl₄, room temperature, and a reaction time of 30 min. The LNPs@AuNPs exhibited excellent stability in the suspension for more than seven days. The reduction process could be related to the disruption of side chains of lignin, hydroxyl group oxidation, and hydroquinones and quinones from the comproportionation reaction. The LNPs@AuNPs would open a door for the design of Au NP/lignin-derived novel functional materials.

Self-Assembled Peptide-Based Biocomposites for Near-Infrared Light Triggered Drug Release to Tumor Cells

Peptide-based nanomaterials are increasingly gaining popularity due to their specificity, biocompatibility, and biodegradability. In this work, a new multi-layered peptide-based biocomposite for targeting MCF-7 breast cancer cells is developed. The amphipathic Fluorenylmethyloxycarbonyl (Fmoc)-Leu-Ser peptide is synthesized, which is conjugated to a tumor-targeting peptide sequence Gly-Cys-Gly-Asn-Ser to form Fmoc-L-S-G-C-G-N-S (FLS) assemblies. To the FLS assemblies, gold nanorods are then attached to develop drug delivery vehicles (DDVs). The DDVs are entrapped with the anti-cancer drug fulvestrant. Entrapment efficiency is found to be 50.6%. Release studies indicate that irradiating the gold nanorod bound DDVs at NIR wavelength (785 nm) increases drug release by fourfold compared to assemblies that are not irradiated. These results also show higher cytotoxicity and lower cell invasion due to photo-triggered drug release. Furthermore, distinct actin cytoskeletal changes are observed. Such novel peptide-based gold nanorod bound DDVs demonstrate potential in dual targeting of MCF-7 breast cancer cells.

State of the Art Biocompatible Gold Nanoparticles for Cancer Theragnosis

Research on cancer theragnosis with gold nanoparticles (AuNPs) has rapidly increased, as AuNPs have many useful characteristics for various biomedical applications, such as biocompatibility, tunable optical properties, enhanced permeability and retention (EPR), localized surface plasmon resonance (LSPR), photothermal properties, and surface enhanced Raman scattering (SERS). AuNPs have been widely utilized in cancer theragnosis, including phototherapy and photoimaging, owing to their enhanced solubility, stability, biofunctionality, cancer targetability, and biocompatibility. In this review, specific characteristics and recent modifications of AuNPs over the past decade are discussed, as well as their application in cancer theragnostics and future perspectives. In the future, AuNP-based cancer theragnosis is expected to facilitate the development of innovative and novel strategies for cancer therapy.

Optically controlled hybrid metamaterial of plasmonic spiky gold inbuilt graphene sheets for bimodal imaging guided multimodal therapy

The development of multifunctional molecular diagnostic platforms for the concordant visualization and treatment of diseases with high sensitivity and resolution has recently become a crucial strategy in cancer management. Thus, engineering functional metamaterials with high therapeutic and imaging capabilities to elucidate diseases from their morphological behaviors to physiological mechanisms is an unmet need in the current scenario. Here, we report the design of a unique hybrid plasmonic nanoarchitecture for targeted multiple phototherapies of breast cancer by simultaneous real-time monitoring through fluorescence and surface-enhanced Raman scattering (SERS) techniques. The nanoframework consisted of plasmonic gold-graphene hybrids tethered with folic acid-ligated chitosan-modified photosensitizer (PpIX) to afford target-specific localized photothermal and photodynamic therapy. The hybrid vehicle also served as an excellent nanocarrier for the efficient loading and stimuli-responsive release of the chemotherapeutic drug doxorubicin (DOX) to enhance the therapeutic efficacy, thereby forming a trimodal nanomedicine against cancer. The cytotoxic effects induced by the cumulative action of the triplet therapeutic tools were visualized through both fluorescence and SERS imaging channels. Moreover, it also generated synchronized therapeutic effects resulting in the effective regression of tumor volume without propagating any toxic effects to other organs of the animals. Taken together, by virtue of strong light-matter interactions, the nanoprobe showed enhanced photoadsorption, which facilitated amplified light-reactive therapeutic and imaging efficacies along with targeted and enhanced chemotherapy, both in vitro and in vivo, which may offer promising outcomes in clinical research.

Near-infrared nanosecond-pulsed laser-activated highly efficient intracellular delivery mediated by nano-corrugated mushroom-shaped gold-coated polystyrene nanoparticles

Here, an efficient intracellular delivery of molecules with high cell viability is reported using nanosecond-pulsed laser-activated plasmonic photoporation, mediated by high-aspect-ratio nano-corrugated mushroom-shaped gold-coated polystyrene nanoparticles (nm-AuPNPs) at near-infrared wavelength. Upon pulsed laser illumination, nm-AuPNPs exhibit greater plasmonic extinction than spherical AuPNPs, which increase their energy efficiency and reduce the necessary illumination of light, effectively controlling cell damage and improving the delivery efficiency. Nm-AuPNPs exhibit surface plasmon absorption at near infrared region with a peak at 945 nm. Pulsed laser illumination at this plasmon peak triggers explosive nanobubbles, which create transient membrane pores, allowing the delivery of dyes, quantum dots and plasmids into the different cell types. The results can be tuned by laser fluence, exposure time, molecular size and concentration of nm-AuPNPs. The best results are found for CL1-0 cells, which yielded a 94% intracellular PI dye uptake and ∼100% cell viability at 35 mJ cm-2 laser fluence for 945 nm wavelength. Thus, the presented approach has proven to have an inevitable potential for biological cell research and therapeutic applications.

High Fluence Chromium and Tungsten Bowtie Nano-antennas

Nano-antennas are replicas of antennas that operate at radio-frequencies, but with considerably smaller dimensions when compared with their radio frequency counterparts. Noble metals based nano-antennas have the ability to enhance photoinduced phenomena such as localized electric fields, therefore-they have been used in various applications ranging from optical sensing and imaging to performance improvement of solar cells. However, such nano-structures can be damaged in high power applications such as heat resisted magnetic recording, solar thermo-photovoltaics and nano-scale heat transfer systems. Having a small footprint, nano-antennas cannot handle high fluences (energy density per unit area) and are subject to being damaged at adequately high power (some antennas can handle just a few milliwatts). In addition, given that nano-antennas are passive devices driven by external light sources, the potential damage of the antennas limits their use with high power lasers: this liability can be overcome by employing materials with high melting points such as chromium (Cr) and tungsten (W). In this article, we fabricate chromium and tungsten nano-antennas and demonstrate that they can handle 110 and 300 times higher fluence than that of gold (Au) counterpart, while the electric field enhancement is not significantly reduced.

Plasmonic Photothermal Nanoparticles for Biomedical Applications

Recent advances of plasmonic nanoparticles include fascinating developments in the fields of energy, catalyst chemistry, optics, biotechnology, and medicine. The plasmonic photothermal properties of metallic nanoparticles are of enormous interest in biomedical fields because of their strong and tunable optical response and the capability to manipulate the photothermal effect by an external light source. To date, most biomedical applications using photothermal nanoparticles have focused on photothermal therapy; however, to fully realize the potential of these particles for clinical and other applications, the fundamental properties of photothermal nanoparticles need to be better understood and controlled, and the photothermal effect-based diagnosis, treatment, and theranostics should be thoroughly explored. This Progress Report summarizes recent advances in the understanding and applications of plasmonic photothermal nanoparticles, particularly for sensing, imaging, therapy, and drug delivery, and discusses the future directions of these fields.

Ag and Au nanoparticles/reduced graphene oxide composite materials: Synthesis and application in diagnostics and therapeutics

The exceptional electrical, thermal, optical and mechanical properties have made two dimensional sp² hybridized graphene a material of choice in both academic as well as industrial research. In the last few years, researchers have devoted their efforts towards the development of graphene/polymer, graphene/metal nanoparticle and graphene/ceramic nanocomposites. These materials display excellent mechanical, electrical, thermal, catalytic, magnetic and optical properties which cannot be obtained separately from the individual components. Fascinating physical and chemical properties are displayed by noble metal nanomaterials and thus they represent model building blocks for modifying nanoscale structures for diverse applications extending from catalysis, optics to nanomedicine. Insertion of noble metal (Au, Ag) nanoparticles (NPs) into chemically derived graphene is thus of primary importance to open new avenues for both materials in various fields where the specific properties of each material act synergistically to provide hybrid materials with exceptional performances. This review attempts to summarize the different synthetic procedures for the preparation of Ag and Au NPs/reduced graphene oxide (rGO) composites. The synthesis processes of metal NPs/rGO composites are categorised into in-situ and ex-situ techniques. The in-situ approach consists of simultaneous reduction of metal salts and GO to obtain metal NPs/rGO nanocomposite materials, while in the ex-situ process, the metal NPs of desired size and shape are first synthesized and then transferred onto the GO or rGO matrix. The application of the Ag NPs and Au NPs/rGO composite materials in the area of biomedical (drug delivery and photothermal therapy) and biosensing are the focus of this review article.

Folic acid-conjugated gold nanorod@polypyrrole@Fe3O4 nanocomposites for targeted MR/CT/PA multimodal imaging and chemo-photothermal therapy

Integrating multimodal bioimaging and different therapies into one nanoplatform is a promising strategy for biomedical applications, but remains a great challenge. Herein, we have synthesized a biocompatible folic acid (FA) functionalized gold nanorod@polypyrrole@Fe3O4 (GNR@PPy@Fe3O4-FA) nanocomposite through a facile method. The conjugated FA has endowed the nanocomposite with the ability to recognize targeted cancer cells. Importantly, the nanocomposite has been successfully utilized for magnetic resonance (MR), computed tomography (CT) and photoacoustic (PA) multimodal imaging. Moreover, the GNR@PPy@Fe3O4-DOX nanocomposite shows pH-responsive chemotherapy and enables the integration of photothermal therapy and chemotherapy to achieve superior antitumor efficacy. The GNR@PPy@Fe3O4-DOX nanocomposites have a drug release of 23.64%, and the photothermal efficiency of the GNR@PPy@Fe3O4 nanocomposites reaches 51.46%. Cell viability decreases to 15.83% and 16.47% because of the combination of chemo-photothermal therapy effects. Moreover, the GNR@PPy@Fe3O4-DOX-FA nanocomposite could target cancer cells via folic acid and under a magnetic field. The in vivo multimodal imaging and chemo-photothermal therapy effects showed that the GNR@PPy@Fe3O4-DOX-FA nanocomposites are a good contrast and theranostic agent. Thus, this multifunctional nanocomposite could be a promising theranostic platform for cancer diagnosis and therapy.

Chitosan nanopolymers: An overview of drug delivery against cancer

Cancer is becoming a major reason for death troll worldwide due to the difficulty in finding an efficient, cost effective and target specific method of treatment or diagnosis. The variety of cancer therapy used in the present scenario have painful side effects, low effectiveness and high cost, which are some major drawbacks of the available therapies. Apart from the conventional cancer therapy, nanotechnology has grown extremely towards treating cancer. Nanotechnology is a promising area of science focusing on developing target specific drug delivery system for carrying small or large active molecules to diagnose and treat cancer cells. In the field of nanoscience, Chitosan nanopolymers (ChNPs) are been emerging as a potential carrier due to their biodegradability and biocompatibility. The easy modification and versatility in administration route of ChNPs has attracted attention of researchers towards loading chemicals, proteins and gene drugs for target specific therapy of cancer cells. Therefore, the present review deals with the growing concern towards cancer therapy, introduction of ChNPs, mode of action and other strategies employed by researchers till date towards cancer treatment and diagnosis ChNPs.

Array of disordered silicon nanowires coated by a gold film for combined NIR photothermal treatment of cancer cells and Raman monitoring of the process evolution

Photothermal therapy (PTT) assisted by nanomaterials is a promising minimally invasive technique for cancer treatment. Here, we explore the PTT properties of a silicon- and gold-based nanostructured platform suitable for being directly integrated in fibre laser systems rather than injected into the human body, which occurs for the most commonly unreported PTT nanoagents. In particular, the photothermal properties of an array of disordered silicon nanowires coated by a thin gold film (Au/SiNWs) were tested on a monolayer of human colon adenocarcinoma cells (Caco-2) irradiated with a 785 nm laser. Au/SiNWs allowed an efficient photothermal action and simultaneous monitoring of the process evolution through the Raman signal coming from the irradiated cellular zone. Strong near infra-red (NIR) absorption, overlapping three biological windows, cell-friendly properties and effective fabrication technology make Au/SiNWs suitable both to be integrated in surgical laser tools and as an in vitro platform to develop novel PTT protocols using different cancer types and NIR sources.

Synthesis and Bioevaluation of Iodine-131 Directly Labeled Cyclic RGD-PEGylated Gold Nanorods for Tumor-Targeted Imaging

Introduction

Radiolabeled gold nanoparticles play an important role in biomedical application. The aim of this study was to prepare iodine-131 (¹³¹I)-labeled gold nanorods (GNRs) conjugated with cyclic RGD and evaluate its biological characteristics for targeted imaging of integrin α_vβ₃-expressing tumors.

Methods

HS-PEG₍₅₀₀₀₎-COOH molecules were applied to replace CTAB covering the surface of bare GNRs for better biocompatibility, and c(RGDfK) peptides were conjugated onto the carboxyl terminal of GNR-PEG-COOH via EDC/NHS coupling reactions. The nanoconjugate was characterized, and ¹³¹I was directly tagged on the surface of GNRs via AuI bonds for SPECT/CT imaging. We preliminarily studied the characteristics of the probe and its feasibility for tumor-targeting SPECT/CT imaging.

Results

The [¹³¹I]GNR-PEG-cRGD probe was prepared in a simple and rapid manner and was stable in both PBS and fetal bovine serum. It targeted selectively and could be taken up by tumor cells mainly via integrin α_vβ₃-receptor-mediated endocytosis. In vivo imaging, biodistribution, and autoradiography results showed evident tumor uptake in integrin α_vβ₃-expressing tumors.

Conclusions

These promising results showed that this smart nanoprobe can be used for angiogenesis-targeted SPECT/CT imaging. Furthermore, the nanoprobe possesses a remarkable capacity for highly efficient photothermal conversion in the near-infrared region, suggesting its potential as a multifunctional theranostic agent.

Gold nanorod reshaping in vitro and in vivo using a continuous wave laser

Gold nanorods (GNRs) are increasingly being investigated for cancer theranostics as they possess features which lend themselves in equal measures as contrast agents and catalysts for photothermal therapy. Their optical absorption spectral peak wavelength is determined by their size and shape. Photothermal therapy using GNRs is typically established using near infrared light as this allows sufficient penetration into the tumour matrix. Continuous wave (CW) lasers are the most commonly applied source of near infrared irradiation on GNRs for tumour photothermal therapy. It is perceived that large tumours may require fractionated or prolonged irradiation. However the true efficacy of repeated or protracted CW irradiation on tumour sites using the original sample of GNRs remains unclear. In this study spectroscopy and transmission electron microscopy are used to demonstrate that GNRs reshape both in vitro and in vivo after CW irradiation, which reduces their absorption efficiency. These changes were sustained throughout and beyond the initial period of irradiation, resulting from a spectral blue-shift and a considerable diminution in the absorption peak of GNRs. Solid subcutaneous tumours in immunodeficient BALB/c mice were subjected to GNRs and analysed with electron microscopy pre- and post-CW laser irradiation. This phenomenon of thermally induced GNR reshaping can occur at relatively low bulk temperatures, well below the bulk melting point of gold. Photoacoustic monitoring of GNR reshaping is also evaluated as a potential clinical aid to determine GNR absorption and reshaping during photothermal therapy. Aggregation of particles was coincidentally observed following CW irradiation, which would further diminish the subsequent optical absorption capacity of irradiated GNRs. It is thus established that sequential or prolonged applications of CW laser will not confer any additional photothermal effect on tumours due to significant attenuations in the peak optical absorption properties of GNRs following primary laser irradiation.

Hollow Au-Cu Nanocomposite for Real-Time Tracing Photothermal/Antiangiogenic Therapy

High absorption in the near-infrared (NIR) region is essential for a photoabsorbing agents to realize efficient photothermal therapy (PTT) for cancer. Here, a novel hollow Au-Cu nanocomposite (HGCNs) is developed, which displays a significantly enhanced NIR surface plasmon resonance absorption and photothermal transduction efficiency. Besides, fluorescent polymer dots poly(9,9-dioctylfluorene-2,7-diyl-co-benzothiadiazole) (PFBT) and chemotherapeutic mammalian target of rapamycin (mTOR) inhibitor agent rapamycin (RAPA) are attached onto the HGCNs (RAPA/PFBT-HGCNs) for real-time NIR fluorescence tracing and combined PTT/antiangiogenesis therapy. In particular, due to the fluorescence resonance energy transfer effect, RAPA/PFBT-HGCNs can act as NIR-activatable on/off probe system for real-time tracing of tumor tissues. A standard in vitro cellular uptake study, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, dual-staining study, and flow cytometry assay reveal that the RAPA/PFBT-HGCNs combined with NIR laser exhibit higher drug accumulation and cytotoxicity in both tumor cells and epithelial cells. Moreover, the margins of tumor and normal tissue can be accurately indicated by NIR-stimulated dequenched PFBT after 24 h intravenous administration. Further, tumor growth can be considerably hampered by the optimal formulation plus laser treatment with relatively lower side effects. Consequently, the work highlights the real-time tracing and enhanced PTT/antiangiogenesis therapy prospects of the established HGCNs with tremendous potential for treatment of cancer.

Multicomponent, Tumor-Homing Chitosan Nanoparticles for Cancer Imaging and Therapy

Current clinical methods for cancer diagnosis and therapy have limitations, although survival periods are increasing as medical technologies develop. In most cancer cases, patient survival is closely related to cancer stage. Late-stage cancer after metastasis is very challenging to cure because current surgical removal of cancer is not precise enough and significantly affects bystander normal tissues. Moreover, the subsequent chemotherapy and radiation therapy affect not only malignant tumors, but also healthy tissues. Nanotechnologies for cancer treatment have the clear objective of solving these issues. Nanoparticles have been developed to more accurately differentiate early-stage malignant tumors and to treat only the tumors while dramatically minimizing side effects. In this review, we focus on recent chitosan-based nanoparticles developed with the goal of accurate cancer imaging and effective treatment. Regarding imaging applications, we review optical and magnetic resonance cancer imaging in particular. Regarding cancer treatments, we review various therapeutic methods that use chitosan-based nanoparticles, including chemo-, gene, photothermal, photodynamic and magnetic therapies.

In Situ Visualization of the Local Photothermal Effect Produced on α-Cyclodextrin Inclusion Compound Associated with Gold Nanoparticles

Evidence of guest migration in α-cyclodextrin-octylamine (α-CD-OA) inclusion compound (IC) generated via plasmonic heating of gold nanoparticles (AuNPs) has been studied. In this report, we demonstrate local effects generated by laser-mediated irradiation of a sample of AuNPs covered with inclusion compounds on surface-derivatized glass under liquid conditions by atomic force microscopy (AFM). Functionalized AuNPs on the glass and covered by the ICs were monitored by recording images by AFM during 5 h of irradiation, and images showed that after irradiation, a drastic decrease in the height of the AuNPs occurred. The absorption spectrum of the irradiated sample showed a hypsochromic shift from 542 to 536 nm, evidence suggesting that much of the population of nanoparticles lost all of the parts of the overlay of ICs due to the plasmonic heat generated by the irradiation. Mass spectrometry matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) performed on a sample containing a collection of drops obtained from the surface of the functionalized glass provided evidence that the irradiation lead to disintegration of the ICs and therefore exit of the octylamine molecule (the guest) from the cyclodextrin cavity (the matrix). Graphical Abstract Atomic Force Microscopy observation of the disintegration of a cyclodextrin inclusion compound by gold nanoparticles photothermal effect.

An Intermittent Model for Intracellular Motions of Gold Nanostars by k-Space Scattering Image Correlation

Anisotropic metallic nanoparticles have been devised as powerful potential tools for in vivo imaging, photothermal therapy, and drug delivery thanks to plasmon-enhanced absorption and scattering cross sections, ease in synthesis and functionalization, and controlled cytotoxicity. The rational design of all these applications requires the characterization of the nanoparticles intracellular trafficking pathways. In this work, we exploit live-cell time-lapse confocal reflectance microscopy and image correlation in both direct and reciprocal space to investigate the intracellular transport of branched gold nanostars (GNSs). Different transport mechanisms, spanning from pure Brownian diffusion to (sub-)ballistic superdiffusion, are revealed by temporal and spatio-temporal image correlation spectroscopy on the tens-of-seconds timescale. According to these findings, combined with numerical simulations and with a Bayesian (hidden Markov model-based) analysis of single particle tracking data, we ascribe the superdiffusive, subballistic behavior characterizing the GNSs dynamics to a two-state switching between Brownian diffusion in the cytoplasm and molecular motor-mediated active transport. For the investigation of intermittent-type transport phenomena, we derive an analytical theoretical framework for Fourier-space image correlation spectroscopy (kICS). At first, we evaluate the influence of all the dynamic and kinetic parameters (the diffusion coefficient, the drift velocity, and the transition rates between the diffusive and the active transport regimes) on simulated kICS correlation functions. Then we outline a protocol for data analysis and employ it to derive whole-cell maps for each parameter underlying the GNSs intracellular dynamics. Capable of identifying even simpler transport phenomena, whether purely diffusive or ballistic, our intermittent kICS approach allows an exhaustive investigation of the dynamics of GNSs and biological macromolecules.

Self-assisted optothermal trapping of gold nanorods under two-photon excitation

We report a self-assisted optothermal trapping and patterning of gold nanorods (GNRs) on glass surfaces with a femtosecond laser. We show that GNRs are not only the trapping targets, but also can enhance the optothermal trapping of other particles. This trapping phenomenon is the net result of thermophoresis and a convective flow caused by localized heating. The heating is due to the conversion of absorbed photons into heat at GNR's longitudinal surface plasmon resonance (LSPR) wavelength. First, we investigated the optothermal trapping of GNRs at their LSPR wavelength on the glass surface with as low as 0.5 mW laser power. The trapping range was observed to be larger than a typical field of view, e.g. 210 µm  ×  210 µm here. Second, by adjusting the distance between the laser focus and the glass surface, ring patterns of GNRs on the glass surface were obtained. These patterns could be controlled by the laser power and the numerical aperture of the microscope objective. Moreover, we examined the spectral emission of GNRs under different trapping conditions using the spectral phasor approach to reveal the temperature and association status of GNRs. Our study will help understanding manipulation of flows in solution and in biological systems that can be applied in future investigations of GNR-induced heating and flows.

Fabrication of Graphene and AuNP Core Polyaniline Shell Nanocomposites as Multifunctional Theranostic Platforms for SERS Real-time Monitoring and Chemo-photothermal Therapy

In this work, novel theranostic platforms based on graphene oxide and AuNP core polyaniline shell (GO-Au@PANI) nanocomposites are fabricated for simultaneous SERS imaging and chemo-photothermal therapy. PANI, a new NIR photothermal therapy agent with strong NIR absorption, outstanding stability and low cytotoxicity is decorated on AuNPs by one-pot oxidative polymerization, then the Au@PANI core-shell nanoparticles are attached to the graphene oxide (GO) sheet via π-π stacking and electrostatic interaction. The obtained GO-Au@PANI nanohybirds exhibit excellent NIR photothermal transduction efficiency and ultrahigh drug-loading capacity. The nanocomposites can also serve as novel NIR SERS probes utilizing the intense SERS signals of PANI. Rapid SERS imaging of cancer cells is achieved using this ultrasensitive nanoprobe. GO-Au@PANI also reveals good capability of drug delivery with the DOX-loading efficiency of 189.2% and sensitive NIR/pH-responsive DOX release. The intracellular real-time drug release dynamics from the nanocomposites is monitored by SERS-fluorescence dual mode imaging. Finally, chemo-photothermal ablation of cancer cells is carried out in vitro and in vivo using GO-Au@PANI as high-performance chemo-photothermal therapeutic nanoagent. The theranostic applications of GO-Au@PANI endow it with great potential for personalized and precise cancer medicine.

Ultrasensitive solution-processed broad-band photodetectors using CH₃NH₃PbI₃ perovskite hybrids and PbS quantum dots as light harvesters

Sensing from ultraviolet-visible to infrared is critical for both scientific and industrial applications. In this work, we demonstrate solution-processed ultrasensitive broad-band photodetectors (PDs) utilizing organolead halide perovskite materials (CH3NH3PbI3) and PbS quantum dots (QDs) as light harvesters. Through passivating the structural defects on the surface of PbS QDs with diminutive molecular-scaled CH3NH3PbI3, both trap states in the bandgap of PbS QDs for charge carrier recombination and the leakage currents occurring at the defect sites are significantly reduced. In addition, CH3NH3PbI3 itself is an excellent light harvester in photovoltaics, which contributes a great photoresponse in the ultraviolet-visible region. Consequently, operated at room temperature, the resultant PDs show a spectral response from 375 nm to 1100 nm, with high responsivities over 300 mA W(-1) and 130 mA W(-1), high detectivities exceeding 10(13) Jones (1 Jones = 1 cm Hz(1/2) W(-1)) and 5 × 10(12) Jones in the visible and near infrared regions, respectively. These device performance parameters are comparable to those from pristine inorganic counterparts. Thus, our results offer a facile and promising route for advancing the performance of broad-band PDs.

Color and texture morphing with colloids on multilayered surfaces

Dynamic morphing of marine species to match with environment changes in color and texture is an advanced means for surviving, self-defense, and reproduction. Here we use colloids that are placed inside a multilayered structure to demonstrate color and texture morphing. The multilayer is composed of a thermal insulating base layer, a light absorbing mid layer, and a liquid top layer. When external light of moderate intensity (∼0.2 W cm(-2)) strikes the structure, colloids inside the liquid layer will be assembled to locations with an optimal absorption. When this system is exposed to continuous laser pulses, more than 18,000 times of reversible responses are recorded, where the system requests 20 ms to start the response and another 160 ms to complete. The flexibility of our concept further allows the system to be built on a variety of light-absorbing substrates, including dyed paper, gold thin film, and amorphous silicon, with the top layer even a solid.

Spectral properties and dynamics of gold nanorods revealed by EMCCD-based spectral phasor method

Gold nanorods (NRs) with tunable plasmon-resonant absorption in the near-infrared region have considerable advantages over organic fluorophores as imaging agents due to their brightness and lack of photobleaching. However, the luminescence spectral properties of NRs have not been fully characterized at the single particle level due to lack of proper analytic tools. Here, we present a spectral phasor analysis method that allows investigations of NRs' spectra at single particle level showing the spectral variance and providing spatial information during imaging. The broad phasor distribution obtained by the spectral phasor analysis indicates that spectra of NRs are different from particle to particle. NRs with different spectra can be identified in images with high spectral resolution. The spectral behaviors of NRs under different imaging conditions, for example, different excitation powers and wavelengths, were revealed by our laser-scanning multiphoton microscope using a high-resolution spectrograph with imaging capability. Our results prove that the spectral phasor method is an easy and efficient tool in hyper-spectral imaging analysis to unravel subtle changes of the emission spectrum. We applied this method to study the spectral dynamics of NRs during direct optical trapping and by optothermal trapping. Interestingly, different spectral shifts were observed in both trapping phenomena.

A single multifunctional nanoplatform based on upconversion luminescence and gold nanorods

Lanthanide-doped upconverting nanoparticles (UCNPs), which convert near-infrared (NIR) light to higher energy light have been intensively studied for theranostic applications. Here, we developed a hybrid core/shell nanocomposite with multifunctional properties using a multistep strategy consisting of a gold nanorod (GNR) core with an upconverting NaYF4:Er3+, Yb3+ shell (GNR@NaYF4:Er3+, Yb3+). To use a single excitation beam, the GNR plasmon was tuned to ∼650 nm, which is resonant with the upconverted red Er3+ emission emanating from the 4F9/2 excited state. Thus, under laser irradiation at 980 nm, the intensity ratio of the upconverted green emission (arising from the 2H11/2 and 4S3/2 excited states of Er3+) showed a remarkable thermal sensitivity, which was used to calculate the temperature change due to rapid heat conversion from the GNR core. The red upconversion emission of the GNR@NaYF4:Er3+, Yb3+ core/shell nanocomposite decreased compared with the NaYF4:Er3+, Yb3+ nanoshell structure (without a GNR core), which indicates that energy transfer from NaYF4:Er3+, Yb3+ to the GNR takes place, subsequently causing a photothermal effect. The anticancer drug, doxorubicin, was loaded into the GNR@NaYF4:Er3+, Yb3+ nanocomposites and the drug release profile was evaluated. In particular, the release of doxorubicin was significantly enhanced at lower pH and higher temperature caused by the photothermal effect. This multifunctional nanocomposite, which is suitable for local heating and controlled drug release, shows strong potential for use in cancer therapy.

Citrate-stabilized gold nanorods

Stable aqueous dispersions of citrate-stabilized gold nanorods (cit-GNRs) have been prepared in scalable fashion by surfactant exchange from cetyltrimethylammonium bromide (CTAB)-stabilized GNRs, using polystyrenesulfonate (PSS) as a detergent. The surfactant exchange process was monitored by infrared spectroscopy, surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopy (XPS). The latter established the quantitative displacement of CTAB (by PSS) and of PSS (by citrate). The Cit-GNRs are indefinitely stable at low ionic strength, and are conducive to further ligand exchange without loss of dispersion stability. The reliability of the surface exchange process supports the systematic analysis of ligand structure on the hydrodynamic size of GNRs, as described in a companion paper.

Nanoparticles for photothermal therapies

The current status of the use of nanoparticles for photothermal treatments is reviewed in detail. The different families of heating nanoparticles are described paying special attention to the physical mechanisms at the root of the light-to-heat conversion processes. The heating efficiencies and spectral working ranges are listed and compared. The most important results obtained in both in vivo and in vitro nanoparticle assisted photothermal treatments are summarized. The advantages and disadvantages of the different heating nanoparticles are discussed.

Advances in noninvasive functional imaging of bone

The demand for functional imaging in clinical medicine is comprehensive. Although the gold standard for the functional imaging of human bones in clinical settings is still radionuclide-based imaging modalities, nonionizing noninvasive imaging technology in small animals has greatly advanced in recent decades, especially the diffuse optical imaging to which Britton Chance made tremendous contributions. The evolution of imaging probes, instruments, and computation has facilitated exploration in the complicated biomedical research field by allowing longitudinal observation of molecular events in live cells and animals. These research-imaging tools are being used for clinical applications in various specialties, such as oncology, neuroscience, and dermatology. The Bone, a deeply located mineralized tissue, presents a challenge for noninvasive functional imaging in humans. Using nanoparticles (NP) with multiple favorable properties as bioimaging probes has provided orthopedics an opportunity to benefit from these noninvasive bone-imaging techniques. This review highlights the historical evolution of radionuclide-based imaging, computed tomography, positron emission tomography, and magnetic resonance imaging, diffuse optics-enabled in vivo technologies, vibrational spectroscopic imaging, and a greater potential for using NPs for biomedical imaging.

Gold nanoparticles and gold nanoparticle-conjugates for delivery of therapeutic molecules. Progress and challenges

Gold nanoparticles and their conjugates as drug delivery vehicles for selective targeting of cancer cells.

Au nanostructure-decorated TiO2 nanowires exhibiting photoactivity across entire UV-visible region for photoelectrochemical water splitting

Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV-visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV-visible light for solar fuel production.

Low power upconverted near-IR light for efficient polymeric nanoparticle degradation and cargo release

By encapsulating NaYF4 :Tm.Yb upconverting nanocrystals in UV-degradable polymer capsules, it is possible to access efficient polymer photodegradation and remotely controlled release using near-IR laser light at an unprecedentedly low power.

The conjugates of gold nanorods and chlorin e6 for enhancing the fluorescence detection and photodynamic therapy of cancers

Gold nanorods (AuNRs) were conjugated with chlorin e6 (Ce6), a commonly used photosensitizer, to form AuNRs-Ce6 by electrostatic binding. Due to the strong surface plasmon resonance coupling, the fluorescence of conjugated Ce6 was enhanced 3-fold and the production of singlet oxygen was increased 1.4-fold. AuNRs-Ce6 were taken up by the HeLa and KB cell lines more easily than free Ce6, enhancing the intracellular delivery of Ce6. The increased cellular amount of Ce6 leads to a 3-fold more efficient photodynamic killing of these two cell lines. This demonstrates the potential of this approach to improve photodynamic detection and therapy of cancers.

Gold nanorod-facilitated localized heating of droplets in microfluidic chips

A gold nanorod-facilitated optical heating method for droplets in microfluidic chips is reported. Individual and stream nanoliter level droplets containing gold nanorods are heated by a low power 808-nm-wavelength laser. Owing to the high photothermal conversion efficiency of gold nanorods, a droplet temperature of 95 °C is achieved by employing a 13.6 mW laser with good reproducibility. The heating and cooling times are 200 and 800 ms, respectively, which are attributed to the fast thermal-transfer rates of the droplets. By controlling the irradiation laser power, the temperature cycles for polymerase chain reaction are also demonstrated.