Hydrogen Peroxide-Responsive Nanoprobe Assists Circulating Tumor Cell Identification and Colorectal Cancer Diagnosis

A fluorescent probe for ultrarapid H2O2 detection during reagent-stimulated oxidative stress in cells and zebrafish

Hydrogen peroxide(H2O2), as a reliable signaling biomolecule for oxidative stress, its accurate detection during agent-stimulated oxidative stress plays a vital role in pathological and physiological mechanism exploration for disease theranostics. It's necessary to develop an efficient method for their detection. In view of the advantages of fluorescent probes, we rationally constructed a novel fluorescent probe Compound 2 based on 4-(Bromomethyl)benzeneboronic acid pinacol ester_Herein, a small molecule fluorescent probe was fabricated using isoflore nitrile as fluorescent group, phenylboronic acid pinacol ester as the response group, to detect H2O2. The probe Compound 2 has a strong fluorescence intensity at 575 nm, indicating that the structure of the probe molecule is reasonably designed, and the Stokes shift is up to 172 nm. While the detection time is as low as 30 s and the LOD of the probe for H2O2 is as low as 3.7 μmol/L,the quantum yield is Φ = 40.31 %. It has been successfully used for imaging detection of H2O2 in HepG2 cells and zebrafish for its low toxicity. It can be found that this small molecule fluorescent probe can identify H2O2 in tumor cells significantly and efficiently, which would realize the early diagnosis of tumor.

MnO2 nanosheets and gold nanoparticles supported electrochemical detection of circulating tumor cells

The concentration of circulating tumor cells (CTCs) in peripheral blood is strongly correlated with the progress of certain metastatic cancers. In this study, we have developed a novel and facile electrochemical biosensor for the detection of CTCs based on the use of manganese dioxide nanosheets (MnO2 NSs) and gold nanoparticles (AuNPs). Aptamer sequence of target cell is modified on the surface of AuNPs for specifical recognition. With low-speed centrifugation, numerous AuNPs@DNA can be removed from the supernatant. On the other hand, MnO2 NSs are modified on the electrode surface to capture unreacted AuNPs@DNA. The declined electrochemical signal intensity can be used to reflect the level of CTCs. This biosensor achieves a wide linear range from 10 to 104 cells mL-1 and a limit of detection as low as 3 cells mL-1. Due to the specific aptamer as the recognition element, interfering cells can be successfully distinguished and this method performs satisfactorily in clinical samples. Therefore, it has great potential to be used as a powerful tool benefiting rare cells analysis and the investigation of dynamics of cellular interactions.

Biomaterials releasing drug responsively to promote wound healing via regulation of pathological microenvironment

Wound healing is characterized by complex, orchestrated, spatiotemporal dynamic processes. Recent findings demonstrated suitable local microenvironments were necessities for wound healing. Wound microenvironments include various biological, biochemical and physical factors, which are produced and regulated by endogenous biomediators, exogenous drugs, and external environment. Successful drug delivery to wound is complicated, and need to overcome the destroyed blood supply, persistent inflammation and enzymes, spatiotemporal requirements of special supplements, and easy deactivation of drugs. Triggered by various factors from wound microenvironment itself or external elements, stimuli-responsive biomaterials have tremendous advantages of precise drug delivery and release. Here, we discuss recent advances of stimuli-responsive biomaterials to regulate local microenvironments during wound healing, emphasizing on the design and application of different biomaterials which respond to wound biological/biochemical microenvironments (ROS, pH, enzymes, glucose and glutathione), physical microenvironments (mechanical force, temperature, light, ultrasound, magnetic and electric field), and the combination modes. Moreover, several novel promising drug carriers (microbiota, metal-organic frameworks and microneedles) are also discussed.

Reactive Oxygen Species (ROS)-Responsive Biomaterials for the Treatment of Bone-Related Diseases

Reactive oxygen species (ROS) are the key signaling molecules in many physiological signs of progress and are associated with almost all diseases, such as atherosclerosis, aging, and cancer. Bone is a specific connective tissue consisting of cells, fibers, and mineralized extracellular components, and its quality changes with aging and disease. Growing evidence indicated that overproduced ROS accumulation may disrupt cellular homeostasis in the progress of bone modeling and remodeling, leading to bone metabolic disease. Thus, ROS-responsive biomaterials have attracted great interest from many researchers as promising strategies to realize drug release or targeted therapy for bone-related diseases. Herein, we endeavor to introduce the role of ROS in the bone microenvironment, summarize the mechanism and development of ROS-responsive biomaterials, and their completion and potential for future therapy of bone-related diseases.

Detection and clinical significance of circulating tumor cells in colorectal cancer

Histopathological examination (biopsy) is the "gold standard" for the diagnosis of colorectal cancer (CRC). However, biopsy is an invasive method, and due to the temporal and spatial heterogeneity of the tumor, a single biopsy cannot reveal the comprehensive biological characteristics and dynamic changes of the tumor. Therefore, there is a need for new biomarkers to improve CRC diagnosis and to monitor and treat CRC patients. Numerous studies have shown that "liquid biopsy" is a promising minimally invasive method for early CRC detection. A liquid biopsy mainly samples circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), microRNA (miRNA) and extracellular vesicles (EVs). CTCs are malignant cells that are shed from the primary tumors and/or metastases into the peripheral circulation. CTCs carry information on both primary tumors and metastases that can reflect dynamic changes in tumors in a timely manner. As a promising biomarker, CTCs can be used for early disease detection, treatment response and disease progression evaluation, disease mechanism elucidation, and therapeutic target identification for drug development. This review will discuss currently available technologies for plasma CTC isolation and detection, their utility in the management of CRC patients and future research directions.

A biotin-guided two-photon fluorescent probe for detection of hydrogen peroxide in cancer cells ferroptosis process

Hydrogen peroxide (H₂O₂) plays a vital role in organism due to its strong oxidizability, especially in resisting the invasion of pathogens. Cancer cells have abnormal concentrations of hydrogen peroxide due to their disordered reproduction. In complex biological systems, however, conventional fluorescent probes based solely on their fluorescent response to abnormal H₂O₂ overexpression in cancer cells are not enough to distinguish cancer cells from other unhealthy or immune cells. Therefore, it is necessary to develop other methods to allow the probe to selectively enter the cancer cells and perform fluorescence imaging of the hydrogen peroxide in the cancer cells. Herein, we developed a biotin-guided, two-photon fluorescent probe (BT-HP) for sensitive detection of H₂O₂ in cancer cells. Through the study on the properties of the probe, it was found that the probe can selectively enter cancer cells. The depth penetration imaging of H₂O₂ in cancer cells and tumor tissues by two-photon microscope proves the potential of the probe BT-HP as a tumor targeting H₂O₂ biosensor. The probe was further applied to detect hydrogen peroxide in cancer cells during the ferroptosis process.

Nanotechnology in emerging liquid biopsy applications

Liquid biopsy is considered as the most attractive alternative to traditional tissue biopsies. The major advantages of this approach lie in the non-invasive procedure, the rapidness of sample collection and the potential for early cancer diagnosis and real-time monitoring of the disease and the treatment response. Nanotechnology has dynamically emerged in a wide range of applications in the field of liquid biopsy. The benefits of using nanomaterials for biosensing include high sensitivity and detectability, simplicity in many cases, rapid analysis, the low cost of the analysis and the potential for portability and personalized medicine. The present paper reports on the nanomaterial-based methods and biosensors that have been developed for liquid biopsy applications. Most of the nanomaterials used exhibit great analytical performance; moreover, extremely low limits of detection have been achieved for all studied targets. This review will provide scientists with a comprehensive overview of all the nanomaterials and techniques that have been developed for liquid biopsy applications. A comparison of the developed methods in terms of detectability, dynamic range, time-length of the analysis and multiplicity, is also provided.

Reactive Oxygen Species Responsive Polymers for Drug Delivery Systems

Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms; however, as the concentration of ROS increases in the area of a lesion, this may undermine cellular homeostasis, leading to a series of diseases. Using cell-product species as triggers for targeted regulation of polymer structures and activity represents a promising approach for the treatment. ROS-responsive polymer carriers allow the targeted delivery of drugs, reduce toxicity and side effects on normal cells, and control the release of drugs, which are all advantages compared with traditional small-molecule chemotherapy agents. These formulations have attracted great interest due to their potential applications in biomedicine. In this review, recent progresses on ROS responsive polymer carriers are summarized, with a focus on the chemical mechanism of ROS-responsive polymers and the design of molecular structures for targeted drug delivery and controlled drug release. Meanwhile, we discuss the challenges and future prospects of its applications.

Ratiometric nanoprobe for circulating tumor cell detection and intracellular hydrogen peroxide evaluation in colorectal cancer patients

The application of intensity-based H₂O₂-responsive fluorescence nanoprobe for circulating tumor cell detection was limited by the complex background and the nanoprobe uptake in each CTC. In this context, we developed a ratiometric fluorescence nanoprobe, on which a H₂O₂-responsive subunit and a stable subunit grafted working as a H₂O₂ detector and a reference, respectively. When responding to intracellular H₂O₂, the reference fluorescence (580 nm) maintained as a correction background while the detector fluorescence (450 nm) was turned on to conduct CTC enumeration and intracellular H₂O₂ evaluation. Two normal cells and three colon cancer cells were examined to evaluate their endogenous H₂O₂ with the ratiometric nanoprobe by flow cytometry and confocal laser scanning microscopy. CTC sample from colorectal cancer patients was used to validate the performance of the nanoprobe for CTC enumeration and H₂O₂ evaluation. The results indicated that not only CTC could be effectively identified based on the "turn on" fluorescence, but also the viability of the identified CTCs could be assessed with the intensity of the reference fluorescence to avoid the false-positive number. Moreover, the clinical results demonstrated that the viability CTC count combined with intracellular H₂O₂ content (described as I₄₅₀/₅₈₀)were related to the tumor TNM stage, which might provide significant guidance for clinical treatments.

Enzyme-less amperometric sensor manufactured using a Nafion-LaNiO3 nanocomposite for hydrogen peroxide

In the present study, an enzyme-less amperometric sensor based on Nafion (NF) and a LaNiO3 (LNO) nanocomposite was constructed for H2O2 detection. LNO from the perovskite group was mixed with NF as an effective solubilizing and stabilizing agent that was used as a novel modifier for modification of the glassy carbon electrode (GCE). The designed sensor showed a desirable electrocatalytic response toward H2O2 reduction. The calibration curve revealed two linear portions in the concentration ranges of 0.2-50 μM and 50-3240 μM, and the detection limit was 0.035 μM. The accuracy of the interference-free sensor was checked by recovery analysis in serum samples.

Recent Advances in Tumor Microenvironment Hydrogen Peroxide-Responsive Materials for Cancer Photodynamic Therapy

Photodynamic therapy (PDT), as one of the noninvasive clinical cancer phototherapies, suffers from the key drawback associated with hypoxia at the tumor microenvironment (TME), which plays an important role in protecting tumor cells from damage caused by common treatments. High concentration of hydrogen peroxide (H₂O₂), one of the hallmarks of TME, has been recognized as a double-edged sword, posing both challenges, and opportunities for cancer therapy. The promising perspectives, strategies, and approaches for enhanced tumor therapies, including PDT, have been developed based on the fast advances in H₂O₂-enabled theranostic nanomedicine. In this review, we outline the latest advances in H₂O₂-responsive materials, including organic and inorganic materials for enhanced PDT. Finally, the challenges and opportunities for further research on H₂O₂-responsive anticancer agents are envisioned .

Recent Advances in Tumor Microenvironment Hydrogen Peroxide-Responsive Materials for Cancer Photodynamic Therapy

Photodynamic therapy (PDT), as one of the noninvasive clinical cancer phototherapies, suffers from the key drawback associated with hypoxia at the tumor microenvironment (TME), which plays an important role in protecting tumor cells from damage caused by common treatments. High concentration of hydrogen peroxide (H₂O₂), one of the hallmarks of TME, has been recognized as a double-edged sword, posing both challenges, and opportunities for cancer therapy. The promising perspectives, strategies, and approaches for enhanced tumor therapies, including PDT, have been developed based on the fast advances in H₂O₂-enabled theranostic nanomedicine. In this review, we outline the latest advances in H₂O₂-responsive materials, including organic and inorganic materials for enhanced PDT. Finally, the challenges and opportunities for further research on H₂O₂-responsive anticancer agents are envisioned .

Tumor-acidity activated surface charge conversion of two-photon fluorescent nanoprobe for enhanced cellular uptake and targeted imaging of intracellular hydrogen peroxide

Elevated levels of intracellular hydrogen peroxide (H2O2) are closely related to the development of cancers. Specific imaging of H2O2 in tumor sites would be significant not only for cancer diagnosis but also for gaining a deep understanding of the role of H2O2 in cancer. However, traditional fluorescent probes based only on responses to overexpression levels of H2O2 in cancer cells are insufficient to distinguish cancer cells from other unhealthy or healthy cells in complex biological systems. Herein, we developed a smart, two-photon fluorescent GC-NABP nanoprobe with pH-dependent surface charge conversion for tumor-targeted imaging of H2O2. The nanoprobe was constructed by the self-assembly of amphiphilic GC-NABP, which was synthesized by grafting the hydrophobic, H2O2-responsive and two-photon fluorophore, NABP, onto hydrophilic biopolymer glycol chitosan (GC). Taking advantage of pH-titratable amino groups on GC, the nanoprobe had the capability of surface charge conversion from negative at physiologic pH to positive in the acidic tumor microenvironment. The positive charge of the nanoprobe promoted electrostatic interactions with cell membranes, leading to enhanced cellular uptake in acidic environment. Upon cellular uptake, the high level of H2O2 in tumor cells triggered boronate deprotections of the nanoprobe, generating a "turn-on" fluorescence emission for H2O2 imaging. The nanoprobe exhibited good sensitivity and selectivity to H2O2 with a detection limit down to 110 nM in vitro. The results from flow cytometry and two-photon fluorescence imaging of H2O2 in living cells and tissues evidenced the enhanced cellular uptake and targeted imaging of intracellular H2O2 in acidic environment. Compared to control nanoparticles that lack pH sensitivity, our nanoprobe showed enhanced accumulation in tumor sites and was applied to targeted imaging of H2O2 in a tumor-bearing mouse model. This work demonstrates that the nanoprobe GC-NABP holds great promise for tumor-specific imaging of cellular H2O2, providing a potential tool to explore the role of H2O2 in tumor sites.

Differential Diagnosis and Precision Therapy of Two Typical Malignant Cutaneous Tumors Leveraging Their Tumor Microenvironment: A Photomedicine Strategy

Elevated hydrogen peroxide (H2O2) in biological tissues is generally recognized to be relevant to the carcinogenesis process that regulates the proliferative activity of cancer cells and the transformation of malignant features. Inspired by this observation, it can be hypothesized that imaging H2O2 in the tumor microenvironment (TME) could help diagnose tumor types and malignancy, and even guide precise therapy. Thus, in this study, a noninvasive photomedicine strategy is demonstrated that leverages the different levels of H2O2 in the TME, and two representative skin cancers, malignant melanoma (MM, clinically higher incidence of metastasis and recurrence) and cutaneous squamous cell carcinoma (cSCC, relatively less dangerous), are differentially diagnosed. The working probe used here is one we previously developed, namely, intelligent H2O2 responsive ABTS-loaded HRP@Gd nanoprobes (iHRANPs). In this study, iHRANPs have advantages over ratiometric imaging due to their bimodal imaging elements, in which the inherent magnetic resonance imaging (MR) mode can be used as the internal imaging reference and the H2O2 responsive photoacoustic (PA) imaging modality can be used for differential diagnosis. Results showed that after intravenous injection of iHRANPs, the tumor signals on both MM and cSCC are obviously enhanced without significant difference under the MR modality. However, under the PA modality, MM and cSCC can be easily distinguished with obvious variations in signal enhancement. Particularly, guided by PA imaging, photothermal therapy (PTT) can be precisely applied on MM, and a strong antitumor effect was achieved owing to the excessive H2O2 in the TME of MM. Furthermore, exogenous H2O2 was injected into cSCC to remedy H2O2 deficiency in the TME of cSCC, and an evident therapeutic efficacy on cSCC can also be realized. This study demonstrated that MM can be differentially diagnosed from cSCC by noninvasive imaging of H2O2 in the TME with iHRANPs; meanwhile, it further enabled imaging-guided precision PTT ablation, even for those unsatisfactory tumor types (cSCC) through exogenously delivering H2O2.

Electrochemical Detection of Circulating Tumor Cells Based on DNA Generated Electrochemical Current and Rolling Circle Amplification

Circulating tumor cells (CTCs) are important indicators for tumor diagnosis and tumor metastasis. However, the extremely low levels of CTCs in peripheral blood challenges the precise detection of CTCs. Herein, we report DNA generated electrochemical current combined with rolling circle amplification (RCA) as well as magnetic nanospheres for highly efficient magnetic capture and ultrasensitive detection of CTCs. The antiepithelial cell adhesion molecule (EpCAM) antibody-modified magnetic nanospheres were used to capture and enrich CTCs. The following binding of an aptamer onto the CTC surface and the subsequent RCA assembled a significant amount of DNA molecules onto the electrode. The reaction of the DNA molecules with molybdate can then form redox molybdophosphate and produce an electrochemical current. Using the breast cancer cell MCF-7 as a model, the sensor displays good performances toward detection of MCF-7 that was spiked into peripheral blood. The signal amplification strategy integrated with a magnetic nanosphere platform exhibits good performance in the efficient capture and detection of CTCs, which may find wide potential in cancer diagnostics and therapeutics.

Direct Plasmon-Enhanced Electrochemistry for Enabling Ultrasensitive and Label-Free Detection of Circulating Tumor Cells in Blood

In this work, we developed a simple electrochemical method for ultrasensitive and label-free detection of circulating tumor cells (CTCs) based on direct plasmon-enhanced electrochemistry (DPEE). After plasmonic gold nanostars (AuNSs) were modified on the glassy carbon (GC) electrode, the aptamer probe was immobilized on the AuNSs surface, which can selectively capture the CTCs in samples. Upon localized surface plasmon resonance (LSPR) excitation, the electrochemical current response can be enhanced remarkably due to efficient hot electrons transport from AuNSs to the external circuit. The captured cells on the AuNSs surface will influence the hot electrons transport efficiency, leading to a decreased current response. Using ascorbic acid (AA) as the electroactive probe, it was found that the current responses of the AuNSs/GC electrode upon light irradiation decrease with the cell concentration. Due to the special molecular recognition of the aptamer and enhanced electrochemical performance of the plasmon, the proposed method enables an ultrasensitive and label-free detection of CTCs with excellent selectivity. The experimental results show that CCRF-CEM cell concentrations as low as 5 cells/mL can be successfully detected, which is superior to most reported work up to now. Using the present method, MCF-7 cells as low as 10 cells/mL can be also successfully detected, indicating the universality of the proposed method for CTCs detection. Furthermore, the cytosensor can successfully distinguish CTCs from normal cells in blood samples. The as-proposed strategy provides a promising application of DPEE in the development of novel biosensors for nondestructive analysis of biological samples.

Porous Graphene Oxide Enhanced Aptamer Specific Circulating-Tumor-Cell Sensing Interface on Light Addressable Potentiometric Sensor: Clinical Application and Simulation

The circulating-tumor-cell (CTC) specific aptamer is believed to be a power recognition factor to realize clinical CTC assay. However, the limited sensing range is still one of the challenges in its real application. The porous-graphene-oxide (PGO) enhanced aptamer specific CTC sensing interface is studied on the platform of light-addressable-potentiometric-sensor (LAPS) to provide a clinical available method for CTC detection. The underlying mechanism of this sensing interface on LAPS is modeled and simulated. It is confirmed to be a promising candidate for CTC assay by the linear responding for 5-5000 spiked cells, as well as the satisfactory sensitivity for clinical samples.

A Fluorescent Cocktail Strategy for Differentiating Tumor, Inflammation, and Normal Cells by Detecting mRNA and H2O2

Accurately distinguishing tumors from noncancerous inflammation and normal tissues is hugely significent for tumor diagnosis and therapy. However, tumor and inflammatory tissues have similar pathologic characteristics in their microenvironment, making differentiation very difficult. Here, a fluorescent cocktail nanoparticle capable of simultaneously detecting intracellular mRNA and H₂O₂ was designed to differentiate tumors from nontumor cells. To detect targeted mRNA in living cells, a DNA probe was generated using the fluorescence resonance energy transfer (FRET) principle. A pH-responsive amphiphilic polymer was synthesized to realize the transportation of the DNA probe. In addition, the polymer was conjugated with a coumarin-boronic acid ester (Cou-BE) H₂O₂ probe. According to the change in the fluorescence of Cou-BE, tumor and inflammatory cells could be distinguished from normal cells owing to their high concentration of H₂O₂. Because of the different concentrations of tumor-related mRNA in tumor and nontumor cells, the fluorescence intensity of the DNA probe-loaded nanoparticles inside tumor cells was different from that inside inflammatory cells. Therefore, our fluorescent cocktail strategy could discriminate simultaneously tumor, inflammation, and normal cells through the cooperative detection of intracellular mRNA and H₂O₂, which demonstrated potential application value in biomedical research and clinical diagnosis.

Near-Infrared Fluorescent Ag2S Nanodot-Based Signal Amplification for Efficient Detection of Circulating Tumor Cells

The level of circulating tumor cells (CTCs) plays a critical role in tumor metastasis and personalized therapy, but it is challenging for highly efficient capture and detection of CTCs because of the extremely low concentration in peripheral blood. Herein, we report near-infrared fluorescent Ag₂S nanodot-based signal amplification combing with immune-magnetic spheres (IMNs) for highly efficient magnetic capture and ultrasensitive fluorescence labeling of CTCs. The near-infrared fluorescent Ag₂S nanoprobe has been successfully constructed through hybridization chain reactions using aptamer-modified Ag₂S nanodots, which can extremely improve the imaging sensitivity and reduce background signal of blood samples. Moreover, the antiepithelial-cell-adhesion-molecule (EpCAM) antibody-labeled magnetic nanospheres have been used for highly capture rare tumor cells in whole blood. The near-infrared nanoprobe with signal amplification and IMNs platform exhibits excellent performance in efficient capture and detection of CTCs, which shows great potential in cancer diagnostics and therapeutics.

Star polymer-based unimolecular micelles and their application in bio-imaging and diagnosis

As a novel kind of polymer with covalently linked core-shell structure, star polymers behave in nanostructure in aqueous medium at all concentration range, as unimolecular micelles at high dilution condition and multi-micelle aggregates in other situations. The unique morphologies endow star polymers with excellent stability and functions, making them a promising platform for bio-application. A variety of functions including imaging and therapeutics can be achieved through rational structure design of star polymers, and the existence of plentiful end-groups on shell offers the opportunity for further modification. In the last decades, star polymers have become an attracting platform on fabrication of novel nano-systems for bio-imaging and diagnosis. Focusing on the specific topology and physicochemical properties of star polymers, we have reviewed recent development of star polymer-based unimolecular micelles and their bio-application in imaging and diagnosis. The main content of this review summarizes the synthesis of integrated architecture of star polymers and their self-assembly behavior in aqueous medium, focusing especially on the recent advances on their bio-imaging application and diagnosis use. Finally, we conclude with remarks and give some outlooks for further exploration in this field.