Nanostructures for NIR light-controlled therapies

Thermo-responsive gold nanorod vesicles for combined NIR-II photothermal therapy and chemotherapy of solid tumors

Photothermal therapy (PTT) is a promising treatment strategy for malignant tumors. Photothermal agents which can achieve efficient photothermal conversion in the NIR-II region plays crucial roles in this remedy. Here, we report one type of thermo-responsive gold nanorod vesicles USGRV-17-AAG for combined NIR-II photothermal therapy and chemotherapy of solid tumors. The nanovesicles are formed by self-assembly of gold nanorods modified with amphiphilic polymers (PEG45-b-PS450) and UCST-type polymers (P(AAm-co-AN)), and are loaded with the heat shock protein inhibitor 17-AAG. Upon 1064 nm laser irradiation, USGRV-17-AAG exhibits a high photothermal conversion efficiency (65.1 %) and thus can achieve temperature responsive release of tanespimycin (17-AAG), an inhibitor of HSP90. The combination of NIR-II photothermal therapy and chemotherapy can effectively eliminate tumor cells and inhibit the expression of HSP90. Intravenous injection of USGRV-17-AAG followed by 1064 nm laser irradiation revealed efficacious tumor ablation of tumor-bearing mice, with a tumor growth inhibition rate of 98.86 %. Therefore, USGRV-17-AAG can produce efficient anti-tumor effects and provides an alternative approach to the treatment of malignant tumors. STATEMENT OF SIGNIFICANCE: Photothermal conversion agents (PTAs) based on the near-infrared II (NIR-II) window are currently attracting significant attention for their promising development and diverse applications. In this study, thermosensitive drug-loaded nanovesicles, USGRV-17-AAG, were designed to enable NIR-II photothermal therapy in combination with chemotherapy. These nanovesicles were loaded with the heat shock protein 90 (HSP90) inhibitor 17-AAG, which effectively inhibits HSP90 expression and enhances the therapeutic efficacy of photothermal treatment. Additionally, USGRV-17-AAG exhibited efficient photothermal conversion (65.1 %) under 1064 nm laser irradiation and enabled temperature-responsive drug release through the action of surface-modified upper critical solution temperature (UCST) polymers. This nanocarrier, with enhanced NIR-II photothermal therapy, might offer a promising solution for anti-tumor treatment.

Grafting and controlled release of antimicrobial peptides from mesoporous silica

The grafting of antimicrobial peptides onto mesoporous silica particles and their controlled release using a green light-responsive linker, which enables tunable release-concentration-time profiles, is presented. The mesoporous silica surface is functionalized with antimicrobial peptides employing sequential functionalization steps, including the grafting of 3-[(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) as anchor, boron-dipyrromethene (BODIPY) as photosensitive linker, and C14R peptides as antimicrobial agents. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflectance infrared (ATR-IR) spectroscopy, and thermogravimetric analysis (TGA) validate the successful fabrication and functionalization of mesoporous silica. The ester-1,2,3-triazole-BODIPY demonstrates high sensitivity to green light and enables C14R antimicrobial peptide release with adjusted concentration-time profiles. Under the applied conditions up to 64 μg mL-1 were released within 40 minutes. The antimicrobial activity of the released C14R on Escherichia coli. BL21(DE3) is demonstrated. Overall, the use of the photosensitive linker not only provides a promising avenue for controlling the release of biomolecules and therapeutics but also opens up opportunities for the development of materials for targeted release in wound dressings, for example.

Inhalable Polymeric Microparticles for Phage and Photothermal Synergistic Therapy of Methicillin-Resistant Staphylococcus aureus Pneumonia

Acute methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is a common and serious lung infection with high morbidity and mortality rates. Due to the increasing antibiotic resistance, toxicity, and pathogenicity of MRSA, there is an urgent need to explore effective antibacterial strategies. In this study, we developed a dry powder inhalable formulation which is composed of porous microspheres prepared from poly(lactic-co-glycolic acid) (PLGA), internally loaded with indocyanine green (ICG)-modified, heat-resistant phages that we screened for their high efficacy against MRSA. This formulation can deliver therapeutic doses of ICG-modified active phages to the deep lung tissue infection sites, avoiding rapid clearance by alveolar macrophages. Combined with the synergistic treatment of phage therapy and photothermal therapy, the formulation demonstrates potent bactericidal effects in acute MRSA pneumonia. With its long-term stability at room temperature and inhalable characteristics, this formulation has the potential to be a promising drug for the clinical treatment of MRSA pneumonia.

Detection of free DNA based on metal-enhanced fluorescence triggered by CRISPR-Cas12a and colorimetric analysis

The CRISPR-Cas system has been found to be extremely sensitive and there is an urgent demand to extend its potential in bioassays. Herein, we developed a novel nanobiosensor to detect the human papillomavirus 16 genes (HPV-16 DNA), which is triggered by CRISPR-Cas12a to amplify the fluorescence signal by metal-enhanced fluorescence (CAMEF). Along with the changing of the fluorescence signal, the aggregation of the substrate of MEF also leads to a change in the color of the mixture solution, enabling dual signal detection with the fluorescence and the naked eye. Furthermore, the designed CAMEF probe was verified to detect the HPV-16 DNA accurately and reliably in biological samples. Triggered by the CRISPR system, the designed CAMEF probe allows quantitative detection of the HPV-16 DNA in the wide range of 10-500 pM. Owing to the MEF, the fluorescence signal of the CAMEF probe was significantly amplified with the detection limit as low as 1 pM. Besides, we can determine the concentration of HPV-16 DNA simply by the naked eye, which also drastically reduces the possibility of false-positive signals. Theoretically, the target ssDNA could be any strand of DNA obtained by designing the crRNA sequence in the CRISPR-Cas system. We believe that the designed CAMEF sensor can present a reliable approach for the accurate detection of low amounts of target ssDNA in complex biological samples.

Near-infrared-guided NO generator for combined NO/photothermal/chemodynamic therapy of bacterial infections

Nitric oxide (NO)-based gas therapy approaches are promising in the treatment of infections; however, these strategies are hindered by poor delivery to the target site, which leads to unsatisfactory effects. In this study, we developed a NO-controlled platform (SCM@HA) via NO-generating mesoporous silica nanoparticles co-doped with sodium nitroprusside and copper sulphide to control NO production under near-infrared (NIR)-laser irradiation. Irradiation with an 808 nm NIR laser rapidly triggered the release of NO from the particles to actualise gas therapy. Photothermal therapy (PTT) also increased the local microenvironment temperature, and the close relationship between chemodynamic therapy (CDT) and temperature suggests that the increasing temperature facilitates in its working. The hydroxyl radicals generated by CDT can destroy the structure of bacteria in acidic environments. The germicidal activity of the nanoparticles was determined by the combined action of PTT, CDT, and NO-based gas therapy. The nanoparticles showed bactericidal activity in vitro against bacterial strains Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhimurium). Finally, the anti-infective efficacy in vivo in S. aureus-infected mouse model was demonstrated. Thus, the synergistic antimicrobial effects of NO-generating silica nanoparticles have good potential for the non-antibiotic treatment of bacterial infections in wounds. STATEMENT OF SIGNIFICANCE: Bacterial infections and resistance are challenging health threats. Therefore, the development of an antibiotic-independent method is essential for the treatment of wound bacterial infections. In this study, NO-generating nanoparticles loaded with sodium nitroprusside in copper sulphide-doped mesoporous silica were prepared to control the long-term release of NO using near-infrared laser, which has good efficacy of PTT and CDT. The bactericidal effects of as-prepared nanoparticles against S. aureus and S. typhimurium have been well elucidated. This study proposes a feasible method in the field of NO-based therapy, thus paving the way that will benefit for the treatment of bacterial infections in wounds.

Antibacterial micro/nanomotors: advancing biofilm research to support medical applications

Multi-drug resistant (MDR) bacterial infections are gradually increasing in the global scope, causing a serious burden to patients and society. The formation of bacterial biofilms, which is one of the key reasons for antibiotic resistance, blocks antibiotic penetration by forming a physical barrier. Nano/micro motors (MNMs) are micro-/nanoscale devices capable of performing complex tasks in the bacterial microenvironment by transforming various energy sources (including chemical fuels or external physical fields) into mechanical motion or actuation. This autonomous movement provides significant advantages in breaking through biological barriers and accelerating drug diffusion. In recent years, MNMs with high penetrating power have been used as carriers of antibiotics to overcome bacterial biofilms, enabling efficient drug delivery and improving the therapeutic effectiveness of MDR bacterial infections. Additionally, non-antibiotic antibacterial strategies based on nanomaterials, such as photothermal therapy and photodynamic therapy, are continuously being developed due to their non-invasive nature, high effectiveness, and non-induction of resistance. Therefore, multifunctional MNMs have broad prospects in the treatment of MDR bacterial infections. This review discusses the performance of MNMs in the breakthrough and elimination of bacterial biofilms, as well as their application in the field of anti-infection. Finally, the challenges and future development directions of antibacterial MNMs are introduced.

Stimuli-responsive (nano)architectures for phytochemical delivery in cancer therapy

The use of phytochemicals for purpose of cancer therapy has been accelerated due to resistance of tumor cells to conventional chemotherapy drugs and therefore, monotherapy does not cause significant improvement in the prognosis and survival of patients. Therefore, administration of natural products alone or in combination with chemotherapy drugs due to various mechanisms of action has been suggested. However, cancer therapy using phytochemicals requires more attention because of poor bioavailability of compounds and lack of specific accumulation at tumor site. Hence, nanocarriers for specific delivery of phytochemicals in tumor therapy has been suggested. The pharmacokinetic profile of natural products and their therapeutic indices can be improved. The nanocarriers can improve potential of natural products in crossing over BBB and also, promote internalization in cancer cells through endocytosis. Moreover, (nano)platforms can deliver both natural and synthetic anti-cancer drugs in combination cancer therapy. The surface functionalization of nanostructures with ligands improves ability in internalization in tumor cells and improving cytotoxicity of natural compounds. Interestingly, stimuli-responsive nanostructures that respond to endogenous and exogenous stimuli have been employed for delivery of natural compounds in cancer therapy. The decrease in pH in tumor microenvironment causes degradation of bonds in nanostructures to release cargo and when changes in GSH levels occur, it also mediates drug release from nanocarriers. Moreover, enzymes in the tumor microenvironment such as MMP-2 can mediate drug release from nanocarriers and more progresses in targeted drug delivery obtained by application of nanoparticles that are responsive to exogenous stimulus including light.

A NIR-Activated and Mild-Temperature-Sensitive Nanoplatform with an HSP90 Inhibitor for Combinatory Chemotherapy and Mild Photothermal Therapy in Cancel Cells

Mild photothermal therapy (PTT) shows great potential to treat cancers while avoiding unwanted damage to surrounding normal cells. However, the efficacy of mild PTT is normally moderate because of the low hyperthermia temperature and limited light penetration depth. Chemotherapy has unlimited penetration but often suffers from unsatisfactory efficacy in view of the occurrence of drug resistance, suboptimal drug delivery and release profile. As a result, the combinatory of chemotherapy and mild PTT would integrate their advantages and overcome the shortcomings. Herein, we synthesized an NIR-activatable and mild-temperature-sensitive nanoplatform (BDPII-gel@TSL) composed of temperature-sensitive liposomes (TSL), heat shock protein 90 (HSP90) inhibitor (geldanamycin) and photothermal agent (BDPII), for dual chemotherapy and mild PTT in cancer cells. BDPII, constructed with donor-acceptor moieties, acts as an excellent near-infrared (NIR) photothermal agent (PTA) with a high photothermal conversion efficiency (80.75%). BDPII-containing TSLs efficiently produce a mild hyperthermia effect (42 °C) under laser irradiation (808 nm, 0.5 W cm-2). Importantly, the phase transformation of TSL leads to burst release of geldanamycin from BDPII-gel@TSL, and this contributes to down-regulation of the overexpression of HSP90, ensuring efficient inhibition of cancer cell growth. This research provides a dual-sensitive synergistic therapeutic strategy for cancer cell treatment.

Nanobiotics and the One Health Approach: Boosting the Fight against Antimicrobial Resistance at the Nanoscale

Antimicrobial resistance (AMR) is a growing public health concern worldwide, and it poses a significant threat to human, animal, and environmental health. The overuse and misuse of antibiotics have contributed significantly and others factors including gene mutation, bacteria living in biofilms, and enzymatic degradation/hydrolyses help in the emergence and spread of AMR, which may lead to significant economic consequences such as reduced productivity and increased health care costs. Nanotechnology offers a promising platform for addressing this challenge. Nanoparticles have unique properties that make them highly effective in combating bacterial infections by inhibiting the growth and survival of multi-drug-resistant bacteria in three areas of health: human, animal, and environmental. To conduct an economic evaluation of surveillance in this context, it is crucial to obtain an understanding of the connections to be addressed by several nations by implementing national action policies based on the One Health strategy. This review provides an overview of the progress made thus far and presents potential future directions to optimize the impact of nanobiotics on AMR.

Copper-based nanoparticles against microbial infections

Drug-resistant bacteria and highly infectious viruses are among the major global threats affecting the human health. There is an immediate need for novel strategies to tackle this challenge. Copper-based nanoparticles (CBNPs) have exhibited a broad antimicrobial capacity and are receiving increasing attention in this context. In this review, we describe the functionalization of CBNPs, elucidate their antibacterial and antiviral activity as well as applications, and briefly review their toxicity, biodistribution, and persistence. The limitations of the current study and potential solutions are also shortly discussed. The review will guide the rational design of functional nanomaterials for antimicrobial application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Recent advances in 2D material-based phototherapy

Phototherapy, which generally refers to photothermal therapy (PTT) and photodynamic therapy (PDT), has received significant attention over the past few years since it is non-invasive, has effective selectivity, and has few side effects. As a result, it has become a promising alternative to traditional clinical treatments. At present, two-dimensional materials (2D materials) have proven to be at the forefront of the development of advanced nanomaterials due to their ultrathin structures and fascinating optical properties. As a result, much work has been put into developing phototherapy platforms based on 2D materials. This review summarizes the current developments in 2D materials beyond graphene for phototherapy, focusing on the novel approaches of PTT and PDT. New methods are being developed to go above and beyond conventional treatment to fully use the potential of 2D materials. Additionally, the efficacy of cutting-edge phototherapy is assessed, and the existing difficulties and future prospects of 2D materials for phototherapy are covered.

Precise Photothermal Treatment of Methicillin-Resistant S. aureus Infection via Phage Lysin-Cell Binding Domain-Modified Gold Nanosheets

The increasing spread of antibiotic resistance in bacterial pathogens poses a huge threat to global human health. Precise targeting of bacterial pathogens while avoiding collateral damage to healthy tissues has become the overriding goal for bacterial infection treatment. Inspired by the host specificity of bacteriophages, a biomimetic intelligent platform was designed for highly precise photothermal treatment herein. As proof-of-concept, the lysin cell-binding domain (CBD) from a newly discovered virulent methicillin-resistant S. aureus (MRSA) phage Z was applied to the functionalization of gold nanosheets. Our results demonstrated that the bionanocomposite gold particles (Au@PEG-CBDz) could be effectively delivered directly to MRSA and kill them effectively under near infrared irradiation in vitro, while displaying good in vivo biocompatibility. This work is the first to report the combination of phage lysin navigatory function with photothermal effect-induced bactericidal activity from Au nanosheets, providing a novel therapeutic mode for the precision treatment of antibiotic-resistant bacterial infections.

The Influence of Medium on Fluorescence Quenching of Colloidal Solutions of the Nd3+: LaF3 Nanoparticles Prepared with HTMW Treatment

An original method was proposed to reduce the quenching of the NIR fluorescence of colloidal solutions of 0.1 at. % Nd³⁺: LaF₃ nanoparticles (NPs) synthesized by aqueous co-precipitation method followed by hydrothermal microwave treatment. For this, an aqueous colloidal solution of NPs was precipitated by centrifugation and dissolved in the same volume of DMSO. The kinetics of static fluorescence quenching of Nd³⁺ donors of doped NPs dispersed in two solvents was analyzed to determine and to compare the concentrations of OH- quenching acceptors uniformly distributed throughout the volume of the NPs. The dependences of the relative fluorescence quantum yield φ of colloidal solutions on the concentration of OH- groups in the NPs were calculated and were also used to determine concentration of acceptors in the volume of NPs in different solvents. It was found that the concentration of OH- groups in NPs dispersed in DMSO is almost two times lower than in NPs dispersed in water. This gives an almost two-fold increase in the relative fluorescence quantum yield φ for the former. The sizes of synthesized NPs were monitored by common TEM and by applying a rapid procedure based on optical visualization of the trajectories of the Brownian motion of NPs in solution using a laser ultramicroscope. The use of two different methods made it possible to obtain more detailed information about the studied NPs.

Photothermal conversion and transfer in photothermal therapy: From macroscale to nanoscale

Photothermal therapy (PTT) is a promising alternative therapy for benign or even malignant tumors. To improve the selective heating of tumor cells, target-specific photothermal conversion agents are often included, especially nanoparticles. Meanwhile, some indirect methods by manipulating the radiation and heat delivery are also adopted. Therefore, to gain a clear understanding of the mechanism, and to improve the controllability of PTT, a few issues need to be clarified, including bioheat and radiation transfer, localized and collective heating of nanoparticles, etc. In this review, we provide an introduction to the typical bioheat transfer and radiation transfer models along with the dynamic thermophysical properties of biological tissue. On this basis, we reviewed the most recent advances in the temperature control methods in PTT from macroscale to nanoscale. Most importantly, a comprehensive introduction of the localized and collective heating effects of nanoparticle clusters is provided to give a clear insight into the mechanism for PPT from the microscale and nanoscale point of view.

A hybrid thermoresponsive plasmonic nanogel designed for NIR-mediated chemotherapy

Temperature-trigger chemotherapy is one of the state-of-the-art anti-tumoral strategies in nanomedicine. However, this strategy is in close relationship with the effect of the temperature in the tumor tissue. With high temperatures, the ablation of the tumor tissue can hinder a correct chemotherapy approximation. On the other hand, with moderate temperatures a negative vascularization that promotes the tumor growing is produced and competes with the chemotherapeutic effects. We have constructed one nanogel system composed of a thermoresponsive polymer cross-linked by plasmonic gold nanoparticles (AuNPs) for temperature-trigger chemotherapy. Doxorubicin loaded in the porous interior of the nanogel is released when the thermoresponsive network of the nanogel collapses due to the heat generated by the AuNPs upon near infra-red light irradiation. The hybrid nanogel system has been tested in vitro and in vivo, where it was observed that the temperatures reached in the in vivo NIR irradiation have an undesired effect on the inhibition of the tumor growth while the drug loaded systems considerably reduced the tumor sizes. This study shows the importance of design in temperature triggered antitumoral systems, where lower temperatures usually reached in practical situations due to light attenuation produced by the tissue can be positively utilized for enhancing the antitumoral effect of loaded drugs in the system.

Molecular Switches—Tools for Imparting Control in Drug Delivery Systems

Cancer is a globally prevalent cause of premature mortality. Of growing interest is the development of novel anticancer therapies and the optimisation of associated risks. Major issues presently facing conventional anticancer therapies include systemic toxicity, poor solubility, membrane permeability, and multidrug resistance Nanocarriers have been employed to address these issues. Nanocarriers encapsulate anticancer drugs, enabling them to bypass biological barriers and minimise their adverse side effects. These drug delivery systems offer extensive benefits as they can be modified to gravitate towards specific environmental conditions. To further enhance the safety and efficacy of these drug carriers, modern developments have included incorporating a molecular switching mechanism into their structure. These molecular switches are responsive to endogenous and exogenous stimuli and may undergo reversible and repeatable conformational changes when activated. The incorporation of molecular switches can, therefore, impart stimuli-responsive drug-release control on a DDS. These stimuli can then be manipulated to offer precise dosage control over the drug release at a specific target site. This review discusses recent developments in the design of DDSs incorporating light and pH-responsive molecular switches as drug release controllers.

Polymeric Micro/Nanocarriers and Motors for Cargo Transport and Phototriggered Delivery

Smart polymer-based micro/nanoassemblies have emerged as a promising alternative for transporting and delivering a myriad of cargo. Cargo encapsulation into (or linked to) polymeric micro/nanocarrier (PC) strategies may help to conserve cargo activity and functionality when interacting with its surroundings in its journey to the target. PCs for cargo phototriggering allow for excellent spatiotemporal control via irradiation as an external stimulus, thus regulating the delivery kinetics of cargo and potentially increasing its therapeutic effect. Micromotors based on PCs offer an accelerated cargo-medium interaction for biomedical, environmental, and many other applications. This review collects the recent achievements in PC development based on nanomicelles, nanospheres, and nanopolymersomes, among others, with enhanced properties to increase cargo protection and cargo release efficiency triggered by ultraviolet (UV) and near-infrared (NIR) irradiation, including light-stimulated polymeric micromotors for propulsion, cargo transport, biosensing, and photo-thermal therapy. We emphasize the challenges of positioning PCs as drug delivery systems, as well as the outstanding opportunities of light-stimulated polymeric micromotors for practical applications.

Stable Aqueous Colloidal Solutions of Nd3+: LaF3 Nanoparticles, Promising for Luminescent Bioimaging in the Near-Infrared Spectral Range

Two series of stable aqueous colloidal solutions of Nd³⁺: LaF₃ single-phase well-crystallized nanoparticles (NPs), possessing a fluorcerite structure with different activator concentrations in each series, were synthesized. A hydrothermal method involving microwave-assisted heating (HTMW) in two Berghof speedwave devices equipped with one magnetron (type I) or two magnetrons (type II) was used. The average sizes of NPs are 15.4 ± 6 nm (type I) and 21 ± 7 nm (type II). Both types of NPs have a size distribution that is well described by a double Gaussian function. The fluorescence kinetics of the ⁴F_3/2 level of the Nd³⁺ ion for NPs of both types, in contrast to a similar bulk crystal, demonstrates a luminescence quenching associated not only with Nd-Nd self-quenching, but also with an additional Nd-OH quenching. A method has been developed for determining the spontaneous radiative lifetime of the excited state of a dopant ion, with the significant contribution of the luminescence quenching caused by the presence of the impurity OH- acceptors located in the bulk of NPs. The relative quantum yield of fluorescence and the fluorescence brightness of an aqueous colloidal solution of type II NPs with an optimal concentration of Nd³⁺ are only 2.5 times lower than those of analogous Nd³⁺: LaF₃ single crystals.

Recent advances in selective photothermal therapy of tumor

Photothermal therapy (PTT), which converts light energy to heat energy, has become a new research hotspot in cancer treatment. Although researchers have investigated various ways to improve the efficiency of tumor heat ablation to treat cancer, PTT may cause severe damage to normal tissue due to the systemic distribution of photothermal agents (PTAs) in the body and inaccurate laser exposure during treatment. To further improve the survival rate of cancer patients and reduce possible side effects on other parts of the body, it is still necessary to explore PTAs with high selectivity and precise treatment. In this review, we summarized strategies to improve the treatment selectivity of PTT, such as increasing the accumulation of PTAs at tumor sites and endowing PTAs with a self-regulating photothermal conversion function. The views and challenges of selective PTT were discussed, especially the prospects and challenges of their clinical applications.

Light-Controlled Precise Delivery of NIR-Responsive Semiconducting Polymer Nanoparticles with Promoted Vascular Permeability

The endothelial barrier plays an essential role in health and disease by protecting organs from toxins while allowing nutrients to access the circulation. However, it is the major obstacle that limits the delivery of therapeutic drugs to the diseased tissue. Here, it is reported for the first time that near-infrared (NIR) laser pulses can transiently promote the delivery of semiconducting polymer nanoparticles passing the vascular barrier via photoacoustic-effect-induced accumulation, only by the aid of pulse laser irradiation. This strategy enables selective and substantial accumulation of the NIR-absorbing nanoparticles inside specific tissues, implying the discovery of an unprecedented approach for light-controlled nanoparticle delivery. Especially, the nanoparticle delivery in solid tumors by 10-min laser scanning is approximately six times higher than that of the enhanced permeability and retention (EPR) effect in 24 h under current experimental conditions. Further results confirm that this strategy facilitates substantial accumulation of nanoparticles in the mouse brain with intact skull. This approach thus opens a new door for tissue-specific delivery of nanomaterials with an unprecedented level of efficiency and precision.

Synergistic Lysozyme-Photodynamic Therapy Against Resistant Bacteria based on an Intelligent Upconversion Nanoplatform

The rapid emergence of drug-resistant bacteria has raised a great social concern together with the impetus for exploring advanced antibacterial ways. NIR-triggered antimicrobial photodynamic therapy (PDT) by lanthanide-doped upconversion nanoparticles (UCNP) as energy donor exhibits the advantages of high tissue penetration, broad antibacterial spectrum and less acquired resistance, but is still limited by its low efficacy. Now we designed a bio-inorganic nanohybrid and combined lysozyme (LYZ) with UCNP-PDT system to enhance the efficiency against resistant bacteria. Benefiting from the rapid adhesion to bacteria, intelligently bacteria-responsive LYZ release and synergistic LYZ-PDT effect, the nanoplatform achieves an exceptionally strong bactericidal capacity and conspicuous bacteriostasis on methicillin-resistant S. aureus. These findings pave the way for designing efficiently antibacterial nanomaterials and provide a new strategy for combating deep-tissue bacterial infection.

Advances in Biomimetic Nanoparticles for Targeted Cancer Therapy and Diagnosis

Biomimetic nanoparticles have recently emerged as a novel drug delivery platform to improve drug biocompatibility and specificity at the desired disease site, especially the tumour microenvironment. Conventional nanoparticles often encounter rapid clearance by the immune system and have poor drug-targeting effects. The rapid development of nanotechnology provides an opportunity to integrate different types of biomaterials onto the surface of nanoparticles, which enables them to mimic the natural biological features and functions of the cells. This mimicry strategy favours the escape of biomimetic nanoparticles from clearance by the immune system and reduces potential toxic side effects. Despite the rapid development in this field, not much has progressed to the clinical stage. Thus, there is an urgent need to develop biomimetic-based nanomedicine to produce a highly specific and effective drug delivery system, especially for malignant tumours, which can be used for clinical purposes. Here, the recent developments for various types of biomimetic nanoparticles are discussed, along with their applications for cancer imaging and treatments.

Individual and successive detection of H2S and HClO in living cells and zebrafish by a dual-channel fluorescent probe with longer emission wavelength

Reactive oxygen species (ROS) and reactive sulfur species (RSS) participate in many physiological activities and help maintaining the redox homeostasis in biological system. The complicated intrinsic connection between specific ROS/RSS needs to be further explored. Herein, a novel fluorescent probe (MB-NAP-N₃) with longer emission wavelength has been rationally designed and synthesized based on the conjugation of the methylene blue moiety and the naphthalimide moiety for the detection of hypochlorous acid (HClO) and hydrogen sulfide (H₂S). The dual-signal probe exhibits rapid turn-on fluorescence responses for individual and successive detection of H₂S and HClO in green and red channels, respectively. Owning to its advantages such as fast response, good selectivity and high sensitivity, the probe was successfully applied to detect endogenous and exogenous HClO/H₂S in living cells. Furthermore, the outstanding luminescence performance makes it suitable for the visualization of the in vivo interaction between the two analytes in zebrafish.

Manganese/iron-based nanoprobes for photodynamic/chemotherapy combination therapy of tumor guided by multimodal imaging

Early diagnosis of tumors is crucial in selecting appropriate treatment options to achieve the desired therapeutic effect, but it is difficult to accurately diagnose cancer by a single imaging modality due to technical constraints. Therefore, we synthesized a type of Fe3O4 nanoparticle with manganese dioxide grown on the surface and then prepared it by loading photosensitive drugs and traditional Chinese medicine monomers to create an integrated diagnosis/treatment multifunctional nanoplatform: Fe3O4@MnO2-celastrol (CSL)/Ce6. This nanoplatform can have full advantage of the tumor microenvironment (TME) characteristics of hypoxia (hypoxia), acidic pH (acidosis), and increased levels of reactive oxygen species (e.g., H2O2), even outside the TME. Specific imaging and drug release can also enhance tumor therapy by adjusting the hypoxic state of the TME to achieve the combined effect of chemotherapy (CT) and photodynamic therapy (PDT). Moreover, the obtained Fe3O4@MnO2-CSL/Ce6 has H2O2- and pH-sensitive biodegradation and can release the anticancer drug celastrol (CSL) and photosensitizer Ce6 in TME and simultaneously generate O2 and Mn2+. Therefore, the "dual response" synergistic strategy also confers specific drug release on nanomaterials, relieves tumor hypoxia and antioxidant capacity, and achieves significant optimization of CT and PDT. Furthermore, the resulting Mn2+ ions and Fe3O4 nanoparticles can be used for T1/T2 magnetic resonance imaging on tumor-bearing mice, and the released Ce6 can simultaneously provide fluorescence imaging functions. Therefore, Fe3O4@MnO2-CSL/Ce6 realized the synergistic treatment of PDT and CT under multimodal near-infrared fluorescence/photoacoustic (photoacoustic) imaging monitoring, showing its great potential in the accurate medical treatment of tumors.

Photothermal bactericidal surfaces: killing bacteria using light instead of biocides

Recent developments of photothermal bactericidal surfaces based on immobilized photothermal agents to kill bacteria through hyperthermia effects are reviewed.

Emerging photothermal-derived multimodal synergistic therapy in combating bacterial infections

Due to the emerging bacterial resistance and the protection of tenacious biofilms, it is hard for the single antibacterial modality to achieve satisfactory therapeutic effects nowadays. In recent years, photothermal therapy (PTT)-derived multimodal synergistic treatments have received wide attention and exhibited cooperatively enhanced bactericidal activity. PTT features spatiotemporally controllable generation of hyperthermia that could eradicate bacteria without inducing resistance. The synergy of it with other treatments, such as chemotherapy, photo-dynamic/catalytic therapy (PDT/PCT), immunotherapy, and sonodynamic therapy (SDT), could lower the introduced laser density in PTT and avoid undesired overheating injury of normal tissues. Simultaneously, by heat-induced improvement of the bacterial membrane permeability, PTT is conducive for accelerated intracellular permeation of chemotherapeutic drugs as well as reactive oxygen species (ROS) generated by photosensitizers/sonosensitizers, and could promote infiltration of immune cells. Thereby, it could solve the currently existing sterilization deficiencies of other combined therapeutic modes, for example, bacterial resistance for chemotherapy, low drug permeability for PDT/PCT/SDT, adverse immunoreactions for immunotherapy, etc. Admittedly, PTT-derived synergistic treatments are becoming essential in fighting bacterial infection, especially those caused by antibiotic-resistant strains. This review firstly presents the classical and newly reported photothermal agents (PTAs) in brief. Profoundly, through the introduction of delicately designed nanocomposite platforms, we systematically discuss the versatile photothermal-derived multimodal synergistic therapy with the purpose of sterilization application. At the end, challenges to PTT-derived combinational therapy are presented and promising synergistic bactericidal prospects are anticipated.

Magnetically-driven drug and cell on demand release system using 3D printed alginate based hollow fiber scaffolds

Local delivery of drugs, proteins and living cells with on demand release manner using porous scaffolds has been widely used in the field of tissue engineering and cancer therapies. Drugs directly loaded in the porous scaffolds, are generally prone to free diffuse especially for long term incubation. Herein, in this study, hollow fiber alginate/iron oxide nanoparticles scaffolds were prepared by coaxial 3D printing with drugs, protein or living cells encapsulating in the core part (low concentration of alginate gels). Magnetically-driven on demand release was realized by extruding the loaded drugs, proteins and cells from the core part of the hollow fibers due to the deformation of the scaffolds under magnetic field. Additionally, the hollow fibers could sever as diffusion barriers to reduce uncontrolled diffusion of drugs, proteins and cells from scaffolds in the conditions of no required stimulation. The factors influencing the deformation of the scaffolds, as well as the release behavior were investigated. The data indicated that the scaffolds prepared by 10 wt% of alginate with 13% of iron oxide nanoparticles after crosslinking using 0.1 M CaCl₂ solution for 10 s showed repeated on demand release capability in vitro and in vivo under intermittently magnetic stimulation. Thus, this 3D printed alginate/iron oxide nanoparticles hollow scaffolds with on demand controlled delivery capability may prove useful for tissue engineering and disease therapies.

The Coppery Age: Copper (Cu)-Involved Nanotheranostics

As an essential trace element in the human body, transitional metal copper (Cu) ions are the bioactive components within the body featuring dedicated biological effects such as promoting angiogenesis and influencing lipid/glucose metabolism. The recent substantial advances of nanotechnology and nanomedicine promote the emerging of distinctive Cu-involved biomaterial nanoplatforms with intriguing theranostic performances in biomedicine, which are originated from the biological effects of Cu species and the physiochemical attributes of Cu-composed nanoparticles. Based on the very-recent significant progresses of Cu-involved nanotheranostics, this work highlights and discusses the principles, progresses, and prospects on the elaborate design and rational construction of Cu-composed functional nanoplatforms for a diverse array of biomedical applications, including photonic nanomedicine, catalytic nanotherapeutics, antibacteria, accelerated tissue regeneration, and bioimaging. The engineering of Cu-based nanocomposites for synergistic nanotherapeutics is also exemplified, followed by revealing their intrinsic biological effects and biosafety for revolutionizing their clinical translation. Finally, the underlying critical concerns, unresolved hurdles, and future prospects on their clinical uses are analyzed and an outlook is provided. By entering the "Copper Age," these Cu-involved nanotherapeutic modalities are expected to find more broad biomedical applications in preclinical and clinical phases, despite the current research and developments still being in infancy.

NIR light-assisted phototherapies for bone-related diseases and bone tissue regeneration: A systematic review

Recently, the rapid development of biomaterials has induced great interest in the precisely targeted treatment of bone-related diseases, including bone cancers, infections, and inflammation. Realizing noninvasive therapeutic effects, as well as improving bone tissue regeneration, is essential for the success of bone‑related disease therapies. In recent years, researchers have focused on the development of stimuli-responsive strategies to treat bone-related diseases and to realize bone regeneration. Among the various external stimuli for targeted therapy, near infrared (NIR) light has attracted considerable interests due to its high tissue penetration capacity, minimal damage toward normal tissues, and easy remote control properties. The main objective of this systematic review was to reveal the current applications of NIR light-assisted phototherapy for bone-related disease treatment and bone tissue regeneration. Database collection was completed by June 1, 2020, and a total of 81 relevant studies were finally included. We outlined the various therapeutic applications of photothermal, photodynamic and photobiomodulation effects under NIR light irradiation for bone‑related disease treatment and bone regeneration, based on the retrieved literatures. In addition, the advantages and promising applications of NIR light-responsive drug delivery systems for spatiotemporal-controlled therapy were summarized. These findings have revealed that NIR light-assisted phototherapy plays an important role in bone-related disease treatment and bone tissue regeneration, with significant promise for further biomedical and clinical applications.

Luminescent molecules towards precise cellular event regulation

A unique lanthanide complex which responds to near-infrared (NIR) stimulation was developed for remote regulation of cellular events. This molecule can be localized specifically on the cell surface. Upon NIR stimulation, strong emission of the complex can successfully modulate the activities of light-gated membrane channels and regulate the ion flux in vivo.

Near-infrared NIR irradiation and sodium hypochlorite: An efficacious association to counteract the Enterococcus faecalis biofilm in endodontic infections

New strategies are necessary for the prevention of endodontic infections caused by Enterococcus faecalis, a common resistant pathogen and biofilm producer. Aim of the present study was to compare the effects of Near-Infrared (NIR) Light-Emitting Diode (LED) irradiation and different concentrations of sodium hypochlorite (NaOCl) alone or combined to each other on the E. faecalis biofilm, on artificial and human dentin surfaces. E. faecalis ATCC 29212 preformed biofilms, on polystyrene wells and on dentin discs, were treated with 880 nm NIR irradiation and NaOCl at 4%, 2.5%, 1% and 0.5% alone and combined to each other (NIR irradiation plus NaOCl 1% or 0.5%) at 5 and 10 min. Treated biofilms were compared to the controls for (i) biofilm biomass evaluation, (ii) CFU count for the quantification of cultivable cells and (iii) cells viability. All the detected experimental conditions displayed a significant reduction of biofilm biomass (p < 0.001) and CFUs/mL (p < 0.01) in respect to the controls on both tested surfaces. The effects on the E. faecalis biomass, colony count and cell viability were not time-dependent except for NaOCl 2.5% and 1% in the biofilm biomass reductions on human dentin discs. NIR-LED irradiation alone showed a reduction of E. faecalis aggregates without interfering with cell viability whereas NaOCl alone expressed a killing effect in a concentration dependent way. The combination of NIR-LED irradiation with NaOCl 1% and 0.5% displayed a double effect of cluster disaggregation and cell killing. In particular, NIR-LED irradiation combined with NaOCl 0.5% displayed an anti-biofilm activity major than those expressed by NaOCl 0.5% alone (p = 0.001) with a reduction of biomass 93% vs 71% and 97% vs 25% after 10 min, on polystyrene wells and human dentin discs, respectively. The innovative use of NIR-LED irradiation combined at short times with low concentration of NaOCl (1% and 0.5%) is capable to reach a significant effect on E. faecalis biofilm, especially on human dentin discs.

Near-Infrared Multipurpose Lanthanide-Imaging Nanoprobes

Optical imaging plays a growing role in modern biomedical research and clinical applications due to its high sensitivity, superb spatiotemporal resolution and minimal hazards. Lanthanide-doped nanoparticles (LDNPs), as a classical category of luminescent materials, exhibit promising photostability, near-infrared (NIR)-excited frequency up-/down-converting capabilities, emission fine-tuning and multispectral features, which have greatly promoted the endeavors of deeper and clearer diagnostics in complex living conditions. This review focuses on the recent advances of LDNP-based multipurpose imaging studies using upconversion, downshifting, lifetime, photoacoustic and multimodal nanoprobes in the NIR (650-1000 nm) and the second near-infrared window (NIR-II, 1000-1700 nm). The principle and design of various functional, activatable, multiplexing or multimodal lanthanide-imaging nanoprobes (LINPs) as well as representative biophotonic applications are summarized in detail. In addition, the future perspectives and challenges for facilitating LINPs to clinical translations are discussed.

Recent Advances in Rare-Earth-Doped Nanoparticles for NIR-II Imaging and Cancer Theranostics

Fluorescence imaging in the second near infrared window (NIR-II, 1,000-1,700 nm) has been widely used in cancer diagnosis and treatment due to its high spatial resolution and deep tissue penetration depths. In this work, recent advances in rare-earth-doped nanoparticles (RENPs)-a novel kind of NIR-II nanoprobes-are presented. The main focus of this study is on the modification of RENPs and their applications in NIR-II in vitro and in vivo imaging and cancer theranostics. Finally, the perspectives and challenges of NIR-II RENPs are discussed.

Multifunctional DNA Polymer-Assisted Upconversion Therapeutic Nanoplatform for Enhanced Photodynamic Therapy

Although considerable clinical attempts on various kinds of cancers have been made, photodynamic therapy (PDT) still suffers from attenuated therapeutic effects because of the developed resistance of cancer cells. As a novel antiapoptosis protein, survivin has been demonstrated to be selectively overexpressed in a great number of human malignancies and plays a significant part in cancer progression and therapeutic resistance. Herein, we present an upconversion nanoplatform for enhanced PDT by DNAzyme-mediated gene silencing of survivin. In our system, a long single-stranded DNA (ssDNA) with a repetitive aptamer (AS1411) and survivin-targeted DNAzyme was fabricated by rolling circle amplification (RCA) and adsorbed on the upconversion nanoparticles (UCNPs) by electrostatic attraction. The multivalence of the ssDNA endows the upconversion nanoplatform with high recognition and loading capacity of photosensitizers and DNAzymes. When the nanoplatform is targeted internalized into cancer cells, PDT can be triggered by near-infrared (NIR) light to generate reactive oxygen species (ROS) for killing the cancer cells. Moreover, the encoded DNAzyme can efficiently inhibit the gene expression of survivin, providing the potential to enhance the efficiency of PDT. This study thus highlights the promise of an upconversion photodynamic nanoplatform for admirable combination therapy in cancer.

Extraspecific Manifestation of Nanoheater's Position Effect on Distinctive Cellular Photothermal Responses

Subcellular localization of nanoparticles plays critical roles in precision medicine that can facilitate an in-depth understanding of disease etiology and achieve accurate theranostic regulation via responding to the aiding stimuli. The photothermal effect is an extensively employed strategy that converts light into heat stimulation to induce localized disease ablation. Despite diverse manipulations that have been investigated in photothermal nanotheranostics, influences of nanoheaters' subcellular distribution and their molecular mechanism on cellular heat response remain elusive. Herein, we disclose the biological basis of distinguishable thermal effects at subcellular resolution by localizing photothermal upconversion nanoparticles into specific locations of cell compartments. Upon 808 nm light excitation, the lysosomal cellular uptake initialized by poly(ethylenimine)-modified nanoheaters promoted mitochondria apoptosis through the activation of Bid protein, whereas the cell surface nanoheaters anchored via metabolic glycol biosynthesis triggered necrosis by direct perturbation of the membrane structure. Intriguingly, these two different thermolyses revealed similar levels of heat shock protein expression in live cells. This study stipulates insights underlying the different subcellular positions of nanoparticles for the selective thermal response, which provides valuable perspectives on optimal precision nanomedicine.

Antibiotic-Free Antibacterial Strategies Enabled by Nanomaterials: Progress and Perspectives

Bacterial infection is one of the top ten leading causes of death globally and the worst killer in low-income countries. The overuse of antibiotics leads to ever-increasing antibiotic resistance, posing a severe threat to human health. Recent advances in nanotechnology provide new opportunities to address the challenges in bacterial infection by killing germs without using antibiotics. Antibiotic-free antibacterial strategies enabled by advanced nanomaterials are presented. Nanomaterials are classified on the basis of their mode of action: nanomaterials with intrinsic or light-mediated bactericidal properties and others that serve as vehicles for the delivery of natural antibacterial compounds. Specific attention is given to antibacterial mechanisms and the structure-performance relationship. Practical antibacterial applications employing these antibiotic-free strategies are also introduced. Current challenges in this field and future perspectives are presented to stimulate new technologies and their translation to fight against bacterial infection.

Mitochondria-targeting NO gas nanogenerator for augmenting mild photothermal therapy in the NIR-II biowindow

A mitochondria-targeting NO gas-releasing nanoplatform based on CuS-nanoplates has been designed for augmenting photothermal therapy by the synergistic effect.

Neodymium-Sensitized Nanoconstructs for Near-Infrared Enabled Photomedicine

Neodymium (Nd³⁺ )-sensitized nanoconstructs have gained increasing attention in recent decades due to their unique properties, especially optical properties. The design of various Nd³⁺ -sensitized nanosystems is expected to contribute to medical and health applications, due to their advantageous properties such as high penetration depth, excellent photostability, non-photobleaching, low cytotoxicity, etc. However, the low conversion efficiency and potential long-term toxicity of Nd³⁺ -sensitized nanoconstructs are huge obstacles to their clinical translations. This review article summarizes three energy transfer pathways of all kinds of Nd³⁺ -sensitized nanoconstructs focusing on the properties of Nd³⁺ ions and discusses their recent potential applications as near-infrared (NIR) enabled photomedicine. This review article will contribute to the design and fabrication of novel Nd³⁺ -sensitized nanoconstructs for NIR-enabled photomedicine, aiming for potentially safer and more efficient designs to get closer to clinical usage.

A Tumor Microenvironment-Responsive Biodegradable Mesoporous Nanosystem for Anti-Inflammation and Cancer Theranostics

A nanoplatform that integrates diagnostic and therapeutic functions with intrinsic tumor microenvironment-responsive biodegradability is highly desired. Herein, a biodegradable nanotheranostic agent based on hollow mesoporous organosilica nanoparticles (HMONs), followed by encapsulating of heat shock protein 90 (Hsp 90) inhibitor is described. Then, the pore-engineering including gating with bovine serum albumin-iridium oxide nanoparticles (BSA-IrO₂ ) and conjugation of polyethylene glycol (PEG) is conducted to yield 17AAG@HMONs-BSA-IrO₂ -PEG (AHBIP) nanotheranostics for multimode computed tomography (CT)/photoacoustic (PA) imaging-guided photodynamic therapy (PDT) and low-temperature photothermal therapy (PTT). Such nanoplatforms show extraordinary photothermal conversion efficiency, high cargo loading (35.4% for 17AAG), and stimuli-responsive release of 17AAG for inhibition of Hsp90, which induces cell apoptosis at low-temperatures (≈41 °C). Also, the IrO₂ simultaneously endows the nanotheranostics with catalytic activity in triggering the decomposition of H₂ O₂ into O₂ and thus reducing the tumor hypoxia, as well as protecting normal tissues against H₂ O₂ -induced inflammation. AHBIP shows good photocatalysis activity for PDT as a result of the generation of superoxide anion by laser irradiation. The resulting AHBIP-mediated synergistic PTT/PDT offers an outstanding therapeutic outcome both in vitro and in vivo. Overall, the incorporation of the BSA-IrO₂ and biodegradable HMONs into one nanoplatform has great potential for clinical applications.

Polydopamine Nanoparticles for Deep Brain Ablation via Near-Infrared Irradiation

Local resection or ablation remains an important approach to treat drug-resistant central neurological disease. Conventional surgical approaches are designed to resect the diseased tissues. The emergence of photothermal therapy (PTT) offers a minimally invasive alternative. However, their poor penetration and potential off-target effect limit their clinical application. Here, polydopamine nanoparticles (PDA-NPs) were prepared and characterized. Studies were performed to evaluate whether PDA-NPs combined with near-infrared (NIR) light can be used to ablate deep brain structures in vitro and in vivo. PDA-NPs were prepared with a mean diameter of ∼150 nm. The particles show excellent photothermal conversion efficiency. PDA-NPs did not show remarkable cytotoxicity against neuronal-like SH-SY5Y cell lines. However, it can cause significant cell death when combined with NIR irradiation. Transcranial NIR irradiation after PDA-NPs administration induced enhanced local hyperthermia as compared with NIR alone. Local temperature exceeded 60 °C after 6 min of irradiation plus PDA while it can only reach 48 °C with NIR alone. PTT with PDA (10 mg/mL, 3 μL) and NIR (1.5 W/cm²) can ablate deep brain structures precisely with an ablation volume of ∼6.5 mm³. Histological analysis confirmed necrosis and apoptosis in the targeted area. These results demonstrate the potential of NP-assisted PTT for the treatment against nontumorous central neurological diseases.

Synergistic photothermal/photodynamic suppression of prostatic carcinoma by targeted biodegradable MnO2 nanosheets

The biodegradability and clearance of metal-based nanomaterials have been questioned worldwide, which have greatly limited their clinical translation. Herein, ultrathin manganese dioxide (MnO2) nanosheets with broad near-infrared (NIR) absorption and pH-dependent degradation properties were prepared. After being modified with polyethylene glycol-cyclic arginine-glycineaspartic acid tripeptide (PEG-cRGD), the MnO2 nanosheets were then used as photothermal agent and nanocarrier to encapsulate chlorin e6 (Ce6) for targeted photothermal (PTT) and photodynamic (PDT) of cancer. As expected, the MnO2-PEG-cRGD nanosheets show high Ce6 loading capacity (351 mg/g), superb photothermal conversion performance (37.2%) and excellent colloidal stability. These nanosheets also exhibit pH-dependent and NIR-induced Ce6 release. Furthermore, the MnO2 nanosheets can be degraded by reacting with hydrogen peroxide in the acidic microenvironment, which are able to elevate the oxygen concentration in situ and thus reverses the tumor hypoxia. Thanks to these favorable properties and the cRGD-mediated tumor-targeted ability, the fabricated MnO2-PEG-cRGD/Ce6 nanocomposites can be effectively up taken by alpha-v beta-3 (αvβ3) integrin over-expressed prostatic carcinoma PC3 cells and achieve favorable therapeutic outcomes under a single 660 nm NIR laser, which is also verified by in vitro studies. The biodegradable MnO2-PEG-cRGD/Ce6 nanosheets developed in this work can be a promising nanoplatform for synergetic PTT/PDT cancer therapy.

InSe Nanosheets for Efficient NIR-II-Responsive Drug Release

Near-infrared-II (NIR-II) biowindow is appealing from the perspectives of larger maximum permissible exposure in comparison with the near-infrared-I biowindow, so the NIR-II-responsive drug-delivery nanoplatform is highly desirable. In this work, two-dimensional InSe nanosheets (InSe NSs) are modified with poly(ethylene glycol) and evaluated as an effective NIR-II-responsive cancer treatment nanoplatform. The InSe NSs synthesized by liquid exfoliation exhibit prominent NIR-II-responsive photothermal conversion efficiency (39.5%) and photothermal stability. Moreover, the InSe NSs have a doxorubicin (DOX) loading capacity as high as 93.6%, along with excellent NIR-II-responsive DOX release characteristic. The superior synergistic chemo/photothermal effects have also been demonstrated by the in vitro experiments in killing cancer cells. In combination with good biocompatibility, the InSe NSs have great potential in therapeutic applications.