Stable ICG-loaded upconversion nanoparticles: silica core/shell theranostic nanoplatform for dual-modal upconversion and photoacoustic imaging together with photothermal therapy

In situ modified mesoporous silica nanoparticles: synthesis, properties and theranostic applications

Over the last 20 years, mesoporous silica nanoparticles (MSNs) have drawn considerable attention in the biomedical field due to their large surface area, porous network, biocompatibility, and abundant modification possibilities. In situ MSN modification refers to the incorporation of materials such as alkoxysilanes, ions and nanoparticles (NPs) in the silica matrix during synthesis. Matrix modification is a popular approach for endowing MSNs with additional functionalities such as imaging properties, bioactivity, and degradability, while leaving the mesopores free for drug loading. As such, in situ modified MSNs are considered promising theranostic agents. This review provides an extensive overview of different materials and modification strategies that have been used and their effect on MSN properties. We also highlight how in situ modified MSNs have been applied in theranostic applications, oncology and regenerative medicine. We conclude with perspectives on the future outlooks and current challenges for the widespread clinical use of in situ modified MSNs.

NIR-Triggered Release of Nitric Oxide by Upconversion-Based Nanoplatforms to Enhance Osteogenic Differentiation of Mesenchymal Stem Cells for Osteoporosis Therapy

Stem cell therapy is an attractive approach to bone tissue regeneration in osteoporosis (OP); however, poor cell engraftment and survival within injured tissues limits its success in clinical settings. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes, with emerging evidence supporting its diverse roles in modulating stem cell behavior, including survival, migration, and osteogenic differentiation. To control and enhance osteogenic differentiation of mesenchymal stem cells (MSCs) for OP therapy, we designed a near-infrared (NIR) light-triggered NO-releasing nanoplatform based on upconversion nanoparticles (UCNPs) that converts 808-nm NIR light into visible light, stimulating NO release by light control. We demonstrate that the UCNP nanoplatforms can encapsulate a light-sensitive NO precursor, Roussin's black salt (RBS), through the implementation of a surface mesoporous silica coating. Upon exposure to 808-nm irradiation, NO is triggered by the controlled upconversion of UCNP visible light at the desired time and location. This controlled release mechanism facilitates photoregulated differentiation of MSCs toward osteogenic lineage and avoids thermal effects and phototoxicity on cells, thus offering potential therapeutic applications for treating OP in vivo. Following the induction of osteogenic differentiation, the UCNP nanoplatforms exhibit the capability to serve as nanoprobes for the real-time detection of differentiation through enzymatic digestion and fluorescence recovery of UCNPs, enabling assessment of the therapeutic efficacy of OP treatment. Consequently, these UCNP-based nanoplatforms present a novel approach to control and enhance osteogenic differentiation of MSCs for OP therapy, simultaneously detecting osteogenic differentiation for evaluating treatment effectiveness.

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.

Enhancement of enzyme activity by laser-induced energy propulsion of upconverting nanoparticles under near-infrared light: A comprehensive methodology for in vitro and in vivo applications

If the appropriate immobilization method and carrier support are not selected, partial decreases in the activity of enzymes may occur after immobilization. Herein, to overcome this challenge, an excitation mechanism that enables energy transfer was proposed. Modified upconverting nanoparticles (UCNPs) were constructed and the important role of near-infrared (NIR) excitation in enhancing the catalytic activity of the enzyme was demonstrated. For this purpose, UCNPs were first synthesized via the hydrothermal method, functionalized with isocyanate groups, and then, PEG-L-ASNase was immobilized via covalent binding. UCNPs with and without PEG-L-ASNase were extensively characterized by different methods. These supports had immobilization yield and activity efficiency of >96 % and 78 %, respectively. Moreover, immobilized enzymes exhibited improved pH, thermal, and storage stability. In addition, they retained >65 % of their initial activity even after 20 catalytic cycles. Biochemical and histological findings did not indicate a trend of toxicity in rats due to UCNPs. Most importantly, PEG-L-ASNase activity was triggered approximately 5- and 2-fold under in vitro and in vivo conditions, respectively. Overall, it is anticipated that this pioneering work will shed new light on the realistic and promising usage of NIR-excited UCNPs for the immobilization of enzymes in expensive and extensive applications.

In vivo monitoring of hemodynamic changes in ischemic stroke using photoacoustic tomography

Ischemic stroke occurs when a blood vessel supplying the brain is blocked, leading to decreased blood flow. Early diagnosis and treatment are crucial. However, existing clinical imaging methods have limitations, such as safety issues and low time resolution. To address these challenges, we propose using photoacoustic tomography (PAT) with a contrast agent, known for its high resolution and contrast capabilities. Our study involved imaging brain vasculature in three groups: normal, unilateral common carotid artery ligation (UCAL), and middle cerebral artery occlusion (MCAO). On the ischemic stroke side, we observed reduced blood vessel density and hemodynamic changes were evident after injecting indocyanine green for PAT. The photoacoustic intensity was notably lower in the ligated sides of the UCAL and MCAO groups, with statistically significant differences between the three groups. This work highlights PAT's potential as a powerful tool for early diagnosis and guidance in ischemic stroke cases.

Achieving photostability in dye-sensitized upconverting nanoparticles and their use in Fenton type photocatalysis

Dye sensitization is a promising approach to enhance the luminescence of lanthanide-doped upconverting nanoparticles. However, the poor photostability of near-infrared dyes hampers their use in practical applications. To address this, commercial IR820 was modified for improved photostability and covalently bonded to amine-functionalized silica-coated LnUCNPs. Two methods of covalent linking were investigated: linking the dye to the surface of the silica shell, and embedding the dye within the silica shell. The photostability of the dyes when embedded in the silica shell exhibited upconversion emissions from NaGdF4:Er3+,Yb3+/NaGdF4:Yb3+ nanoparticles for over four hours of continuous excitation with no change in intensity. To highlight this improvement, the photostable dye-embedded system was successfully utilized for Fenton-type photocatalysis, emphasizing its potential for practical applications. Overall, this study presents a facile strategy to circumvent the overlooked limitations associated with photodegradation, opening up new possibilities for the use of dye-sensitized lanthanide-doped upconverting nanoparticles in a range of fields.

A Photomodulable Bacteriophage-Spike Nanozyme Enables Dually Enhanced Biofilm Penetration and Bacterial Capture for Photothermal-Boosted Catalytic Therapy of MRSA Infections

Nanozymes, featuring intrinsic biocatalytic effects and broad-spectrum antimicrobial properties, are emerging as a novel antibiotic class. However, prevailing bactericidal nanozymes face a challenging dilemma between biofilm penetration and bacterial capture capacity, significantly impeding their antibacterial efficacy. Here, this work introduces a photomodulable bactericidal nanozyme (ICG@hMnOx ), composed of a hollow virus-spiky MnOx nanozyme integrated with indocyanine green, for dually enhanced biofilm penetration and bacterial capture for photothermal-boosted catalytic therapy of bacterial infections. ICG@hMnOx demonstrates an exceptional capability to deeply penetrate biofilms, owing to its pronounced photothermal effect that disrupts the compact structure of biofilms. Simultaneously, the virus-spiky surface significantly enhances the bacterial capture capacity of ICG@hMnOx . This surface acts as a membrane-anchored generator of reactive oxygen species and a glutathione scavenger, facilitating localized photothermal-boosted catalytic bacterial disinfection. Effective treatment of methicillin-resistant Staphylococcus aureus-associated biofilm infections is achieved using ICG@hMnOx , offering an appealing strategy to overcome the longstanding trade-off between biofilm penetration and bacterial capture capacity in antibacterial nanozymes. This work presents a significant advancement in the development of nanozyme-based therapies for combating biofilm-related bacterial infections.

Organic Photothermal Cocrystals: Rational Design, Controlled Synthesis, and Advanced Application

Organic photothermal cocrystals, integrating the advantages of intrinsic organic cocrystals and the fascinating photothermal conversion ability, hold attracted considerable interest in both basic science and practical applications, involving photoacoustic imaging, seawater desalination, and photothermal therapy, and so on. However, these organic photothermal cocrystals currently suffer individual cases discovered step by step, as well as the deep and systemic investigation in the corresponding photothermal conversion mechanisms is rarely carried out, suggesting a huge challenge for their further developments. Therefore, it is urgently necessary to investigate and explore the rational design and synthesis of high-performance organic photothermal cocrystals for future applications. This review first and systematically summarizes the organic photothermal cocrystal in terms of molecular classification, the photothermal conversion mechanism, and their corresponding applications. The timely interpretation of the cocrystal photothermal effect will provide broad prospects for the purposeful fabrication of excellent organic photothermal cocrystals toward great efficiency, low cost, and multifunctionality.

Advances in Single-component inorganic nanostructures for photoacoustic imaging guided photothermal therapy

Phototheranostic based on photothermal therapy (PTT) and photoacoustic imaging (PAI), as one of avant-garde medical techniques, have sparked growing attention because it allows noninvasive, deeply penetrative, and highly selective and effective therapy. Among a variety of phototheranostic nanoagents, single-component inorganic nanostructures are found to be novel and attractive PAI and PTT combined nanotheranostic agents and received tremendous attention, which not only exhibit structural controllability, high tunability in physiochemical properties, size-dependent optical properties, high reproducibility, simple composition, easy functionalization, and simple synthesis process, but also can be endowed with multiple therapeutic and imaging functions, realizing the superior therapy result along with bringing less foreign materials into body, reducing systemic side effects and improving the bioavailability. In this review, according to their synthetic components, conventional single-component inorganic nanostructures are divided into metallic nanostructures, metal dichalcogenides, metal oxides, carbon based nanostructures, upconversion nanoparticles (UCNPs), metal organic frameworks (MOFs), MXenes, graphdiyne and other nanostructures. On the basis of this category, their detailed applications in PAI guide PTT of tumor treatment are systematically reviewed, including synthesis strategies, corresponding performances, and cancer diagnosis and therapeutic efficacy. Before these, the factors to influence on photothermal effect and the principle of in vivo PAI are briefly presented. Finally, we also comprehensively and thoroughly discussed the limitation, potential barriers, future perspectives for research and clinical translation of this single-component inorganic nanoagent in biomedical therapeutics.

Medical Imaging Technology and Imaging Agents

Medical imaging is a technology that studies the interaction between human body and irradiations of X-ray, ultrasound, magnetic field, etc. and represents anatomical structures of human organs/tissues with the implication of irradiation attenuation in the form of grayscales. With these medical images, detailed information on health status and disease diagnosis may be judged by clinical physicians to determine an appropriate therapy approach. This chapter will give a systematic introduction on the modalities, classifications, basic principles, and biomedical applications of traditional medical imaging along with the types, construction, and major features of the corresponding contrast agents or imaging probes.

Bioimaging with Upconversion Nanoparticles

Bioimaging enables the spatiotemporal visualization of biological processes at various scales empowered by a range of different imaging modalities and contrast agents. Upconversion nanoparticles (UCNPs) represent a distinct type of such contrast agents with the potential to transform bioimaging due to their unique optical properties and functional design flexibilities. This review explores and discusses the opportunities, challenges, and limitations that UCNPs exhibit as bioimaging probes and highlights applications with spatial dimensions ranging from the single nanoparticle level to cellular, tissue, and whole animal imaging. We further summarized recent advancements in bioimaging applications enabled by UCNPs, including super-resolution techniques and multimodal imaging methods, and provide a perspective on the future potential of UCNP-based technologies in bioimaging research and clinical translation. This review may provide a valuable resource for researchers interested in exploring and applying UCNP-based bioimaging technologies.

Nanocomposites based on lanthanide-doped upconversion nanoparticles: diverse designs and applications

Lanthanide-doped upconversion nanoparticles (UCNPs) have aroused extraordinary interest due to the unique physical and chemical properties. Combining UCNPs with other functional materials to construct nanocomposites and achieve synergistic effect abound recently, and the resulting nanocomposites have shown great potentials in various fields based on the specific design and components. This review presents a summary of diverse designs and synthesis strategies of UCNPs-based nanocomposites, including self-assembly, in-situ growth and epitaxial growth, as well as the emerging applications in bioimaging, cancer treatments, anti-counterfeiting, and photocatalytic fields. We then discuss the challenges, opportunities, and development tendency for developing UCNPs-based nanocomposites.

Boosting Near-Infrared Photothermal Conversion by Intermolecular Interactions in Isomeric Cocrystals

Organic cocrystal exhibits excellent photothermal conversion (PTC), but how the intermolecular interactions of cocrystals regulate the PTC is obscure. Here, two isomeric donor molecules (phenanthrene and anthracene) and two electron-withdrawing molecules (7,7,8,8,8-tetracyanodimethylquinone and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinone dimethane) are self-assembled into the four cocrystals (PTQ, PFQ, ATQ, and AFQ). By changing the molecular configuration of the donor and the electron-withdrawing ability of the acceptor, the intrinsic influencing factors of the intermolecular interaction on the PTC were explored. Under near-infrared laser (808 nm) irradiation, the PTC efficiencies of PTQ, PFQ, AFQ, and ATQ are 35.85, 44.74, 57.00, and 60.53%, respectively. Based on the single-crystal X-ray diffraction, ultrafast time-resolved transient absorption, and excited-state theoretical calculations, we found that the π-π stacking in ATQ and AFQ is conducive to promoting the near-infrared light-harvesting ability and the p-π interaction of cocrystals can regulate the nonradiative rotation of -C(C≡N)₂ groups, resulting in a tunable near-infrared PTC via the isomeric cocrystals. Accordingly, the evaporation rate of the porous polyurethane-AFQ foam can reach 1.33 kg·m^-2·h^-1 in the simulated solar-driven water evaporation system. This work provides a strategy to boost the PTC by the intermolecular interactions of cocrystal materials.

Facets of optically and magnetically induced heating in ferromagnetically doped-NaYF4 particles

Upconverting particles like Yb and Er-doped NaYF₄ are known to heat up after illumination with light at pump wavelength due to inefficient upconversion processes. Here we show that NaYF₄ particles which have been co-doped not only with Yb and Er but also Fe improves the photothermal conversion efficiency. In addition, we show for the first time that alternating magnetic fields also heat up the ferromagnetic particles. Thereafter we show that a combination of optical and magnetic stimuli significantly increases the heat generated by the particles.

Extracellular vesicles with high dual drug loading for safe and efficient combination chemo-phototherapy

Extracellular vesicles (EVs) have emerged as biocompatible nanocarriers for efficient delivery of various therapeutic agents, with intrinsic long-term blood circulatory capability and low immunogenicity. Here, indocyanine green (ICG)- and paclitaxel (PTX)-loaded EVs [EV(ICG/PTX)] were developed as a biocompatible nanoplatform for safe and efficient cancer treatment through near-infrared (NIR) light-triggered combination chemo/photothermal/photodynamic therapy. High dual drug encapsulation in EVs was achieved for both the hydrophilic ICG and hydrophobic PTX by simple incubation. The EVs substantially improved the photostability and cellular internalization of ICG, thereby augmenting the photothermal effects and reactive oxygen species production in breast cancer cells upon NIR light irradiation. Hence, ICG-loaded EVs activated by NIR light irradiation showed greater cytotoxic effects than free ICG. EV(ICG/PTX) showed the highest anticancer activity owing to the simultaneous chemo/photothermal/photodynamic therapy when compared with EV(ICG) and free ICG. In vivo study revealed that EV(ICG/PTX) had higher accumulation in tumors and improved pharmacokinetics compared to free ICG and PTX. In addition, a single intravenous administration of EV(ICG/PTX) exhibited a considerable inhibition of tumor proliferation with negligible systemic toxicity. Thus, this study demonstrates the potential of EV(ICG/PTX) for clinical translation of combination chemo-phototherapy.

The importance, status, and perspectives of hybrid lanthanide-doped upconversion nanothermometers for theranostics

Theranostics combines diagnostics and therapy in a single multifunctional system. Multifunctional upconversion luminescent lanthanide-doped nanothermometers for theranostic purposes offer non-invasive and sensitive multimodal performance in the biomedical field over traditional temperature measurement methods. Despite existing challenges, various studies on hybrid upconversion nanothermometers show substantial progress for (bio)imaging, temperature sensing, photodynamic and photothermal therapy, as well as drug delivery applications. The beauty of such an approach is that it unfolds possibilities to combine diagnostics and therapy in a single particle, which can modify the way certain diseases are treated, hence change the entire healthcare scene.

Nanoarchitectured prototypes of mesoporous silica nanoparticles for innovative biomedical applications

Despite exceptional morphological and physicochemical attributes, mesoporous silica nanoparticles (MSNs) are often employed as carriers or vectors. Moreover, these conventional MSNs often suffer from various limitations in biomedicine, such as reduced drug encapsulation efficacy, deprived compatibility, and poor degradability, resulting in poor therapeutic outcomes. To address these limitations, several modifications have been corroborated to fabricating hierarchically-engineered MSNs in terms of tuning the pore sizes, modifying the surfaces, and engineering of siliceous networks. Interestingly, the further advancements of engineered MSNs lead to the generation of highly complex and nature-mimicking structures, such as Janus-type, multi-podal, and flower-like architectures, as well as streamlined tadpole-like nanomotors. In this review, we present explicit discussions relevant to these advanced hierarchical architectures in different fields of biomedicine, including drug delivery, bioimaging, tissue engineering, and miscellaneous applications, such as photoluminescence, artificial enzymes, peptide enrichment, DNA detection, and biosensing, among others. Initially, we give a brief overview of diverse, innovative stimuli-responsive (pH, light, ultrasound, and thermos)- and targeted drug delivery strategies, along with discussions on recent advancements in cancer immune therapy and applicability of advanced MSNs in other ailments related to cardiac, vascular, and nervous systems, as well as diabetes. Then, we provide initiatives taken so far in clinical translation of various silica-based materials and their scope towards clinical translation. Finally, we summarize the review with interesting perspectives on lessons learned in exploring the biomedical applications of advanced MSNs and further requirements to be explored.

Low-temperature open-air synthesis of PVP-coated NaYF4:Yb,Er,Mn upconversion nanoparticles with strong red emission

Cubic (α-phase) NaYF₄:Yb,Er upconversion nanoparticles (UCNPs) are uniquely suited to biophotonics and biosensing applications due to their near-infrared excitation and visible red emission (λ _ex approx. 660 nm), enabling detection via thick overlying tissue with no bio-autofluorescence. However, UCNP synthesis typically requires high temperatures in combination with either high pressure reaction vessels or an inert atmosphere. Here, we report synthesis of α-phase NaYF₄:Yb,Er,Mn UCNPs via the considerably more convenient PVP40-mediated route; a strategy that requires modest temperatures and relatively short reaction time (160°C, 2 h) in open air, with Mn²⁺ co-doping serving to greatly enhance red emission. The optimal Mn²⁺ co-doping level was found to be 35 mol %, which decreased the average maximum UCNP Feret diameter from 42 ± 11 to 36 ± 15 nm; reduced the crystal lattice parameter, a, from 5.52 to 5.45 Å; and greatly enhanced UCNP red/green emission ratio in EtOH by a factor of 5.6. The PVP40 coating enabled dispersal in water and organic solvents and can be exploited for further surface modification (e.g. silica shell formation). We anticipate that this straightforward UCNP synthesis method for producing strongly red-emitting UCNPs will be particularly beneficial for deep tissue biophotonics and biosensing applications.

Emerging indocyanine green-integrated nanocarriers for multimodal cancer therapy: a review

Nanotechnology is a branch of science dealing with the development of new types of nanomaterials by several methods. In the biomedical field, nanotechnology is widely used in the form of nanotherapeutics. Therefore, the current biomedical research pays much attention to nanotechnology for the development of efficient cancer treatment. Indocyanine green (ICG) is a near-infrared tricarbocyanine dye approved by the Food and Drug Administration (FDA) for human clinical use. ICG is a biologically safe photosensitizer and it can kill tumor cells by producing singlet oxygen species and photothermal heat upon NIR irradiation. ICG has some limitations such as easy aggregation, rapid aqueous degradation, and a short half-life. To address these limitations, ICG is further formulated with nanoparticles. Therefore, ICG is integrated with organic nanomaterials (polymers, micelles, liposomes, dendrimers and protein), inorganic nanomaterials (magnetic, gold, mesoporous, calcium, and LDH based), and hybrid nanomaterials. The combination of ICG with nanomaterials provides highly efficient therapeutic effects. Nowadays, ICG is used for various biomedical applications, especially in cancer therapeutics. In this review, we mainly focus on ICG-based combined cancer nanotherapeutics for advanced cancer treatment.

Gold nanostructures as mediators of hyperthermia therapies in breast cancer

Breast cancer is the leading cause of cancer-related deaths among women. Due to the limitations of the current therapeutics, new treatment options are needed. Hyperthermia is a promising approach to improve breast cancer therapy, particularly when combined with chemo and radiotherapy. This area has gained more attention following association with nanotechnology, with the emergence of modalities, such as photothermal therapy (PTT). PTT is a simple, minimally invasive technique that requires a near infrared (NIR) light source and a PTT agent. Gold nanostructures are excellent PTT agents as they offer biocompatibility, versatility, high photothermal conversion efficiency, imaging contrast and an easily-modified surface. In this review, we describe the molecular basis and the current clinical aspects of hyperthermia-based therapies. The emergent area of nanoparticle-induced hyperthermia will be explored, in particular gold nanostructure-mediated PTT, focusing on recent preclinical studies for breast cancer management.

Multifunctional theranostic nanoparticles for biomedical cancer treatments - A comprehensive review

Modern-day search for the novel agents (their preparation and consequent implementation) to effectively treat the cancer is mainly fuelled by the historical failure of the conventional treatment modalities. Apart from that, the complexities such as higher rate of cell mutations, variable tumor microenvironment, patient-specific disparities, and the evolving nature of cancers have made this search much stronger in the latest times. As a result of this, in about two decades, the theranostic nanoparticles (TNPs) - i.e., nanoparticles that integrate therapeutic and diagnostic characteristics - have been developed. The examples for TNPs include mesoporous silica nanoparticles, luminescence nanoparticles, carbon-based nanomaterials, metal nanoparticles, and magnetic nanoparticles. These TNPs have emerged as single and powerful cancer-treating multifunctional nanoplatforms, as they widely provide the necessary functionalities to overcome the previous/conventional limitations including lack of the site-specific delivery of anti-cancer drugs, and real-time continuous monitoring of the target cancer sites while performing therapeutic actions. This has been mainly possible due to the association of the as-developed TNPs with the already-available unique diagnostic (e.g., luminescence, photoacoustic, and magnetic resonance imaging) and therapeutic (e.g., photothermal, photodynamic, hyperthermia therapy) modalities in the biomedical field. In this review, we have discussed in detail about the recent developments on the aforementioned important TNPs without/with targeting ability (i.e., attaching them with ligands or tumor-specific antibodies) and also the strategies that are implemented to increase their tumor accumulation and to enhance their theranostic efficacies for effective biomedical cancer treatments.

Hybrid Hierarchical Heterostructures of Nanoceramic Phosphors as Imaging Agents for Multiplexing and Living Cancer Cells Translocation

Existing fluorescent labels used in life sciences are based on organic compounds with limited lifetime or on quantum dots which are either expensive or toxic and have low kinetic stability in biological environments. To address these challenges, luminescent nanomaterials have been conceived as hierarchical, core–shell structures with spherical morphology and highly controlled dimensions. These tailor-made nanophosphors incorporate Ln:YVO₄ nanoparticles (Ln = Eu(III) and Er(III)) as 50 nm cores and display intense and narrow emission maxima centered at ∼565 nm. These cores can be encapsulated in silica shells with highly controlled dimensions as well as functionalized with chitosan or PEG5000 to reduce nonspecific interactions with biomolecules in living cells. Confocal fluorescence microscopy in living prostate cancer cells confirmed the potential of these platforms to overcome the disadvantages of commercial fluorophores and their feasibility as labels for multiplexing, biosensing, and imaging in life science assays.

Stabilization of indocyanine green dye in polymeric micelles for NIR-II fluorescence imaging and cancer treatment

One of the most commonly used near infrared (NIR) dyes is indocyanine green (ICG), which has been extensively used for NIR bioimaging, photothermal and photodynamic therapy. However, upon excitation this dye can react with molecular oxygen to form singlet oxygen (SO), which can then cleave ICG to form non-fluorescent debris. In order to reduce the reaction between ICG and oxygen, we used energy transfer (ET) between the former and the NIR dye IR-1061. The two dyes were encapsulated in micelles composed of biocompatible poly(ethylene glycol)-block-poly(ε-caprolactone) (PCL-PEG). Micelles were characterized for their size using dynamic light scattering (DLS) and were found to measure about 35 nm in diameter. Fluorescence emission measurements were conducted to show that the stability of ICG against photodecomposition is increased. Moreover, this increased stability allows the encapsulated dye to generate more heat and for a longer time, compared to its free form. Studies with a SO indicator showed that as more IR-1061 is added to the micelles, less SO is produced. These results show how by changing the amount of added IR-1061 it is possible to tune the heat and SO generated by the system. Cell viability studies demonstrated that while particles were nontoxic under physiological conditions, upon 808 nm irradiation they become potent at eradicating MCF7 cancer cells. Moreover, it was demonstrated that both the increase of temperature and the creation of decomposition debris play a role in the cytotoxic efficacy of the micelles. Dye-loaded micelles that were injected to live mice showed bright fluorescence in the over 1000 nm NIR (OTN-NIR) region, allowing for visualization of blood vessels and internal organs. Most importantly, the encapsulated dyes remained stable for over 30 minutes, gradually accumulating in the liver and spleen. The presence of IR-1061 in addition to the heat-generating dye ICG allowed for simultaneous temperature modification and monitoring. We were able to assess the change in temperature by measuring the change in the fluorescence intensity of IR-1061 in the OTN-NIR region, a range with deep penetration of living tissues. These features illustrate the potential use of ICG/IR-1061 in PCL-PEG micelles as promising candidates for cancer treatment and diagnosis.

Mesoporous Silica Nanoparticles as Theranostic Antitumoral Nanomedicines

Nanoparticles have become a powerful tool in oncology not only as carrier of the highly toxic chemotherapeutic drugs but also as imaging contrast agents that provide valuable information about the state of the disease and its progression. The enhanced permeation and retention effect for loaded nanocarriers in tumors allow substantial improvement of selectivity and safety of anticancer nanomedicines. Additionally, the possibility to design stimuli-responsive nanocarriers able to release their payload in response to specific stimuli provide an excellent control on the administered dosage. The aim of this review is not to present a comprehensive revision of the different theranostic mesoporous silica nanoparticles (MSN) which have been published in the recent years but just to describe a few selected examples to offer a panoramic view to the reader about the suitability and effectiveness of these nanocarriers in the oncology field.

A Hybrid Organo-Nanotheranostic Platform of Superlative Biocompatibility for Near-Infrared-Triggered Fluorescence Imaging and Synergistically Enhanced Ablation of Tumors

The quest for an all-organic nanosystem with negligible cytotoxicity and remarkable in vivo tumor theranostic capability is inescapably unending. Hitherto, the landscape of available photothermal agents is dominated by metal-based nanoparticles (NPs) with attendant in vivo negatives. Here, an all-organic-composed theranostic nanosystem with outstanding biocompatibility for fluorescence image-guided tumor photothermal therapy, and as a potential alternative to metal-based photothermal agents is developed. This is rationally achieved by compartmentalizing indocyanine green (ICG) in glycol chitosan (GC)-polypyrrole (PP) nanocarrier to form hybrid ICG@GC-PP NPs (≈65 nm). The compartmentalization strategy, alongside the high photothermal conversion ability of PP jointly enhances the low photostability of free ICG. Advantageously, ICG@GC-PP is endowed with an impeccable in vivo performance by the well-known biocompatibility track records of its individual tri organo-components (GC, PP, and ICG). As a proof of concept, ICG@GC-PP NPs enables a sufficiently prolonged tumor diagnosis by fluorescence imaging up to 20 h post-injection. Furthermore, owing to the complementary heating performances of PP and ICG, ICG@GC-PP NPs-treated mice by one-time near-infrared irradiation exhibit total tumor regression within 14 days post-treatment. Therefore, leveraging the underlying benefits of this study will help to guide the development of new all-organic biocompatible systems in synergism, for safer tumor theranostics.

ICG-Loaded PEGylated BSA-Silver Nanoparticles for Effective Photothermal Cancer Therapy

Purpose

Indocyanine green (ICG), a near infrared (NIR) dye clinically approved in medical diagnostics, possesses great heat conversion efficiency, which renders itself as an effective photosensitizer for photothermal therapy (PTT) of cancer. However, there remain bottleneck challenges for use in PTT, which are the poor photo and plasma stability of ICG. To address these problems, in this research, ICG-loaded silver nanoparticles were prepared and evaluated for the applicability as an effective agent for photothermal cancer therapy.

Methods and Results

PEGylated bovine serum albumin (BSA)-coated silver core/shell nanoparticles were synthesized with a high loading of ICG (“PEG-BSA-AgNP/ICG”). Physical characterization was carried out using size analyzer, transmission electron microscopy, and Fourier transform infrared spectrophotometry to identify successful preparation and size stability. ICG-loading content and the photothermal conversion efficiency of the particles were confirmed with inductively coupled plasma mass spectrometry and laser instruments. In vitro studies showed that the PEG-BSA-AgNP/ICG could provide great photostability for ICG, and their applicability for PTT was verified from the cellular study results. Furthermore, when the PEG-BSA-AgNP/ICG were tested in vivo, study results exhibited that ICG could stably remain in the blood circulation for a markedly long period (plasma half-life: 112 min), and about 1.7% ID/g tissue could be accumulated in the tumor tissue at 4 h post-injection. Such nanoparticle accumulation in the tumor enabled tumor surface temperature to be risen to 50°C (required for photo-ablation) by laser irradiation and led to successful inhibition of tumor growth in the B16F10 s.c. syngeneic nude mice model, with minimal systemic toxicity.

Conclusion

Our findings demonstrated that PEG-BSA-AgNPs could serve as effective carriers for delivering ICG to the tumor tissue with great stability and safety.

Indocyanine Green Nanoparticles: Are They Compelling for Cancer Treatment?

Indocyanine green (ICG) is a Food and Drug Administration–approved near-infrared fluorescent dye, employed as an imaging agent for different clinical applications due to its attractive physicochemical properties, high sensitivity, and safety. However, free ICG suffers from some drawbacks, such as relatively short circulation half-life, concentration-dependent aggregation, and rapid clearance from the body, which would confine its feasible application in oncology. Here, we aim to discuss encapsulation of ICG within a nanoparticle formulation as a strategy to overcome some of its current limitations and to enlarge its possible applications in cancer diagnosis and treatment. Our purpose is to provide a short but exhaustive overview of clinical outcomes that these nanocomposites would provide, discussing opportunities, limitations, and possible impacts with regard to the main clinical needs in oncology.

Indocyanine Green Loaded Modified Mesoporous Silica Nanoparticles as an Effective Photothermal Nanoplatform

Photothermal therapy possesses great advantages for the treatment of drug-resistant tumors. Herein, Near Infrared (NIR)-triggered photothermal nanoparticles were developed through loading indocyanine green (ICG), a kind of NIR dye, into amino group-modified silica nanoparticles (SiO₂-NH₂ NPs). SiO₂-NH₂ NPs were prepared with immobilization of the amino groups into the framework of silica nanoparticles (SiO₂ NPs) by employing (3-aminopropyl)-triethoxysilane (APTES). Before and after the modification of the amino group, the particle sizes of SiO₂ NPs showed similar value, around 100 nm. ICG was further adsorbed into SiO₂-NH₂ NPs by electrostatic attraction to enable SiO₂-NH₂@ICG NPs as a kind of photothermal agent. The loading rate of ICG to SiO₂-NH₂ was greatly increased compared to unmodified SiO₂, and the stability of ICG was also improved. Moreover, the SiO₂-NH₂@ICG NPs exhibited efficient photothermal effects due to ICG transforming laser power into local heat through the connected ICG, when NIR laser irradiation turned on for a couple of minutes. Finally, the in vitro antitumor efficacy of SiO₂-NH₂@ICG NPs was investigated by recording cell proliferation rate and further chronicled the apoptotic morphology evidence by a Calcein-AM/PI fluorescent staining assay, indicating the efficient photothermal targeted therapy for the HepG2 tumor cells.

SiO2@Cu7S4 nanotubes for photo/chemodynamic and photo-thermal dual-mode synergistic therapy under 808 nm laser irradiation

Photodynamic therapy (PDT) is a light-based modality for tumor treatment that involves the generation of reactive oxygen species (ROS) by the combination of light, a photosensitizer, and molecular oxygen. Nevertheless, the therapeutic effects of PDT are limited by hypoxic conditions that worsen with oxygen consumption during the PDT process. Photo/chemodynamic therapy (PCDT) based on the Fenton reaction is one strategy to improve ROS generation, provided a highly effective Fenton reagent is developed. In this research, SiO₂@Cu₇S₄ nanotubes (NTs) were synthesized as a PCDT agent. This double-valence metal-sulfide composite material can react with H₂O₂ at the tumor site. SiO₂@Cu₇S₄ NTs can produce more ROS than the traditional PDT agents, and besides, they can also be used as a photothermal therapy (PTT) agent. SiO₂@Cu₇S₄ NTs will trigger the PTT effect under 808 nm irradiation and generate a large amount of heat to eradicate cancer cells. This heat will also promote the PCDT effect by increasing the reaction rate. Thus, the SiO₂@Cu₇S₄ NT is a suitable material for PCDT and PTT synergistic oncotherapy. The 808 nm laser is selected as the appropriate excitation source, providing adequate penetration and minimal harm to normal cells. The experimental data presented herein demonstrate the promising photosensitive, Fenton-like, and photothermal performance of SiO₂@Cu₇S₄ NTs. Furthermore, the findings could promote the development of PCDT and PTT synergistic therapy. Thus, this research provides a feasible method to design a single, multifunctional material for cancer treatment.

Efficient photoacoustic imaging using indocyanine green (ICG) loaded functionalized mesoporous silica nanoparticles

Photoacoustic (PA) imaging is gaining momentum due to its greater depth of field, low background, and 3D imaging capabilities. However, traditional PA imaging agents (e.g. dyes, quantum dots, etc.) are usually unstable in plasma and bind to serum proteins, and thus cleared rapidly. Because of this, the nanoparticle encapsulation of PA imaging agents is becoming increasingly popular. Therefore, the rational design of carrier nanoparticles for this purpose is necessary for strong imaging signal intensity, high biosafety, and precise targeting. Herein, we systematically evaluate the influence of the chemical and physical surface functionalization of mesoporous silica nanoparticles (MSNs) on the photo-stability, loading, release, and photoacoustic (PA) signal strength of the FDA approved small molecule contrast agent, indocyanine green (ICG). Chemical functionalization involved the modification of MSNs with silanes having amine (NH2) or phosphonate (PO3) terminal groups, whereas physical modifications were performed by capping the ICG loaded MSNs with lipid bilayer (LB) or layer-by-layer (LBL) polyelectrolyte coatings. The NH2-MSNs display the highest ICG mass loading capacity (16.5 wt%) with a limited release of ICG (5%) in PBS over 48 h, while PO3-MSNs only loaded ICG around 3.5 wt%. The physically modified MSNs (i.e. LBMSNs and LBLMSNs) were vacuum loaded resulting in approximately 9 wt% loading and less than 10% ICG release in 48 h. Pure ICG was highly photo-unstable and showed 20% reduction in photoluminescence (PL) within 3 h of exposure to 800 nm, while the ICG loaded onto functionalized MSNs did not photo-degrade. Among the tested formulations, NH2-MSNs and LBLMSNs presented 4-fold in vitro PA signal intensity enhancement at a 200 μg mL-1 equivalent ICG dose. Similar to the in vitro PA imaging, NH2-MSNs and LBLMSNs performed the best when subcutaneously injected into mouse cadavers with 1.29- and 1.43-fold PA signal enhancement in comparison to the pure ICG, respectively.

Construction of Multicolor Upconversion Nanotheranostic Agent for in-situ Cooperative Photodynamic Therapy for Deep-Seated Malignant Tumors

Upconversion nanoparticles (UCNPs)-based photodynamic nanotheranostic agents could address the main drawbacks of photosensitizer molecules (PSs) including instability in aqueous solution and rapid clearance. Due to the relatively weak luminescence intensity of UCNPs and insufficient reactive oxygen species (ROSs), UCNPs-based photodynamic therapy (UCNPs-PDT) was discounted for deep-seated tumors. Thus, we proposed a PSs-modulated sensitizing switch strategy. Indocyanine green (ICG) as an NIR organic dye was proved to effectively enhance the luminescence intensity of UCNPs. Herein, four-color UCNPs were coated with a silica layer which loaded ICG and PSs while the thickness of silica layer was controlled to assist the sensitization function of ICG and activation of PSs. Under the drive of mitochondria-targeting ligand, the prepared nanotheranostic agent would accumulate in the mitochondria where ROSs were in-situ produced and then cell apoptosis was induced. Due to the cooperative PDT and high tissue-penetration depth of NIR laser, the prepared upconversion nanotheranostic agent could achieve significant inhibition on the deep-seated tumors.

Photo-induced reactions for disassembling of coloaded photosensitizer and drug molecules from upconversion-mesoporous silica nanoparticles: An effective synergistic cancer therapy

Photodynamic therapy is an emerging noninvasive cancer treatment approach, which requires a photosensitizer (PS), light, and molecular oxygen. In this study, we have successfully fabricated a dual nature (pH- and reactive-oxygen-species-responsive) upconversion nanoparticles (UCNPs) to utilize coloaded doxorubicin (DOX) and chlorin e6 (Ce6) with high antitumor efficacy. The model anticancer drug (DOX) and PS (Ce6) were conjugated in a ratio of 1:1 (w:w), and then loaded on the surface of UCNPs@mesoporous silica (mSiO₂) (85.63 ± 9.87 nm). Cellular uptake could be achieved by either increased permeability or ionic effect of UCNPs@mSiO₂, where Ce6 controlled the DOX release under a near-infrared (NIR) laser irradiation at 980 nm. A cytotoxicity analysis revealed that the dual-responsive UCNPs@mSiO₂ could successfully deliver DOX and Ce6 at the tumor site, causing cell death with a high efficiency. This study shows that the modified UCNPs@mSiO₂ is a promising system to realize NIR-light-triggered PS and drug delivery approach to improve synergistic therapies in vitro and in vivo, in the future.

Neodymium-Sensitized Nanoconstructs for Near-Infrared Enabled Photomedicine

Neodymium (Nd³⁺ )-sensitized nanoconstructs have gained increasing attention in recent decades due to their unique properties, especially optical properties. The design of various Nd³⁺ -sensitized nanosystems is expected to contribute to medical and health applications, due to their advantageous properties such as high penetration depth, excellent photostability, non-photobleaching, low cytotoxicity, etc. However, the low conversion efficiency and potential long-term toxicity of Nd³⁺ -sensitized nanoconstructs are huge obstacles to their clinical translations. This review article summarizes three energy transfer pathways of all kinds of Nd³⁺ -sensitized nanoconstructs focusing on the properties of Nd³⁺ ions and discusses their recent potential applications as near-infrared (NIR) enabled photomedicine. This review article will contribute to the design and fabrication of novel Nd³⁺ -sensitized nanoconstructs for NIR-enabled photomedicine, aiming for potentially safer and more efficient designs to get closer to clinical usage.

Indocyanine green modified silica shells for colon tumor marking

Marking colon tumors for surgery is normally done with the use of India ink. However, non-fluorescent dyes such as India ink cannot be imaged below the tissue surface and there is evidence for physiological complications such as abscess, intestinal perforation and inconsistency of dye injection. A novel infrared marker was developed using FDA approved indocyanine green (ICG) dye and ultrathin hollow silica nanoshells (ICG/HSS). Using a positively charged amine linker, ICG was non-covalently adsorbed onto the nanoparticle surface. For ultra-thin wall 100 nm diameter silica shells, a bimodal ICG layer of < 3 nm is was formed. Conversely, for thicker walls on 2 μm diameter silica shells, the ICG layer was only bound to the outer surface and was 6 nm thick. In vitro testing of fluorescent emission showed the particles with the thinner coating were considerably more efficient, which is consistent with self-quenching reducing emission shown in the thicker ICG coatings. Ex-vivo testing showed that ICG bound to the 100 nm hollow silica shells was visible even under 1.5 cm of tissue. In vivo experiments showed that there was no diffusion of the ICG/nanoparticle marker in tissue and it remained imageable for as long as 12 days.

Antimonene Nanoflakes: Extraordinary Photoacoustic Performance for High-Contrast Imaging of Small Volume Tumors

Photoacoustic imaging (PAI) has evolved to a stage that high-performance exogeneous contrast agents are urgently needed for imminent biomedical and clinical applications. Given that a material meets the basic criteria of efficient photoacoustic conversion, high biocompatibility, and fast excretion, great effort has been devoted to evaluating various materials for developing advantageous contrast agents to explore the full potentials of PAI. One focus is through modification of the current agents to boost their PA performance; whilst the other focus is to develop novel agents. Antimonene (AM) has emerged as a promising candidate for next generation of electronics among 2D materials due to its outstanding properties. Herein, it is reported that liquid-phase exfoliated antimonene exhibits extraordinary photoacoustic performance, which is not only more advantageous than other 2D materials, such as black phosphorus, graphene oxide, and transition metal dichalcogenides, but also superior to the commonly used PA contrast agents, such as ICG and gold nanorods. An insight analysis reveals that the unique thermal property of AM, including intrinsic low thermal conductivity and the morphology-related high interfacial thermal conductivity, might interpret the high photothermal conversion efficiency, and thus the excellent photoacoustic performance. The prodigious performance allows sensitive monitoring of intracellular events and high-quality in vivo tumor imaging.

Leveraging the interplay of nanotechnology and neuroscience: Designing new avenues for treating central nervous system disorders

Nanotechnology has the potential to open many novel diagnostic and treatment avenues for disorders of the central nervous system (CNS). In this review, we discuss recent developments in the applications of nanotechnology in CNS therapies, diagnosis and biology. Novel approaches for the diagnosis and treatment of neuroinflammation, brain dysfunction, psychiatric conditions, brain cancer, and nerve injury provide insights into the potential of nanomedicine. We also highlight nanotechnology-enabled neuroscience techniques such as electrophysiology and intracellular sampling to improve our understanding of the brain and its components. With nanotechnology integrally involved in the advancement of basic neuroscience and the development of novel treatments, combined diagnostic and therapeutic applications have begun to emerge. Nanotheranostics for the brain, able to achieve single-cell resolution, will hasten the rate in which we can diagnose, monitor, and treat diseases. Taken together, the recent advances highlighted in this review demonstrate the prospect for significant improvements to clinical diagnosis and treatment of a vast array of neurological diseases. However, it is apparent that a strong dialogue between the nanoscience and neuroscience communities will be critical for the development of successful nanotherapeutics that move to the clinic, benefit patients, and address unmet needs in CNS disorders.

Precise cell behaviors manipulation through light-responsive nano-regulators: recent advance and perspective

Nanotechnology-assisted spatiotemporal manipulation of biological events holds great promise in advancing the practice of precision medicine in healthcare systems. The progress in internal and/or external stimuli-responsive nanoplatforms for highly specific cellular regulations and theranostic controls offer potential clinical translations of the revolutionized nanomedicine. To successfully implement this new paradigm, the emerging light-responsive nanoregulators with unparalleled precise cell functions manipulation have gained intensive attention, providing UV-Vis light-triggered photocleavage or photoisomerization studies, as well as near-infrared (NIR) light-mediated deep-tissue applications for stimulating cellular signal cascades and treatment of mortal diseases. This review discusses current developments of light-activatable nanoplatforms for modulations of various cellular events including neuromodulations, stem cell monitoring, immunomanipulation, cancer therapy, and other biological target intervention. In summary, the propagation of light-controlled nanomedicine would place a bright prospect for future medicine.

Mass production of poly(ethylene glycol) monooleate-modified core-shell structured upconversion nanoparticles for bio-imaging and photodynamic therapy

Developing robust and high-efficient synthesis approaches has significant importance for the expanded applications of upconversion nanoparticles (UCNPs). Here, we report a high-throughput synthesis strategy to fabricate water-dispersible core-shell structured UCNPs. Firstly, we successfully obtain more than 10 grams core UCNPs with high quality from one-pot reaction using liquid rare-earth precursors. Afterwards, different core-shell structured UCNPs are fabricated by successive layer-by-layer strategy to get enhanced fluorescence property. Finally, the hydrophobic UCNPs are modified with poly(ethylene glycol) monooleate (PEG-OA) though a novel physical grinding method. On the basis of mass-production, we use the as-prepared PEG-UCNPs to construct an 808-nm stimuli photodynamic therapy agent, and apply them in cancer therapy and bio-imaging.

Color-Tunable Upconversion in Er3+/Yb3+-Codoped KLaF4 Nanophosphors by Incorporation of Tm3+ Ions for Biological Applications

Heavily doped nanocrystals of host KLaF4 with rare earth (RE3+ = Er3+, Tm3+, and Yb3+) ions prepared by a simple one-step template-free wet-chemical route have been reported. Prepared KLaF4 nanocrystals reveal phase-pure cubic structures (lattice constant a = 5.931Å) with space group Fm3m. Precisely defined molar ratios of heavily dopant RE3+ ions allow us to achieve wide color upconversion (UC) emission tunability (blue, green to yellow-orange-red) and white light, without any morphology and structure changes. The enhanced red emission by a factor of ∼120 has been achieved in 20% Yb3+ and 5% Tm3+ ions in KLaF4:1% Er3+ nanocrystals, which is due to an efficient sensitizer-acceptor (Yb3+ to Er3+ and Tm3+ ions) energy transfer and interexchange energy process between acceptors. For the first time, the key role of sensitizer (Yb3+) for UC emission energy transfer to Er3+ and/or Tm3+ is experimentally demonstrated. The evidence of upconversion photoluminescence excitation spectra reveals a broad safe biological excitation window (690-1040 nm), which can be well demonstrated by low-cost NIR diode lasers/LEDs. The applicability of these cubic nanophosphors is demonstrated as light-emitting polymer composite coatings and blocks for LEDs and solar cell panels. These well-dispersed UC nanocrystals can also be found to have greater use in bioimaging and spectral studies.

AgBiS2-TPP nanocomposite for mitochondrial targeting photodynamic therapy, photothermal therapy and bio-imaging under 808 nm NIR laser irradiation

AgBiS₂ nanodots as an NIR light-excited photosensitizer produce a PDT effect, which is reported for the first time.

Core-shell rare-earth-doped nanostructures in biomedicine

The current status of the use of core-shell rare-earth-doped nanoparticles in biomedical applications is reviewed in detail. The different core-shell rare-earth-doped nanoparticles developed so far are described and the most relevant examples of their application in imaging, sensing, and therapy are summarized. In addition, the advantages and disadvantages they present are discussed. Finally, a critical opinion of their potential application in real life biomedicine is given.