Hydrogen Sulfide-Activatable Second Near-Infrared Fluorescent Nanoassemblies for Targeted Photothermal Cancer Therapy

Activatable Second Near-Infrared Fluorescent Probes: A New Accurate Diagnosis Strategy for Diseases

Recently, second near-infrared (NIR-II) fluorescent imaging has been widely applied in biomedical diagnosis, due to its high spatiotemporal resolution and deep tissue penetration. In contrast to the "always on" NIR-II fluorescent probes, the activatable NIR-II fluorescent probes have specific targeting to biological tissues, showing a higher imaging signal-to-background ratio and a lower detection limit. Therefore, it is of great significance to utilize disease-associated endogenous stimuli (such as pH values, enzyme existence, hypoxia condition and so on) to activate the NIR-II probes and achieve switchable fluorescent signals for specific deep bioimaging. This review introduces recent strategies and mechanisms for activatable NIR-II fluorescent probes and their applications in biosensing and bioimaging. Moreover, the potential challenges and perspectives of activatable NIR-II fluorescent probes are also discussed.

Fabrication of carbon dots for sequential on-off-on determination of Fe3+ and S2- in solid-phase sensing and anti-counterfeit printing

Glutathione and 2-aminopyridine are used as carbon sources to prepare carbon dots (CDs) by a one-step hydrothermal reaction. The results show that the average particle diameter of CDs is 8.64 nm with uniform size distribution and the fluorescence quantum yield is 13.62%. We further demonstrate that novel CDs possess highly selective sensing of Fe³⁺ from 0.2 to 200 μM with a low detection limit (0.194 μM). Meanwhile, the fluorescence of CDs can be repeated many times by the addition of S^2-. Moreover, the CDs are used for biological imaging of living cells with well cell penetrability and low toxicity. Furthermore, it is successfully applied for anti-counterfeiting and information encryption. More interestingly, it can be doped with hydrogel and filter paper to prepare solid-phase sensors exhibiting high sensitivity and fast response, demonstrating their tremendous potential for the simple, rapid, and low-cost monitoring of Fe³⁺ and S^2-.

Optical Imaging in the Second Near Infrared Window for Vascular Bioimaging

Optical imaging in the second near infrared region (NIR-II, 1000-1700 nm) provides higher resolution and deeper penetration depth for accurate and real-time vascular anatomy, blood dynamics, and function information, effectively contributing to the early diagnosis and curative effect assessment of vascular anomalies. Currently, NIR-II optical imaging demonstrates encouraging results including long-term monitoring of vascular injury and regeneration, real-time feedback of blood perfusion, tracking of lymphatic metastases, and imaging-guided surgery. This review summarizes the latest progresses of NIR-II optical imaging for angiography including fluorescence imaging, photoacoustic (PA) imaging, and optical coherence tomography (OCT). The development of current NIR-II fluorescence, PA, and OCT probes (i.e., single-walled carbon nanotubes, quantum dots, rare earth doped nanoparticles, noble metal-based nanostructures, organic dye-based probes, and semiconductor polymer nanoparticles), highlighting probe optimization regarding high brightness, longwave emission, and biocompatibility through chemical modification or nanotechnology, is first introduced. The application of NIR-II probes in angiography based on the classification of peripheral vascular, cerebrovascular, tumor vessel, and cardiovascular, is then reviewed. Major challenges and opportunities in the NIR-II optical imaging for vascular imaging are finally discussed.

Synergistic Therapy Using Doxorubicin-Loading and Nitric Oxide-Generating Hollow Prussian Blue Nanoparticles with Photoacoustic Imaging Potential Against Breast Cancer

Introduction

Traditional antitumor chemotherapy faces great challenges, such as multi-drug resistance (MDR) and poor penetration into tumor tissues. The newly emerging nitric oxide (NO)-based gas therapy has been recognized to reduce MDR and has improved permeation into tumor tissue.

Methods

In this study, NO-generating prodrug sodium nitroprusside (SNP) was doped to hollow mesoporous Prussian blue (PB) nanoparticles to fabricate NO-generating nanoparticles (NO-PB), which was further loaded with doxorubicin (DOX).

Results

DOX loaded NO-PB (DOX-NO-PB) was released quicker at pH 6 compared with neutral pH, suggesting NO-PB may facilitate the release of loaded drug in acidic tumor tissue. The capacity of NO production by NO-PB was measured, and the results showed the presence of NO in the culture medium from 4T1 cells incubated with NO-PB and inside the cells. NP-PB could be detected by photoacoustic imaging (PAI) in tumor tissue in 4T1 tumor bearing mice, suggesting this nanoparticle may serve as contrast agent for the noninvasive diagnosis of tumor tissues. NO-PB suppressed the growth of tissues in 4T1 tumor bearing mice. DOX-NO-PB showed more potent anti-tumor effects in 4T1 cells and tumor bearing mice compared with free DOX and NO-PB alone, indicating that the combination of DOX and NO-PB exhibited synergistic effects on tumor suppression.

Conclusion

This study provides a novel nanocarrier for gas therapy with additional PAI imaging capacity. This nanocarrier can be utilized for combination therapy of NO and chemotherapeutics which may serve as theranostic agents.

Precision photothermal therapy and photoacoustic imaging by in situ activatable thermoplasmonics

Phototherapy holds great promise for disease treatment; however, traditional "always-on" photoagents have been restricted to clinical translation due to their nonspecific response and side effects on normal tissues. Here, we show a tumor microenvironment activated photothermal and photoacoustic agent as an activatable prodrug and probe that allows precise cancer diagnosis and treatment. Such an in situ revitalized therapeutic and contrast agent is achieved via controllable plasmonic heating for thermoplasmonic activation. This enables monitoring of signal molecule dynamics, real-time photothermal and photoacoustic imaging of tumors and lymph node metastasis, and targeted photothermal therapy without unwanted phototoxicity to normal tissues. Our study provides a practical solution to the non-specificity problem in phototherapy and offers precision cancer therapeutic and theranostic strategies. This work may advance the development of ultrasensitive disease diagnosis and precision medicine.

Hyaluronic acid-modified manganese dioxide-enveloped hollow copper sulfide nanoparticles as a multifunctional system for the co-delivery of chemotherapeutic drugs and photosensitizers for efficient synergistic antitumor treatments

This paper presents the design of a new type of intelligent and versatile all-in-one therapeutic nanoplatform for the co-delivery of chemotherapeutic drugs and photosensitizers to facilitate multimodal antitumor treatment; the system is based on hyaluronic acid (HA)-modified manganese dioxide (MnO₂)-enveloped hollow porous copper sulfide (CuS) nanoparticles (CuS@MnO₂/HA NPs). In this system, a CuS inner shell allows for the co-loading of doxorubicin (DOX) and indocyanine green (ICG) and induces photothermal effects, and a biodegradable MnO₂ external shell affords on-demand tumor microenvironment (TME)-triggered release and catalase- andFenton-like activities. Moreover, the HA modification endows the system with a CD44 receptor-mediated tumor-targeting property. The formulated DOX and ICG co-loaded CuS@MnO₂/HA (DOX/ICG-CuS@MnO₂/HA) NPs were found to exhibit excellent photothermal performance both in vitro and in vivo. In addition, DOX/ICG-CuS@MnO₂/HA NPs were found to display both TME and near-infrared (NIR)-responsive controlled release properties. The NPs also have a superior reactive oxygen species (ROS) generation capacity due to the combination of enhanced ICG-induced singlet oxygen and CuS@MnO₂-mediated hydroxyl radicals. The cellular uptake, fluorescence imaging property, cytotoxicity, and thermal imaging of these NPs were also evaluated. In tumor-bearing mice, the DOX/ICG-CuS@MnO₂/HA NPs displayeda superior antitumor efficacy (2.57-fold) as compared with free DOX. Therefore, the developed DOX/ICG-CuS@MnO₂/HA NPs have a great potential for use as an all-in-one nanotherapeutic agent for the efficient and precise induction of chemo/photothermal/photodynamic/chemodynamic therapy with superior antitumor efficacy and fewer side effects.

Aromatic [b]-fused BODIPY dyes as promising near-infrared dyes

Far-red and near-infrared (NIR) absorbing/emitting dyes have found diverse applications in biomedicine and material science. However, the absorption and emission of classical BODIPY chromophores at short wavelength hamper their applications. Several strategies have been adopted to modify the structure of the BODIPY core to design NIR dyes. Among these, the most efficient approach to expand the π-conjugation of the BODIPY core is via fusion of aromatic rings. So far, many novel BODIPY skeletons fused to aromatic hydrocarbons and heterocycles at the b bond have been reported. This review comprehensively describes the recent advances regarding the development of aromatic [b]-fused BODIPY dyes with the focus on the design and synthesis, the relationships between their photophysical/spectroscopic properties and molecular structures, and the potential applications in bioassays and optoelectronic devices.

Hemicyanine-Based Near-Infrared Activatable Probes for Imaging and Diagnosis of Diseases

Molecular activatable probes with near-infrared (NIR) fluorescence play a critical role in in vivo imaging of biomarkers for drug screening and disease diagnosis. With structural diversity and high fluorescence quantum yields, hemicyanine dyes have emerged as a versatile scaffold for the construction of activatable optical probes. This Review presents a survey of hemicyanine-based NIR activatable probes (HNAPs) for in vivo imaging and early diagnosis of diseases. The molecular design principles of HNAPs towards activatable optical signaling against various biomarkers are discussed with a focus on their broad applications in the detection of diseases including inflammation, acute organ failure, skin diseases, intestinal diseases, and cancer. This progress not only proves the unique value of HNAPs in preclinical research but also highlights their high translational potential in clinical diagnosis.

Stimuli-activated molecular photothermal agents for cancer therapy

Taking advantage of activatable and imaging-guided properties, stimuli-activated molecular photothermal agents (MPTAs) have drawn great attention in photothermal therapy (PTT) over the past decades. In this review, the recent progress in the study of stimuli-activated MPTAs is summarized from different stimuli, including pH, bioactive small molecules, and enzymes. The features and challenges of stimuli-activated MPTAs are also discussed. This review aims to motivate readers to design and synthesise more efficient MPTAs.

In Situ Activatable Ratiometric NIR-II Fluorescence Nanoprobe for Quantitative Detection of H2S in Colon Cancer

As key characteristic molecules, several H₂S-activated probes have been explored for colon cancer studies. However, a few ratiometric fluorescence (FL) probes with NIR-II emissions have been reported for the quantitative detection of H₂S in colon cancer in vivo. Here, we developed an in situ H₂S-activatable ratiometric nanoprobe with two NIR-II emission signals for the detection of H₂S and intelligently lighting up colon cancer. The nanoprobe comprised a down conversion nanoparticle (DCNP), which emitted NIR-II FL at 1550 nm on irradiation with a 980 nm laser (F_{1550Em, 980Ex}). Further, human serum albumin (HSA) was combined with Ag⁺ on the surface of DCNP to form a DCNP@HSA-Ag⁺ nanoprobe. In the presence of H₂S, Ag₂S quantum dots (QDs) were formed in coated HSA, which emitted FL at approximately 1050 nm on irradiation with an 808 nm laser (F_{1050Em, 808Ex}) through an H₂S-induced chemical reaction between H₂S and Ag⁺; however, the FL signal of DCNP was stable at 1550 nm (F_{1550Em, 980Ex}), generating a H₂S concentration-dependent ratiometric F_{1050Em, 808Ex}/F_{1550Em, 980Ex} signal. The NIR-II ratiometric nanoprobe was successfully used for the accurate quantitative detection of H₂S and the detection of the precise location of colon cancer through an endogenous H₂S-induced in situ reduction reaction to form Ag₂S QDs. Thus, these findings provide a new strategy for the specific detection of targeted molecules and diagnosis of disease based on the in situ-activatable NIR-II ratiometric FL nanoprobe.

Chemodynamic nanomaterials for cancer theranostics

It is of utmost urgency to achieve effective and safe anticancer treatment with the increasing mortality rate of cancer. Novel anticancer drugs and strategies need to be designed for enhanced therapeutic efficacy. Fenton- and Fenton-like reaction-based chemodynamic therapy (CDT) are new strategies to enhance anticancer efficacy due to their capacity to generate reactive oxygen species (ROS) and oxygen (O2). On the one hand, the generated ROS can damage the cancer cells directly. On the other hand, the generated O2 can relieve the hypoxic condition in the tumor microenvironment (TME) which hinders efficient photodynamic therapy, radiotherapy, etc. Therefore, CDT can be used together with many other therapeutic strategies for synergistically enhanced combination therapy. The antitumor applications of Fenton- and Fenton-like reaction-based nanomaterials will be discussed in this review, including: (iþ) producing abundant ROS in-situ to kill cancer cells directly, (ii) enhancing therapeutic efficiency indirectly by Fenton reaction-mediated combination therapy, (iii) diagnosis and monitoring of cancer therapy. These strategies exhibit the potential of CDT-based nanomaterials for efficient cancer therapy.

Real-Time Imaging of Hepatic Inflammation Using Hydrogen Sulfide-Activatable Second Near-Infrared Luminescent Nanoprobes

The sensing and visualized monitoring of hydrogen sulfide (H₂S) in vivo is crucial to understand its physiological and pathological roles in human health and diseases. Common methods for H₂S detection require the destruction of the biosamples and are not suitable to be applied in vivo. In this Communication, we report a "turn-on" second near-infrared (NIR-II) luminescent approach for sensitive, real-time, and in situ H₂S detection, which is based on the absorption competition between the H₂S-responsive chromophores (compound 1) and the NIR-II luminescent lanthanide nanoparticles. Specifically, the luminescence was suppressed by compound 1 due to the competitive absorption of the incident light. In the presence of H₂S, the compound 1 was bleached to recover the luminescence. Thanks to the deep tissue penetration depth and the low absorbance/scattering on biological samples of the NIR-II nanoprobes, the monitoring of the endogenous H₂S in lipopolysaccharide-induced liver inflammation was achieved, which is unattainable by the conventional histopathological and serological approaches.

Responsive optical probes for deep-tissue imaging: Photoacoustics and second near-infrared fluorescence

Optical imaging has played a vital role in development of biomedicine and image-guided theragnostic. Nevertheless, the clinical translation of optical molecular imaging for deep-tissue visualization is still limited by poor signal-to-background ratio and low penetration depth owing to light scattering and tissue autofluorescence. Hence, to facilitate precise diagnosis and accurate surgery excision in clinical practices, the responsive optical probes (ROPs) are broadly designed for specific reaction with biological analytes or disease biomarkers via chemical/physical interactions for photoacoustic and second near-infrared fluorescence (NIR-II, 900-1700 nm) fluorescence imaging. Herein, the recent advances in the development of ROPs including molecular design principles, activated mechanisms and treatment responses for photoacoustic and NIR-II fluorescence imaging are reviewed. Furthermore, the present challenges and future perspectives of ROPs for deep-tissue imaging are also discussed.

γ-Glutamyl transpeptidase-activatable near-infrared nanoassembly for tumor fluorescence imaging-guided photothermal therapy

Rationale: Precise treatment of tumors is attracting increasing attention. Molecular probes simultaneously demonstrating the diagnostic signal and pharmacological effect in response to tumor microenvironment are highly desired. γ-glutamyl transpeptidase (GGT) is a biomarker with significantly up-regulated expression in the tumor area. We developed a GGT responsive near-infrared (NIR) nanoassembly for tumor-specific fluorescence imaging-guided photothermal therapy. Methods: The GGT responsive NIR probe was constructed by conjugating GGT-specific substrate γ-glutamic acid (γ-Glu) with cyanine fluorophore (NRh-NH2) via amide reaction. The resulting NRh-G spontaneously assembled into nanoparticles (NRh-G-NPs) around 50 nm. The NPs were characterized and the properties evaluated in the presence or absence of GGT. Subsequently, we studied fluorescence imaging and photothermal therapy of NRh-G-NPs in vitro and in vivo. Results: NRh-G-NPs, upon specific reaction with GGT, turned into NRh-NH2-NPs, showing a ~180-fold fluorescence enhancement and excellent photothermal effect recovery. NRh-G-NPs could selectively light up U87MG tumor cells while their fluorescence was weak in L02 human normal liver cells. The NPs also showed excellent tumor cell ablation upon laser irradiation. After intravenous injection into tumor-bearing mice, NRh-G-NPs could arrive in the tumor area and specifically light up the tumor. Following laser irradiation, the tumor could be completely erased with no tumor reoccurrence for up to 40 days. Conclusions: NRh-G-NPs were specifically responsive to GGT overexpressed in U87MG tumor cells and selectively lit up the tumor for imaging-guided therapy. Besides, the recovery of photothermal property in the tumor area could improve cancer therapy precision and decreased side effects in normal tissues.

Stimuli-activatable nanomaterials for phototherapy of cancer

Phototherapy including photothermal therapy (PTT) and photodynamic therapy (PDT), as non-invasive therapy approaches, have gained accumulated attention for cancer treatment in past years. PTT and PDT can generate local hyperthermia effects and reactive oxygen species (ROS) respectively, for tumor eradication. To improve the therapeutic performance while minimizing the reverse side effects of phototherapy, extensive efforts have been devoted to developing stimuli-activatable (e.g. pH, redox, ROS, enzyme, etc) nanomaterials for tumor-specific delivery/activation of the phototherapeutics. In this review, we first overviewed the recent advances of the engineered stimuli-responsive nanovectors for the phototherapy of cancer. We particularly summarized the progress of stimuli-activatable nanomaterials-based combinatory therapy strategies for augmenting the performance of phototherapy. We further discuss challenges for the clinical translation of nanomaterials-based phototherapy.

Activatable NIR-II Fluorescent Probes Applied in Biomedicine: Progress and Perspectives

With the advantage of inherent responsiveness that can change the spectroscopic signals from "off" to "on" state in responding to targets (e. g. biological analytes/microenvironmental factors), activatable fluorescent probes have attracted extensive attention and made significant progress in the field of bioimaging and biosensing. Due to the high depth of tissue penetration, minimal tissue damage and negligible background signal at longer wavelengths, the development of second near-infrared window (NIR-II) fluorescent materials provides a new opportunity to develop activable fluorescent probes. Here, we summarized properties, advantages and disadvantages of mainly NIR-II fluorophores (such as rare earth-doped nanoparticles, quantum dots, single-walled carbon nanotubes, small molecule dyes, conjugated polymers and gold nanoclusters), then overviewed current role and development of activatable NIR-II fluorescent probes (AFPs) for biomedical applications including biosensing, bioimaging and therapeutic. The potential challenges and perspectives of AFPs in deep-tissue imaging and clinical application are also discussed.

Nanomedicine Enables Drug-Potency Activation with Tumor Sensitivity and Hyperthermia Synergy in the Second Near-Infrared Biowindow

Disulfiram (DSF), a U.S. Food and Drug Administration (FDA)-approved drug for the treatment of chronic alcoholism, is also used as an antitumor drug in combination with Cu²⁺ ions. However, studies have shown that the endogenous Cu²⁺ dose in tumor tissues is still insufficient to form relatively high levels of a bis(N,N-diethyldithiocarbamate) copper(II) complex (denoted as Cu(DTC)₂) to selectively eradicate cancer cells. Here, DSF-loaded hollow copper sulfide nanoparticles (DSF@PEG-HCuSNPs) were designed to achieve tumor microenvironment (TME)-activated in situ formation of cytotoxic Cu(DTC)₂ for NIR-II-induced, photonic hyperthermia-enhanced, and DSF-initiated cancer chemotherapy. The acidic TME triggered the gradual degradation of DSF@PEG-HCuSNPs, promoting the rapid release of DSF and Cu²⁺ ions, causing the in situ formation of cytotoxic Cu(DTC)₂, to achieve efficient DSF-based chemotherapy. Additionally, DSF@PEG-HCuSNPs exhibited a notably high photothermal conversion efficiency of 23.8% at the second near-infrared (NIR-II) biowindow, thus significantly inducing photonic hyperthermia to eliminate cancer cells. Both in vitro and in vivo studies confirmed the effective photonic hyperthermia-induced chemotherapeutic efficacy of DSF by integrating the in situ formation of toxic Cu(DTC)₂ complexes and evident temperature elevation upon NIR-II laser irradiation. Thus, this study represents a distinctive paradigm of in situ Cu²⁺ chelation-initiated "nontoxicity-to-toxicity" transformation for photonic hyperthermia-augmented DSF-based cancer chemotherapy.

Temperature-Sensitive Lipid-Coated Carbon Nanotubes for Synergistic Photothermal Therapy and Gene Therapy

The combination of photothermal therapy (PTT) and gene therapy (GT) shows great potential to achieve synergistic anti-tumor activity. However, the lack of a controlled release of genes from carriers remains a severe hindrance. Herein, peptide lipid (PL) and sucrose laurate (SL) were used to coat single-walled carbon nanotubes (SCNTs) and multi-walled carbon nanotubes (MCNTs) to form bifunctional delivery systems (denoted SCNT-PS and MCNT-PS, respectively) with excellent temperature-sensitivity and photothermal performance. CNT/siRNA suppressed tumor growth by silencing survivin expression while exhibiting photothermal effects under near-infrared (NIR) light. SCNT-PS/siRNA showed very high anti-tumor activity, resulting in the complete inhibition of some tumors. It was highly efficient for systemic delivery to tumor sites and to facilitate siRNA release owing to the phase transition of the temperature-sensitive lipids, due to PL and SL coating. Thus, SCNT-PS/siRNA is a promising anti-tumor nanocarrier for combined PTT and GT.

Activable Multi-Modal Nanoprobes for Imaging Diagnosis and Therapy of Tumors

Malignant tumors have become one of the major causes of human death, but there remains a lack of effective methods for tiny tumor diagnosis, metastasis warning, clinical efficacy prediction, and effective treatment. In this context, localizing tiny tumors via imaging and non-invasively extracting molecular information related to tumor proliferation, invasion, metastasis, and drug resistance from the tumor microenvironment have become the most fundamental tasks faced by cancer researchers. Tumor-associated microenvironmental physiological parameters, such as hypoxia, acidic extracellular pH, protease, reducing conditions, and so forth, have much to do with prognostic indicators for cancer progression, and impact therapeutic administrations. By combining with various novel nanoparticle-based activatable probes, molecular imaging technologies can provide a feasible approach to visualize tumor-associated microenvironment parameters noninvasively and realize accurate treatment of tumors. This review focuses on the recent achievements in the design of “smart” nanomedicine responding to the tumor microenvironment-related features and highlights state-of- the-art technology in tumor imaging diagnosis and therapy.

Which is Better for Nanomedicines: Nanocatalysts or Single-Atom Catalysts?

With the rapid advancements in nanotechnology and materials science, numerous nanomaterials have been used as catalysts for nanomedical applications. Their design and modification according to the microenvironment of diseases have been shown to achieve effective treatment. Chemists are in pursuit of nanocatalysts that are more efficient, controllable, and less toxic by developing innovative synthetic technologies and improving existing ones. Recently, single-atom catalysts (SACs) with excellent catalytic activity and high selectivity have attracted increasing attention because of their accurate design as nanomaterials at the atomic level, thereby highlighting their potential for nanomedical applications. In this review, the recent advances in nanocatalysts and SACs are briefly summarized according to their synthesis, characterizations, catalytic mechanisms, and nanomedical applications. The opportunities and future scope for their development and the issues and challenges for their application as nanomedicine are also discussed. As far as it is known, the review is the systematic comparison of nanocatalysts and SACs, especially in the field of nanomedicine, which has promoted the development of nanocatalytic medicine.

Tailor-Made Nanomaterials for Diagnosis and Therapy of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers worldwide due to its aggressiveness and the challenge to early diagnosis and treatment. In recent decades, nanomaterials have received increasing attention for diagnosis and therapy of PDAC. However, these designs are mainly focused on the macroscopic tumor therapeutic effect, while the crucial nano-bio interactions in the heterogeneous microenvironment of PDAC remain poorly understood. As a result, the majority of potent nanomedicines show limited performance in ameliorating PDAC in clinical translation. Therefore, exploiting the unique nature of the PDAC by detecting potential biomarkers together with a deep understanding of nano-bio interactions that occur in the tumor microenvironment is pivotal to the design of PDAC-tailored effective nanomedicine. This review will introduce tailor-made nanomaterials-enabled laboratory tests and advanced noninvasive imaging technologies for early and accurate diagnosis of PDAC. Moreover, the fabrication of a myriad of tailor-made nanomaterials for various PDAC therapeutic modalities will be reviewed. Furthermore, much preferred theranostic multifunctional nanomaterials for imaging-guided therapies of PDAC will be elaborated. Lastly, the prospects of these nanomaterials in terms of clinical translation and potential breakthroughs will be briefly discussed.

Recent Progress on Biomaterials Fighting against Viruses

Viruses not only pose severe threats to public health, but also influence the development of society. Over the past decade, rapid advances have been seen in the application of nanomaterials to virus research. As an interdisciplinary field, nanotechnology offers powerful functions because the structures of nanomaterials are unique, with remarkable physicochemical properties and excellent biocompatibility. Nanomaterials have been developed for virus detection and tracking and for antiviral strategies, to better understand viruses and reduce viral infections, implying a bright future for this field. Herein, the recent advances are systematically summarized regarding the nanomaterials used in viral studies. Representative applications of nanomaterials to viral detection and tracking are described. The antiviral effects achieved with nanomaterials based on different mechanisms are also described, including entry inhibition, inhibition of viral replication, and immunological enhancement. The current challenges and future opportunities in this promising field are also discussed.

Tumor microenvironment-activated NIR-II reagents for tumor imaging and therapy

Second near-infrared window (NIR-II, 1000-1700 nm) absorption and fluorescent agents have attracted great attention because they can overcome the penetration limitation of the first near-infrared window (NIR-I, 750-1000 nm). However, these always "on" agents face the severe problem of being susceptible to retention and phagocytosis by the reticuloendothelial system after intravenous administration, which results in signal interference during diagnosis and side effects during treatment. Accordingly, tumor microenvironment-responsive smart agents (smart NIR-II agents), whose imaging and therapeutic functions can only be triggered in tumors, can overcome this limitation. Thus, NIR-II smart agents, which exhibit a combined response to the tumor microenvironment and NIR-II, make full use of the advantages of both triggers and improve the precision diagnosis and effective treatment of cancer. This review summarizes the recent advances in tumor microenvironment-activated NIR-II agents for tumor diagnosis and treatment, including smart NIR-II fluorescence imaging, photoacoustic imaging, photothermal therapy and photodynamic therapy. Finally, the challenges and perspectives of NIR-II smart agents for tumor diagnosis and treatment are proposed.

Research Progress of Thermosensitive Hydrogel in Tumor Therapeutic

Compared with traditional tumor therapy strategies, hydrogel as a drug reservoir system can realize on-demand drug release and deep tissue penetration ability. It also exhibits great tumor-site retention to enhance the permeability and retention effect of tumor treatment. This can significantly overcome the drug's resistance and severe side effects. Inorganic/organic composite hydrogel has attracted wide attention due to its combined effects, enhancing therapeutic effects against various kinds of tumors. In situ injectable hydrogel can securely restrict the drugs in the lesion sites without leakage and guarantee better biosafety. Moreover, hydrogel possesses interconnected macropores which can provide enough space for nutrient transport, cellular activity, and cell-cell interactions. Thermal therapy is an effective strategy for tumor therapy due to its minimal invasiveness and high selectivity. Because the location temperature can be precisely controlled and helps avoid the risks of destroying the body's immune system and ablate normal cells, thermal therapy exhibits significant treatment outcomes. Nonetheless, when the cellular temperature reaches approximately 43 °C, it causes long-term cell inactivation. Based on these merits, thermosensitive hydrogel formulation with adaptive functions shows excellent efficacy, unlimited tissue penetration capacity, and few deleterious side effects. Furthermore, the thermosensitive hydrogel has unique physical properties under the external stimuli, which is the ideal drug delivery system for on-demand release in tumor treatment. This article will review the state of the thermosensitive hydrogel in clinic application for cancer therapy.

Aptamer-Functionalized Upconverting Nanoformulations for Light-Switching Cancer-Specific Recognition and In Situ Photodynamic-Chemo Sequential Theranostics

Biomarker-activatable theranostic formulations offer the potential for removing specific tumors with a high diagnostic accuracy and a significant pharmacological effect. Herein, we developed a novel activatable theranostic nanoformulation UAS-PD [upconversion nanophosphor (UCNP)-aptamer/ssDNA-pyropheophorbide-a (PPA)-doxyrubicin (DOX)], which can recognize specific cancer cells with sensitivity and trigger the localized photodynamic destruction and enhanced chemotherapy. UAS-PD was constructed by the conjugation of UCNPs and aptamer probes containing the photosensitizer PPA and the chemotherapeutic drug DOX. When cancer cells are present, the UAS-PD specifically binds to PTK7, an overexpressed protein present on the surface of cancer cells, through conformational recombination of the aptamer structure and switches its upconversion luminescence from 655 to 540 nm. This long-lived ratiometric optical signal provides an ultrasensitive detection limit as low as 3.9 nM for PTK7. Changes in the conformation of UAS-PD can also induce PPA to approach UCNPs, which can produce cytotoxic singlet oxygens under near-infrared excitation to destroy the cell membrane and enhance its permeability for the simultaneously released DOX that targets cellular DNA degradation, which results in a highly effective tumor-killing effect by synergistic extra-intracellular sequential damage.

Hydrogen sulfide-activatable prodrug-backboned block copolymer micelles for delivery of chemotherapeutics

A novel hydrogen sulfide-activatable block copolymer prodrug with high tumor specificity was developed for cancer chemotherapy.

Recent Progress in the Development of Multifunctional Nanoplatform for Precise Tumor Phototherapy

Phototherapy, including photodynamic therapy and photothermal therapy, mainly relies on phototherapeutic agents (PAs) to produce heat or toxic reactive oxygen species (ROS) to kill tumors. It has attracted wide attention due to its merits of noninvasive properties and negligible drug resistance. However, the phototoxicity of conventional PAs is one of the main challenges for its potential clinical application. This is mainly caused by the uncontrolled distribution of PA in vivo, as well as the inevitable damage to healthy cells along the light path. Ensuring the generation of ROS or heat specific at tumor site is the key for precise tumor phototherapy. In this review, the progress of targeted delivery of PA and activatable phototherapy strategies based on nanocarriers for precise tumor therapy is summarized. The research progress of passive targeting, active targeting, and activatable targeting strategies in the delivery of PA is also described. Then, the switchable nanosystems for tumor precise phototherapy in response to tumor microenvironment, including pH, glutathione (GSH), protein, and nucleic acid, are highlighted. Finally, the challenges and opportunities of nanocarrier-based precise phototherapy are discussed for clinical application in the future.

Sensing and Bioimaging of the Gaseous Signaling Molecule Hydrogen Sulfide by Near-Infrared Fluorescent Probes

A fluorescent probe for the monitoring of H₂S levels in living cells and organisms is highly desirable. In this regard, near-infrared (NIR) fluorescent probes have emerged as a promising tool. NIR-I and NIR-II probes have many significant advantages; for instance, NIR light penetrates deeper into tissue than light at visible wavelengths, and it causes less photodamage during biosample analysis and less autofluorescence, enabling higher signal-to-background ratios. Therefore, it is expected that fluorescent probes having emission in the NIR region are more suitable for in vivo imaging. Consequently, a considerable increase in reports of new H₂S-responsive NIR fluorescent probes appeared in the literature. This review highlights the advances made in developing new NIR fluorescent probes aimed at the sensitive and selective detection of H₂S in biological samples. Their applications in real-time monitoring of H₂S in cells and in vivo for bioimaging of living cells/animals are emphasized. The selection of suitable dyes for designing NIR fluorescent probes, along with the principles and mechanisms involved for the sensing of H₂S in the NIR region, are described. The discussions are focused on small-molecule and nanomaterials-based NIR probes.

Thermosensitive Polymer Dot Nanocomposites for Trimodal Computed Tomography/Photoacoustic/Fluorescence Imaging-Guided Synergistic Chemo-Photothermal Therapy

Precision delivery of theranostic agents to the tumor site is essential to improve their diagnostic and therapeutic efficacy and concurrently minimize adverse effects during treatment. In this study, a novel concept of near-infrared (NIR) light activation of conjugated polymer dots (Pdots) at thermosensitive hydrogel nanostructures is introduced for multimodal imaging-guided synergistic chemo-photothermal therapy. Interestingly, owing to the attractive photothermal conversion efficiency of Pdots, the Pdots@hydrogel as theranostic agents is able to undergo a controllable softening or melting state under the irradiation of NIR laser, resulting in light-triggered drug release in a controlled way and concurrently hydrogel degradation. Besides, the novel Pdots@hydrogel nanoplatform can serve as the theranostic agent for enhanced trimodal photoacoustic (PA)/computed tomography (CT)/fluorescence (FL) imaging-guided synergistic chemo-photothermal therapy of tumors. More importantly, the constructed intelligent nanocomposite Pdots@hydrogel exhibits excellent biodegradability, strong NIR absorption, bright PA/CT/FL signals, and superior tumor ablation effect. Therefore, the concept of a light-controlled multifunctional Pdots@hydrogel that integrates multiple diagnostic/therapeutic modalities into one nanoplatform can potentially be applied as a smart nanotheranostic agent to various perspectives of personalized nanomedicine.

A review: Red/near-infrared (NIR) fluorescent probes based on nucleophilic reactions of H2 S since 2015

The topics of human health and disease are always the focus of much attention. Hydrogen sulfide (H₂ S), as a double-edged sword, plays an important role in biological systems. Studies have revealed that endogenous H₂ S is important to maintain normal physiological functions. Conversely, abnormal levels of H₂ S may contribute to various diseases. Due to the importance of H₂ S in physiology and pathology, research into the effects of H₂ S has been active in recent years. Fluorescent probes with red/near-infrared (NIR) emissions (620-900 nm) are more suitable for imaging applications in vivo, because of their negligible photodamage, deep tissue penetration, and maximum lack of interference from background autofluorescence. H₂ S, an 'evil and positive' molecule, is not only toxic, but also produces significant effects; a 'greedy' molecule, is not only a strong nucleophile under physiological conditions, but also undergoes a continuous double nucleophilic reaction. Therefore, in this tutorial review, we will highlight recent advances made since 2015 in the development and application of red/NIR fluorescent probes based on nucleophilic reactions of H₂ S.

H2 S-Scavenged and Activated Iron Oxide-Hydroxide Nanospindles for MRI-Guided Photothermal Therapy and Ferroptosis in Colon Cancer

Overproduced hydrogen sulfide (H₂ S) is of vital importance for the progress of colon cancer and promotes cancer cellular proliferation. Devising pharmacological nanomaterials for tumor-specific H₂ S activation will be significant for precise colon cancer treatment. Herein, a biocompatible fusiform iron oxide-hydroxide nanospindles (FeOOH NSs) nanosystem for magnetic resonance imaging (MRI), ferroptosis, and H₂ S based cascade reaction-enhanced combinational colon cancer treatment is developed. The FeOOH NSs can effectively scavenge endogenous H₂ S via the reduction reaction to prohibit the growth of CT26 colon cancer. The cascade produced FeS driven by overexpressed H₂ S exhibits near-infrared-triggered photothermal therapy capability and Fe²⁺ -mediated ferroptosis functionality. Meanwhile, the as-prepared FeOOH NSs can light up tumor tissues as a potent MRI contrast agent. Additionally, FeOOH NSs present desirable biosafety in a murine model for up to three months and avoid any long-term toxicity. Furthermore, it is found that these H₂ S-responsible nanotheranostics do not cause any cure effects on other cancer types, such as 4T1 breast cancer. Overall, the findings illustrate that the biocompatible FeOOH NSs can be successfully employed as a theranostic for specifically treating colon cancer, which may promote the clinical translation and development of H₂ S-responsive nanoplatforms.

In Vivo Imaging of Senescent Vascular Cells in Atherosclerotic Mice Using a β-Galactosidase-Activatable Nanoprobe

Senescence-associated diseases have severely diminished the quality of life and health of patients. However, a sensitive assay of these diseases remains limited due to a lack of straightforward methods. Considering that senescence-associated β-galactosidase (SA-β-Gal) is overexpressed in senescent cells, the detection of SA-β-Gal in senescent cells and tissues might be a feasible strategy for the early diagnosis of SA diseases. In this study, a β-galactosidase-activatable nanoprobe BOD-L-βGal-NPs was developed for the imaging of senescent cells and vasculature in atherosclerotic mice via real-time monitoring of β-Gal. BOD-L-βGal-NPs was fabricated by encapsulating a newly designed NIR ratiometric probe BOD-L-βGal within a poly(lactic-co-glycolic) acid (PLGA) core. Nanoprobe BOD-L-βGal-NPs showed good accumulation in arteries, thus successfully visualizing senescent cells and vasculature in atherosclerotic mice by tail vein injection. Our findings indicated that nanoprobe BOD-L-βGal-NPs holds great potential for the early diagnosis and therapy of atherosclerosis and other aging-associated diseases.

Aggregation Enhanced Responsiveness of Rationally Designed Probes to Hydrogen Sulfide for Targeted Cancer Imaging

Activatable molecular probes hold great promise for targeted cancer imaging. However, the hydrophobic nature of most conventional probes makes them generate precipitated agglomerate in aqueous media, thereby annihilating their responsiveness to analytes and precluding their practical applications for bioimaging. This study reports the development of two small molecular probes with unprecedented aggregation enhanced responsiveness to H₂S for in vivo imaging of H₂S-rich cancers. The subtle modulation of the equilibrium between hydrophilicity and lipophilicity by N-methylpyridinium endows these designed probes with the capability of spontaneously self-assembling into nanoprobes under physiological conditions. Such probes in an aggregated state, rather than a molecular dissolved state, show NIR fluorescence light up and photoacoustic signals turn on upon H₂S specific activation, allowing in vivo visualization and differentiation of cancers based on differences in H₂S content. Thus, our study presents an effective design strategy which should pave the way to molecular design of optimized probes for precision cancer diagnostics.

A ratiometric fluorescent probe for imaging enzyme dependent hydrogen sulfide variation in the mitochondria and in living mice

Developing a ratiometric H₂S fluorescent probe with fast response is of great importance for studying the H₂S physiology. Herein, two hemicyanine-based H₂S probes were constructed; the one with a propanoic acid group (CouPa) showed poor sensitivity while the other one with the N,N-diethylpropionamide moiety (CouDE) exhibited distinctly improved performance. CouDE showed the ability to detect mitochondrial H₂S level fluctuation, which was triggered by alteration of CBS enzyme activity. Moreover, endogenous H₂S change in solid tumours was monitored using CouDE.

Mitochondria-Targeting Organic Nanoparticles for Enhanced Photodynamic/Photothermal Therapy

Organelle-targeting techniques have been proved to be promising approaches for enhanced cancer treatment, especially phototherapy, because it can greatly improve the efficiency of photosensitizers. In this work, we designed and synthesized a mitochondria-targeting diketopyrrolopyrrole-based photosensitizer (DPP2+) for synergistic photodynamic/photothermal therapy upon irradiation. The obtained mitochondria-targeting nanoparticles (DPP2+ NPs) could produce thermal energy and singlet oxygen under 635 nm laser irradiation with ideal cytocompatibility. Importantly, DPP2+ NPs are more likely to enter the cells and target mitochondria. In in vitro and in vivo antitumor experiments, DPP2+ NPs showed highly effective antitumor effects, suggesting that mitochondria-targeting photosensitizers have potential for cancer treatment. The present work provides an alternative strategy to mitochondria-targeting molecular engineering and highlights the potential of organic nanomaterials in biomedical fields and cancer treatment.

Ultrasmall Rhodium Nanozyme with RONS Scavenging and Photothermal Activities for Anti-Inflammation and Antitumor Theranostics of Colon Diseases

Colitis-associated colorectal cancer (CAC), in which chronic inflammation is a well-recognized carcinogen, requires concurrent anti-inflammation and antitumor treatments in the clinic. Herein, we report polyethylene glycol (PEG)-coated (PEGylated) ultrasmall rhodium nanodots (Rh-PEG NDs) can serve as a metallic nanozyme with reactive oxygen and nitrogen species (RONS) scavenging properties as well as photothermal activities for anti-inflammation and antitumor theranostics in colon diseases. Benefiting from multienzyme activities against RONS, Rh-PEG NDs can decrease the levels of pro-inflammatory cytokines (TNF-α, IL-6), resulting in good anti-inflammatory effect on dextran sulfate sodium-induced colitis. By virtue of high photothermal conversion efficiency (48.9%), Rh-PEG NDs demonstrate complete ablation of CT-26 colon tumor without any recurrence. Most importantly, Rh-PEG NDs exhibit good biocompatibility both at the cellular and animal levels. Our findings provide a paradigm to utilize metallic nanozymes for the potential management of colon diseases.

Chiral Cux OS@ZIF-8 Nanostructures for Ultrasensitive Quantification of Hydrogen Sulfide In Vivo

In this study, a Cu_x OS@ZIF-8 nanostructure is fabricated to quantify the levels of hydrogen sulfide (H₂ S) in living cells and in vivo. Zeolitic lmidazolate framework-8 (ZIF-8) is chosen as an encapsulation shell to improve the selectivity of this probe. Using this unique nanostructure, ultrasensitive quantification and bioimaging of H₂ S in living cells are successfully achieved. The lower limit of detection is 0.8 and 5.3 nmol per 10⁶ cells for circular dichroism and fluorescence modes, respectively. It is found that the chiral Cu_x OS NPs transformed into achiral Cu_x S NPs contribute to the ultrasensitive detection. Notably, this probe can also be carried out to detect and track H₂ S levels in tumor-bearing animals. The discoveries put forward for the creation of a detection platform for quantitative tracking and analysis in clinic.

Semiconducting Polymer Nanomaterials as Near-Infrared Photoactivatable Protherapeutics for Cancer

Cancer therapy is routinely performed in the clinic to cure cancer and control its progression, wherein therapeutic agents are generally used. To reduce side effects, protherapeutic agents that can be activated by overexpressed cancer biomarkers are under development. However, these agents still face certain extent of off-target activation in normal tissues, stimulating the interest to design external-stimuli activatable protherapeutics. In this regard, photoactivatable protherapeutic agents have been utilized for cancer treatments. However, because of the intrinsic features of photolabile moieties, most photoactivatable protherapeutic agents only respond to ultraviolet-visible light, limiting their in vivo applications. Thus, protherapeutic agents that can be activated by near-infrared (NIR) light with minimal phototoxicity and increased tissue penetration are highly desired.In this Account, we summarize our semiconducting polymer nanomaterials (SPNs) as NIR photoactivatable protherapeutic agents for cancer treatment. SPNs are transformed from π-conjugated polymers that efficiently convert NIR light into heat or singlet oxygen (¹O₂). With photothermal and photodynamic properties, SPNs can be directly used as photomedicine or serve as light transducers to activate heat or ¹O₂-responsive protherapeutic agents.The heat-activatable SPN-based protherapeutic agents are developed by loading or conjugating of SPNs with therapeutic agents (e.g., agonist, gene, and enzyme). For instance, photothermally triggered release of agonists specifically activates certain protein ion channels on the cellular membrane, leading to ion overinflux induced mitochondria dysfunction and consequently apoptosis of cancer cells. Moreover, photothermal activation of temperature-sensitive bromelain can promote the in situ degradation of collagens (the major components of extracellular matrix), resulting in an improved accumulation of agents in tumor tissues and thus amplified therapeutic outcome.The ¹O₂-activatable SPN-based protherapeutic agents are constructed through covalent conjugation of SPNs with caged therapeutic agents via hypoxia- or ¹O₂-cleavable linkers. Upon NIR photoirradiation, SPNs consume oxygen to generate ¹O₂, which leads to photodynamic therapy (PDT), and meanwhile breaks hypoxia- or ¹O₂-cleavable linkers for on-demand release and in situ activation of caged protherapeutic molecules (e.g., chemodrug, enzyme, and inhibitor). Such remote activation of SPN-based protherapeutic agents can be applied to induce DNA damage, ribonucleic acid degradation, inhibition of protein biosynthesis, or immune system activation in tumors of living animals. By synergizing PDT with NIR photoactivation of those biological actions, these protherapeutic agents effectively eliminate tumors and even fully inhibit tumor metastasis.This Account highlights the potential of SPNs for construction of versatile NIR photoactivatable protherapeutics to treat cancer at designated times and locations with high therapeutic outcome and precision.

Advanced Near-Infrared Light for Monitoring and Modulating the Spatiotemporal Dynamics of Cell Functions in Living Systems

Light-based technique, including optical imaging and photoregulation, has become one of the most important tools for both fundamental research and clinical practice, such as cell signal sensing, cancer diagnosis, tissue engineering, drug delivery, visual regulation, neuromodulation, and disease treatment. In particular, low energy near-infrared (NIR, 700-1700 nm) light possesses lower phototoxicity and higher tissue penetration depth in living systems as compared with ultraviolet/visible light, making it a promising tool for in vivo applications. Currently, the NIR light-based imaging and photoregulation strategies have offered a possibility to real-time sense and/or modulate specific cellular events in deep tissues with subcellular accuracy. Herein, the recent progress with respect to NIR light for monitoring and modulating the spatiotemporal dynamics of cell functions in living systems are summarized. In particular, the applications of NIR light-based techniques in cancer theranostics, regenerative medicine, and neuroscience research are systematically introduced and discussed. In addition, the challenges and prospects for NIR light-based cell sensing and regulating techniques are comprehensively discussed.

Zwitterionic Polymer Coating of Sulfur Dioxide-Releasing Nanosystem Augments Tumor Accumulation and Treatment Efficacy

Multiple drug resistance (MDR) exhibited by cancer cells and low intratumor accumulation of chemotherapeutics are the main obstacles in cancer chemotherapy. Herein, the preparation of a redox-responsive sulfur dioxide (SO₂ )-releasing nanosystem, with high SO₂ -loading capacity, aimed at improving the treatment efficacy of cancers exhibiting MDR is described. The multifunctional nanomedicine (MON-DN@PCBMA-DOX) is designed and constructed by coating mesoporous organosilica nanoparticles with a zwitterionic polymer, poly(carboxybetaine methacrylate) (PCBMA), which can concurrently load SO₂ prodrug molecules (DN, 2,4-dinitrobenzenesulfonylchloride) and chemotherapeutics (DOX, doxorubicin). The generated SO₂ molecules can sensitize cells to chemotherapy and overcome the MDR by downregulating the expression of P-glycoprotein. Furthermore, the PCBMA coating prolongs the blood circulation time of the inner core, leading to an increased intratumor accumulation of the nanomedicine. Owing to the prolonged blood circulation, enhanced tumor accumulation, and SO₂ sensitization of cells to chemotherapy, the nanomedicine exhibits excellent tumor suppression with a tumor inhibition rate of 94.8%, and might provide a new platform for cancer therapy.

Strategies for engineering advanced nanomedicines for gas therapy of cancer

As an emerging and promising treatment method, gas therapy has attracted more and more attention for treatment of inflammation-related diseases, especially cancer. However, therapeutic/therapy-assisted gases (NO, CO, H₂S, H₂, O₂, SO₂ and CO₂) and most of their prodrugs lack the abilities of active intratumoral accumulation and controlled gas release, resulting in limited cancer therapy efficacy and potential side effects. Therefore, development of nanomedicines to realize tumor-targeted and controlled release of therapeutic/therapy-assisted gases is greatly desired, and also the combination of other therapeutic modes with gas therapy by multifunctional nanocarrier platforms can augment cancer therapy efficacy and also reduce their side effects. The design of nanomedicines with these functions is vitally important, but challenging. In this review, we summarize a series of engineering strategies for construction of advanced gas-releasing nanomedicines from four aspects: (1) stimuli-responsive strategies for controlled gas release; (2) catalytic strategies for controlled gas release; (3) tumor-targeted gas delivery strategies; (4) multi-model combination strategies based on gas therapy. Moreover, we highlight current issues and gaps in knowledge, and envisage current trends and future prospects of advanced nanomedicines for gas therapy of cancer. This review aims to inspire and guide the engineering of advanced gas-releasing nanomedicines.