Ultrafast synthesis of ultrasmall polyethylenimine-protected AgBiS2 nanodots by "rookie method" for in vivo dual-modal CT/PA imaging and simultaneous photothermal therapy

AgBiS2@CQDs/Ti nanocomposite coatings for combating implant-associated infections by photodynamic /photothermal therapy

Biofilm-mediated implant-associated infections are one of the most serious complications of implantation surgery, posing a grave threat to patient well-being. Effectively addressing bacterial infections is crucial for the success of implantation procedures. In this study, we prepared a bismuth sulfide silver@carbon quantum dot composite coating (AgBiS2@CQDs/Ti) on a medical titanium surface by surface engineering design to treat implant-associated infections. The photocatalytic/photothermal activity test results confirmed the excellent photogenerated ROS and photothermal properties of AgBiS2@CQDs/Ti under near-infrared laser irradiation. In vitro antibacterial and in vivo anti-infection experiments showed that the coating combined with photodynamic and photothermal therapies to eradicate bacteria and disrupt mature biofilms under 1064 nm laser irradiation. Consequently, AgBiS2@CQDs/Ti shows promise as an implant coating for treating implant-associated infections post-surgery, thereby enhancing the success rate of implantation procedures. This study also provides a new idea for combating implant-associated infections.

Bismuth-based two-dimensional nanomaterials for cancer diagnosis and treatment

The intrinsic high X-ray attenuation and insignificant biological toxicity of Bi-based nanomaterials make them a category of advanced materials in oncology. Bi-based two-dimensional nanomaterials have gained rapid development in cancer diagnosis and treatment owing to their adjustable bandgap structure, high specific surface area and strong NIR absorption. In addition to the single functional cancer diagnosis and treatment modalities, Bi-based two-dimensional nanomaterials have been certified for accomplishing multi-imaging guided multifunctional synergistic cancer therapies. In this review, we summarize the recent progress including controllable synthesis, defect engineering and surface modifications of Bi-based two-dimensional nanomaterials for cancer diagnosis and treatment in the past ten years. Their medical applications in cancer imaging and therapies are also presented. Finally, we discuss the potential challenges and future research priorities of Bi-based two-dimensional nanomaterials.

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

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

Upconversion nanoparticles@AgBiS2 core-shell nanoparticles with cancer-cell-specific cytotoxicity for combined photothermal and photodynamic therapy of cancers

UCNPs@AgBiS₂ core-shell nanoparticles that AgBiS₂ coated on the surface of upconversion nanoparticles (UCNPs) was successfully prepared through an ion exchange reaction. The photothermal conversion efficiency of AgBiS₂ can be improved from 14.7% to 45% due to the cross relaxation between Nd ions and AgBiS₂. The doping concentration of Nd ions played a critical role in the production of reactive oxygen species (ROS) and enhanced the photothermal conversion efficiency. The NaYF₄:Yb/Er/Nd@NaYF₄:Nd nanoparticles endows strong upconversion emissions when the doped concentration of Nd ions is 1% in the inner core, which excites the AgBiS₂ shell to produce ROS for photodynamic therapy (PDT) of cancer cells. As a result, the as-prepared NaYF₄:Yb/Er/Nd@NaYF₄:Nd@AgBiS₂ core-shell nanoparticles showed combined photothermal/photodynamic therapy (PTT/PDT) against malignant tumors. This work provides an alternative near-infrared light-active multimodal nanostructures for applications such as fighting against cancers.

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UCNPs@AgBiS₂ core-shell nanoparticles firstly prepared via a facile chemical process.

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The photothermal conversion efficiency for UCNPs@AgBiS₂ core-shell nanoparticles reached up to 45%.

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The as-prepared UCNPs@AgBiS₂ core-shell nanoparticles showed superoroir therapeutic efficacy for cancers.

Ultrasmall AgBiSe2 nanodots for CT/thermal imaging-guided photothermal tumor therapy in the NIR-II biowindow

Stimulus-responsive ternary chalcogenide nanomaterials are regarded as promising 'all-in-one' nanotheranostics agents on account of their tunable band structures and multi-metal intrinsic properties. Herein, ultrasmall AgBiSe₂ nanodots are prepared by a simple thermal injection method. It shows a narrow band gap of 0.91 eV and high absorption coefficient in the NIR-II biowindow, resulting in excellent photothermal performance. Under the irradiation of a 1064 nm laser, AgBiSe₂ can induce the overexpression of intracellular heat shock protein (Hsp70) and cell apoptosis to inhibit the growth of tumor cells. The strong signal from CT/thermal imaging also provides guidance for tumor diagnosis. Importantly, AgBiSe₂ can be rapidly excreted from the body, thus avoiding long term toxicity. This study presents the first biomedical application of AgBiSe₂ nanodots in cancer treatment and extends the development of ternary chalcogenide-based semiconductor nanomedicine.

Recent Progress Toward Imaging Application of Multifunction Sonosensitizers in Sonodynamic Therapy

Sonodynamic therapy (SDT) is a rapidly developing non-surgical therapy that initiates sensitizers’ catalytic reaction using ultrasound, showing great potential for cancer treatment due to its high safety and non-invasive nature. In addition, recent research has found that using different diagnostic and therapeutic methods in tandem can lead to better anticancer outcomes. Therefore, as essential components of SDT, sonosensitizers have been extensively explored to optimize their functions and integrate multiple medical fields. The review is based on five years of articles evaluating the combined use of SDT and imaging in treating cancer. By developing multifunctional sonosensitive particles that combine imaging and sonodynamic therapy, we have integrated diagnosis into the treatment of precision medicine applications, improving SDT cell uptake and antitumor efficacy utilizing different tumour models. This paper describes the imaging principle and the results of cellular and animal imaging of the multifunctional sonosensitizers. Efforts are made in this paper to provide data and design references for future SDT combined imaging research and clinical application development and to provide offer suggestions.

On-Demand Triggered Chemodynamic Therapy by NIR-II Light on Oxidation-Prevented Bismuth Nanodots

As the least toxic heavy metal, monoelemental bismuth nanomaterials with several superiorities are the ideal theranostic agents. However, bismuth nanoparticles are easily oxidized by oxygen in air or media, limiting their clinical application. In contrast, the oxidization of Bi⁰ to Bi³⁺ can activate the chemodynamic therapy (CDT) by transferring endogenous H₂O₂ into ^•OH. Herein, a well-designed Bi-DMSNs@PCM nanosystem was prepared via in situ growth of Bi nanodots and a coating of phase-change material (PCM) on the surface of dendritic mesoporous silica nanoparticles (DMSNs). The coated PCM protects the Bi nanodots from oxidation by keeping them in the Bi⁰ state for more than 15 d. When irradiated using the near infrared-II (NIR-II) laser with a low power density (0.5 W/cm²), the heat generated from the Bi nanodots melts the PCM shell to trigger CDT through a Fenton-like reaction, accompanied by heat-induced photothermal therapy (PTT). Notably, the CDT can also compensate for the reduced PTT effect caused by the oxidation of Bi nanodots, and a satisfactory treatment effect is realized. Additionally, photoacoustic and computed tomography imaging properties were obtained. Our strategy transfers the detrimental self-oxidation of bismuth to a beneficial therapeutic mode, enhancing the potential of Bi for clinical use.

Ultrasmall PEI-Decorated Bi2Se3 Nanodots as a Multifunctional Theranostic Nanoplatform for in vivo CT Imaging-Guided Cancer Photothermal Therapy

Bi-based nanomaterials, such as Bi2Se3, play an important part in biomedicine, such as photothermal therapy (PTT) and computed tomography (CT) imaging. Polyethylenimine (PEI)-modified ultrasmall Bi2Se3 nanodots were prepared using an ultrafast synthetic method at room temperature (25°C). Bi2Se3 nanodots exhibited superior CT imaging performance, and could be used as effective photothermal reagents owing to their broad absorption in the ultraviolet-visible-near infrared region. Under irradiation at 808 nm, PEI-Bi2Se3 nanodots exhibited excellent photothermal-conversion efficiency of up to 41.3%. Good biocompatibility and significant tumor-ablation capabilities were demonstrated in vitro and in vivo. These results revealed that PEI-Bi2Se3 nanodots are safe and a good nanotheranostic platform for CT imaging-guided PTT of cancer.

Carambola-like Bi2Te3 superstructures with enhanced photoabsorption for highly efficient photothermal therapy in the second near-infrared biowindow

Photothermal therapy (PTT) stimulated by light in the second near-infrared (NIR-II) biowindow shows great superiorities in the penetration ability of tissue and maximum permissible exposure (MPE). Exploring new photothermal agents with good optical absorbance in the NIR-II region is highly desirable for efficient cancer therapy. Herein, we successfully prepare carambola-like bismuth telluride (Bi₂Te₃) superstructures modified with PEGylated phospholipid (Bi₂Te₃@PEG) for CT imaging-guided PTT in the NIR-II biowindow. Attributing to their superstructures, Bi₂Te₃@PEG exhibited enhanced photoabsorption with higher photothermal conversion efficiency (55.3% for 1064 nm) compared with that of Bi₂Te₃ nanoparticles. Furthermore, the good X-ray attenuation capacity of Bi endows Bi₂Te₃@PEG with an outstanding performance as computed tomography (CT) contrast agents. Bi₂Te₃@PEG superstructures have been confirmed to effectively eliminate tumor in vitro and in vivo with negligible long-term toxicities, offering them great potential to act as theranostic platforms for cancer diagnosis and treatment.

How do bismuth-based nanomaterials function as promising theranostic agents for the tumor diagnosis and therapy?

The complexity of tumor microenvironment and the diversity of tumors seriously affect the therapeutic effect, the focus, therefore, has gradually been shifted from monotherapy to combination therapy in clinical research in order to improve the curative effect. The synergistic enhancement interactions among multiple monotherapies majorly contribute to the birth of the multi-mode cooperative therapy, whose effect of the treatment is clearly stronger than that of any single therapy. In addition, the accurate diagnosis of the tumour location is also crucial to the treatment. Bismuth-based nanomaterials (NMs) hold great properties as promising theranostic platforms based on their many unique features that include low toxicity, excellent photothermal conversion efficiency as well as high ability of X-ray computed tomography imaging and photoacoustic imaging. In this review, we will introduce briefly the main features of tumor microenvironment first and its effect on the mechanism of nanomedicine actions and present the recent advances of bismuth-based NMs for diagnosis and photothermal therapy-based combined therapies using bismuth-based NMs are presented, which may provide a new way for overcoming drug resistance and hypoxia. At the end, further challenges and outlooks regarding this promising field are discussed accompanied with some design tips for bismuth-based NMs, hoping to provide researchers some inspirations to design safe and effective nanotherapeutic agents for the clinical treatments of cancers.

NIR Laser Responsive Nanoparticles for Ovarian Cancer Targeted Combination Therapy with Dual-Modal Imaging Guidance

Purpose

Multifunctional nanoparticles with targeted therapeutic function and diagnostic-imaging are of great interest in the domain of precision therapy. NIR laser responsive nanoparticles (PLGA-PEG-FA encapsulating Bi₂S₃, PFP, and Dox (designed as FBPD NPs)) are synthesized for ovarian cancer targeted combination therapy with CT/PA dual-modal imaging guidance (PA: photoacoustic; CT: X-ray computed tomography).

Methods and Results

The FBPD NPS prepared by the double emulsification method revealed excellent dispersity, great stability, outstanding optical properties. The temperature of FBPD NPs increased rapidly after laser irradiation, inducing liquid-to-gas conversion of perfluoropentane (PFP), and promoting the release of Dox up to 86.7%. These FBPD NPs demonstrated their outstanding imaging capability for both PA and CT imaging both in vitro and in vivo, providing the potential for therapeutic guidance and monitoring. Assisted by folic acid, these nanoparticles could highly enrich in ovarian tumor tissue and the accumulation peaked at 3 h after intravenous administration. The desirable photothermal-conversion efficiency of the nanoparticles combined with chemotherapy achieved highly efficient therapy, which was demonstrated both in vitro and in vivo.

Conclusion

We successfully constructed multifunctional theranostic FBPD NPs for highly efficient PTT/chemotherapy combined therapy with dual CT/PA imaging guidance/monitoring. The unique nanoparticles with multiple abilities pave an emerging way toward precise treatment of ovarian cancer.

Mechanism Insight into Rapid Photodriven Sterilization Based on Silver Bismuth Sulfide Quantum Dots

Microbial contamination and the prevalence of resistant bacteria is considered a worldwide public health problem. Therefore, recently, great efforts have been made to develop photoresponsive platforms for the simultaneous photodynamic antibacterial (PDA) and photothermal antibacterial (PTA) therapy processes as mediated by specific light. However, owing to the absorption mismatches of the photothermal agents and photodynamic photosensitizers, it has been discovered that many synergistic photoresponsive antibacterial platforms cannot be excited by a single-wavelength light. In this study, silver bismuth sulfide quantum dots (AgBiS₂ QDs) identified from the literature as a near-infrared light (NIR) that triggers bifunctional materials with simultaneous photodynamic and photothermal effects for photoresponsive bacterial killing were used. Specifically, AgBiS₂ QDs were successfully synthesized via a bottom-up approach, using polyethylenimine (PEI) as an assistant molecule. With PEI wrapping, the attachment between the negatively charged membrane surfaces of the bacterial cells and AgBiS₂ QDs was enhanced via the electrostatic interactions. The photodriven antibacterial activity of AgBiS₂ QDs was then investigated against both S. aureus and E. coli. The results revealed a significant reduction in bacterial survival. The killing effect was found to be independent of the AgBiS₂ QDs, and redox potentials controlled the photogenerated electrons that thermodynamically favored the formation of multiple reactive oxygen species (ROS). A possible phototriggered antibacterial mechanism was then proposed in which the AgBiS₂ QDs are anchored first to the bacterial surface and then induce breaking on its outer membrane by high local heat and ROS under single 808 nm NIR laser illumination to finally induce bacterial death.

Bi19S27I3 nanorods: a new candidate for photothermal therapy in the first and second biological near-infrared windows

Near-infrared (NIR) light-induced photothermal cancer therapy using nanomaterials as photothermal agents has attracted considerable research interest over the past few years. As the key factor in photothermal therapy systems, a variety of photothermal agents have been developed. However, the exploration of novel photothermal therapy nanoplatforms with high NIR absorption remains a significant challenge, especially those working in both NIR-I and NIR-II windows. In this work, Bi19S27I3 nanorods with remarkably high absorption covering the whole visible light to the entire NIR-I and NIR-II regions have been successfully prepared through a facile solvothermal approach. The as-synthesized Bi19S27I3 nanorods have a high photothermal conversion efficiency of 42.7% at 808 nm (NIR-I) and 41.5% at 1064 nm (NIR-II), making them a promising candidate for photothermal therapy. In vitro cell viability assay reveals that the Bi19S27I3 sample has good biocompatibility and exhibits significant cell-killing effect under NIR irradiation. In vivo anti-tumor experiments demonstrate that the tumor growth can be effectively inhibited by fatal hyperthermia ablation mediated by Bi19S27I3 nanorods under the irradiation of an 808 nm or 1064 nm laser. Therefore, this study should be primarily beneficial for the development of new materials for NIR photothermal therapy applications.

Pnictogen Semimetal (Sb, Bi)-Based Nanomaterials for Cancer Imaging and Therapy: A Materials Perspective

Innovative multifunctional nanomaterials have attracted tremendous interest in current research by facilitating simultaneous cancer imaging and therapy. Among them, antimony (Sb)- and bismuth (Bi)-based nanoparticles are important species with multifunction to boost cancer theranostic efficacy. Despite the rapid development, the extensive previous work treated Sb- and Bi-based nanoparticles as mutually independent species, and therefore a thorough understanding of their relationship in cancer theranostics was lacking. We propose here that the identical chemical nature of Sb and Bi, being semimetals, provides their derived nanoparticles with inherent multifunction for near-infrared laser-driven and/or X-ray-based cancer imaging and therapy as well as some other imparted functions. An overview of recent progress on Sb- and Bi-based nanoparticles for cancer theranostics is provided to highlight the relationship between chemical nature and multifunction. The understanding of Sb- and Bi-based nanoparticles in this way might shed light on the further design of smart multifunctional nanoparticles for cancer theranostics.

Engineering Cu2−xS-conjugated upconverting nanocomposites for NIR-II light-induced enhanced chemodynamic/photothermal therapy of cancer

Cu2−xS-conjugated upconverting nanocomposites with an outstanding photothermal killing effect and a PT-enhanced CDT effect for NIR-II light-induced enhanced chemodynamic/photothermal therapy of cancer.

Ultrastable AgBiS2 Hollow Nanospheres with Cancer Cell-Specific Cytotoxicity for Multimodal Tumor Therapy

Specific cytotoxicity for catalytic nanomedicine triggered by the tumor microenvironment (TME) has attracted increasing interest. In this work, we prepared AgBiS₂ hollow nanospheres with narrow bandgaps via rapid precipitation in a weakly polar solvent, which lowered the intrinsic energy gap for the active production of highly reactive hydroxyl radicals (^•OH), especially in the TME. The as-prepared AgBiS₂ hollow nanospheres exhibited enhanced optical absorption and high photothermal conversion efficiency (44.2%). In addition, the hollow structured AgBiS₂ nanospheres were found to have a peroxidase-mimicking feature to induce cancer cell-specific cytotoxicity while exhibiting negligible cytotoxicity toward normal cells, which might be attributed to the efficient production of highly reactive ^•OH originating from the overexpression H₂O₂ in the TME caused by surface catalysis. In particular, the cancer cell-specific cytotoxicity of the nanospheres was greatly enhanced both in vitro and in vivo upon irradiation with a near-infrared (NIR) laser (808 nm). The above-mentioned features of the hollow structured AgBiS₂ will make it a promising candidate for tumor therapy.

Construction of thiol-capped ultrasmall Au-Bi bimetallic nanoparticles for X-ray CT imaging and enhanced antitumor therapy efficiency

Thiol capped gold nanoparticles with small size, high dispersity, and broad light absorption covering ultraviolet (UV) to near infrared (NIR) region have been developed for catalysis, fluorescence imaging and photodynamic therapy (PDT). The constitution of the metal core in such nanoparticles can strongly influence the luminescence, catalysis, and stability properties. However, to date, a corresponding investigation of the influence of the metallic core on the generation of reaction oxygen species (ROS) and its therapeutic efficiency towards tumor cells remains to be lacking. Herein, we fabricated bimetallic nanoparticles by introducing bismuth into captopril capped gold nanoparticles. Surprisingly, the introduction of the Bi was found enhance the photothermal effect of the nanoparticles to a great extent, and the variation trends for the thermal effect, ROS generation rate, and tumor cell inhibition effect were found to disparate with the changes in the Au and Bi composition. The origin of the photothermal effect was deduced through density functional theory calculations based on microscopic construction. Combined with the intrinsic photodynamic effect, the bimetallic nanoparticles showed an outstanding tumor cell inhibition effect. Furthermore, due to the excellent CT imaging property, our designed nanoparticles provide the exciting possibility to realize CT imaging guided and light-mediated tumor therapy.

X-ray-triggered NO-released Bi-SNO nanoparticles: all-in-one nano-radiosensitizer with photothermal/gas therapy for enhanced radiotherapy

Hypoxia in tumor cells is regarded as the most crucial cause of clinical drug resistance and radio-resistance; thus, relieving hypoxia of tumor cells is the key to enhancing the efficacy of anticancer therapy. As a gas signal molecule of vasodilatation factors, nitric oxide (NO) can relieve the hypoxia status of tumor cells, thereby, enhancing the sensitivity of tumor cells to radiotherapy. However, considering complications of vascular activity, the level of NO required for radiotherapy sensitization cannot be obtained in vivo. In view of this, we design and fabricate a multifunctional bismuth-based nanotheranostic agent, which is functionalized with S-nitrosothiol and termed Bi-SNO NPs. X-rays break down the S-N bond and simultaneously trigger large amount of NO-releasing (over 60 μM). Moreover, the as-prepared Bi-SNO NPs not only possess the capability of absorbing and converting 808 nm NIR photons into heat for photothermal therapy, but also have the ability to increase X-ray absorption and CT imaging sensitivity. In addition, the collaborative radio-, photothermal-, and gas-therapy of Bi-SNO in vivo was further investigated and remarkable synergistic tumor inhibition was realized. Finally, no obvious toxicity of Bi-SNO NPs was observed in the treated mice within 14 days. Therefore, the Bi-SNO developed in this work is an effective nano-agent for cancer theranostics with well-controlled morphology and uniform size (36 nm), which could serve as a versatile CT imaging-guided combined radio-, photothermal- and gas-therapy nanocomposite with negligible side effects.

Rapid synthesis of a Bi@ZIF-8 composite nanomaterial as a near-infrared-II (NIR-II) photothermal agent for the low-temperature photothermal therapy of hepatocellular carcinoma

Hepatocellular carcinoma is the fourth leading cause of cancer-related deaths globally. Advanced nanomaterials have emerged as effective approaches to liver cancer therapy such as photothermal therapy. However, limited penetration depth of photothermal agents (PTAs) activated in the NIR-I bio-window and thermoresistance due to heat shock proteins restrict the therapeutic efficacy of PTT in HCC. Herein, we prepared a Bi@ZIF-8 (BZ) nanomaterial by a simple one-step reduction method. Then, gambogic acid, a natural inhibitor of Hsp90, was efficiently loaded onto the BZ nanomaterial via physical mixing. The characterization of the nanomaterial and release of GA due to pH change or NIR-light irradiation were separately studied. Photothermal conversion efficiency was calculated, and therapeutic studies were carried out in vitro and in vivo. This nanomaterial exhibited a significantly enhanced drug release rate when the temperature was increased under acidic conditions and had good light stability under laser irradiation and a photothermal conversion efficiency of about 24.4%. In addition, this novel nanomaterial achieved good therapeutic effects with less toxicity in vitro. The BZ nanomaterial loaded with GA caused tumor shrinkage as well as disappearance and effectively downregulated Hsp90 expression in tumors in vivo. Moreover, this novel nanomaterial exhibited good biocompatibility and potential for application in low-temperature PTT with excellent tumor destruction efficacy.

Low-Cost RoHS Compliant Solution Processed Photovoltaics Enabled by Ambient Condition Synthesis of AgBiS2 Nanocrystals

Two major challenges exist before colloidal nanocrystal solar cells can take their place in the market: So far, these devices are based on Pb/Cd-containing nanocrystals, and second, the synthesis of these nanocrystals takes place in an inert atmosphere at elevated temperatures due to the use of air-sensitive chemicals. In this report, a room-temperature, ambient-air synthesis for nontoxic AgBiS2 nanocrystals is presented. As this method utilizes stable precursors, the need for the use of a protective environment is eliminated, enabling the large-scale production of AgBiS2 nanocrystals. The production cost of AgBiS2 NCs at room temperature and under ambient conditions reduces by ∼60% compared to prior reports based on hot injection, and the solar cells made of these nanocrystals yield a promising power conversion efficiency (PCE) of 5.5%, the highest reported to date for a colloidal nanocrystal material free of Pb or Cd synthesized at room temperature and under ambient conditions.

pH and Glutathione Synergistically Triggered Release and Self-Assembly of Au Nanospheres for Tumor Theranostics

Theranostic agents based on near-infrared absorption which integrate both imaging and therapeutic functions have attracted considerable attention. However, because of the interference signal, indiscriminate treatment usually causes side effects on normal tissues during tumor treatment. To address this limitation, we propose a new synergistically triggered mechanism, release and self-assembly of Au nanospheres, for tumor theranostics based on the synergistic effect of H⁺ and glutathione on the tumor microenvironment. In vitro experiments reveal that Au nanospheres release from Au@ZIF-8 at a high concentration of H⁺ or glutathione. Importantly, Au aggregation only appears in the synergistic effect of glutathione and lower pH and exhibits strong coupling plasmonic resonance absorption in the near-infrared region and can be used as the theranostics agent. This statement was further verified by biological transmission electron microscopy and in vivo imaging. Au@ZIF-8 is stable and produces no photoacoustic signal in normal tissue; in contrast, in the presence of overexpressed glutathione and H⁺, Au nanospheres release from Au@ZIF-8, assemble to aggregates, and exhibit a strong signal at the tumor site for imaging and efficient photothermal therapy. This work provides a new strategy for designing theranostic agents with sequentially responsive steps to avoid interference diagnosis signals from normal tissues and reduce damage to normal tissue during treatment.

Decoration of upconversion nanocrystals with metal sulfide quantum dots by a universal in situ controlled growth strategy

Conjugating transition-metal sulfide quantum dots and upconversion nanocrystals (UCNCs) has aroused widespread concern due to enhanced physical and chemical properties in contrast to only their simple sum. However, the synthesis of such hybrid nanoparticles by a universal in situ growth strategy has been scarcely reported so far. Herein, we developed a facile approach to functionalize NaYF₄:Yb/Er with chitosan (NaYF₄:Yb/Er@CS), which not only could improve the hydrophilicity of NaYF₄:Yb/Er, but also can form stable chelates with transition-metal ions. Then, ultrasmall metal sulfide (Mⁿ⁺S, M = Ag, Cu, Cd) quantum dots (QDs) can be conjugated homogeneously on the surface of NaYF₄:Yb/Er@CS. Taking Ag₂S as an example, the growth behavior of Ag₂S QDs on the surface of NaYF₄:Yb/Er@CS was studied specifically. The influence of the Ag : Y ratio, S : Ag ratio, pH value, reaction time and reaction temperature on the growth behavior of Ag₂S on the surface of NaYF₄:Yb/Er@CS was investigated systematically. Meanwhile, this innovative strategy is also suitable for the growth of ultrasmall QDs in various shapes, including plates, spheres and rods. The resultant NaYF₄:Yb/Er@CS@Ag₂S system possesses both upconversion luminescence (UCL) properties of NaYF₄:Yb/Er and a good photothermal conversion effect of Ag₂S, and is a promising candidate for UCL imaging guided PTT of cancer.

AgBiS2 nanoparticles with synergistic photodynamic and bioimaging properties for enhanced malignant tumor phototherapy

Bismuth (Bi)-based nanoagents for synergistic photodynamic therapy (PDT) and photothermal therapy (PTT) are attracting attention and are highly desired for malignant tumor diagnosis and treatment, but producing these materials is still a challenge. Here, we designed theranostic nanoparticles (NPs) based on AgBiS₂ for computed tomography (CT) imaging and phototherapy of malignant tumors. These AgBiS₂ NPs could effectively convert light into heat (with a high photothermal conversion efficiency of 36.51%) and significantly increase the generation of intracellular reactive oxygen species (ROS) under near infrared (NIR) laser irradiation. Remarkably, the combined PTT/PDT successfully inhibited the growth of a highly malignant osteosarcoma in vivo. In addition, AgBiS₂ NPs exhibited an enhanced CT contrast ability for tumor imaging and killed clinically derived Staphylococcus aureus (S. aureus) to prevent infection. In conclusion the ability of AgBiS₂ NPs to be used in phototherapy and CT imaging and their antibacterial abilities indicate that they are promising candidates for malignant tumor theranostics.

Fabrication of NaYF4:Yb3+,Tm3+-modified Ag nanocubes with upconversion luminescence and photothermal conversion properties

Herein, uniform Ag nanocube@NaYF₄:Yb³⁺,Tm³⁺ multifunctional nanocomposites were constructed by a facile synthetic strategy. Following the successful synthesis of Ag nanocubes, cubic phase NaYF₄:Yb³⁺,Tm³⁺ upconversion luminescent nanocrystals were modified on the surface of the Ag nanocubes, enhanced the mutual assistance of energy and versatility of the materials. Upon irradiation with a near-infrared laser, the nanocomposites exhibited excellent upconversion fluorescence and good photothermal conversion capability. Furthermore, the potential biological applications and biosafety of the Ag@NaYF₄:Yb³⁺,Tm³⁺ nanocomposites were also demonstrated; the obtained nanocomposites could achieve a good bactericidal performance and photothermal treatment of cancer cells, and they could be potentially applied in the biomedical field as a promising agent. Furthermore, this method provides a facile approach for synthesizing a multifunctional nanocomposite with different properties.

Ag nanocubes@NaYF₄:Yb³⁺,Tm³⁺ multifunctional nanocomposites with florescence and photothermal ability are fabricated by a facile strategy, which enhance the mutual assistance of energy and biological application.

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

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