Cu2-x Se nanocrystals with localized surface plasmon resonance as sensitive contrast agents for in vivo photoacoustic imaging: demonstration of sentinel lymph node mapping

A clinical feasibility study of a photoacoustic finder for sentinel lymph node biopsy in breast cancer patients: A prospective cross-sectional study

The sentinel lymph node (SLNb) is generally performed using radioisotopes, blue dyes, or both to improve false negative rate. However, ionizing radiation is involved in a gamma probe with radioisotopes and the blue dye detection relies on native visual inspection by an operator. To overcome these limitations, we developed the photoacoustic finder (PAF), a highly sensitive, non-radioactive detector that uses only blue dye and a photoacoustic signal to detect SLNs. A total of 121 patients with breast cancer were enrolled, and 375 lymph nodes were excised using conventional SLNb. The PAF was used to measure the signal from the excised lymph nodes. We compared the SLN detection rates of each method (gamma probe, visual inspection, and PAF) and conducted a non-inferiority test. The PAF detected 87 % of SLNs, comparable to the gamma probe (85 %) and superior to visual inspection (73 %). Non-inferiority tests confirmed PAF's performance was not inferior to visual inspection (p < 0.001) or the gamma probe (p < 0.015). Using the dual-modal method (gamma probe + visual inspection) as the gold standard, PAF showed a sensitivity of 0.81 and specificity of 0.63. This study demonstrates that PAF, using only blue dye, offers a non-inferior alternative to the standard dual-modal SLN detection method with radioactive materials, opening new avenues for radiation-free SLNb in the future.

Synergistic photothermal and chemo-therapeutic platform utilizing Cu2-xSe/PDA/AIPH nanoparticles for targeted tumor eradication

In this study, we developed an innovative Cu2-xSe/PDA/AIPH nanoparticle platform that combines photothermal therapy and chemotherapy for effective tumor treatment. The Cu2-xSe nanoparticles, known for their strong near-infrared (NIR) absorption, were encapsulated within a polydopamine (PDA) and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) matrix. Upon NIR irradiation, the platform triggers localized heating and subsequent thermal decomposition of AIPH, releasing ROS to induce significant oxidative damage in tumor cells. In vitro and in vivo experiments demonstrated that Cu2-xSe/PDA/AIPH nanoparticles exhibit excellent biocompatibility, effective photothermal conversion, and potent anticancer efficacy. This multifunctional nanosystem offers a promising approach for enhancing tumor therapy by combining PTT with ROS-mediated chemotherapy.

Synthesis and Superficial Modification "In Situ" of Copper Selenide (Cu2-x Se) Nanoparticles and Their Antibacterial Activity

Copper selenide nanoparticles (Cu2-x Se NPs) have received a lot of attention in recent decades due to their interesting properties and potential applications in various areas such as electronics, health, solar cells, etc. In this study, details of the synthesis and characterization of copper selenide nanoparticles modified with gum arabic (GA) are reported. Also, through transmission electronic microscopy (TEM) analysis, the transformation of the morphology and particle size of copper selenide nanoparticles in aqueous solution was studied. In addition, we present an antimicrobial study with different microorganisms such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Candida albiacans (C. albicans). Copper selenide nanoparticles were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry analysis (DSC) and TEM. XRD confirmed the crystal-line structure of the nanoparticles such as cubic berzelanite with a particle size of 6 nm ± 0.5. FTIR and TGA corroborated the surface modification of copper selenide nanoparticles with gum arabic, and DSC suggested a change in the structural phase from cubic to hexagonal. TEM analysis demonstrated that the surface modification of the Cu2-x Se NPs stabilized the nanostructure of the particles, preventing changes in the morphology and particle size. The antimicrobial susceptibility analysis of copper selenide nanoparticles indicated that they have the ability to inhibit the microbial growth of Staphylococcus aureus, Escherichia coli and Candida albicans.

Recent Progress of Copper-Based Nanomaterials in Tumor-Targeted Photothermal Therapy/Photodynamic Therapy

Nanotechnology, an emerging and promising therapeutic tool, may improve the effectiveness of phototherapy (PT) in antitumor therapy because of the development of nanomaterials (NMs) with light-absorbing properties. The tumor-targeted PTs, such as photothermal therapy (PTT) and photodynamic therapy (PDT), transform light energy into heat and produce reactive oxygen species (ROS) that accumulate at the tumor site. The increase in ROS levels induces oxidative stress (OS) during carcinogenesis and disease development. Because of the localized surface plasmon resonance (LSPR) feature of copper (Cu), a vital trace element in the human body, Cu-based NMs can exhibit good near-infrared (NIR) absorption and excellent photothermal properties. In the tumor microenvironment (TME), Cu2+ combines with H2O2 to produce O2 that is reduced to Cu1+ by glutathione (GSH), causing a Fenton-like reaction that reduces tumor hypoxia and simultaneously generates ROS to eliminate tumor cells in conjunction with PTT/PDT. Compared with other therapeutic modalities, PTT/PDT can precisely target tumor location to kill tumor cells. Moreover, multiple treatment modalities can be combined with PTT/PDT to treat a tumor using Cu-based NMs. Herein, we reviewed and briefly summarized the mechanisms of actions of tumor-targeted PTT/PDT and the role of Cu, generated from Cu-based NMs, in PTs. Furthermore, we described the Cu-based NMs used in PTT/PDT applications.

Ultrathin Porous Nitrogen-Doped Carbon-Coated CuSe Heterostructures for Combination Cancer Therapy of Photothermal Therapy, Photocatalytic Therapy, and Logic-Gated Chemotherapy

The construction of nanoplatforms for the multimodal cancer therapy still remains an enormous challenge. Ultrathin porous nitrogen-doped carbon coated stoichiometric copper selenide heterostructures (CuSe/NC) are prepared using a facile and green one-pot hydrothermal method. Interestingly, CuSe/NC itself can achieve both photothermal therapy (PTT) and photocatalytic therapy (PCT) under irradiation of a single near-infrared (NIR) light (808 nm), which is convenient and safe for clinical applications. Importantly, the triple-enhanced NIR light-activated PCT, including O₂-independent free radicals, Fenton-like reaction, and glutathione (GSH) depletion, breaks through the limitations of hypoxia and overexpressed GSH in cancer cells. Furthermore, CuSe/NC is loaded with doxorubicin (DOX) via metal coordination and then decorates with DNA to construct the CuSe/NC-DOX-DNA nanoplatform. Surprisingly, the facile nanoplatform has an advanced biocomputing capability of an "AND" Boolean logic gate with the smart "AND" logic controlled release of DOX upon combined stimuli of pH and GSH for precise cancer chemotherapy. The synergistic mechanism of proton-mediated ligand exchange between DOX and GSH is proposed for the "AND" logic controlled drug release from CuSe/NC-DOX-DNA. In vitro and in vivo studies demonstrate that CuSe/NC-DOX-DNA has excellent anticancer efficacy and negligible toxicity. This innovative nanoplatform with multienhanced anticancer efficacy provides a paradigm for combination cancer therapy of PTT, PCT, and chemotherapy.

Sorafenib-Loaded Cu2-xSe Nanoparticles Boost Photothermal-Synergistic Targeted Therapy against Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) accounts for the predominant form of liver malignancy and presents a leading cause of cancer-related death globally. Sorafenib (SOR), a first-line targeted drug for advanced HCC treatment, has a battery of untoward side effects. Photothermal therapy (PTT) has been utilized as an effective adjuvant in synergy with other approaches. However, little is known about the tumoricidal efficacy of combining SOR with PTT for HCC. Herein, a novel versatile nanoparticle, Cu_2-xSe@SOR@PEG (CSP), that is based on a photothermal Cu_2-xSe core and SOR for simultaneously reinforcing PTT and reducing the adverse effects of SOR was constructed. The synthesized CSP exhibited a remarkably enhanced therapeutic effect upon 808 nm laser irradiation via dampening HCC cell propagation and metastasis and propelling cell apoptosis. The intravenous administration of CSP substantially suppressed tumor growth in a xenograft tumor mouse model. It was noted that the CSP manifested low toxicity and excellent biocompatibility. Together, this work indicates a promising and versatile tool that is based on synergistic PTT and molecular-targeted therapy for HCC management.

Manganese Phosphate-Doxorubicin-Based Nanomedicines Using Mimetic Mineralization for Cancer Chemotherapy

Inorganic nanomaterials showed great potential as drug carriers for chemotherapeutics molecules due to their biocompatible physical and chemical properties. A manganese-based inorganic nanomaterial manganese phosphate (MnP) had become a new drug carrier in cancer therapy. However, the approach for manganese phosphate preparation and drug integration is still confined in complex methods. Inspired by mimetic mineralization, we proposed a "one-step" method for the preparation of manganese phosphate-doxorubicin (DOX) nanomedicines (MnP-DOX) by manganese ion and DOX complexation. The structural characterization results revealed that the prepared MnP-DOX nanocomplexes were homogeneous with controlled sizes and shapes. More importantly, the MnP-DOX nanocomposites could significantly induce cancer inhibition in vitro and in vivo. The results indicated that the drug molecules were integrated into MnP nanocarriers by mimetic mineralization, which not only prevented the premature release of the drug but also reduced excessive modification. Moreover, the designed MnP-DOX complex showed high loading efficacy and pH-dependent degradation leading to drug release, achieving high efficiency for cancer chemotherapy in vitro and in vivo via a facile process. These achievements presented an approach to construct the manganese phosphate-based chemotherapy nanomedicines by mimetic mineralization for cancer therapy.

Efficient pollutant degradation under ultraviolet to near-infrared light irradiation and dark condition using CuSe nanosheets: Mechanistic insight into degradation

The hydrothermally prepared two-dimensional copper selenide nanosheets (2D CuSe NSs) have been employed for the first time to degrade rhodamine B (RhB) in the presence of hydrogen peroxide (H₂O₂) under ultraviolet to near-infrared (NIR) light irradiation and dark condition. The experimental measurements demonstrate that 99.7% RhB is degraded under NIR light irradiation for 120 min. Moreover, the experimental tests clearly demonstrate that the 2D CuSe NSs display excellent ability to degrade RhB under dark condition. The different degradation mechanisms under the light irradiation and dark condition have been revealed by the experimental tests through the investigation of H₂O₂ role and the evaluation of hydroxyl radicals (•OH) and H₂O₂ concentration during the degradation reaction. Under light irradiation, the H₂O₂ traps the photogenerated electrons of the CuSe to generate •OH and hydroxide ion (OH^-), and the holes react with OH^- to produce •OH, making RhB to be degraded efficiently. Under dark conduction, the 2D CuSe NSs react with H₂O₂ to exhibit Fenton-like process to degrade RhB with a degradation rate of 90.0% within 120 min. This work opens a pathway for developing nanostructures with full-solar-responsive and strong near-infrared photocatalytic activity as well as Fenton-like reaction to efficiently degrade pollutants under light irradiation and dark condition.

Optothermal properties of plasmonic inorganic nanoparticles for photoacoustic applications

Plasmonic systems are becoming a favourable alternative to dye molecules in the generation of photoacoustic signals for spectroscopy and imaging. In particular, inorganic nanoparticles are appealing because of their versatility. In fact, as the shape, size and chemical composition of nanoparticles are directly correlated with their plasmonic properties, the excitation wavelength can be tuned to their plasmon resonance by adjusting such traits. This feature enables an extensive spectral range to be covered. In addition, surface chemical modifications can be performed to provide the nanoparticles with designed functionalities, e.g., selective affinity for specific macromolecules. The efficiency of the conversion of absorbed photon energy into heat, which is the physical basis of the photoacoustic signal, can be accurately determined by photoacoustic methods. This review contrasts studies that evaluate photoconversion in various kinds of nanomaterials by different methods, with the objective of facilitating the researchers' choice of suitable plasmonic nanoparticles for photoacoustic applications.

Synthesis, modification and bioapplications of nanoscale copper chalcogenides

Copper chalcogenides have a simple general formula, variable atomic ratios, and complicated crystal structures, which lead to their wealth of optical, electrical, and magnetic properties with great potential for wide applications ranging from energy conversion to the biomedical field. Herein, we summarize the recent advances in (1) the synthesis of size- and morphology tunable nanostructures by different methods; (2) surface modification and functionalization for different purposes; and (3) bioapplications for diagnosis and treatment of tumors by different imaging and therapy methods, as well as antibacterial applications. We also briefly discuss the future directions and challenges of copper chalcogenide nanoparticles in the biomedical field.

Understanding Nanoparticle Toxicity to Direct a Safe-by-Design Approach in Cancer Nanomedicine

Nanomedicine is a rapidly growing field that uses nanomaterials for the diagnosis, treatment and prevention of various diseases, including cancer. Various biocompatible nanoplatforms with diversified capabilities for tumor targeting, imaging, and therapy have materialized to yield individualized therapy. However, due to their unique properties brought about by their small size, safety concerns have emerged as their physicochemical properties can lead to altered pharmacokinetics, with the potential to cross biological barriers. In addition, the intrinsic toxicity of some of the inorganic materials (i.e., heavy metals) and their ability to accumulate and persist in the human body has been a challenge to their translation. Successful clinical translation of these nanoparticles is heavily dependent on their stability, circulation time, access and bioavailability to disease sites, and their safety profile. This review covers preclinical and clinical inorganic-nanoparticle based nanomaterial utilized for cancer imaging and therapeutics. A special emphasis is put on the rational design to develop non-toxic/safe inorganic nanoparticle constructs to increase their viability as translatable nanomedicine for cancer therapies.

Perspectives and advancements in the design of nanomaterials for targeted cancer theranostics

Cancer continues to be one of the most challenging diseases to be treated and is one of the leading causes of deaths around the globe. Cancers account for 13% of all deaths each year, with cancer-related mortality expected to rise to 13.1 million by the year 2030. Although, we now have a large library of chemotherapeutic agents, the problem of non-selectivity remains the biggest drawback, as these substances are toxic not only to cancerous cells, but also to other healthy cells in the body. The limitations with chemotherapy and radiation have led to the discovery and development of novel strategies for safe and effective treatment strategies to manage the menace of cancer. Researchers have long justified and have shed light on the emergence of nanotechnology as a potential area for cancer therapy and diagnostics, whereby, nanomaterials are used primarily as nanocarriers or as delivery agents for anticancer drugs due to their tumor targeting properties. Furthermore, nanocarriers loaded with chemotherapeutic agents also overcome biological barriers such as renal and hepatic clearances, thus improving therapeutic efficacy with lowered morbidity. Theranostics, which is the combination of rationally designed nanomaterials with cancer-targeting moieties, along with protective polymers and imaging agents has become one of the core keywords in cancer research. In this review, we have highlighted the potential of various nanomaterials for their application in cancer therapy and imaging, including their current state and clinical prospects. Theranostics has successfully paved a path to a new era of drug design and development, in which nanomaterials and imaging contribute to a large variety of cancer therapies and provide a promising future in the effective management of various cancers. However, in order to meet the therapeutic needs, theranostic nanomaterials must be designed in such a way, that take into account the pharmacokinetic and pharmacodynamics properties of the drug for the development of effective carcinogenic therapy.

In Vivo Dual-Modal Photoacoustic and Ultrasound Imaging of Sentinel Lymph Nodes Using a Solid-State Dye Laser System

Photoacoustic imaging (PAI) is being actively investigated as a non-invasive and non-radioactive imaging technique for sentinel lymph node (SLN) biopsy. By taking advantage of optical and ultrasound imaging, PAI probes SLNs non-invasively with methylene blue (MB) in both live animals and breast cancer patients. However, these PAI systems have limitations for widespread use in clinics and commercial marketplaces because the lasers used by the PAI systems, e.g., tunable liquid dye laser systems and optical parametric oscillator (OPO) lasers, are bulky in size, not economical, and use risky flammable and toxic liquid dyes. To overcome these limitations, we are proposing a novel dual-modal photoacoustic and ultrasound imaging system based on a solid-state dye laser (SD-PAUSI), which is compact, convenient, and carries far less risk of flammability and toxicity. Using a solid-state dye handpiece that generates 650-nm wavelength, we successfully imaged the MB tube positioned deeply (~3.9 cm) in chicken breast tissue. The SLNs were also photoacoustically detected in the in vivo rats beneath a 2.2-cm-thick layer of chicken breast, which is deeper than the typical depth of SLNs in humans (1.2 ± 0.5 cm). Furthermore, we showed the multispectral capability of the PAI by switching the dye handpiece, in which the MB-dyed SLN was selectively highlighted from the surrounding vasculature. These results demonstrated the great potential of the SD-PAUSI as an easy but effective modality for SLN detection.

Synthesis of SiO2@Cu2-xSe nanospheres for efficient near-infrared radiation mediated treatment and care of gastric cancer patients

Rational design and fabrication of suitable optical absorbing agents (OAAs) are of great significance for state-of-the-art photothermal cancer therapy. Copper selenides have recently emerged as a type of promising photothermal operators thanks to their engineered effortlessness, high carrier concentration, and superior photothermal transformation. Nevertheless, the further in vivo applications are hampered owing to their poor biocompatibility and hydrophobicity. Herein, we synthesized the judicious structure of Cu2-xSe nanospheres coated with mesoporous silica for improving their biocompatibility and hydrophilicity. The Cu2-xSe@mSiO2 core-shell nanospheres were studied by scanning/transmission electron microscopy (SEM/TEM), X-ray (XRD and XPS), and UV-Visible techniques. Such nanocomposite achieved great ability in photothermal removal of cancer cells with little toxicity. The cell death mechanism has been investigated through typical biochemical assays including acridine orange and ethidium bromide (AO-EB), flowcytometry, and nuclear staining. In addition, the cell cycle arrest in human gastric cancer cells (GCCs) has also been evaluated. Strikingly, the in vivo chemo-photothermal therapy of as-prepared Cu2-xSe@mSiO2 toward GCCs confirms the excellent antitumor activity of the core-shell nanospheres under near-infrared radiation (NIR) radiation. It is firmly believed that the Cu2-xSe@mSiO2 nanocomposites hold great potential to function as OAAs for NIR mediated treatment and care of gastric cancer patients.

Photoacoustic Imaging for Management of Breast Cancer: A Literature Review and Future Perspectives

In this review article, a detailed chronological account of the research related to photoacoustic imaging for the management of breast cancer is presented. Performing a detailed analysis of the breast cancer detection related photoacoustic imaging studies undertaken by different research groups, this review attempts to present the clinical evidence in support of using photoacoustic imaging for breast cancer detection. Based on the experimental evidence obtained from the clinical studies conducted so far, the performance of photoacoustic imaging is compared with that of conventional breast imaging modalities. While we find that there is enough experimental evidence to support the use of photoacoustic imaging for breast cancer detection, additional clinical studies are required to be performed to evaluate the diagnostic potential of photoacoustic imaging for identifying different types of breast cancer. To establish the utility of photoacoustic imaging for breast cancer screening, clinical studies with high-risk asymptomatic patients need to be done.

The release and detection of copper ions from ultrasmall theranostic Cu2-xSe nanoparticles

Nanoscale copper chalcogenides have been widely used in nanomedicine, however, their pharmacokinetics, degradation, and biological effects of released copper ions are usually overlooked, which are crucial for their future clinical translation. Herein, we report the in vitro and in vivo release of copper ions from polyvinylpyrrolidone (PVP) functionalized ultrasmall copper selenide (Cu2-xSe) theranostic nanoparticles. We synthesized a Cu2+-specific fluorescent probe (NCM), which can quickly and specifically react with copper ions to exhibit very strong near infrared fluorescence. The in vitro study shows that copper ions can be slowly released from Cu2-xSe nanoparticles in aqueous solution with the progress of their oxidation. The release of copper ions from Cu2-xSe nanoparticles in RAW 264.7 murine macrophages is very fast, evidenced by the gradual increase of fluorescence intensity and the diffusion of fluorescence from cytoplasm into nuclei. We also demonstrate the distribution, degradation, and the metabolism of ultrasmall Cu2-xSe nanoparticles by the in vivo fluorescence imaging, the blood routine test, blood biochemistry and histology analysis, and the characterization of copper transport and binding proteins. The results show that ultrasmall Cu2-xSe nanoparticles were mainly eliminated through feces and urine from the body within 72 h after intravenous injection, and the released copper ions did not cause severe toxicity. Our research highlights the great potential of copper chalcogenide nanoparticles in nanomedicine.

Current concepts in nanostructured contrast media development for in vivo photoacoustic imaging

To overcome the endogenous photoacoustic contrast arising from endogenous species, specific contrast agents need to be developed, allowing PAI to successfully identify targeted contrast in the range of wavelength in which the interference from the biomatrix is minimized.

Noninvasive photothermal cancer therapy nanoplatforms via integrating nanomaterials and functional polymers

In the cutting-edge field of cancer therapy, noninvasive photothermal therapy (PTT) has received great attention because it is considered to overcome the drawbacks of conventional surgery, radiotherapy and chemotherapy of severe body injuries and side effects on the immune system. The construction of PTT therapeutic and theranostic nanoplatforms is the key issue in achieving tumor targeting, imaging and therapy in a synergetic manner. In this review, we focus on the recent advances in constructing PTT therapeutic and theranostic nanoplatforms by integrating nanomaterials and functional polymers. The noninvasive photothermal cancer therapy mechanism and achievement strategies of PTT therapeutic and theranostic nanoplatforms are presented as well as the innovative construction strategies and perspectives for the future. Owing to their high tumor ablation efficiency, biological availability and low- or non-toxicity, PTT therapeutic and theranostic nanoplatforms are promising and emerging in medicine and clinical applications.

Focused Ultrasound-Augmented Delivery of Biodegradable Multifunctional Nanoplatforms for Imaging-Guided Brain Tumor Treatment

The blood brain barrier is the main obstacle to delivering diagnostic and therapeutic agents to the diseased sites of brain. It is still of great challenge for the combined use of focused ultrasound (FUS) and theranostic nanotechnology to achieve noninvasive and localized delivery of chemotherapeutic drugs into orthotopic brain tumor. In this work, a unique theranostic nanoplatform for highly efficient photoacoustic imaging-guided chemotherapy of brain tumor both in vitro and in vivo, which is based on the utilization of hollow mesoporous organosilica nanoparticles (HMONs) to integrate ultrasmall Cu_2-x Se particles on the surface and doxorubicin inside the hollow interior, is synthesized. The developed multifunctional theranostic nanosystems exhibit tumor-triggered programmed destruction due to the reducing microenvironment-responsive cleavage of disulfide bonds that are incorporated into the framework of HMONs and linked between HMONs and Cu_2-x Se, resulting in tumor-specific biodegradation and on-demand drug-releasing behavior. Such tumor microenvironment-responsive biodegradable and biocompatible theranostic nanosystems in combination with FUS provide a promising delivery nanoplatform with high performance for orthotopic brain tumor imaging and therapy.

Vacancy engineering of Cu2-xSe nanoparticles with tunable LSPR and magnetism for dual-modal imaging guided photothermal therapy of cancer

The vacancies in the semiconductor nanocrystals not only induce unique properties, but also provide spaces for engineering them with multifunctions by the introduction of other elements. Herein, the vacancy of Cu_2-xSe nanoparticles was tuned by doping with magnetic ferric ions (Fe³⁺) at room temperature, and the position and intensity of the near-infrared localized surface plasmon resonance (LSPR) in the resultant nanostructure can be finely controlled by altering the feeding amount of Fe³⁺ ions. The results of the density-functional theory (DFT) calculations show that both doping and replacement reactions are favourable. Owing to its tunable near-infrared absorption and magnetic property, the obtained hybrid nanostructure was demonstrated to be a novel nanotheranostic agent for effective deep-tissue photoacoustic imaging, magnetic resonance imaging, and photothermal therapy of cancer.

Biodegradable MoOx nanoparticles with efficient near-infrared photothermal and photodynamic synergetic cancer therapy at the second biological window

Near-infrared (NIR) laser induced phototherapy has been considered as a noninvasive option for cancer therapy. Herein, we report plasmonic PEGylated molybdenum oxide nanoparticles (PEG-MoO_x NPs) that were synthesized by using a facile hydrothermal method. The PEG-MoO_x NPs exhibit broad absorption at the NIR biological window and remarkable photothermal conversion ability in the first (808 nm) and the second (1064 nm) windows. Moreover, the biocompatible PEG-MoO_x NPs exhibit effective cellular uptake and could be eliminated gradually from the liver and spleen in mice. Studies on the therapeutic effects of these NPs under 808 and 1064 nm exposures with mild hyperthermia are conducted. According to the result, exposure to 1064 nm irradiation can not only effectively convert light into heat but also sensitize the formation of reactive oxygen species (ROS), which exert dramatic cancer cell death and suppression in vivo due to the synergic effect of photothermal therapy (PTT) and photodynamic therapy (PDT). In marked contrast, 808 nm irradiation can only execute limited PTT to cancer cells, showing a relatively low inhibition rate in vitro and in vivo. This biodegradable MoO_x nanoplatform with synergetic PTT and PDT functionalities upon 1064 nm irradiation provided emerging opportunities for the phototherapy of cancer in nanomedicine.

Formation of Colloidal Copper Indium Sulfide Nanosheets by Two-Dimensional Self-Organization

Colloidal 2D semiconductor nanosheets (NSs) are an interesting new class of materials due to their unique properties. However, synthesis of these NSs is challenging, and synthesis procedures for materials other than the well-known Pb- and Cd-chalcogenides are still underdeveloped. In this paper, we present a new approach to make copper indium sulfide (CIS) NSs and study their structural and optical properties. The CIS NSs form via self-organization and oriented attachment of 2.5 nm chalcopyrite CuInS2 nanocrystals (NCs), yielding triangular- and hexagonal-shaped NSs with a thickness of ∼3 nm and lateral dimensions ranging from 20 to 1000 nm. The self-organization is induced by fast cation extraction, leading to attractive dipolar interactions between the NCs. Primary amines play a crucial role in the formation of the CIS NSs, both by forming in situ the cation extracting agent, and by preventing the attachment of NCs to the top and bottom facets of the NSs. Moreover, DFT calculations reveal that the amines are essential to stabilize the covellite crystal structure of the product CIS NSs. The NSs are indium-deficient and the off-stoichiometry gives rise to a plasmon resonance in the NIR spectral window.

Green synthesis of Au-Cu2-xSe heterodimer nanoparticles and their in-vitro cytotoxicity, photothermal assay

We demonstrate a new route for the synthesis of heterogeneous nanoparticles (NPs) composed of a gold domain (Au) and a heavily doped semiconductor domain (Cu_2-xSe) which exhibit a broad localized surface plasmon resonance (LSPR) arising from interactions between two nanocrystal domains. We also demonstrate the in-vitro cytotoxicity and photo thermal efficiency of as prepared Au-Cu_2-xSe heterodimer nanoparticles. This work establishes a new way of tuning LSPR by engineering the density of free charge carriers in two interacting domains.

Multifunctional Theranostic Agent of Cu2(OH)PO4 Quantum Dots for Photoacoustic Image-Guided Photothermal/Photodynamic Combination Cancer Therapy

Image-guided phototherapy is considered to be a prospective technique for cancer treatment because it can provide both oncotherapy and bioimaging, thus achieving an optimized therapeutic efficacy and higher treatment accuracy. Compared to complicated systems with multiple components, using a single material for this multifunctional purpose is preferable. In this work, we strategically fabricated poly(acrylic acid)- (PAA-) coated Cu₂(OH)PO₄ quantum dots [denoted as Cu₂(OH)PO₄@PAA QDs], which exhibit a strong near-infrared photoabsorption ability. As a result, an excellent photothermal conversion ability and the photoactivated formation of reactive oxygen species could be realized upon NIR irradiation, concurrently meeting the basic requirements for photothermal and photodynamic therapies. Moreover, phototherapeutic investigations on both cervical cancer cells in vitro and solid tumors of an in vivo mice model illustrated the effective antitumor effects of Cu₂(OH)PO₄@PAA upon 1064-nm laser irradiation, with no detectable lesions in major organs during treatment. Meanwhile, Cu₂(OH)PO₄@PAA is also an exogenous contrast for photoacoustic tomography (PAT) imaging to depict tumors under NIR irradiation. In brief, the Cu₂(OH)PO₄@PAA QDs prepared in this work are expected to serve as a multifunctional theranostic platform.

TiL4 -Coordinated Black Phosphorus Quantum Dots as an Efficient Contrast Agent for In Vivo Photoacoustic Imaging of Cancer

Black phosphorus quantum dots coordinated with a sulfonic ester of the titanium ligand are prepared and exhibit enhanced stability. In vitro and in vivo photoacoustic imaging applications demonstrate that the quantum dots can efficiently accumulate inside the tumor producing tumor profiles with high spatial resolution, demonstrating their potential as an efficient agent for photoacoustic imaging.

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.

Molecular imaging probes for multi-spectral optoacoustic tomography

In this review, we discuss recent progress in emerging optoacoustic probes, their mechanisms, applications and challenges for biological imaging using MSOT.

Au–Cu2−xSe heterogeneous nanocrystals for efficient photothermal heating for cancer therapy

In this study, we show that Au–Cu_2−xSe heterogeneous nanocrystals have great promise for use in photothermal therapy (PTT).

Nonstoichiometric copper chalcogenides for photo-activated alkyne/azide cycloaddition

Cu(i) present in nonstoichiometric copper chalcogenides and associated with copper vacancy defects is released under illumination, enabling efficient photo-activated catalysis of azide–alkyne cycloaddition reactions.

Ambient Aqueous Synthesis of Ultrasmall PEGylated Cu2-x Se Nanoparticles as a Multifunctional Theranostic Agent for Multimodal Imaging Guided Photothermal Therapy of Cancer

Ultrasmall PEGylated Cu_2-x Se nanoparticles with strong near-infrared absorption have been prepared by an ambient aqueous method. The resultant water-soluble and biocompatible nanoparticles are demonstrated to be a novel nanotheranostic agent for effective deep-tissue photoacoustic imaging, computed tomography imaging, single-photon emission computed tomography imaging, and photothermal therapy of cancer.

Biodegradable Nitrogen-Doped Carbon Nanodots for Non-Invasive Photoacoustic Imaging and Photothermal Therapy

Multifunctional nanoparticles have been widely investigated for biomedical applications, such as imaging, therapy, and drug delivery. Especially, photoactive nanoparticles have received great attention as theranostic agents because of their heat-generating abilities after exposure to laser irradiation. However, photostability and safety issues have been the technical hurdles for further clinical applications. Here, we designed nitrogen (N)-doped carbon nanodots (N-CNDs) that have strong absorption in the near-infrared region, high photostability, and excellent biodegradability. Optimized N-CNDs can be utilized not only as a new photoacoustic (PA) imaging agent but also as a superior photothermal therapy (PTT) agent in vivo because of their strong optical absorption at a specific wavelength. We used N-CNDs to perform in vivo/ex vivo noninvasive PA imaging of sentinel lymph nodes via local delivery and performed PTT for cancer ablation therapy. Finally, biodegradation and renal clearance were confirmed by performing whole-body PA monitoring and a degradation test.

A novel bacteriochlorin-gold nanoparticle construct for photoacoustic imaging

Herein we report the synthesis of new gold nanoparticle-bacteriochlorin conjugate (Au-NP-PS) as a highly efficient photoacoustic (PA) imaging agent. The conjugate was obtained by reacting a water soluble thio-bacteriochlorin (derived from bacteriochlorophyll-[Formula: see text] with Au-NP. The resulting NPs were characterized by UV-vis, TEM (transmission electron microscopy)/HRTEM (high resolution TEM) and diffraction pattern. The results obtained from in vitro studies suggest that due to conjugation between the PS and Au-NPs, the photoacoustic (PA) signals from the Au-NP-PS were greatly enhanced by a factor of 2.4 compared to that from PS alone.

Copper-Based Nanomaterials for Cancer Imaging and Therapy

Copper based nanoparticles (NPs) have attracted increased attention for biomedical applications. Copper chalcogenide NPs exhibit strong absorption in near-infrared region, demonstrate highly efficient light-to-heat transformation under near-infrared laser irradiation, and cause selective thermal destruction to the tumor. Smaller copper NPs display fluorescence signal and capability for optical imaging. Copper based NPs also serve as a versatile vehicle for drug delivery and image-guided therapy. This review covers recent advances related to the biomedical application of copper based NPs, with a focus on cancer imaging and therapy. We also discuss challenges to their successful clinical translation.

Multifunctional Inorganic Nanoparticles: Recent Progress in Thermal Therapy and Imaging

Nanotechnology has enabled the development of many alternative anti-cancer approaches, such as thermal therapies, which cause minimal damage to healthy cells. Current challenges in cancer treatment are the identification of the diseased area and its efficient treatment without generating many side effects. Image-guided therapies can be a useful tool to diagnose and treat the diseased tissue and they offer therapy and imaging using a single nanostructure. The present review mainly focuses on recent advances in the field of thermal therapy and imaging integrated with multifunctional inorganic nanoparticles. The main heating sources for heat-induced therapies are the surface plasmon resonance (SPR) in the near infrared region and alternating magnetic fields (AMFs). The different families of inorganic nanoparticles employed for SPR- and AMF-based thermal therapies and imaging are described. Furthermore, inorganic nanomaterials developed for multimodal therapies with different and multi-imaging modalities are presented in detail. Finally, relevant clinical perspectives and the future scope of inorganic nanoparticles in image-guided therapies are discussed.

The non-aqueous synthesis of shape controllable Cu(2-x)S plasmonic nanostructures in a continuous-flow millifluidic chip for the generation of photo-induced heating

In this paper, a new method for synthesizing non-aqueous copper sulfide nanocrystals with different shapes and sizes using a homemade continuous-flow millifluidic chip is presented. Conventionally, the shape control of nanocrystals was accomplished using a surfactant-controlled approach, where directional growth is facilitated by selective passivation of a particular facet of the nanocrystals using surfactants. We demonstrate a "surfactant-free" approach where different sizes and shapes (i.e. spherical, triangular prism and rod) of plasmonic copper sulfide (Cu(2-x)S) nanocrystals can be fabricated by adjusting the flow rate and precursor concentrations. As continuous-flow synthesis enables uniform heating and easy variation of precursors' stoichiometries, it serves as an excellent incubation platform for nanoparticles due to its simplicity and high reproducibility. Transmission electron microscopy (TEM), fast Fourier transform (FFT) and X-ray diffraction (XRD) techniques were used to characterize the as-synthesized nanocrystals and revealed structures ranging from copper-deficient covellite (CuS), spionkopite (Cu1.39S), roxbyite (Cu1.75S), to copper-rich djurleite (Cu1.94S). The localized surface plasmon resonance (LSPR) peak of the nanocrystals can be tuned from 1115 to 1644 nm by simply varying the copper to sulfur molar ratio and flow rate. Furthermore, photothermal effects of Cu(2-x)S nanocrystals were also demonstrated to annihilate the RAW264.7 cells upon near infra-red laser irradiation.

“Smart” gold nanoparticles for photoacoustic imaging: an imaging contrast agent responsive to the cancer microenvironment and signal amplification via pH-induced aggregation

pH-Responsive “smart” gold nanoparticles were demonstrated as a new photoacoustic imaging agent that can selectively respond to the cancer microenvironment and show the amplified signal in vivo.

Facile-synthesized ultrasmall CuS nanocrystals as drug nanocarriers for highly effective chemo–photothermal combination therapy of cancer

Combinational chemo–photothermal therapy has been considered as a promising strategy to enhance antitumor efficiency via synergistic effects for cancer treatments.

Near-IR responsive nanostructures for nanobiophotonics: emerging impacts on nanomedicine

Nanobiophotonics is an emerging field at the intersection of nanoscience, photonics, and biotechnology. Harnessing interactions of light with nanostructures enables new types of bioimaging, sensing, and light-activated therapy which can make a major impact on nanomedicine. Low penetration through tissue limits the use of visible light in nanomedicine. Near infrared (NIR) light (~780-1100 nm) can penetrate significantly further, enabling free-space delivery into deep tissues. This review focuses on interactions of NIR light with nanostructures to produce three effects: direct photoactivation, photothermal effects, and photochemical effects. Applications of direct photoactivation include bioimaging and biosensing using NIR-emitting quantum dots, materials with localized surface plasmon resonance (LSPR) in the NIR, and upconverting nanoparticles. Two key nanomedicine applications using photothermal effects are photothermal therapy (PTT), and photoacoustic (PA) imaging. For photochemical effects, we present the latest advances in in-situ upconversion and upconverting nanostructures for NIR activation of photodynamic therapy (PDT).

FROM THE CLINICAL EDITOR

Nanobiophotonics is a relatively new field applying light for the interactions with nanostructures, which can be used in bioimaging, sensing, and therapy. As near infrared (NIR) light (~780-1100 nm) can have better tissue penetration, its clinical potential is far greater. In this review, the authors discussed the latest research on the applications of NIR light in imaging and therapeutics.

Compact chelator-free Ni-integrated CuS nanoparticles with tunable near-infrared absorption and enhanced relaxivity for in vivo dual-modal photoacoustic/MR imaging

A chelator-free doping method is developed for constructing a Ni-integrated CuS nanostructure as a novel PA/MRI contrast agent. It exhibits tunable near-infrared absorption. Moreover, the hybrid nanostructure has demonstrated a dramatically enhanced T1 relaxivity compared with Ni ions. Due to these unique properties, chelator-free nanoparticles have been successfully applied for in vivo PA/MRI dual-modal imaging.

Dual-color photoacoustic lymph node imaging using nanoformulated naphthalocyanines

Demarking lymph node networks is important for cancer staging in clinical practice. Here, we demonstrate in vivo dual-color photoacoustic lymphangiography using all-organic nanoformulated naphthalocyanines (referred to as nanonaps). Nanonap frozen micelles were self-assembled from two different naphthalocyanine dyes with near-infrared absorption at 707 nm or 860 nm. These allowed for noninvasive, nonionizing, high resolution photoacoustic identification of separate lymphatic drainage systems in vivo. With both types of nanonaps, rat lymph nodes buried deeply below an exogenously-placed 10 mm thick layer of chicken breast were clearly visualized in vivo. These results show the potential of multispectral photoacoustic imaging with nanonaps for detailed mapping of lymphatic drainage systems.

Real-time Near-infrared Virtual Intraoperative Surgical Photoacoustic Microscopy

We developed a near infrared (NIR) virtual intraoperative surgical photoacoustic microscopy (NIR-VISPAM) system that combines a conventional surgical microscope and an NIR light photoacoustic microscopy (PAM) system. NIR-VISPAM can simultaneously visualize PA B-scan images at a maximum display rate of 45 Hz and display enlarged microscopic images on a surgeon's view plane through the ocular lenses of the surgical microscope as augmented reality. The use of the invisible NIR light eliminated the disturbance to the surgeon's vision caused by the visible PAM excitation laser in a previous report. Further, the maximum permissible laser pulse energy at this wavelength is approximately 5 times more than that at the visible spectral range. The use of a needle-type ultrasound transducer without any water bath for acoustic coupling can enhance convenience in an intraoperative environment. We successfully guided needle and injected carbon particles in biological tissues ex vivo and in melanoma-bearing mice in vivo.