A carbohydrate-grafted nanovesicle with activatable optical and acoustic contrasts for dual modality high performance tumor imaging

Novel activated NIR-II fluorescence/Ratio photoacoustic probe for dual-modality accurate imaging of palladium ions overload in mouse liver

Palladium contaminants can pose risks to human health and the natural environment. Once Pd2+ enters the body, it can bind with DNA, proteins, and other macromolecules, disrupting cellular processes and causing serious harm to health. Therefore, it becomes critical to develop simple, highly selective and precise methods for detecting Pd2+in vivo. Here, we have successfully developed the first activated second near-infrared region fluorescence (NIR-II FL) and ratio photoacoustic (PA) probe NYR-1 for dual-modal accurate detection of Pd2+ levels. NYR-1 is capable of rapidly (< 60 s) and sensitively detection of Pd2+ in solution, providing switched on NIR-II FL920 and ratio PA808/PA720 dual-mode signal change. More notably, the probe NYR-1 was successfully used for non-invasive imaging of Pd2+ overload in mouse liver by NIR-II FL/Ratio PA dual-modality imaging technology for the first time. Thus, this work opens up a promising dual-modal detection method for the precise detection of Pd2+ in organisms and in the environment.

Exploiting Sound for Emerging Applications of Extracellular Vesicles

Extracellular vesicles are nano- to microscale, membrane-bound particles released by cells into extracellular space, and act as carriers of biomarkers and therapeutics, holding promising potential in translational medicine. However, the challenges remain in handling and detecting extracellular vesicles for disease diagnosis as well as exploring their therapeutic capability for disease treatment. Here, we review the recent engineering and technology advances by leveraging the power of sound waves to address the challenges in diagnostic and therapeutic applications of extracellular vesicles and biomimetic nanovesicles. We first introduce the fundamental principles of sound waves for understanding different acoustic-assisted extracellular vesicle technologies. We discuss the acoustic-assisted diagnostic methods including the purification, manipulation, biosensing, and bioimaging of extracellular vesicles. Then, we summarize the recent advances in acoustically enhanced therapeutics using extracellular vesicles and biomimetic nanovesicles. Finally, we provide perspectives into current challenges and future clinical applications of the promising extracellular vesicles and biomimetic nanovesicles powered by sound.

Acoustic-Based Theranostic Probes Activated by Tumor Microenvironment for Accurate Tumor Diagnosis and Assisted Tumor Therapy

Acoustic-based imaging techniques, including ultrasonography and photoacoustic imaging, are powerful noninvasive approaches for tumor imaging owing to sound transmission facilitation, deep tissue penetration, and high spatiotemporal resolution. Usually, imaging modes were classified into "always-on" mode and "activatable" mode. Conventional "always-on" acoustic-based probes often have difficulty distinguishing lesion regions of interest from surrounding healthy tissues due to poor target-to-background signal ratios. As compared, activatable probes have attracted attention with improved sensitivity, which can boost or amplify imaging signals only in response to specific biomolecular recognition or interactions. The tumor microenvironment (TME) exhibits abnormal physiological conditions that can be used to identify tumor sections from normal tissues. Various types of organic dyes and biomaterials can react with TME, leading to obvious changes in their optical properties. The TME also affects the self-assembly or aggregation state of nanoparticles, which can be used to design activatable imaging probes. Moreover, acoustic-based imaging probes and therapeutic agents can be coencapsulated into one nanocarrier to develop nanotheranostic probes, achieving tumor imaging and cooperative therapy. Satisfactorily, ultrasound waves not only accelerate the release of encapsulated therapeutic agents but also activate therapeutic agents to exert or enhance their therapeutic performance. Meanwhile, various photoacoustic probes can convert photon energy into heat under irradiation, achieving photoacoustic imaging and cooperative photothermal therapy. In this review, we focus on the recently developed TME-triggered ultrasound and photoacoustic theranostic probes for precise tumor imaging and targeted tumor therapy.

Targeted contrast agents and activatable probes for photoacoustic imaging of cancer

Photoacoustic (PA) imaging has emerged as a powerful technique for the high resolution visualization of biological processes within deep tissue. Through the development and application of exogenous targeted contrast agents and activatable probes that can respond to a given cancer biomarker, researchers can image molecular events in vivo during cancer progression. This information can provide valuable details that can facilitate cancer diagnosis and therapy monitoring. In this tutorial review, we provide a step-by-step guide to select a cancer biomarker and subsequent approaches to design imaging agents for in vivo use. We envision this information will be a useful summary to those in the field, new members to the community, and graduate students taking advanced imaging coursework. We also highlight notable examples from the recent literature, with emphasis on the molecular designs and their in vivo PA imaging performance. To conclude, we provide our outlook and future perspective in this exciting field.

Development of pH-activatable fluorescent probes for rapid visualization of metastatic tumours and fluorescence-guided surgery via topical spraying

A series of pH-activatable aza-BODIPY-based fluorescent probes were developed for rapid cancer visualization and real-time fluorescence-guided surgery by harnessing topical spraying. These probes exhibited good water-solubility, a tunable pK_a from 5.0 to 7.9, and stable intense NIR emission at ∼725 nm under acidic conditions. AzaB5 with a pK_a value of 6.7 was able to rapidly and clearly visualize pulmonary and abdominal metastatic tumours including tiny metastases less than 2 mm via topical spraying, further improving intraoperative fluorescence-guided resection. We believe that AzaB5 is promising as a powerful tool to rapidly delineate a broad range of malignancies and assist surgical tumour resection.

Galectin Trafficking Pathway-Enabled Color-Switchable Detection of Lysosomal Membrane Permeabilization

Lysosomal membrane permeabilization (LMP) engaged in multiple human diseases is accompanied by relocation of cytosolic galectin into LMP⁺ lysosomes. We herein reported a galectin trafficking-targeted method to image LMP using two kinds of glyco-dendrimers, a sialic acid-terminated dendrimer labeled with pH-inert rhodamine and a lactose-terminated dendrimer labeled with fluorescein that becomes green-emissive in pH-elevated lysosomes. Albeit both accumulated in physiological lysosomes, the former is released from LMP⁺ lysosomes while the latter binds to galectin accumulated in LMP⁺ lysosomes and thus trapped in LMP⁺ lysosomes. Accordingly, LMP⁺ lysosomes exhibit loss of red fluorescence and turn-on green fluorescence due to loss of lysosomal acidity. This red-to-green color switch enables discernment of LMP⁺ lysosomes from physiological lysosomes and pH-elevated lysosomes and can be further utilized to detect LMP in distinct cell death pathways. These results suggest the utility of galectin trafficking pathway-integrated synthetic probes for detection of LMP, a key factor for diseased cells.

Two birds with one stone: A highly sensitive near-infrared BODIPY-based fluorescent probe for the simultaneous detection of Fe2+ and H+ in vivo

Ferrous ion (Fe²⁺) plays an essential role in many physiological and pathological processes, and its cellular metabolism is closely related to acidic pH. However, the lack of multifunctional Fe²⁺ probes has hindered the further study of Fe²⁺ in vivo. Herein, we report a dual-responsive near-infrared (NIR) fluorescent probe BODIPY-Fe for the simultaneous of Fe²⁺ and H⁺ in vivo by harnessing the N-oxide strategy and photoinduced electron transfer (PeT) mechanism. BODIPY-Fe exhibited NIR fluorescence at 671 nm, rapid response to Fe²⁺ within 90 s, and high sensitivity of low LOD of 292 nM towards Fe²⁺. Moreover, BODIPY-Fe could sensitively and selectively detect Fe²⁺ and H⁺ in the lysosomes of living cells simultaneously. Notably, BODIPY-Fe was able to noninvasively visualize Fe²⁺ and H⁺ in vivo, showing "ON-OFF-ON" NIR fluorescence signal changes. This work demonstrates that BODIPY-Fe has great potential to promote the simultaneous imaging of Fe²⁺ and H⁺ in biological systems.

Collaborative assembly of doxorubicin and galactosyl diblock glycopolymers for targeted drug delivery of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) patients suffer from severe pain due to the serious systemic side effects and low efficiency of chemotherapeutic drugs, and it is important to develop novel drug delivery systems to circumvent these issues. In this study, a series of galactose-based glycopolymers, poly(N-(prop-2-enoyl)-β-d-galactopyranosylamine)-b-poly(N-isopropyl acrylamide) (pGal(OH)-b-pNIPAA), were prepared through a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and tetrabutylammonium hydroxide (TBAOH)-mediated removal of acetyl groups. Hydrophilic doxorubicin hydrochloride was introduced to undergo collaborative assembly with poly(N-(prop-2-enoyl)-β-d-peracetylated galactosamine)-b-poly(N-isopropyl acrylamide) (pGal(Ac)-b-pNIPAA) via TBAOH treatment. pGal-b-pNIPAA/doxorubicin (DOX) delivery nanoparticles (GND NPs) formed by collaborative assembly were fully characterized by NMR, TEM and FT-IR, indicating the well-controlled formation of particles with uniform size and high efficiency in terms of drug loading and encapsulation compared with conventional adsorption methods. Meanwhile, the GND NPs were observed to be rapidly disintegrated under acidic conditions and resulted in an increased release of DOX. Cellular experiments showed that pGal-b-pNIPAA/DOX is apparently an asialoglycoprotein receptor (ASGPR)-mediated target of HCC, resulting in enhanced cellular uptake to HepG2 cells and anti-tumor efficacy in vitro. Furthermore, GND NPs III exerted more sustainable and effective anti-tumor effects compared to free DOX on a transgenic zebrafish TO(Kras^G12V) model in vivo. These results indicated that the biocompatible nanomaterials developed by collaborative assembly with galactosyl diblock glycopolymers and DOX may serve as a promising candidates for targeting therapy of HCC.

Tumor pH-Responsive Albumin/Polyaniline Assemblies for Amplified Photoacoustic Imaging and Augmented Photothermal Therapy

Tumor-microenvironment-responsive theranostics have great potential for precision diagnosis and effective treatment of cancer. Polyaniline (PANI) is the first reported pH-responsive organic photothermal agent and is widely used as a theranostic agent. However, tumor pH-responsive PANI-based theranostic agents are not explored, mainly because the conversion from the emeraldine base (EB) to emeraldine salt (ES) state of PANI requires pH < 4, which is lower than tumor acidic microenvironment. Herein, a tumor pH-responsive PANI-based theranostic agent is designed and prepared for amplified photoacoustic imaging guided augmented photothermal therapy (PTT), through intermolecular acid-base reactions between carboxyl groups of bovine serum albumin (BSA) and imine moieties of PANI. The albumin/PANI assemblies (BSA-PANI) can convert from the EB to ES state at pH < 7, accompanied by the absorbance redshift from visible to near-infrared region. Both in vitro and in vivo results demonstrate that tumor acidic microenvironment can trigger both the photoacoustic imaging (PAI) signal amplification and the PTT efficacy enhancement of BSA-PANI assemblies. This work not only highlights that BSA-PANI assemblies overcome the limitation of low-pH protonation, but also provides a facile assembly strategy for a tumor pH-responsive PANI-based nanoplatform for cancer theranostics.

Facile in situ synthesis of ultrasmall near-infrared-emitting gold glyconanoparticles with enhanced cellular uptake and tumor targeting

The simultaneous possession of high tumor-targeting efficiency, long blood circulation, and low normal-tissue retention is critical for future clinically translatable nanomedicines. Herein, we reported a facile in situ glycoconjugation strategy for the synthesis of near-infrared (NIR)-emitting gold glyconanoparticles (AuGNPs, ∼2.4 nm) using 1-thio-β-d-glucose as both the surface ligand and the reducing agent in the presence of a gold precursor. The ultrasmall AuGNPs showed similar low healthy organ retention to that of the renal-clearable ultrasmall nonglyconanoparticles, but ∼10 and 2.5 times higher in vitro and in vivo tumor-targeting efficiencies, respectively, were observed. This facile glycoconjugation strategy of ultrasmall AuGNPs was found to show activity towards glucose transporters in the cancer cells and prolonged blood circulation with both renal and hepatobiliary clearance pathways, which synergistically enhanced the tumor targeting of the ultrasmall AuGNPs. This discovery provides a smart strategy for the improvement in tumor targeting by ultrasmall NPs and further strengthens our understanding of glycoconjugation in designing future clinically translatable nanomedicines.

Photothermal therapy and photoacoustic imaging via nanotheranostics in fighting cancer

The nonradiative conversion of light energy into heat (photothermal therapy, PTT) or sound energy (photoacoustic imaging, PAI) has been intensively investigated for the treatment and diagnosis of cancer, respectively. By taking advantage of nanocarriers, both imaging and therapeutic functions together with enhanced tumour accumulation have been thoroughly studied to improve the pre-clinical efficiency of PAI and PTT. In this review, we first summarize the development of inorganic and organic nano photothermal transduction agents (PTAs) and strategies for improving the PTT outcomes, including applying appropriate laser dosage, guiding the treatment via imaging techniques, developing PTAs with absorption in the second NIR window, increasing photothermal conversion efficiency (PCE), and also increasing the accumulation of PTAs in tumours. Second, we introduce the advantages of combining PTT with other therapies in cancer treatment. Third, the emerging applications of PAI in cancer-related research are exemplified. Finally, the perspectives and challenges of PTT and PAI for combating cancer, especially regarding their clinical translation, are discussed. We believe that PTT and PAI having noteworthy features would become promising next-generation non-invasive cancer theranostic techniques and improve our ability to combat cancers.

An active DNA-based nanoprobe for photoacoustic pH imaging

We report an active DNA construct capable of probing pH through a photoacoustic (PA) ratiometric analysis approach. Our nanoprobe enables different PA readout in tissue mimicking phantoms in the range between pH 6.8 to 7.8 at physiologically relevant sodium concentrations. Thus, it represents a promising platform to probe pH values relevant to the tumor microenvironment using PA.

Photoacoustic Probes for Molecular Detection: Recent Advances and Perspectives

Photoacoustic (PA) imaging (PAI) is a noninvasive and nonionizing biomedical imaging modality that combines the advantages of optical imaging and ultrasound imaging. Based on PAI, photoacoustic detection (PAD) is an emerging approach that is involved with the interaction between PA probes and analytes resulting in the changes of photoacoustic signals for molecular detection with rich contrast, high resolution, and deep tissue penetration. This Review focuses on the recent development of PA probes in PAD. The following contents will be discussed in detail: 1) the construction of PA probes; 2) the applications and mechanisms of PAD to different types of analytes, including microenvironments, small biomolecules, or metal ions; 3) the challenges and perspectives of PA probes in PAD.

A nitroreductase and acidity detecting dual functional ratiometric fluorescent probe for selectively imaging tumor cells

A dual functional ratiometric fluorescent probe can obviously distinguish acidity, nitroreductase, and nitroreductase in an acidic environment. Confocal fluorescence imaging of A549 cells indicates the probe can detect acidity and expressed nitroreductase in living cells.

Development of Photoacoustic Probes for in Vivo Molecular Imaging

Photoacoustic (PA) imaging is an emerging, non-invasive imaging modality that encompasses attributes of both optical and ultrasound imaging. Because of the combination of optical excitation and acoustic detection, PA imaging enables high contrast and high resolution within deep tissue (centimeter depths). Recent advances in PA probe development have allowed for stimulus-responsive imaging in a variety of biological models with implications for basic, translational, and clinical sciences. This perspective highlights recent progress in the development of PA probes and their application to live-animal molecular imaging.

Advanced Photoacoustic Imaging Applications of Near-Infrared Absorbing Organic Nanoparticles

Progress of nanotechnology in recent years has stimulated fast development of nanoparticles in biomedical research. Photoacoustic (PA) imaging as an emerging non-invasive technique in molecular imaging has improved imaging depth relative to conventional optical imaging, demonstrating great potential in clinical applications. The convergence of nanotechnology and PA imaging has enabled a broad spectrum of new opportunities in fundamental biology and translation medicine. This review focuses on the recent advances of organic nanoparticles in PA imaging applications. Near-infrared absorbing organic nanoparticles are classified and discussed according to their different imaging applications, which include tumor imaging, gastrointestinal imaging, sentinel lymph node imaging, disease microenvironment imaging and real-time drug imaging. The chemistry and PA properties of organic nanoparticles are discussed in details to highlight their own merits, and their challenges and perspectives in PA imaging are also discussed.

High-Contrast Fluorescence Detection of Metastatic Breast Cancer Including Bone and Liver Micrometastases via Size-Controlled pH-Activatable Water-Soluble Probes

Breast cancer metastasis is the major cause of cancer death in women worldwide. Early detection would save many lives, but current fluorescence imaging probes are limited in their detection ability, particularly of bone and liver micrometastases. Herein, probes that are capable of imaging tiny (<1 mm) micrometastases in the liver, lung, pancreas, kidneys, and bone, that have disseminated from the primary site, are reported. The influence of the poly(ethylene glycol) (PEG) chain length on the performance of water-soluble, pH-responsive, near-infrared 4,4'-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) probes is systematically investigated to demonstrate that PEG tuning can provide control over micrometastasis tracking with high tumor-to-background contrast (up to 12/1). Optimized probes can effectively visualize tumor boundaries and successfully detect micrometastases with diameters <1 mm. The bone-metastasis-targeting ability of these probes is further enhanced by covalent functionalization with bisphosphonate. This improved detection of both bone and liver micrometastases (<2 mm) with excellent tumor-to-normal contrast (5.2/1). A versatile method is thus introduced to directly synthesize modular water-soluble probes with broad potential utility. Through a single intravenous injection, these materials can image micrometastases in multiple organs with spatiotemporal resolution. They thus hold promise for metastasis diagnosis, image-guided surgery, and theranostic PEGylated drug therapies.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

Responsive hetero-organelle partition conferred fluorogenic sensing of mitochondrial depolarization

Malfunctioning organelles are often difficult to probe with classical organelle-homing sensors owing to disruption of physiological organelle-probe affinity. We herein report the use of a responsive hetero-organelle partition and signal activable probe (RC-TPP) for detecting mitochondrial depolarization, a pathologically relevant event featuring loss of the electrical potentials across the mitochondrial membrane (ΔΨm). Partitioned in mitochondria to give blue fluorescence, RC-TPP relocates into lysosomes upon mitochondrial depolarization and exhibits red fluorescence triggered by lysosomal acidity, enabling determination of autophagy relevant mitochondrial depolarization and the chronological sequence of mitochondrial depolarization and lysosomal neutralization in distinct cell death signalling pathways. As an alternative to classic homo-organelle specific molecular systems, this hetero-organelle responsive approach provides a new perspective from which to study dysfunctional organelles.

Near-Infrared Probe Based on Rhodamine Derivative for Highly Sensitive and Selective Lysosomal pH Tracking

The development of near-infrared fluorescent probes with low pK_a, high selectivity, high photostability, and high sensitivity for lysosomal pH detection is of great importance. In the present work, we developed a novel near-infrared lysosomal pH probe (Lyso-hNR) based on a rhodamine derivative. Lyso-hNR showed fast, highly sensitive, and highly selective fluorescence response to acidic pH caused by the H⁺-induced structure changes from the nonfluorescent spirolactam form to the highly emissive open-ring form. Lyso-hNR displays a significant fluorescence enhancement at 650 nm (over 280-fold) from pH 7.0 to 4.0 with a pK_a value of 5.04. Live cell imaging data revealed that Lyso-hNR can selectively monitor lysosomal pH changes with excellent photostability and low cytotoxicity. In addition, Lyso-hNR can be successfully used in tracking lysosomal pH changes induced by chloroquine and those during apoptosis. All these features render Lyso-hNR a promising candidate to investigate lysosome-associated physiological and pathological processes.

Supramolecular core–glycoshell polythiophene nanodots for targeted imaging and photodynamic therapy

We show that supramolecular core–glycoshell nanodots are capable of targeted imaging and photodynamic therapy of liver and triple-negative breast cancer cells.

Development of a unique family of two-photon full-color-tunable fluorescent materials for imaging in live subcellular organelles, cells, and tissues

We outline the rational design, synthesis, optical property studies, and biological imaging studies of a unique family of two-photon full-color-tunable functional fluorescent materials.

Functional computer-to-plate near-infrared absorbers as highly efficient photoacoustic dyes

Photoacoustic imaging (PAI) is an emerging modality in biomedical imaging. Photoacoustic effect is the basis for PAI, where a photoacoustic contrast agent absorbs optical pulses to initiate localized heating and rapid thermal expansion, thus generating thermoelastic stress waves. Therefore, ideal PAI dyes should have strong NIR light absorbance and high light-heat conversion efficiency. However, most current low molecular weight organic PAI contrast agents are fluorescent dyes, where the light-heat conversion efficiency is dramatically impaired due to the energy loss by fluorescence emission. Herein, we report a series of highly efficient photoacoustic dyes with COOH, NH2 and NHS ester functionalities, from an inexpensive industrial computer-to-plate NIR absorber (IR830 p-toluenesulfonate) that has a strong NIR absorbance but an extremely low fluorescence emission. In vitro and in vivo studies show that the functional IR830 dyes have low cytotoxicity, and are 2.1 folds brighter in photoacoustic imaging than traditional photoacoustic dye indocyanine green (ICG). The Lowest Limit of Quantification of the IR830 series dyes is as low as the 1/7 of that of ICG. These indicate that the functional IR830 dyes have great potential as highly efficient photoacoustic dyes.

STATEMENT OF SIGNIFICANCE

Photoacoustic imaging (PAI) is an emerging modality in biomedical imaging. Ideal PAI dyes should have strong NIR absorbance and high light-heat conversion efficiency. However, most current low molecular weight organic PAI contrast agents are fluorescent dyes, where the light-heat conversion efficiency is dramatically impaired due to the energy loss by fluorescence emission. Herein we report a series of highly efficient functional photoacoustic dyes from an inexpensive industrial computer-to-plate NIR absorber (IR830) that has a strong NIR absorbance but an extremely low fluorescence emission. The functional IR830 dyes show low cytotoxicity, much brighter in photoacoustic imaging than traditional photoacoustic dye indocyanine green. These indicate that the functional IR830 dyes have great potential as highly efficient photoacoustic dyes.

Selective imaging and cancer cell death via pH switchable near-infrared fluorescence and photothermal effects

Accurately locating and eradicating sporadically distributed cancer cells whilst minimizing damage to adjacent normal tissues is vital in image-guided tumor ablation. In this work, we developed four heptamethine cyanine based theranostic probes, IR1-4, that demonstrated unique pH switchable near-infrared (NIR) fluorescence and photothermal efficiency. While their fluorescence quantum yields increased up to 1020-fold upon acidification from pH 7.4 to 2.4, their photothermal efficiencies decreased up to 7.1-fold concomitantly. Theoretical calculations showed that protonation of the probes in an acidic environment increased the orbital energy gaps and reduced the intramolecular charge transfer efficiency, resulting in the conversion of absorbed light energy to NIR fluorescence instead of hyperthermia. Substitutions at the terminal indole of the probes fine-tuned their pKafluo values to a narrow physiological pH range of 4.0-5.3. IR2, with a pKafluo of 4.6, not only specifically illuminated cancer cells by sensing their more acidic lysosomal lumen, but also selectively ablated cancer cells via its maximized photothermal effects in the alkaline mitochondrial matrix. As far as we are aware, these probes not only offer the highest physiological acidity triggered NIR fluorescence enhancement as small molecules, but are also the first to specifically visualize and eradicate cancer cells by sensing their altered pH values in cellular organelles. Considering that a disordered pH in organelle lumen is a common characteristic of cancer cells, these theranostic probes hold the promise to be applied in image-guided tumor ablation over a wide range of tumor subtypes.

A FRET probe with AIEgen as the energy quencher: dual signal turn-on for self-validated caspase detection

The accurate detection of biological substances is highly desirable to study various biological processes and evaluate disease progression. Herein, we report a self-validated fluorescent probe which is composed of a coumarin fluorophore as the energy donor and a fluorogen with aggregation-induced emission characteristics (AIEgen) as the energy quencher linked through a caspase-3 specific peptide substrate. Unlike the traditionally widely studied fluorescence resonance energy transfer (FRET) probes, our new generation of FRET probe is non-fluorescent itself due to the energy transfer as well as the dissipation of the acceptor energy through the free molecular motion of AIEgen. Upon interaction with caspase-3, the probe displays strong green and red fluorescent signals synchronously due to the separation of the donor-quencher and aggregation of the released AIEgen. The fluorescence turn-on with dual signal amplification allows real-time and self-validated enzyme detection with a high signal-to-background ratio, providing a good opportunity to accurately monitor various biological processes in a real-time manner.

Are nanotheranostics and nanodiagnostics-guided drug delivery stepping stones towards precision medicine?

The progress in medical research has led to the understanding that cancer is a large group of heterogeneous diseases, with high variability between and within individuals. This variability sprouted the ambitious goal to improve therapeutic outcomes, while minimizing drug adverse effects through stratification of patients by the differences in their disease markers, in a personalized manner, as opposed to the strategy of "one therapy fits all". Nanotheranostics, composed of nanoparticles (NPs) carrying therapeutic and/or diagnostics probes, have the potential to revolutionize personalized medicine. There are different modalities to combine these two distinct fields into one system for a synergistic outcome. The addition of a nanocarrier to a theranostic system holds great promise. Nanocarriers possess high surface area, enabling sophisticated functionalization with imaging agents, thus gaining enhanced diagnostic ability in real-time. Yet, most of the FDA-approved theranostic approaches are based on small molecules. The theranostic approaches that are reviewed herein are paving the road towards personalized medicine through all stages of patient care: starting from screening and diagnostics, proceeding to treatment and ending with treatment follow-up. Our current review provides a broad background and highlights new insights for the rational design of theranostic nanosystems for desired therapeutic niches, while summoning the hurdles on their way to become first-line diagnostics and therapeutics for cancer patients.

A dual-responsive nanocapsule via disulfide-induced self-assembly for therapeutic agent delivery

One-step synthesis of fluorescent molecules (SNBDP) containing one disulfide bond and two o-nitrobenzyl groups was demonstrated via multi-component Passerini reaction.

One-step synthesis of fluorescent molecules (SNBDP) containing one disulfide bond and two o-nitrobenzyl groups was demonstrated via multi-component Passerini reaction. This hydrophobic SNBDP could self-assemble into nanocapsules (SNBDP NCs) in aqueous solution via disulfide-induced assembly. The obtained nanocapsules were stable in aqueous solution for several weeks and exhibited enhanced fluorescence when nanocapsules were destroyed due to disaggregation-induced emission. The nanocapsules not only were reduction-sensitive and light-responsive, but also could be endocytosed by HeLa cells for cellular imaging. The enhanced fluorescence in the glutathione (GSH) pretreated HeLa cells showed that the compound was reduction-sensitive in living cells. In vitro WST-8 assays showed the nanocapsules were biocompatible and could further be used as drug delivery carriers. Indocyanine green (ICG), a clinically approved NIR dye, was loaded into the nanocapsules (ICG@SNBDP NCs). ICG@SNBDP NCs showed enhanced photothermal efficacy compared with same concentration of free ICG under 808-nm laser irradiation. Consequently, ICG@SNBDP NCs upon NIR irradiation can effectively kill cancer cells through local hyperthermia. These results highlight the potential of disulfide-induced nanocapsules as smart nanoparticles for cellular imaging and therapeutic agent delivery.