Rational design of biodegradable semiconducting polymer nanoparticles for NIR-II fluorescence imaging-guided photodynamic therapy

Semiconducting polymer nanoparticles(SPNs)have shown great promise in second near-infrared window(NIR-II)phototheranostics.However,the issue of long metabolic time significantly restricts the clinical application of SPNs.In this study,we rationally designed a biodegradable SPN(BSPN50)for NIR-II fluorescence imaging-guided photodynamic therapy(PDT).BSPN50 is prepared by encapsulating a biodegradable SP(BSP50)with an amphiphilic copolymer F-127.BSP50 is composed of NIR-II fluorescent diketopyrrolopyrrole(DPP)segment and degradable poly(phenylenevinylene)(PPV)segment with the ratio of 50/50.BSPN50 has both satisfactory degradability under myeloperoxidase(MPO)/hydrogen peroxide(H_(2)O_(2))and NIR-II fluorescence emission upon 808 nm laser excitation.Furthermore,BSPN50 shows good photodynamic efficacy under 808 nm laser irradiation.BSPN50 shows a faster degradation rate than BSPN100 which has no PPV segment both in vitro and in vivo.In addition,BSPN50 can effectively diagnose tumor via NIR-II fluorescence imaging and inhibit the tumor growth by PDT.Thus,our study provides a rational approach to construct biodegradable nanoplatforms for efficient tumor NIR-II phototheranostics.

Intelligent polymeric hydrogen sulfide delivery systems for therapeutic applications

Hydrogen sulfide(H_(2)S)plays an important role in regulating various pathological processes such as protecting mammalian cell from harmful injuries,promoting tissue regeneration,and regulating the process of various diseases caused by physiological disorders.Studies have revealed that the physiological effects of H_(2)S are highly associated with its concentrations.At relatively low concentration,H_(2)S shows beneficial functions.However,long-time and high-dose donation of H_(2)S would inhibit regular biological process,resulting in cell dysfunction and apoptosis.To regulate the dosage of H_(2)S delivery for precision medicine,H_(2)S delivery systems with intelligent characteristics were developed and a variety of biocompatibility polymers have been utilized to establish intelligent polymeric H_(2)S delivery systems,with the abilities to specifically target the lesions,smartly respond to pathological microenvironments,as well as real-timely monitor H_(2)S delivery and lesion conditions by incorporating imaging-capable moieties.In this review,we focus on the design,preparation,and therapeutic applications of intelligent polymeric H_(2)S delivery systems in cardiovascular therapy,inflammatory therapy,tissue regenerative therapy,cancer therapy and bacteria-associated therapy.Strategies for precise H_(2)S therapies especially imaging-guided H_(2)S theranostics are highlighted.Since H_(2)S donors with stimuli-responsive characters are vital components for establishing intelligent H_(2)S delivery systems,the development of H_(2)S donors is also briefly introduced.

透明质酸纳米材料在荧光/光声成像和光疗中的应用

荧光/光声成像和光疗技术的生物医学应用引起了人们越来越多的关注,然而很多荧光/光声造影剂存在生物相容性较差,缺乏肿瘤靶向性,信噪比较低,功能单一等共性问题,严重限制其诊疗应用.透明质酸具有优异的生物相容性和主动肿瘤靶向性,可被透明质酸酶降解,并且易于化学修饰和实现多种超分子弱相互作用力协同工作.因此,人们将透明质酸与荧光/光声造影剂结合制备纳米材料,使其在细胞乃至活体的标记性能和治疗效果获得了很大的改善.本文综述了将两类物质结合制备纳米材料的方法,着重阐述了纳米材料的结构与性能关系,为其未来设计和开发提供了指导,最后对存在的主要问题以及未来的重要研究方向进行了分析和展望.

近红外二区发光稀土纳米材料的设计及生物成像应用

近年来,近红外二区(NIR-II,1000~1700 nm)荧光成像因其较高的空间分辨率、较深的组织穿透能力,在分子影像领域引起了广泛的关注。常见的NIR-II发光材料(如有机小分子、共轭聚合物、量子点等)通常具有光稳定性差、荧光量子产率低、斯托克斯位移小、荧光峰宽等问题,限制了这一新型成像技术的进一步发展与应用。稀土纳米材料由于其独特的发光特性,能够较好地克服这些不足,近年来不同结构的稀土纳米材料也逐渐被设计开发并应用于近红外二区荧光成像与检测,展示出了巨大的应用潜力。本综述首先介绍了稀土纳米材料的光学特性,然后按敏化离子的不同(Yb^(3+)、Nd^(3+)、Er^(3+)、Tm^(3+))详细介绍了近红外二区稀土纳米材料的设计方法及相关应用,最后对稀土纳米材料在近红外二区成像领域的进一步发展进行了展望。

激活型有机光声造影剂的应用

光声(PA)成像作为一种结合了光学和声学成像优势的新型成像方式,具有深层组织穿透和高空间分辨率等优点,在重大疾病的早期影像诊断方面有着巨大的应用前景。然而传统的PA造影剂依然存在信噪比低、选择性及特异性差等不足,容易产生假阳性诊断结果。激活型PA造影剂可以有效的降低背景噪声,并提升成像的灵敏度和特异性,是目前PA造影剂设计与构筑的主要趋势。本综述首先简单介绍了PA成像的原理,然后结合近几年在金属离子、酶、活性氮和活性氧等相关方面的生物成像应用,梳理了可激活探针在不同微环境中的响应方式。最后,对激活型探针在PA成像中的应用进行了总结和展望。

Highly selective detection of copper(Ⅱ) by a “ligand-free” conjugated copolymer in nucleophilic solvents

The synthesis of N-cyclohexyl carbamate-attached fluorene-alt-phenylene copolymer(PFPNCC)and the use of PFPNCC as a“ligand-free”fluorescent chemosensor for Cu(Ⅱ)are described.Addition of Cu(Ⅱ)can efficiently quench the fluorescence of PFPNCC in nucleophilic solvents such as DMF and DMSO,but not in low nucleophilic solvents such as 1,4-dioxane and THF.Ultraviolet-visible spectra of the mixture of the conjugated polymer and Cu(Ⅱ)indicate the presence of a reduced Cu(Ⅰ)ion in the solution.Furthermore,fluorescence recovery of PFPNCC observed at low temperature suggests that the quenching and reducing mechanism is most probably due to a photo-induced electron transfer from excited PFPNCC to Cu(Ⅱ).Our findings provide a novel strategy for highly selective conjugated polymer-based chemosensors for various target analytes,albeit“ligand-free”.

Advanced technologies for single-cell in situ protein profiling

Cells are inherently heterogeneous to achieve a diverse spectrum of biological functions.To understand the underlying protein machinery that achieves these fascinating functions,it is important to develop advanced analytical methods that can profile proteins in their native environment,as protein expression,aggregation,degradation,and regulation define both normal physiology as well as pathogenicity.Genome and transcriptome sequencing have seen major advances at the single-cell levels,but comprehensive proteomic profiling is still challenging.The conventional proteomic methods,such as enzyme-linked immunosorbent assay(ELISA),western blot,and protein chips,can characterize biomarkers of interest.Still,these ensemble techniques are unsuitable for single-cell studies.Increasing evidence has shown the significance of in situ,sensitive,quantitative,and multiplexed profiling of biomarkers in single cells for diagnosis and treatment guidance.Here,we review the recent development of advanced imaging and spectroscopy techniques,including mass cytometry,immunofluorescence,and surfaceenhanced Raman spectrometry(SERS)for single-cell proteomic imaging.We also provide our view on the challenges and the outlook.

An Improved Turn-On Aptasensor for Thrombin Detection Using Split Aptamer Fragments and Graphene Oxide

An improved tum-on aptasensor for thrombin detection using split aptamer fragments and graphene oxide （GO） was reported. The thrombin-binding aptamer （Aptl5） was split into two parts for target recognition, an 8-base se- quence labeled with fluorescein （FAM-Apt-A） and a 7-base oligonucleotide sequence （Apt-B）. In the absence of target protein, the fluorescence of FAM-Apt-A/Apt-B was quenched by GO through n-n stacking between GO and single-stranded DNA. However, when thrombin was introduced into the system, a target-induced G-quadruplex forms with two split aptamer fragments and thrombin. The fluorescence recovered due to weak interaction between G-quadruplex and GO. Compared to the strategy using intact aptamer, probe concentration was lowered, and an improved sensitivity was obtained. Moreover, heating process to avoid unfavorable secondary structure was avoided due to the use of shorter split aptamer fragments.

Near-Infrared-Excitable Organic Ultralong Phosphorescence through Multiphoton Absorption

Organic ultralong room-temperature phosphorescence(OURTP)with a long-lived triplet excited state up to several seconds has triggered widespread research interests,but most OURTP materials are excited by only ultraviolet(UV)or blue light owing to their unique stabilized triplet-and solid-state emission feature.Here,we demonstrate that near-infrared-(NIR-)excitable OURTP molecules can be rationally designed by implanting intra/intermolecular charge transfer(CT)characteristics into Haggregation to stimulate the efficient nonlinear multiphoton absorption(MPA).The resultant upconverted MPA-OURTP show ultralong lifetimes over 0.42 s and a phosphorescence quantum yield of~37%under both UV and NIR light irradiation.Empowered by the extraordinary MPA-OURTP,novel applications including two-photon bioimaging,visual laser power detection and excitation,and lifetime multiplexing encryption devices were successfully realized.These discoveries illustrate not only a delicate design map for the construction of NIR-excitable OURTP materials but also insightful guidance for exploring OURTP-based nonlinear optoelectronic properties and applications.

Multifunctional shape-dependent plasmonic nanoprobe by enzymatic etching of single gold triangular nanoplate

Hydrogen peroxide(H2O2),as a signaling molecule,plays a vital role in a wide variety of signaling transduction processes,aging,and diseases.However,the excessive production of H2O2 causes various diseases.Herein,we develop a novel method for H2O2 detection in live cells via dark-field scattering spectroscopy with gold triangular nanoprisms(AuTNPs)as probes.The corners of AuTNPs would be gradually oxidatively etched by the strong coordination of Br•which is generated by enzymatic reactions in the presence of horseradish peroxidase(HRP),bromide ion and trace hydrogen peroxide.Benefitting from the morphological change,the single AuTNP based plasmonic nanoprobe shows notable blueshifts and scattering color changes which could be real-time monitored under the dark-field microscopy.The peak position in the scattering spectra of individual AuTNP blueshifts linearly with the increase of H2O2 concentration,and exhibits high sensitivity to H2O2 in a large range from 2.5 to 100µM with a low detection limit(LOD)of 0.74µM.Moreover,the experimental results were supported by the simulated results via the finite-difference time-domain(FDTD)method.The nanoprobes have been further used for intracellular H2O2 detection in live cells.Besides,the etching of AuTNP also provides an alternative method to design novel plasmonic logic chips and write-once plasmonic memories.

A Water-soluble Conjugated Polymer for Thiol Detection Based on ＂Tu rn-off＂ Effect

We investigated a novel water-soluble conjugated polymer （WSCP） for thiol detection based on ＂turn-off＂ ef- fect. This WSCP was modified with poly（ethylene glycol） （PEG） by disulfide linkages to achieve good solubility in aqueous solution （34 mg/mL） and high quantum yield （0.47）. The separation of water-soluble PEG chains from the conjugated backbone induced by the cleavage of the disulfide linkages would lead to a significant decrease of the water solubility and a dramatical fluorescence quenching of the probe. The combined intuitive images and fluores- cence spectrophotometer further confirmed that decreased solubility produced an aggregation of the hydrophobic conjugated backbone. The fluorescence intensity of the probe showed a good linear relationship with glutathione （GSH） （1-200 nmol·L^-1）, and the detection limit was 16 nmol·L^-1. This WSCP probe was confirmed to be a good sensing material with high selectivity to thiols by testing various biological molecules. And this WSCP probe ex- hibited good detection effect to intracellular thiols by testing Hela cells. Considering the good sensitivity and selec- tivity, the probe could be further used in vivo. In conclusion, this conjugated polymer probe made up for the draw- backs of the micromolecue probes and contributed to the development of new probes based on conjugated poly- mers.

Elucidating the excited-state dynamics behavior in near-infrared Bodipy dye and aggregates toward biophotonics

Photo-induced excited-state dynamics within organic materials fundamentally determine their photophysical properties for various applications,and thus understanding the primary excited-state dynamics behavior is of fundamental and practical significance.Until recently,the excited-state dynamics of organic materials towards biophotonics have been rarely studied,although numerous endeavors have been devoted to the design of organic materials for biophotonics.Herein,various spectroscopy technologies including femtosecond transient absorption(fs-TA)spectroscopy clearly reveal a totally different excited state dynamics behavior within Bodipy monomer(2B-BDP dye)and aggregates(2B-BDP NPs),indicating strongly morphology dependent character.2B-BDP dye undergoes an ultrafast conversion from S1 to intramolecular charge transfer(ICT)state for subsequent photoluminescence(PL)and nonradiative(NR)decay,while 2B-BDP NPs show an accelerated excited-state deactivation mainly through S1→S0 NR decay.The potential bioapplications based on the corresponding excited state dynamics behavior are discussed together with experimental results.Interestingly,the accelerated NR decay in 2B-BDP NPs does not yield a stronger photoacoustic(PA)signal than that in 2B-BDP dye,which violates the conventional wisdom that faster NR decay would benefit the photothermal effects for better photoacoustic imaging(PAI).These insightful and fundamental observations of the excited-state dynamics may contribute an alternative approach at the molecular level towards the future design of functional Bodipy-based organic molecules with desirable performances.

Morphology-Tunable Fluorescent Nanoparticles： Synthesis, Photophysical Properties and Two-Photon Cell Imaging

A novel water-soluble fluorescent amphiphile based on amino polyethylene glycol （PEG-NH2） substituted oligo- （p-phenyleneethynylene） （OPE） was designed and synthesized successfully. Taking anion OPE amphiphile as a comparison, the photophysical features were investigated through ultraviolet absorption （UV） and photolumines- cence （PL） analyses. Due to the hydrophobic-hydrophilic property of the OPE conjugated molecule, self-assembled nanoparticles with the size ranging from 19.6 to 93.5 nm along with the change of morphology from ＂grain＂ to ＂strawberry＂ were conveniently prepared via adjusting concentrations of OPE aqueous solution. Interestingly, after aging for a period of time, homogeneous hollow nanospheres were spontaneously constructed with a diameter of about 200 rim. Cytotoxieity test and cellular uptake behavior of the nanoparticles were further investigated to evalu- ate their potential biomedical applications. Subsequently, the promising applications of two-photon cell imaging were explored using human pancreatic cancer cells （PANC-I cells）, which indicated that the nanoparticles were mainly located within the cell cytoplasm.

NIR-Ⅱprobe modified by poly(L-lysine)with efficient ovalbumin delivery for dendritic cell tracking

Dendritic cell(DC)vaccine is an effective strategy for cancer immunotherapy by carrying antigen into DCs and migrating these DCs to drain lymph nodes after inoculation.In this article,second near-infrared window(NIR-II)fluorescent nanoparticles have been used to uptake antigen and activate DCs.Ovalbumin(OVA),an antigen for immunization,can be loaded on the surface of these NIR-II fluorescent nanoparticles via electrostatic interaction by virtue of their functionalized poly(L-lysine)(PLL),which exhibits biocompatibility and strong selective interaction with OVA.In addition,these antigen-loaded complexes can efficiently be engulfed by immature DCs to induce DC maturation and cytokine secretion.After subcutaneous injection,highly sensitive NIR-II fluorescence signal from nanoparticles indicates that nanoparticle-labeled DCs can successfully migrate into lymph nodes in vivo,showing great promise in immunotherapy against cancer.

NIR-Ⅱ-absorbing conjugated polymer-based theranostic agent for NIR-Ⅱfluorescence imaging-guided photothermal therapy acting synergistically with tumor microenvironment-responsive nitric oxide therapy

Despite tremendous advances in gas therapy,there are major concerns about the inevitable concentration of toxicity and the ability to perform real-time tracking of drug delivery.Second near-infrared(NIR-Ⅱ)window absorbing nanoplatforms hold great promise for precision medicine because of their excellent tissue penetration of light and non-invasive nature.In this study,we engineered an NIR-Ⅱlaser-activated theranostic agent(named CP-bF@PEG)that was composed of amphiphilic polymers(Pluronic F127,with polyethylene glycol,PEG,moieties)coated with an NIR-Ⅱ-absorbing conjugated polymer(PTTBBT,CP)and nitric oxide(NO)donor(benzofuroxan,bF),which served as an NIR-Ⅱphotothermal inducer and NO nanogenerator.Under deep tissue penetration of NIR-Ⅱlaser irradiation,CP-bF@PEG was found to possess fluorescence imaging ability to accurately identify tumor and excellent photothermal effect.Moreover,CP-bF@PEG could generate NO via glutathione activation in the tumor microenvironment in a controllable manner.This NIR-Ⅱ-absorbing polymer for high-contrast NIR-Ⅱfluorescence imaging-guided precision photothermal therapy achieved synergistic effects with NO therapy,as evidenced by pronounced tumor therapeutic efficacy and few side effects.This nanotheranostic agent is a highly promising candidate for high-contrast NIR-Ⅱimaging-guided precision photothermal therapy combined with gas therapy against cancer.