Recent Advances in Carbon Nanodots: Properties and Applications in Cancer Diagnosis and Treatment

Carbon nanomaterials as electrochemical sensors for theophylline: a review

Theophylline (TP) is a methylxanthine derivative, which serves as a valuable compound in treating respiratory disorders and acts as a bronchodilator agent. However, TP has a limited therapeutic range (20-100 μmol L-1), demanding precise monitoring to prevent potential drug toxicity even with slight level fluctuations during treatment. Thus, to overcome this limitation, electrochemical methods have been extensively used due to their efficacy in achieving sensitivity, selectivity, and accuracy. In the context of electrochemical sensors, nanocarbon-based materials have gained widespread recognition for their extensive applications. Therefore, this review aims to explore the latest advancements in carbon-based electrodes particularly used for the precise determination of TP through electrochemical methods. The results are expected to provide insights into the profound significance of the methods in enhancing the accuracy and sensitivity for the detection of TP.

The restructure of Au@Ag nanorods for cell imaging with dark-field microscope

The facile and noninjurious image of cells with high resolution and low toxicity is essential since imaging can offer rich and direct information and insights into metabolic activities, clinical diagnosis, drug delivery and cancer therapy. In this contribution, a smart imaging probe was employed as a contrast agent for dark-field cell imaging. Au core/Ag shell nanorods (Au@Ag NRs) that characterized by X-ray diffraction and X-ray photoelectron spectroscopy, formed Au@Ag@AgI NRs when exposed to iodine, which greatly enhanced the light scattering of nanorods. Herein, the silver shell acted as the response element for iodine as well as the protective agent for Au core. When conjugated with folate, the nanorods can be used to image human cervical cancer cells (HeLa cells) under a dark-field microscope. Nanorods were demonstrated with excellent tumor cellular uptake ability without obvious cytotoxicity, making them ideal candidates in biosensing and bioimaging applications.

Simultaneous detection of dual biomarkers using hierarchical MoS2 nanostructuring and nano-signal amplification-based electrochemical aptasensor toward accurate diagnosis of prostate cancer

Accurate and reliable quantification of tumor biomarkers in clinical samples is of vital importance for early stage diagnosis and treatment of cancer. However, a poor specificity of prostate specific antigen (PSA) testing alone fostering overdetection and overtreatment, remains a great controversy in prostate cancer (PCa) screening. Here we report an electrochemical aptasensor using hierarchical MoS₂ nanostructuring and SiO₂ nano-signal amplification for simultaneous detection of dual PCa biomarkers, PSA and sarcosine, to enhance the diagnostic performance of PCa. In this strategy, hierarchical flower-like MoS₂ nanostructures as functional interface accelerated intermolecular accessibility and improved DNA hybridization efficiency. Moreover, the spherical SiO₂ nanoprobe that conjugated with both electroactive tags and DNA probes, allowed effective electrochemical signal amplification. By deliberately designing different hybridization modes, we individually implemented the optimization of PSA and sarcosine sensing system. Based on this, simultaneous determination of PSA and sarcosine was achieved, with limit of detection (LOD) down to 2.5 fg/mL and 14.4 fg/mL, respectively, as well as excellent selectivity. More importantly, using this approach, we could directly differentiate cancer patients with healthy ones for clinical serum samples. The ultrasensitive biosensor provides single-step analysis with simple operation and a small sample volume (∼12 μL), shedding new light on accurate diagnosis and early-detection of cancer in clinical applications.

Charge Neutralization Strategy to Construct Salt-Tolerant and Cell-Permeable Nanoprobes: Application in Ratiometric Sensing and Imaging of Intracellular pH

Intracellular pH homeostasis is essential for the survival and function of biological cells. Negatively charged molecular probes, such as pyranine (HPTS), tend to exhibit poor salt tolerance and unsatisfactory cell permeability, limiting their widespread use in intracellular assays. Herein, we explored a charge neutralization strategy using multicharged cationic nanocarriers for an efficient and stable assembly with the pH-sensitive HPTS. Through immobilization and neutralization with poly(allylamine hydrochloride)-stabilized red-emitting gold nanoclusters (PAH-AuNCs), the resulting nanoprobes (HPTS-PAH-AuNCs) offered improved salt tolerance, satisfactory cell permeability, and dual-emission properties. The fluorescence ratio exhibited a linear response over the pH range of 3.0-9.0. Moreover, the proposed HPTS-PAH-AuNCs were successfully applied to determine and visualize lysosomal pH variations in living cells, which indicated great potential for biosensing and bioimaging applications in living systems. Benefiting from the charge neutralization strategy, various types of probes can be expected to achieve broader analytical applications.

Recent Advances in Fluorescence Imaging of Pulmonary Fibrosis in Animal Models

Pulmonary fibrosis (PF) is a lung disease that may cause impaired gas exchange and respiratory failure while being difficult to treat. Rapid, sensitive, and accurate detection of lung tissue and cell changes is essential for the effective diagnosis and treatment of PF. Currently, the commonly-used high-resolution computed tomography (HRCT) imaging has been challenging to distinguish early PF from other pathological processes in the lung structure. Magnetic resonance imaging (MRI) using hyperpolarized gases is hampered by the higher cost to become a routine diagnostic tool. As a result, the development of new PF imaging technologies may be a promising solution. Here, we summarize and discuss recent advances in fluorescence imaging as a talented optical technique for the diagnosis and evaluation of PF, including collagen imaging, oxidative stress, inflammation, and PF-related biomarkers. The design strategies of the probes for fluorescence imaging (including multimodal imaging) of PF are briefly described, which can provide new ideas for the future PF-related imaging research. It is hoped that this review will promote the translation of fluorescence imaging into a clinically usable assay in PF.

Recent Advances in Fluorescence Imaging of Traumatic Brain Injury in Animal Models

Traumatic brain injury (TBI) is one of the top three specific neurological disorders, requiring reliable, rapid, and sensitive imaging of brain vessels, tissues, and cells for effective diagnosis and treatment. Although the use of medical imaging such as computed tomography (CT) and magnetic resonance imaging (MRI) for the TBI detection is well established, the exploration of novel TBI imaging techniques is of great interest. In this review, recent advances in fluorescence imaging for the diagnosis and evaluation of TBI are summarized and discussed in three sections: imaging of cerebral vessels, imaging of brain tissues and cells, and imaging of TBI-related biomarkers. Design strategies for probes and labels used in TBI fluorescence imaging are also described in detail to inspire broader applications. Moreover, the multimodal TBI imaging platforms combining MRI and fluorescence imaging are also briefly introduced. It is hoped that this review will promote more studies on TBI fluorescence imaging, and enable its use for clinical diagnosis as early as possible, helping TBI patients get better treatment and rehabilitation.

Multi-stage responsive peptide nanosensor: Anchoring EMT and mitochondria with enhanced fluorescence and boosting tumor apoptosis

Epithelial-mesenchymal transition (EMT) is closely related to tumor metastasis and invasion. Thereinto, mesenchymal tumor mitochondria are the critical target for tumor inhibition. Therefore, real-time in vivo monitoring of EMT as well as inhibiting mesenchymal tumor mitochondria is of great diagnosis and therapy significance. Herein, we construct a multi-stage recognition and morphological transformable self-assembly-peptide nano biosensor ^NDRP which can response the EMT marker and specifically damage the mesenchymal tumor cell in vivo. This nano-molar-affinity sensor is designed and screened with sensitive peptides containing a molecular switching which could be specifically triggered by the receptor to achieve the vesicle-to-fibril transformation in living system with enhanced fluorescent signal. ^NDRP nanosensor could target the tumor lesion in circulatory system, recognize mesenchymal tumor marker DDR2 (Discoidin domain receptor 2) in cellular level and specifically achieve mitochondria in subcellular level as well as damaged mitochondria which could be applied as a in vivo theranostic platform.

Recent advances in the modification of carbon-based quantum dots for biomedical applications

Carbon-based quantum dots (CDs) are mainly divided into two sub-groups; carbon quantum dots (CQDs) and graphene quantum dots (GQDs), which exhibit outstanding photoluminescence (PL) properties, low toxicity, superior biocompatibility and facile functionalization. Regarding these features, they have been promising candidates for biomedical science and engineering applications. In this work, we reviewed the efforts made to modify these zero-dimensional nano-materials to obtain the best properties for bio-imaging, drug and gene delivery, cancer therapy, and bio-sensor applications. Five main surface modification techniques with outstanding results are investigated, including doping, surface functionalization, polymer capping, nano-composite and core-shell structures, and the drawbacks and challenges in each of these methods are discussed.

Dual Photoluminescence Emission Carbon Dots for Ratiometric Fluorescent GSH Sensing and Cancer Cell Recognition

We developed a facile strategy for the fabrication of dual-emission carbon nanodots (CDs) and demonstrated their applications for ratiometric glutathione (GSH) sensing and for differentiating cancer cells from normal cells. Dual-emission CDs were synthesized using a simple hydrothermal treatment of alizarin carmine as the carbon source, manifesting intriguing dual-emission behavior at 430 and 642 nm. With increasing GSH concentration, the fluorescence band at 430 nm increased gradually, whereas that at 642 nm decreased slightly. With monitoring of the intrinsic ratiometric fluorescence variation (I_430nm/I_642nm), as-prepared CDs were developed as an effective platform for ratiometric fluorescent GSH sensing, with a linear range of 1-10 to 25-150 μM and a detection limit of 0.26 μM. More importantly, confocal fluorescent imaging of cancer cells and normal cells indicated that obtained CDs could be implemented as an effective tool to visualize cancer cells with overexpressing GSH.

A facile deoxyuridine/biotin-modified molecular beacon for simultaneous detection of proteins and nucleic acids via a label-free and background-eliminated fluorescence assay

Simultaneous detection of different types of cancer biomarkers (nucleic acids and proteins) could facilitate early diagnosis of cancer and clinical treatment. Herein, a simultaneous detection platform of proteins and nucleic acids has been developed using a single substrate probe combining a label-free and background-eliminated fluorescence assay. Telomerase and telomerase RNA (TR) were chosen as the models. The molecular beacon (dU-BIO-HP) that contains deoxyuridine/biotin in its side arm, a TR recognition sequence in the loop and a telomerase substrate primer at the stem end was ingeniously designed. In the presence of telomerase, the stem of dU-BIO-HP is elongated by the addition of telomere repeats complementary to the assistant DNA. Furthermore, the formed dsDNA performed as engaging primers to initiate a SDA reaction, generating abundant G-quadruplex monomers. Similarly, on TR, the hybridization between TR and dU-BIO-HP can open its stem, triggering another SDA reaction, producing abundant short ssDNAs. With the G-quadruplex binding with ZnPPIX and ssDNA binding with SG for specific fluorescence responses, the label-free multiple detection can be achieved. In our strategy, the deoxyuridine of dU-BIO-HP acts as a barrier to block the DNA extension due to its strong inhibitory effects on DNA polymerase activity and to make sure that the two SDA reactions occurred independently. The biotin of dU-BIO-HP enables the reduction of the background from the binding between SG, ZnPPIX and dU-BIO-HP through streptavidin-biotin interaction. This method showed an excellent sensitivity with telomerase and TR detection limit of 2.18 HeLa cells per mL and 0.16 × 10^-12 M, respectively. Furthermore, the telomerase and TR in different cell lines have been evaluated as powerful tools for biomedical research and clinical diagnosis.

Review of Carbon and Graphene Quantum Dots for Sensing

Carbon and graphene quantum dots (CQDs and GQDs), known as zero-dimensional (0D) nanomaterials, have been attracting increasing attention in sensing and bioimaging. Their unique electronic, fluorescent, photoluminescent, chemiluminescent, and electrochemiluminescent properties are what gives them potential in sensing. In this Review, we summarize the basic knowledge on CQDs and GQDs before focusing on their application to sensing thus far followed by a discussion of future directions for research into CQDs- and GQD-based nanomaterials in sensing. With regard to the latter, the authors suggest that with the potential of these nanomaterials in sensing more research is needed on understanding their optical properties and why the synthetic methods influence their properties so much, into methods of surface functionalization that provide greater selectivity in sensing and into new sensing concepts that utilize the virtues of these nanomaterials to give us new or better sensors that could not be achieved in other ways.