Nano-sized Indocyanine Green J-aggregate as a One-component Theranostic Agent

Tailoring Indocyanine Green J-Aggregates for Imaging, Cancer Phototherapy, and Drug Delivery: A Review

Indocyanine green J-aggregates (ICG-Jagg) have emerged as a significant subject of interest in biomedical applications due to their unique optical properties, tunable size, and excellent biocompatibility. This comprehensive review aims to provide an in-depth exploration of ICG-Jagg, with a focus on elucidating the diverse facets of their preparation and the factors that influence the preparation process. Additionally, the review discusses their applications in biomedical diagnostics, such as imaging and contrast agents, as well as their utilization in drug delivery and various phototherapeutic interventions.

Indocyanine green J-aggregate (IJA) theranostics: Challenges and opportunities

Indocyanine green is an FDA-approved fluorescent imaging dye used for determining cardiac output, hepatic function, liver blood flow, and retinal perfusion. It has been investigated preclinically in photoacoustic imaging and photothermal therapy (PTT); however, ICG photodegradation limits its biomedical applications. An aggregated form of ICG, known as J-aggregate (IJA), exhibits superior photoacoustic signals and thermal stability than the monomeric ICG. Nevertheless, IJA still suffers from low stability in the biological milieu, and short in vivo blood circulation. To address these limitations, a range of nanocarriers have been developed to enhance IJA stability and performance. This review focuses on IJA potentials and limitations, besides the recent development of IJA-loaded nanocarriers, particularly for cancer imaging and therapy.

Potential applications for photoacoustic imaging using functional nanoparticles: A comprehensive overview

This paper presents a comprehensive overview of the potential applications for Photo-Acoustic (PA) imaging employing functional nanoparticles. The exploration begins with an introduction to nanotechnology and nanomaterials, highlighting the advancements in these fields and their crucial role in shaping the future. A detailed discussion of the various types of nanomaterials and their functional properties sets the stage for a thorough examination of the fundamentals of the PA effect. This includes a thorough chronological review of advancements, experimental methodologies, and the intricacies of the source and detection of PA signals. The utilization of amplitude and frequency modulation, design of PA cells, pressure sensor-based signal detection, and quantification methods are explored in-depth, along with additional mechanisms induced by PA signals. The paper then delves into the versatile applications of photoacoustic imaging facilitated by functional nanomaterials. It investigates the influence of nanomaterial shape, size variation, and the role of composition, alloys, and hybrid materials in harnessing the potential of PA imaging. The paper culminates with an insightful discussion on the future scope of this field, focusing specifically on the potential applications of photoacoustic (PA) effect in the domain of biomedical imaging and nanomedicine. Finally, by providing the comprehensive overview, the current work provides a valuable resource underscoring the transformative potential of PA imaging technique in biomedical research and clinical practice.

A supramolecular colloidal system based on folate-conjugated β-cyclodextrin polymer and indocyanine green for enhanced tumor-targeted cell imaging in 2D culture and 3D tumor spheroids

Indocyanine green (ICG) is an FDA-approved medical diagnostic agent that is widely used as a near-infrared (NIR) fluorescent imaging molecular probe. However, ICG tends to aggregate to form dimers or H-aggregates in water and lacks physical and optical stability, which greatly decreases its absorbance and fluorescence intensity in various applications. Additionally, ICG has no tissue- or tumor-targeting properties, and its structure is not easy to modify, which has further limited its application in cancer diagnosis. In this study, we addressed these challenges by developing a supramolecular colloidal carrier system that targets tumor cells. To this end, we synthesized a water-soluble β-cyclodextrin (β-CD) polymer conjugated with folate (FA), denoted PCD-FA, which is capable of forming inclusion complexes with ICG in water through host-guest interactions between the β-CD moieties and ICG molecules. The inclusion complexes formed by PCD-FA and ICG, called ICG@PCD-FA, dispersed stably in solution as colloidal nanoparticles, greatly improving the physical and optical properties of ICG by preventing ICG dimer formation, where ICG appeared as monomers and even J-aggregates. This resulted in stronger and more stable absorption at a longer wavelength of 900 nm, which may allow for deeper tissue penetration and imaging with reduced interference from biological tissues' autofluorescence. Moreover, ICG@PCD-FA showed a targeting effect on folate receptor-positive (FR+) tumor cells, which specifically highlighted FR+ cells via NIR endoscopic imaging. Notably, ICG@PCD-FA further improved permeation and accumulation in FR+ 3D tumor spheroids. Therefore, this ICG@PCD-FA supramolecular colloidal system may have a great potential for use in tumor NIR imaging and diagnostic applications.

A Facile Approach to Producing Liposomal J-Aggregates of Indocyanine Green with Diagnostic and Therapeutic Potential

Liposomal J-Aggregates of Indocyanine Green (L-JA) can serve as a biocompatible and biodegradable nanoparticle for photoacoustic imaging and photothermal therapy. When compared to monomeric IcG, L-JA are characterized by longer circulation, improved photostability, elevated absorption at longer wavelengths, and increased photoacoustic signal generation. However, the documented methods for production of L-JA vary widely. We developed an approach to efficiently form IcG J-aggregates (IcG-JA) directly in liposomes at elevated temperatures. Aggregating within fully formed liposomes ensures particle uniformity and allows for control of J-aggregate size. L-JA have unique properties compared to IcG. L-JA provide significant contrast enhancement in photoacoustic images for up to 24 hours after injection, while IcG and unencapsulated IcG-JA are cleared within an hour. L-JA allow for more accurate photoacoustic-based sO2 estimation and particle tracking compared to IcG. Furthermore, photothermal heating of L-JA with an 852nm laser is demonstrated to be more effective at lower laser powers than conventional 808nm lasers for the first time. The presented technique offers an avenue for formulating a multi-faceted contrast agent for photoacoustic imaging and photothermal therapy that offers significant advantages over other conventional agents.

Development of Indocyanine Green/Methyl-β-cyclodextrin Complex-Loaded Liposomes for Enhanced Photothermal Cancer Therapy

Photothermal therapy (PTT) is a promising cancer therapeutic approach due to its spatial selectivity and high potency. Indocyanine green (ICG) has been considered a biocompatible PTT agent. However, ICG has several challenges to hinder its clinical use including rapid blood clearance and instability to heat, light, and solvent, leading to a loss of photoactivation property and PTT efficacy. Herein, we leveraged stabilizing components, methyl-β-cyclodextrin and liposomes, in one nanoplatform (ICD lipo) to enhance ICG stability and the photothermal therapeutic effect against cancer. Compared to ICG, ICD lipo displayed a 4.8-fold reduction in degradation in PBS solvent after 30 days and a 3.4-fold reduction in photobleaching after near-infrared laser irradiation. Moreover, in tumor-bearing mice, ICD lipo presented a 2.7-fold increase in tumor targetability and inhibited tumor growth 9.6 times more effectively than did ICG without any serious toxicity. We believe that ICD lipo could be a potential PTT agent for cancer therapeutics.

Supramolecular dye nanoassemblies for advanced diagnostics and therapies

Dyes have conventionally been used in medicine for staining cells, tissues, and organelles. Since these compounds are also known as photosensitizers (PSs) which exhibit photoresponsivity upon photon illumination, there is a high desire towards formulating these molecules into nanoparticles (NPs) to achieve improved delivery efficiency and enhanced stability for novel imaging and therapeutic applications. Furthermore, it has been shown that some of the photophysical properties of these molecules can be altered upon NP formation thereby playing a major role in the outcome of their application. In this review, we primarily focus on introducing dye categories, their formulation strategies and how these strategies affect their photophysical properties in the context of photothermal and non-photothermal applications. More specifically, the most recent progress showing the potential of dye supramolecular assemblies in modalities such as photoacoustic and fluorescence imaging, photothermal and photodynamic therapies as well as their employment in photoablation as a novel modality will be outlined. Aside from their photophysical activity, we delve shortly into the emerging application of dyes as drug stabilizing agents where these molecules are used together with aggregator molecules to form stable nanoparticles.

Repurposing indocyanine green: exploring the potential of an old drug in modern medicine

The repurposing of existing drugs, referred to as theranostics, has made profound impacts on precision medicine. Indocyanine green (ICG), a well-established and clinical dye, has continued to be a star agent, described as a multifunctional molecule with concurrent photo- or sono-sensitiveness capabilities and co-delivery accessibility, showing remarkable potential in the area of unimodal or multimodal imaging-guided therapy of various diseases, leading to the extensive consideration of immediate clinical translations. In this review, we strive to bring the understanding of repurposing performance assessment for ICG into practice by clarifying the relationships between its features and applicability. Specifically, we address the obstacles encountered in the process of developing an ICG repurposing strategy, as well as the noteworthy advancements made in the field of ICG repurposing. We also go into detail about the structure-function correlations of drugs containing ICG and how different structural groups significantly affect the physicochemical properties.

An Indocyanine Green-Based Nanoprobe for In Vivo Detection of Cellular Senescence

There is an urgent need to improve conventional cancer-treatments by preventing detrimental side effects, cancer recurrence and metastases. Recent studies have shown that presence of senescent cells in tissues treated with chemo- or radiotherapy can be used to predict the effectiveness of cancer treatment. However, although the accumulation of senescent cells is one of the hallmarks of cancer, surprisingly little progress has been made in development of strategies for their detection in vivo. To address a lack of detection tools, we developed a biocompatible, injectable organic nanoprobe (NanoJagg), which is selectively taken up by senescent cells and accumulates in the lysosomes. The NanoJagg probe is obtained by self-assembly of indocyanine green (ICG) dimers using a scalable manufacturing process and characterized by a unique spectral signature suitable for both photoacoustic tomography (PAT) and fluorescence imaging. In vitro, ex vivo and in vivo studies all indicate that NanoJaggs are a clinically translatable probe for detection of senescence and their PAT signal makes them suitable for longitudinal monitoring of the senescence burden in solid tumors after chemotherapy or radiotherapy.

The role of phospholipids in drug delivery formulations - Recent advances presented at the Researcher's Day 2023 Conference of the Phospholipid Research Center Heidelberg

This Focus on Meetings contribution summarizes recent advances in the research on phospholipids and their applications for drug delivery and analytical purposes that have been presented at the hybrid Researcher's Day 2023 Conference of the Phospholipid Research Center (PRC), held on July 3-5, 2023, in Bad Dürkheim, Germany. The PRC is a non-profit organization focused on expanding and sharing scientific and technological knowledge of phospholipids in pharmaceutical and other applications. This is accomplished by, e.g., funding doctoral and postdoctoral research projects. The progress made with these projects is presented at the Researcher's Day Conference every two years. Four main topics were presented and discussed in various lectures: (1) formulation of phospholipid-based nanocarriers, (2) therapeutic applications of phospholipids and phospholipid-based nanocarriers, (3) phospholipids as excipients in oral, dermal, and parenteral dosage forms, and (4) interactions of phospholipids and phospholipid-based vesicles in biological environment and their use as analytical platforms.

Visualization and Quantification of Drug Release by GSH-Responsive Multimodal Integrated Micelles

Using molecular imaging techniques to monitor biomarkers and drug release profiles simultaneously is highly advantageous for cancer diagnosis and treatment. However, achieving the accurate quantification of both biomarkers and drug release with a single imaging modality is challenging. This study presents the development of a glutathione (GSH)-responsive polymer-based micelle, PEG-SS-FCy7/PEG-SS-GEM (PSFG), which can precisely localize the tumor using bimodal imaging and prevent drug leakage. These PSFG micelles exhibit a small particle size of 106.3 ± 12.7 nm with a uniform size distribution, and the drug loading efficiency can also be easily controlled by changing the PEG-SS-FCy7 (PSF) and PEG-SS-GEM (PSG) feeding ratio. The PSFG micelles display weak fluorescence emission and minimal drug release under physiological conditions but collapse in the presence of GSH to trigger near-infrared fluorescence and the 19F magnetic resonance imaging signal, allowing for real-time monitoring of intracellular GSH levels and drug release. GSH could synergistically promote the disassembly of the micellar structure, resulting in accelerated probe and drug release of up to about 93.1% after 24 h. These prodrug micelles exhibit high in vitro and in vivo antitumor abilities with minimal side effects. The GSH-responsive drug delivery system with dual-modal imaging capability provides a promising imaging-guided chemotherapeutic platform to probe the tumor microenvironment and quantify real-time drug release profiles with minimal side effects.

A combined experimental and DFT study of metal core/indocyanine green shell hybrid nanoparticles

Indocyanine green (ICG) is the FDA-approved fluorescent dye used for in vivo medical imaging, diagnostics, and photothermal therapy. However, this dye is easily degradable in the human vascular system, and therefore its stabilization is preferable. In this work, ICG molecules were stabilized by their adsorption on the surface of the L-methionine-capped Ag and Au nanoparticles (Ag and Au @LM NPs) in aqueous colloidal dispersions. The result is the formation of hybrid metal core/ICG shell NPs in colloidal dispersions. Additionally, colloidal dispersions were stabilized, indicating a double effect of ICG adsorption. The obtained hybrid NPs were studied experimentally (UV-Vis spectrophotometry, HRTEM, DLS, FTIR) and theoretically (DFT calculations). HRTEM revealed that the interplanar spacing between adjacent planes of NPs decreases after the dye adsorption. The results obtained from the DFT study confirmed the formation of a covalent bond between the oxygen from ICG dye SO3- group and metal NPs. Considering the characteristics of both components of the NPs/ICG hybrid system, the authors assume that this hybrid system can exhibit the synergistic effect that could lead to more successful theranostic treatment of cancer in nanomedicine.

Antibody-Conjugated Polymersomes with Encapsulated Indocyanine Green J-Aggregates and High Near-Infrared Absorption for Molecular Photoacoustic Cancer Imaging

Imaging plays a critical role in all stages of cancer care from early detection to diagnosis, prognosis, and therapy monitoring. Recently, photoacoustic imaging (PAI) has started to emerge into the clinical realm due to its high sensitivity and ability to penetrate tissues up to several centimeters deep. Herein, we encapsulated indocyanine green J (ICGJ) aggregate, one of the only FDA-approved organic exogenous contrast agents that absorbs in the near-infrared range, at high loadings up to ∼40% w/w within biodegradable polymersomes (ICGJ-Ps) composed of poly(lactide-co-glycolide-b-polyethylene glycol) (PLGA-b-PEG). The small Ps hydrodynamic diameter of 80 nm is advantageous for in vivo applications, while directional conjugation with epidermal growth factor receptor (EGFR) targeting cetuximab antibodies renders molecular specificity. Even when exposed to serum, the ∼11 nm-thick membrane of the Ps prevents dissociation of the encapsulated ICGJ for at least 48 h with a high ratio of ICGJ to monomeric ICG absorbances (i.e., I895/I780 ratio) of approximately 5.0 that enables generation of a strong NIR photoacoustic (PA) signal. The PA signal of polymersome-labeled breast cancer cells is proportional to the level of cellular EGFR expression, indicating the feasibility of molecular PAI with antibody-conjugated ICGJ-Ps. Furthermore, the labeled cells were successfully detected with PAI in highly turbid tissue-mimicking phantoms up to a depth of 5 mm with the PA signal proportional to the amount of cells. These data show the potential of molecular PAI with ICGJ-Ps for clinical applications such as tumor margin detection, evaluation of lymph nodes for the presence of micrometastasis, and laparoscopic imaging procedures.

Near-infrared light activatable niosomes loaded with indocyanine green and plasmonic gold nanorods for theranostic applications

Light-mediated theranostic platforms involve the use of agents (small molecules/nanomaterials), which can absorb light to produce either heat or reactive chemical species (RCS) and emit fluorescence. Such platforms are advantageous in the field of personalized medicine, as they provide enhanced diagnostic capabilities, improved therapeutic efficiencies, and can also simultaneously monitor the treatment outcomes using imaging modalities. Specifically, agents absorbing near-infrared (NIR) light can provide minimal scattering, low autofluorescence, superior spatio-temporal resolution, and deeper tissue penetration depths. Gold nanorods (GNR) and indocyanine green (ICG) are two agents known to absorb light in the NIR region. GNR can provide tunable plasmonic properties, while ICG is an FDA-approved NIR fluorophore. However, the use of ICG and GNR suffers from various limitations, such as photobleaching, non-specificity, toxicity, and aggregation in solution. To overcome these limitations, herein, we report on NIR light-activatable niosomes loaded with GNR and ICG for cancer theranostic applications. Both agents were encapsulated into non-ionic surfactant-based biocompatible niosomes to form ICG-GNR@Nio with superior loading efficiencies and enhanced properties. ICG-GNR@Nio offers excellent storage stability, photostability, elevated temperature rise and generation of reactive oxygen species (ROS) upon 1064 nm laser irradiation. Subsequently, the enhanced phototherapeutic capabilities mediated by ICG-GNR@Nio were validated in the in vitro cellular experiments. Overall, ICG-GNR@Nio-based theranostic platforms can provide a significant benchmark in the improved diagnosis and therapeutic capabilities for biomedical clinicians to tackle various diseases.

Indocyanine Green-Loaded Halloysite Nanotubes as Photothermal Agents

Photothermal nanoparticles with light-to-heat conversion properties have gained interest in recent years and have been used in a variety of applications. Herein, indocyanine green (ICG), which is commonly employed as a photothermal agent suffering from low photostability, was loaded into halloysite nanotubes (HNTs) resulting in photothermal HNT-ICG nanohybrids. The photothermal heating patterns of the prepared photothermal nanohybrids as a result of near-infrared (NIR) irradiation were carefully examined. The nanohybrids reached a temperature of 216 °C in 2 min under NIR light, and in contrast to free NIR, the ICG loaded into HNTs remained stable over 10 heating and cooling cycles. Moreover, HNT-ICG nanohybrids incorporated into polyacrylonitrile (PAN) were electrospun into nanofibers for use as photothermal nanofibers, and composite nanofibers, which heat up to 79.3 °C under 2 min of NIR irradiation, were obtained. To demonstrate the potential of the PAN/HNT-ICG nanofibers as light-activated antibacterial nanofibers, their NIR light-activated killing activity on Staphylococcus aureus (S. aureus) cells has been explored. The composite nanofibers reduced the number of bacteria on their surface by 7log upon 10 min of NIR irradiation. Encapsulation of ICG in HNTs as a carrier has been demonstrated as an effective way to stabilize ICG and incorporate it into materials and coatings without compromising its functionality.

Enhanced stability and photothermal efficiency of Indocyanine Green J-aggregates by nanoformulation with Calix[4]arene for photothermal therapy of cancers

Photothermal therapy (PTT) is a method of growing attention, owing to its controllable process, high efficiency and minimal side effect. Indocyanine Green (ICG) is as Food and Drug Administration (FDA) approved agent that stands on the frontline of further developments of PTT toward clinics. However, the applicability of ICG-mediated PTT is limited by the rapid in vivo clearance and photo-degradation of ICG. To improve those parameters, nanosized ICG-loaded nanoparticles (ICG-J/CX) were fabricated in this study by co-assembly of anionic ICG J-aggregates (ICG-J) with cationic tetraguanidinium calix[4]arene (CX). This very simple approach produces ICG-J/CX with a well-defined nanometer range size and a close to neutral charge. The nanoparticles demonstrate high photothermal conversion efficiency (PCE) and dramatically improved photostability, as compared with ICG. The in vitro cellular uptake and cytotoxicity studies further demonstrated that the ICG-J/CX nanoparticles enhance uptake and photothermal efficiency in comparison with ICG or non-formulated ICG-J, overall demonstrating that ICG-J/CX mediated photothermal therapy have significant potential for attaining cancer treatment.

Indocyanine Green (ICG) Fluorescence Is Dependent on Monomer with Planar and Twisted Structures and Inhibited by H-Aggregation

The optical properties of indocyanine green (ICG) as a near-infrared (NIR) fluorescence dye depend on the nature of the solvent medium and the dye concentration. In the ICG absorption spectra of water, at high concentrations, there were absorption maxima at 700 nm, implying H-aggregates. With ICG dilution, the main absorption peak was at 780 nm, implying monomers. However, in ethanol, the absorption maximum was 780 nm, and the shapes of the absorption spectra were identical regardless of the ICG concentration, indicating that ICG in ethanol exists only as a monomer without H-aggregates. We found that emission was due to the monomer form and decreased with H-aggregate formation. In the fluorescence spectra, the 820 nm emission band was dominant at low concentrations, whereas at high concentrations, we found that the emission peaks were converted to 880 nm, suggesting a new form via the twisted intramolecular charge transfer (TICT) process of ICG. The NIR fluorescence intensity of ICG in ethanol was approximately 12- and 9-times brighter than in water in the NIR-I and -II regions, respectively. We propose an energy diagram of ICG to describe absorptive and emissive transitions through the ICG structures such as the monomer, H-aggregated, and TICT monomer forms.

Medical Applications and Advancement of Near Infrared Photosensitive Indocyanine Green Molecules

Indocyanine green (ICG) is an important kind of near infrared (NIR) photosensitive molecules for PTT/PDT therapy as well as imaging. When exposed to NIR light, ICG can produce reactive oxygen species (ROS), which can kill cancer cells and pathogenic bacteria. Moreover, the absorbed light can also be converted into heat by ICG molecules to eliminate cancer cells. In addition, it performs exceptionally well in optical imaging-guided tumor therapy and antimicrobial therapy due to its deeper tissue penetration and low photobleaching properties in the near-infrared region compared to other dyes. In order to solve the problems of water and optical stability and multi-function problem of ICG molecules, composite nanomaterials based on ICG have been designed and widely used, especially in the fields of tumors and sterilization. So far, ICG molecules and their composite materials have become one of the most famous infrared sensitive materials. However, there have been no corresponding review articles focused on ICG molecules. In this review, the molecular structure and properties of ICG, composite material design, and near-infrared light- triggered anti-tumor, and antibacterial, and clinical applications are reviewed in detail, which of great significance for related research.

Maximum Emission Peak Over 1500 nm of Organic Assembly for Blood-Brain Barrier-Crossing NIR-IIb Phototheranostics of Orthotopic Glioblastoma

The development of blood-brain barrier (BBB)-crossing phototheranostic agents in second near-infrared window (NIR-II), especially in the range of 1500-1700 nm (NIR-IIb), affords great opportunities for glioblastoma (GBM) management. Herein, an organic assembly (denoted as LET-12) with the maximum absorption peak at 1400 nm and emission peak at 1512 nm with trailing over 1700 nm through the self-assembly of organic small molecule IR-1064 is designed and subsequently decorated with choline and acetylcholine analogs. The LET-12 can effectively cross BBB through the brain's choline-like receptors-mediated transcytosis and accumulated in tumor tissues, thus achieving fluorescence/photoacoustic (FL/PA) duplex imaging of orthotopic GBM with ≈3.0 mm depth and a superior tumor-to-normal tissue signal ratio (20.93 ± 0.59 for FL imaging and 32.63 ± 1.16 for PA imaging, respectively). Owing to its good photothermal conversion ability, the LET-12 also can serve as a photothermal conversion agent, achieving obvious tumor repression of orthotopic murine GBM model after once treatment. The findings indicate that the LET-12 holds great potential for BBB-crossing NIR-IIb phototheranostics of orthotopic GBM. This self-assembly strategy of organic small molecules opens a new avenue for the construction of NIR-IIb phototheranostics.

Enzyme-Activatable Polypeptide for Plasma Membrane Disruption and Antitumor Immunity Elicitation

Enzyme-instructed self-assembly of bioactive molecules into nanobundles inside cells is conceived to potentially disrupt plasma membrane and subcellular structure. Herein, an alkaline phosphatase (ALP)-activatable hybrid of ICG-CF₄ KY^p is facilely synthesized by conjugating photosensitizer indocyanine green (ICG) with CF₄ KY^p peptide via classical Michael addition reaction. ALP-induced dephosphorylation of ICG-CF₄ KY^p enables its transformation from small-molecule precursor into rigid nanofibrils, and such fibrillation in situ causes severe mechanical disruption of cytomembrane. Besides, ICG-mediated photosensitization causes additional oxidative damage of plasma membrane by lipid peroxidation. Hollow MnO₂ nanospheres devote to deliver ICG-CF₄ KY^p into tumorous tissue through tumor-specific acidity/glutathione-triggered degradation of MnO₂ , which is monitored by fluorescent probing and magnetic resonance imaging. The burst release of damage-associated molecular patterns and other tumor antigens during therapy effectively triggers immunogenetic cell death and improves immune stimulatory, as demonstrated by the promotion of dendritic cell maturation and CD8⁺ lymphocyte infiltration, as well as constraint of regulatory T cell population. Taken together, such cytomembrane injury strategy based on peptide fibrillation in situ holds high clinical promise for lesion-specific elimination of primary, abscopal, and metastatic tumors, which may enlighten more bioinspired nanoplatforms for anticancer theranostics.

In situ orderly self-assembly strategy affording NIR-II-J-aggregates for in vivo imaging and surgical navigation

J-aggregation, an effective strategy to extend wavelength, has been considered as a promising method for constructing NIR-II fluorophores. However, due to weak intermolecular interactions, conventional J-aggregates are easily decomposed into monomers in the biological environment. Although adding external carriers could help conventional J-aggregates stabilize, such methods still suffer from high-concentration dependence and are unsuitable for activatable probes design. Besides, these carriers-assisted nanoparticles are risky of disassembly in lipophilic environment. Herein, by fusing the precipitated dye (HPQ) which has orderly self-assembly structure, onto simple hemi-cyanine conjugated system, we construct a series of activatable, high-stability NIR-II-J-aggregates which overcome conventional J-aggregates carrier's dependence and could in situ self-assembly in vivo. Further, we employ the NIR-II-J-aggregates probe HPQ-Zzh-B to achieve the long-term in situ imaging of tumor and precise tumor resection by NIR-II imaging navigation for reducing lung metastasis. We believe this strategy will advance the development of controllable NIR-II-J-aggregates and precise bioimaging in vivo.

Size-tunable ICG-based contrast agent platform for targeted near-infrared photoacoustic imaging

Near-infrared photoacoustic imaging (NIR-PAI) combines the advantages of optical and ultrasound imaging to provide anatomical and functional information of tissues with high resolution. Although NIR-PAI is promising, its widespread use is hindered by the limited availability of NIR contrast agents. J-aggregates (JA) made of indocyanine green dye (ICG) represents an attractive class of biocompatible contrast agents for PAI. Here, we present a facile synthesis method that combines ICG and ICG-azide dyes for producing contrast agents with tunable size down to 230 nm and direct functionalization with targeting moieties. The ICG-JA platform has a detectable PA signal in vitro that is two times stronger than whole blood and high photostability. The targeting ability of ICG-JA was measured in vitro using HeLa cells. The ICG-JA platform was then injected into mice and in vivo NIR-PAI showed enhanced visualization of liver and spleen for 90 min post-injection with a contrast-to-noise ratio of 2.42.

J-Aggregates Formed by NaCl Treatment of Aza-Coating Heptamethine Cyanines and Their Application to Monitoring Salt Stress of Plants and Promoting Photothermal Therapy of Tumors

The cationic nature of heptamethine cyanines gives them the capacity to form aggregates with salts by electrostatic interactions. In this work, NaCl promoted J-aggregate formation of aza-coating heptamethine cyanines is explored. NaCl can induce the N-benzyloxycarbonyl Cy-CO₂ Bz to assemble into a J-aggregate having an absorption at 890 nm. Its excellent fluorescence response to NaCl implies that it has great potential for use as a probe for tracing salt stress in plants. Moreover, NaCl also promotes formation of J-aggregates from the N-ethyloxycarbonyl Cy-CO₂ Et. The aggregate shows an intense absorption at 910 nm compared to the monomer which absorbs at 766 nm. Its J-aggregated form can serve as a photothermal agent. And the photothermal conversion efficiency is increased from 29.37 % to 57.59 %. This effort leads to the development of two applications of new cyanine J-aggregates including one for tracing salt stress of plants and the other for promoting photothermal therapy of tumors.

J-aggregation strategy of organic dyes for near-infrared bioimaging and fluorescent image-guided phototherapy

With the continuous development of organic materials for optoelectronic devices and biological applications, J-aggregation has attracted a great deal of interest in both dye chemistry and supramolecular chemistry. Except for the characteristic red-shifted absorption and emission, such ordered head-to-tail stacked structures may be accompanied by special properties such as enhanced absorption, narrowed spectral bandwidth, improved photothermal and photodynamic properties, aggregation-induced emission enhancement (AIEE) phenomenon, and so forth. These excellent properties add great potential to J-aggregates for optical imaging and phototherapy in the near-infrared (NIR) region. Despite decades of development, the challenge of rationally designing the molecular structure to adjust intermolecular forces to induce J-aggregation of organic dyes remains significant. In this review, we discuss the formation of J-aggregates in terms of intermolecular interactions and summarize some recent studies on J-aggregation dyes for NIR imaging and phototherapy, to provide a clear direction and reference for designing J-aggregates of near-infrared organic dyes to better enable biological applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Optical Characteristics of Indocyanine Green J-Aggregates Induced by Cisplatin for Phototheranostic Applications

The development of an optical system for combinatorial theranostics is of significant interest. Clinical translation of such theranostic agents need to cross several barriers. Herein, we have developed a facile method for the preparation of J-aggregates using FDA approved agents, namely, NIR fluorophore indocyanine green (ICG) and a chemotherapeutic drug, cisplatin (CDDP), which induces ICG to form indocyanine green J-aggregates (IJAs). The formation of IJAs has been characterized by the formation of a new absorption peak centered at ∼896 nm. The existing methods to synthesize IJAs have used several harsh reaction conditions, such as elevated temperatures, for a prolonged time duration (∼60 days). To the best of our knowledge, for the first time, we have reported the formation of IJAs assisted by CDDP at 37 °C temperature within 12 h. The presence of CDDP in ICG favors IJA formation and thereby reduces the harshness of the reaction conditions in the conventionally followed protocols. Moreover, the presence of CDDP can facilitate photoactivated combinatorial therapy. The as synthesized IJA optical system has superior properties to those of free ICG, in terms of diagnostic and therapeutic capabilities (being activatable at ∼896 nm wavelength, which can achieve deeper tissue penetration) and excellent optical and storage stability. The facile synthesis proposed along with CDDP incorporation makes the optical system a clinically relevant one-component theranostic agent.

Supramolecular Loading of DNA Hydrogels with Dye-Drug Conjugates for Real-Time Photoacoustic Monitoring of Chemotherapy

A longstanding problem with conventional cancer therapy is the nonspecific distribution of chemotherapeutics. Monitoring drug release in vivo via noninvasive bioimaging can thus have value, but it is difficult to distinguish loaded from released drug in live tissue. Here, this work describes an injectable supramolecular hydrogel that allows slow and trackable release of doxorubicin (Dox) via photoacoustic (PA) tomography. Dox is covalently linked with photoacoustic methylene blue (MB) to monitor Dox before, during, and after release from the hydrogel carrier. The conjugate (MB-Dox) possesses an IC50 of 161.4 × 10-9  m against human ovarian carcinoma (SKOV3) cells and loads into a DNA-clad hydrogel with 91.3% loading efficiency due to MB-Dox's inherent intramolecular affinity to DNA. The hydrogel is biodegradable by nuclease digestion, which causes gradual release of MB-Dox. This release rate is tunable based on the wt% of the hydrogel. This hydrogel maintains distinct PA contrast on the order of days when injected in vivo and demonstrates activatable PA spectral shifts   during hydrogel degradation. The released and loaded payload can be imaged relative to live tissue via PA and ultrasound signal being overlaid in real-time. The hydrogel slowed the rate of the murine intraperitoneal tumor growth 72.2% more than free Dox.

Correlation of spectroscopic and structural properties of indocyanine green j-aggregates

Indocyanine green (ICG), when in free form in a liquid, can form stable nanoparticle structures or colloidal solution, while changing its spectroscopic properties. In the work, the aggregation degree and the average size of nanoparticles depending on the concentration of a colloidal solution of indocyanine green (ICG NPs) in the form of J-aggregates were investigated by various methods based on light scattering. The size of nanoparticles is an important parameter from the point of view of clinical application, because the technique of intravenous administration of drugs, in order to avoid microvascular thrombosis and embolism, provides dosage forms with inclusions of individual molecules or their clusters, not exceeding 500 nm diameter. In turn, small nanoparticles less than 30 nm lead to prolonged circulation of the drug in the body with an increased possibility of permeation into cells of healthy tissue. In the course of studies, it was found that an increase in the concentration of ICG NPs in the solution leads to an increase in the average size of spontaneously formed J-aggregates, which, in turn, leads to a decrease in the absorption coefficient in the aggregates. Presumably, this phenomenon, i.e. the established nonlinear dependence of the J-aggregate absorption on its size, can be explained by the formation of absorption centers on the J-aggregate surface in the form of mobile surface molecules. The threshold range of ICG molecule concentration was determined, at which there is a transition from aggregation with an increase in size with a slow addition of ICG J-aggregate molecules in height to a rapid addition in width.

The Pursuit of Shortwave Infrared-Emitting Nanoparticles with Bright Fluorescence through Molecular Design and Excited-State Engineering of Molecular Aggregates

Shortwave infrared (SWIR) fluorescence detection gradually becomes a pivotal real-time imaging modality, allowing one to elucidate biological complexity in deep tissues with subcellular resolution. The key challenge for the further growth of this imaging modality is the design of new brighter biocompatible fluorescent probes. This review summarizes the recent progress in the development of organic-based nanomaterials with an emphasis on new strategies that extend the fluorescence wavelength from the near-infrared to the SWIR spectral range and amplify the fluorescence brightness. We first introduce the most representative molecular design strategies to obtain near-infrared-SWIR wavelength fluorescence emission from small organic molecules. We then discuss how the formation of nanoparticles based on small organic molecules contributes to the improvement of fluorescence brightness and the shift of fluorescence to SWIR, with a special emphasis on the excited-state engineering of molecular probes in an aggregate state and spatial packing of the molecules in nanoparticles. We build our discussion based on a historical perspective on the photophysics of molecular aggregates. We extend this discussion to nanoparticles made of conjugated polymers and discuss how fluorescence characteristics could be improved by molecular design and chain conformation of the polymer molecules in nanoparticles. We conclude the article with future directions necessary to expand this imaging modality to wider bioimaging applications including single-particle deep tissue imaging. Issues related to the characterization of SWIR fluorophores, including fluorescence quantum yield unification, are also mentioned.

Synthesis and Study on Aggregation Behaviors in Liquid Phase of Three Prepared Cyanine Dyes

Here we investigate the aggregation behaviors of three prepared dyes in the liquid phase to pick out one possessing J-aggregation characteristic which is of significant interest for organic materials used in multiple bio-applications. The self-assembly of dyes usually leads to various forms of aggregates, for example, H-aggregates or J-aggregates and it is easy to distinguish bathochromic J-aggregation from hypsochromic H-aggregation by UV/Vis spectroscopy. Enlightened by the cyanine dyes which have shown a great tendency to self-associate, we designed and synthesized three cyanine dyes: Cy7-Ph, DCy7-Ph, SN-Cy7-Ph, followed by the study of the influence of multiple factors to their aggregation behaviors, including solvent polarity, ionic strength and temperature. Finally, we found that only SN-Cy7-Ph of the three molecules can self-assemble into J-aggregates conveniently and stably in the aqueous phase under normal conditions.

Interfacing DNA nanotechnology and biomimetic photonic complexes: advances and prospects in energy and biomedicine

Self-assembled photonic systems with well-organized spatial arrangement and engineered optical properties can be used as efficient energy materials and as effective biomedical agents. The lessons learned from natural light-harvesting antennas have inspired the design and synthesis of a series of biomimetic photonic complexes, including those containing strongly coupled dye aggregates with dense molecular packing and unique spectroscopic features. These photoactive components provide excellent features that could be coupled to multiple applications including light-harvesting, energy transfer, biosensing, bioimaging, and cancer therapy. Meanwhile, nanoscale DNA assemblies have been employed as programmable and addressable templates to guide the formation of DNA-directed multi-pigment complexes, which can be used to enhance the complexity and precision of artificial photonic systems and show the potential for energy and biomedical applications. This review focuses on the interface of DNA nanotechnology and biomimetic photonic systems. We summarized the recent progress in the design, synthesis, and applications of bioinspired photonic systems, highlighted the advantages of the utilization of DNA nanostructures, and discussed the challenges and opportunities they provide.

Multiplexed imaging in oncology

In oncology, technologies for clinical molecular imaging are used to diagnose patients, establish the efficacy of treatments and monitor the recurrence of disease. Multiplexed methods increase the number of disease-specific biomarkers that can be detected simultaneously, such as the overexpression of oncogenic proteins, aberrant metabolite uptake and anomalous blood perfusion. The quantitative localization of each biomarker could considerably increase the specificity and the accuracy of technologies for clinical molecular imaging to facilitate granular diagnoses, patient stratification and earlier assessments of the responses to administered therapeutics. In this Review, we discuss established techniques for multiplexed imaging and the most promising emerging multiplexing technologies applied to the imaging of isolated tissues and cells and to non-invasive whole-body imaging. We also highlight advances in radiology that have been made possible by multiplexed imaging.

pH-Responsive Polymer Nanomaterials for Tumor Therapy

The complexity of the tumor microenvironment presents significant challenges to cancer therapy, while providing opportunities for targeted drug delivery. Using characteristic signals of the tumor microenvironment, various stimuli-responsive drug delivery systems can be constructed for targeted drug delivery to tumor sites. Among these, the pH is frequently utilized, owing to the pH of the tumor microenvironment being lower than that of blood and healthy tissues. pH-responsive polymer carriers can improve the efficiency of drug delivery in vivo, allow targeted drug delivery, and reduce adverse drug reactions, enabling multifunctional and personalized treatment. pH-responsive polymers have gained increasing interest due to their advantageous properties and potential for applicability in tumor therapy. In this review, recent advances in, and common applications of, pH-responsive polymer nanomaterials for drug delivery in cancer therapy are summarized, with a focus on the different types of pH-responsive polymers. Moreover, the challenges and future applications in this field are prospected.

Chemical Design of Activatable Photoacoustic Probes for Precise Biomedical Applications

Photoacoustic (PA) imaging technology, a three-dimensional hybrid imaging modality that integrates the advantage of optical and acoustic imaging, has great application prospects in molecular imaging due to its high imaging depth and resolution. To endow PA imaging with the ability for real-time molecular visualization and precise biomedical diagnosis, numerous activatable molecular PA probes which can specifically alter their PA intensities upon reacting with the targets or biological events of interest have been developed. This review highlights the recent developments of activatable PA probes for precise biomedical applications including molecular detection of the biotargets and imaging of the biological events. First, the generation mechanism of PA signals will be given, followed by a brief introduction to contrast agents used for PA probe design. Then we will particularly summarize the general design principles for the alteration of PA signals and activatable strategies for developing precise PA probes. Furthermore, we will give a detailed discussion of activatable PA probes in molecular detection and biomedical imaging applications in living systems. At last, the current challenges and outlooks of future PA probes will be discussed. We hope that this review will stimulate new ideas to explore the potentials of activatable PA probes for precise biomedical applications in the future.

Design Principles Governing the Development of Theranostic Anticancer Agents and Their Nanoformulations with Photoacoustic Properties

The unmet need to develop novel approaches for cancer diagnosis and treatment has led to the evolution of theranostic agents, which usually include, in addition to the anticancer drug, an imaging agent based mostly on fluorescent agents. Over the past few years, a non-invasive photoacoustic imaging modality has been effectively integrated into theranostic agents. Herein, we shed light on the design principles governing the development of theranostic agents with photoacoustic properties, which can be formulated into nanocarriers to enhance their potency. Specifically, we provide an extensive analysis of their individual constituents including the imaging dyes, drugs, linkers, targeting moieties, and their formulation into nanocarriers. Along these lines, we present numerous relevant paradigms. Finally, we discuss the clinical relevance of the specific strategy, as also the limitations and future perspectives, and through this review, we envisage paving the way for the development of theranostic agents endowed with photoacoustic properties as effective anticancer medicines.

Analysis of Fluorescence Decay Kinetics of Indocyanine Green Monomers and Aggregates in Brain Tumor Model In Vivo

Spectroscopic approach with fluorescence time resolution allows one to determine the state of a brain tumor and its microenvironment via changes in the fluorescent dye's fluorescence lifetime. Indocyanine green (ICG) is an acknowledged infra-red fluorescent dye that self-assembles into stable aggregate forms (ICG NPs). ICG NPs aggregates have a tendency to accumulate in the tumor with a maximum accumulation at 24 h after systemic administration, enabling extended intraoperative diagnostic. Fluorescence lifetime analysis of ICG and ICG NPs demonstrates different values for ICG monomers and H-aggregates, indicating promising suitability for fluorescent diagnostics of brain tumors due to their affinity to tumor cells and stability in biological tissue.

Fluorescence imaging analysis of distribution of indocyanine green in molecular and nanoform in tumor model

BACKGROUND

The efficient intraoperative identification of tumors requires the development of highly specific near-infrared (NIR) probes as contrast agents. One of the most effective dyes existing in clinic oncology is Indocyanine Green (ICG). However, ICG has a rapid excretion, thus ruling out its extended accumulation in pathological tissues therefore limiting its clinical applications. ICG colloid solution (ICG NPs) consists predominantly of J-aggregates and to a lesser extent of H-aggregates and monomers. In the present study we assessed the spectral properties of ICG nanoforms in preclinical models.

METHODS

We used optical spectroscopy and video fluorescence navigation to monitor accumulation and distribution of ICG monomers and ICG NPs in various tissues in mice with xenografted laryngopharyngeal carcinoma after intravenous drugs injection.

RESULTS

After i.v. injection, the molecular form of ICG was not retained in the tumor and its circulation cycle averaged 5 min. Alternatively, the nanoform of the drug had a different pharmacokinetics, reaching maximum accumulation 24 h after intravenous injection. Moreover, once in the circulation, we observed a progressive accumulation in the tumor of both ICG H-aggregates and ICG monomers, but not J-aggregates.

CONCLUSION

Spectral characteristics of ICG NPs indicated the presence of several fractions, namely, J- and H-aggregates along with molecular forms. These fractions had different fluorescence spectra, allowing us to track the transformation of the drug in vivo conditions. After ICG NPs administration, J-aggregates induce accumulation of monomeric forms in the tumor, enabling extended intraoperative diagnostic, and as such further studies of J-aggregates for theranostic applications in oncological surgery are of great interest.

Unsymmetrical cyanine dye via in vivo hitchhiking endogenous albumin affords high-performance NIR-II/photoacoustic imaging and photothermal therapy

Herein, an unprecedented synergistic strategy for the development of high-performance NIR-II fluorophore is proposed and validated. Based on an unsymmetrical cyanine dye design strategy, the NIR-II emissive dye NIC was successfully developed by replacing only one of the indoline donors of symmetrical cyanine dye ICG with a fully conjugated benz[c,d]indole donor. This minor structural change maximally maintains the high extinction coefficient advantage of cyanine dyes. NIC-ER with endogenous albumin-hitchhiking capability was constructed to further enhance its in vivo fluorescence brightness. In the presence of HSA (Human serum albumin), NIC-ER spontaneously resides in the albumin pocket, and a brilliant ~89-fold increase in fluorescence was observed. Due to its high molar absorptivity and moderate quantum yield, NIC-ER in HSA exhibits bright NIR-II emission with high photostability and significant Stokes shift (>110 nm). Moreover, NIC-ER was successfully employed for tumor-targeted NIR-II/PA imaging and efficient photothermal tumor elimination. Overall, our strategy may open up a new avenue for designing and constructing high-performance NIR-II fluorophores.

Optical-Property-Enhancing Novel Near-Infrared Active Niosome Nanoformulation for Deep-Tissue Bioimaging

Indocyanine green (ICG) is a clinically approved near-infrared (NIR) contrast agent used in medical diagnosis. However, ICG has not been used to its fullest for biomedical imaging applications due to its low fluorescence quantum yield, aqueous instability, concentration-dependent aggregation, and photo and thermal degradations, leading to quenching of its fluorescence emission. In the present study, a nanosized niosomal formulation, ICGNiosomes (ICGNios), is fabricated to encapsulate and protect ICG from degradation. Interestingly, compared to free ICG, the ICGNios exhibited higher fluorescence quantum yield and fluorescence emission with a bathochromic shift. Also, ICGNios nanoparticles are biocompatible, biodegradable, and readily uptaken by the cells. Furthermore, ICGNios show more enhanced fluorescence intensity through ∼1 cm thick chicken breast tissue compared to free ICG, which showed minimal emission through the same thickness of tissue. Our results suggest that ICGNios could offer a promising platform for deep-tissue NIR in vivo imaging to visualize inaccessible tissue microstructures for disease diagnosis and therapeutics.

Indocyanine green-carrying polymeric nanoparticles with acid-triggered detachable PEG coating and drug release for boosting cancer photothermal therapy

In order to boost anticancer efficacy of indocyanine green (ICG)-mediated photothermal therapy (PTT) by promoting intracellular ICG delivery, the ICG-carrying hybrid polymeric nanoparticles were fabricated in this study by co-assembly of hydrophobic poly(lactic-co-glycolic acid) (PLGA) segments, ICG molecules, amphiphilic tocopheryl polyethylene glycol succinate (TPGS) and pH-responsive methoxy poly(ethylene glycol)-benzoic imine-1-octadecanamine (mPEG-b-C18) segments in aqueous solution. The ICG-loaded nanoparticles were characterized to have ICG-containing PLGA core stabilized by hydrophilic PEG-rich surface coating and a well-dispersed spherical shape. Moreover, the ICG-loaded nanoparticles in pH 7.4 aqueous solution sufficiently inhibited ICG self-aggregation and leakage, thereby increasing aqueous photostability of ICG molecules. Notably, when the solution pH was reduced from pH 7.4-5.5, the acid-triggered hydrolysis of benzoic-imine linkers within mPEG-b-C18 remarkably facilitated the detachment of mPEG segments from ICG-loaded nanoparticles, thus accelerating ICG release. The findings of in vitro cellular uptake and cytotoxicity studies further demonstrated that the PEGylated ICG-carrying hybrid nanoparticles were efficiently internalized by MCF-7 cells compared to free ICG and realized intracellular acid-triggered rapid ICG liberation, thus enhancing anticancer effect of ICG-mediated PTT to potently kill cancer cells.

Exploiting cyanine dye J-aggregates/monomer equilibrium in hydrophobic protein pockets for efficient multi-step phototherapy: an innovative concept for smart nanotheranostics

After several decades of development in the field of near-infrared (NIR) dyes for photothermal therapy (PTT), indocyanine green (ICG) still remains the only FDA-approved NIR contrast agent. However, upon NIR light irradiation ICG can react with molecular oxygen to form reactive oxygen species and degrade the ICG core, losing the convenient dye properties. In this work, we introduce a new approach for expanding the application of ICG in nanotheranostics, which relies on the confinement of self-organized J-type aggregates in hydrophobic protein domains acting as monomer depots. Upon the fast photobleaching, while the dye is irradiated, this strategy permits the equilibrium-driven monomer replacement after each irradiation cycle that radically increases the systems' effectivity and applicability. Gadolinium-doped casein micelles were designed to prove this novel concept at the same time as endowing the nanosystems with further magnetic resonance imaging (MRI) ability for dual-modal imaging-guided PTT. By teaching a new trick to a very old dog, the clinical prospect of ICG will undoubtedly be boosted laying the foundation for novel therapeutics. It is anticipated that future research could be expanded to other relevant J-aggregates-forming cyanine dyes or nanocrystal formulations of poorly water-soluble photosensitizers.

Photosensitizer Nanoparticles Boost Photodynamic Therapy for Pancreatic Cancer Treatment

Patients with pancreatic cancer (PCa) have a poor prognosis apart from the few suitable for surgery. Photodynamic therapy (PDT) is a minimally invasive treatment modality whose efficacy and safety in treating unresectable localized PCa have been corroborated in clinic. Yet, it suffers from certain limitations during clinical exploitation, including insufficient photosensitizers (PSs) delivery, tumor-oxygenation dependency, and treatment escape of aggressive tumors. To overcome these obstacles, an increasing number of researchers are currently on a quest to develop photosensitizer nanoparticles (NPs) by the use of a variety of nanocarrier systems to improve cellular uptake and biodistribution of photosensitizers. Encapsulation of PSs with NPs endows them significantly higher accumulation within PCa tumors due to the increased solubility and stability in blood circulation. A number of approaches have been explored to produce NPs co-delivering multi-agents affording PDT-based synergistic therapies for improved response rates and durability of response after treatment. This review provides an overview of available data regarding the design, methodology, and oncological outcome of the innovative NPs-based PDT of PCa.

Dual Color Imaging from a Single BF2-Azadipyrromethene Fluorophore Demonstrated in vivo for Lymph Node Identification

Dual emissions at ~700 and 800 nm have been achieved from a single NIR-AZA fluorophore 1 by establishing parameters in which it can exist in either its isolated molecular or aggregated states. Dual near infrared (NIR) fluorescence color lymph node (LN) mapping with 1 was achieved in a large-animal porcine model, with injection site, channels and nodes all detectable at both 700 and 800 nm using a preclinical open camera system. The fluorophore was also compatible with imaging using two clinical instruments for fluorescence guided surgery. Methods: An NIR-AZA fluorophore with hydrophilic and phobic features was synthesised in a straightforward manner and its aggregation properties characterised spectroscopically and by TEM imaging. Toxicity was assessed in a rodent model and dual color fluorescence imaging evaluated by lymph node mapping in a large animal porcine models and in ex-vivo human tissue specimen. Results: Dual color fluorescence imaging has been achieved in the highly complex biomedical scenario of lymph node mapping. Emissions at 700 and 800 nm can be achieved from a single fluorophore by establishing molecular and aggregate forms. Fluorophore was compatible with clinical systems for fluorescence guided surgery and no toxicity was observed in high dosage testing. Conclusion: A new, biomedical compatible form of NIR-dual emission wavelength imaging has been established using a readily accessible fluorophore with significant scope for clinical translation.

pH-responsive polymeric micelles self-assembled from benzoic-imine-containing alkyl-modified PEGylated chitosan for delivery of amphiphilic drugs

In order to efficiently promote loading efficiency and aqueous photostability of indocyanine green (ICG), an amphiphilic tricarbocyanine dye, the polysaccharide-based nanomicelles utilized as a vehicle for ICG were fabricated by self-assembly of the amphiphilic benzoic-imine-containing PEGylated chitosan/4-(dodecyloxy)benzaldehyde (DBA) conjugates in aqueous solution of pH 7.4. The resulting polymeric micelles were characterized to have a hydrophobic hybrid chitosan/DBA core surrounded by hydrophilic PEG shells. Importantly, the encapsulation of ICG into the hybrid chitosan/DBA core of polymeric micelles by the combined hydrophobic and electrostatic interactions not only promoted the ICG loading but also enhanced its aqueous photostability. With the pH of micelle suspension being reduced from 7.4 to 5.0, upon acid-triggered cleavage of benzoic-imine bonds between chitosan and DBA as well as the extending of the protonated chitosan segments from hybrid cores toward aqueous phase, the rather hydrophobic DBA-rich core was formed within micelles, thereby leading to shrinking of the polymeric micelles. The robust ICG-loaded polymeric micelles showed several superior properties including the inhibition of ICG leakage under the mimic physiological and acidic conditions, favorable biocompatibility and photo-activated hyperthermia effect. This work suggests that the pH-responsive ICG-carrying chitosan-based micelles display great potential in cancer theranostic.

A pH-Sensitive Self-Assembled and Carrier-Free Nanoparticle Based on Charge Reversal for Enhanced Synergetic Chemo-Phototherapy

To overcome biological barriers for nanoparticles (NPs) efficaciously accumulated at tumor sites, as well as enhancing the performance of drug delivery systems, a carrier-free nanoparticle based on charge reversal is designed for improved synergetic chemo-phototherapy for cancer treatment. In this system, doxorubicin (Dox) and zinc phthalocyanine (ZnPc) are self-assembled through noncovalent interactions (π-π stacking, hydrophobic forces) to avoid the possible toxicity of excipient, complex chemical conjugations and batch-to-batch variation. A trace amount of poly(2-(di-methylamino) ethylmethacrylate)- poly[(R)-3-hydroxybutyrate]- poly(2-(dimethylamino) ethylmethacrylate (PDMAEMA-PHB-PDMAEMA) is modified on the surface of Dox-ZnPc to construct the novel nanoparticles, namely DZP, with long-term stability, and with a dual-drug load content of up to ≈90％. The drug delivery system (DDS) can effectively decrease its toxicity among physical circulation and increase the accumulation at the tumor site. Moreover, the developed DZP nanoparticles show excellent photo-chemotherapy, photoacoustic (PA) and fluorescence (FL) imaging characteristics for multimodal imaging-guided synergetic therapy.

Excitation Transfer in Hybrid Nanostructures of Colloidal Ag2S/TGA Quantum Dots and Indocyanine Green J-Aggregates

The regularities of the electron excitations exchange in hybrid associates of colloidal Ag₂S quantum dots, passivated with thioglycolic acid (Ag₂S/TGA QDs) with an average size of 2.2 and 3.7 nm with Indocyanine Green J-aggregates (ICG) were studied in this work by methods of absorption and luminescence spectroscopy. It was shown that IR luminescence sensitization of Ag₂S/TGA QDs with an average size of 3.7 nm in the region of 1040 nm is possible due to non-radiative resonance energy transfer from Ag₂S/TGA QDs with an average size of 2.2 nm and luminescence peak at 900 nm using ICG J-aggregate as an exciton bridge. The sensitization efficiency is 0.33. This technique provides a transition from the first therapeutic window (NIR-I, 700-950 nm) to the second (NIR-II, 1000-1700 nm). It can allow high to increase the imaging in vivo resolution.

Novel Nanohybrids Based on Supramolecular Assemblies of Meso-tetrakis-(4-sulfonatophenyl) Porphyrin J-aggregates and Amine-Functionalized Carbon Nanotubes

The ability of multiwalled carbon nanotubes (MWCNTs) covalently functionalized with polyamine chains of different length (ethylenediamine, EDA and tetraethylenepentamine, EPA) to induce the J-aggregation of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) was investigated in different experimental conditions. Under mild acidic conditions, protonated amino groups allow for the assembly by electrostatic interaction with the diacid form of TPPS, leading to hybrid nanomaterials. The presence of only one pendant amino group for a chain in EDA does not lead to any aggregation, whereas EPA (with four amine groups for chain) is effective in inducing J-aggregation using different mixing protocols. These nanohybrids have been characterized through UV/Vis extinction, fluorescence emission, resonance light scattering and circular dichroism spectroscopy. Their morphology and chemical composition have been elucidated through transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). TEM and STEM analysis evidence single or bundles of MWCNTs in contact with TPPS J-aggregates nanotubes. The nanohybrids are quite stable for days, even in aqueous solutions mimicking physiological medium (NaCl 0.15 M). This property, together with their peculiar optical features in the therapeutic window of visible spectrum, make them potentially useful for biomedical applications.

Liposome-Templated Indocyanine Green J- Aggregates for In Vivo Near-Infrared Imaging and Stable Photothermal Heating

Indocyanine green (ICG) is an FDA-approved near-infrared fluorescent dye that has been used in optical imaging and photothermal therapy. Its rapid in vivo clearance and photo-degradation have limited its application. ICG pharmacokinetics and biodistribution have been improved via liposomal encapsulation, while its photothermal stability has been enhanced by ICG J-aggregate (IJA) formation. In the present work, we report a simple approach to engineer a nano-sized, highly stable IJA liposomal formulation. Our results showed that lipid film hydration and extrusion method led to efficient IJA formation in rigid DSPC liposomes, as supported by molecular dynamics modeling. The engineered DSPC-IJA formulation was nano-sized, and with spectroscopic and photothermal properties comparable to free IJA. Promisingly, DSPC-IJA exhibited high fluorescence, which enabled its in vivo tracking, showing prolonged blood circulation and significantly higher tumor fluorescence signals, compared to free ICG and IJA. Furthermore, DSPC-IJA demonstrated high photo-stability in vivo after multiple cycles of 808 nm laser irradiation. Finally, doxorubicin was loaded into liposomal IJA to utilize the co-delivery capabilities of liposomes. In conclusion, with both liposomes and ICG being clinically approved, our novel liposomal IJA could offer a clinically relevant theranostic platform enabling multimodal imaging and combinatory chemo- and photothermal cancer therapy.