Single-layer MoS2 nanosheet grafted upconversion nanoparticles for near-infrared fluorescence imaging-guided deep tissue cancer phototherapy

Harnessing the power of targeted metal nanocarriers mediated photodynamic and photothermal therapy

The treatment of cancer has become a profoundly intricate procedure. Traditional treatment methods, including chemotherapy, surgery and radiotherapy, have been utilized, while notable progress has been achieved in recent years. Among targeted therapies for cancer, folic acid (FA) conjugated metal-based nanoparticles (NP) have emerged as an innovative strategy, namely for photodynamic therapy (PDT) and photothermal therapy (PTT). These NP exploit the strong attraction between FA and folate receptors, which are excessively produced in several cancer cells, in order to enable precise administration and improved effectiveness of treatment. During PDT, metal-based NP functionalized with FA are used as photosensitizers which are activated by light, and produce reactive oxygen species that cause cancer cells to undergo apoptosis. Within the framework of PTT, these NP effectively transform light energy into concentrated heat, specifically targeting and destroying tumor cells. This review examines the fundamental mechanisms by which these NP improve the effectiveness of PDT and PTT while simultaneously presenting important findings that demonstrate the effectiveness of FA-functionalized MNP in laboratory and animal models. In addition, the paper also discusses the problems and potential directions for their clinical translation.

A Sensitive Enzymatic Electrochemical Biosensor for Cholesterol Based on Cobalt Ferrite@Molybdenum Disulfide/Gold Nanoparticles

Cholesterol is essential in biological systems, and the level of cholesterol in the body of a person acts as a diagnostic marker for a variety of diseases. So, in this work, we fabricated an enzymatic electrochemical biosensor for cholesterol using cobalt ferrite@molybdenum disulfide/gold nanoparticles (CoFe2O4@MoS2/Au). The synthesized composite was used for the determination of cholesterol by voltametric methods. The electroactive material CoFe2O4@MoS2/Au was successfully verified from the physiochemical studies such as XRD, Raman, FT-IR, and XPS spectroscopy along with morphological FESEM and HRTEM characterization. CoFe2O4@MoS2/Au showed outstanding dispersion in the aqueous phase, a large effective area, good biological compatibility, and superior electronic conductivity. The microflower-like CoFe2O4@MoS2/Au was confirmed by scanning electron microscopy. The image of transmission electron microscopy showed decoration of gold nanoparticles on CoFe2O4@MoS2 surfaces. Furthermore, a one-step dip-coating technique was used to build the biosensor used for cholesterol detection. In addition to acting as an enabling matrix to immobilize cholesterol oxidase (ChOx), CoFe2O4@MoS2/Au contributes to an increase in electrical conductivity. The differential pulse voltammetry method was used for the quantitative measurement of cholesterol. The calibration curve for cholesterol was linear in the concentration range of 5 to 100 μM, with a low limit of detection of 0.09 μM and sensitivity of 0.194 μA μM-1 cm-2. Furthermore, the biosensor demonstrates good practicability, as it was also employed for identifying cholesterol in real samples with acceptable selectivity and stability.

Recent progress of UCNPs-MoS2 nanocomposites as a platform for biological applications

Composite materials can take advantages of the functional benefits of multiple pure nanomaterials to a greater degree than single nanomaterials alone. The UCNPs-MoS2 composite is a nano-application platform that combines upconversion luminescence and photothermal properties. Upconversion nanoparticles (UCNPs) are inorganic nanomaterials with long-wavelength excitation and short-wavelength tunable emission capabilities, and are able to effectively convert near-infrared (NIR) light into visible light for increased photostability. However, UCNPs have a low capacity for absorbing visible light, whereas MoS2 shows better absorption in the ultraviolet and visible regions. By integrating the benefits of UCNPs and MoS2, UCNPs-MoS2 nanocomposites can convert NIR light with a higher depth of detection into visible light for application with MoS2 through fluorescence resonance energy transfer (FRET), which compensates for the issues of MoS2's low tissue penetration light-absorbing wavelengths and expands its potential biological applications. Therefore, starting from the construction of UCNPs-MoS2 nanoplatforms, herein, we review the research progress in biological applications, including biosensing, phototherapy, bioimaging, and targeted drug delivery. Additionally, the current challenges and future development trends of UCNPs-MoS2 nanocomposites for biological applications are also discussed.

Nanomaterials for light-mediated therapeutics in deep tissue

Light-mediated therapeutics, including photodynamic therapy, photothermal therapy and light-triggered drug delivery, have been widely studied due to their high specificity and effective therapy. However, conventional light-mediated therapies usually depend on the activation of light-sensitive molecules with UV or visible light, which have poor penetration in biological tissues. Over the past decade, efforts have been made to engineer nanosystems that can generate luminescence through excitation with near-infrared (NIR) light, ultrasound or X-ray. Certain nanosystems can even carry out light-mediated therapy through chemiluminescence, eliminating the need for external activation. Compared to UV or visible light, these 4 excitation modes penetrate more deeply into biological tissues, triggering light-mediated therapy in deeper tissues. In this review, we systematically report the design and mechanisms of different luminescent nanosystems excited by the 4 excitation sources, methods to enhance the generated luminescence, and recent applications of such nanosystems in deep tissue light-mediated therapeutics.

Fast detection of Staphylococcus aureus using thiol-functionalized WS2 quantum dots and Bi2O2Se nanosheets hybrid through a fluorescence recovery mechanism

Ultrafast and sensitive detection of Staphylococcus aureus (S. aureus), a harmful Gram-positive human pathogenic bacterium, by two-dimensional layered materials continues to be a challenge. Herein, we have studied the sensing of S. aureus using a tungsten disulfide (WS2) quantum dot (QD) and bismuth oxyselenide (Bi2O2Se) nanosheet (NS) hybrid through their unique optical functionalities. The WS2 QDs of a mean diameter of 2.5 nm were synthesized by liquid exfoliation. Due to the quantum confinement and functional groups, the WS2 QDs exhibit high fluorescence (FL) yield under UV excitation. The addition of Bi2O2Se NSs resulted in the adsorption of WS2 QDs on their surface, resulting in quenching of the FL emission due to nonfluorescent complex formation between the WS2 QDs and Bi2O2Se NSs. A specific sequencing single-standard DNA (ssDNA) aptamer, which identifies and explicitly binds with S. aureus, was attached to the defect sites of the WS2 QDs for selective detection. The thiol-modified ssDNA aptamers attach covalently to the WS2 QD defect sites, which was confirmed by Raman and X-ray photoelectron spectroscopy (XPS). The interaction of S. aureus with the aptamer functionalized WS2 QDs weakens the van der Waals interaction between the WS2 QDs and Bi2O2Se NSs, which results in the detachment of the WS2 QDs from the Bi2O2Se NS surface and restores the FL intensity of the WS2 QDs, thus allowing the efficient detection of S. aureus. Similar measurements with non-targeted bacteria show that the system is quite selective towards S. aureus. Our FL-based biosensor has a linear response in the range of 103-107 CFU mL-1 (colony formation unit mL-1) with a detection limit of 580 CFU mL-1. We have observed a fast response time of 15 minutes for sensing, which is superior to the previous reports. The proposed system was tested in human urine and can detect S. aureus in human urine samples selectively, proving its potential in real-life applications. The reported approach is versatile enough for sensing other biomolecules and metal ions by choosing suitable receptors.

Multifunctional Oxidized Dextran as a Matrix for Stabilization of Octahedral Molybdenum and Tungsten Iodide Clusters in Aqueous Media

Due to their high abundance, polymeric character, and chemical tunability, polysaccharides are perfect candidates for the stabilization of photoactive nanoscale objects, which are of great interest in modern science but can be unstable in aqueous media. In this work, we have demonstrated the relevance of oxidized dextran polysaccharide, obtained via a simple reaction with H₂O₂, towards the stabilization of photoactive octahedral molybdenum and tungsten iodide cluster complexes [M₆I₈}(DMSO)₆](NO₃)₄ in aqueous and culture media. The cluster-containing materials were obtained by co-precipitation of the starting reagents in DMSO solution. According to the data obtained, the amount and ratio of functional carbonyl and carboxylic groups as well as the molecular weight of oxidized dextran strongly affect the extent of stabilization, i.e., high loading of aldehyde groups and high molecular weight increase the stability, while acidic groups have some negative impact on the stability. The most stable material based on the tungsten cluster complex exhibited low dark and moderate photoinduced cytotoxicity, which together with high cellular uptake makes these polymers promising for the fields of bioimaging and PDT.

Peptide functionalized actively targeted MoS2 nanospheres for fluorescence imaging-guided controllable pH-responsive drug delivery and collaborative chemo/photodynamic therapy

The combination of imaging and different therapeutic strategies into one single nanoplatform often demonstrates improved efficacy over monotherapy in cancer treatments. Herein, a multifunctional nanoplatform (labelled as MPRD) based on molybdenum disulfide quantum dots (MoS₂ QDs) is developed to achieve enhanced antitumor efficiency by integrating fluorescence imaging, tumor-targeting and synergistic chemo/photodynamic therapy (PDT) into one system. First, polyethylene glycol (PEG)ylated MoS₂ QDs (MP) with desirable stability are synthesized via a hydrothermal process using MoS₂ QDs and carboxyamino-terminated oligomeric PEG as raw materials. Then, MP were conjugated with arginine-glycine-aspartic acid (RGD) peptide via amidation to form a novel nanocarrier (MPR), which possesses strong blue fluorescence, good biocompatibility and α_νβ₃ receptor-mediated targeting ability. More importantly, MPR generated reactive oxygen species under 808 nm laser activation to realize targeted antitumor PDT. Further doxorubicin (DOX) was loaded onto MPR, which endows MPRD with localized chemotherapy and pH-responsive drug release. The MPRD exhibits improved chemotherapy performance on HepG2 cells (overexpressing integrin α_νβ₃) owing to enhanced cellular uptake mediated by α_νβ₃ receptor and effective drug release triggered by intracellular pH. Notably, MPRD with efficient tumor targeting ability and high chemo/PDT efficacy under NIR laser irradiation is capable of inhibiting HepG2 tumor cell growth both in vitro and in vivo, which is significantly superior to each individual therapy. These findings demonstrate that MPRD holds great potential in effective cancer therapy.

Using host-guest interactions at the interface of quantum dots to load drug molecules for biocompatible, safe, and effective chemo-photodynamic therapy against cancer

Combining photodynamic therapy (PDT) and chemotherapy (CHT) by loading an anti-cancer drug and a photosensitizer (PS) into the same delivery nanosystem has been proposed as an effective approach to achieve synergistic effects for a safe cancer treatment. However, exploring an ideal delivery nanosystem has been challenging, because the noncovalent interactions must be maintained between the multiple components to produce a stable yet responsive nanostructure that takes into account the encapsulation of drug molecules. We addressed this issue by engineering the interfacial interaction between Ag₂S quantum dots (QDs) using a pillararene derivative to direct the co-self-assembly of the entire system. The high surface area-to-volume ratio of the Ag₂S QDs provided ample hydrophobic space to accommodate the anti-drug molecule doxrubicine. Moreover, Ag₂S QDs served as PSs triggered by 808 nm near-infrared (NIR) light and also as carriers for high-efficiency delivery of drug molecules to the tumor site. Drug release experiments showed smart drug release under the acidic microenvironments (pH 5.5) in tumor cells. Additionally, the Ag₂S QDs demonstrated outstanding PDT ability under NIR light, as confirmed by extracellular and intracellular reactive oxygen species generation. Significant treatment efficacy of the chemo-photodynamic synergistic therapy for cancer using the co-delivery system was demonstrated via in vitro and in vivo studies. These findings suggest that our system offers intelligent control of CHT and PDT, which will provide a promising strategy for constructing hybrid systems with synergistic effects for advanced applications in biomedicine, catalysis, and optoelectronics.

Photon Upconversion in Small Molecules

Upconversion (UC) is a process that describes the emission of shorter-wavelength light compared to that of the excitation source. Thus, UC is also referred to as anti-Stokes emission because the excitation wavelength is longer than the emission wavelength. UC materials are used in many fields, from electronics to medicine. The objective of using UC in medical research is to synthesize upconversion nanoparticles (UCNPs) composed of a lanthanide core with a coating of adsorbed dye that will generate fluorescence after excitation with near-infrared light to illuminate deep tissue. Emission occurs in the visible and UV range, and excitation mainly in the near-infrared spectrum. UC is observed for lanthanide ions due to the arrangement of their energy levels resulting from f-f electronic transitions. Organic compounds and transition metal ions are also able to form the UC process. Biocompatible UCNPs are designed to absorb infrared light and emit visible light in the UC process. Fluorescent dyes are adsorbed to UCNPs and employed in PDT to achieve deeper tissue effects upon irradiation with infrared light. Fluorescent UCNPs afford selectivity as they may be activated only by illumination of an area of diseased tissue, such as a tumor, with infrared light and are by themselves atoxic in the absence of infrared light. UCNP constructs can be monitored as to their location in the body and uptake by cancer cells, aiding in evaluation of exact doses required to treat the targeted cancer. In this paper, we review current research in UC studies and UCNP development.

Two-dimensional nanomaterials-added dynamism in 3D printing and bioprinting of biomedical platforms: Unique opportunities and challenges

The nanomaterials research spectrum has seen the continuous emergence of two-dimensional (2D) materials over the years. These highly anisotropic and ultrathin materials have found special attention in developing biomedical platforms for therapeutic applications, biosensing, drug delivery, and regenerative medicine. Three-dimensional (3D) printing and bioprinting technologies have emerged as promising tools in medical applications. The convergence of 2D nanomaterials with 3D printing has extended the application dynamics of available biomaterials to 3D printable inks and bioinks. Furthermore, the unique properties of 2D nanomaterials have imparted multifunctionalities to 3D printed constructs applicable to several biomedical applications. 2D nanomaterials such as graphene and its derivatives have long been the interest of researchers working in this area. Beyond graphene, a range of emerging 2D nanomaterials, such as layered silicates, black phosphorus, transition metal dichalcogenides, transition metal oxides, hexagonal boron nitride, and MXenes, are being explored for the multitude of biomedical applications. Better understandings on both the local and systemic toxicity of these materials have also emerged over the years. This review focuses on state-of-art 3D fabrication and biofabrication of biomedical platforms facilitated by 2D nanomaterials, with the comprehensive summary of studies focusing on the toxicity of these materials. We highlight the dynamism added by 2D nanomaterials in the printing process and the functionality of printed constructs.

A near-infrared triggered upconversion/MoS2 nanoplatform for tumour-targeted chemo-photodynamic combination therapy

The combination of photodynamic therapy and chemotherapy has shown a great potential in cancer treatment. As a promising photosensitizer, MoS₂ quantum dots (QDs) have limited application due to the low tissue penetration of its light absorbing wavelength in the ultraviolet and visible regions. For the purpose of utilizing MoS₂QDs in higher NIR absorption region, herein, we constructed a core/shell nano-photosensitizer upconversion@MoS₂ with doxorubicin loading. This nanoplatform can convert 980 nm NIR into visible light, activating MoS₂QDs to produce reactive oxygen species through fluorescence resonance energy transfer. In addition, this nanoplatform presented good biocompatibility and tumor targeting after polyethylene glycol and folic acid modification. Interestingly, with pH-responsive drug release performance, this nanoplatform presented efficient chemotherapy effects. Thus, the tumour-targeted nanoplatform can achieve up-converted luminescence imaging guided chemo-photodynamic synergistic therapy effectively.

Acid-Sensitive Nanoparticles Based on Molybdenum Disulfide for Photothermal-Chemo Therapy

The combination of multiple treatments has recently been investigated for tumor treatment. In this study, molybdenum disulfide (MoS₂) with excellent photothermal conversion performance was used as the core, and manganese dioxide (MnO₂), which responds to the tumor microenvironment, was loaded on its surface by liquid deposition to form a mesoporous core-shell structure. Then, the chemotherapeutic drug Adriamycin (DOX) was loaded into the hole. To further enhance its water solubility and stability, the surface of MnO₂ was modified with mPEG-NH₂ to prepare the combined antitumor nanocomposite MoS₂@DOX/MnO₂-PEG (MDMP). The results showed that MDMP had a diameter of about 236 nm, its photothermal conversion efficiency was 33.7%, and the loading and release rates of DOX were 13 and 65%, respectively. During in vivo and in vitro studies, MDMP showed excellent antitumor activity. Under the combined treatment, the tumor cell viability rate was only 11.8%. This nanocomposite exhibits considerable potential for chemo-photothermal combined antitumor therapy.

MoS2-based nanocomposites for cancer diagnosis and therapy

Molybdenum is a trace dietary element necessary for the survival of humans. Some molybdenum-bearing enzymes are involved in key metabolic activities in the human body (such as xanthine oxidase, aldehyde oxidase and sulfite oxidase). Many molybdenum-based compounds have been widely used in biomedical research. Especially, MoS2-nanomaterials have attracted more attention in cancer diagnosis and treatment recently because of their unique physical and chemical properties. MoS2 can adsorb various biomolecules and drug molecules via covalent or non-covalent interactions because it is easy to modify and possess a high specific surface area, improving its tumor targeting and colloidal stability, as well as accuracy and sensitivity for detecting specific biomarkers. At the same time, in the near-infrared (NIR) window, MoS2 has excellent optical absorption and prominent photothermal conversion efficiency, which can achieve NIR-based phototherapy and NIR-responsive controlled drug-release. Significantly, the modified MoS2-nanocomposite can specifically respond to the tumor microenvironment, leading to drug accumulation in the tumor site increased, reducing its side effects on non-cancerous tissues, and improved therapeutic effect. In this review, we introduced the latest developments of MoS2-nanocomposites in cancer diagnosis and therapy, mainly focusing on biosensors, bioimaging, chemotherapy, phototherapy, microwave hyperthermia, and combination therapy. Furthermore, we also discuss the current challenges and prospects of MoS2-nanocomposites in cancer treatment.

Low-dimensional nanomaterials for antibacterial applications

The excessive use of antibiotics has led to a rise in drug-resistant bacteria. These "superbugs" are continuously emerging and becoming increasingly harder to treat. As a result, new and effective treatment protocols that have minimal risks of generating drug-resistant bacteria are urgently required. Advanced nanomaterials are particularly promising due to their drug loading/releasing capabilities combined with their potential photodynamic/photothermal therapeutic properties. In this review, 0-dimensional, 1-dimensional, 2-dimensional, and 3-dimensional nanomaterial-based systems are comprehensively discussed for bacterial-based diagnostic and treatment applications. Since the use of these platforms as antibacterials is relatively new, this review will provide appropriate insight into their construction and applications. As such, we hope this review will inspire researchers to explore antibacterial-based nanomaterials with the aim of developing systems for clinical applications.

Molybdenum disulfide nanosheets: From exfoliation preparation to biosensing and cancer therapy applications

Over the past few decades, nanotechnology has developed rapidly. Various nanomaterials have been gradually applied in different fields. As a kind of two-dimensional (2D) layered nanomaterial with a graphene-like structure, molybdenum disulfide (MoS₂) nanosheets have broad research prospects in the fields of tumor photothermal therapy, biosensors and other biomedical fields because of their unique band gap structure and physical, chemical and optical properties. In this paper, the latest research progress on MoS₂ is briefly summarized. Several commonly used exfoliation methods for the preparation of MoS₂ nanosheets are reviewed based on the studies in the past five years. Additionally, the current research status of MoS₂ nanosheets in the field of biomedicine is introduced. At the end of this review, a brief overview of the limitations of MoS₂ research and its future prospects in the field of biomedicine is also provided.

Application of rare earth-doped nanoparticles in biological imaging and tumor treatment

Rare earth-doped nanoparticles have been widely used in disease diagnosis, drug delivery, tumor therapy, and bioimaging. Among various bioimaging methods, the fluorescence imaging technology based on the rare earth-doped nanoparticles can visually display the cell activity and lesion evolution in living animals, which is a powerful tool in biological technology and has being widely applied in medical and biological fields. Especially in the band of near infrared (700–1700 nm), the emissions show the characteristics of deep penetration due to low absorption, low photon scattering, and low autofluorescence interference. Furthermore, the rare earth-doped nanoparticles can be endowed with the water solubility, biocompatibility, drug-loading ability, and the targeting ability for different tumors by surface functionalization. This confirms its potential in the cancer diagnosis and treatment. In this review, we summarized the recent progress in the application of rare earth-doped nanoparticles in the field of bioimaging and tumor treatment. The luminescent mechanism, properties, and structure design were also discussed.

Immunostimulatory Potential of MoS2 Nanosheets: Enhancing Dendritic Cell Maturation, Migration and T Cell Elicitation

BACKGROUND

Due to their extraordinary physical and chemical properties, MoS2 nanosheets (MSNs) are becoming more widely used in nanomedicine. However, their influence on immune systems remains unclear.

MATERIALS AND METHODS

Two few-layered MSNs at sizes of 100-250 nm (S-MSNs) and 400-500 nm (L-MSNs) were used in this study. Bone marrow-derived dendritic cells (DCs) were exposed to both MSNs at different doses (0, 8, 16, 32, 64, 128 µg/mL) for 48 h and subjected to analyses of surface marker expression, cytokine secretion, lymphoid homing and in vivo T cell priming.

RESULTS

Different-sized MSNs of all doses did not affect the viability of DCs. The expression of CD40, CD80, CD86 and CCR7 was significantly higher on both S-MSN- and L-MSN-treated DCs at a dose of 128 μg/mL. As the dose of MSN increased, the secretion of IL-12p70 remained unchanged, the secretion of IL-1β decreased, and the production of TNF-α increased. A significant increase in IL-6 was observed in the 128 µg/mL L-MSN-treated DCs. In particular, MSN treatment dramatically improved the ex vivo movement and in vivo homing ability of both the local resident and blood circulating DCs. Furthermore, the cytoskeleton rearrangement regulated by ROS elevation was responsible for the enhanced homing ability of the MSNs. More robust CD4+ and CD8+ T cell proliferation and activation (characterized by high expression of CD107a, CD69 and ICOS) was observed in mice vaccinated with MSN-treated DCs. Importantly, exposure to MSNs did not interrupt LPS-induced DC activation, homing and T cell priming.

CONCLUSION

Few-layered MSNs ranging from 100 to 500 nm in size could play an immunostimulatory role in enhancing DC maturation, migration and T cell elicitation, making them a good candidate for vaccine adjuvants. Investigation of this study will not only expand the applications of MSNs and other new transition metal dichalcogenides (TMDCs) but also shed light on the in vivo immune-risk evaluation of MSN-based nanomaterials.

Two-Dimensional Transition Metal Dichalcogenides: Synthesis, Biomedical Applications and Biosafety Evaluation

Recently, two-dimensional transition metal dichalcogenides (2D TMDCs) have drawn certain attentions in many fields. The unique and diversified electronic structure and ultrathin sheet structure of 2D TMDCs offer opportunities for moving ahead of other 2D nanomaterials such as graphene and expanding the wide application of inorganic 2D nanomaterials in many fields. For a better understanding of 2D TMDCs, one needs to know methods for their synthesis and modification, as well as their potential applications and possible biological toxicity. Herein, we summarized the recent research progress of 2D TMDCs with particular focus on their biomedical applications and potential health risks. Firstly, two kinds of synthesis methods of 2D TMDCs, top-down and bottom-up, and methods for their surface functionalization are reviewed. Secondly, the applications of 2D TMDCs in the field of biomedicine, including drug loading, photothermal therapy, biological imaging and biosensor were summarized. After that, we presented the existing researches on biosafety evaluation of 2D TMDCs. At last, we discussed major research gap in current researches and challenges and coping strategies in future studies.

β-NaYF4:Yb,Er,Gd nanorods@1T/2H-MoS2 for 980 nm NIR-triggered photocatalytic bactericidal properties

Fabrication of β-NaYF₄:Yb,Er,Gd@1T/2H-MoS₂ nanocomposites for NIR-driven photocatalytic sterilization of Escherichia coli.

Biodegradable Hollow MoSe2/Fe3O4 Nanospheres as the Photodynamic Therapy-Enhanced Agent for Multimode CT/MR/IR Imaging and Synergistic Antitumor Therapy

Photodynamic therapy (PDT) is considered as one of the most effective cancer treatment strategies because of its minimally invasive and high efficiency. On account of the correlation between PDT and photocatalytic oxidation, the hollow MoSe₂/Fe₃O₄ (MF-2) nanoheterostructure was constructed to enhance PDT as shown in this paper. The size and the hollow structure can be well controlled by the addition of F-127. MoSe₂/Fe₃O₄ reveals the twofold reactive oxygen species (ROS) generation in contrast to the pure MoSe₂, which is ascribed to the effective separation of photogenic charges. The novel hollow structure also supplies a lot of cavities for perfluorocarbon (PFC) and O₂ loading, and O₂@PFC@MF-2 can effectively overcome the hypoxic microenvironment to further cause more than 3 times ROS production. Moreover, the narrow band gap and hollow structure also make sure that the strong near-infrared (NIR) light absorption and high photothermal conversion efficiency is as high as 66.2%. Furthermore, the combination of Fe₃O₄ can further accelerate the effective biodegradation capacity of MF-2 because of the repeated endogenous redox reaction to form water-soluble Mo^VI-oxide species. Meanwhile, doxorubicin (Dox, anticancer drug) was assembled onto the MF-2@PEG nanomaterials through π-π staking and electrostatic interaction for chemotherapy. O₂@PFC@MF-2@PEG/Dox possesses the potential application in triple-model computed tomography, magnetic resonance, and infrared (CT/MR/IR) imaging-guided photothermal/photodynamic/chemotherapy (PTT/PDT/chemotherapy) nanodiagnosis platforms.

Construction and evaluation of tumor nucleus-targeting nanocomposite for cancer dual-mode imaging - Guiding photodynamic therapy/photothermal therapy

To tackle the barrier of the insufficient intra-cellular delivery of reactive oxygen species (ROS) and heat, we designed a multifunctional nanoplatform to release ROS and heat directly in the cell nucleus for enhancing combined photodynamic therapy (PDT) and photothermal therapy (PTT) of tumors. As a photothermal agent, WS₂ nanoparticles were adsorbed photosensitive Au₂₅(Captopril)₁₈^- (Au₂₅) nanoclusters via electrostatic interaction. And Dexamethasone (Dex), a glucocorticoid with nucleus targeting capability, played a key role in the intra-nuclear process of heat and ROS. PTT can increase intra-tumoral blood flow to promote Au₂₅ produce more ROS for PDT. Under near infrared (NIR) laser irradiation at a single 808 nm, these nucleus targeting WS₂ nanoplatforms showed a significant decreased cell viability of 18.2 ± 1.7% and a high DNA damage degree of 59.6 ± 8.3%. Furthermore, the WS₂ nanoplatform could be further used for X-ray computed tomography (CT) images. Taken together, our study provided a new prospect for effectively diagnostic and enhancing PTT/PDT efficacy.

Multifunctional Photo- and Magnetoresponsive Graphene Oxide-Fe3O4 Nanocomposite-Alginate Hydrogel Platform for Ice Recrystallization Inhibition

Tuning ice recrystallization (IR) has attracted tremendous interest in fundamental research and a variety of practical applications, including food and pharmaceutical engineering, fabrication of anti-icing coating and porous materials, and cryopreservation of biological cells and tissues. Although great efforts have been devoted to modulation of IR for better microstructure control of various materials, it still remains a challenge, especially in cryopreservation, where insufficient suppression of IR during warming is fatal to the cells. Herein, we report an all-in-one platform, combining the external physical fields and the functional materials for both active and passive suppression of IR, where the photo- and magnetothermal dual-modal heating of GO-Fe₃O₄ nanocomposites (NCs) can be used to suppress IR with both enhanced global warming and microscale thermal disturbance. Moreover, the materials alginate hydrogels and GO-Fe₃O₄ NCs can act as IR inhibitors for further suppression of the IR effect. As a typical application, we show that this GO-Fe₃O₄ nanocomposite-alginate hydrogel platform can successfully enable low-cryoprotectant, high-quality vitrification of stem cell-laden hydrogels. We believe that the versatile ice recrystallization inhibition platform will have a profound influence on cryopreservation and tremendously facilitate stem cell-based medicine to meet its ever-increasing demand in clinical settings.

Current and future envision on developing biosensors aided by 2D molybdenum disulfide (MoS2) productions

Two-dimensional (2D) layered nanomaterials have triggered an intensive interest due to the fascinating physiochemical properties with the exceptional physical, optical and electrical characteristics that transpired from the quantum size effect of their ultra-thin structure. Among the family of 2D nanomaterials, molybdenum disulfide (MoS₂) features distinct characteristics related to the existence of direct energy bandgap, which significantly lowers the leakage current and surpasses other 2D materials. In this overview, we expatiate the novel strategies to synthesize MoS₂ that cover techniques such as liquid exfoliation, chemical vapour deposition, mechanical exfoliation, hydrothermal reaction, and Van Der Waal epitaxial growth on the substrate. We extend the discussion on the recent progress in biosensing applications of the produced MoS₂, highlighting the important surface-to-volume of ultrathin MoS₂ structure, which enhances the overall performance of the devices. Further, envisioned the missing piece with the current MoS₂-based biosensors towards developing the future strategies.

Remote Induction of Cell Autophagy by 2D MoS2 Nanosheets via Perturbing Cell Surface Receptors and mTOR Pathway from Outside of Cells

The ability of nanoparticles to induce adverse consequences in human cells relies on their physical shapes. In this aspect, how two-dimensional nanoparticles differ from three-dimensional nanoparticles is not well-known. To elucidate this difference, combined experimental and theoretical approaches are employed to compare MoS₂ nanosheets with 5-layer and 40-layer thicknesses for their cellular effects and the associated molecular events. At a concentration as defined by the nanosheet surface areas (10 cm²/mL), 40-layer nanosheets are internalized by cells, whereas 5-layer nanosheets mostly bind to the cell surface without internalization. Although they alter different autophagy-related genes, a common mechanism is that they both perturb cell surface protein amyloid precursor proteins and activate the mTOR signaling pathway. Our findings prove that the perturbation of cellular function without nanoparticle internalization has significant nanomedicinal and nanotoxicological significances.

2D MoS2 -Based Nanomaterials for Therapeutic, Bioimaging, and Biosensing Applications

Molybdenum disulfide (MoS₂ ), a typical layered 2D transition metal dichalcogenide, has received colossal interest in the past few years due to its unique structural, physicochemical, optical, and biological properties. While MoS₂ is mostly applied in traditional industries such as dry lubricants, intercalation agents, and negative electrode material in lithium-ion batteries, its 2D and 0D forms have led to diverse applications in sensing, catalysis, therapy, and imaging. Herein, a systematic overview of the progress that is made in the field of MoS₂ research with an emphasis on its different biomedical applications is presented. This article provides a general discussion on the basic structure and property of MoS₂ and gives a detailed description of its different morphologies that are synthesized so far, namely, nanosheets, nanotubes, and quantum dots along with synthesis strategies. The biomedical applications of MoS₂ -based nanocomposites are also described in detail and categorically, such as in varied therapeutic and diagnostic modalities like drug delivery, gene delivery, phototherapy, combined therapy, bioimaging, theranostics, and biosensing. Finally, a brief commentary on the current challenges and limitations being faced is provided, along with a discussion of some future perspectives for the overall improvement of MoS₂ -based nanocomposites as a potential nanomedicine.

Heterogeneous growth of palladium nanocrystals on upconversion nanoparticles for multimodal imaging and photothermal therapy

Based on the heterogeneous growth of nano-palladium on UCNPs, a new kind of nanocomposite was developed that can be used for dual-imaging guided photothermal therapy. This smart strategy provides new insights for future development of materials based on the multicomponent nanocomposites.

Photothermally controlled drug release system with high dose loading for synergistic chemo-photothermal therapy of multidrug resistance cancer

Chemotherapy is an important first-line strategy for tumor therapy in cancer treatment, but multidrug resistance (MDR) is a major problem that reduces the efficacy of chemotherapeutics. Herein, we report a novel photothermally controlled intelligent drug release system (AuNP@mSiO₂-DOX-FA) with a large amount of drugs loading for synergistic chemo-photothermal therapy of MDR in breast cancer. The nanoplatform utilized gold nanoparticles as a hyperthermia core, and large-mesoporous silica as a shell for doxorubicin (DOX) loading. Benefiting from the thick layer and large pore size, the encapsulation and loading efficiency were as high as 97.7% and 8.84%, respectively. Furthermore, under the trigger of 808 nm near infrared (NIR) light, the released DOX increased significantly at pH 5.0 and reached to 39.0% in 20 min, achieving a facile intelligent control of chemotherapy additional to the photothermal therapy. The viability of MCF-7/ADR cells could be efficiently reduced to 16.9%, demonstrating the proposed photothermally controlled system with synergistic chemo-photothermal therapy has great potential capability to overcome MDR in breast cancer.

Recent advances in the field of transition metal dichalcogenides for biomedical applications

Nanosheets of transition metal dichalcogenide (TMDs), the graphene-like two-dimensional (2D) materials, exhibit a unique combination of properties and have attracted enormous research interest for a wide range of applications including catalysis, functional electronics, solid lubrication, photovoltaics, energy materials and most recently in biomedical applications. Their potential for use in biosensors, drug delivery, multimodal imaging, antimicrobial agents and tissue engineering is being actively studied. However, the commercial translation of exfoliated TMDs has been limited due to the low aqueous solubility, non-uniformity, lack of control over the layer thickness, and the long-term colloidal stability of the exfoliated material. There is wide interest in the synthesis and exfoliation of TMDs resulting in the reporting of increasing numbers of new methods and their biomedical applications. The unique physicochemical characteristics of the TMD nanosheets have been exploited to tether them with biological payload to achieve selective localized delivery in vivo. The large surface-to-volume ratio, good cytocompatibility, ease of surface modification, tunable bandgap, strong spin-orbit coupling, and high optical and thermal conversion efficiency of TMD nanosheets make them favorable over traditional nanomaterials for biomedical research. Moreover, the presence of abundant active edge sites on the 2D TMDs makes them suitable for catalytic activities, while the large surface area and the interspace between layers are particularly conducive to ion or small molecule intercalation, making them useful for energy storage applications with rapid redox reaction capabilities. One of the major limitations of the exfoliated TMDs has been their limited colloidal stability in aqueous media. In this review, we summarize the recent advances in the exfoliation and synthesis of single-layered TMDs, their biomedical efficacy in terms of cytotoxicity, combinatorial therapy and diagnostic imaging, as well as antimicrobial activity. We highlight the current challenges in the field and propose strategies for the future.

Multivalent Interactions between 2D Nanomaterials and Biointerfaces

2D nanomaterials, particularly graphene, offer many fascinating physicochemical properties that have generated exciting visions of future biological applications. In order to capitalize on the potential of 2D nanomaterials in this field, a full understanding of their interactions with biointerfaces is crucial. The uptake pathways, toxicity, long-term fate of 2D nanomaterials in biological systems, and their interactions with the living systems are fundamental questions that must be understood. Here, the latest progress is summarized, with a focus on pathogen, mammalian cell, and tissue interactions. The cellular uptake pathways of graphene derivatives will be discussed, along with health risks, and interactions with membranes-including bacteria and viruses-and the role of chemical structure and modifications. Other novel 2D nanomaterials with potential biomedical applications, such as transition-metal dichalcogenides, transition-metal oxide, and black phosphorus will be discussed at the end of this review.

Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives

Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS₂, MoSe₂, MoTe₂, WS₂ and WSe₂, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.

Advanced smart-photosensitizers for more effective cancer treatment

Photodynamic therapy (PDT) based upon the use of light and photosensitizers (PSs) has been used as a novel treatment approach for a variety of tumors. It, however, has several major limitations in the clinic: poor water solubility, long-term phototoxicity, low tumor targeting efficacy, and limited light penetration. With advances in nanotechnology, materials science, and clinical interventional imaging procedures, various smart-PSs have been developed for improving their cancer-therapeutic efficacy while reducing the adverse effects. Here, we briefly review state-of-the-art smart-PSs and discuss the future directions of PDT technology.

RGD-QD-MoS2 nanosheets for targeted fluorescent imaging and photothermal therapy of cancer

The fast-developing field of nanotechnology provides unprecedented opportunities for the increasing demands of biomedicine, especially for cancer diagnostics and treatment. Here, novel multifunctional zero-dimensional-two-dimensional (0D-2D) RGD-QD-MoS₂ nanosheets (NSs) with excellent fluorescence, photothermal conversion, and cancer-targeting properties were successfully prepared by functionalizing single-layer MoS₂ NSs with fluorescent quantum dots (QDs) and arginine-glycine-aspartic (RGD) containing peptides. By using RGD-QD-MoS₂ NSs as a multifunctional theranostic agent, targeted fluorescent imaging and photothermal therapy (PTT) of human cervical carcinoma (HeLa) cells were achieved. Moreover, HeLa tumors in mouse models can be fluorescently imaged and completely eradicated by photothermal irradiation using a low power NIR laser, due to the effective accumulation of RGD-QD-MoS₂ NSs at the tumor sites through the RGD-integrin targeting and the enhanced penetration and retention (EPR) effect. Without exhibiting any appreciable toxicity to treated cells or animals, RGD-QD-MoS₂ NSs have been demonstrated as promising multifunctional theranostic agents for cancer imaging and therapy.

Synthesis and Optimization of MoS2@Fe3O4-ICG/Pt(IV) Nanoflowers for MR/IR/PA Bioimaging and Combined PTT/PDT/Chemotherapy Triggered by 808 nm Laser

Elaborately designed biocompatible nanoplatforms simultaneously achieving multimodal bioimaging and therapeutic functions are highly desirable for modern biomedical applications. Herein, uniform MoS2 nanoflowers with a broad size range of 80-180 nm have been synthesized through a facile, controllable, and scalable hydrothermal method. The strong absorbance of MoS2 nanoflowers at 808 nm imparts them with high efficiency and stability of photothermal conversion. Then a novel multifunctional composite of MoS2@Fe3O4-ICG/Pt(IV) (labeled as Mo@Fe-ICG/Pt) is designed by covalently grafting Fe3O4 nanoparticles with polyethylenimine (PEI) functionalized MoS2, and then loading indocyanine green molecules (ICG, photosensitizers) and platinum (IV) prodrugs (labeled as Pt(IV) prodrugs) on the surface of MoS2@Fe3O4. The resulting Mo@Fe-ICG/Pt nanocomposites can achieve excellent magnetic resonance/infrared thermal/photoacoustic trimodal biomaging as well as remarkably enhanced antitumor efficacy of combined photothermal therapy, photodynamic therapy, and chemotherapy triggered by a single 808 nm NIR laser, thus leading to an ideal nanoplatform for cancer diagnosis and treatment in future.

Marriage of Albumin-Gadolinium Complexes and MoS2 Nanoflakes as Cancer Theranostics for Dual-Modality Magnetic Resonance/Photoacoustic Imaging and Photothermal Therapy

The construction of safe and stable theranostics is beneficial to realize simultaneous cancer diagnosis and treatment. In this study, bovine serum albumin-gadolinium (BSA-Gd) complexes and MoS₂ nanoflakes (MoS₂-Gd-BSA) were successfully married as cancer theranostics for dual-modality magnetic resonance (MR)/photoacoustic (PA) imaging and photothermal therapy (PTT). BSA-Gd complexes were prepared by the biomineralization method and then conjugated with MoS₂ nanoflakes via an amide bond. The as-prepared MoS₂-Gd-BSA possessed a good photostability and photothermal effect. The cytotoxicity assessment and hemolysis assay suggested the excellent biocompatibility of MoS₂-Gd-BSA. Meanwhile, MoS₂-Gd-BSA could not only achieve in vivo MR/PA dual-modality imaging of xenograft tumors, but also effectively kill cancer cells in vitro and ablate the xenograft tumors in vivo upon 808 nm laser illumination. The biodistribution and histological evaluations indicated the negligible toxicity of MoS₂-Gd-BSA both in vitro and in vivo. Thus, our results substantiated the potential of MoS₂-Gd-BSA for cancer theranostics.