Quasi‐Continuous Wave Near‐Infrared Excitation of Upconversion Nanoparticles for Optogenetic Manipulation of C. elegans

Optogenetics is an emerging powerful tool to investigate workings of the nervous system. However, the use of low tissue penetrating visible light limits its therapeutic potential. Employing deep penetrating near‐infrared (NIR) light for optogenetics would be beneficial but it cannot be used directly. This issue can be tackled with upconversion nanoparticles (UCNs) acting as nanotransducers emitting at shorter wavelengths extending to the UV range upon NIR light excitation. Although attractive, implementation of such NIR‐optogenetics is hindered by the low UCN emission intensity that necessitates high NIR excitation intensities, resulting in overheating issues. A novel quasi‐continuous wave (quasi‐CW) excitation approach is developed that significantly enhances multiphoton emissions from UCNs, and for the first time NIR light‐triggered optogenetic manipulations are implemented in vitro and in C. elegans. The approach developed here enables the activation of channelrhodopsin‐2 with a significantly lower excitation power and UCN concentration along with negligible phototoxicity as seen with CW excitation, paving the way for therapeutic optogenetics.     

氟氧化物中Er3+的上转换发光

研究了Er^3 离子氟氧化物上的转换发光。在980nm光的激发下,测定了Er^3 离子浓度（分别为1mol%、2mol%、3mol%）不同时材料上的转换发光光谱。在可见光范围内,观察到了强红光和绿光,并且在短波段也观察到了光的发射,波峰分别位于661.545、456、409和380nm处。还测量了各样品的上转换发光强度随激发强度的变化情况,由LogIvis-LogIin曲线可知,红光为双光子过程和三光子过程,绿光为三光子过程。并初步研究了此材料的上转换过程和上转换通道。     

NIR Biosensing of Neurotransmitters in Stem Cell‐Derived Neural Interface Using Advanced Core–Shell Upconversion Nanoparticles

Nondestructive neurotransmitter detection and real‐time monitoring of stem cell differentiation are both of great significance in the field of neurodegenerative disease and regenerative medicine. Although luminescent biosensing nanoprobes have been developed to address this need, they have intrinsic limitations such as autofluorescence, scattering, and phototoxicity. Upconversion nanoparticles (UCNPs) have gained increasing attention for various biomedical applications due to their high photostability, low auto‐fluorescent background, and deep tissue penetration; however, UCNPs also suffer from low emission intensities due to undesirable energy migration pathways. To address the aforementioned issue, a single‐crystal core–shell–shell “sandwich” structured UCNP is developed that is designed to minimize deleterious energy back‐transfer to yield bright visible emissions using low power density excitations. These UCNPs show a remarkable enhancement of luminescent output relative to conventional β‐NaYF4:Yb,Er codoped UCNPs and β‐NaYF4:Yb,Er@NaYF4:Yb “active shell” alike. Moreover, this advanced core–shell–shell UCNP is subsequently used to develop a highly sensitive biosensor for the ultrasensitive detection of dopamine released from stem cell‐derived dopaminergic‐neurons. Given the challenges of in situ detection of neurotransmitters, the developed NIR‐based biosensing of neurotransmitters in stem cell‐derived neural interfaces present a unique tool for investigating single‐cell mechanisms associated with dopamine, or other neurotransmitters, and their roles in neurological processes.     

Phytotoxicity,Translocation, and Biotransformation of NaYF4 Upconversion Nanoparticles in a Soybean Plant

The increasing uses of rare‐earth‐doped upconversion nanoparticles (UCNPs) have obviously caused many concerns about their potential toxicology on live organisms. In addition, the UCNPs can be released into the environment, then transported into edible crop plants, and finally entered into food chain. Here, the soybean is chosen as a model plant to study the subchronic phytotoxicity, translocation, and biotransformation of NaYF₄ UCNPs. The incubation with UCNPs at a relative low concentration of 10 μg mL^?1 leads to growth promotion for the roots and stems, while concentration exceeding 50 μg mL^?1 brings concentration‐dependent inhibition. Upconversion luminescence imaging and scanning electron microscope characterization show that the UCNPs can be absorbed by roots and parts of the adsorbed UCNPs are then transported through vessels to stems and leaves. The near‐edge X‐ray absorption fine structure spectra reveal that the adsorbed NaYF₄ nanoparticles are relatively stable during a 10 d incubation. Energy‐dispersive X‐ray spectrum further indicates that a small amount of NaYF₄ is dissolved/digested and can transform into Y‐phosphate clusters in roots.     

Expanding the Toolbox of Upconversion Nanoparticles for In Vivo Optogenetics and Neuromodulation

Optogenetics is an optical technique that exploits visible light for selective neuromodulation with spatio‐temporal precision. Despite enormous effort, the effective stimulation of targeted neurons, which are located in deeper structures of the nervous system, by visible light, remains a technical challenge. Compared to visible light, near‐infrared illumination offers a higher depth of tissue penetration owing to a lower degree of light attenuation. Herein, an overview of advances in developing new modalities for neural circuitry modulation utilizing upconversion‐nanoparticle‐mediated optogenetics is presented. These developments have led to minimally invasive optical stimulation and inhibition of neurons with substantially improved selectivity, sensitivity, and spatial resolution. The focus is to provide a comprehensive review of the mechanistic basis for evaluating upconversion parameters, which will be useful in designing, executing, and reporting optogenetic experiments.     

Ultrafast Synthesis of Novel Hexagonal Phase NaBiF4 Upconversion Nanoparticles at Room Temperature

Upconversion (UC) nanoparticles (UCNPs) have evoked considerable attention in many fields owing to their fascinating features. However, rigorous synthesis conditions and expensive raw materials often limit their further applications. Here, a novel hexagonal phase NaBiF₄ UC matrix through a very facile method (one min only at room temperature) is synthesized. The nanoparticles show good monodispersity with uniform size. Under the 980 nm irradiation, Yb³⁺/Ln³⁺ (Ln = Er, Ho, Tm) codoped NaBiF₄ nanoparticles show excellent UC luminescence (UCL). This super facile synthesis strategy and excellent matrix materials enable to achieve UCL in such low temperature, opening a new gateway for the UCNPs applied to a variety of areas in the future.     

Nd3+掺杂的NaYF4:Yb@NaYF4:Ho上转换纳米颗粒的光谱分析

上转换纳米颗粒因具有良好的穿透深度和发光强度被广泛地应用在生物标记或生物成像中。实验制备了核壳结构的NaYF₄:Yb@NaYF₄:Ho纳米颗粒, 分散均匀, 粒径在50 nm左右。通过光谱分析可知, 该纳米颗粒可在980 nm激光激发下发射波长为650 nm为主的发射光。进一步对该核壳结构的NaYF₄:Yb@NaYF₄:Ho纳米颗粒进行Nd³⁺掺杂, 制备了可被800 nm激光激发且发射强红光的纳米颗粒。通过比较多种不同结构的Nd³⁺掺杂NaYF₄:Yb@NaYF₄:Ho纳米颗粒的荧光光谱发现, NaYF₄:Yb@NaYF₄:Ho,Nd纳米颗粒发射光最强, 表明Nd³⁺掺杂在NaYF₄:Yb@NaYF₄:Ho纳米颗粒的壳层中最佳。最后对NaYF₄:Yb³⁺50%@NaYF₄:Ho³⁺1%,Nd³⁺x%纳米颗粒Nd³⁺离子的掺杂浓度进行优化, 实验结果表明: Nd³⁺掺杂浓度为30%时,该纳米颗粒在800 nm激光激发下发光强度最强。     

Efficacy Dependence of Photodynamic Therapy Mediated by Upconversion Nanoparticles: Subcellular Positioning and Irradiation Productivity

Singlet oxygen (¹O₂), as an important kind of reactive oxygen species (ROS) and main therapeutic agent in photodynamic therapy (PDT), only have a half‐life of 40 ns and an effective radius of 20 nm, which cause significant obstacles for improving PDT efficacy. In this work, novel upconversion nanoparticle (UCN)‐based nanoplatforms are developed with a minimized distance between UCNs and a photosensitizer, protoporphyrin IX (PpIX), and a controllable payload of PpIX, to enhance and control ROS production. The ability of the nanoplatform to target different subcellular organelles such as cell membrane and mitochondria is demonstrated via surface modification of the nanoplatform with different targeting ligands. The results show that the mitochondria‐targeting nanoplatforms result in significantly increased capability of both tumor cell killing and inhibition of tumor growth. Subcellular targeting of nanoparticles leads to the death of cancer cells in different manners. However, the efficiency of ROS generation almost have no influence on the tumor cell viability during the period of evaluation. These findings suggest that specific subcellular targeting of the nanoplatforms enhances the PDT efficacy more effectively than the increase of ROS production, and may shed light on future novel designs of effective and controllable PDT nanoplatforms.     

Upconversion Luminescence Resonance Energy Transfer (LRET)‐Based Biosensor for Rapid and Ultrasensitive Detection of Avian Influenza Virus H7 Subtype

Avian influenza viruses (AIV) with good adaptation and various mutations have threatened both human and animals’ health. The H7 subtypes have the potential to cause pandemic threats to human health due to the highly pathogenic characteristics. Therefore, it is quite urgent to develop a novel biosensor for rapid and sensitive detection of H7 subtypes. In this work, a biosensor based on luminescence resonance energy transfer (LRET) from BaGdF₅:Yb/Er upconversion nanoparticles (UCNPs) to gold nanoparticles (AuNPs) has been developed for rapid and sensitive H7 subtypes detection. The amino modified capture oligonucleotide probes are covalently linked to poly(ethylenimine) (PEI) modified BaGdF₅:Yb/Er UCNPs. The thiol modified oligonucleotides with H7 hemagglutinin gene sequence are conjugated to surfaces of AuNPs. The hybridization process between complementary strands of H7 Hemagglutinin gene and its probe brings the energy donor and acceptor into close proximity, leading to the quenching of fluorescence of UCNPs. A linear response is obtained ranging from 10 pm to 10 nm and the limit of detection (LOD) is around 7 pm with detection time around 2 hours. This biosensor is expected to be a valuable diagnostic tool for rapid and sensitive detection of AIV.     

Red‐Emitting Upconverting Nanoparticles for Photodynamic Therapy in Cancer Cells Under Near‐Infrared Excitation

Upconverting nanoparticles (UCNPs) have attracted considerable attention as potential photosensitizer carriers for photodynamic therapy (PDT) in deep tissues. In this work, a new and efficient NIR photosensitizing nanoplatform for PDT based on red‐emitting UCNPs is designed. The red emission band matches well with the efficient absorption bands of the widely used commercially available photosensitizers (Ps), benefiting the fluorescence resonance energy transfer (FRET) from UCNPs to the attached photosensitizers and thus efficiently activating them to generate cytotoxic singlet oxygen. Three commonly used photosensitizers, including chlorine e6 (Ce6), zinc phthalocyanine (ZnPc) and methylene blue (MB), are loaded onto the alpha‐cyclodextrin‐modified UCNPs to form Ps@UCNPs complexes that efficiently produce singlet oxygen to kill cancer cells under 980 nm near‐infrared excitation. Moreover, two different kinds of drugs are co‐loaded onto these nanoparticles: chemotherapy drug doxorubicin and PDT agent Ce6. The combinational therapy based on doxorubicin (DOX)‐induced chemotherapy and Ce6‐triggered PDT exhibits higher therapeutic efficacy relative to the individual means for cancer therapy in vitro.     

有机配体对NaBiF4:Yb3+/Er3+上转换纳米粒子形貌和发光性能的调控研究

本工作采用一锅溶剂热法分别制备了不同有机配体修饰的NaBiF₄:Yb³⁺/Er³⁺上转换纳米粒子(UCNPs), 并对其形貌和发光性能进行了研究。实验表明, 有机配体的软模板和导向作用可调控UCNPs的粒径和形貌, 且有机配体的缺陷钝化作用会使其发光增强。其中, 以十六烷基三甲基溴化铵(CTAB)和十六烷基三甲基氯化铵(CTAC)修饰的UCNPs的增强效果最为显著, 强度大约增加了9倍。此外, 本研究进一步考察了该UCNPs在不同的温度和pH条件下的发光强度的变化规律。结果表明, 在30~90 ℃之间, 其发光强度随着温度的升高而降低; 在强酸和强碱环境中, 其发光强度显著降低, 而在pH为5~6时, 其发光强度最大。