Facile fabrication of organic dyed polymer nanoparticles with aggregation-induced emission using an ultrasound-assisted multicomponent reaction and their biological imaging

Aggregation-induced emission-active micelles: synthesis, characterization, and applications

Aggregation-induced emission (AIE)-active micelles are a type of fluorescent functional materials that exhibit enhanced emissions in the aggregated surfactant state. They have received significant interest due to their excellent fluorescence efficiency in the aggregated state, remarkable processability, and solubility. AIE-active micelles can be designed through the self-assembly of amphipathic AIE luminogens (AIEgens) and the encapsulation of non-emissive amphipathic molecules in AIEgens. Currently, a wide range of AIE-active micelles have been constructed, with a significant increase in research interest in this area. A series of advanced techniques has been used to characterize AIE-active micelles, such as cryogenic-electron microscopy (Cryo-EM) and confocal laser scanning microscopy (CLSM). This review provides an overview of the synthesis, characterization, and applications of AIE-active micelles, especially their applications in cell and in vivo imaging, biological and organic compound sensors, anticancer drugs, gene delivery, chemotherapy, photodynamic therapy, and photocatalytic reactions, with a focus on the most recent developments. Based on the synergistic effect of micelles and AIE, it is anticipated that this review will guide the development of innovative and fascinating AIE-active micelle materials with exciting architectures and functions in the future.

Ultrasound triggered organic mechanoluminescence materials

Ultrasound induced organic mechanoluminescence materials have become one of the focal topics in wireless light sources since they exhibit high spatiotemporal resolution, biocompatibility and excellent tissue penetration depth. These properties promote great potential in ultrahigh sensitive bioimaging with no background noise and noninvasive nanodevices. Recent advances in chemistry, nanotechnology and biomedical research are revolutionizing ultrasound induced organic mechanoluminescence. Herein, we try to summarize some recent researches in ultrasound induced mechanoluminescence that use various materials design strategies based on the molecular conformational changes and cycloreversion reaction. Practical applications, like noninvasive bioimaging and noninvasive optogenetics, are also presented and prospected.

Aggregation-induced emission (AIE) from poly(1,4-dihydropyridine)s synthesized by Hantzsch polymerization and their specific detection of Fe2+ ions

As an important metal element widely existing in nature and the human body, the simple and specific detection of Fe2+ ions has always been of interest.

Synthesis and Characterization of Pyridine-Grafted Copolymers of Acrylic Acid-Styrene Derivatives for Antimicrobial and Fluorescence Applications

The goal of the present study was to copolymerize 3-(4-acetylphenylcarbamoyl) acrylic acid and styrene using azo-bis-isobutyronitrile (AIBN) as a catalyst. The resulting copolymers exhibited number average molecular weights (Mn) of 3.73-5.23 × 104 g/mol with a variable polydispersity (PDI = 2.3-3.8). The amide group of the PMA/PSA polymer was used for grafting poly (-styrene-maleic acid substituted aromatic 2-aminopyridine) by the Hantzsch reaction using a substituted aromatic aldehyde, malononitrile, and ammonium acetate. The polymer can emit strong blue fluorescence (λ = 510 nm) and its thermal stability and solubility were enhanced by polymer grafting. Moreover, the polymer showed the fluorescence spectra of the copolymer had a strong, broad emission band between 300 to 550 nm (maximum wavelength 538 nm) under excitation at 293 nm. The Hantzsch reaction yields an interesting class of nitrogen-based heterocycles that combine with a synthetic strategy for synthesis of grafted co-polymer pyridine-styrene derivatives. The as-prepared pyridine-based polymer compounds were screened against Gram-positive and Gram-negative bacteria, where a maximum inhibition zone toward all four types of bacteria was observed, including specific antifungal activity. Herein, a series of pyridine compounds were synthesized that showed enhanced fluorescent properties and antimicrobial properties due to their unique structure and ability to form polymer assemblies.

Fluorescent nanorods based on 9,10-distyrylanthracene (DSA) derivatives for efficient and long-term bioimaging

Fluorescent nanoparticles based on 9,10-distyrylanthracene (DSA) derivatives (4,4'-((1E,1'E)-anthracene-9,10-diylbis(ethene-2,1-diyl))bis(N,N-dimethylaniline) (NDSA) and 4,4'-((1E,1'E)-anthracene-9,10-diylbis(ethene-2,1-diyl))dibenzonitrile (CNDSA)) were prepared using an ultrasound aided nanoprecipitation method. The morphologies of the fluorescent nanoparticles could be controlled by adjusting the external ultrasonication time. NDSA or CNDSA could form spherical nanodots (NDSA NDs, CNDSA NDs) in a THF-H2O mixture with an 80% or 70% water fraction when the ultrasonication time was 30 s. When the ultrasonication time was prolonged to 10 min, NDSA and CNDSA could assemble into nanorods (NDSA NRs, CNDSA NRs). Meanwhile, the sizes of NDSA NRs and CNDSA NRs could be controlled by adjusting the water content in the mixture. As the water fraction was increased from 60% to 80%, the sizes of NDSA and CNDSA nanorods or nanodots reduced from 238.4 nm to 140.3 nm, and 482 nm to 198.4 nm, respectively. When the water fraction was up to 90%, irregular morphologies of NDSA and CNDSA could be observed. The nanoparticles exhibited intense fluorescence emission, good anti-photobleaching properties, as well as excellent stability and biocompatibility. In vitro cell imaging experiments indicated that the nanorods prepared by this simple method had the potential to be used for efficient and noninvasive long-term bioimaging.

Recent Advances on Fabrication of Polymeric Composites Based on Multicomponent Reactions for Bioimaging and Environmental Pollutant Removal

As the core of polymer chemistry, manufacture of functional polymers is one of research hotspots over the past several decades. Various polymers are developed for diverse applications due to their tunable structures and unique properties. However, traditional step-by-step preparation strategies inevitably involve some problems, such as separation, purification, and time-consuming. The multicomponent reactions (MCRs) are emerging as environmentally benign synthetic strategies to construct multifunctional polymers or composites with pendant groups and designed structures because of their features, such as efficient, fast, green, and atom economy. This mini review summarizes the latest advances about fabrication of multifunctional fluorescent polymers or adsorptive polymeric composites through different MCRs, including Kabachnik-Fields reaction, Biginelli reaction, mercaptoacetic acid locking imine reaction, Debus-Radziszewski reaction, and Mannich reaction. The potential applications of these polymeric composites in biomedical and environmental remediation are also highlighted. It is expected that this mini-review will promote the development preparation and applications of functional polymers through MCRs.

Fabrication of claviform fluorescent polymeric nanomaterials containing disulfide bond through an efficient and facile four-component Ugi reaction

Multicomponent reactions (MCRs) have attracted broad interest for preparation of functional nanomaterials especially for the synthesis of functional polymers. Herein, we utilized an "old" MCR, the four-component Ugi reaction, to synthesize disulfide bond containing poly(PEG-TPE-DTDPA) amphiphilic copolymers with aggregation-induced emission (AIE) feature. This four-component Ugi reaction was carried out under rather mild reaction conditions, such as room temperature, no gas protection and absent of catalysts. The amphiphilic poly(PEG-TPE-DTDPA) copolymers with high number-average molecular weight (up to 86,440 Da) can self-assemble into claviform fluorescent polymeric nanoparticles (FPNs) in aqueous solution, and these water-dispersed nanoparticles exhibited strong emission, large Stokes shift (142 nm), low toxicity and remarkable ability in cellular imaging. Moreover, owing to the introduction of 3,3'-dithiodipropionic acid with disulfide bond, the resultant AIE-active poly(PEG-TPE-DTDPA) could display reduction-responsiveness and be utilized for synthesis of photothermal agents in-situ. Therefore, the AIE-active poly(PEG-TPE-DTDPA) could be promising for controlled intracellular delivery of biological activity molecules and fabrication of multifunctional AIE-active materials. Therefore, these novel AIE-active polymeric nanoparticles could be of great potential for various biomedical applications, such as biological imaging, stimuli-responsive drug delivery and theranostic applications.

Deciphering the Dynamics of Organic Nanoaggregates with AIEE Effect and Excited States: Lipophilic Benzothiadiazole Derivatives as Selective Cell Imaging Probes

An aggregation-induced emission enhancement (AIEE) effect in fluorescent lipophilic 2,1,3-benzothiadiazole (BTD) derivatives and their organic nanoaggregates were studied. A set of techniques such as single-crystal X-ray, dynamic light scattering (DLS), electron paramagnetic resonance (EPR), UV-vis, fluorescence, and density functional theory (DFT) calculations have been used to decipher the formation/break (kinetics), properties, and dynamics of the organic nanoaggregates of three BTD small organic molecules. An in-depth study of the excited-state also revealed the preferential relaxation emissive pathways for the BTD derivatives and the dynamics associated with it. The results described herein, for the first time, explain the formation of fluorescent BTD nanoaggregate derivatives and allow for the understanding of their dynamics in solution as well as the ruling forces of both aggregation and break processes along with the involved equilibrium. One of the developed dyes could be used at a nanomolar concentration to selectively stain lipid droplets emitting an intense and bright fluorescence at the red channel. The other two BTDs could also stain lipid droplets at very low concentrations and were visualized preferentially at the blue channel.

Fluorescence biosensor based on silicon quantum dots and 5,5'-dithiobis-(2-nitrobenzoic acid) for thiols in living cells

An efficient and stable fluorescent sensor is described for the detection and imaging of thiols. It is making use of silicon quantum dots (SiQDs) which can be rapidly prepared. They were characterized by transmission electron microscopy, X-ray power diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry. The SiQDs have an absorption maximum at 300 nm and displayed blue-green fluorescence with excitation/emission maxima at 410/480 nm. A mixture of SiQDs and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) exhibits strong fluorescence emission which however is quenched within 30 s of incubation with thiols. This is assumed to be due to an inner filter effect caused by the reaction of DTNB and thiols. The following thiols were tested: cysteine, homocysteine, and glutathione. The sensor has a linear response in the 3-100 μM thiol concentration range, and the LODs are between 0.80 and 0.96 μM. The sensor displays low cytotoxicity and was applied to fluorescence imaging of MCF-7 cells and Hela cells where it demonstrated excellent biocompatibility.

Double-detecting fluorescent sensor for ATP based on Cu2+ and Zn2+ response of hydrazono-bis-tetraphenylethylene

Although all kinds of sensors with unique detecting ability for one guest were reported, the fluorescence sensor with multiple detecting abilities was seldom presented. This work designed and synthesized a novel AIE fluorescence probe bearing double detecting for ATP based on Cu²⁺ and Zn²⁺ response of hydrazono-bis-tetraphenylethylene (Bis-TPE). Bis-TPE was prepared in 82% yield with simple procedure. It exhibited strong red AIE fluorescence based on the large conjugated electron effect in aqueous media. It showed outstanding selective sensing abilities for Cu²⁺ by strong fluorescence quenching and for Zn²⁺ by red-orange fluorescence change. The sensing mechanism of 1:1 stoichiometric ratios was confirmed by ¹H NMR and MS study. The strong red fluorescence of Bis-TPE + Cu²⁺ system could be recovered by adding ATP. The orange fluorescence of Bis-TPE + Zn²⁺ system could be quenched by adding Cu²⁺ and then was recovered by adding ATP. These double detecting abilities for ATP with the "off-on" red fluorescence in Bis-TPE + Cu²⁺ system and "allochroic-off-on" orange fluorescence in Bis-TPE + Zn²⁺+Cu²⁺ system were successfully applied to test Cu²⁺, Zn²⁺ and ATP in test paper and living cell imaging, displaying the good application prospects for sensing Cu²⁺, Zn²⁺ and double detecting ATP in the complicated environment.

An acrylate AIE-active dye with a two-photon fluorescent switch for fluorescent nanoparticles by RAFT polymerization: synthesis, molecular structure and application in cell imaging

Recently, AIE-active fluorescent materials have attracted extensive investigation due to their significant applications in the fields of memory devices, photomodulation, information displays, sensors, and biological imaging. In this contribution, a novel acrylate AIE-active dye of TPMA was successfully synthesized by Suzuki coupling and acylation reaction, and belongs to the monoclinic crystal system and P21/c space group from the crystal structure analysis, and its fluorescence intensity was stronger with an obvious red shift of emission wavelength as compared with the reported TPB dye. Moreover, the obtained TPMA dye exhibits multi-stimuli-responsivity and a two-photon fluorescent switch with excellent reversibility in the solid state. Subsequently, the corresponding fluorescent polymers of PEG-TM were successfully fabricated via RAFT polymerization of TPMA and PEGMA with a molecular weight of about 25 000 (M n) and narrow polydispersity index (PDI). From 1H NMR analysis, when the feeding ratio of TPMA increased to 32.2% from 19.2%, the molar fraction of TPMA in PEG-TM polymers accordingly increased to 32.8% from 19.5%. In water solution, the as-prepared PEG-TM1 polymers would self-assemble into fluorescent organic nanoparticles (FONs) with diameters ranging from 150 to 250 nm, and their maximum emission wavelength presented at 518 nm with obvious AIE phenomena. Moreover, the as-synthesized PEG-TM polymers have prospective application in biological imaging due to their good fluorescence, high water solubility and excellent biocompatibility.

Biomimetic carbon nanotubes for neurological disease therapeutics as inherent medication

Nowadays, nanotechnology is revolutionizing the approaches to different fields from manufacture to health. Carbon nanotubes (CNTs) as promising candidates in nanomedicine have great potentials in developing novel entities for central nervous system pathologies, due to their excellent physicochemical properties and ability to interface with neurons and neuronal circuits. However, most of the studies mainly focused on the drug delivery and bioimaging applications of CNTs, while neglect their application prospects as therapeutic drugs themselves. At present, the relevant reviews are not available yet. Herein we summarized the latest advances on the biomedical and therapeutic applications of CNTs in vitro and in vivo for neurological diseases treatments as inherent therapeutic drugs. The biological mechanisms of CNTs-mediated bio-medical effects and potential toxicity of CNTs were also intensely discussed. It is expected that CNTs will exploit further neurological applications on disease therapy in the near future.

Advances of Nano-Structured Extended-Release Local Anesthetics

Extended-release local anesthetics (LAs) have drawn increasing attention with their promising role in improving analgesia and reducing adverse events of LAs. Nano-structured carriers such as liposomes and polymersomes optimally meet the demands of/for extended-release, and have been utilized in drug delivery over decades and showed satisfactory results with extended-release. Based on mature technology of liposomes, EXPAREL, the first approved liposomal LA loaded with bupivacaine, has seen its success in an extended-release form. At the same time, polymersomes has advances over liposomes with complementary profiles, which inspires the emergence of hybrid carriers. This article summarized the recent research successes on nano-structured extended-release LAs, of which liposomal and polymeric are mainstream systems. Furthermore, with continual optimization, drug delivery systems carry properties beyond simple transportation, such as specificity and responsiveness. In the near future, we may achieve targeted delivery and controlled-release properties to satisfy various analgesic requirements.

Enzyme-responsive polymeric micelles with fluorescence fabricated through aggregation-induced copolymer self-assembly for anticancer drug delivery

The TPE moiety with AIE is employed as functional hydrophobic chain to induce copolymer self-assembly and form polymeric micelle that can show enzyme-responsive drug delivery.

A novel nucleic acid based bio-assay toward recognition of Haemophilus influenza using bioconjugation and DNA hybridization method

Haemophilus influenza (H. influenza) is a gram negative coccobacillus pathogenic microorganism. H. influenza produces beta-lactamases, and it is also able to modify its penicillin-binding proteins, so it has gained resistance to the penicillin family of antibiotics. In this work, a novel sensitive approach was established for the monitoring of H. influenza using DNA based bio-assay. For the first time, specific sequence of thiolated probe of Haemophilus influenza (SH-5'-AAT TTT CCA ACT TTT TCA CCT GCA T-3') was immobilized on the surface of gold (Au) electrode. Square wave voltammetry (SWV) was carried out in toluidine blue (TB) solution for DNA hybridization and targeting of cDNA sequence of Haemophilus influenza. Field scanning electron microscope (FE-SEM) was applied to investigation of the electrode morphology and estimate of particle size. In the optimal conditions, the planned strategy could detect target DNA (5'-ATG CAG GTG AAA AAG TTG GAA AAT T-3') down to 1 ZM with a linear range from 1 μM to 1 ZM. Moreover, engineered geno-assay selectively differentiates the complementary sequence from target sequences with one, double and three base mismatch sequences.

Paper based immunosensing of ovarian cancer tumor protein CA 125 using novel nano-ink: A new platform for efficient diagnosis of cancer and biomedical analysis using microfluidic paper-based analytical devices (μPAD)

Ovarian cancer is the first and most important cause of malignancy death in women. Mucin 16 or MUC16 protein also known as carcinoma antigen 125 (CA 125) is the most commonly used glycoprotein for early stage diagnosis of ovarian cancer. In this work, a novel paper-based bio-device through hand writing of Ag/RGO (silver nanoparticles/reduced graphene oxide) nano-ink on the flexible paper substrate using pen-on-paper technology was developed. The prepared interface was used to the recognition of CA 125 protein in human biofluid. For this purpose, Ag/rGO nano-ink was synthesized by deposition of Ag nanoparticles onto graphene oxide sheets and the reduction of graphene oxide to rGO simultaneously. Conductivity and resistance of conductive lines were studied after drawing on photographic paper. Subsequently, to prepare a new and unique immuno-device, paper electrode modified by cysteamine caped gold nanoparticles (CysA/Au NPs) using electrochemical techniques. CysA is bonded by sulfur atoms with Au (CysA/Au NPs), and from the amine group with hydroxyl and carboxyl groups of Ag/RGO nano-ink deposited on the surface of paper-based electrodes (CysA/Au NPs/Ag-rGO). Then, anti-CA 125 antibody was immobilized on the electrode surface through Au NPs and CA 125 positively charged amine groups interaction. Atomic force microscopy, Transmission electron microscopy, Field emission scanning electron microscopy, and dynamic light scattering, were performed to identify the engineered immunosensor. Using chronoamperometry technique and under the optimized conditions, the low limit of quantitation (LLOQ) for the proposed immunoassay was recorded as 0.78 U/ml, which this evaluation was performed at highly linear range of 0.78-400 U/ml. The high sensitivity of the electrochemical immunosensor device is indicative of the ability of this immuno-device to detect early stages ovarian cancer.

Trypsin mediated one-pot reaction for the synthesis of red fluorescent gold nanoclusters: Sensing of multiple analytes (carbidopa, dopamine, Cu2+, Co2+ and Hg2+ ions)

Herein, we fabricated fluorescent gold nanoclusters (Au NCs) by using trypsin as a ligand. The fabricated trypsin-Au NCs emit bright red color fluorescence upon the exposure of 365 nm UV light. The trypsin-Au NCs are stable and well dispersed in water, which exhibited strong red emission peak at 665 nm upon excitation wavelength of 520 nm. The red fluorescence of trypsin-Au NCs was greatly quenched by the addition of multiple analytes such as drugs (carbidopa and dopamine) and three divalent metal ions (Cu²⁺, Co²⁺ and Hg²⁺ ion). As a result, a novel fluorescence "turn-off" probe was developed for the detection of the above analytes with good selectivity and sensitivity. This method exhibits the detection limits for carbidopa, dopamine, Cu²⁺, Co²⁺ and Hg²⁺ ions are 6.5, 0.14, 5.2, 0.0078, and 0.005 nM, respectively. The trypsin-Au NCs were successfully applied to detect drugs (carbidopa, and dopamine) in pharmaceutical samples and metal ions (Cu²⁺, Co²⁺ and Hg²⁺ ion) in biofluids and water samples, exhibiting good precision and accuracy, which offers a facile analytical strategy for assaying of the above analytes in pharmaceutical and biological samples.

Tailoring Cell Morphomechanical Perturbations Through Metal Oxide Nanoparticles

The nowadays growing use of nanoparticles (NPs) in commercial products does not match a comprehensive understanding of their potential harmfulness. More in vitro investigations are required to address how the physicochemical properties of NPs guide their engulfment within cells and their intracellular trafficking, fate, and toxicity. These nano-bio interactions have not been extensively addressed yet, especially from a mechanical viewpoint. Cell mechanic is a critical indicator of cell health because it regulates processes like cell migration, tissue integrity, and differentiation via cytoskeleton rearrangements. Here, we investigated in vitro the elasticity perturbation of Caco-2 and A549 cell lines, in terms of Young's modulus modification induced by SiO2NPS and TiO2NPS. TiO2NPs demonstrated stronger effects on cell elasticity compared to SiO2NPs, as they induced significant morphological and morphometric changes in actin network. TiO2NPS increased the elasticity in Caco-2 cells, while opposite effects have been observed on A549 cells. These results demonstrate the existence of a correlation between the alteration of cell elasticity and NPs toxicity that depends, in turn, on the NPs physicochemical properties and the specific cell tested.

Preparation and evaluation of fluorescent poly(p-phenyleneethylene) covalently coated microspheres with reactive sites for bioconjugation

Fluorescent microspheres with reactive sites for interacting with biomolecules are greatly demanded in flow cytometry based suspension array. Aiming to develop a new method for preparing fluorescent microspheres, two poly(p-phenyleneethylene) (PPE) conjugated polymers (CPs) with pedant carboxylic groups were synthesized via Sonogashira coupling and followed with hydrolysis of ester groups; then the conjugated polymers were immobilized onto monodispersed amino-modified porous poly(glycidylmethacrylate) (APGMA) microspheres via coupling reaction between carboxylic and amino groups to give APGMA-CP fluorescent microspheres. The fluorescent microspheres were found to have good photo- and thermal stability as well as negligible influence from rigorous washing. The emission was uniform all across the inner and surface of the spheres. To evaluate the effectiveness of bioconjugation on the fluorescent microspheres, fluorescein isothiocyanate isomer I (FITC) labeled bovine serum albumin (BSA) (BSA-FITC) was chosen as the representative biomolecule to react with the fluorescent microspheres to give APGMA-CP-BSA-FITC. In the flow cytometry study, fluorescence compensation between the V500 and FITC detectors (receiving signals from fluorophores excited by 405 nm and 488 nm, respectively), to remove the interference between the emission of FITC and CPs, was realized using singly-stained microspheres. Finally, APGMA-CP-BSA-FITC microspheres were found to be double positive for CP and FITC with very high percentage (>95%), suggesting the bioconjugation is very effective. This study provides a facile method for simultaneous introduction of fluorescence and reactive sites onto the microspheres, which is very promising to be used as general strategy for fabricating fluorescence microspheres for application in high-throughput technology.

The bioconjugation of DNA with gold nanoparticles towards the spectrophotometric genosensing of pathogenic bacteria

The investigation of important bio-molecular events such as expression of special genes has shown promise with the advent of nanotechnology.

Methyl-restricted rotor rotation on the stator produces high-efficiency fluorescence emission: a new strategy to achieve aggregation-induced emission

At present, we have realized that the aggregation-induced emission (AIE) achieves the purpose of fluorescence enhancement by restricting rotations to reduce intermolecular or intramolecular energy loss. Based on this idea, we synthesized a novel fluorene-based fluorescent compound with a restricted rotor rotation on the stator through the Suzuki coupling reaction. The luminescence effect was evaluated by comparing its fluorescence intensity with that of the control compound. Finally, theoretical calculations showed that the presence of methyl groups hindered the thermal rotation of the fluorenyl groups. Thus, the results indicated that the fluorescence of this compound was better than that of the control compound. A new synthetic pathway for high-efficiency AIE-based fluorescent luminogens has been developed.

At present, we have realized that the aggregation-induced emission (AIE) achieves the purpose of fluorescence enhancement by restricting rotations to reduce intermolecular or intramolecular energy loss.

Tuning the aggregation performance by varying the substituent position: comparative study of neutral bis-urea derivatives in aqueous medium

A set of three neutral bis-urea derivatives has been purposefully chosen to investigate the consequences of positional isomers on the aggregation performance.