Folic acid-functionalized mesoporous silica nanospheres hybridized with AIE luminogens for targeted cancer cell imaging

PEI-based functional materials: Fabrication techniques, properties, and biomedical applications

Cationic polymers have recently attracted considerable interest as research breakthroughs for various industrial and biomedical applications. They are particularly interesting due to their highly positive charges, acceptable physicochemical properties, and ability to undergo further modifications, making them attractive candidates for biomedical applications. Polyethyleneimines (PEIs), as the most extensively utilized polymers, are one of the valuable and prominent classes of polycations. Owing to their flexible polymeric chains, broad molecular weight (MW) distribution, and repetitive structural units, their customization for functional composites is more feasible. The specific beneficial attributes of PEIs could be introduced by purposeful functionalization or modification, long service life, biocompatibility, and distinct geometry. Therefore, PEIs have significant potential in biotechnology, medicine, and bioscience. In this review, we present the advances in PEI-based nanomaterials, their transfection efficiency, and their toxicity over the past few years. Furthermore, the potential and suitability of PEIs for various applications are highlighted and discussed in detail. This review aims to inspire readers to investigate innovative approaches for the design and development of next-generation PEI-based nanomaterials possessing cutting-edge functionalities and appealing characteristics.

Reactive oxygen species in biological media are they friend or foe? Major In vivo and In vitro sensing challenges

The role of Reactive Oxygen Species (ROS) on biological media has been shifting over the years, as the knowledge on the complex mechanism that lies in underneath their production and overall results has been growing. It has been known for some time that these species are associated with a number of health conditions. However, they also participate in the immunoactivation cascade process, and can have an active role in theranostics. Macrophages, for example, react to the presence of pathogens through ROS production, potentially allowing the development of new therapeutic strategies. However, their short lifetime and limited spatial distribution of ROS have been limiting factors to the development and understanding of this phenomenon. Even though, ROS have shown successful theranostic applications, e.g., photodynamic therapy, their wide applicability has been hampered by the lack of effective tools for monitoring these processes in real time. Thus the development of innovative sensing strategies for in vivo monitoring of the balance between ROS concentration and the resultant immune response is of the utmost relevance. Such knowledge could lead to major breakthroughs towards the development of more effective treatments for neurodegenerative diseases. Within this review we will present the current understanding on the interaction mechanisms of ROS with biological systems and their overall effect. Additionally, the most promising sensing tools developed so far, for both in vivo and in vitro tracking will be presented along with their main limitations and advantages. This review focuses on the four main ROS that have been studied these are: singlet oxygen species, hydrogen peroxide, hydroxyl radical and superoxide anion.

Mesoporous Silica Nanoparticles as a Potential Nanoplatform: Therapeutic Applications and Considerations

With advances in nanotechnology, nanoparticles have come to be regarded as carriers of therapeutic agents and have been widely studied to overcome various diseases in the biomedical field. Among these particles, mesoporous silica nanoparticles (MSNs) have been investigated as potential nanocarriers to deliver drug molecules to various target sites in the body. This review introduces the physicochemical properties of MSNs and synthesis procedures of MSN-based nanoplatforms. Moreover, we focus on updating biomedical applications of MSNs as a carrier of therapeutic or diagnostic cargo and review clinical trials using silica-nanoparticle-based systems. Herein, on the one hand, we pay attention to the pharmaceutical advantages of MSNs, including nanometer particle size, high surface area, and porous structures, thus enabling efficient delivery of high drug-loading content. On the other hand, we look through biosafety and toxicity issues associated with MSN-based platforms. Based on many reports so far, MSNs have been widely applied to construct tissue engineering platforms as well as treat various diseases, including cancer, by surface functionalization or incorporation of stimuli-responsive components. However, even with the advantageous aspects that MSNs possess, there are still considerations, such as optimizing physicochemical properties or dosage regimens, regarding use of MSNs in clinics. Progress in synthesis procedures and scale-up production as well as a thorough investigation into the biosafety of MSNs would enable design of innovative and safe MSN-based platforms in biomedical fields.

Chitosan coated fluorescent mesoporous silica for the sensitive and selective detection of H2O2

A novel turn-on fluorescent sensor for hydrogen peroxide (H₂O₂) was prepared from chitosan (CS) coating mesoporous silica nanoparticles (MSNs) loaded with 1-(4-Aminophenyl)-1,2,2-triphenylethene (TPE-NH₂) and silver nanoparticles (AgNCs). The surface of MSNs was coated by CS as the gatekeeper and the template for loading of AgNCs. Because of the surface plasmon-enhanced energy transfer (SPEET), AgNCs effectively quenched the fluorescence emission of nanoparticles. In the presence of H₂O₂, AgNCs can be oxidized to Ag⁺, resulting in the recovery of fluorescence. This fluorescent sensor was characterized with respect to its chemical composition, morphological features and optical properties by means of FTIR, XRD, TGA, SEM, TEM, XPS, UV-Vis and fluorescence spectroscopy. The MSN/TPE-CS@Ag nanoparticles showed good sensitivity and selectivity for H₂O₂ even with various interfering ions and agents. Under optimized conditions, the detection limit for H₂O₂ was 0.64 μM in the rage of 1-300 μM. The feasibility of the practical application of this probe was confirmed by accurate quantitative of H₂O₂ in practical samples.

Carbon-Based Nanocomposite Smart Sensors for the Rapid Detection of Mycotoxins

Carbon-based nanomaterials have become the subject of intensive interest because their intriguing physical and chemical properties are different from those of their bulk counterparts, leading to novel applications in smart sensors. Mycotoxins are secondary metabolites with different structures and toxic effects produced by fungi. Mycotoxins have low molecular weights and highly diverse molecular structures, which can induce a spectrum of biological effects in humans and animals even at low concentrations. A tremendous amount of biosensor platforms based on various carbon nanocomposites have been developed for the determination of mycotoxins. Therefore, the contents of this review are based on a balanced combination of our own studies and selected research studies performed by academic groups worldwide. We first address the vital preparation methods of biorecognition unit (antibodies, aptamers, molecularly imprinted polymers)-functionalized carbon-based nanomaterials for sensing mycotoxins. Then, we summarize various types of smart sensors for the detection of mycotoxins. We expect future research on smart sensors to show a significant impact on the detection of mycotoxins in food products.

Recent advances in assembled AIEgens for image-guided anticancer therapy

Image-guided therapy, with simultaneous imaging and therapy functions, has the potential to greatly enhance the therapeutic efficacy of anticancer therapy, and reduce the incidence of side effects. Fluorescence imaging has the advantages of easy operation, abundant signal, high contrast, and fast response for real-time and non-invasive tracking. Luminogens with aggregation-induced emission characteristics (AIEgens) can emit strong luminescence in an aggregate state, which makes them ideal materials to construct applicative fluorophores for fluorescence imaging. The opportunity for image-guided cancer treatment has inspired researchers to explore the theranostic application of AIEgens combined with other therapy methods. In recent years, many AIEgens with efficient photosensitizing or photothermal abilities have been designed by precise molecular engineering, with superior performance in image-guided anticancer therapy. Owing to the hydrophobic property of most AIEgens, an assembly approach has been wildly utilized to construct biocompatible AIEgen-based nanostructures in aqueous systems, which can be used for image-guided anticancer therapy. In the present review, we summarize the recent advances in the assembled AIEgens for image-guided anticancer therapy. Five types of image-guided anticancer therapy using assembled AIEgens are included: chemotherapy, photodynamic therapy, photothermal therapy, gene therapy, and synergistic therapy. Moreover, a brief conclusion with the discussion of current challenges and future perspectives in this area is further presented.

Targeting Cancer Cells Overexpressing Folate Receptors with New Terpolymer-Based Nanocapsules: Toward a Novel Targeted DNA Delivery System for Cancer Therapy

Chemotherapeutics represent the standard treatment for a wide range of cancers. However, these agents also affect healthy cells, thus leading to severe off-target effects. Given the non-selectivity of the commonly used drugs, any increase in the selective tumor tissue uptake would represent a significant improvement in cancer therapy. Recently, the use of gene therapy to completely remove the lesion and avoid the toxicity of chemotherapeutics has become a tendency in oncotherapy. Ideally, the genetic material must be safely transferred from the site of administration to the target cells, without involving healthy tissues. This can be achieved by encapsulating genes into non-viral carriers and modifying their surface with ligands with high selectivity and affinity for a relevant receptor on the target cells. Hence, in this work we evaluate the use of terpolymer-based nanocapsules for the targeted delivery of DNA toward cancer cells. The surface of the nanocapsules is decorated with folic acid to actively target the folate receptors overexpressed on a variety of cancer cells. The nanocapsules demonstrate a good ability of encapsulating and releasing DNA. Moreover, the presence of the targeting moieties on the surface of the nanocapsules favors cell uptake, opening up the possibility of more effective therapies.

Tetraphenylethylene-conjugated polycation covered iron oxide nanoparticles for magnetic resonance/optical dual-mode imaging

Magnetic resonance (MR)/optical dual-mode imaging with high sensitivity and high tissue resolution have attracted many attentions in biomedical applications. To avert aggregation-caused quenching of conventional fluorescence chromophores, an aggregation-induced emission molecule tetraphenylethylene (TPE)-conjugated amphiphilic polyethylenimine (PEI) covered superparamagnetic iron oxide (Alkyl-PEI-LAC-TPE/SPIO nanocomposites) was prepared as an MR/optical dual-mode probe. Alkyl-PEI-LAC-TPE/SPIO nanocomposites exhibited good fluorescence property and presented higher T ₂ relaxivity (352 Fe mM^-1s^-1) than a commercial contrast agent Feridex (120 Fe mM^-1s^-1) at 1.5 T. The alkylation degree of Alkyl-PEI-LAC-TPE effects the restriction of intramolecular rotation process of TPE. Reducing alkane chain grafting ratio aggravated the stack of TPE, increasing the fluorescence lifetime of Alkyl-PEI-LAC-TPE/SPIO nanocomposites. Alkyl-PEI-LAC-TPE/SPIO nanocomposites can effectively labelled HeLa cells and resulted in high fluorescence intensity and excellent MR imaging sensitivity. As an MR/optical imaging probe, Alkyl-PEI-LAC-TPE/SPIO nanocomposites may be used in biomedical imaging for certain applications.

A cationic on–off fluorescent sensor with AIE properties for heparin and protamine detection

In this research, a distyryl-anthracene derivative (DSAI) with two quaternary ammonium groups was synthesized for highly sensitive detection of heparin and protamine.

A novel AIE active NIR fluorophore based triphenylamine for sensing of Hg2+ and CN- and its multiple application

New strategies still need to be proposed that can be used to sense and remove toxic environmental pollutants in a sensing system. In this research, a novel NIR fluorescence sensor 1 was designed and prepared with aggregation induced emission (AIE) property. The fluorescence intensity of the sensor 1 in DMSO/H₂O mixed solvent was changed along with the proportion of water. The sensor 1 can be successfully used for real-time detection and removal of Hg²⁺ in 20% DMSO aqueous solution with high selectivity, quick response and so on. Furthermore it can be efficiently reused and recycled without any loss through Na₂S. In addition, the sensor 1 displayed high sensitivity and selectivity to cyanide ions in 1% DMSO aqueous solution with the presence of other interference anions. The sensing mechanism for Hg²⁺ and cyanide ion was evaluated by ¹H NMR spectra, Mass spectrometry. The sensor 1 exhibited low cytotoxicity for biological applications, which was used as an outstanding fluorescent transducer for detection of cyanide ion in living cells. Based on the visible fluorescence change for the sensor 1 to cyanide ion, the measurement was performed for food materials containing cyanide, such as potato, cassava powder and almond. This research provides perspective potential in solving the problem of other pollution and stimulating new thinking for designing of the novel fluorescence materials.

Encapsulation-Dependent Enhanced Emission of Near-Infrared Nanoparticles Using in vivo Three-Photon Fluorescence Imaging

We discovered a unique fluorescent enhancement of dye encapsulated polymeric nanoparticles, which strongly depended on the polymeric matrix. Interestingly, the polymer nanoparticles containing a NIR emissive dye exhibited remarkable enhancement of emission encapsulated by the polymer amphiphilic polymer containing polystyrene (PS) moiety, whereas the nanoparticles showed weak fluorescence when using other polymer encapsulation. The highest fluorescent quantum yield of nanoparticles can reach 27% by using PS-PEG encapsulation, where the strong NIR fluorescence can be observed. These ultra-bright fluorescence nanoparticles also possess a strong three-photon fluorescence and show a good candidate for in vivo vascular three-photon fluorescence imaging of mouse brain and ear under 1550 nm fs laser excitation. A fine three-dimensional (3D) reconstruction with an imaging depth of 635 and 180 μm was achieved, respectively. We further demonstrate that these nanoparticles can effectively target the sentinel lymph node (SLN) of mice.

AIE nanodots scaffolded by mini-ferritin protein for cellular imaging and photodynamic therapy

Photodynamic therapy (PDT) is one of the most elegant cancer treatment strategies that can be controlled by a beam of light with non-invasion, precise control, and high spatiotemporal accuracy. An ideal photosensitizer (PS) is the key to ensure the efficacy of PDT. Due to their hydrophobic and rigid planar structures, most traditional PSs are prone to aggregate under physiological conditions, which causes fluorescence quenching and significantly reduces reactive oxygen species (ROS) generation. Fortunately, the emergence of aggregation-induced emission (AIE) dyes offers a potential opportunity to overcome these limitations. When AIE PS molecules are in the aggregation state, the fluorescence intensity and ROS production can be increased. We herein use red AIE PS molecules to prepare stable AIE nanodots for cell imaging and PDT via a simple method with a highly negatively charged mini-ferritin protein as the scaffold. The as-prepared protein-AIE nanodots show strong fluorescence emission and efficient singlet oxygen generation, with good stability, relatively long wavelengths of absorption and emission, and negligible dark toxicity. The mini-ferritin-AIE system may be useful in developing novel functional probes for tumour nanotheranostics.

AIE-active fluorescent polymeric nanoparticles about dextran derivative: preparation and bioimaging application

Aggregation-induced emission (AIE), as a special phenomenon of fluorescence, can elegantly overcome the fluorescence quenching caused by common fluorescent materials under high concentration conditions and has attracted interest of researchers in many fields. Particularly AIE-active polymer nanoparticles have been widely utilized in a modern biomedical research. In this work, we prepared a novel kind of AIE-active fluorescent polymeric nanoparticals (Dex-OH-CHO) through a facile esterification between a new hydrophobic AIE-active 1, 8-naphthalimide derivative and the hydrophilic dextran. The structure and optical properties of Dex-OH-CHO were characterized in detail by FTIR, ¹H NMR, XPS, TEM and fluorescence spectra. The results showed that Dex-OH-CHO emitted light-blue fluorescence in aqueous solution with high fluorescent quantum yield (Φ = 24.43%, concentration is 20 μg/mL), low CMC (5 μg/mL), good photostability, high water solubility and well dispersivity. Moreover, good biocompatibility and ideal cell uptake made Dex-OH-CHO had a great application potential in biological imaging.

A Luminescent Amine-Functionalized Metal-Organic Framework Conjugated with Folic Acid as a Targeted Biocompatible pH-Responsive Nanocarrier for Apoptosis Induction in Breast Cancer Cells

Folic acid amine-functionalized metal-organic framework (FOLA@NH₂-Eu:TMU-62) with luminescent properties loaded with 5-fluorouracil (5-Fu), as an anticancer medication, was used to construct a new cancer targeted drug delivery system in the present study. The 5-Fu release from this targeted carrier along with MTT assay and trypan blue dye exclusion test results also exhibited pH-controlled characteristics of the given carrier in acidic environments, which is very suitable for targeting solid tumors. Then, the inhibitory action of 5-Fu-loaded FOLA@NH₂-Eu:TMU-62 for Michigan Cancer Foundation-7 (MCF7) cell migration was explored according to scratch wound healing assays. Based on the results, the FOLA@NH₂-Eu:TMU-62 carrier was not toxic for MCF-10A normal cells, but it was significantly toxic for MCF-7 breast cancer ones, revealing that the FOLA@NH₂-Eu:TMU-62 carrier could be utilized in accurate cancer treatments through apoptotic pathways with higher reactive oxygen species compared with 5-Fu alone. This cancer-targeted design of FOLA@NH₂-Eu:TMU-62 could thus pave the way for synergistic effects of targeting as well as organized release capabilities.

Fluorescent Imidazolium-Type Poly(ionic liquid)s for Bacterial Imaging and Biofilm Inhibition

Fluorescent imidazolium-type poly(ionic liquid)s (PIL)s were synthesized by anion exchange of bromide (Br^-) in poly(3-butyl-1-vinylimidazolium bromide) (PIL-Br) with a fluorescent anion, namely, 3-(4-(1,2,2-triphenylvinyl)phenoxy)propane-1-sulfonate (TPESO₃^-). Such an anion exchange provided antibacterial PILs with aggregation-induced emission (AIE) properties that simultaneously kill and image bacteria. These fluorescence and antibacterial properties could be regulated by controlling the Br^-/TPESO₃^- ratio. The fluorescence intensity increases as this ratio increases, while the antibacterial property exhibits an opposite trend. Moreover, the AIE-type PILs are useful for fluorescently imaging dead bacteria (macroscopically and microscopically) and could effectively inhibit biofilm growth. This study provided a convenient method to obtain fluorescent PILs with adjustable antibacterial and imaging properties.

Engineered borate ester conjugated protein-polymer nanoconjugates for pH-responsive drug delivery

To improve the clinical efficiency of cytotoxic anticancer drugs e.g. doxorubicin (DOX), reduce the severe off-target side effects, and allow the more biocompatible and biodegradable drug penetration into tumor cells, our research efforts developed a new DOX-conjugated protein polymer nanoconjugates (PPNCs) prodrugs delivery system. Briefly, DOX was conjugated to bovine serum albumin (BSA) and the complex was treated with lactobionic acid (LA) as well as folic acid (FA) to enhance drug endocytosis and targeting selectivity. Such functionalized BSA could be conjugated with a designed phenylboronic acid functionalized poly(N-isopropylacrylamide) (PNIPAAm) via forming a pH-sensitive borate ester bond to give the functionalized PPNCs prodrugs. The potential of the PPNCs prodrugs on tumor cells therapy was systematically evaluated in dose/time-dependent effects. In vitro results showed a rapid accumulation of the prodrugs into the MDA-MB-231 tumor cell during the first 30 min and reached maximum at 24 h. Moreover, the cell-killing effect was observed quickly after 4 h incubation with an IC50 of 0.5 mg/mL (≈4 μM/L). In general, given the efficient pH-dependent DOX release of these constructed nanoconjugates, it is anticipated to contribute a potential delivery strategy for cancer therapy.

A new approach to developing diagnostics and therapeutics: Aggregation-induced emission-based fluorescence turn-on

Fluorescence imaging is a promising visualization tool and possesses the advantages of in situ response and facile operation; thus, it is widely exploited for bioassays. However, traditional fluorophores suffer from concentration limits because they are always quenched when they aggregate, which impedes applications, especially for trace analysis and real-time monitoring. Recently, novel molecules with aggregation-induced emission (AIE) characteristics were developed to solve the problems encountered when using traditional organic dyes, because these new molecules exhibit weak or even no fluorescence when they are in free movement states but emit intensely upon the restriction of intramolecular motions. Inspired by the excellent performances of AIE molecules, a substantial number of AIE-based probes have been designed, synthesized, and applied to various fields to fulfill diverse detection tasks. According to numerous experiments, AIE probes are more practical than traditional fluorescent probes, especially when used in bioassays. To bridge bioimaging and materials engineering, this review provides a comprehensive understanding of the development of AIE bioprobes. It begins with a summary of mechanisms of the AIE phenomenon. Then, the strategies to realize accurate detection using AIE probes are discussed. In addition, typical examples of AIE-active materials applied in diagnosis, treatment, and nanocarrier tracking are presented. In addition, some challenges are put forward to inspire more ideas in the promising field of AIE-active materials.

AIEgen based poly(L-lactic-co-glycolic acid) magnetic nanoparticles to localize cytokine VEGF for early cancer diagnosis and photothermal therapy

Aim: We demonstrated a novel theranostic system for simultaneous photothermal therapy and magnetic resonance imaging applicable to early diagnostics and treatment of cancer cells. Materials & methods: Oleic acid-Fe3O4 and triphenylamine-divinylanthracene-dicyano were loaded to the poly(L-lactic-co-glycolic acid) nanoparticles (NPs) on which anti-VEGF antibodies were modified to form anti-VEGF/OA-Fe3O4/triphenylamine-divinylanthracene-dicyano@poly(L-lactic-co-glycolic acid) NPs. The 1H nuclear magnetic resonance (NMR), mass spectra, fluorescence, UV absorption, dynamic light scattering, transmission electron microscope and inductively coupled plasma mass spectrometry tests were used to characterize the NPs, and the bioimaging was illustrated by confocal laser scanning microscope (CLSM) and in vivo MRI animal experiment. Results: This system was capable to recognize the overexpressed VEGF-A as low as 68 pg/ml in different cell lines with good selectivity and photothermal therapy effect. Conclusion: These ultrasensitive theranostic NPs were able to identify tumor cells by fluorescence imaging and MRI, and destroy tumors under near infrared illumination.

Polymeric Engineering of Nanoparticles for Highly Efficient Multifunctional Drug Delivery Systems

Most targeting strategies of anticancer drug delivery systems (DDSs) rely on the surface functionalization of nanocarriers with specific ligands, which trigger the internalization in cancer cells via receptor-mediated endocytosis. The endocytosis implies the entrapment of DDSs in acidic vesicles (endosomes and lysosomes) and their eventual ejection by exocytosis. This process, intrinsic to eukaryotic cells, is one of the main drawbacks of DDSs because it reduces the drug bioavailability in the intracellular environment. The escape of DDSs from the acidic vesicles is, therefore, crucial to enhance the therapeutic performance at low drug dose. To this end, we developed a multifunctionalized DDS that combines high specificity towards cancer cells with endosomal escape capabilities. Doxorubicin-loaded mesoporous silica nanoparticles were functionalized with polyethylenimine, a polymer commonly used to induce endosomal rupture, and hyaluronic acid, which binds to CD44 receptors, overexpressed in cancer cells. We show irrefutable proof that the developed DDS can escape the endosomal pathway upon polymeric functionalization. Interestingly, the combination of the two polymers resulted in higher endosomal escape efficiency than the polyethylenimine coating alone. Hyaluronic acid additionally provides the system with cancer targeting capability and enzymatically controlled drug release. Thanks to this multifunctionality, the engineered DDS had cytotoxicity comparable to the pure drug whilst displaying high specificity towards cancer cells. The polymeric engineering here developed enhances the performance of DDS at low drug dose, holding great potential for anticancer therapeutic applications.

Multifunctional Gd-based mesoporous silica nanotheranostic for anticancer drug delivery

A theranostic MRI nanoprobe based on mesoporous silica nanoparticles with attached stable Gd-complexes with high relaxivity, rhodamine dyes, PEG and cyclooctyne moieties was synthesized and loaded with mitoxantrone for bio-orthogonal targeted anticancer drug delivery.

A facile surface modification strategy for fabrication of fluorescent silica nanoparticles with the aggregation-induced emission dye through surface-initiated cationic ring opening polymerization

Fluorescent silica nanoparticles (FSNPs) have attracted great interest for potential applications in biological and biomedical fields because they possess higher fluorescence quantum yield and better fluorescence stability as comparison with small organic fluorescent molecules. The encapsulation of covalent linkage with fluorescent organic dyes or fluorescent metal complexes has demonstrated to be the commonly adopted strategies for fabrication of FSNPs previously. However, it is still challengeable to obtain FSNPs based polymer composites with intensive fluorescence and good water dispersibility through a one-pot surface modification strategy. In this paper, we developed a facile method to fabricate novel FSNPs based polymer composites (PhE@MSNs-PEtOx) through introducing the aggregation-induced emission (AIE) dye (PhE-OH) and poly(2-ethyl-2-oxazoline) (PEtOx) onto mesoporous silica nanoparticles (MSNs) based on cationic ring opening polymerization (CROP). The resulting PhE@MSNs-PEtOx composites possess strong fluorescence emission, excellent hydrophilicity and biocompatibility. These features make the final FSNPs based polymer composites great potential for biomedical applications. Taken together, we have developed for the first time that FSNPs based polymer composites can be facilely prepared through the one-pot introduction of AIE dyes and hydrophilic PEtOx on MSNs. Moreover, the novel FSNPs based composites could also be utilized for other biomedical applications considered their properties.

Delivery of a TNF-α-derived peptide by nanoparticles enhances its antitumor activity by inducing cell-cycle arrest and caspase-dependent apoptosis

Prostate cancer is the second-most common malignancy of the male genitourinary system. TNF-α has attracted intense attention as a potential therapeutic agent against various cancers. However, its therapeutic application is restricted by short half life and severe toxic side-effects. In this study, we constructed a stable nanodrug, called TNF-α-derived polypeptide (P16)-conjugated, chitosan (CTS)-modified selenium nanoparticle (SC; SCP), which is composed of SC as a slow-release carrier conjugated to P16. SCP had significant inhibitory effects on multiple types of tumor cells, especially DU145 prostate cancer cells, but not on RWPE-1 normal human prostate epithelial cells. SCP could induce G0/G1 cell-cycle arrest and apoptosis in DU145 cells more effectively than could P16 and TNF-α. In DU145 xenograft tumor models, SCP exerted much stronger antitumor effects than P16 or estramustine (the clinical drug for prostate cancer) but caused fewer toxic side-effects. In addition, SCP significantly inhibited proliferation and accelerated apoptosis in DU145 xenograft tumors. Further mechanistic studies revealed that SCP exerted antitumor effects via activation of the p38 MAPK/JNK pathway, thus inducing G0/G1 cell-cycle arrest and caspase-dependent apoptosis. These findings suggest that SCP may represent a potential long-lasting therapeutic agent for human prostate cancer with fewer side effects.-Yan, Q., Chen, X., Gong, H., Qiu, P., Xiao, X., Dang, S., Hong, A., Ma, Y. Delivery of a TNF-α-derived peptide by nanoparticles enhances its antitumor activity by inducing cell-cycle arrest and caspase-dependent apoptosis.

Organic Dye Based Nanoparticles for Cancer Phototheranostics

Phototheranostics, which simultaneously combines photodynamic and/or photothermal therapy with deep-tissue diagnostic imaging, is a promising strategy for the diagnosis and treatment of cancers. Organic dyes with the merits of strong near-infrared absorbance, high photo-to-radical and/or photothermal conversion efficiency, great biocompatibility, ready chemical structure fine-tuning capability, and easy metabolism, have been demonstrated as attractive candidates for clinical phototheranostics. These organic dyes can be further designed and fabricated into nanoparticles (NPs) using various strategies. Compared to free molecules, these NPs can be equipped with multiple synergistic functions and show longer lifetime in blood circulation and passive tumor-targeting property via the enhanced permeability and retention effect. In this article, the recent progress of organic dye-based NPs for cancer phototheranostic applications is summarized, which extends the anticancer arsenal and holds promise for clinical uses in the near future.

Fluorescence resonance energy transfer (FRET) based nanoparticles composed of AIE luminogens and NIR dyes with enhanced three-photon near-infrared emission for in vivo brain angiography

Near-infrared (NIR) fluorescence is very important for high-contrast biological imaging of high-scattering tissues such as brain tissue. Unfortunately, commercial NIR dyes are excited usually by visible light, and their multi-photon absorption (MPA) cross-sections are small. Here, we design new co-encapsulated NIR nanoparticles (NPs) with a large three-photon (3PA) absorption cross-section. A form of aggregation-induced emission (AIE) luminogen (AIEgen), 2,3-bis(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl) fumaronitrile (TPATCN), is introduced as the donor, and a form of NIR dye, silicon 2,3-naphthalocyanine bis-(trihexylsilyloxide) (NIR775), is adopted as the acceptor. Under the excitation of a 1550 nm fs laser, TPATCN-NIR775 NPs demonstrated a bright three-photon fluorescence centered at 785 nm. The energy transfer efficiency of the TPATCN-NIR775 NPs was calculated to be as high as 90%, which could be attributed to the good spectral overlap between the emission of TPATCN and the absorption of NIR775. By injection with TPATCN-NIR775 NPs, a vivid 3D reconstruction of mouse brain vasculature was obtained with even small blood vessels clearly visualized. The design strategy used for the co-encapsulated AIE-NIR NPs would be helpful in synthesizing more NIR probes for deep-tissue biological imaging in the future.

Brighter, More Stable, and Less Toxic: A Host-Guest Interaction-Aided Strategy for Fabricating Fluorescent Silica Nanoparticles and Applying Them in Bioimaging and Biosensing at the Cellular Level

The exploration of fluorescent tools with distinguished optical properties and favorable biocompatibility is significant for biosensing and bioimaging. We herein present a host-guest interactions aided strategy for fabricating fluorescent silica nanoparticles (FSNPs), which is enabled by cyclodextrin (CD) supermolecules. Compared with conventional FSNPs, the modified products (are named as fluorophore@CD@SNPs) possess several advantages. First, the incorporated fluorophores can thoroughly get rid of their intrinsic aggregation due to CD's inclusion effect, and the fluorescence intensity of the obtained fluorophore@CD@SNPs can enhance 48-67%. The fluorophores can then be well-fixed by the host CD molecules. As a result, the leak rates of the incorporated fluorophores are only 15-17%, which is about 3 times lower than that of conventional ones (42-48%). Notably, the as-prepared fluorophore@CD@SNPs show observable less cytotoxicity as compared with their conventional counterparts, probably due to the substantially decreased leakage of the incorporated fluorophores. Because of prominent properties and versatile fabrication, the proposed fluorophore@CD@SNPs not only possess better performances for cell-imaging but are competent for ratiometric sensing of pH value at living cell using (indicator-reference) integrative silica NPs.

Progress and Trends in AIE-Based Bioprobes: A Brief Overview

Luminescent bioprobes are powerful analytical means for biosensing and optical imaging. Luminogens featured with aggregation-induced emission (AIE) attributes have emerged as ideal building blocks for high-performance bioprobes. Bioprobes constructed with AIE luminogens have been identified to be a novel class of FL light-up probing tools. In contrast to conventional bioprobes based on the luminophores with aggregation-caused quenching (ACQ) effect, the AIE-based bioprobes enjoy diverse superiorities, such as lower background, higher signal-to-noise ratio and sensitivity, better accuracy, and more outstanding resistance to photobleaching. AIE-based bioprobes have been tailored for a vast variety of purposes ranging from biospecies sensing to bioimaging to theranostics (i.e., image-guided therapies). In this review, recent five years' advances in AIE-based bioprobes are briefly overviewed in a perspective distinct from other reviews, focusing on the most appealing trends and progresses in this flourishing research field. There are altogether 11 trends outlined, which have been classified into four aspects: the probe composition and form (bioconjugtes, nanoprobes), the output signal of probe (far-red/near-infrared luminescence, two/three-photon excited fluorescence, phosphorescence), the modality and functionality of probing system (dual-modality, dual/multifunctionality), the probing object and application outlet (specific organelles, cancer cells, bacteria, real samples). Typical examples of each trend are presented and specifically demonstrated. Some important prospects and challenges are pointed out as well in the hope of intriguing more interests from researchers working in diverse areas into this exciting research field.

"Turn-on" Fluorescent Aptasensor Based on AIEgen Labeling for the Localization of IFN-γ in Live Cells

We report an aggregation-induced emission fluorogen (AIEgen)-based turn-on fluorescent aptasensor able to detect the ultrasmall concentration of intracellular IFN-γ. The aptasensor consists of an IFN-γ aptamer labeled with a fluorogen with a typical aggregation-induced emission (AIE) characteristic, which shows strong red emission only in the presence of IFN-γ. The aptasensor is able to effectively monitor intracellular IFN-γ secretion with the lowest detection limit of 2 pg mL^-1, and it is capable of localizing IFN-γ in live cells during secretion, with excellent cellular permeability and biocompatibility as well as low cytotoxicity. This probe is able to localize the intracellular IFN-γ at a low concentration <10 pg mL^-1, and it is successfully used for real-time bioimaging. This simple and highly sensitive sensor may enable the exploration of cytokine pathways and their dynamic secretion process in the cellular environment. It provides a universal sensing platform for monitoring a spectrum of molecules secreted by cells.

AIEgen-Based Fluorescent Nanomaterials: Fabrication and Biological Applications

In recent years, luminogens with the feature of aggregation-induced emission (AIEgen) have emerged as advanced luminescent materials for fluorescent nanomaterial preparation. AIEgen-based nanomaterials show enhanced fluorescence efficiency and superior photostability, which thusly offer unique advantages in biological applications. In this review, we will summarize the fabrication methods of AIEgen-based nanomaterials and their applications in in vitro/in vivo imaging, cell tracing, photodynamic therapy and drug delivery, focusing on the recent progress.

Folic acid-functionalized graphene quantum dots with tunable fluorescence emission for cancer cell imaging and optical detection of Hg2+

Functional groups may alter the optical and electrical characteristics of graphene quantum dots and lead to unusual properties and related applications.

Progress in Nanotheranostics Based on Mesoporous Silica Nanomaterial Platforms

Theranostics based on nanoparticles (NPs) is a promising paradigm in nanomedicine. Mesoporous silica nanoparticle (MSN)-based systems offer unique characteristics to enable multimodal imaging or simultaneous diagnosis and therapy. They include large surface area and volume, tunable pore size, functionalizable surface, and acceptable biological safety. Hybridization with other NPs and chemical modification can further potentiate the multifunctionality of MSN-based systems toward translation. Here, we update the recent progress on MSN-based systems for theranostic purposes. We discuss various synthetic approaches used to construct the theranostic platforms either via intrinsic chemistry or extrinsic combination. These include defect generation in the silica structure, encapsulation of diagnostic NPs within silica, their assembly on the silica surface, and direct conjugation of dye chemicals. Collectively, in vitro and in vivo results demonstrate that multimodal imaging capacities can be integrated with the therapeutic functions of these MSN systems for therapy. With further improvement in bioimaging sensitivity and targeting specificity, the multifunctional MSN-based theranostic systems will find many clinical applications in the near future.

Supramolecular complexes formed by dimethoxypillar[5]arenes and imidazolium salts: a joint experimental and computational investigation

The stability of host–guest complexes formed by dimethoxypillar[5]arenes and imidazolium salts has been analyzed as a function of different structural features of the guest, using a combined approach of different techniques.

Silica nanoparticles based on an AIE-active molecule for ratiometric detection of RNS in vitro

Silica nanoparticles based on an AIE-active molecule were prepared for ratiometric detection of reactive nitrogen species (RNS) in vitro.

Construction and function of a highly efficient supramolecular luminescent system

Aggregation-induced emission (AIE) provides a new way of achieving highly efficient luminescent materials. In this contribution, the self-assembly behavior, molecular stacking structure and photophysical properties of two polymorphs of a supramolecular co-crystal (C1 and C2) are investigated. The block-like crystal C1, packed in segregated stacking with strong π–π interactions between the H and G molecules, shows weak green emission with a low efficiency (Φ_F) of 2%. In comparison, the needle-like crystal C2, packed in segregated stacking with no obviously strong intermolecular interactions, shows bright yellow emission. More importantly, C1 exhibits mechanochromic behavior.

E/Z isomerization effects on aggregation-enhanced emission of tetraphenylethene derivatives assisted by host–guest recognition

Pure E and Z stereoisomers of tetraphenylethene derivatives functionalized with dibenzylamine groups were isolated. Both supramolecular polymerization and photophysical changes were more significant in the case of the former than in the latter.

Tunable Supramolecular Interactions of Aggregation-Induced Emission Probe and Graphene Oxide with Biomolecules: An Approach toward Ultrasensitive Label-Free and "Turn-On" DNA Sensing

Aggregation-induced emission (AIE) probes have shown great potential applications in fluorescent sensing of biomolecules, and the integration of AIE probe and graphene oxide (GO) attracts intense interest in developing new tools for label-free and "turn-on" fluorescent biomolecular analysis. Herein, an ultrasensitive label-free and "turn-on" DNA sensing is realized by tuning the supramolecular interactions of AIE probe and GO with DNA. The investigation of supramolecular interactions of AIE probes and GO with DNA demonstrate that AIE probe with short alkyl chains substitute shows highest binding affinity with DNA strand, and GO with low oxidation degree possesses strong binding interactions to ssDNA and the highest fluorescence quenching efficiency. As a result, the optimized AIE probes and GO-based fluorescent sensor can selectively detect the target DNA sequence and exhibits the detection limitation as low as 0.17 × 10^-9 m. It is believed that the research efforts will provide an efficient approach to improve the performance of DNA sensing assay and an indepth understanding of the supramolecular interactions of AIE probes and GO with DNA, and thus facilitate their extended applications in biosensors and biomedicine.

AIEgens-Functionalized Inorganic-Organic Hybrid Materials: Fabrications and Applications

Inorganic materials functionalized with organic fluorescent molecules combine advantages of them both, showing potential applications in biomedicine, chemosensors, light-emitting, and so on. However, when more traditional organic dyes are doped into the inorganic materials, the emission of resulting hybrid materials may be quenched, which is not conducive to the efficiency and sensitivity of detection. In contrast to the aggregation-caused quenching (ACQ) system, the aggregation-induced emission luminogens (AIEgens) with high solid quantum efficiency, offer new potential for developing highly efficient inorganic-organic hybrid luminescent materials. So far, many AIEgens have been incorporated into inorganic materials through either physical doping caused by aggregation induced emission (AIE) or chemical bonding (e.g., covalent bonding, ionic bonding, and coordination bonding) caused by bonding induced emission (BIE) strategy. The hybrid materials exhibit excellent photoactive properties due to the intramolecular motion of AIEgens is restricted by inorganic matrix. Recent advances in the fabrication of AIEgens-functionalized inorganic-organic hybrid materials and their applications in biomedicine, chemical sensing, and solid-state light emitting are presented.

A Silver(I)-Estrogen Nanocluster: GSH Sensitivity and Targeting Suppression on HepG2 Cell

A structure-determined silver nanocluster of [Ag₁₀ (Eth)₄ (CF₃ COO)₆ (CH₃ OH)₃ ]·3C-H₃ OH (Eth = ethisterone) (1), is firstly demonstrated by self-assembly of silver salt and ethisterone. Due to the thiophilicity of silver(I) ions, complex 1 shows reactivity with glutathione (GSH) molecules in solution and induces the fluorescence quenching behavior. Thus, complex 1 can be used as a fluorescent sensor for GSH. In consideration of the higher level of GSH in cancerous cells, complex 1 presents significant tumor suppression reactivity toward the human hepatocellular carcinoma (HepG2) cells with IC₅₀ value of 165 × 10^-9 m. Especially, complex 1 displays 3.4-fold higher in vitro cytotoxicity to HepG2 cells than that of the normal CCC-HEL-1 cells, which makes complex 1 a potential targeting suppression agent for cancerous cells. The molecular design of complex 1 not only generates a new medicine-silver(I) cluster family, but also opens a new avenue to the targeting anticancer organosilver(I) materials.