NIR-to-NIR Deep Penetrating Nanoplatforms Y2O3:Nd3+/Yb3+@SiO2@Cu2S toward Highly Efficient Photothermal Ablation

Cold-Responsive Hyaluronated Upconversion Nanoplatform for Transdermal Cryo-Photodynamic Cancer Therapy

Cryotherapy leverages controlled freezing temperature interventions to engender a cascade of tumor-suppressing effects. However, its bottleneck lies in the standalone ineffectiveness. A promising strategy is using nanoparticle therapeutics to augment the efficacy of cryotherapy. Here, a cold-responsive nanoplatform composed of upconversion nanoparticles coated with silica - chlorin e6 - hyaluronic acid (UCNPs@SiO2-Ce6-HA) is designed. This nanoplatform is employed to integrate cryotherapy with photodynamic therapy (PDT) in order to improve skin cancer treatment efficacy in a synergistic manner. The cryotherapy appeared to enhance the upconversion brightness by suppressing the thermal quenching. The low-temperature treatment afforded a 2.45-fold enhancement in the luminescence of UCNPs and a 3.15-fold increase in the photodynamic efficacy of UCNPs@SiO2-Ce6-HA nanoplatforms. Ex vivo tests with porcine skins and the subsequent validation in mouse tumor tissues revealed the effective HA-mediated transdermal delivery of designed nanoplatforms to deep tumor tissues. After transdermal delivery, in vivo photodynamic therapy using the UCNPs@SiO2-Ce6-HA nanoplatforms resulted in the optimized efficacy of 79% in combination with cryotherapy. These findings underscore the Cryo-PDT as a truly promising integrated treatment paradigm and warrant further exploring the synergistic interplay between cryotherapy and PDT with bright upconversion to unlock their full potential in cancer therapy.

Controlled Growth Cu2S Nanoarrays with High-Performance Photothermal Properties

The controlled growth of Cu₂S nanoarrays was constructed by a facile two-step impregnation synthesis route. The as-synthesized Cu₂S/CuO@Cu samples were precisely characterized in terms of surface morphology, phase, composition, and oxidation states. At the laser irradiation of 808 nm, Cu₂S/CuO@Cu heated up to 106 °C from room temperature in 120 s, resulting in an excellent photothermal conversion performance. The Cu₂S/CuO@Cu exhibited excellent cycling performance-sustaining the photothermal performance during five heating-cooling cycles. The finite difference time domain (FDTD) simulation of optical absorption and electric field distributions assured the accuracy and reliability of the developed experimental conditions for acquiring the best photothermal performance of Cu₂S/CuO@Cu.

Novel YOF-Based Theranostic Agents with a Cascade Effect for NIR-II Fluorescence Imaging and Synergistic Starvation/Photodynamic Therapy of Orthotopic Gliomas

Accurate diagnosis and highly effective treatment of glioblastoma are still challenges in clinic. Near-infrared (NIR) light triggered fluorescence imaging and photodynamic therapy (PDT) showed the potential for theranostics of glioblastoma, but the presence of blood-brain barrier (BBB) and hypoxia limited treatment effect. Herein, the novel theranostic nanoagents with YOF:Nd³⁺ as core, MnO₂ as shell, and further loading photosensitizer (indocyanine green, ICG) and glucose oxidase (GOx) were successfully constructed, and further modified with lactoferrin to endow them with BBB penetration and target abilities (YOF:Nd³⁺@MnO₂-ICG-GOx-LF, YMIGL). The YOF:Nd³⁺ core with good fluorescence performances makes YMIGL act as promising probes for fluorescence imaging in the second biowindow (NIR-II FL). The combination of GOx and MnO₂ shell significantly increased the O₂ generation from the cascade reactions and consumed glucose, improving the treatment effect of PDT and achieving starvation treatment (ST). These theranostic nanoagents exhibit a highly efficient inhibition effect on orthotopic gliomas by cascade reactions, which improved PDT and ST.

Folate receptor-targeting semiconducting polymer dots hybrid mesoporous silica nanoparticles against rheumatoid arthritis through synergistic photothermal therapy, photodynamic therapy, and chemotherapy

With ideal optical properties, semiconducting polymer quantum dots (SPs) have become a research focus in recent years; a considerable number of studies have been devoted to the application of SPs in non-invasive and biosafety phototherapy with near-infrared (NIR) lasers. Nevertheless, the relatively poor stability of SPs in vitro and in vivo remains problematic. PCPDTBT was chosen to synthesize photothermal therapy (PTT) and photodynamic therapy (PDT) dual-model SPs, considering its low band gap and desirable absorption in the NIR window. For the first time, cetrimonium bromide was used as a stabilizer to guarantee the in vitro stability of SPs, and as a template to prepare SP hybrid mesoporous silica nanoparticles (SMs) to achieve long-term stability in vivo. The mesoporous structure of SMs was used as a reservoir for the hypoxia-activated prodrug Tirapazamine (TPZ). SMs were decorated with polyethylene glycol-folic acid (SMPFs) to specifically target activated macrophages in rheumatoid arthritis (RA). Upon an 808 nm NIR irradiation, the SMPFs generate intracellular hyperthermia and excessive singlet oxygen. Local hypoxia caused by molecular oxygen consumption simultaneously activates the cytotoxicity of TPZ, which effectively kills activated macrophages and inhibits the progression of arthritis. This triple PTT-PDT-chemo synergistic treatment suggests that SMPFs realize the in vivo application of SPs and may be a potential nano-vehicle for RA therapy with negligible side-toxicity.

Near-Infrared-Triggered Upconverting Nanoparticles for Biomedicine Applications

Due to the unique properties of lanthanide-doped upconverting nanoparticles (UCNP) under near-infrared (NIR) light, the last decade has shown a sharp progress in their biomedicine applications. Advances in the techniques for polymer, dye, and bio-molecule conjugation on the surface of the nanoparticles has further expanded their dynamic opportunities for optogenetics, oncotherapy and bioimaging. In this account, considering the primary benefits such as the absence of photobleaching, photoblinking, and autofluorescence of UCNPs not only facilitate the construction of accurate, sensitive and multifunctional nanoprobes, but also improve therapeutic and diagnostic results. We introduce, with the basic knowledge of upconversion, unique properties of UCNPs and the mechanisms involved in photon upconversion and discuss how UCNPs can be implemented in biological practices. In this focused review, we categorize the applications of UCNP-based various strategies into the following domains: neuromodulation, immunotherapy, drug delivery, photodynamic and photothermal therapy, bioimaging and biosensing. Herein, we also discuss the current emerging bioapplications with cutting edge nano-/biointerfacing of UCNPs. Finally, this review provides concluding remarks on future opportunities and challenges on clinical translation of UCNPs-based nanotechnology research.

Upconversion nanoparticles modified by Cu2S for photothermal therapy along with real-time optical thermometry

Highly effective photothermal conversion performance coupled with high resolution temperature detection in real time is urgently needed for photothermal therapy (PTT). Herein, ultra-small Cu₂S nanoparticles (NPs) were designed to absorb on the surface of NaScF₄: Yb³⁺/Er³⁺/Mn²⁺@NaScF₄@SiO₂ NPs to form a central-satellite system, in which the Cu₂S NPs play the role of providing significant light-to-heat conversion ability and the Er³⁺ ions in the NaScF₄: Yb³⁺/Er³⁺/Mn²⁺ cores act as a thermometric probe based on the fluorescence intensity ratio (FIR) technology operating in the biological windows. A wavelength of 915 nm is used instead of the conventional 980 nm excitation wavelength to eliminate the laser induced overheating effect for the bio-tissues, by which Yb³⁺ can also be effectively excited. The temperature resolution of the FIR-based optical thermometer is determined to be better than 0.08 K over the biophysical temperature range with a minimal value of 0.06 K at 298 K, perfectly satisfying the requirements of biomedicine. Under the radiation of 915 nm light, the Cu₂S NPs exhibit remarkable light-to-heat conversion capacity, which is proved by photothermal ablation testing of E. coli. The results reveal the enormous potential of the present NPs for PTT integrated with real-time temperature sensing with high resolution.

Cr,Yb-codoped Ca2LaHf2Al3O12 garnet phosphor: electronic structure, broadband NIR emission and energy transfer properties

The combination of a broadband near-infrared (NIR) phosphor and phosphor-converted light-emitting diodes (pc-LEDs) has proven to be an ideal choice for a high-efficiency NIR light source. Here, a garnet-type NIR Ca₂LaHf₂Al₃O₁₂:Cr³⁺ phosphor is obtained and its emission covered most of the NIR spectral range. Excited by 460 nm blue light, the maximum peak was located at 780 nm with a full width at half maximum (FWHM) of ∼141 nm and an internal quantum efficiency (IQE) of 33%. Moreover, the NIR spectra can be broadened by doping Yb³⁺ into the Ca₂LaHf₂Al₃O₁₂:Cr³⁺ garnet phosphor. A super broad FWHM of 300 nm and reduced thermal quenching were acquired, originating from the energy transfer of Cr³⁺→ Yb³⁺. The energy transfer process of Cr³⁺ and Yb³⁺ is described by means of an energy level diagram and time-resolved spectrum. Finally, a NIR pc-LED is fabricated by combining the Ca₂LaHf₂Al₃O₁₂:Cr³⁺,Yb³⁺ phosphor with blue chips, which has a photoelectric conversion efficiency of 10%. These results demonstrate the great potential of Ca₂LaHf₂Al₃O₁₂:Cr³⁺,Yb³⁺ in super broadband NIR pc-LED applications.

Tumor-targeting multi-shelled hollow nanospheres as drug loading platforms for imaging-guided combinational cancer therapy

In this work, we developed multi-shelled hollow nanospheres [RGD@am-ZnO@CuO@Au@DOX HNSs] as multifunctional therapeutic agents to achieve effective and targeted Zn2+/Cu2+ therapy, induced drug delivery under low pH/red-light conditions, and enhanced phototherapy under single red-light. The photothermal and photodynamic performance of am-ZnO@CuO@Au HNSs was enhanced relative to that of am-ZnO nanoparticles (NPs) or am-ZnO@CuO HNSs by utilizing the resonance energy transfer process and broad red-light absorption. The pH-sensitive am-ZnO@CuO@Au HNSs were dissolved to Zn2+/Cu2+ in the acidic endosomes/lysosomes of cancer cells, resulting in a cancer cell killing effect. The release performance of doxorubicin (DOX) from RGD@am-ZnO@CuO@Au@DOX HNSs was evaluated under low pH and red-light-irradiated conditions, and targeting of HNSs was confirmed by dual-modal imaging (magnetic resonance/fluorescence) of the tumor area. Moreover, in vivo synergistic therapy using RGD@am-ZnO@CuO@Au@DOX HNSs was further evaluated in mice bearing human pulmonary adenocarcinoma (A549) cells, achieving a remarkable synergistic antitumor effect superior to that obtained by monotherapy. This study validated that RGD@am-ZnO@CuO@Au@DOX HNSs can be a promising candidate for efficient postoperative cancer therapy.

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.

Deep-Tissue Photothermal Therapy Using Laser Illumination at NIR-IIa Window

Photothermal therapy (PTT) using near-infrared (NIR) light for tumor treatment has triggered extensive attentions because of its advantages of noninvasion and convenience. The current research on PTT usually uses lasers in the first NIR window (NIR-I; 700-900 nm) as irradiation source. However, the second NIR window (NIR-II; 1000-1700 nm) especially NIR-IIa window (1300-1400 nm) is considered much more promising in diagnosis and treatment as its superiority in penetration depth and maximum permissible exposure over NIR-I window. Hereby, we propose the use of laser excitation at 1275 nm, which is approved by Food and Drug Administration for physical therapy, as an attractive technique for PTT to balance of tissue absorption and scattering with water absorption. Specifically, CuS-PEG nanoparticles with similar absorption values at 1275 and 808 nm, a conventional NIR-I window for PTT, were synthesized as PTT agents and a comparison platform, to explore the potential of 1275 and 808 nm lasers for PTT, especially in deep-tissue settings. The results showed that 1275 nm laser was practicable in PTT. It exhibited much more desirable outcomes in cell ablation in vitro and deep-tissue antitumor capabilities in vivo compared to that of 808 nm laser. NIR-IIa laser illumination is superior to NIR-I laser for deep-tissue PTT, and shows high potential to improve the PTT outcome.

Cu2S nanosheets for ultrashort pulse generation in the near-infrared region

2D metal chalcogenide materials have received enormous attention due to their extraordinary bio-chemical, electronic, magnetic, thermal and optical properties. Compared with the typical two-dimensional transition metal dichalcogenides (TMDs) and topological insulators, cuprous sulfide (Cu2S) has very different two-dimensional lattice structures, along with excellent electro-catalysis and high conductivity. However, the nonlinear optical properties of Cu2S have never been studied until now. Here, the nonlinear photonics characteristics of Cu2S and its application in ultrafast lasers have been systematically studied for the first time. Through optical deposition of Cu2S nanosheets on a tapered fiber, the nonlinear optical properties of Cu2S nanosheets are measured through the interaction with the evanescent field. The results indicate that superior nonlinear saturable absorption properties with a modulation depth of 0.51% are achieved. An erbium-doped fiber (EDF) laser is constructed to verify the performance of the Cu2S saturable absorber (SA). The results show that an output pulse with 8.06 MHz repetition rate, 1.04 ps pulse duration, 1530.4 nm central wavelength and 3.1 nm spectral width without an obvious Kelly sideband is obtained. Considering the diversity of the metal chalcogenide family, various engineering applications may be developed from the nonlinear saturable absorption characteristics of Cu2S, including optical fiber communication/sensing, precision optical metrology, material processing and nonlinear optics.

In situ construction of the BiOCl/Bi2Ti2O7 heterojunction with enhanced visible-light photocatalytic activity

Herein, a BiOCl/Bi₂Ti₂O₇ heterojunction was prepared as an efficient visible light-driven photocatalyst through an in situ hydrothermal method, and its photocatalytic properties were investigated via a comparable method.

Upconverting LuVO4:Nd3+/Yb3+/Er3+@SiO2@Cu2S Hollow Nanoplatforms for Self-monitored Photothermal Ablation

Self-monitored photothermal therapy (PTT) with minimal collateral damages has emerged as a challenging strategy for antibacterial and cancer treatments, which could be fulfilled via the rational integration of luminescent thermometry and photothermal ablation within a single upconverting (UC) nanoplatform. Herein, 808 nm light-driven dual-functional nanoplatforms LuVO₄:Nd³⁺/Yb³⁺/Er³⁺@SiO₂@Cu₂S were successfully developed using olivelike LuVO₄:Nd³⁺/Yb³⁺/Er³⁺ hollow nanoparticles as the thermal-sensing core and ultrasmall Cu₂S nanoparticles as the photothermal satellite. Irradiated by 808 nm laser, thermal-sensing behaviors of samples were evaluated based on the high-purity Er³⁺ green emissions, while the surface-attached Cu₂S exhibited superior photothermal effects due to the efficient absorption of incident laser and near-infrared emissions from the luminescent core. The feasibility of bifunctional samples acting as self-monitored photothermal agents in subtissues and antibacterial agents against drug-resistant bacteria was separately assessed. Results provide deeper insights into the desirable design of 808 nm-driven multifunctional nanoplatforms with intense UC emission, sensitive thermometry, and effective photothermal conversion toward self-monitored PTT with high therapeutic accuracy.