Visualizing Breast Cancer Cell Proliferation and Invasion for Assessing Drug Efficacy with a Fluorescent Nanoprobe

Graphene oxide-functionalized molecular beacon for real-time interference-free detection of Ki-67 mRNA in living cells

Molecular beacons (MBs) based on hairpin-shaped oligonucleotides are captivating owing to their capability to enable effective real-time detection of cytosolic mRNA in living cells. However, DNase in the nucleus and lysosome could induce the degradation of oligonucleotides in MBs, leading to the generation of false-positive signals. Herein, a graphene oxide (GO) nanosheet was applied as a nanocarrier for MBs to greatly enhance the anti-interference of the easily designed nanoprobe. Advantageously, the absorption capacity of GO for MBs increased with the decrease in pH values, providing the MB-GO nanoprobe with the ability to detect the expression of cytosolic Ki-67 mRNA without interference from DNase Ⅱ in lysosomes. Moreover, the size of GO nanosheets was considerably higher than that of the nuclear pore complex (NPC), which prevented nanoprobes from transition through the NPCs, thereby avoiding the generation of false-positive signals in the nucleus. Altogether, the present work affords a convenient approach for the successful detection of Ki-67 mRNA expression in the cytosol without interference from DNase Ⅰ/Ⅱ in the nucleus/lysosome, which may be potentially further applied for the detection of other cytosolic RNAs.

Photodynamic therapy of cancer using graphene nanomaterials

INTRODUCTION

High incidence and fatality rates of cancer remain a global challenge. The success of conventional treatment modalities is being questioned on account of adverse effects. Photodynamic therapy (PDT) is a potential alternative. It utilizes a combination of photosensitizer (PS), light and oxygen to target the tissues locally, thereby minimizing the damage to neighboring healthy tissues. Conventional PSs suffer from poor selectivity, high hydrophobicity and sub-optimal yield of active radicals. Graphene nanomaterials (GNs) exhibit interesting particulate and photophysical properties in the context of their use in PDT.

AREA COVERED

We focus on describing the mechanistic aspects of PDT-mediated elimination of cancer cells and the subsequent development of adaptive immunity. After covering up-to-date literature on the significant enhancement of PDT capability with GNs, we have discussed the probability of combining PDT with chemo-, immuno-, and photothermal therapy to make the treatment more effective.

EXPERT OPINION

GNs can be synthesized in various size ranges, and their biocompatibility can be improved through surface functionalization and doping. These can be used as PS to generate ROS or conjugated with other PS molecules for treating deep-seated tumors. With increasing evidence on biosafety, such materials offer hope as antitumor therapeutics.

Enzyme-assisted amplification of target cycle triggers the unlocking of locked hairpin probes for let-7a detection

The detection of miRNA in cells is difficult owing to its substantially low cellular content. Therefore, developing a highly sensitive sensor to detect cellular miRNA remains a significant challenge. Herein, we report an enzyme-assisted biosensor with target cycle amplification that can trigger the unlocking of locked hairpin probes for sensitive and robust let-7a gene detection. In the research, three kinds of hairpin probes were skillfully designed. The hairpin probe comprises a complementary sequence of a target, primer, and recognition site of Nt. BbvCI restriction endonucleases. In addition, the alternating synergistic impact of polymerase and the nicking enzyme generates considerable triggers to unlock the locked hairpin probe LH1, consequently triggering a subsequent circulating strand displacement reaction to form a stable H1-H2 double strand to ensure sufficient distance between a fluorophore on H1 and a quenching group on bolt DNA (bDNA), and resulting in the recovery of fluorescence. Furthermore, this process does not require complicated operation procedures and instruments, and the target gene let-7a can be sensitively detected. Specifically, the detection limit of the biosensor is as low as 160 fM, and its linear range is 0.5 pM-250 nM. Moreover, this biosensor can be employed to detect let-7a in human serum with good selectivity.

In situ growth of TiO2/Ti3C2 MXene Schottky heterojunction as a highly sensitive photoelectrochemical biosensor for DNA detection

In this work, a heterojunction composed of a TiO₂ nanosheet and layered Ti₃C₂ was synthesized by directly growing TiO₂ in Ti₃C₂ MXene. Compared with pure TiO₂, TiO₂/Ti₃C₂ composites had increased surface area, and a light absorption range that extended from ultraviolet to visible light, which greatly extended the life of photogenerated carriers. A photoelectrochemical biosensor for DNA detection was constructed based on the TiO₂/Ti₃C₂ heterogeneous structure, which was comprehensively studied based on photocurrent responses. In the absence of the target, the CdSe QDs were close to the surface of the electrode, resulting in enhanced sensitization and increased photocurrent. In the presence of the target, the photocurrent decreases due to the formation of rigid double strands with the probe DNA, which caused the CdSe QDs to be far away from the electrode surface. The sensor had stability and sensitivity for DNA detection in the range of 10 nM-10 fM, and the lower detection limit was 6 fM. Its outstanding characteristics also provided ideas for detecting various other target DNA for early diagnosis of various diseases.

Novel Au-Se Nanoprobes for Specific Thrombin Detection in Diagnosis of Lung Cancer

Thrombin is associated with malignant tumors and promotes tumor development, metastasis, and angiogenesis, therefore its identification especially in lung cancer cells is crucial. Because the interference of in vivo biothiols caused false positive findings with prior gold fluorescent nanoprobes, in this manuscript, an Au-selenol(Se) nanoprobe (5-FAM-peptide-Se-AuNPs) that could specifically detect thrombin was designed and compared to traditional Au-S nanoprobes. For reaching this goal, fluorophore-bearing thrombin-specific peptide containing selenol at the end was synthesized. The nanoprobe may be broken by thrombin to regain its fluorescence in lung cancer cells, allowing for high-sensitivity thrombin detection. Since the Au-Se bond is more stable than the Au-S bond, the accuracy of the detection results can be guaranteed. The probe synthesis method is simple and cost-effective, as well as having high biocompatibility. Low concentrations of thrombin can be detected and imaged in lung cancer cells. The synthetic method of this probe opens up new avenues for the application of Au-Se bonds.

Integrin α2β1 Targeting DGEA-Modified Liposomal Doxorubicin Enhances Antitumor Efficacy against Breast Cancer

Breast cancer was the leading cause of newly diagnosed cases of tumors in 2020, ranking as the second highest cause of female death. Chemotherapy remains the conventional treatment of choice for breast tumors in most clinical cases. However, it is often accompanied by a poor prognosis and severe side effects, resulting from an insufficient accumulation of the drug at tumor sites and an unsystematic distribution of the drug across the body. Inspired by the fact that breast tumor cells overexpress integrin α2β1 on the surface, we designed and constructed an integrin α2β1 targeting DGEA-modified liposomal doxorubicin (DGEA-Lipo-DOX) platform for application in breast cancer therapy. The DGEA-Lipo-DOX was stable with a uniform particle size of 121.1 ± 3.8 nm and satisfactory drug encapsulation. Demonstrated in vitro and in vivo, the constructed platform exhibited improved antitumor ability. The DGEA-Lipo-DOX showed 4-fold enhanced blood circulation and 6-fold increased accumulation of DOX at the tumor sites compared to those of free DOX, resulting in a significantly enhanced antitumor efficacy in tumor-bearing mice. A preliminary safety evaluation suggested that the systemic toxicity of DOX was relieved by DGEA-Lipo delivery. Collectively, binding integrin α2β1 by DGEA may represent an alternative therapeutic strategy for potentially safer breast cancer treatment.

A AuNP-capped cage fluorescent biosensor based on controlled-release and cyclic enzymatic amplification for ultrasensitive detection of ATP

Gold nanodevices have attracted extensive interest in the detection of specific targets within cells. However, constructing gold sensing devices that can be activated by the simulation of remote applications remains a huge challenge. Here, we report a Au nanoparticle (AuNP)-capped cage fluorescent biosensor based on controlled-release and Exonuclease III (Exo III) assisted cyclic enzymatic amplification that can be activated by adenosine triphosphate (ATP). In the system, AuNPs were used as the building blocks to cap the pores of Au nanocages (AuNCs) loaded with Rhodamine B (RhB) molecules through the hybridization of DNA. The RhB fluorescent molecules were finally released with the help of Exo III in the presence of ATP for detection purposes. Ultimately, the biosensor leads to a wide linear ATP detection range from 1.0 × 10-9 to 1.0 × 10-7 M with a limit of detection (LOD) down to 0.88 nM. In addition, it also has good selectivity for ATP to distinguish between ATP and ATP analogues such as cytidine triphosphate (CTP), guanosine triphosphate (GTP), and uridine triphosphate (UTP). Therefore, as a convenient and sensitive biosensor, it is expected to be widely used in the biomedical field.

An Au-Se nanoprobe for the evaluation of the invasive potential of breast cancer cells via imaging the sequential activation of uPA and MMP-2

Urokinase-type plasminogen activator (uPA) has been shown to activate matrix metalloproteinase-2 (MMP-2) that leads to the migration and invasion of breast cancer cells. Overexpressed uPA and MMP-2 are regarded as signs of malignant tumors in clinical practice. Therefore, real-time monitoring of the sequential activation of these two signal molecules may have important implications for the evaluation of the invasive potential and tumor progression of breast cancer. However, due to the complicated intracellular environment, visualizing the dynamic changes of protein expression levels in living cells with a noninvasive method is still a great challenge. Here, a novel gold-selenium (Au-Se) fluorescent nanoprobe with excellent selectivity and strong anti-interference capability was designed for the simultaneous in situ imaging of uPA and MMP-2 and real-time monitoring of their changes in living cells. The imaging results demonstrated that the nanoprobe achieved a better prevention of glutathione interference compared to the conventional Au-S nanoprobe, thus it could be applied to actually reflect the expression level of uPA and MMP-2 in different breast cancer cells. Furthermore, the Au-Se nanoprobe could visually present the activation process of the two signal molecules, which play a dual role of insuring the invasiveness evaluation of breast cancer cells. Overall, our work offers a visual biomarker detection method for the judgment of the degree of breast cancer malignancy, and also provides an effective strategy to investigate the relationships among signal molecules of other signaling pathways in the future.

An RNase H-powered DNA walking machine for sensitive detection of RNase H and the screening of related inhibitors

Ribonuclease H (RNase H), an intracellular ribonuclease, plays a crucial role in cellular processes and especially relates to many disease processes. Here, we report a novel signal amplification strategy based on an RNase H-powered DNA walking machine for specific and sensitive RNase H activity detection. The DNA walking machine is composed of a small quantity of DNA walker strands and abundant FAM-labeled DNA-RNA chimeric strands on a single gold nanoparticle (AuNP). RNase H can specifically degrade the RNA fragment in a DNA-RNA hybrid duplex and trigger the autonomous movement of a DNA walker strand on the AuNP surface. During this process, each step of the walking can release the FAM-labeled RNA from the surface of the AuNP, realizing the signal amplification for RNase H sensing. This method has been successfully utilized for RNase H activity detection in a complex system and applied for screening of related inhibitors. Therefore, our RNase H-powered DNA walking machine gives a novel platform for RNase H activity detection and RNase H-associated drug discovery.

Boosting Cancer Therapy with Organelle-Targeted Nanomaterials

The ultimate goal of cancer therapy is to eliminate malignant tumors while causing no damage to normal tissues. In the past decades, numerous nanoagents have been employed for cancer treatment because of their unique properties over traditional molecular drugs. However, lack of selectivity and unwanted therapeutic outcomes have severely limited the therapeutic index of traditional nanodrugs. Recently, a series of nanomaterials that can accumulate in specific organelles (nucleus, mitochondrion, endoplasmic reticulum, lysosome, Golgi apparatus) within cancer cells have received increasing interest. These rationally designed nanoagents can either directly destroy the subcellular structures or effectively deliver drugs into the proper targets, which can further activate certain cell death pathways, enabling them to boost the therapeutic efficiency, lower drug dosage, reduce side effects, avoid multidrug resistance, and prevent recurrence. In this Review, the design principles, targeting strategies, therapeutic mechanisms, current challenges, and potential future directions of organelle-targeted nanomaterials will be introduced.

A gold-selenium-bonded nanoprobe for real-time in situ imaging of the upstream and downstream relationship between uPA and MMP-9 in cancer cells

A novel Au-Se nanoprobe with remarkable anti-interference ability for glutathione was developed for real-time in situ monitoring of the upstream and downstream regulatory relationship between uPA and MMP-9 proteins in the pathway.

A Suzuki-Miyaura method for labelling proliferating cells containing incorporated BrdU

The 5-bromo-2'-deoxyuridine (BrdU) incorporation cell proliferation assay is the most commonly used method for assessing DNA replication. The current detection of BrdU in cells relies on antibody immunostaining, but has various limitations including low antibody specificity and poor tissue penetration. In this study, we utilised a Suzuki-Miyaura reaction to develop a chemical method to label cellular BrdU with fluorescent boronic acid probes. The coupling conditions were optimised for complex cellular environments, and the key observation was the need to use oxygen scavengers and zerovalent palladium to prevent side reactions and increase the rate of coupling. The reliability and specificity of the BrdU Suzuki-Miyaura labelling method were verified under various biological conditions. The applicability of the BrdU Suzuki-Miyaura labelling methodology was also investigated, and we show that labelling cellular BrdU is highly sensitive and reliable, which is comparable to the ideal performance of BrdU immunostaining. Moreover, the Suzuki-Miyaura reaction protocol provides high BrdU recognition specificity. Taken together, the BrdU Suzuki-Miyaura labelling protocol provides an attractive alternative to the more traditional cell proliferation assay.

Gold nanoparticle based fluorescent oligonucleotide probes for imaging and therapy in living systems

Gold nanoparticles (AuNPs) with unique physical and chemical properties have become an integral part of research in nanoscience.

Enhancement of mitochondrial ROS accumulation and radiotherapeutic efficacy using a Gd-doped titania nanosensitizer

Radiotherapy is an extensively used treatment modality in the clinic and can kill malignant cells by generating cytotoxic reactive oxygen species (ROS). Unfortunately, excessive dosages of radiation are typically required because only a small proportion of the radiative energy is adsorbed by the soft tissues of a tumor, which results in the nonselective killing of normal cells and severe systemic side effects. An efficient nanosensitizer that makes cancer cells more sensitive to radiotherapy under a relatively low radiation dose would be highly desirable.

Methods: In this study, we developed a Gd-doped titania nanosensitizer that targets mitochondria to achieve efficient radiotherapy. Upon X-ray irradiation, the nanosensitizer triggers a “domino effect” of ROS accumulation in mitochondria. This overabundance of ROS leads to mitochondrial permeability transition and ultimately irreversible cell apoptosis. Confocal laser imaging, western blotting and flow cytometry analysis were used to explore the biological process of intrinsic apoptosis induced by the nanosensitizer. Clonogenic survival assay, cell migration and invasion experiments were employed to evaluate the radiosensitizing effect of the nanosensitizer in vitro. Finally, to evaluate the therapeutic outcome of the nanosensitizer in vivo, MCF-7 tumor model was used.

Results: Confocal laser images and western blotting data demonstrated that the nanosensitizer in conjunction with X-ray irradiation could induce cell apoptosis in ROS-mediated apoptotic signal pathways. A clonogenic survival assay revealed that cells treated with the prepared nanosensitizer exhibited a lower number of viable cell colonies than that of the nontargeted group under X-ray irradiation. Notably, with only a single dose of radiotherapy, the mitochondria-targeted nanosensitizer elicited the complete ablation of tumors in a mouse model.

Conclusion: The designed nanosensitizer in combination with X-ray radiation exposure could be used for radiotherapy against cancer in living cells and in vivo. Moreover, the nanosensitizer with mitochondria targeting played a pivotal role in triggering a “domino effect” of ROS and cell apoptosis. The current strategy could provide new opportunities in designing efficient radiosensitizers for future cancer therapy.

Simultaneous Fluorescence Visualization of Epithelial-Mesenchymal Transition and Apoptosis Processes in Tumor Cells for Evaluating the Impact of Epithelial-Mesenchymal Transition on Drug Efficacy

The epithelial-mesenchymal transition (EMT) process plays a pivotal role in acquiring invasive and metastatic properties and has been recognized as a crucial driver of epithelial-derived tumor malignancies. It is necessary to determine the role of EMT in promoting or suppressing carcinoma progression through investigating the relationship between EMT and apoptosis. We designed a multicolor fluorescent nanoprobe for simultaneously imaging the epithelial biomarker E-cadherin mRNA, the mesenchymal marker vimentin mRNA, and the apoptotic marker caspase-3. EMT and apoptosis progresses could be visually detected, which were used to study the effect of EMT on apoptosis and further assess the influence of EMT on drug efficacy in different cancer cells. We believe the designed nanoprobe can offer a new strategy for visualizing EMT and apoptosis in tumor cells and will be a promising tool to investigate the efficiency of drugs targeting EMT-related therapies in living cells.

Au-Se-Bond-Based Nanoprobe for Imaging MMP-2 in Tumor Cells under a High-Thiol Environment

The gold nanosensors based on the Au-S bond have been widely applied to biochemical detections. However, signal distortion caused by biothiols has been seldom mentioned and urgently needs to be solved. Herein, we designed a novel but easily assembled gold nanoprobe by coupling a selenol-modified peptide with FITC onto the gold nanoparticle's surface via an Au-Se bond for fluorescence imaging of a tumor marker matrix, metalloproteinases 2 (MMP-2). Compared to the Au-S probes, the Au-Se probes display high thermal stability and a very good anti-interference ability toward glutathione under simulated physiological conditions. More importantly, the Au-Se nanoprobe exhibits a high-fidelity fluorescent signal toward MMP-2, effectively avoiding interference caused by high levels of thiol compounds in vivo. In addition, in vivo experiments further proved that no significant signal intensity change for the tumor cells treated by the Au-Se probes was observed before and after eliminating glutathione. Hence, we believe such Au-Se probes with in vivo glutathione interfering resistance offer new routes and perspectives in biology and medicine in the future.

A Universal Upconversion Sensing Platform for the Sensitive Detection of Tumour-Related ncRNA through an Exo III-Assisted Cycling Amplification Strategy

Here, a sensitive and universal noncoding RNA (ncRNA) upconversion sensing nanoplatform is developed. Gold nanoparticles bearing one hairpin DNA (Hp) molecule are conjugated to the linker DNA modified NaYF₄ :Yb, Er@NaYF₄ upconversion nanoparticles by DNA hybridization, leading to quenching of the upconversion emission through fluorescence resonance energy transfer. A signal DNA (SDNA) sequence is designed to open Hp, recovering the upconversion emission. To achieve universality and high sensitivity of the nanoprobe, an exonuclease III (Exo III)-assisted cycling amplification strategy is introduced. A multifunctional hairpin DNA (mHp) containing ncRNA recognition sequence and SDNA sequence is designed to recognize ncRNA and trigger Exo III as a biocatalyst to stepwise disintegrate itself, releasing both ncRNA and SDNA. The released ncRNA can be reused to release more SDNA, which greatly improves the sensing sensitivity. By changing the recognition portion of mHp, various ncRNA can be detected. The sensitive detection of both homeobox (HOX) transcript antisense RNA segment and miR-21 is achieved with this novel strategy, even in human serum, indicating the universality and sensitivity of the proposed strategy. Additionally, the expression level of miR-21 in human breast cancer cell (MCF-7) lysate is successfully measured, suggesting its potential in clinical diagnosis.

A gold nanoparticle-based four-color proximity immunoassay for one-step, multiplexed detection of protein biomarkers using ribonuclease H signal amplification

A gold nanoparticle-based four-color fluorescence proximity immunoassay was developed for multiplexed analysis of protein biomarkers using ribonuclease H signal amplification.