NIR Emission Nanoparticles Based on FRET Composed of AIE Luminogens and NIR Dyes for Two-photon Fluorescence Imaging

(Nano)biotechnological approaches in the treatment of cervical cancer: integration of engineering and biology

Cervical cancer is one of the most malignant gynaecological tumors characterised with the aggressive behaviour of the tumor cells. In spite of the development of different strategies for the treatment of cervical cancer, the tumor cells have developed resistance to conventional therapeutics. On the other hand, nanoparticles have been recently applied for the treatment of human cancers through delivery of drugs and facilitate tumor suppression. The stimuli-sensitive nanostructures can improve the release of therapeutics at the tumor site. In the present review, the nanostructures for the treatment of cervical cancer are discussed. Nanostructures can deliver both chemotherapy drugs and natural compounds to increase anti-cancer activity and prevent drug resistance in cervical tumor. Moreover, the genetic tools such as siRNA can be delivered by nanoparticles to enhance their accumulation at tumor site. In order to enhance selectivity, the stimuli-responsive nanoparticles such as pH- and redox-responsive nanocarriers have been developed to suppress cervical tumor. Moreover, nanoparticles can induce photo-thermal and photodynamic therapy to accelerate cell death in cervical tumor. In addition, nanobiotechnology demonstrates tremendous potential in the treatment of cervical cancer, especially in the context of tumor immunotherapy. Overall, metal-, carbon-, lipid- and polymer-based nanostructures have been utilized in cervical cancer therapy. Finally, hydrogels have been developed as novel kinds of carriers to encapsulate therapeutics and improve anti-cancer activity.

Catalytic NIR chemiluminescence sensor with enhanced persistence and intensity for in vivo imaging

Chemiluminescence (CL) is a self-illumination phenomenon that involves the emission of light from chemical reactions, and it provides favorable spatial and temporal information on biological processes. However, it is still a great challenge to construct effective CL sensors that equip strong CL intensity, long emission wavelength, and persistent luminescence for deep tissue imaging. Here, we report a liposome encapsulated polymer dots (Pdots)-based system using catalytic CL substrates (L-012) as energy donor and fluorescent polymers and dyes (NIR 695) as energy acceptors for efficient Near-infrared (NIR) CL in vivo imaging. Thanks to the modulation of paired donor and acceptor distance and the slow diffusion of biomarker by liposome, the Pdots show a NIR emission wavelength (λ em, max = 720 nm), long CL duration (>24 h), and a high chemiluminescence resonance energy transfer efficiency (46.5 %). Furthermore, the liposome encapsulated Pdots possess excellent biocompatibility, sensitive response to H2O2, and persistent whole-body NIR CL imaging in the drug-induced inflammation and the peritoneal metastatic tumor mouse model. In a word, this NIR-II CL nanoplatform with long-lasting emission and high spatial-temporal resolution will be a concise strategy in deep tissue imaging and clinical diagnostics.

Detection of free DNA based on metal-enhanced fluorescence triggered by CRISPR-Cas12a and colorimetric analysis

The CRISPR-Cas system has been found to be extremely sensitive and there is an urgent demand to extend its potential in bioassays. Herein, we developed a novel nanobiosensor to detect the human papillomavirus 16 genes (HPV-16 DNA), which is triggered by CRISPR-Cas12a to amplify the fluorescence signal by metal-enhanced fluorescence (CAMEF). Along with the changing of the fluorescence signal, the aggregation of the substrate of MEF also leads to a change in the color of the mixture solution, enabling dual signal detection with the fluorescence and the naked eye. Furthermore, the designed CAMEF probe was verified to detect the HPV-16 DNA accurately and reliably in biological samples. Triggered by the CRISPR system, the designed CAMEF probe allows quantitative detection of the HPV-16 DNA in the wide range of 10-500 pM. Owing to the MEF, the fluorescence signal of the CAMEF probe was significantly amplified with the detection limit as low as 1 pM. Besides, we can determine the concentration of HPV-16 DNA simply by the naked eye, which also drastically reduces the possibility of false-positive signals. Theoretically, the target ssDNA could be any strand of DNA obtained by designing the crRNA sequence in the CRISPR-Cas system. We believe that the designed CAMEF sensor can present a reliable approach for the accurate detection of low amounts of target ssDNA in complex biological samples.

Visualization and correlation of drug release of risperidone/clozapine microspheres in vitro and in vivo based on FRET mechanism

This study addresses the challenging task of quantitatively investigating drug release from PLGA microspheres after in vivo administration. The objective is to employ Förster resonance energy transfer (FRET) to visualize drug-encapsulated microspheres in both in vitro and in vivo settings. The primary goal is to establish a quantitative correlation between FRET fluorescence changes and microsphere drug release. The study selects drugs with diverse structures and lipid solubility to explore release mechanisms, using PLGA as the matrix material. Clozapine and risperidone serve as model drugs. FRET molecules, Cy5 and Cy5.5, along with Cy7 derivatives, create FRET donor-acceptor pairs. In vitro results show that FRET fluorescence changes align closely with microsphere drug release, particularly for the Cy5.5-Cy7 pair. In vivo experiments involve subcutaneous administration of microspheres to rats, tracking FRET fluorescence changes while collecting blood samples. Pharmacokinetic studies on clozapine and risperidone reveal in vivo absorption fractions using the Loo-Riegelman method. Correlating FRET and in vivo absorption data establishes an in vitro-in vivo relationship (IVIVR). The study demonstrates that FRET-based fluorescence changes quantitatively link to microsphere drug release, offering an innovative method for visualizing and monitoring release in both in vitro and in vivo settings, potentially advancing clinical applications of such formulations.

Dual-color nanospheres based on aggregation-induced emission and catalytic hairpin assembly for simultaneous imaging of acrylamide and miR-21 in living cells

Acrylamide (AA) is a heat-processed potent food carcinogen that is widely used in industry, posing a significant risk to human health. Therefore, it is necessary to investigate the toxic effects and mechanism of AA. miR-21 is a representative biomarker during AA-induced carcinogenesis. Here, dual-color aggregation-induced emission nanoparticles (AIENPs) were developed for the detection and simultaneous imaging of AA and miR-21. AIENPs were synthesized by combining aggregation-induced emission (AIE) dyes and a poly (styrene-co-maleic anhydride) (PSMA) amphiphilic polymer modified with hairpin DNA. Upon AA intervention and aptamer recognition, cDNA was dissociated, leading to miR-21 overexpression and initiating the catalytic hairpin assembly cycle. Consequently, fluorescence quenching was observed due to FRET between AIENPs and labeled quenchers. The relative fluorescence intensities of dual-color AIENPs displayed good linear relationships with logarithmic AA and miR-21 concentrations. Moreover, there was a gradual decrease in dual-color AIENP fluorescence as the HepG2 cell concentration of AA (0-500 μM) and stimulation time (0-12 h) increased, making it possible to simultaneously image AA and AA-induced miR-21. The findings of this work are valuable for revealing the cytotoxic mechanism of AA.

Fabrication of FA/HA-functionalized carbon dots for human breast cancer cell targeted imaging

Green fluorescent carbon dots (CDs) were prepared by one-step hydrothermal method and then modified into folic acid functionalized carbon dots (FA-CDs) and hyaluronic acid functionalized carbon dots (HA-CDs) with targeted function to study their application in breast cancer cells imaging. The microstructure of the CDs observed through TEM showed the CDs with a scale of 2.69 nm. FT-IR and XPS showed the changes of bonds and functional groups that confirmed the transformation of COOH and NH₂ to amide bonds. FA-CDs and HA-CDs had good water solubility and cytocompatibility, which laid a foundation for their application in human breast cancer cells imaging. At the same time, FA-CDs and HA-CDs had strong fluorescence excitation, and the optimal emission wavelength was about 450 nm. In fluorescence imaging of cells, carbon dots had bright green fluorescence in both breast cancer cells (MCF-7 cells) and normal cells (EC cells). After targeted endocytosis, FA-CDs and HA-CDs could emit bright green fluorescence in cancer cells but could not in normal cells, which proved that the synthesized FA-CDs and HA-CDs had targeting properties. FA-CDs and HA-CDs could be used to accurately identify breast cancer cells and normal cells as cancer diagnosis material, which had the potential application in early cancer diagnosis.

Visible-light and near-infrared fluorescence and surface-enhanced Raman scattering point-of-care sensing and bio-imaging: a review

This review article deals with the concepts, principles and applications of visible-light and near-infrared (NIR) fluorescence and surface-enhanced Raman scattering (SERS) in in vitro point-of-care testing (POCT) and in vivo bio-imaging. It has discussed how to utilize the biological transparency windows to improve the penetration depth and signal-to-noise ratio, and how to use surface plasmon resonance (SPR) to amplify fluorescence and SERS signals. This article has highlighted some plasmonic fluorescence and SERS probes. It has also reviewed the design strategies of fluorescent and SERS sensors in the detection of metal ions, small molecules, proteins and nucleic acids. Particularly, it has provided perspectives on the integration of fluorescent and SERS sensors into microfluidic chips as lab-on-chips to realize point-of-care testing. It has also discussed the design of active microfluidic devices and non-paper- or paper-based lateral flow assays for in vitro diagnostics. In addition, this article has discussed the strategies to design in vivo NIR fluorescence and SERS bio-imaging platforms for monitoring physiological processes and disease progression in live cells and tissues. Moreover, it has highlighted the applications of POCT and bio-imaging in testing toxins, heavy metals, illicit drugs, cancers, traumatic brain injuries, and infectious diseases such as COVID-19, influenza, HIV and sepsis.

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.

Polymer encapsulated clinical ICG nanoparticles for enhanced photothermal therapy and NIR fluorescence imaging in cervical cancer

Photothermal therapy (PTT) is a popular tumor therapy method, which is based on efficient photothermal nanoagents (PTNs). Clinical Indocyanine Green (ICG), as a Food and Drug Administration (FDA) approved agent, is an often-used PTN, meanwhile it is also a good near-infrared (NIR) fluorescence contrast agent. However, the further applications of ICG in biomedical fields are limited due to its poor stability. In this study, ICG was encapsulated by the amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA) to form ICG@PSMA nanoparticles. Furthermore, optical and thermal characteristics of ICG@PSMA nanoparticles were studied in detail. Strong NIR fluorescence and excellent photothermal properties of ICG@PSMA nanoparticles under 808 nm laser irradiation were measured. Besides, favorable biocompatibility of ICG@PSMA nanoparticles was demonstrated on a human cervical cancer cell line (HeLa) via cell viability studies. Hence, ICG@PSMA nanoparticles were further applied to enhanced PTT of living HeLa cells under 808 nm excitation, and a high PTT efficiency of ∼70% was obtained. The novel ICG nanoparticles as a promising PTT nanoplatform could offer an opportunity for further tumour treatments.

PSMA encapsulated Clinical ICG to form ICG@PSMA nanoparticles. ICG@PSMA nanoparticles showed strong NIR fluorescence and excellent photothermal properties.

Fluorescent AIE-Active Materials for Two-Photon Bioimaging Applications

Fluorescence imaging has been widely used as a powerful tool for in situ and real-time visualization of important analytes and biological events in live samples with remarkably high selectivity, sensitivity, and spatial resolution. Compared with one-photon fluorescence imaging, two-photon fluorescence imaging exhibits predominant advantages of minimal photodamage to samples, deep tissue penetration, and outstanding resolution. Recently, the aggregation-induced emission (AIE) materials have become a preferred choice in two-photon fluorescence biological imaging because of its unique bright fluorescence in solid and aggregate states and strong resistance to photobleaching. In this review, we will exclusively summarize the applications of AIE-active materials in two-photon fluorescence imaging with some representative examples from four aspects: fluorescence detection, in vitro cell imaging, ex vivo tissue imaging, and in vivo vascular imaging. In addition, the current challenges and future development directions of AIE-active materials for two-photon bioimaging are briefly discussed.

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen

Developing versatile synthetic methodologies with merits of simplicity, efficiency, and environment friendliness for five-membered heterocycles is of incredible importance to pharmaceutical and material science, as well as a huge challenge to synthetic chemistry. Herein, an unexpected regioselective photoreaction to construct a fused five-membered azaheterocycle with an aggregation-induced emission (AIE) characteristic is developed under mild conditions. The formation of the five-membered ring is both thermodynamically and kinetically favored, as justified by theoretical calculation and experimental evidence. Markedly, a light-driven amplification strategy is proposed and applied in selective mitochondria-targeted cancer cell recognition and fluorescent photopattern fabrication with improved resolution. The work not only delivers the first report on efficiently generating a fused five-membered azaheterocyclic AIE luminogen under mild conditions via photoreaction, but also offers deep insight into the essence of the photosynthesis of fused five-membered azaheterocyclic compounds.

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.

Folic acid-conjugated nitrogen-doped graphene quantum dots as a fluorescent diagnostic material for MCF-7 cells

This paper reports the preparation and application of folic acid-conjugated nitrogen-doped graphene quantum dots (N-GQDs) as a fluorescent diagnostic material for MCF-7 cells of breast cancer. N-GQDs were prepared by a hydrothermal method using citric acid as the carbon source and diethylamine as the nitrogen source. The doping of different amounts of nitrogen content was effectively controlled by diethylamine. As the amount of nitrogen increased, more binding sites on the N-GQDs were supplied to the folic acid. Laser confocal scanning microscopy showed that increased folic acid binding facilitated the recognition of and entry to cancer cells, which made the labeled cells emit a stronger fluorescence and thus the cancer cells could be better detected. Cytotoxicity tests showed that the material was of low cytotoxicity, making it a promising prospect for fluorescent probes.