Fluorescent Contrast Agents Research Articles

Pluronic stabilized conjugated polymer nanoparticles for NIR fluorescence imaging and dual phototherapy applications

• Pluronic stabilized conjugated polymer nanoparticles (CP-NP-Plu) are prepared. • CP-NP-Plu present photothermal conversion efficiency of 61% under NIR irradiation. • 2-fold increase of singlet oxygen generation quantum yield due to encapsulation with Plu • NIR fluorescence imaging ability validated at single nanoparticle level. Besides their intensive application as solar photovoltaic materials, low bandgap conjugated polymers have been recently exploited in cell imaging and phototherapeutic applications due to their photoactivity in the near-infrared (NIR) spectral domain, also known as the “biologically transparent window”. Herein, Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole) (PCPDTBT) conjugated polymer was used to prepare novel NIR activatable theranostic nanoparticles, via nanoprecipitation method, for fluorescence imaging and dual photothermal-photodynamic therapy (PTT-PDT) applications. To overcome the drawback of hydrophobicity of PCPDTBT, the approach of encapsulating the obtained nanoparticles with a layer of Pluronic F127 amphiphilic block co-polymer was herein applied. The Pluronic layer not only provides excellent colloidal stability, but also ensures enhanced fluorescence emission, improved photothermal heating and singlet oxygen generation ability of the nanoparticles in aqueous dispersion. Specifically, upon irradiation with a NIR laser at 785 nm, the obtained nanoparticles exhibit good thermal response and excellent photostability leading to a photothermal conversion efficiency of 61%. Moreover, a near two-fold increase in the singlet oxygen generation quantum yield due to encapsulation with Pluronic is also detected. Furthermore, fluorescence imaging measurements on single nanoparticle immobilized on glass substrate reveal their potential as fluorescence contrast agents. The enhanced fluorescence and improved therapeutic properties of our nanoparticles suggest the possibility to be employed as NIR activatable theranostic agents via dual phototherapy combined with high-resolution fluorescence tracking.

A narrative review of indocyanine green near-infrared fluorescence imaging technique: a new application in thoracic surgery

: In clinical work of thoracic surgery, accurate anatomic location of pulmonary nodules, precise demarcation of segmental and sub-segmental plane, tracing of sentinel lymph nodes (SLNs), protection of thoracic nerve, averting of anastomotic fistula etc. always puzzling the surgeons. Indocyanine green (ICG) is a near-infrared fluorescence (NIRF) contrast agent that is the only reagent approved by the Food and Drug Administration (FDA) for use in human subjects due to its low toxicity and high absorbance in the near-infrared spectrum. The application of ICG NIRF imaging technology in surgery is safe and feasible, it can offer real-time fluorescing information and help surgeons make important decisions during surgery. Many studies demonstrated that ICG NIRF can be used to determine tissue perfusion, lymphatic reflux and other fields. In recent years, it has been reported in the field of thoracic surgery and got success. It can provide more information compared to conventional video-assisted thoracoscopic surgery (VATS). In this review, the research results of this technique in animal models and clinical trials in recent years are reviewed the application of ICG NIRF technique in accurate positioning of pulmonary nodules, precise demarcation of segmental and sub-segmental plane, SLNs tracing, thoracic nerve protection, anastomotic leakage and chylothorax prevention.

A preliminary study on the application of paramagnetic composite nanoparticles in the navigation of hepatectomy

As the preferred treatment strategy for primary liver cancer, hepatic resection surgery can effectively improve the survival of liver cancer patients without relying on other treatments. However, traditional hepatic resection surgery cannot achieve precise localization of the cancer foci boundary. Therefore, improving hepatectomy targeting and reducing the metabolic rate of contrast agents in vivo has become an urgent challenge. This study constructed a novel indocyanine green nanocomposite fluorescent contrast agent, known as indocyanine green-carboxymethyl chitosan/superparamagnetic iron oxide nanoparticle (ICG-CMCS/SIO NP), based on a superparamagnetic iron oxide. The carboxymethyl chitosan and indocyanine green (ICG)’s graft copolymer served as a nanomaterial shell. This shell enhanced ICG targeting’s control ability and stability while effectively retaining its core magnetic properties. Thus, ICG-CMCS/SIO NPs should provide a novel idea for the study of clinical hepatocellular carcinoma resection surgery navigation.

Dual Fluorescence Emission by Irradiation of Single Optical Source for Fluorescein Sodium and 5-ALA Applications

Abstract Most brain surgeries aim to completely resection a tumor. However, the arrangement of blood vessels around brain tumors is often complex. Moreover, the tumors and blood vessels have similar colors, making it difficult to identify the boundaries between them with the naked eye. Fluorescent staining is a method used to distinguish the borders between brain tumors and blood vessels. The fluorescent contrast agents commonly used to observe tumors are 5-aminolevulinic acid and fluorescein sodium, which have different surgical sensitivities, depending on the type of tumor. In this article, a dual band bandpass filter with dual-wavelength emission for 5-aminolevulinic acid and fluorescein sodium is designed, and the dual-band bandpass filter capable of inducing simultaneous fluorescence emission of fluorescein sodium and 5-aminolevulinic acid was investigated experimentally to improve accuracy, speed, and energy efficiency in clinical settings. The possibility of dual fluorescence emission with a single irradiation is proposed. The efficiency of transmission and reflection (optical density) is 98% and 0.01%, respectively, and the bandwidth is 50% in the proposed filter. The proposed fluorescent dual-band filter has the advantage of saving energy, reducing auxiliary manpower and unit costs, and reducing operating room space requirements by producing two fluorescence diagnostic effects using a single equipment.

Combined PARP1-Targeted Nuclear Contrast and Reflectance Contrast Enhance Confocal Microscopic Detection of Basal Cell Carcinoma.

Reflectance confocal microscopy (RCM) with endogenous backscattered contrast can noninvasively image basal cell carcinomas (BCCs) in skin. However, BCCs present with high nuclear density, and the relatively weak backscattering from nuclei imposes a fundamental limit on contrast, detectability, and diagnostic accuracy. We investigated PARPi-FL, an exogenous nuclear poly(adenosine diphosphate ribose) polymerase (PARP1)-targeted fluorescent contrast agent, and fluorescence confocal microscopy toward improving BCC diagnosis. Methods: We tested PARP1 expression in 95 BCC tissues using immunohistochemistry, followed by PARPi-FL staining in 32 fresh surgical BCC specimens. The diagnostic accuracy of PARPi-FL contrast was evaluated in 83 surgical specimens. The optimal parameters for permeability of PARPi-FL through intact skin was tested ex vivo on 5 human skin specimens and invivo in 3 adult Yorkshire pigs. Results: We found significantly higher PARP1 expression and PARPi-FL binding in BCCs than in normal skin structures. Blinded reading of RCM-and-fluorescence confocal microscopy images by 2 experts demonstrated a higher diagnostic accuracy for BCCs with combined fluorescence and reflectance contrast than for RCM alone. Optimal parameters (time and concentration) for PARPi-FL transepidermal permeation through intact skin were successfully determined. Conclusion: Combined fluorescence and reflectance contrast may improve noninvasive BCC diagnosis with confocal microscopy.

Carbocyanine dye-patterned microbubbles as ultrasound-modulated fluorescent contrast agents

Combining fluorescence and acoustic techniques enables the characterization of biochemical environments with optical sensors while utilizing the penetration depth and spatial resolution of focused ultrasound. Localized light generation within a small tissue volume can yield spatially resolved chemical information useful for delineating tissue pathology such as cancerous lesions. Our work develops fluorescent microbubble contrast agents that generate light in the focal zone of an ultrasound beam through modulation of their fluorescence intensity. Microbubbles were designed with a self-quenching lipophilic dye patterned within the lipid layer, enabling the dye molecules to quench and dequench with the ultrasound-driven particle size oscillations. Distinct dye patterns were generated on the microbubble surfaces and investigated for their ultrasound-driven fluorescence response. By amplifying the microbubble fluorescence intensity modulations using a lock-in amplifier, the optical signal from these locally activated particles was detected within an optically scattering environment and at significant depth. We additionally observed that these microbubbles also displayed harmonic oscillations of fluorescence intensity beyond the ultrasound driving frequency which could be used to further improve the signal-to-noise ratio for detection. This technique could enable sensitive optical imaging with ultrasound-scale millimeter-level spatial resolution, providing a valuable tool to address the challenge of optical imaging in deep tissue.

Preparation Fe3O4@chitosan-graphene quantum dots nanocomposites for fluorescence and magnetic resonance imaging

The recent development of nanoprobes with multiple biomolecular detection functionalities have attracted considerable interests in various biomedical imaging applications. Herein, we have designed and prepared Fe3O4@chitosan-graphene quantum dots (Fe3O4@CS-GQDs) nanocomposites for fluorescence and magnetic resonance imaging (MRI). The photoluminescent spectra of Fe3O4@CS-GQDs nanocomposites exhibit an emission peak at 434 nm under the ultraviolet excitation light of 330 nm. Fe3O4@CS-GQD nanocomposites show the excellent MRI results in aqueous solution. The cytotoxicity of Fe3O4@CS-GQDs nanocomposites is observed low cytotoxicity in Hela cells. Based on the results, Fe3O4@CS-GQDs nanocomposites are confirmed as promising fluorescence and MRI imaging contrast agents for tumor detection.

Design of a Long-Pass Filter with Effects on Fluorescence Image Observation for Surgical Fluorescence Microscope Applications

The goal of oncological surgery is to completely remove the tumor. Tumors are often difficult to observe with the naked eye because of the presence of numerous blood vessels and the fact the colors of the tumor and blood vessels are similar. Therefore, a fluorescent contrast medium using a surgical microscope is used to observe the removal status of the tumor. To observe the tumor removal status using a fluorescent contrast agent, fluorescence is expressed in the tumor by irradiating with an external light source, and the expressed tumor can be confirmed through a surgical microscope. However, not only fluorescence-expressed tumors are observed under a surgical microscope, but images from an external light source are also mixed and observed. Therefore, since the surgical microscope is connected to a filter, the quality of the diagnostic image is not uniform, and it is difficult to achieve a clear observation. As a result, an asymmetric image quality phenomenon occurs in the diagnostic images. In this paper, a filter with high clarity that provides a symmetrical observation of diagnostic images is developed and manufactured.

Organic Anion Transporting Polypeptide 1B1 Is a Potential Reporter for Dual MR and Optical Imaging

Membrane proteins responsible for transporting magnetic resonance (MR) and fluorescent contrast agents are of particular importance because they are potential reporter proteins in noninvasive molecular imaging. Gadobenate dimeglumine (Gd-BOPTA), a liver-specific MR contrast agent, has been used globally for more than 10 years. However, the corresponding molecular transportation mechanism has not been validated. We previously reported that the organic anion transporting polypeptide (OATP) 1B3 has an uptake capability for both MR agents (Gd-EOB-DTPA) and indocyanine green (ICG), a clinically available near-infrared (NIR) fluorescent dye. This study further evaluated OATP1B1, another polypeptide of the OATP family, to determine its reporter capability. In the OATP1B1 transfected 293T transient expression model, both Gd-BOPTA and Gd-EOB-DTPA uptake were confirmed through 1.5 T MR imaging. In the constant OAPT1B1 and OATP1B3 expression model in the HT-1080 cell line, both HT-1080-OAPT1B1 and HT-1080-OATP1B3 were observed to ingest Gd-BOPTA and Gd-EOB-DTPA. Lastly, we validated the ICG uptake capability of both OATP1B1 and OATP1B3. OAPT1B3 exhibited a superior ICG uptake capability to that of OAPT1B1. We conclude that OATP1B1 is a potential reporter for dual MR and NIR fluorescent molecular imaging, especially in conjunction with Gd-BOPTA.

Thrombus-specific theranostic nanocomposite for codelivery of thrombolytic drug, algae-derived anticoagulant and NIR fluorescent contrast agent

Thrombolysis is a standard treatment for rapidly restoring blood flow. However, the application of urokinase-type plasminogen activator (Uk) in clinical therapy is limited due to its nonspecific distribution and inadequate therapeutic accumulation. Precise thrombus imaging and site-specific drug delivery can enhance the diagnostic and therapeutic efficacy for thrombosis. Accordingly, we developed a P-selectin-specific, photothermal theranostic nanocomposite for thrombus-targeted codelivery of Uk and indocyanine green (ICG, a contrast agent for near-infrared (NIR) fluorescence imaging). We evaluated its capabilities for thrombus imaging and enzyme/hyperthermia combined thrombolytic therapy. Mesoporous silica-coated gold nanorods (Si-AuNRs) were functionalized with an arginine-rich peptide to create an organic template for the adsorption of ICG and fucoidan (Fu), an algae-derived anticoagulant. Uk was loaded into the SiO2 pores of the Si-AuNRs through the formation of a Fu-Uk-ICG complex on the peptide-functionalized template. The Fu-Uk/ICG@SiAu NRs nanocomposite increased the photostability of ICG and improved its targeting/accumulation at blood clot sites with a strong NIR fluorescence intensity for precise thrombus imaging. Furthermore, ICG incorporated into the nanocomposite enhanced the photothermal effect of Si-AuNRs. Fu, as a P-selectin-targeting ligand, enabled the nanocomposite to target a thrombus site where platelets were activated. The nanocomposite enabled a faster release of Uk for rapid clearing of blood clots and a slower release of Fu for longer lasting prevention of thrombosis regeneration. The nanocomposite with multiple functions, including thrombus-targeting drug delivery, photothermal thrombolysis, and NIR fluorescence imaging, is thus an advanced theranostic platform for thrombolytic therapy with reduced hemorrhaging risk and enhanced imaging/thrombolysis efficiency. Statement of significanceHerein, for the first time, a P-selectin specific, photothermal theranostic nanocomposite for thrombus-targeted co-delivery of urokinase and NIR fluorescence contrast agent indocyanine green (ICG) was developed. We evaluated the potential of this theranostic nanocomposite for thrombus imaging and enzyme/hyperthermia combined thrombolytic therapy. The nanocomposite showed multiple functions including thrombus targeting and imaging, and photothermal thrombolysis. Besides, it allowed faster release of the thrombolytic urokinase for rapidly clearing blood clots and slower release of a brown algae-derived anticoagulant fucoidan (also acting as a P-selectin ligand) for prevention of thrombosis regeneration. The nanocomposite is thus a new and advanced theranostic platform for targeted thrombolytic therapy.

Rapid, non-invasive measurement of gastric emptying rate using transcutaneous fluorescence spectroscopy.

Gastric emptying rate (GER) signifies the rate at which the stomach empties following ingestion of a meal and is relevant to a wide range of clinical conditions. GER also represents a rate limiting step in small intestinal absorption and so is widely assessed for research purposes. Despite the clinical and physiological importance of gastric emptying, methods used to measure GER possess a series of limitations (including being invasive, slow or unsuitable for certain patient populations). Here, we present a new technique based on transcutaneous (through-the-skin) fluorescence spectroscopy that is fast, non-invasive, and does not require the collection of samples or laboratory-based analysis. Thus, this approach has the potential to allow immediate reporting of clinical results. Using this new method, participants receive an oral dose of a fluorescent contrast agent and a wearable probe detects the uptake of the agent from the gut into the blood stream. Analysis of the resulting data then permits the calculation of GER. We compared our spectroscopic technique to the paracetamol absorption test (a clinically approved GER test) in a clinical study of 20 participants. Results demonstrated good agreement between the two approaches and, hence, the clear potential of transcutaneous fluorescence spectroscopy for clinical assessment of GER.

Defect-Rich La2O3 Nanoparticles with Antioxidant Activity for Human Keratinocytes

A deficiency in the human antioxidant system to scavenge free radicals results in mounting oxidative stress, causing various pathological conditions including immune system constraints. To support an underperforming antioxidant system and regulate homeostatic function, efficient and biocompatible reactive oxygen species (ROS) scavengers may be employed. At present, metal oxide-based antioxidants nanoparticles are of fundamental interest because of their smart surface property tailoring. A spray precipitation method was employed in this work to develop a strained and defect rich lanthanum oxide (La2O3) nanostructure. A contraction in d-spacing and distortion in planes and vacancies were observed in the nanostructure, causing microstrain as verified by the William-Hall uniform deformation model (UDM). Photocatalytic activity was evaluated against commercial La2O3 and Evonik Aeroxide TiO2 P25 via dye degradation experiments. A 30% degradation reduction confirmed the ability of the nanostructure to scavenge free radicals generated by P25 upon ultraviolet (UV) irradiation. Compared to the commercial La2O3, the nanostructured La2O3 showed an increase in UV absorption (200–400) nm due to a decrease in the optical band gap. A positive surface charge of the nanoparticles was observed from zeta potential measurements, suggesting sufficient colloidal stability. In vitro toxicity studies toward the nonmalignant human keratinocyte cell line (HaCaT) over a 24 h treatment period with the La2O3 nanoparticles exhibited no toxicity in comparison with the control and ZnO nanoparticles. The antioxidant properties of the nanoparticles were investigated by a dichlorofluorescein (DCF)-based assay which revealed a decrease in intracellular ROS in comparison with N-acetylcysteine (NAC) and H2O2. In addition, confocal microscopy imaging showed the internalization of the nanoparticles and subsequent DCF intensity change between the treated and untreated cells, as supported by flow cytometry analysis. Our findings suggest that defect-rich La2O3 nanoparticles could be used effectively as active inorganic UV filter and fluorescent contrast agent owing to their biocompatible antioxidant properties.

Necrosis binding of Ac-Lys0(IRDye800CW)-Tyr3-octreotate: a consequence from cyanine-labeling of small molecules

BackgroundThere is a growing body of nuclear contrast agents that are repurposed for fluorescence-guided surgery. New contrast agents are obtained by substituting the radioactive tag with, or adding a fluorescent cyanine to the molecular structure of antibodies or peptides. This enables intra-operative fluorescent detection of cancerous tissue, leading to more complete tumor resection. However, these fluorescent cyanines can have a remarkable influence on pharmacokinetics and tumor uptake, especially when labeled to smaller targeting vectors such as peptides. Here we demonstrate the effect of cyanine-mediated dead cell-binding of Ac-Lys0(IRDye800CW)-Tyr3-octreotate (800CW-TATE) and how this can be used as an advantage for fluorescence-guided surgery.ResultsBinding of 800CW-TATE could be blocked with DOTA0-Tyr3-octreotate (DOTA-TATE) on cultured SSTR2-positive U2OS cells and was absent in SSTR2 negative U2OS cells. However, strong binding was observed to dead cells, which could not be blocked with DOTA-TATE and was also present in dead SSTR2 negative cells. No SSTR2-mediated binding was observed in frozen tumor sections, possibly due to disruption of the cells in the process of sectioning the tissue before exposure to the contrast agent. DOTA-TATE blocking resulted in an incomplete reduction of 61.5 ± 5.8% fluorescence uptake by NCI-H69-tumors in mice. Near-infrared imaging and dead cell staining on paraffin sections from resected tumors revealed that fluorescence uptake persisted in necrotic regions upon blocking with DOTA-TATE.ConclusionThis study shows that labeling peptides with cyanines can result in dead cell binding. This does not hamper the ultimate purpose of fluorescence-guided surgery, as necrotic tissue appears in most solid tumors. Hence, the necrosis binding can increase the overall tumor uptake. Moreover, necrotic tissue should be removed as much as possible: it cannot be salvaged, causes inflammation, and is tumorigenic. However, when performing binding experiments to cells with disrupted membrane integrity, which is routinely done with nuclear probes, this dead cell-binding can resemble non-specific binding. This study will benefit the development of fluorescent contrast agents.

A method for validating depth-resolved biodistributions in topically-stained specimen with multi-channel fluorescence cryo-imaging.

Fluorescent contrast agents targeted to cancer biomarkers are increasingly being explored for cancer detection, surgical guidance, and response monitoring. Efforts have been underway to topically apply such biomarker-targeted agents to freshly excised specimen for detecting cancer cell receptors on the surface as a method for intraoperative surgical margin assessment, including dual-probe staining methods introduce a second 'non-specific' optical agent as a control to help compensate for heterogeneous uptake and normalize the imaging field. Still, such specimen staining protocols introduce multifaceted complexity with unknown variables, such as tissue-specific diffusion, cell-specific binding and disassociation rates, and other factors, affecting the interpreted cancer-biomarker distribution across the specimen surface. The ability to recover three-dimensional dual-probe biodistributions throughout whole-specimens could offer a ground-truth validation method for examining topical staining uptake behaviors. Herein, we report on a novel method for characterizing dual-probe accumulation with 3D depth-profiles observed from a dual-probe fresh-specimen staining experiment.

Development of biotin-tagged near-infrared fluorescence probes for tumor-specific imaging

Near-infrared (NIR) probes are applicable for tumor imaging due to deep tissue penetration and low background signal. And cyanine dyes with long emission wavelength are excellent fluorophores to develop NIR probes. However, the aggregation of cyanine dyes in aqueous solution reduces the utilization of light. To solve this problem, polyethylene glycol (PEG) was introduced into the probes to reduce their aggregation. In our work, two new NIR probes G1 and G2 were designed and prepared by conjugating the cyanine dye G0 with Biotin-PEG5-Azide. The conjugated biotin could enhance the target specificity of probes. And the photophysical and photochemical parameters demonstrated that G1 and G2 had a reduced aggregation tendency. In vitro fluorescence imaging proved that these two probes could be specifically taken up by HeLa cells, and in vivo imaging demonstrated that these two probes could specifically target tumors with large tumor-to-muscle (T/M) ratios. All these results indicated that G1 and G2 are promising NIR fluorescent contrast agents for tumor-specific imaging.

Tumor imaging of a novel Ho3+-based biocompatible NIR fluorescent fluoride nanoparticle

Cancer has become the leading cause of death for its high incidence and mortality. Early diagnosis and treatment are essential for the inhibition of tumor growth. In this work, A biocompatible, nontoxic, near-infrared fluorescent tumor targeting nanoparticle KHLF(K5HoLi2F10) was prepared by a delicate method for the early diagnosis of tumor. The surface functionalization of the nanoparticle endows it with good water solubility and biocompatibility. Covalent binding to folic acid provides it with the ability to target HeLa cells. After modification, this nanoparticle can still maintain high fluorescence intensity and it can be detected in 2 cm thick pork tissue. We carried out biodistribution imaging, organs imaging and tumor targeting imaging experiments to characterize its imaging ability in vivo. The results show that this nanoparticle could accurately accumulate in HeLa tumor and generate significant fluorescence signal, which confirms the nanoparticle has great potential as a efficient biocompatible fluorescent contrast agent for tumor diagnosis.

Tuning the Baird Aromatic Triplet State Energy of Cyclooctatetraene to Maximize the Self-Healing Mechanism in Organic Fluorophores

Bright, photostable and non-toxic fluorescent contrast agents are critical for biological imaging. ‘Self-healing’ dyes, in which triplet states are intramolecularly quenched, enable fluorescence imaging by increasing fluorophore brightness and longevity, while simultaneously reducing the generation of reactive oxygen species that promote phototoxicity. Here, we systematically examine the self-healing mechanism in cyanine-class organic fluorophores spanning the visible spectrum. We show that the Baird aromatic triplet state energy of cyclooctatetraene can be physically altered to achieve order of magnitude enhancements in fluorophore brightness and signal-to-noise ratio both in the presence and absence of oxygen. We leverage these advances to achieve direct measurements of large-scale conformational dynamics within single molecules at sub-millisecond resolution using wide-field illumination and camera-based detection methods. These findings demonstrate the capacity to image functionally relevant conformational processes in biological systems in the kilohertz regime at physiological oxygen concentrations and shed important light on the multivariate parameters critical to self-healing organic fluorophore design (Pati et al., PNAS, 2020).

Far-Red to Near Infrared Emissive Aqueous Nanoparticles Based on a New Organic Material with Three BODIPY Dyes at the Periphery of the Core: A Combined Experimental and Theoretical Study

A new organic material with three 4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene dyes (BODIPYs) at the periphery of the central core is successfully synthesized (3BDP3T) and its corresponding aqueous nanoparticles are prepared via the encapsulation approach and characterized in detail both experimentally and theoretically with the aid of the Density Functional Theory (DFT). The linear and non-linear optical properties of the synthesized material are also studied. Until now, the development of organic materials with three BODIPYs as substituents is limited and their properties are not fully resolved. The obtained 3BDP3T-based nanoparticles exhibit far-red and near infrared (NIR) emission with photoluminescence quantum yields of 0.021, which is promising as a new fluorescent contrast agent in the far-red and NIR spectral regions.

Polymer encapsulated clinical ICG nanoparticles for enhanced photothermal therapy and NIR fluorescence imaging in cervical cancer.

Photothermal therapy (PTT) is a popular tumor therapy method, which is based on efficient photothermal nanoagents (PTNs). Clinical Indocyanine Green (ICG), as a Food and Drug Administration (FDA) approved agent, is an often-used PTN, meanwhile it is also a good near-infrared (NIR) fluorescence contrast agent. However, the further applications of ICG in biomedical fields are limited due to its poor stability. In this study, ICG was encapsulated by the amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA) to form ICG@PSMA nanoparticles. Furthermore, optical and thermal characteristics of ICG@PSMA nanoparticles were studied in detail. Strong NIR fluorescence and excellent photothermal properties of ICG@PSMA nanoparticles under 808 nm laser irradiation were measured. Besides, favorable biocompatibility of ICG@PSMA nanoparticles was demonstrated on a human cervical cancer cell line (HeLa) via cell viability studies. Hence, ICG@PSMA nanoparticles were further applied to enhanced PTT of living HeLa cells under 808 nm excitation, and a high PTT efficiency of ∼70% was obtained. The novel ICG nanoparticles as a promising PTT nanoplatform could offer an opportunity for further tumour treatments.

Near-infrared emitting gold-silver nanoclusters with large Stokes shifts for two-photon in vivo imaging.

Near-infrared emitting bi-metallic gold/silver nanoclusters with large Stokes shifts were manufactured through one-pot synthesis. The gold/silver nanoclusters exhibit strong NIR fluorescence due to the silver effect, which can be applied as a two-photon fluorescent contrast agent for in vivo bioimaging.