Intrinsic fluorescence hydrogels for ON/OFF screening of antidiabetic drugs: assessing α-glucosidase inhibition by acarbose

Diabetes remains one of the most prevalent chronic diseases globally, significantly impacting mortality ratetables. The development of effective treatments for controlling glucose level in blood is critical to improve the quality of life of patients with diabetes. In this sense, smart optical sensors using hydrogels, responsive to external stimuli, have emerged as a revolutionary approach to diabetes care. In this study, changes in the optical properties of a hydrogel are employed for monitoring α-glucosidase activity, a critical enzyme involved in diabetes mellitus type II due to its role in breaking terminal α-glycosidic bonds, releasing α-glucose. The enzyme is encapsulated within a triazine-based hydrogel that exhibits intrinsic blue fluorescence. Upon hydrolysis of the substrate p-nitrophenyl-α-D-glucopyranoside (p-NPG) by α-glucosidase, the fluorescence is quenched due to the release of p-nitrophenol (PNP). However, when exposed to potential antidiabetic drugs, the enzyme's activity is inhibited, and the hydrogel's fluorescence remains intact. This ON/OFF fluorescence-based assay enables rapid screening of drug candidates by evaluating their ability to inhibit α-glucosidase enzymatic activity. Sensor optimization involves conducting swelling studies, fluorescent assays, reusability tests and a trial with a real antidiabetic drug. This innovative approach holds potential for enhancing antidiabetic drug screening and management, offering a more accessible and efficient solution compared to traditional biosensors.

Fluorescent detection of emerging virus based on nanoparticles: From synthesis to application

The spread of COVID-19 has caused huge economic losses and irreversible social impact. Therefore, to successfully prevent the spread of the virus and solve public health problems, it is urgent to develop detection methods with high sensitivity and accuracy. However, existing detection methods are time-consuming, rely on instruments, and require skilled operators, making rapid detection challenging to implement. Biosensors based on fluorescent nanoparticles have attracted interest in the field of detection because of their advantages, such as high sensitivity, low detection limit, and simple result readout. In this review, we systematically describe the synthesis, intrinsic advantages, and applications of organic dye-doped fluorescent nanoparticles, metal nanoclusters, up-conversion particles, quantum dots, carbon dots, and others for virus detection. Furthermore, future research initiatives are highlighted, including green production of fluorescent nanoparticles with high quantum yield, speedy signal reading by integrating with intelligent information, and error reduction by coupling with numerous fluorescent nanoparticles.

Polymer-Ligated Nanocrystals Enabled by Nonlinear Block Copolymer Nanoreactors: Synthesis, Properties, and Applications

The past several decades have witnessed substantial advances in synthesis and self-assembly of inorganic nanocrystals (NCs) due largely to their size- and shape-dependent properties for use in optics, optoelectronics, catalysis, energy conversion and storage, nanotechnology, and biomedical applications. Among various routes to NCs, the nonlinear block copolymer (BCP) nanoreactor technique has recently emerged as a general yet robust strategy for crafting a rich diversity of NCs of interest with precisely controlled dimensions, compositions, architectures, and surface chemistry. It is notable that nonlinear BCPs are unimolecular micelles, where each block copolymer arm of nonlinear BCP is covalently connected to a central core or polymer backbone. As such, their structures are static and stable, representing a class of functional polymers with complex architecture for directing the synthesis of NCs. In this review, recent progress in synthesizing NCs by capitalizing on two sets of nonlinear BCPs as nanoreactors are discussed. They are star-shaped BCPs for producing 0D spherical nanoparticles, including plain, hollow, and core-shell nanoparticles, and bottlebrush-like BCPs for creating 1D plain and core/shell nanorods (and nanowires) as well as nanotubes. As the surface of these NCs is intimately tethered with the outer blocks of nonlinear BCPs used, they can thus be regarded as polymer-ligated NCs (i.e., hairy NCs). First, the rational design and synthesis of nonlinear BCPs via controlled/living radical polymerizations is introduced. Subsequently, their use as the NC-directing nanoreactors to yield monodisperse nanoparticles and nanorods with judiciously engineered dimensions, compositions, and surface chemistry is examined. Afterward, the intriguing properties of such polymer-ligated NCs, which are found to depend sensitively on their sizes, architectures, and functionalities of surface polymer hairs, are highlighted. Some practical applications of these polymer-ligated NCs for energy conversion and storage and drug delivery are then discussed. Finally, challenges and opportunities in this rapidly evolving field are presented.

Estrogen conjugated fluorescent silica nanoparticles as optical probes for breast cancer cells imaging

Fluorescent nanoparticles are promising tools for living cancer cell imaging and cancer targeting. In this study, estrogen conjugated dye-doped fluorescent nanoparticles (estrogen conjugated FNPs) were synthesized and characterized. The functionalized nanoparticles with low toxicity have shown high selectivity and sensitivity toward target cells. Based on the specific recognition between the estrogen and the estrogen receptor, estrogen conjugated FNPs have been employed as optical probes for specific targeting of estrogen receptor-positive cancer cells with fluorescence microscopy imaging technology. The results demonstrate that the estrogen conjugated FNPs can effectively recognize breast cancer cells with good sensitivity and exceptional photostability, which would offer a novel approach for the diagnosis of breast cancer cells, as well as a new method in detecting estrogen receptors.

Tetraphenylethylene-Induced Cross-Linked Vesicles with Tunable Luminescence and Controllable Stability

Luminescence-tunable vesicles (LTVs) are becoming increasingly attractive for their potential application in optics, electronics, and biomedical technology. However, for real applications, luminous efficiency and durability are two urgent constraints to be overcome. Combining the advantages of aggregation-induced emission in luminous enhancement and cross-linking in stability, we herein fabricated tetraphenylethylene-induced cross-linked vesicles with an entrapped acceptor of RhB (TPE-CVs@RhB), which achieved a high-efficiency multicolor emission of the visible spectrum, including white, by altering the amount of entrapped acceptor. Stability tests show that the luminescence of TPE-CVs@RhB has excellent environmental tolerance toward heating, dilution, doping of organic solvent, and storage in serum. Further outstanding performance in the application of fluorescent inks suggests that the new LTVs hold high potential in industrialization. More attractively, although the TPE-CVs@RhB can tolerate various harsh conditions, their stability can actually be controlled through the cross-linker adopted. For example, the employment of dithiothreitol in the present work produces an acid-labile β-thiopropionate linker. The cellular uptake by HepG2 cells shows that the acid-labile TPE-CVs@RhB can effectively respond to the acidic environment of cancer cells and release the entrapped RhB molecules, indicative of promising applications of this new type of LTVs in bioimaging and drug delivery.

Color-Convertible, Unimolecular, Micelle-Based, Activatable Fluorescent Probe for Tumor-Specific Detection and Imaging In Vitro and In Vivo

Recent years have witnessed significant progress in molecular probes for cancer diagnosis. However, the conventional molecular probes are designed to be "always-on" by attachment of tumor-targeting ligands, which limits their abilities to diagnose tumors universally due to the variations of targeting efficiency and complex environment in different cancers. Here, it is proposed that a color-convertible, activatable probe is responding to a universal tumor microenvironment for tumor-specific diagnosis without targeting ligands. Based on the significant hallmark of up-regulated hydrogen peroxide (H₂ O₂ ) in various tumors, a novel unimolecular micelle constructed by boronate coupling of a hydrophobic hyperbranched poly(fluorene-co-2,1,3-benzothiadiazole) core and many hydrophilic poly(ethylene glycol) arms is built as an H₂ O₂ -activatable fluorescent nanoprobe to delineate tumors from normal tissues through an aggregation-enhanced fluorescence resonance energy transfer strategy. This color-convertible, activatable nanoprobe is obviously blue-fluorescent in various normal cells, but becomes highly green-emissive in various cancer cells. After intravenous injection to tumor-bearing mice, green fluorescent signals are only detected in tumor tissue. These observations are further confirmed by direct in vivo and ex vivo tumor imaging and immunofluorescence analysis. Such a facile and simple methodology without targeting ligands for tumor-specific detection and imaging is worthwhile to further development.

Combining Two-Photon-Activated Fluorescence Resonance Energy Transfer and Near-Infrared Photothermal Effect of Unimolecular Micelles for Enhanced Photodynamic Therapy

Recent years have witnessed significant progress in the field of two-photon-activated photodynamic therapy (2P-PDT). However, the traditional photosensitizer (PS)-based 2P-PDT remains a critical challenge in clinics due to its low two-photon absorption (2PA) cross sections. Here, we propose that the therapeutic activity of current PSs can be enhanced through a combination of two-photon excited fluorescence resonance energy transfer (FRET) strategy and photothermal effect of near-infrared (NIR) light. A core-shell unimolecular micelle with a large two-photon-absorbing conjugated polymer core and thermoresponsive shell was constructed as a high two-photon light-harvesting material. After PSs were grafted onto the surface of a unimolecular micelle, the FRET process from the conjugated core to PSs could be readily switched "on" to kill cancer by the collapsed thermoresponsive shell due to the photothermal effect of NIR light. Such NIR-triggered FRET leads to an enhanced 2PA activity of the traditional PSs and, in turn, amplifies their cytotoxic singlet oxygen generation. Eventually, both in vitro and in vivo PDT efficiencies treated with the thermoresponsive micelles were dramatically enhanced under NIR light irradiation, as compared to pure PSs excited by traditional visible light. Such a facile and simple methodology for the enhancement of the photodynamic antitumor effect holds great promises for cancer therapy with further development.

Functional supramolecular polymers for biomedical applications

As a novel class of dynamic and non-covalent polymers, supramolecular polymers not only display specific structural and physicochemical properties, but also have the ability to undergo reversible changes of structure, shape, and function in response to diverse external stimuli, making them promising candidates for widespread applications ranging from academic research to industrial fields. By an elegant combination of dynamic/reversible structures with exceptional functions, functional supramolecular polymers are attracting increasing attention in various fields. In particular, functional supramolecular polymers offer several unique advantages, including inherent degradable polymer backbones, smart responsiveness to various biological stimuli, and the ease for the incorporation of multiple biofunctionalities (e.g., targeting and bioactivity), thereby showing great potential for a wide range of applications in the biomedical field. In this Review, the trends and representative achievements in the design and synthesis of supramolecular polymers with specific functions are summarized, as well as their wide-ranging biomedical applications such as drug delivery, gene transfection, protein delivery, bio-imaging and diagnosis, tissue engineering, and biomimetic chemistry. These achievements further inspire persistent efforts in an emerging interdisciplin-ary research area of supramolecular chemistry, polymer science, material science, biomedical engineering, and nanotechnology.

Photomodulated fluorescence of supramolecular assemblies of sulfonatocalixarenes and tetraphenylethene

Self-assembled fluorescent nanoparticles responding to specific stimuli are highly appealing for applications such as labels, probes, memory devices, and logic gates. However, organic analogues are challenging to prepare, due to unfavorable aggregation-caused quenching. We herein report the preparation of self-assembled fluorescent organic nanoparticles in water by means of calixarene-induced aggregation of a tetraphenylethene derivative (QA-TPE) mediated by p-sulfonatocalix[4]arenes. The self-assembled nanoparticles showed interesting photoswitching behaviors, and the fluorescence output of the generated nanoparticles was opposite to that of free QA-TPE both before and after irradiation. Free QA-TPE is nonfluorescent, owing to intramolecular rotations of the phenyl rings. In contrast, the self-assembled nanoparticles that formed upon complexation of QA-TPE with p-sulfonatocalix[4]arene exhibited aggregation-induced emission fluorescence (λ(em) = 480 nm, Φ = 14%), as a result of the inhibition of rotations. Upon UV light irradiation, free QA-TPE was cyclized to the corresponding diphenylphenanthrene, which showed typical fluorescence of a π-conjugated system (λ(em) = 385 nm, Φ = 9.3%), whereas the nanoparticles were nonfluorescent upon irradiation due to the aggregation-caused quenching. In effect, this system allows programmed modulation of TPE fluorescence at two different emission wavelengths by means of host-guest complexation and irradiation. Relative to a single-mode stimulus-responsive system, our new developed system of highly integrated modes into a single molecular unit that can exhibit modulation of fluorescence by multiple stimulus is expected to be more adaptable for practical applications and to show enhanced multifunctionality.

Self-assembly of supramolecularly engineered polymers and their biomedical applications

Self-assembly behavior of supramolecularly engineered polymers and their biomedical applications have been summarized.