Protein-Modified CuS Nanotriangles: A Potential Multimodal Nanoplatform for In Vivo Tumor Photoacoustic/Magnetic Resonance Dual-Modal Imaging

Magneto-optical nanosystems for tumor multimodal imaging and therapy in-vivo

Multimodal imaging, which combines the strengths of two or more imaging modalities to provide complementary anatomical and molecular information, has emerged as a robust technology for enhancing diagnostic sensitivity and accuracy, as well as improving treatment monitoring. Moreover, the application of multimodal imaging in guiding precision tumor treatment can prevent under- or over-treatment, thereby maximizing the benefits for tumor patients. In recent years, several intriguing magneto-optical nanosystems with both magnetic and optical properties have been developed, leading to significant breakthroughs in the field of multimodal imaging and image-guided tumor therapy. These advancements pave the way for precise tumor medicine. This review summarizes various types of magneto-optical nanosystems developed recently and describes their applications as probes for multimodal imaging and agents for image-guided therapeutic interventions. Finally, future research and development prospects of magneto-optical nanosystems are discussed along with an outlook on their further applications in the biomedical field.

Evolving approaches in glioma treatment: harnessing the potential of copper metabolism modulation

The key properties and high versatility of metal nanoparticles have shed new perspectives on cancer therapy, with copper nanoparticles gaining great interest because of the ability to couple the intrinsic properties of metal nanoparticles with the biological activities of copper ions in cancer cells. Copper, indeed, is a cofactor involved in different metabolic pathways of many physiological and pathological processes. Literature data report on the use of copper in preclinical protocols for cancer treatment based on chemo-, photothermal-, or copper chelating-therapies. Copper nanoparticles exhibit anticancer activity via multiple routes, mainly involving the targeting of mitochondria, the modulation of oxidative stress, the induction of apoptosis and autophagy, and the modulation of immune response. Moreover, compared to other metal nanoparticles (e.g. gold, silver, palladium, and platinum), copper nanoparticles are rapidly cleared from organs with low systemic toxicity and benefit from the copper's low cost and wide availability. Within this review, we aim to explore the impact of copper in cancer research, focusing on glioma, the most common primary brain tumour. Glioma accounts for about 80% of all malignant brain tumours and shows a poor prognosis with the five-year survival rate being less than 5%. After introducing the glioma pathogenesis and the limitation of current therapeutic strategies, we will discuss the potential impact of copper therapy and present the key results of the most relevant literature to establish a reliable foundation for future development of copper-based approaches.

Biomimetic Theranostic Agents with Superior NIR-II Photoacoustic and Magnetic Resonance Imaging Performance for Targeted Photothermal Therapy of Prostate Cancer

The accurate diagnosis and treatment of prostate cancer at an early stage is crucial to reduce mortality rates. However, the limited availability of theranostic agents with active tumor-targeting abilities hinders imaging sensitivity and therapeutic efficiency. To address this challenge, we have developed biomimetic cell membrane-modified Fe₂O₃ nanoclusters implanted in polypyrrole (CM-LFPP), achieving photoacoustic/magnetic resonance dual-modal imaging-guided photothermal therapy of prostate cancer. The CM-LFPP exhibits strong absorption in the second near-infrared window (NIR-II, 1000-1700 nm), showing high photothermal conversion efficiency of up to 78.7% under 1064 nm laser irradiation, excellent photoacoustic imaging capabilities, and good magnetic resonance imaging ability with a T2 relaxivity of up to 48.7 s^-1 mM^-1. Furthermore, the lipid encapsulation and biomimetic cell membrane modification enable CM-LFPP to actively target tumors, leading to a high signal-to-background ratio of ~30.2 for NIR-II photoacoustic imaging. Moreover, the biocompatible CM-LFPP enables low-dose (0.6 W cm^-2) photothermal therapy of tumors under 1064 nm laser irradiation. This technology offers a promising theranostic agent with remarkable photothermal conversion efficiency in the NIR-II window, providing highly sensitive photoacoustic/magnetic resonance imaging-guided prostate cancer therapy.

NIR-II Imaging and Sandwiched Plasmonic Biosensor for Ultrasensitive Intraoperative Definition of Tumor-Invaded Lymph Nodes

Radical lymphadenectomy remains the cornerstone of preventing tumor metastasis through the lymphatic system. Current surgical resection of lymph nodes (LNs) based on fluorescence-guided surgery (FGS) suffers from low sensitivity/selectivity with only qualitative information, hampering accurate intraoperative decision-making. Herein, we develop a modularized theranostic system including NIR-II FGS and a sandwiched plasmonic chip (SPC). Intraoperative NIR-II FGS and detection of tumor-positive lymph nodes were performed on the gastric tumor to determine the feasibility of the modularized theranostic system in defining LN metastasis. Under the NIR-II imaging window, the orthotopic tumor and sentinel lymph nodes (SLNs) were successfully excised without ambient light interference in the operating room. Importantly, the SPC biosensor achieved 100% sensitivity and 100% specificity for tumor markers and realized rapid and high-throughput intraoperative SLN detection. We propose the synergetic design of combining the NIR-II FGS and suitable biosensor will substantially improve the efficiency of cancer diagnosis and therapy follow-up.

Core-satellite nanoreactors based on cationic photosensitizer modified hollow CuS nanocage for ROS diffusion enhanced phototherapy of hypoxic tumor

Photodynamic therapy (PDT) efficiency is directly affected by the reactive oxygen species (ROS) generated by photosensitizers. However, ROSs' ultrashort life span and limited diffusion distance restrict the PDT efficiency. Therefore, it is important to control the delivery strategy of photosensitizers for PDT treatment. Herein, the core-satellite nanoreactors were fabricated with oxygen generation and ROS diffusion properties. The hollow CuS encapsulating horseradish peroxidase (HRP) was combined with the cationic photosensitizers (PEI-Ce6). The unique photosensitizers delivery strategy makes the nanoreactors achieve ROS diffusion-enhanced PDT effect. First, HRP in "core" (HRP@CuS) can decompose hydrogen peroxide (H₂O₂) to O₂, increasing O₂ levels on the surface of the nanoreactor. Second, the Ce6 molecules covalent-linked with PEI are uniformly dispersed on the surface of CuS as a "satellite", avoiding Ce6 aggregation and causing more Ce6 molecules be activated to produce more ¹O₂. Due to the Ce6 was on the surface of the CuS nanocages, the generated ROS may ensure a larger diffusion range. Meanwhile, the inherently CuS nanocages exhibit photothermal and photoacoustic (PA) effect. The photothermal effect further enhances the ROS diffusion. Under the guidance of PA imaging, nanoreactors exhibit highly efficient hypoxic tumor ablation via photodynamic and photothermal effect. Overall, the core-satellite nanoreactors provide an effective strategy for tumor therapy, further promoting the research of photosensitizers delivery.

Albumin-Consolidated AIEgens for Boosting Glioma and Cerebrovascular NIR-II Fluorescence Imaging

The application of an exogenous polymer matrix to construct aggregation-induced emission (AIE) nanoprobes promotes the utility of AIE luminogens (AIEgens) in diagnosing brain diseases. However, the limited fluorescence (FL) and low active-targeting abilities of AIE-based nanoprobes impede their imaging application. Here, we employed endogenous albumin as an effective matrix to encapsulate AIEgens to enhance FL quantum yield (QY) and active-targeting ability. The albumin-consolidated strategy effectively inhibited the intramolecular vibration of AIEgens and enhanced endocytosis mediated by the gp60 receptor. The QYs of three kinds of albumin-based AIE nanoprobes with FL emissions ranging from the visible (400-650 nm) to the second near-infrared (NIR-II, 1000-1700 nm) region was at least 10% higher, and the tumor-targeting efficiency was ∼25% higher, compared with those of nanoprobes constructed by the exogenous polymer. Albumin-based AIE nanoprobes have achieved active-targeting NIR-II imaging of brain tumors and cerebrovascular imaging with a high signal-to-background ratio (SBR, ∼90) and high resolution (∼70 μm) in mouse models. Therefore, the albumin-based AIE nanoprobes will enable FL imaging-guided surgery of brain tumors and cerebral ischemia, which will improve surgical efficacy to prevent recurrence and side effects.

Advances in image-guided drug delivery for antibacterial therapy

The emergence of antibiotic-resistant bacterial strains is seriously endangering the global healthcare system. There is an urgent need for combining imaging with therapies to realize the real-time monitoring of pathological condition and treatment progress. It also provides guidance on exploring new medicines and enhance treatment strategies to overcome the antibiotic resistance of existing conventional antibiotics. In this review, we provide a thorough overview of the most advanced image-guided approaches for bacterial diagnosis (e.g., computed tomography imaging, magnetic resonance imaging, photoacoustic imaging, ultrasound imaging, fluorescence imaging, positron emission tomography, single photon emission computed tomography imaging, and multiple imaging), and therapies (e.g., photothermal therapy, photodynamic therapy, chemodynamic therapy, sonodynamic therapy, immunotherapy, and multiple therapies). This review focuses on how to design and fabricate photo-responsive materials for improved image-guided bacterial theranostics applications. We present a potential application of different image-guided modalities for both bacterial diagnosis and therapies with representative examples. Finally, we highlighted the current challenges and future perspectives image-guided approaches for future clinical translation of nano-theranostics in bacterial infections therapies. We envision that this review will provide for future development in image-guided systems for bacterial theranostics applications.

Design and application of organic contrast agents for molecular imaging in the second near infrared (NIR-II) window

Optical imaging in the second near-infrared (NIR-II) window has attracted interest in recent years because of the merits of reduced light scattering, minimal autofluorescence from biological tissues and deeper penetration depth in this wavelength range. In this review, we summarize NIR-II organic contrast agents reported in the past decade for photoacoustic and fluorescence imaging including members of the cyanine family, D-A-D structure dyes, phthalocyanines and semiconducting polymers. Improved imaging contrast and higher resolution could be favorably achieved by rational design of NIR-II fluorophores by tuning their properties including molar extinction coefficient, fluorescence quantum yield, emission wavelength and others. A wide variety of applications using NIR-II dyes has been realized including imaging of tumors, lymphatics, brains, intestines and others. Emerging applications such as targeted imaging and activable imaging with improved resolution and sensitivity have been demonstrated by innovative chemical modification of NIR-II dyes. Looking forward, rational design of improved NIR-II dyes for advanced bioimaging is likely to remain an area of interest for next-generation potential approaches to disease diagnosis.

Multifunctional nanotheranostics for near infrared optical imaging-guided treatment of brain tumors

Malignant brain tumors, a heterogeneous group of primary and metastatic neoplasms in the central nervous system (CNS), are notorious for their highly invasive and devastating characteristics, dismal prognosis and low survival rate. Recently, near-infrared (NIR) optical imaging modalities including fluorescence imaging (FLI) and photoacoustic imaging (PAI) have displayed bright prospect in innovation of brain tumor diagnoses, due to their merits, like noninvasiveness, high spatiotemporal resolution, good sensitivity and large penetration depth. Importantly, these imaging techniques have been widely used to vividly guide diverse brain tumor therapies in a real-time manner with high accuracy and efficiency. Herein, we provide a systematic summary of the state-of-the-art NIR contrast agents (CAs) for brain tumors single-modal imaging (e.g., FLI and PAI), dual-modal imaging (e.g., FLI/PAI, FLI/magnetic resonance imaging (MRI) and PAI/MRI) and triple-modal imaging (e.g., MRI/FLI/PAI and MRI/PAI/computed tomography (CT) imaging). In addition, we update the most recent progress on the NIR optical imaging-guided therapies, like single-modal (e.g., photothermal therapy (PTT), chemotherapy, surgery, photodynamic therapy (PDT), gene therapy and gas therapy), dual-modal (e.g., PTT/chemotherapy, PTT/surgery, PTT/PDT, PDT/chemotherapy, PTT/chemodynamic therapy (CDT) and PTT/gene therapy) and triple-modal (e.g., PTT/PDT/chemotherapy, PTT/PDT/surgery, PTT/PDT/gene therapy and PTT/gene/chemotherapy). Finally, we discuss the opportunities and challenges of the CAs and nanotheranostics for future clinic translation.

Biomimetic synthesis of 2D ultra-small copper sulfide nanoflakes based on reconfiguration of the keratin secondary structure for cancer theranostics in the NIR-II region

Two-dimensional transition metal dichalcogenides have attracted widespread attention in cancer theranostics due to their high specific surface area and excellent photothermal conversion properties. However, their dimensions and biodegradability have limited the exploration of the therapeutic properties of transition metal dichalcogenides. Herein, we explore the mechanism of the keratin α-helix-to-random coil transition, as an actuation mechanism for the controllable design and precise synthesis of two-dimension copper sulfide nanoflakes (CuS NFs) with high absorption in the NIR-II window. Upon mixing keratin and Cu²⁺, the hydrogen bonds that maintain the α-helix are broken by copper ions to form biuret coordination, while the structure of the α-helix is transformed into a random coil, providing a more scalable space for the growth of CuS NFs. The CuS NFs prepared in this way possess the great advantages of outstanding uniformity, size controllability, and biodegradability. Importantly, the CuS NFs in the NIR-II window show an excellent photothermal conversion efficiency (32.9%) and extraordinary photoacoustic signal. This work updates the fabrication of two-dimensional transition metal dichalcogenides and greatly enhances their competitiveness in the area of cancer theranostics in the NIR-II region, and provides significant theoretical and practical opportunities for the development of keratin using biomimetic synthesis.

Surfactant-Stripped Semiconducting Polymer Micelles for Tumor Theranostics and Deep Tissue Imaging in the NIR-II Window

Photoacoustic imaging (PA) in the second near infrared (NIR-II) window presents key advantages for deep tissue imaging owing to reduced light scattering and low background signal from biological structures. Here, a thiadiazoloquinoxaline-based semiconducting polymer (SP) with strong absorption in the NIR-II region is reported. After encapsulation of SP in Pluronic F127 (F127) followed by removal of excess surfactant, a dual functional polymer system named surfactant-stripped semiconductor polymeric micelles (SSS-micelles) are generated with water solubility, storage stability, and high photothermal conversion efficiency, permitting tumor theranostics in a mouse model. SSS-micelles have a wideband absorption in the NIR-II window, allowing for the PA imaging at both 1064 and 1300 nm wavelengths. The PA signal of the SSS-micelles can be detected through 6.5 cm of chicken breast tissue in vitro. In mice or rats, SSS-micelles can be visualized in bladder and intestine overlaid 5 cm (signal to noise ratio, SNR ≈ 17 dB) and 5.8 cm (SNR over 10 dB) chicken breast tissue, respectively. This work demonstrates the SSS-micelles as a nanoplatform for deep tissue theranostics.

Intraband Transition and Localized Surface Plasmon Resonance of Metal Chalcogenides Nanocrystals and their Dependence on Crystal Structure

Understanding the localized surface plasmon resonance (LSPR) and the intraband transition of semiconductor nanocrystals (NCs) has attracted considerable attention since it can provide the opportunity to investigate the boundary between...

Mitochondria-Targeted Nanomedicine for Enhanced Efficacy of Cancer Therapy

Nanomedicines have been designed and developed to deliver anticancer drugs or exert anticancer therapy more selectively to tumor sites. Recent investigations have gone beyond delivering drugs to tumor tissues or cells, but to intracellular compartments for amplifying therapy efficacy. Mitochondria are attractive targets for cancer treatment due to their important functions for cells and close relationships to tumor occurrence and metastasis. Accordingly, multifunctional nanoplatforms have been constructed for cancer therapy with the modification of a variety of mitochondriotropic ligands, to trigger the mitochondria-mediated apoptosis of tumor cells. On this basis, various cancer therapeutic modalities based on mitochondria-targeted nanomedicines are developed by strategies of damaging mitochondria DNA (mtDNA), increasing reactive oxygen species (ROS), disturbing respiratory chain and redox balance. Herein, in this review, we highlight mitochondria-targeted cancer therapies enabled by nanoplatforms including chemotherapy, photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), sonodynamic therapy (SDT), radiodynamic therapy (RDT) and combined immunotherapy, and discussed the ongoing challenges.

Cascade targeting tumor mitochondria with CuS nanoparticles for enhanced photothermal therapy in the second near-infrared window

Photothermal therapy, assisted by local heat generation using photothermal nanoparticles (NPs), is an emerging strategy to treat tumors noninvasively. To improve treatment outcomes and to alleviate potential side effects on normal tissue cells, utilizing the optically transparent second near-infrared (NIR-II) window and actively targeting tumors are critical. Considering that mitochondria are heat sensitive and play an important role in the up-regulation of metabolic activity in tumor cells, herein we report a cascade targeting scheme that enables active photothermal ablation of tumor mitochondria. First, NIR-II absorbing CuS NPs were surface modified with the mitochondria targeting moiety (3-carboxypropyl) triphenylphosphonium bromide (TPP) and then shielded with CD44 targeting hyaluronic acid, which will only expose TPP upon reaching the tumor sites. This allowed over 90% CuS NP enrichment at tumor mitochondria, and as a result, significantly improved tumor cell photothermal ablation was observed at the cellular level. An in vivo study demonstrated enhanced tumor uptake and improved tumor growth suppression by using these cascade targeting CuS NPs as NIR-II photothermal agents.

Infection microenvironment-activated nanoparticles for NIR-II photoacoustic imaging-guided photothermal/chemodynamic synergistic anti-infective therapy

Subcutaneous abscesses caused by drug-resistant bacteria pose huge challenges to human health. The design of infection microenvironment-activated biomaterials has an advantage for the diagnosis and treatment of infective diseases due to its high specificity and efficiency. Herein, a novel theranostic platform based on Cu₂O nanoparticles (NPs) is successfully constructed via a simple, fast and low-cost approach. The Cu₂O NPs exhibit high sensitivity to overexpressed H₂S and H₂O₂ in the bacterial infection microenvironment. After in situ injection, the Cu₂O NPs will rapidly react with the endogenous H₂S to generate Cu₉S₈ NPs, which exhibits high absorbance in the second near-infrared (NIR-II) biowindow. The Cu₉S₈ NPs serving as NIR-II photoacoustic contrast agents can exactly distinguish between inflammatory and normal tissues. With the guidance of NIR-II photoacoustic imaging (PAI), H₂S-activated photothermal antibacterial therapy (PTAT) can realize excellent antibacterial performance under 1060 nm laser irradiation. Meanwhile, the Cu₂O NPs can effectively catalyze H₂O₂ at the site of inflammation to produce hydroxyl radicals with strong antibacterial property via Fenton-like reaction, resulting in the damage of bacterial cell membrane. Furthermore, the application of Cu₂O NPs can enhance epidermic migration and facilitate the re-epithelialization of the infected skin. In vivo experiment shows that 97.9% methicillin-resistant Staphylococcus aureus are eliminated by the synergistic PTAT and chemodynamic antibacterial therapy.

Intravital NIR-II three-dimensional photoacoustic imaging of biomineralized copper sulfide nanoprobes

Photoacoustic (PA) imaging with functional nanoprobes in the second near-infrared region (NIR-II, 1000-1700 nm) has aroused much interest due to its deep tissue penetration and high maximum laser permissible exposure. However, most NIR-II PA imaging is performed using the two-dimensional (2D) imaging modality, which impedes the comprehension of the in vivo biodistribution, angiography and molecular-targeted performance of NIR-II nanoprobes (NPs). Herein, we report the systematic monitoring of biomineralized copper sulfide (CuS) NPs, typical NIR-II NPs, in mouse models by employing NIR-II three-dimensional (3D) PA imaging. The advanced imaging modality provides dynamic information about the 3D biodistribution and metabolic pathway of CuS NPs. We also achieved contrast-enhanced 3D PA imaging of abdominal and cerebral vessels at a high signal-to-background ratio. Moreover, the tumor-targeted CuS NPs conjugated with the bombesin peptide endowed NIR-II 3D PA with superior performance in imaging orthotopic tumors both deep in the prostate and in the brain beneath the intact scalp and skull. Our results highlight the potential of NIR-II 3D PA imaging for the evaluation of the in vivo behavior of NPs, thus providing a promising strategy for screening NPs in clinical translational studies.

In vivo intravascular photoacoustic imaging at a high speed of 100 frames per second

Intravascular photoacoustic (IVPA) imaging technology enables the visualization of pathological characteristics (such as inflammation activities, lipid deposition) of the artery wall. Blood flushing is a necessary step in improving the imaging quality in in vivo IVPA imaging. But the limited imaging speed of the systems stretches their flushing time, which is an important obstacle of their clinical translations. In this paper, we report an improvement in IVPA/IVUS imaging speed to 100 frames per second. The high-speed imaging is demonstrated in rabbit in vivo, visualizing the nanoparticles accumulated on abdominal aorta wall at the wavelength of 1064 nm, in real time display. Blood flushing in vivo improves the IVPA signal-noise-ratio by around 3.5 dB. This study offers a stable, efficient and easy-to-use tool for instantaneous disease visualization and disease diagnosis in research and forwards IVPA/IVUS imaging technology towards clinical translations.

NIR II-Excited and pH-Responsive Ultrasmall Nanoplatform for Deep Optical Tissue and Drug Delivery Penetration and Effective Cancer Chemophototherapy

The limited tumor tissue penetration of many nanoparticles remains a formidable challenge to their therapeutic efficacy. Although several photonanomedicines have been applied to improve tumor penetration, the first near-infrared window mediated by the low optical tissue penetration depth severely limits their anticancer effectiveness. To achieve deep optical tissue and drug delivery penetration, a near-infrared second window (NIR-II)-excited and pH-responsive ultrasmall drug delivery nanoplatform was fabricated based on BSA-stabilized CuS nanoparticles (BSA@CuS NPs). The BSA@CuS NPs effectively encapsulated doxorubicin (DOX) via strong electrostatic interactions to form multifunctional nanoparticles (BSA@CuS@DOX NPs). The BSA@CuS@DOX NPs had an ultrasmall size, which allowed them to achieve deeper tumor penetration. They also displayed stronger NIR II absorbance-mediated deep optical tissue penetration than that of the NIR I window. Moreover, the multifunctional nanoplatform preferentially accumulated in tumor sites, induced tumor hyperthermia, and generated remarkably high ROS levels in tumor sites upon NIR-II laser (1064 nm) irradiation. More importantly, our strategy achieved excellent synergistic effects of chemotherapy and phototherapy (chemophototherapy) under the guidance of photothermal imaging. The developed nanoparticles also showed good biocompatibility and bioclearance properties. Therefore, our work demonstrated a facile strategy for fabricating a multifunctional nanoplatform that is a promising candidate for deep tumor penetration as an effective antitumor therapy.

Co-encapsulating indocyanine green and CT contrast agent within nanoliposomes for trimodal imaging and near infrared phototherapy of cancer

X-ray CT imaging can be complementary to fluorescence and photoacoustic imaging (FLI and PAI), allowing for high spatial resolution and high-sensitivity multimodal imaging for imaging guided treatment. In this study, the CT contrast agent iohexol was co-encapsulated with indocyanine green (ICG) within nanoliposomes (NLs) to explore their interaction and possible application of this liposomal formulation (LGI) in cancer theranostics. The photophysical properties of LGI were studied to assess the effect of iohexol on ICG that can enhance the efficiency of ICG-based near infrared photodynamic therapy (PDT). The CT, FLI and PA imaging abilities of LGI were also investigated. Furthermore, the near infrared phototherapy of cancer cells in vitro was performed, exhibiting higher phototherapy efficacy of LGI in comparison with other ICG formulations. We conclude that LGI can serve as a highly efficient theranostic nanoplatform for multimodal (fluorescence, CT and PA) imaging and near infrared phototherapy.

Gold-based Inorganic Nanohybrids for Nanomedicine Applications

Noble metal Au nanoparticles have attracted extensive interests in the past decades, due to their size and morphology dependent localized surface plasmon resonances. Their unique optical property, high chemical stability, good biocompatibility, and easy functionalization make them promising candidates for a variety of biomedical applications, including bioimaging, biosensing, and cancer therapy. With the intention of enhancing their optical response in the near infrared window and endowing them with additional magnetic properties, Au nanoparticles have been integrated with other functional nanomaterials that possess complementary attributes, such as copper chalcogenides and magnetic metal oxides. The as constructed hybrid nanostructures are expected to exhibit unconventional properties compared to their separate building units, due to nanoscale interactions between materials with different physicochemical properties, thus broadening the application scope and enhancing the overall performance of the hybrid nanostructures. In this review, we summarize some recent progresses in the design and synthesis of noble metal Au-based hybrid inorganic nanostructures for nanomedicine applications, and the potential and challenges for their clinical translations.

Ultrasmall aqueous starch-capped CuS quantum dots with tunable localized surface plasmon resonance and composition for the selective and sensitive detection of mercury(ii) ions

Ultrasmall starch-capped CuS quantum dots (QDs) with controllable size were chemically fabricated in an aqueous medium. The phase of the CuS QDs was confirmed via X-ray diffraction (XRD), whereas the characteristic localized surface plasmon resonance (LSPR) peak in the near-infrared (NIR) region was measured using UV-Vis spectroscopy. Transmission electron microscopy and high bandgap analysis confirmed the formation of ultrasmall CuS QDs in the size range of 4-8 nm. CuS QDs have been used for the selective and sensitive detection of Hg2+ ions through colorimetric and spectroscopic techniques. The selective sensing of Hg2+ ions from various metal ions was detected via a remarkable change in color, damping in LSPR intensity, significant change in the Fourier-transform infrared spectra and X-ray photoelectron spectroscopic measurements. The mechanism of interaction between the CuS QDs and Hg2+ ions has been deeply explored in terms of the role played by the starch and the reorganization of sulfide and disulfide bonds to facilitate the access of Hg2+ ions into the CuS lattice. Finally, an intermediate Cu2-x Hg x S nanostructure resulted in the leaching of Cu+ ions into the solution, which were further recovered and reused for the formation of fluorescent Cu2S nanoparticles. Thus, the entire process of synthesis, sensing and reuse paves the way for sustainable nanotechnology.

Recent Advances of Bioresponsive Nano-Sized Contrast Agents for Ultra-High-Field Magnetic Resonance Imaging

The ultra-high-field magnetic resonance imaging (MRI) nowadays has been receiving enormous attention in both biomaterial research and clinical diagnosis. MRI contrast agents are generally comprising of T1-weighted and T2-weighted contrast agent types, where T1-weighted contrast agents show positive contrast enhancement with brighter images by decreasing the proton's longitudinal relaxation times and T2-weighted contrast agents show negative contrast enhancement with darker images by decreasing the proton's transverse relaxation times. To meet the incredible demand of MRI, ultra-high-field T2 MRI is gradually attracting the attention of research and medical needs owing to its high resolution and high accuracy for detection. It is anticipated that high field MRI contrast agents can achieve high performance in MRI imaging, where parameters of chemical composition, molecular structure and size of varied contrast agents show contrasted influence in each specific diagnostic test. This review firstly presents the recent advances of nanoparticle contrast agents for MRI. Moreover, multimodal molecular imaging with MRI for better monitoring is discussed during biological process. To fasten the process of developing better contrast agents, deep learning of artificial intelligent (AI) can be well-integrated into optimizing the crucial parameters of nanoparticle contrast agents and achieving high resolution MRI prior to the clinical applications. Finally, prospects and challenges are summarized.

Albumin-bioinspired iridium oxide nanoplatform with high photothermal conversion efficiency for synergistic chemo-photothermal of osteosarcoma

Protein-based nanocarriers with inherent biocompatibility have been widely served as building blocks to construct versatile therapeutic nanoplatforms. Herein, bovine serum albumin-iridium oxide nanoparticles (denoted BSA-IrO₂ NPs) are successfully synthesized via one-step biomineralization approach. The BSA-IrO₂ NPs exhibits uniform size (40 nm), superb biocompatibility and high drug loading capacity for doxorubicin (27.4 wt%). Under near-infrared (NIR) laser irradiation, the as-prepared BSA-IrO₂ NPs exhibited high photothermal conversion ability (54.3%) and good photostability. The in vitro drug release experiments displayed pH and NIR laser -triggered DOX release profiles, which could enhance the therapeutic anticancer effect. By utilizing this DOX loaded nanoplatform, effective synergistic chemo-photothermal therapy against human osteosarcoma can be realized, which has been systematically verified both in vitro and in vivo. Notably, in vivo pharmacokinetics studies showed that BSA-IrO₂@DOX had prolonged blood circulation time due to the BSA component can improve the stealthiness of the nanoparticles during the blood circulation. Meanwhile, in vitro and in vivo toxicity studies demonstrated that the BSA-IrO₂ NPs can act as biocompatible agents for drug delivery and cancer therapy. Therefore, this work presents a biomineralized iridium-based NPs with remarkable features and be used as a very potential therapeutic nanoplatform for cancer treatment.

Protein-based nanoplatforms for tumor imaging and therapy

Cancer is one of the leading causes of death all over the world. The development of nanoplatform provides a promising strategy for the diagnosis and treatment of cancer. As the foundation of the nanoplatform, the composition of nanocarrier decides the basic properties. Protein exists in all kinds of life and participates in any life activities, having great potentials to serve as a nanocarrier because of its excellent biocompatibility, abundance of functional groups, and inherent biological activity. As a result, protein-based nanoplatforms have evoked extensive interests for tumor imaging and therapy. This review presents the latest progresses on the advancement of protein-based nanoplatforms, introducing the most common protein nanocarriers (such as human/bovine serum albumin, ferritin, human transferrin) thoroughly including their physiochemical properties and specific applications. Also, other kinds of protein are briefly involved. Finally, the prospects and challenges of the development of protein-based nanoplatforms are summarized. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Fe-doped copper sulfide nanoparticles for in vivo magnetic resonance imaging and simultaneous photothermal therapy

Multifunctional theranostic agents are widely applied in cancer diagnosis and treatment. These agents can significantly improve therapeutic outcomes and reduce adverse effects in current cancer therapy. Here, we have designed and synthesized iron-doped copper sulfide nanoparticles with polyvinylpyrollidone (FCS@PVP NPs) for magnetic resonance imaging (MRI) guided photothermal therapy. The biocompatible FCS@PVP NPs with strong near-infrared absorption could be used as the photothermal agent and the magnetic characteristic of Fe³⁺ ions could be applied to T ₁-weighted magnetic resonance imaging (MRI). The T ₁-weighted MRI, high photothermal performance, and the biodistribution of FCS@PVP NPs were investigated in mice after intravenous administration. The data showed that there was a high accumulation of FCS@PVP NPs in the tumor sites because of the enhanced permeability and retention (EPR) effect. This result also indicated that the tumors in tumor-bearing mice were effectively suppressed after FCS@PVP NPs treatment under 808 nm laser irradiation. More importantly, FCS@PVP NPs show low cytotoxicity and few side effects because of the quick and safe elimination through the hepatobiliary/fecal route. This work provided a foundation for the clinical application of FCS@PVP NPs as a promising multifunctional theranostic agent for the MRI guided photothermal therapy of cancer.

Nanomaterials for photoacoustic imaging in the second near-infrared window

Photoacoustic imaging (PAI) is a rapidly developing imaging technique for both fundamental research and clinical applications. Recent studies revealed that PAI in the second near-infrared (NIR-II) region exhibits enhanced deep-tissue imaging capability, which benefits from reduced photon scattering, minimized background noise and increased applicable power in comparison to PAI in the first near-infrared (NIR-I) region. This review focuses on the latest achievements on PAI in the NIR-II region. The advantages of shifting PAI from NIR-I to NIR-II is first compared, followed by discussions on nanomaterials as contrast agents for NIR-II PAI. In the end, the challenges and perspectives of PAI in the NIR-II region are also elaborated.

State-of-the-Art Preclinical Photoacoustic Imaging in Oncology: Recent Advances in Cancer Theranostics

The optical imaging plays an increasing role in preclinical studies, particularly in cancer biology. The combined ultrasound and optical imaging, named photoacoustic imaging (PAI), is an emerging hybrid technique for real-time molecular imaging in preclinical research and recently expanding into clinical setting. PAI can be performed using endogenous contrast, particularly from oxygenated and deoxygenated hemoglobin and melanin, or exogenous contrast agents, sometimes targeted for specific biomarkers, providing comprehensive morphofunctional and molecular information on tumor microenvironment. Overall, PAI has revealed notable opportunities to improve knowledge on tumor pathophysiology and on the biological mechanisms underlying therapy. The aim of this review is to introduce the principles of PAI and to provide a brief overview of current PAI applications in preclinical research, highlighting also on recent advances in clinical translation for cancer diagnosis, staging, and therapy.

Dual-Modal In Vivo Fluorescence/Photoacoustic Microscopy Imaging of Inflammation Induced by GFP-Expressing Bacteria

In this study, dual-modal fluorescence and photoacoustic microscopy was performed for noninvasive and functional in vivo imaging of inflammation induced by green fluorescent protein (GFP) transfected bacteria in mice ear. Our imaging results demonstrated that the multimodal imaging technique is able to monitor the tissue immunovascular responses to infections with molecular specificity. Our study also indicated that the combination of photoacoustic and fluorescence microscopy imaging can simultaneously track the biochemical changes including the bacterial distribution and morphological change of blood vessels in the biological tissues with high resolution and enhanced sensitivity. Consequently, the developed method paves a new avenue for improving the understanding of the pathology mechanism of inflammation.

Ultrasmall hybrid protein–copper sulfide nanoparticles for targeted photoacoustic imaging of orthotopic hepatocellular carcinoma with a high signal-to-noise ratio

A schematic illustration of CuS@BSA-RGD nanoparticle synthesis and the application of photoacoustic imaging in an orthotopic HCC model.

Protein-modified conjugated polymer nanoparticles with strong near-infrared absorption: a novel nanoplatform to design multifunctional nanoprobes for dual-modal photoacoustic and fluorescence imaging

Engineering conjugated polymer nanoparticles (CPNs) with an easily-modified surface is essential to construct multifunctional nanoprobes as contrast agents for dual-modal photoacoustic (PA) and fluorescence imaging, which can take advantages of the complementary information from a single modality. In this study, an abundant protein with plenty of functional groups was introduced for the first time to produce easily-modified CPNs, leading to a robust nanoplatform to engineer PA-based multifunctional nanoprobes due to their strong optical absorption in the near-infrared region. Meanwhile, the bovine serum albumin (BSA)-modified CPNs were further engineered by introducing gold clusters in situ, which can serve as fluorescent nanoprobes for dual-modal molecular imaging. In particular, the developed nanoplatform exhibited superior stability and excellent biocompatibility, making it an ideal candidate for various cancer-theranostics applications. More importantly, our imaging results demonstrated that the BSA-modified CPNs were excellent candidates to design PA-based contrast agents for multimodal imaging using the function of the protein. In addition, other functional blocks can also be added to the nanoplatform based on its easily-modified surface, making it a general method for the construction of multifunctional nanoprobes for disease theranostics.

Fabrication of multifunctional triple-responsive platform based on CuS-capped periodic mesoporous organosilica nanoparticles for chemo-photothermal therapy

INTRODUCTION

For an ideal drug delivery system, the outstanding drug-loading capacity and specific control of the release of therapeutics at the desired lesions are crucial. In this work, we developed a triple-responsive nanoplatform based on copper sulfide (CuS)-capped yolk-shell-structured periodic mesoporous organosilica nanoparticles (YSPMOs) for synergetic chemo-photothermal therapy.

METHODS

Herein, the YSPMOs were employed as a drug carrier, which exhibited a high doxorubicin (DOX) loading capacity of 386 mg/g. In this controlled-release drug delivery system, CuS serves as a gatekeeper to modify YSPMOs with reduction-cleavable disulfide bond (YSPMOs@CuS). CuS could not only avoid premature leakage in the delivery process, but also endowed the excellent photothermal therapy (PTT) ability.

RESULTS

Upon entering into cancer cells, the CuS gatekeeper was opened with the breaking of disulfide bonds and the DOX release from YSPMOs(DOX)@CuS in response to the intracellular acidic environment and external laser irradiation. Such a precise control over drug release, combined with the photothermal effect of CuS nanoparticles, is possessed by synergistic chemo-photothermal therapy for cancer treatment. Both in vitro and in vivo experimental data indicated that the synergistic effect of YSPMOs(DOX)@CuS showed efficient antitumor effect. In addition, low systemic toxicity was observed in the pathologic examinations of liver, spleen, lungs, and kidneys.

CONCLUSION

This versatile nanoplatform combination of PTT, chemotherapeutics, and gating components shows general potential for designing multifunctional drug delivery systems.

Protein-modified ultra-small gold clusters for dual-modal in vivo fluorescence/photoacoustic imaging

Background

Construction of nanoprobes for dual-modal fluorescence/photoacoustic imaging (PAI) is of great importance for the detection of disease pathology and the development of innovative therapeutics. Previously ultra-small gold clusters were designed and used as contrast agents for fluorescence imaging (FLI). However, it is not clear whether they can also serve as promising probes for PAI. In this study, protein-modified ultra-small gold clusters are produced and examined quantitatively as enhanced contrast agents for dual-modal in vivo fluorescence and PAI.

Methods

To construct the dual-modal ultra-small gold clusters, HAuCl₄·4H₂O aqueous solution was first mixed with the protein solution. NaOH was further introduced to the solution under vigorous stirring. The as-designed dual-modal nanoprobe was formed after stirring for 2 h at 65 °C. And then the solution was purified by gel column for further application. Zebrafish, cultivated in the solution containing gold clusters, was used in this study to demonstrate the dual-modal imaging ability of the nanoprobe by using our home-made optical-resolution photoacoustic microscopy and commercial fluorescence microscopy systems.

Results

The gold nanoclusters were synthesized with diameters of about 3 nm, which showed the broad absorption with a characteristic peak centered at 520 nm. A strong near-infrared emission ranging from 600 to 750 nm was also observed for the gold clusters. In addition, the cell viability was more than 90% even at a high concentration of the nanoprobes. The zebrafish cultivated with the gold clusters exhibited dramatically enhanced fluorescence and photoacoustic signal intensities.

Conclusions

Quantitative analysis results demonstrated that BSA-modified gold clusters were excellent contrast agents for in vivo dual-modal fluorescence/PAI. Due to their ultra-small size and superior biocompatibility, they can be applied to the detection and treatment of various diseases with enhanced sensitivity.

Highly Sensitive MoS2-Indocyanine Green Hybrid for Photoacoustic Imaging of Orthotopic Brain Glioma at Deep Site

Photoacoustic technology in combination with molecular imaging is a highly effective method for accurately diagnosing brain glioma. For glioma detection at a deeper site, contrast agents with higher photoacoustic imaging sensitivity are needed. Herein, we report a MoS₂-ICG hybrid with indocyanine green (ICG) conjugated to the surface of MoS₂ nanosheets. The hybrid significantly enhanced photoacoustic imaging sensitivity compared to MoS₂ nanosheets. This conjugation results in remarkably high optical absorbance across a broad near-infrared spectrum, redshifting of the ICG absorption peak and photothermal/photoacoustic conversion efficiency enhancement of ICG. A tumor mass of 3.5 mm beneath the mouse scalp was clearly visualized by using MoS₂-ICG as a contrast agent for the in vivo photoacoustic imaging of orthotopic glioma, which is nearly twofold deeper than the tumors imaged in our previous report using MoS₂ nanosheet. Thus, combined with its good stability and high biocompatibility, the MoS₂-ICG hybrid developed in this study has a great potential for high-efficiency tumor molecular imaging in translational medicine.

Dual Roles of Protein as a Template and a Sulfur Provider: A General Approach to Metal Sulfides for Efficient Photothermal Therapy of Cancer

Fabrication of clinically translatable nanoparticles (NPs) as photothermal therapy (PTT) agents against cancer is becoming increasingly desirable, but still challenging, especially in facile and controllable synthesis of biocompatible NPs with high photothermal efficiency. A new strategy which uses protein as both a template and a sulfur provider is proposed for facile, cost-effective, and large-scale construction of biocompatible metal sulfide NPs with controlled structure and high photothermal efficiency. Upon mixing proteins and metal ions under alkaline conditions, the metal ions can be rapidly coordinated via a biuret-reaction like process. In the presence of alkali, the inert disulfide bonds of S-rich proteins can be activated to react with metal ions and generate metal sulfide NPs under gentle conditions. As a template, the protein can confine and regulate the nucleation and growth of the metal sulfide NPs within the protein formed cavities. Thus, the obtained metal sulfides such as Ag₂ S, Bi₂ S₃ , CdS, and CuS NPs are all with small size and coated with proteins, affording them biocompatible surfaces. As a model material, CuS NPs are evaluated as a PTT agent for cancer treatment. They exhibit high photothermal efficiency, high stability, water solubility, and good biocompatibility, making them an excellent PTT agent against tumors. This work paves a new avenue toward the synthesis of structure-controlled and biocompatible metal sulfide NPs, which can find wide applications in biomedical fields.

Oxidation-Responsive, EuII/III-Based, Multimodal Contrast Agent for Magnetic Resonance and Photoacoustic Imaging

We report, for the first time, a multimodal, oxidation-responsive contrast agent for magnetic resonance imaging and photoacoustic imaging that uses the differences in the properties between Eu in the +2 and +3 oxidation states. The enhancement of contrast in T1-weighted magnetic resonance and photoacoustic imaging was observed in the +2 but not in the +3 oxidation state, and the complex is a known chemical exchange saturation transfer agent for magnetic resonance imaging in the +3 oxidation state.

Photoacoustic-Based Multimodal Nanoprobes: from Constructing to Biological Applications

Multimodal nanoprobes have attracted intensive attentions since they can integrate various imaging modalities to obtain complementary merits of single modality. Meanwhile, recent interest in laser-induced photoacoustic imaging is rapidly growing due to its unique advantages in visualizing tissue structure and function with high spatial resolution and satisfactory imaging depth. In this review, we summarize multimodal nanoprobes involving photoacoustic imaging. In particular, we focus on the method to construct multimodal nanoprobes. We have divided the synthetic methods into two types. First, we call it “one for all” concept, which involves intrinsic properties of the element in a single particle. Second, “all in one” concept, which means integrating different functional blocks in one particle. Then, we simply introduce the applications of the multifunctional nanoprobes for in vivo imaging and imaging-guided tumor therapy. At last, we discuss the advantages and disadvantages of the present methods to construct the multimodal nanoprobes and share our viewpoints in this area.