Photothermal Effect Of Gold Nanorods Research Articles

Real-Time Monitoring of a Single Molecule in Sub-nanometer Space by Dynamic Surface-Enhanced Raman Spectroscopy.

In biology and chemistry, the ultimate goal is to monitor single molecules without labels. However, long-term monitoring of label-free molecules remains a challenge. Here, on the basis of the photothermal effect of gold nanorods (GNRs), we developed a platform for monitoring of a single molecule employing surface-enhanced Raman spectroscopy (SERS). Laser re-irradiation forms 1.0 nm gaps between GNRs, allowing us to observe single crystal violet (CV) molecules blinking for up to 4 min with dynamic surface-enhanced Raman spectroscopy (D-SERS). Bianalyte experiments confirm single-molecule features at CV concentrations of 10-14 M. Combining density functional theory (DFT) calculations with a free CV molecule observed in millisecond D-SERS, we propose that CV molecules can be confined to sub-nanometer space and the orientation of an individual CV moving in the range of 50-90° can be dynamically captured by D-SERS. This will provide a novel idea for effective exploration of the temporal and spatial dynamic processes of different reactions.

Photothermal effects of gold nanorods in aqueous solution and gel media: Influence of particle size and excitation wavelength.

Gold nanorods (GNRs) have emerged as the most efficient photothermal agent in cancer therapy and photocatalysis. Understanding the influence of the surrounding medium, particle size, and excitation wavelength is critical to optimising the photothermal conversion rate. Here, three pairs of large and small gold nanorods of different aspect ratios and their heat generation under laser radiation at on and off surface plasmon resonance wavelengths in aqueous solution and gel-like media are investigated. In the aqueous solution, the temperature rise of the large gold nanorods is more than with small gold nanorods at resonance excitation. In contrast to the large gold nanorods (LGNRs), the small gold nanorods (SGNRs) were less sensitive to excitation wavelength. At off-resonance excitation, the temperature rise of the SGNRs is larger than that of the LGNRs. In the agarose gel, the photothermal effect of the SGNRs is greater than LGNRs excited at the wavelength near their solution phase longitudinal surface plasmon resonance wavelength. The temperature increase of LGNRs in gel is significantly less than in aqueous solution. These findings suggest that SGNRs could be more beneficial than the LGNRs for photothermal applications in biological systems and provides further insight when selecting GNRs.

Photothermal effect of albumin-modified gold nanorods diminished neuroblastoma cancer stem cells dynamic growth by modulating autophagy

Here, we investigated the photothermal effect of gold nanorods (GNRs) on human neuroblastoma CD133+ cancer stem cells (CSCs) via autophagic cell death. GNRs were synthesized using Cetyltrimethylammonium bromide (CTAB), covered with bovine serum albumin (BSA). CD133+ CSCs were enriched from human neuroblastoma using the magnetic-activated cell sorting (MACS) technique. Cells were incubated with GNRs coated with BSA and exposed to 808-nm near-infrared laser irradiation for 8 min to yield low (43 °C), medium (46 °C), and high (49 °C) temperatures. After 24 h, the survival rate and the percent of apoptotic and necrotic CSCs were measured using MTT assay and flow cytometry. The expression of different autophagy-related genes was measured using polymerase chain reaction (PCR) array analysis. Protein levels of P62 and LC3 were detected using an enzyme-linked immunosorbent assay (ELISA). The viability of CSC was reduced in GNR-exposed cells compared to the control group (p < 0.05). At higher temperatures (49 °C), the percent of apoptotic CSCs, but not necrotic cells, increased compared to the lower temperatures. Levels of intracellular LC3 and P62 were reduced and increased respectively when the temperature increased to 49 °C (p < 0.05). These effects were non-significant at low and medium temperatures (43 and 46 °C) related to the control CSCs (p > 0.05). The clonogenic capacity of CSC was also inhibited after photothermal therapy (p < 0.05). Despite these changes, no statistically significant differences were found in terms of CSC colony number at different temperatures regardless of the presence or absence of HCQ. Based on the data, the combination of photothermal therapy with HCQ at 49 °C can significantly abort the CSC clonogenic capacity compared to the control-matched group without HCQ (p < 0.0001). PCR array showed photothermal modulation of CSCs led to alteration of autophagy-related genes and promotion of co-regulator of apoptosis and autophagy signaling pathways. Factors related to autophagic vacuole formation and intracellular transport were significantly induced at a temperature of 49 °C (p < 0.05). We also note the expression of common genes belonging to autophagy and apoptosis signaling pathways at higher temperatures. Data showed tumoricidal effects of laser-irradiated GNRs by the alteration of autophagic response and apoptosis.

Theoretical and experimental investigations on the photo-thermal effect of gold nanorods irradiated by femtosecond and nanosecond laser

Nanoparticle mediated laser induced breakdown can be used for Nanoparticle synthesis, cell nanosurgery and laser induced breakdown spectroscopy. To investigate the photo-thermal conversion of gold nanoparticles during pulsed laser irradiation, the electron-phonon two temperature model was established in this study. The impact of laser energy density and pulse width on the thermal conversion and morphology change of gold nanorods were investigated and compared with experimental observations. The results show that the melting threshold of gold nanorods under nanosecond laser irradiation is about twenty times that of femtosecond laser irradiation. The mechanisms of nanorod fragmentation are different between femto and nanosecond laser irradiation: particle melting is more likely to occur in nanosecond laser irradiation, while the Coulomb explosion is highly likely to occur in femtosecond laser irradiation.

Plasmonic photothermal biosensor for visual detection of tyrosinase and dopamine based on manganese dioxide nanosheets-mediated etching of gold nanorods

As a crucial enzyme involved in melanogenesis, tyrosinase plays an important role in the diagnosis of melanoma. Herein, a novel and simple photothermal quantitative method based on manganese dioxide nanosheets-mediated etching of gold nanorods was established for tyrosinase activity assay with a simple household thermometer as the readout. Gold nanorods were etched by manganese dioxide nanosheets in acid condition at room temperature with a fast and stable etching efficiency. With the etching of gold nanorods, the photothermal conversion efficiency decreased gradually with the change of the aspect ratio of gold nanorods, leading to the decrease of the temperature increment of the solution by degrees. The gold nanorods have an unparalleled photothermal conversion efficiency, and the increment of temperature caused by the photothermal effect of gold nanorods has a span as wide as nearly 17 °C within one minute of laser irradiation. A household thermometer, instead of a spectrometer or any other professional and costly instruments, was used as a signal reader to achieve the visual quantitative detection, which makes this method possible for point-of-care testing. The photothermal platform was used successfully for the determination of tyrosinase and its substrate dopamine with wider linear ranges from 1.0 to 70 U/mL and 2.0–150 μM and detection limits as low as 0.34 U/mL and 0.92 μM, respectively. Moreover, the inhibition efficiency of kojic acid on tyrosinase activity was investigated, proving the photothermal quantitative method will be a potential platform for screening inhibitors of tyrosinase.

Assembly of gold nanorods with L-cysteine reduced graphene oxide for highly efficient NIR-triggered photothermal therapy

Near-infrared (NIR) photothermal therapy is an effective partner to the chemotherapy of tumors with the merits of high therapeutic ability and slight side effect on normal tissues. Herein, we synthesized gold nanorods and assembled them with L-cysteine reduced graphene oxide (AuNR@Lcyst-rGO) for efficient photothermal therapy. The high therapeutic efficacy of AuNR@Lcyst-rGO can be due to the high photothermal effect of gold nanorods and reduced graphene oxide, and the synergistic effect of them. The nontoxicity of L-cysteine also guarantees the comfortable biocompatibility of reduced graphene oxide, which is essential for the photothermal absorber used in human tissue. The results demonstrate that assembly of gold nanorods with reduced graphene oxide (AuNR@Lcyst-rGO) is a promising photothermal agent with high efficient NIR-triggered photothermal therapy efficiency, excellent stability, superior biocompatibility.

Magnetic Testis Targeting and Magnetic Hyperthermia for Noninvasive, Controllable Male Contraception via Intravenous Administration

Mild testicular hyperthermia by the photothermal effect of gold nanorods could realize controllable male contraception. However, associated limitations, such as testicular administration and infrared laser inflicting severe pain, and the nondegradability of nanoparticles potentially causing toxicity, have restricted further clinical application. Inspired by the excellent physicochemical properties of iron oxide nanoparticles (IONPs), and the finding that testicular injection of PEG-coated IONPs with a diameter of 50 nm (PEG@Fe3O4-50) following an alternating magnetic field (AMF) could achieve controllable male contraception; here we propose a noninvasive, targeting approach for male contraception via intravenous administration. The magnetic properties and testes targeting of IONPs were proven to be greatly affected by their surface chemistry and particle size. After systemic administration, citric acid stabilized IONPs with size of 100 nm (CA@Fe3O4-100) were found to be the best ideal thermoagent for realizing the noninvasive contraception. This study offers new strategies for male contraception.

Quantitative gold nanorods based photothermal biosensor for glucose using a thermometer as readout

To meet the increasing need for point-of-care testing (POCT), simple and portable readout strategies would be highly desirable. Thermometer with high accuracy and straightforward readout is an ideal tool for the development of new POCT methods. The exploration of new thermometer-based detection methods is of great significance. In this study, a simple biosensor for glucose based on the photothermal effect of gold nanorods using a simple thermometer as readout has been developed. In the presence of glucose oxidase, glucose can react with the dissolved oxygen to produce H2O2. With the help of Fe2+, H2O2 can etch gold nanorods (AuNRs) to different aspect ratios. The decrease of the aspect ratio of AuNRs leads to the blue-shift of the localized surface plasmon resonance peak, resulting in a decrease of photothermal effect in the near-infrared regions and the temperature of the system decreased. The change of the temperature has a linear relationship with the logarithm of glucose concentration in the range of 1.0–10.0 mM with a detection limit of 0.8 mM. The proposed method possesses a bias offset of −0.03 mM for glucose detection compared to the hospital method. Since many enzymatic reactions can produce H2O2, the principle can be modified to detect different targets by simply change of the enzyme used.

Controlled Synthesis and Surface Engineering of Janus Chitosan‐Gold Nanoparticles for Photoacoustic Imaging‐Guided Synergistic Gene/Photothermal Therapy

The unsymmetrical morphology and unique properties of Janus nanoparticles (JNPs) provide superior performances for biomedical applications. In this work, a general and facile strategy is developed to construct a series of symmetrical and unsymmetrical chitosan/gold nanoparticles. Taking advantage of the active motion derived from Janus structure, selective surface functionalization of polysaccharide domain, and photothermal effect of gold nanorods, Janus chitosan/gold nanoparticles (J-Au-CS) are selected as a model system to construct Janus-structured chitosan/gold nanohybrids (J-ACP). Near-infrared (NIR)-responsive J-ACP composed of polycationic chitosan nanospheres and PEGylated gold nanorods hold great potential to realize photoacoustic (PA) imaging-guided complementary photothermal therapy (PTT)/gene therapy for breast cancer. The morphology effect of chitosan/gold nanostructures on enhanced PTT, cellular uptake, and gene transfection is investigated. The feasibility of PA imaging to track the accumulation of J-ACP and guide PTT is also explored. Notably, synergistic therapy is achieved based on PTT-enhanced gene therapy. In addition, the loading function of chitosan/gold nanoparticles for fluorescence imaging is demonstrated. The current work extends the application of JNPs for imaging-guided synergistic cancer therapy and provides flexible candidates with distinct structures for diverse biomedical applications.

Theoretical and Experimental Investigations on Photothermal Effect of Gold Nanorods Irradiated by Femtosecond or Nanosecond Laser

Theoretical and Experimental Investigations on Photothermal Effect of Gold Nanorods Irradiated by Femtosecond or Nanosecond Laser

Aptamer-based selective KB cell killing by the photothermal effect of gold nanorods

Development of both specific receptors against target cancer cells and therapeutic tools using receptor-functionalized nanoplatforms are important in cancer treatment. To address these challenges, we developed KB cell–specific aptamers using systematic evolution of ligands by exponential enrichment (SELEX). Additionally, we combined the targeting properties of aptamers and photothermal characteristics of GNRs. As a result, we generated efficient aptamer-gold nanorods (Apt-GNRs) targeting KB cancer cells and exhibiting photothermal therapeutic effects. When the samples were irradiated with a light-emitting diode at 845 nm, the targeted KB cells showed ~ 80% cell death compared with the unirradiated and aptamer-free control. Based on the low toxicity, biocompatibility, and selectivity of Apt-GNRs, the proposed nanoplatform has significant potential as a cancer therapy in vivo.

Development of Direct-Laser-Printable Light-Powered Nanocomposites.

Four-dimensional (4D) printable light-powered materials have emerged as a new generation of materials for the development of functional devices. The design of these types of materials is mostly based on the trans-cis transformation of azobenzene moieties in a liquid crystalline elastomer (LCE) matrix, in which the motion is triggered by ultraviolet (UV) irradiation. In this paper, we first report on a direct laser printable photoresist for producing light-powered 4D structures with enhanced mechanical properties and near-infrared (NIR) responsive mechanical deformation. The reported nanocomposite design is based on the photothermal effects of gold nanorods (AuNRs), which can induce the nematic-to-isotropic transition of LCE upon exposure to NIR irradiation. The miscibility between AuNRs and LCE is enhanced by thiol functionalization. Appropriate printing parameters are determined, and nanocomposites containing 0-3 wt % of AuNR loading are fabricated via femtosecond two-photon direct laser writing. The effects of the AuNR loading fraction and laser power on the light-powered actuating performance are evaluated. It is found that the nanocomposite with AuNR loading of 3 wt % demonstrates the maximum percentage (20%) of elongation under an NIR laser power of 2 W. An increase in laser power can lead to faster deformation but slower restoration. The nanocomposites demonstrate relatively good stability. Even after 300 actuation cycles, 80% of the elongation magnitude can be retained. In addition, an improvement of 80% in the complex modulus of the nanocomposites, due to the inclusion of AuNRs, is observed.

Mesoporous Manganese Dioxide Coated Gold Nanorods as a Multiresponsive Nanoplatform for Drug Delivery

Nanomaterials can offer a chance to integrate many excellent physical and chemical performances into a single carrier for smart responsive drug delivery. Herein, gold nanorods/mesoporous manganese dioxide (Au/MnO2) hybrid nanoparticles were prepared to combine the photothermal effect of gold nanorods (AuNRs) with glutathione (GSH)-responsive and pH-responsive performances of MnO2. The near-infrared (NIR) responsive constituent of a Au/MnO2 nanoparticle was AuNRs. Doxorubicin hydrochloride (DOX), a widely used anticancer drug, was loaded into the Au/MnO2 hybrid nanoparticle via electrostatic force, hydrogen bonding, and physical absorption with a drug loading up to 99.1%. The results revealed that the mesoporous MnO2 was degraded in the media with high concentrations of GSH and acid microenvironment. The Au/MnO2 nanoparticles displayed satisfying drug release kinetics (ca. 47% of loaded drug released in 12 h) and showed excellent GSH-responsive, pH-responsive, and NIR-responsive performances. This multires...

A Biomimetic Non-Antibiotic Approach to Eradicate Drug-Resistant Infections.

The chronic infections by pathogenic Pseudomonas aeruginosa (P. aeruginosa) remain to be properly addressed. In particular, for drug-resistant strains, limited medication is available. An in vivo pneumonia model induced by a clinically isolated aminoglycoside resistant strain of P. aeruginosa is developed. Tobramycin clinically treating P. aeruginosa infections is found to be ineffective to inhibit or eliminate this drug-resistant strain. Here, a newly developed non-antibiotics based nanoformulation plus near-infrared (NIR) photothermal treatment shows a remarkable antibacterial efficacy in treating this drug-resistant pneumonia. The novel formulation contains 50-100 nm long nanorods decorated with two types of glycomimetic polymers to specifically block bacterial LecA and LecB lectins, respectively, which are essential for bacterial biofilm development. Such a 3D display of heteromultivalent glycomimetics on a large scale is inspired by the natural strengthening mechanism for the carbohydrate-lectin interaction that occurs when bacteria initially infects the host. This novel formulation shows the most efficient bacteria inhabitation and killing against P. aeruginosa infection, through lectin blocking and the near-infrared-light-induced photothermal effect of gold nanorods, respectively. Collectively, the novel biomimetic design combined with the photothermal killing capability is expected to be an alternative treatment strategy against the ever-threatening drug-resistant infectious diseases when known antibiotics have failed.

Effects of gold nanorods modified with antiepidermal growth factor receptor monoclonal antibody on laryngeal cancer cells.

We aimed to evaluate the photothermal effects of gold nanorods (GNRs) modified with antiepidermal growth factor receptor (EGFR) monoclonal antibody (mAb) on laryngeal cancer cells. EGFR protein expressions in HEP-2 cells, and normal laryngeal epithelial and laryngeal cancer tissues were detected by western blot. The cytotoxicity against HEP-2 and BEAS-2B cells was tested by MTT assay, and the photothermal effects were assessed by near-infrared (NIR) irradiation. The apoptosis of HEP-2 cells was detected by flow cytometry. EGFR expression in laryngeal cancer tissues was significantly higher than that in normal tissues (P < 0.05). The inhibitory effects of GNRs and anti-EGFR mAb/GNRs on the apoptosis of HEP-2 and BEAS-2B cells were enhanced with increasing dose. AntiEGFR mAb/GNRs were more cytotoxic to HEP-2 cells and less cytotoxic to BEAS-2B cells than GNRs. NIR irradiation inhibited cell proliferation, which was enhanced with rising power, accompanied by continuously dropping survival rate. The apoptosis rate of the anti-EGFR mAb/GNRs group was significantly higher than that of the GNRs group, and the apoptosis rate of the irradiation + antiEGFR mAb/GNRs group also significantly exceeded that of the irradiation + GNRs group (P < 0.05). Anti-EGFR mAb/GNRs promoted HEP-2 cell apoptosis more evidently than GNRs did. Functional modification of GNRs augmented the targeted specificity to cancer cells, biocompatibility, and stability. Anti-EGFR mAb/GNRs have great potential in biomedical fields.

Near-infrared-light-responsive liquid-crystalline composite gels with photo-healing ability

ABSTRACTWe developed photo-healable composite gels consisting of liquid crystal, microparticles, and gold nanorods. Upon irradiation with near-infrared light, the temperature of the composite gels rapidly increased above a gel-sol transition temperature by the photothermal effect of gold nanorods. Then, we successfully performed photoinduced gel-sol transition of composite gels based on the phase transition of liquid crystals induced by the photothermal effect. In addition, we achieved photo-healing of surface cracks made on the composite gels by means of the photothermal gel-sol transition.

Comparison of ovalbumin and ovalbumin epitope peptide for transdermal delivery and vaccination mediated by the photothermal effect of gold nanorods

Transdermal protein delivery is a powerful and attractive method for protein therapy and dermal vaccination compared with other administrations. However, this delivery method is restricted by the low permeability of the stratum corneum (SC), a hydrophobic barrier that restricts the entry of hydrophilic molecules such as proteins. In this study, we developed an improved gel patch system carrying ovalbumin and ovalbumin epitope peptide, and then compared their permeability into the skin. First, the gel patch was placed on mouse skin to allow contact with the polymer coated gold nanorods and then irradiated by a continuous-wave laser. Thermal ablation of the SC improved the permeability and translocation of ovalbumin and the peptide. Fluorescence images showed the translocation was enhanced when the skin was treated with the FITC-modified ovalbumin epitope peptide. However, induction of anti-OVA IgG production after treatment with the FITC-modified ovalbumin epitope peptide was lower than that with FITC-OVA.

Injectable, NIR/pH-Responsive Nanocomposite Hydrogel as Long-Acting Implant for Chemophotothermal Synergistic Cancer Therapy.

In this study, gold nanorods (GNRs) were incorporated into the hydrogel networks formed by the copolymerization of N-isopropylacrylamide (NIPAm) and methacrylated poly-β-cyclodextrin (MPCD)-based macromer to fabricate an injectable and near-infrared (NIR)/pH-responsive poly(NIPAm-co-MPCD)/GNRs nanocomposite hydrogel, which could serve as a long-acting implant for chemophotothermal synergistic cancer therapy. The nanocomposite hydrogel showed superior mechanical and swelling properties, gelation characteristics, and excellent NIR-responsive property. A hydrophobic acid-labile adamantane-modified doxorubicin (AD-DOX) prodrug was loaded into the hydrogel efficiently by host-guest interaction. The nanocomposite hydrogel exhibited a manner of sustained drug release and could sustain the slow and steady release of DOX for more than 1 month. The pH-responsive release of DOX from the nanocomposite hydrogel was observed owing to the cleavage of acid-labile hydrazone bond between DOX and the adamantyl group in acidic environment. NIR irradiation could accelerate the release of DOX from the networks, which was controlled by the collapse of the hydrogel networks induced by photothermal effect of GNRs. The in vitro cytotoxicity test demonstrated the excellent biocompatibility and photothermal effect of the nanocomposite hydrogel. Moreover, the in situ-forming hydrogel showed promising tissue biocompatibility in the mouse model study. The in vivo antitumor test demonstrated the capacity of the nanocomposite hydrogel for chemophotothermal synergistic therapy with reduced adverse effects owing to the prolonged drug retention in the tumor region and efficient photothermal effect. Therefore, this injectable and NIR/pH-responsive nanocomposite hydrogel exhibited great potential as a long term drug delivery platform for chemophotothermal synergistic cancer therapy.

Enhancement of transdermal protein delivery by photothermal effect of gold nanorods coated on polysaccharide-based hydrogel.

Transdermal protein delivery is a useful and attractive method for protein therapy and dermal vaccination. However, this delivery method is restricted by the low permeability of the stratum corneum. The purpose of this study was to develop a transdermal delivery system for enhancement of protein permeability into the skin. First, we prepared a transparent gel patch made of polysaccharides with gold nanorods on the gel surface and fluorescein isothiocyanate-modified ovalbumin (FITC-OVA) inside. Next, the gel patch was placed on mouse skin to allow contact with the coated gold nanorods, and irradiated by a continuous-wave laser. The laser irradiation heated the gold nanorods and the skin temperature increased to 43°C, resulting in enhanced translocation of FITC-OVA into the skin. These results confirmed the capability of the transdermal protein delivery system to perforate the stratum corneum and thus facilitate the passage of proteins across the skin.

Photothermal activation of astrocyte cells using localized surface plasmon resonance of gold nanorods.

Although it has been revealed that astrocytes, generally known as star-shaped glial cells, play critical roles in the functions of central nervous system, there have been few efforts to directly modulate their activities and responses. In this study, an optical stimulation strategy for producing intracellular Ca2+ transients of astrocytes is demonstrated using near-infrared (NIR) light and localized surface plasmon resonance. It is presented that NIR stimulation of micro-second duration combined with gold nanorods (GNRs) efficiently produces stronger Ca2+ transients of astrocytes, which seems to be associated with a local heat generation by photothermal effects of GNRs. Since the proposed scheme can directly activate astrocytes with a high reliability, it is expected that GNR-mediated NIR stimulation could be utilized to facilitate minimally invasive physiological studies on the astrocyte functions. Photos of intracellular Ca2+ transient of astrocytes with membrane-bound GNRs after optical stimulation at 30 s.