Recent Advances in the Development of Highly Luminescent Semiconducting Polymer Dots and Nanoparticles for Biological Imaging and Medicine

Two AIE-active Schiff base fluorescent probes for highly selective recognition of Cu2+ ions

Two helical Schiff base compounds (H4TPA and H4TPE) containing a triphenylamine (TPA) or tetraphenylethylene (TPE) scaffold were successfully synthesized and characterized. Both H4TPA and H4TPE exhibited typical aggregation-induced emission characteristics in the mixed solvent of THF/H2O. The two compounds also showed high selectivity and sensitivity for the recognition of Cu2+ over other ions in THF/HEPES (1:4, V/V, pH = 7.4, 2.0 × 10-5 M), and could be used as turn-off fluorescent probes for Cu2+. The stoichiometric ratios and association constants were estimated via Job's plots and UV-vis spectra titration, and the detection limits of H4TPA and H4TPE toward Cu2+ were calculated to be 2.41 × 10-7 M and 1.38 × 10-7 M, respectively. Besides, the crystal structure of the complex obtained from the interaction of H4TPA with Cu2+ well illustrated the binding modes, which helped us understand the Cu2+ recognition mechanism of H4TPA and H4TPE. Moreover, the detection of Cu2+ and spiked recovery experiments were carried out, which indicated that the two probes can be applied to Cu2+ detection in real samples with satisfactory recoveries.

Processing polymer photocatalysts for photocatalytic hydrogen evolution

Conjugated materials have emerged as competitive photocatalysts for the production of sustainable hydrogen from water over the last decade. Interest in these polymer photocatalysts stems from the relative ease to tune their electronic properties through molecular engineering, and their potentially low cost. However, most polymer photocatalysts have only been utilised in rudimentary suspension-based photocatalytic reactors, which are not scalable as these systems can suffer from significant optical losses and often require constant agitation to maintain the suspension. Here, we will explore research performed to utilise polymeric photocatalysts in more sophisticated systems, such as films or as nanoparticulate suspensions, which can enhance photocatalytic performance or act as a demonstration of how the polymer can be scaled for real-world applications. We will also discuss how the systems were prepared and consider both the benefits and drawbacks of each system before concluding with an outlook on the field of processable polymer photocatalysts.

Ultrabright Dibenzofluoran-Based Polymer Dots with NIR-IIa Emission Maxima and Unusual Large Stokes Shifts for 3D Rotational Stereo Imaging

Emerging organic molecules with emissions in the second near-infrared (NIR-II) region are garnering significant attention. Unfortunately, achieving accountable organic emission intensity over the NIR-IIa (1300 nm) region faces challenges due to the intrinsic energy gap law. Up to the current stage, all reported organic NIR-IIa emitters belong to polymethine-based dyes with small Stokes shifts (<50 nm) and low quantum yield (QY; ≤0.015%). However, such polymethines have proved to cause self-absorption with constrained emission brightness, limiting advanced development in deep-tissue imaging. Here a new NIR-IIa scaffold based on rigid and highly conjugated dibenzofluoran core terminated by amino-containing moieties that reveal emission peaks of 1230-1305 nm is designed. The QY is at least 10 times higher than all synthesized or reported NIR-IIa polymethines with extraordinarily large Stokes shifts of 370-446 nm. DBF-BJ is further prepared as a polymer dot to demonstrate its in vivo 3D stereo imaging of mouse vasculature with a 1400 nm long-pass filter.

Near-Infrared Emissive Super Penetrating Conjugated Polymer Dots for Intratumoral Imaging in 3D Tumor Spheroid Models

This study describes the formation of single-chain polymer dots (Pdots) via ultrasonic emulsification of nonionic donor-acceptor-donor type (D-A-D) alkoxy thiophene-benzobisthiadiazole-based conjugated polymers (Poly BT) with amphiphilic cetyltrimethylammonium bromide (CTAB). The methodology yields Pdots with a high cationic surface charge (+56.5 mV ± 9.5) and average hydrodynamic radius of 12 nm. Optical characterization reveals that these Pdots emit near-infrared (NIR) light at a maximum wavelength of 860 nm owing to their conjugated polymer backbone consisting of D-A-D monomers. Both colloidal and optical properties of these Pdots make them promising fluorescence emissive probes for bioimaging applications. The significant advantage of positively charged Pdots is demonstrated in diffusion-limited mediums such as tissues, utilizing human epithelial breast adenocarcinoma, ATCC HTB-22 (MCF-7), human bone marrow neuroblastoma, ATCC CRL-2266 (SH-SY5Y), and rat adrenal gland pheochromocytoma, CRL-1721 (PC-12) tumor spheroid models. Fluorescence microscopy analysis of tumor spheroids from MCF-7, SH-SY5Y, and PC-12 cell lines reveals the intensity profile of Pdots, confirming extensive penetration into the central regions of the models. Moreover, a comparison with mitochondria staining dye reveals an overlap between the regions stained by Pdots and the dye in all three tumor spheroid models. These results suggest that single-chain D-A-D type Pdots, cationized via CTAB, exhibit long-range mean free path of penetration (≈1 µm) in dense mediums and tumors.

Preparation of seven-coordinated hypervalent tin(IV)-fused azobenzene and applications for stimuli-responsive π-conjugated polymer films

Heavy atoms can form highly coordinated states, and their optical properties have attracted much attention. Recently, we have demonstrated that a reversible coordination-number shift of hypervalent tin(IV) from five to six can provide predictable hypsochromic shifts in light absorption and emission properties in small molecules and a π-conjugated polymer film. Herein, we show the preparation of seven-coordinated tin and reveal that the binding constant of the seven coordination with ethylenediamine (EDA, K = 2900 M-1) is 200 times higher than that of six coordination with propylamine (PA, K = 14 M-1) owing to the chelate effect. Moreover, reversible vapochromism of the π-conjugated polymer film was observed upon exposure (λabs = 598 nm and λPL = 697 nm) and desorption (λabs = 641 nm and λPL = 702 nm) of EDA vapor. Furthermore, as a unique demonstration, the thermochromic film was prepared by fixing the seven coordination as the initial state using 1,10-phenanthroline. These optical variations are predictable by quantum chemical calculations. Our findings are valuable for the development of designable and controllable stimuli-responsive materials focusing on the inherent properties of the elements.

Semiconducting polymer dots for multifunctional integrated nanomedicine carriers

The expansion applications of semiconducting polymer dots (Pdots) among optical nanomaterial field have long posed a challenge for researchers, promoting their intelligent application in multifunctional nano-imaging systems and integrated nanomedicine carriers for diagnosis and treatment. Despite notable progress, several inadequacies still persist in the field of Pdots, including the development of simplified near-infrared (NIR) optical nanoprobes, elucidation of their inherent biological behavior, and integration of information processing and nanotechnology into biomedical applications. This review aims to comprehensively elucidate the current status of Pdots as a classical nanophotonic material by discussing its advantages and limitations in terms of biocompatibility, adaptability to microenvironments in vivo, etc. Multifunctional integration and surface chemistry play crucial roles in realizing the intelligent application of Pdots. Information visualization based on their optical and physicochemical properties is pivotal for achieving detection, sensing, and labeling probes. Therefore, we have refined the underlying mechanisms and constructed multiple comprehensive original mechanism summaries to establish a benchmark. Additionally, we have explored the cross-linking interactions between Pdots and nanomedicine, potential yet complete biological metabolic pathways, future research directions, and innovative solutions for integrating diagnosis and treatment strategies. This review presents the possible expectations and valuable insights for advancing Pdots, specifically from chemical, medical, and photophysical practitioners' standpoints.

Regulating luminescence thermal enhancement in negative thermal expansion metal-organic frameworks

Overcoming thermal quenching is generally essential for the practical application of luminescent materials. It has been recently found that frameworks with negative thermal expansion (NTE) could be a promising candidate to engineer unconventional luminescence thermal enhancement. However, the mechanism through which luminescence thermal enhancement can be well tuned remains an open issue. In this work, enabled by altering ligands in a series of UiO-66 derived Eu-based metal-organic frameworks, it was revealed that the changes in the thermal expansion are closely related to luminescence thermal enhancement. The NTE of the aromatic ring part favors luminescence thermal enhancement, while contraction of the carboxylic acid part plays the opposite role. Modulation of functional groups in ligands can change the thermal vibration of aromatic rings and then achieve luminescence thermal enhancement in a wide temperature window. Our findings pave the way to manipulate the NTE and luminescence thermal enhancement based on ligand engineering.

Nanoparticle-Based Bioaffinity Assays: From the Research Laboratory to the Market

Advances in the development of new biorecognition elements, nanoparticle-based labels as well as instrumentation have inspired the design of new bioaffinity assays. This review critically discusses the potential of nanoparticles to replace current enzymatic or molecular labels in immunoassays and other bioaffinity assays. Successful implementations of nanoparticles in commercial assays and the need for rapid tests incorporating nanoparticles in different roles such as capture support, signal generation elements, and signal amplification systems are highlighted. The limited number of nanoparticles applied in current commercial assays can be explained by challenges associated with the analysis of real samples (e.g., blood, urine, or nasal swabs) that are difficult to resolve, particularly if the same performance can be achieved more easily by conventional labels. Lateral flow assays that are based on the visual detection of the red-colored line formed by colloidal gold are a notable exception, exemplified by SARS-CoV-2 rapid antigen tests that have moved from initial laboratory testing to widespread market adaption in less than two years.

Semiconducting Polymer Dots Directly Stabilized with Serum Albumin: Preparation, Characterization, and Cellular Immunolabeling

Semiconducting polymer dots (Pdots) are brightly fluorescent nanoparticles of growing interest for bioanalysis and imaging. A recurring challenge with these materials is obtaining robust physical and colloidal stability and low nonspecific binding. Here, we prepared and characterized Pdots with bovine serum albumin (BSA) as the stabilizing agent (BSA-Pdots) instead of a more conventionally used amphiphilic polymer, both without and with cross-linking of the protein using glutaraldehyde (BSA(GA)-Pdots) or disuccinimidyl glutarate. Characterization included fluorescence properties; colloidal stability as a function of pH, ionic strength, and solvent perturbation; shape retention and hardness; and nonspecific binding with common assay substrates, fixed cells, and live cells. These properties were contrasted with the same properties for amphiphilic polymer-stabilized Pdots and silica-coated Pdots. On balance, the BSA-stabilized Pdots were similar or more favorable in their properties, with BSA(GA)-Pdots being especially advantageous. Bioconjugation of the BSA-stabilized Pdots was possible using amine-reactive active-ester chemistry, including biotinylation and bioorthogonal functionalization for immunoconjugation via tetrazine-strained-alkene click chemistry. These approaches were used for selective fluorescent labeling of cells based on ligand-receptor and antibody-antigen binding, respectively. Overall, direct BSA stabilization is a very promising strategy for preparing Pdots with improved physical and colloidal stability, reduced nonspecific interactions, and utility for in vitro diagnostics and other bioanalyses and imaging.

Organic Polymer Dots Photocatalyze CO2 Reduction in Aqueous Solution

Developing low-cost and efficient photocatalysts to convert CO2 into valuable fuels is desirable to realize a carbon-neutral society. In this work, we report that polymer dots (Pdots) of poly[(9,9'-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-thiadiazole)] (PFBT), without adding any extra co-catalyst, can photocatalyze reduction of CO2 into CO in aqueous solution, rendering a CO production rate of 57 μmol g-1  h-1 with a detectable selectivity of up to 100 %. After 5 cycles of CO2 re-purging experiments, no distinct decline in CO amount and reaction rate was observed, indicating the promising photocatalytic stability of PFBT Pdots in the photocatalytic CO2 reduction reaction. A mechanistic study reveals that photoexcited PFBT Pdots are reduced by sacrificial donor first, then the reduced PFBT Pdots can bind CO2 and reduce it into CO via their intrinsic active sites. This work highlights the application of organic Pdots for CO2 reduction in aqueous solution, which therefore provides a strategy to develop highly efficient and environmentally friendly nanoparticulate photocatalysts for CO2 reduction.

Incorporation of a Morphologically Controlled Ice Grain Boundary into a Microfluidic Device for Size-Selective Separation of Micro/Nanospheres

A frozen aqueous solution was integrated into a microfluidic device as a size-tunable separation field for the size-selective separation of micro/nanospheres. The width of the ice grain boundaries formed in frozen aqueous solutions could be altered by controlling the operating temperature. A freezing chamber was placed adjacent to the microfluidic channel. A sample-dispersing aqueous sucrose solution was injected into the chamber and frozen, allowing the freeze-concentrated solution (FCS) to run vertically to the microfluidic channel, where the eluting solution flows. The operating temperature can be used to control the physical interaction between the ice wall and micro/nanospheres, enabling size-selective migration. The eluted micro/nanospheres in the microchannel were passed through the eluting solution collected from the outlet. We achieved size-selective separation and collection of microspheres and nanospheres. We separated the exosomes and yeast cells to demonstrate their applicability in bioseparation. The present method is suitable not only for size-selective separation but also for evaluating the biological expression of extracellular vesicles under cryogenic conditions.

Enhanced Photodynamic Therapy by Improved Light Energy Capture Efficiency of Porphyrin Photosensitizers

OPINION STATEMENT

Photodynamic therapy (PDT) has garnered increasing attention in cancer treatment because of its advantages such as minimal invasiveness and selective destruction. With the development of PDT, impressive progress has been made in the preparation of photosensitizers, particularly porphyrin photosensitizers. However, the limited tissue penetration of the activating light wavelengths and relatively low light energy capture efficiency of porphyrin photosensitizers are two major disadvantages in conventional photosensitizers. Therefore, tissue penetration needs to be enhanced and the light energy capture efficiency of porphyrin photosensitizers improved through structural modifications. The indirect excitation of porphyrin photosensitizers using fluorescent donors (fluorescence resonance energy transfer) has been successfully used to address these issues. In this review, the enhancement of the light energy capture efficiency of porphyrins is discussed.

Precise Planar-Twisted Molecular Engineering to Construct Semiconducting Polymers with Balanced Absorption and Quantum Yield for Efficient Phototheranostics

Semiconducting polymers (SPs) have shown great feasibility as candidates for near-infrared-II (NIR-II) fluorescence imaging-navigated photothermal therapy due to their strong light-harvesting ability and flexible tunability. However, the fluorescence signal of traditional SPs tends to quench in their aggregate states owing to the strong π-π stacking, which can lead to the radiative decay pathway shutting down. To address this issue, aggregation-induced emission effect has been used as a rational tactic to boost the aggregate-state fluorescence of NIR-II emitters. In this contribution, we developed a precise molecular engineering tactic based on the block copolymerizations that integrate planar and twisted segments into one conjugated polymer backbone, providing great flexibility in tuning the photophysical properties and photothermal conversion capacity of SPs. Two monomers featured with twisted and planar architectures, respectively, were tactfully incorporated via a ternary copolymerization approach to produce a series of new SPs. The optimal copolymer (SP2) synchronously shows desirable absorption ability and good NIR-II quantum yield on the premise of maintaining typical aggregation-induced emission characteristics, resulting in balanced NIR-II fluorescence brightness and photothermal property. Water-dispersible nanoparticles fabricated from the optimal SP2 show efficient photothermal therapeutic effects both in vitro and in vivo. The in vivo investigation reveals the distinguished NIR-II fluorescence imaging performance of SP2 nanoparticles and their photothermal ablation toward tumor with prominent tumor accumulation ability and excellent biocompatibility.

BODIPY-based near-infrared semiconducting polymer dot for selective yellow laser-excited cell imaging

Semiconducting polymer dots (Pdots) with both narrow-band absorption and emission are desirable for multiplexed bioassay applications, but such Pdots with absorption peaks beyond 400 nm are difficult to achieve. Here we describe a donor-energy transfer unit-acceptor (D-ETU-A) design strategy to produce a BODIPY-based Pdot that exhibits simultaneously narrow absorption and emission bands. A green BODIPY (GBDP) unit was employed as the main building block of the polymer backbone, conferring a strong, narrow-band absorption around 551 nm. An NIR720 acceptor provides narrow-band NIR emission. The small Stokes shift of the GBDP donor allows introduction of a benzofurazan-based ETU, resulting in a ternary Pdot with a fluorescence quantum yield of 23.2%, the most efficient yellow-laser excitable Pdot. Due to the strong absorbance band centered at 551 nm and weak absorbance at 405 nm and 488 nm, the Pdot showed high single-particle brightness when excited by a 561 nm (yellow) laser, and selective yellow laser excitation when used to label MCF cells, with much greater brightness when excited at 561 nm than at 405 nm or 488 nm.

The Role of Stabilizing Copolymer in Determining the Physicochemical Properties of Conjugated Polymer Nanoparticles and Their Nanomedical Applications

Conjugated polymer nanoparticles (CPNs) are a promising class of nanomaterials for biomedical applications, such as bioimaging, gene and drug delivery/release, photodynamic therapy (PDT), photothermal therapy (PTT), and environmental sensing. Over the past decade, many reports have been published detailing their synthesis and their various potential applications, including some very comprehensive reviews of these topics. In contrast, there is a distinct lack of overview of the role the stabilizing copolymer shells have on the properties of CPNs. This review attempts to correct this oversight by scrutinizing reports detailing the synthesis and application of CPNs stabilized with some commonly-used copolymers, namely F127 (Pluronic poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) diacrylate), PSMA (poly(styrene-co-maleic anhydride)), PLGA (poly(D, L-lactide-co-glycolide)) and PEG (polyethylene glycol) derivatives. The analysis of the reported physicochemical properties and biological applications of these CPNs provides insights into the advantages of each group of copolymers for specific applications and offers a set of guidance criteria for the selection of an appropriate copolymer when designing CPNs-based probes. Finally, the challenges and outlooks in the field are highlighted.

Self-Assembly of Selenium-Doped Carbon Quantum Dots as Antioxidants for Hepatic Ischemia-Reperfusion Injury Management

Hepatic ischemia-reperfusion injury (HIRI) is a critical complication after liver surgery that negatively affects surgical outcomes of patients with the end-stage liver-related disease. Reactive oxygen species (ROS) are responsible for the development of ischemia-reperfusion injury and eventually lead to hepatic dysfunction. Selenium-doped carbon quantum dots (Se-CQDs) with an excellent redox-responsive property can effectively scavenge ROS and protect cells from oxidation. However, the accumulation of Se-CQDs in the liver is extremely low. To address this concern, the fabrication of Se-CQDs-lecithin nanoparticles (Se-LEC NPs) is developed through self-assembly mainly driven by the noncovalent interactions. Lecithin acting as the self-assembly building block also makes a pivotal contribution to the therapeutic performance of Se-LEC NPs due to its capability to react with ROS. The fabricated Se-LEC NPs largely accumulate in the liver, effectively scavenge ROS and inhibit the release of inflammatory cytokines, thus exerting beneficial therapeutic efficacy on HIRI. This work may open a new avenue for the design of self-assembled Se-CQDs NPs for the treatment of HIRI and other ROS-related diseases.

High-Precision Mapping of Membrane Proteins on Synaptic Vesicles using Spectrally Encoded Super-Resolution Imaging

The spatial resolution of single-molecule localization microscopy is limited by the photon number of a single switching event because of the difficulty of correlating switching events dispersed in time. Here we overcome this limitation by developing a new class of photoswitching semiconducting polymer dots (Pdots) with structured and highly dispersed single-particle spectra. We imaged the Pdots at the first and the second vibronic emission peaks and used the ratio of peak intensities as a spectral coding. By correlating switching events using the spectral coding and performing 4-9 frame binning, we achieved a 2-3 fold experimental resolution improvement versus conventional superresolution imaging. We applied this method to count and map SV2 and proton ATPase proteins on synaptic vesicles (SVs). The results reveal that these proteins are trafficked and organized with high precision, showing unprecedented level of detail about the composition and structure of SVs.

Rational Design of Asymmetric Polymethines to Attain NIR(II) Bioimaging at >1100 nm

Organic molecules having emission in the NIR(II) region are emergent and receiving enormous attention. Unfortunately, attaining accountable organic emission intensity around the NIR(II) region is hampered by the dominant internal conversion operated by the energy gap law, where the emission energy gap and the associated internal reorganization energy λ_int play key roles. Up to the current stage, the majority of the reported organic NIR(II) emitters belong to those polymethines terminated by two symmetric chromophores. Such a design has proved to have a small λ_int that greatly suppresses the internal conversion. However, the imposition of symmetric chromophores is stringent, limiting further development of organic NIR(II) dyes in diversity and versatility. Here, we propose a new concept where as far as the emissive state of the any asymmetric polymethines contains more or less equally transition density between two terminated chromophores, λ_int can be as small as that of the symmetric polymethines. To prove the concept, we synthesize a series of new polymethines terminated by xanthen-9-yl-benzoic acid and 2,4-diphenylthiopyrylium derivatives, yielding AJBF1112 and AEBF1119 that reveal emission peak wavelength at 1112 and 1119 nm, respectively. The quantum yield is higher than all synthesized symmetric polymethines of 2,4-diphenylthiopyrylium derivatives (SC1162, 1182, 1185, and 1230) in this study. λ_int were calculated to be as small as 6.2 and 7.3 kcal/mol for AJBF1112 and AEBF1119, respectively, proving the concept. AEBF1119 was further prepared as a polymer dot to demonstrate its in vitro specific cellular imaging and in vivo tumor/bone targeting in the NIR(II) region.

Clearance pathways of near-infrared-II contrast agents

Near-infrared-II (NIR-II) bioimaging gradually becomes a vital visualization modality in the real-time investigation for fundamental biological research and clinical applications. The favorable NIR-II contrast agents are vital in NIR-II imaging technology for clinical translation, which demands good optical properties and biocompatibility. Nevertheless, most NIR-II contrast agents cannot be applied to clinical translation due to the acute or chronic toxicity caused by organ retention in vivo imaging. Therefore, it is critical to understand the pharmacokinetic properties and optimize the clearance pathways of NIR-II contrast agents in vivo to minimize toxicity by decreasing organ retention. In this review, the clearance mechanisms of biomaterials, including renal clearance, hepatobiliary clearance, and mononuclear phagocytic system (MPS) clearance, are synthetically discussed. The clearance pathways of NIR-II contrast agents (classified as inorganic, organic, and other complex materials) are highlighted. Successively analyzing each contrast agent barrier, this review guides further development of the clearable and biocompatible NIR-II contrast agents.

Semiconducting polymer dots as fluorescent probes for in vitro biosensing

Semiconducting polymer dots (Pdots) have emerged as novel fluorescent probes with excellent characteristics, such as ultrahigh molar extinction coefficient, easy tunable absorption and emission bands, high brightness, and excellent photostability. Combined with good biocompatibility properties, much effort has been devoted to Pdots for in vivo biological imaging and therapy applications, such as deep-tissue fluorescent imaging, photodynamic therapy, photothermal therapy, and nanocarriers of genes or chemical drugs. Many reviews have been presented in these fields. On the other hand, a large number of studies employing Pdots for in vitro biosensing applications have been reported during the past few years, and there are barely any relevant reports to summarize the progress in this area. Hence, it is necessary to review these studies to promote the comprehensive application of Pdots. Herein, we introduce the properties and functionalization of Pdots, and systematically summarize the progress in the in vitro applications of Pdots, including the detection of DNAs, microRNAs, proteins, enzymatic activity, and some biological small molecules and ions. Finally, we share our perspectives on the future direction of this field.

Nanoparticle-based single molecule fluorescent probes

Single molecule fluorescent probes have attracted considerable attention duet to their ultimate sensitivity, fast response, low sample consumption, and high signal-to-noise ratio. Nanoparticles with outstanding optical properties make them perfect candidates for probes in application of single molecule detection. In this review, we focus on various kinds of nanoparticles acting as single molecule fluorescent probes, including quantum dots, upconverting fluorescent nanoparticles, carbon dots, single-wall carbon nanotubes, fluorescent nanodiamonds, polymeric nanoparticles, nanoclusters, and metallic nanoparticles. Optical properties of various nanoparticles and their recent application in single molecule fluorescent probes are explored. How nanoparticles boost the sensitivity of detection is emphasized in combination with different sensing strategies. Future trends of nanoparticles in single molecule detection are also discussed. We hope this review can provide practical guidance for researchers who work on nanoparticle-based single molecule fluorescent probes.

Dynamic 3D DNA Rolling Walkers via Directional Movement on a Lipid Bilayer Supported by Au@Fe3O4 Nanoparticles for Sensitive Detection of MiRNA-16

Currently reported polyfluorene-based fluorescence detection usually shows high background signal and low detection sensitivity. This work developed a novel three-dimensional (3D) DNA rolling walker via directional movement on a lipid bilayer (LB) supported by Au@Fe₃O₄ nanoparticles (NPs) in a polyfluorene-based fluorescence system so that it could achieve significantly improved detection sensitivity and almost zero-background signal detection for miRNA-16. First, the carboxyl-functionalized poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadazole)] polymer nanoparticles (c-PFBT PNPs) covalently bonded with amino-labeled single-strand CP and further hybridized with single-strand AP to prepare AP-CP-coupled c-PFBT PNP probes. Meanwhile, Au@Fe₃O₄ NPs were developed as efficient fluorescence quenchers and served as the matrix for assembling the LB. The resulting Au@Fe₃O₄@LB assembled cholesterol-labeled orbital DNA L1 and L2 and further assembled hairpins H1 and AP-CP-coupled c-PFBT PNP probes to construct DNA nanomachines. Then, the target miRNA-16 was introduced to initiate the rolling circle amplification (RCA) reaction and form dynamic DNA rolling walkers, thus releasing single-strand CP-coupled c-PFBT PNP probes. The magnetic separation effect of Au@Fe₃O₄ NPs made it possible to detect the fluorescence signal from the released probes, thus achieving almost zero-background signal detection for miRNA-16 with a low detection limit of 95 aM. The flexible interfaces provided by the LB endowed the DNA rolling walkers with high binding efficiency and low derailment probability, thus achieving significantly improved detection sensitivity. The developed strategy provided an attractive polyfluorene-based fluorescence platform with high-sensitivity and low-background signals.

Bifunctional Pdots-Based Novel ECL Nanoprobe with Qualitative and Quantitative Dual Signal Amplification Characteristics for Trace Cytokine Analysis

In this work, a novel methodology to design bifunctional ECL-luminophores with self-enhanced and TSA-amplified characteristics was proposed for improving the sensing performance of ECL-immunosensor toward trace cytokine analysis. Thanks to the qualitative- and quantitative- dual signal amplification technique, the as-prepared ECL biosensor demonstrated excellent detection performance. By analyzing the prospective cytokine biomarkers (IL-6), the ECL immunosensor exhibited a broad examination range with quite low detection limit and quite high selectivity, which was far superior to commercial ELISA kits and ever reported works. In particular, the novel ECL nanoprobe developed here could also be applied to monitor other immune toxicities or disease-related cytokines by using the respective antibodies corresponding to these targets. Moreover, the concept and construction strategy of self-amplified ECL-luminophores presented here could be further extended to design a series of Pdots-derived multicolored ECL probes to meet the needs of multipathway detection applications.

Low-Triggering-Potential Electrochemiluminescence from a Luminol Analogue Functionalized Semiconducting Polymer Dots for Imaging Detection of Blood Glucose

In recent years, semiconducting polymer dots (Pdots) as environmentally friendly and high-brightness electrochemiluminescence (ECL) nanoemitters have attracted intense attention in ECL biosensing and imaging. However, most of the available Pdots have a high ECL excitation potential in the aqueous phase (>1.0 V vs Ag/AgCl), which causes poor selectivity in actual sample detection. Therefore, it is particularly important to construct a simple and universal strategy to lower the trigger potential of Pdots. This work has realized the ECL emission of Pdots at low-trigger-potential based on the electrochemiluminescence resonance energy transfer (ERET) strategy. By covalently coupling the Pdots with a luminol analogue, N-(4-aminobutyl)-N-ethylisoluminol (ABEI), the ABEI-Pdots showed an anodic ECL emission with a low onset potential of +0.34 V and a peak potential at +0.45 V (vs Ag/AgCl), which was the lowest trigger potential reported so far. We further explored this low-triggering-potential ECL for imaging detection of glucose in buffer and serum. By imaging the ABEI-Pdots-modified screen-printed electrodes (SPCE) at +0.45 V for 16 s, the ECL imaging method could quantify the glucose concentration in buffer from 10 to 200 μM with detection limits of 3.3 μM, while exhibiting excellent selectivity. When applied to real serum, the results of our method were highly consistent with a commercial blood glucose meter, with the relative errors ranging from 3.2 to 13%. This work provided a universal strategy for constructing low potential Pdots and demonstrated its application potential in complex biological sample analysis.

A Perspective on Polythiophenes as Conformation Dependent Optical Reporters for Label-Free Bioanalytics

Poly(3-alkylthiophene) (PT)-based conjugated polyelectrolytes (CPEs) constitute an important class of responsive polymers with excellent optical properties. The electrostatic interactions between PTs and target analytes trigger complexation and concomitant conformational changes of the PT backbones that produce distinct optical responses. These conformation-induced optical responses of the PTs enable them to be utilized as reporters for detection of various analytes by employing simple UV-vis spectrophotometry or the naked eye. Numerous PTs with unique pendant groups have been synthesized to tailor their interactions with analytes such as nucleotides, ions, surfactants, proteins, and bacterial and viral pathogens. In this perspective, we discuss PT-target analyte complexation for bioanalytical applications and highlight recent advancements in point-of-care and field deployable assays. Subsequently, we highlight a few areas of critical importance for future applications of PTs as reporters, including (i) design and synthesis of specific PTs to advance the understanding of the mechanisms of interaction with target analytes, (ii) using arrays of PTs and linear discriminant analysis for selective and specific detection of target analytes, (iii) translation of conventional homogeneous solution-based assays into heterogeneous membrane-based assay formats, and finally (iv) the potential of using PT as an alternative to conjugated polymer nanoparticles and dots in bioimaging.

Ultrabright Pdots with a Large Absorbance Cross Section and High Quantum Yield

Semiconducting polymer dots (Pdots) are increasingly used in biomedical applications due to their extreme single-particle brightness, which results from their large absorption cross section (σ). However, the quantum yield (Φ) of Pdots is typically below 40% due to aggregation-induced self-quenching. One approach to reducing self-quenching is to use FRET between the donor (D) and acceptor (A) groups within a Pdot; however, Φ values of FRET-based Pdots remain low. Here, we demonstrate an approach to achieve ultrabright FRET-based Pdots with simultaneously high σ and Φ. The importance of self-quenching was revealed in a non-FRET Pdot: adding 30 mol % of a nonabsorbing polyphenyl to a poly(9,9-dioctylfluorene) (PFO) Pdot increased Φ from 13.4 to 71.2%, yielding an ultrabright blue-emitting Pdot. We optimized the brightness of FRET-based Pdots by exploring different D/A combinations and ratios with PFO and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-phenylene)] (PFP) as donor polymers and poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-(1,4-phenylene)] (PFPV) and poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT) as acceptor polymers, with a fixed concentration of poly(styrene-co-maleic anhydride) as surfactant polymer. Ultrabright blue-emitting Pdots possessing high Φ (73.1%) and σ (σ_R = σ_abs/σ_all, 97.5%) were achieved using PFP/PFPV Pdots at a low acceptor content (A/[D + A], 2.5 mol %). PFP/PFPV Pdots were 1.8 times as bright as PFO/PFPV Pdots due to greater coverage of acceptor absorbance by donor emission─a factor often overlooked in D/A pair selection. Ultrabright green-emitting PFO Pdots (Φ = 76.0%, σ_R = 92.5%) were obtained by selecting an acceptor (PFBT) with greater spectral overlap with PFO. Ultrabright red-emitting Pdots (Φ = 64.2%, σ_R = 91.0%) were achieved by blending PFO, PFBT, and PFTBT to create a cascade FRET Pdot at a D:A₁:A₂ molar ratio of 61:5:1. These blue, green, and red Pdots are among the brightest Pdots reported. This approach of using a small, optimized amount of FRET acceptor polymer with a large donor-acceptor spectral overlap can be generalized to produce ultrabright Pdots with emissions that span the visible spectrum.

Synthesis, characterization, photophysical, lipophilicity, and in vitro fluorescence studies of mono-, di-, and trinuclear Ru(II) polypyridyl complexes of pyridinyl benzimidazole derivatives

The synthesis, characterization, and photophysical properties of mononuclear ruthenium(II) complexes [Ru(bpy)₂(py-BIm-Bz)](ClO₄)₂ (1) and [Ru(phen)₂(py-BIm-Bz)](ClO₄)₂ (2), dinuclear complexes [(bpy)₂Ru-μ₂-(py-BIm-Xy)-Ru(bpy)₂](ClO₄)₄ (3) and [(phen)₂Ru-μ₂-(py-BIm-Xy)-Ru(phen)₂](ClO₄)₄ (4), and trinuclear complexes [((bpy)₂Ru)₃-μ₃-(py-BIm-Ms)](ClO₄)₆ (5) and [((phen)₂Ru)₃-μ₃-(py-BIm-Ms)](ClO₄)₆ (6) of pyridinyl benzimidazole ligands with 2,2'-bipyridine or 1,10-phenanthroline ancillary ligands as fluorescent imaging probes are reported. The ligand py-BIm-Bz crystallizes with inherent disorder due to the competing π-π interactions between two (2-pyridinyl)benzimidazole moieties aligned in parallel and in the opposite direction. The complex 2 forms non-merohedrally twinned crystal with the twin law matrix [0.259 -0.776 0.741, 0.000 -1.000 0.000, 1.259 -0.776 -0.259] and a batch scale factor (BASF) of 0.05. The electronic absorption spectra of the complexes 1-6 differ typically in the π-π* transitions of the ancillary ligands. The complexes exhibit orange-red fluorescence at 624-634 nm at room temperature with quantum yield (0.096 - 0.117) higher than that of [Ru(bpy)₃]²⁺ and a hypsochromic shift of the emission maxima in frozen acetonitrile (λ_em = 613-628 nm) due to the rigidochromic effect. The excited state lifetime of these complexes are in the range 72-194 ns with the mononuclear complexes exhibiting the highest values. The complexes 1-6 are nontoxic (IC₅₀ > 275 μM) toward both HeLa and Vero cell lines. They are hydrophilic and the logP_o/w values are in the -0.53 to -1.46 range. The confocal microscopic study of cellular localization of the complexes on the HeLa cells co-stained with the nuclear staining DAPI dye shows their localization in the cytoplasm and the nuclear membrane penetration increases with nuclearity.

Gadolinium and Polythiophene Functionalized Polyurea Polymer Dots as Fluoro-Magnetic Nanoprobes

A rapid and one-pot synthesis of poly 3-thiopheneacetic acid (PTAA) functionalized polyurea polymer dots (Pdots) using polyethyleneimine and isophorone diisocyanate is reported. The one-pot mini-emulsion polymerization technique yielded Pdots with an average diameter of ~20 nm. The size, shape, and concentration of the surface functional groups could be controlled by altering the synthesis parameters such as ultrasonication time, concentration of the surfactant, and crosslinking agent, and the types of isocyanates utilized for the synthesis. Colloidal properties of Pdots were characterized using dynamic light scattering and zeta potential measurements. The spherical geometry of Pdots was confirmed by scanning electron microscopy. The Pdots were post-functionalized by 1,4,7,10 tetraazacyclododecane-1,4,7,10-tetraacetic acid for chelating gadolinium nanoparticles (Gd³⁺) that provide magnetic properties to the Pdots. Thus, the synthesized Pdots possess fluorescent and magnetic properties, imparted by PTAA and Gd³⁺, respectively. Fluorescence spectroscopy and microscopy revealed that the synthesized dual-functional Gd³⁺-Pdots exhibited detectable fluorescent signals even at lower concentrations. Magnetic levitation experiments indicated that the Gd³⁺-Pdots could be easily manipulated via an external magnetic field. These findings illustrate that the dua- functional Gd³⁺-Pdots could be potentially utilized as fluorescent reporters that can be magnetically manipulated for bioimaging applications.

TADF-based NIR-II semiconducting polymer dots for in vivo 3D bone imaging

Intraoperative fluorescence imaging in the second near-infrared (NIR-II) region heralds a new era in image-guided surgery since the success in the first-in-human liver-tumor surgery guided by NIR-II fluorescence. Limited by the conventional small organic NIR dyes such as FDA-approved indocyanine green with suboptimal NIR-II fluorescence and non-targeting ability, the resulting shallow penetration depth and high false positive diagnostic values have been challenging. Described here is the design of NIR-II emissive semiconducting polymer dots (Pdots) incorporated with thermally activated delayed fluorescence (TADF) moieties to exhibit emission maxima of 1064–1100 nm and fluorescence quantum yields of 0.40–1.58% in aqueous solutions. To further understand how the TADF units affect the molecular packing and the resulting optical properties of Pdots, in-depth and thorough density-functional theory calculations were carried out to better understand the underlying mechanisms. We then applied these Pdots for in vivo 3D bone imaging in mice. This work provides a direction for future designs of NIR-II Pdots and holds promising applications for bone-related diseases.

A series of NIR-II fluorescent TADF-incorporated polymer dots were successfully synthesized. The function of the TADF moiety was fully studied and the bio-applications of these polymer dots including bone imaging were also demonstrated.

Molecular Design of Ultrabright Semiconducting Polymer Dots with High NIR-II Fluorescence for 3D Tumor Mapping

Fluorescence probes emitting in the second near-infrared (NIR-II, 1000-1700 nm) window with the ability for deep-tissue imaging in mammals herald a new era in surgical methodology. However, the brightness of these NIR-II probes is still far from satisfactory due to their low fluorescence quantum yields (QYs), preventing the observation of high-resolution images such as whole-organ vascular networks in real time. Described here is the molecular engineering of a series of semiconducting polymer dots (Pdots) incorporated with aggregation-induced emission moieties to exhibit the QYs as high as 14% in the NIR-II window. Benefiting from the ultrahigh brightness, a 1400 nm long-pass filter is utilized to realize in vivo 3D tumor mapping in mice. To further understand how the geometrical and electron structures of the semiconducting polymers affect their optical properties, the in-depth and thorough density-functional theory calculations are performed to interpret the experimental results. This study lays the groundwork for further molecular design of highly bright NIR-II Pdots.

Polymer Dots with Enhanced Photostability, Quantum Yield, and Two-Photon Cross-Section using Structurally Constrained Deep-Blue Fluorophores

Semiconducting polymer dots (Pdots) have emerged as versatile probes for bioanalysis and imaging at the single-particle level. Despite their utility in multiplexed analysis, deep blue Pdots remain rare due to their need for high-energy excitation and sensitivity to photobleaching. Here, we describe the design of deep blue fluorophores using structural constraints to improve resistance to photobleaching, two-photon absorption cross sections, and fluorescence quantum yields using the hexamethylazatriangulene motif. Scanning tunneling microscopy was used to characterize the electronic structure of these chromophores on the atomic scale as well as their intrinsic stability. The most promising fluorophore was functionalized with a polymerizable acrylate handle and used to give deep-blue fluorescent acrylic polymers with M_n > 18 kDa and Đ < 1.2. Nanoprecipitation with amphiphilic polystyrene-graft-(carboxylate-terminated poly(ethylene glycol)) gave water-soluble Pdots with blue fluorescence, quantum yields of 0.81, and molar absorption coefficients of (4 ± 2) × 10⁸ M^-1 cm^-1. This high brightness facilitated single-particle visualization with dramatically improved signal-to-noise ratio and photobleaching resistance versus an unencapsulated dye. The Pdots were then conjugated with antibodies for immunolabeling of SK-BR3 human breast cancer cells, which were imaged using deep blue fluorescence in both one- and two-photon excitation modes.

Monitoring Metabolites Using an NAD(P)H-sensitive Polymer Dot and a Metabolite-Specific Enzyme

We introduce an NAD(P)H-sensitive polymer dot (Pdot) biosensor for point-of-care monitoring of metabolites. The Pdot is combined with a metabolite-specific NAD(P)H-dependent enzyme that catalyzes the oxidation of the metabolite, generating NAD(P)H. Upon UV illumination, the NAD(P)H quenches the fluorescence emission of Pdot at 627 nm via electron transfer, and also fluoresces at 458 nm, resulting in a shift from red to blue emission at higher NAD(P)H concentrations. Metabolite concentration is quantified ratiometrically-based on the ratio of blue-to-red channel emission intensities, with a digital camera-with high sensitivity and specificity. We demonstrate phenylalanine biosensing in human plasma for a phenylketonuria screening test, quantifying several other disease-related metabolites (lactate, glucose, glutamate, and β-hydroxybutyrate), and a paper-based assay with smartphore imaging for point-of-care use.

Second near-infrared photoactivatable biocompatible polymer nanoparticles for effective in vitro and in vivo cancer theranostics

Photoacoustic imaging (PAI)-guided photothermal therapy (PTT) has drawn considerable attention due to the deeper tissue penetration and higher maximum permissible exposure. However, current phototheranostic agents are greatly restricted by weak absorption in the second near-infrared (NIR-II, 1000-1700 nm) window, long-term toxicity, and poor photostability. In this report, novel organic NIR-II conjugated polymer nanoparticles (CPNs) based on narrow bandgap donor-acceptor BDT-TBZ polymers were developed for effective cancer PAI and PTT. Characterization data confirmed the high photothermal conversion efficiency, good photostability, excellent PAI performance, and superior biocompatibility of as-obtained CPNs. In addition, in vitro and in vivo tests demonstrated the efficient PTT effect of CPNs in ablating cancer cells and inhibiting tumor growth under 1064 nm laser irradiation. More importantly, the CPNs exhibited rapid clearance capability through the biliary pathway and negligible systematic toxicity. Thus, this work provides a novel organic theranostic nanoplatform for NIR-II PAI-guided PTT, which advances the future clinical translation of biocompatible and metabolizable conjugated nanomaterials in cancer diagnosis and therapy.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

Near-Infrared-Emitting Boron-Difluoride-Curcuminoid-Based Polymers Exhibiting Thermally Activated Delayed Fluorescence as Biological Imaging Probes

Near-infrared-emitting polymers were prepared using four boron-difluoride-curcuminoid-based monomers using ring-opening metathesis polymerization (ROMP). Well-defined polymers with molecular weights of ≈20 kDa and dispersities <1.07 were produced and exhibited near-infrared (NIR) emission in solution and in the solid state with photoluminescence quantum yields (Φ_PL ) as high as 0.72 and 0.18, respectively. Time-resolved emission spectroscopy revealed thermally activated delayed fluorescence (TADF) in polymers containing highly planar dopants, whereas room-temperature phosphorescence dominated with twisted species. Density functional theory demonstrated that rotation about the donor-acceptor linker can give rise to TADF, even where none would be expected based on calculations using ground-state geometries. Incorporation of TADF-active materials into water-soluble polymer dots (Pdots) gave NIR-emissive nanoparticles, and conjugation of these Pdots with antibodies enabled immunofluorescent labeling of SK-BR3 human breast-cancer cells.

Development of modified polymer dot as stimuli-sensitive and 67Ga radio-carrier, for investigation of in vitro drug delivery, in vivo imaging and drug release kinetic

A polymer dot modified histidine-functionalized graphene quantum dot carrier, PD@His.GQD, was synthesized to investigate the in vitro sunitinib (STB) deliveryvia luminescence spectrometer. The carrier's synthesis, with an average size of 34 nm, was proved by Fourier transform infrared (FTIR), Transmission Electron Microscopy (TEM), and Dynamic Light Scattering (DLS) analyses. In the in vitro, STB delivery investigation showed that for healthy tissue, the STB was loaded at pH  = 7.2 and at 25  = 5.4 at 37 °C with a maximum loading efficiency percentage of 99 % while it was released at pH = 5.4 at 37 °C with a release percentage of 97 %. In the sequel, the STB loaded carrier was labeled with Gallium-67 (⁶⁷Ga-STB.PD@His.GQD) to produce exceedingly transparent radio-carrier for in vivo kidney cancerous mice imaging via the single photon emission computed tomography (SPECT) device. The radiochemical purity of the ⁶⁷Ga-STB.PD@His.GQD was obtained as 95 % by Radio Thin Layer Chromatography (RTLC) and High-Performance Liquid Chromatography (HPLC) analysis. All obtained results affirmed that the synthesized PD@His.GQD is an STB stimuli-sensitive and selective targeting carrier. All cancerous mice in vivo images at 10 and 20 h of ⁶⁷Ga-STB.PD@His.GQD post-injection and its bio-distribution calculations showed its most accumulation in the kidney cancerous tissue. Also, the STB release kinetic was studied via Zero-order, First-order, Higuchi, and Korsmeyer-Peppas models, and the release data were fitted with Korsmeyer-Peppas model that expresses the STB release mechanism is controlled by diffusion.

Surface Texturing of Polyethylene Terephthalate Induced by Excimer Laser in Silver Nanoparticle Colloids

We report on a novel technique of surface texturing of polyethylene terephthalate (PET) foil in the presence of silver nanoparticles (AgNPs). This approach provides a variable surface morphology of PET evenly decorated with AgNPs. Surface texturing occurred in silver nanoparticle colloids of different concentrations under the action of pulse excimer laser. Surface morphology of PET immobilized with AgNPs was observed by AFM and FEGSEM. Atomic concentration of silver was determined by XPS. A presented concentration-controlled procedure of surface texturing of PET in the presence of silver colloids leads to a highly nanoparticle-enriched polymer surface with a variable morphology and uniform nanoparticle distribution.

High-Throughput Counting and Superresolution Mapping of Tetraspanins on Exosomes Using a Single-Molecule Sensitive Flow Technique and Transistor-like Semiconducting Polymer Dots

A method for high-throughput counting and superresolution mapping of surface proteins on exosomes is described. The method combines a single-molecule sensitive flow technique and an adaptive superresolution imaging method. Exosomes stained with membrane dye and dye-conjugated antibodies were analyzed using a microfluidic platform at a flow rate of 100 exosome s-1 to determine size and protein copy number. Superresolution mapping was performed with exosomes labeled with novel transistor-like, semiconducting polymer dots (Pdots), which exhibit spontaneous blinking with <5 nm localization error and a broad range of optical-adjustable duty cycles. Based on the copy numbers extracted from the flow analysis, the switch-on frequency of the Pdots were finely adjusted so that structures of hundreds of exosomes were obtained within five minutes. The high throughput and high sensitivity of this method offer clear advantages for characterization of exosomes and similar biological vesicles.

Two-photon ratiometric fluorescent probe based on NBD-amine functionalized semiconducting polymer nanoparticles for real-time imaging of hydrogen sulfide in living cells and zebrafish

The thiolysis of 7-nitro-1,2,3-benzoxadiazole amine (NBD-A) paves the way for specific sensing of H₂S over biothiols and real-time imaging in living organisms. Rational fabrication of NBD-A-based probe with ratiometric mode and two-photon excitation is highly appealing to achieve high quality bioimaging. In this work, the NBD-A molecules are assembled with poly(9,9-dioctylfluorenyl-2,7-diyl) polymer nanoparticles, defined as NBD@PFO, to construct two-photon ratiometric probes for H₂S detection through the fluorescence resonance energy transfer (FRET). For the construction of NBD@PFO nanohybrids, polymer nanoparticles are employed as the NBD-A molecular vehicle, energy donor and two-photon absorber, while NBD-A is served as the response unit and energy acceptor. Taking advantages of NBD-A and polymer nanoparticles, the obtained NBD@PFO probes exhibit high selectivity, fast response (<5 s), ratiometric detection and two-photon excitation. Our results indicate that NBD@PFO nanohybrids are successfully applied for monitoring of H₂S concentration in living cells and zebrafish, exhibiting great potential of polymer nanoparticles to improve the imaging capability of an organic small molecular probe.

Efficient and precise delivery of microRNA by photoacoustic force generated from semiconducting polymer-based nanocarriers

One major challenge in miRNA-based therapy is to explore facile delivery strategies, which can facilitate the efficient and precise accumulation of intrinsically instable microRNAs (miRNAs) at targeted tumor sites. To address this critical issue, for the first time we demonstrate that a near-infrared (NIR) pulse laser can guide efficient delivery of miRNAs mediated by a NIR-absorbing and photoacoustic active semiconducting polymer (SP) nanocarrier, which can generate photoacoustic radiation force to intravascularly overcome the endothelial barriers. Importantly, we demonstrate an ultrafast delivery of miRNA (miR-7) to tumor tissues under the irradiation of pulse laser in 20 min, showing a 5-fold boosted efficiency in comparison to the traditional passive targeting strategy. The delivered miR-7 acts as a sensitizer of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and synergizes with TRAIL-inducing compound (TIC), leading to sustained TRAIL upregulation for effective tumor suppression in mice. As such, our results indicate that the NIR-absorbing semiconducting polymer-mediated nanocarrier platform can significantly enhance the targeted delivery efficiency of therapeutic miRNAs to tumors, resulting in potent tumor growth inhibition.

Synthesis and in vitro PDT evaluation of red emission polymer dots (R-CPDs) and pyropheophorbide-α conjugates

Carbon based polymer dots have piqued attention of researchers because of excellent biocompatibility, and good solubility. Most of the p-dots are able to generate ROS which is effective for photodynamic therapy for the treatment of cancer while some photosensitizers such as porphyrins possess some drawbacks such as hydrophobicity, and dark toxicity. Therefore in this study we conjugated red emission carbon based polymer with pyropheophorbide-α through amide condensation and π-π stacking. One pot synthesis of the conjugate was successfully achieved. Their photophysiological properties were studied and structures were characterized by FT-IR, TEM and ¹HNMR. pH- sensitivity of the conjugates was confirmed using fluorescence and UV-vis spectroscopy. Photo toxicity and dark toxicity of the prepared conjugates were evaluated in human esophageal cancer cell line (Eca-109). Hemocompatibility of the synthesized conjugates was evaluated and proved that the conjugates are safe to use for the treatment of tumor. Our results showed the PS doped p-dots had less dark toxicity and increased light toxicity as well as ROS generation was high as compared to precursor drug. Therefore, incorporation of p-dots to porphyrin improved biocompatibility and enhanced the photodynamic effect.