Tracking and Finding Slow-Proliferating/Quiescent Cancer Stem Cells with Fluorescent Nanodiamonds

Fluorescent Probes for Disease Diagnosis

The identification and detection of disease-related biomarkers is essential for early clinical diagnosis, evaluating disease progression, and for the development of therapeutics. Possessing the advantages of high sensitivity and selectivity, fluorescent probes have become effective tools for monitoring disease-related active molecules at the cellular level and in vivo. In this review, we describe current fluorescent probes designed for the detection and quantification of key bioactive molecules associated with common diseases, such as organ damage, inflammation, cancers, cardiovascular diseases, and brain disorders. We emphasize the strategies behind the design of fluorescent probes capable of disease biomarker detection and diagnosis and cover some aspects of combined diagnostic/therapeutic strategies based on regulating disease-related molecules. This review concludes with a discussion of the challenges and outlook for fluorescent probes, highlighting future avenues of research that should enable these probes to achieve accurate detection and identification of disease-related biomarkers for biomedical research and clinical applications.

Deciphering the functional landscape and therapeutic implications of noncoding RNAs in the TGF-β signaling pathway in colorectal cancer: A comprehensive review

Colorectal cancer (CRC) remains a major global health concern, necessitating an in-depth exploration of the intricate molecular mechanisms underlying its progression and potential therapeutic interventions. Transforming Growth Factor-β (TGF-β) signaling, a pivotal pathway implicated in CRC plays a dual role as a tumor suppressor in the early stages and a promoter of tumor progression in later stages. Recent research has shed light on the critical involvement of noncoding RNAs (ncRNAs) in modulating the TGF-β signaling pathway, introducing a new layer of complexity to our understanding of CRC pathogenesis. This comprehensive review synthesizes the current state of knowledge regarding the function and therapeutic potential of various classes of ncRNAs, including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), in the context of TGF-β signaling in CRC. The intricate interplay between these ncRNAs and key components of the TGF-β pathway is dissected, revealing regulatory networks that contribute to the dynamic balance between tumor suppression and promotion. Emphasis is placed on how dysregulation of specific ncRNAs can disrupt this delicate equilibrium, fostering CRC initiation, progression, and metastasis. Moreover, the review provides a critical appraisal of the emerging therapeutic strategies targeting ncRNAs associated with TGF-β signaling in CRC. The potential of these ncRNAs as diagnostic and prognostic biomarkers is discussed, highlighting their clinical relevance. Additionally, the challenges and prospects of developing RNA-based therapeutics, such as RNA interference and CRISPR/Cas-based approaches, are explored in the context of modulating TGF-β signaling for CRC treatment. In conclusion, this review offers a comprehensive overview of the intricate interplay between ncRNAs and the TGF-β signaling pathway in CRC. By unraveling the functional significance of these regulatory elements, we gain valuable insights into the molecular landscape of CRC, paving the way for the development of novel and targeted therapeutic interventions aimed at modulating the TGF-β signaling cascade through the manipulation of ncRNAs.

Fluorescence-Based Mono- and Multimodal Imaging for In Vivo Tracking of Mesenchymal Stem Cells

The advancement of stem cell therapy has offered transformative therapeutic outcomes for a wide array of diseases over the past decades. Consequently, stem cell tracking has become significant in revealing the mechanisms of action and ensuring safe and effective treatments. Fluorescence stands out as a promising choice for stem cell tracking due to its myriad advantages, including high resolution, real-time monitoring, and multi-fluorescence detection. Furthermore, combining fluorescence with other tracking modalities-such as bioluminescence imaging (BLI), positron emission tomography (PET), photoacoustic (PA), computed tomography (CT), and magnetic resonance (MR)-can address the limitations of single fluorescence detection. This review initially introduces stem cell tracking using fluorescence imaging, detailing various labeling strategies such as green fluorescence protein (GFP) tagging, fluorescence dye labeling, and nanoparticle uptake. Subsequently, we present several combinations of strategies for efficient and precise detection.

The interplay between IGF-1R signaling and Hippo-YAP in breast cancer stem cells

BACKGROUND

Both IGF-1R/PI3K/AKT/mTOR and Hippo pathways are crucial for breast cancer stem cells (BCSCs). However, their interplay remains unclear.

METHODS

Four triple negative breast cancer cell lines derived from CSC of two patient-derived xenografts (PDXs), AS-B145, AS-B145-1R, AS-B244, and AS-B244-1R, were used to elucidate the role of YAP in BCSCs. YAP silenced BCSCs were analyzed by cell proliferation, aldehyde dehydrogenase (ALDH) activity, mammosphere formation, and tumorigenesis. The effects of modulating IGF-1R and IGF-1 on YAP expression and localization were evaluated. The clinical correlation of YAP and IGF-1R signaling with the overall survival (OS) of 7830 breast cancer patients was analyzed by KM plotter.

RESULTS

Knockdown of YAP abates the viability and stemness of BCSCs in vitro and tumorigenicity in vivo. Depletion of IGF-1R by shRNA or specific inhibitor decreases YAP expression. In contrast, IGF-1 addition upregulates YAP and enhances its nuclear localization. YAP overexpression increased the mRNA level of IGF-1, but not IGF-1R. Data mining of clinical breast cancer specimens revealed that basal-like breast cancer patients with higher level of IGF-1 and YAP exhibit significantly shorter OS.

CONCLUSIONS

YAP contributes to stemness features of breast cancer in vitro and in vivo. The expression and localization of YAP was regulated by IGF-1R and YAP expression in turns upregulates IGF-1, but not IGF-1R. Clinically, higher level of YAP and IGF-1 significantly correlated with shorter OS in basal-like breast cancer. Taken together, these findings suggest the clinical relevance of interplay between YAP and IGF-1/IGF-1R pathway in sustaining the properties of BCSCs. Video Abstract.

Versatile nanodiamond-based tools for therapeutics and bioimaging

Nanodiamonds (NDs) are a remarkable class of carbon-based nanoparticles in nanomedicine which have recently become a hot topic of research due to their unique features including functionalization versatility, tunable opto-magnetic properties, chemical stability, minimal cytotoxicity, high affinity to biomolecules and biocompatibility. These attractive features make NDs versatile tools for a wide range of biologically relevant applications. In this feature article, we discuss the opto-magnetic properties of negatively charged nitrogen vacancy (NV^-) centres in NDs as fluorescence probes. We further discuss the frequently used chemical methods for surface chemistry modification of NDs which are relevant for biomedical applications. The in vitro and in vivo biocompatibility of modified NDs is also highlighted. Subsequently, we give an overview of recent state-of-the-art biomedical applications of NDs as versatile tools for bioimaging and detection, and as targeting nanocarriers for chemotherapy, photodynamic therapy, gene therapy, antimicrobial and antiviral therapy, and bone tissue engineering. Finally, we pinpoint the main challenges for NDs in biomedical applications which lie ahead and discuss perspectives on future directions in advancing the field for practical applications and clinical translations.

Applications of Fluorescent Nanodiamond in Biology

Fluorescent nanodiamond (FND) has emerged as a promising material in several multidisciplinary areas, including biology, chemistry, physics, and materials science. Composed of sp 3 ‐carbon atoms, FND offers superior biocompatibility, chemical inertness, a large surface area, tunable surface structure, and excellent mechanical characteristics. The nanoparticle is unique in that it comprises a high‐density ensemble of negatively charged nitrogen‐vacancy (NV − ) centers that act as built‐in fluorophores and exhibit a number of remarkable optical and magnetic properties. These properties make FND particularly well suited for a wide range of applications, including cell labeling, long‐term cell tracking, super‐resolution imaging, nanoscale sensing, and drug delivery. This article discusses recent applications of FND‐enabled developments in biology.

The influence of differently functionalized nanodiamonds on proliferation, apoptosis and EMT/MET phenomena in 2D and 3D tumor cell cultures

Nanodiamonds (ND) have been suggested to have several potential uses in biomedicine, since they are seemingly biocompatible. However, data about the biological effects of ND in physiological conditions are scarce. In this study, we observed that prostate cancer cells (LNCaP) and breast cancer cells (MDA-MB-231 and MCF-7) cultured with ND show morphological changes and altered gene and protein expression. In 2D we could detect only slight effects of ND on cell growth and apoptosis induction. Therefore, we applied different functionalized ND in a novel 3D cell culture model that reflects better tissue conditions compared to conventional 2D cell cultures. In 3D proliferation was reduced by all nanoparticles and benzoquinone functionalized ND induced cell death. As the used decellularized scaffold maintains the tissue architecture, we could also functionally investigate if nanoparticles induce cell migration into deeper layers and if they display markers of Mesenchymal Epithelial Transition (MET). We detected in more mesenchymal and invasive growing MDA-MB-231 cells less vimentin and increased levels of pan-cytokeratin expression after ND treatment, which indicates a MET induction. Our observations suggest that the presence of ND stimulates MET, with varying degrees of transition. The observation that ND do not support the opposite, EMT, is beneficial, since EMT is known to play a major role in tumor metastasis. However, a special focus should be placed on the characterization of biological effects to be able to guarantee the safety of ND in clinical use.

Supraclavicular lymph node recurrence after radical surgery: is epidermal growth factor receptor a predictive marker?

The aim of this study was to evaluate the rare postoperative supraclavicular metastasis originating from oral squamous cell carcinoma (OSCC) and to discuss epidermal growth factor receptor (EGFR) as a potential predictive marker. Tumour specimens of OSCC patients divided into three groups were included: supraclavicular metastasis (n = 8), conventional cervical metastasis (n = 28), no metastasis (n = 48). Basic information and EGFR expression were compared among these groups and the data were analysed to identify potentially related risk factors for supraclavicular metastasis. In the supraclavicular metastasis group (n = 8), all primary tumours were T1-T2 and located in the tongue and buccal region; five of eight cases were pathologically N0. The median interval from the primary tumour resection to the development of supraclavicular metastases was 21.5 months. All related deaths (5/8) occurred within 2 years. In the supraclavicular metastasis group, EGFR expression was highest in the supraclavicular metastases, followed by cervical lymph nodes, and was lowest in the primary tumours (P = 0.39). In contrast, in the conventional metastasis group and the N0 group, EGFR expression was higher in the primary tumours than in the lymph nodes (P < 0.01). Supraclavicular metastasis of OSCC is infrequent and associated with a poor prognosis. EGFR might predict the occurrence of supraclavicular metastasis.

Active Carbon-Based Nanomaterials in Food Packaging

Carbon-based nanomaterials (CBN) are currently used in many biomedical applications. The research includes optimization of single grain size and conglomerates of pure detonated nanodiamond (DND), modified nanodiamond particles and graphene oxide (GO) in order to compare their bactericidal activity against food pathogens. Measurement of grain size and zeta potential was performed using the Dynamic Light Scattering (DLS) method. Surface morphology was evaluated using a Scanning Electron Microscope (SEM) and confocal microscope. X-ray diffraction (XRD) was performed in order to confirm the crystallographic structure of detonation nanodiamond particles. Bacteriostatic tests were performed by evaluating the inhibition zone of pathogens in the presence of carbon based nanomaterials. Raman spectroscopy showed differences between the content of the diamond and graphite phases in diamond nanoparticles. Fluorescence microscopy and adenosine-5′-triphosphate (ATP) determination methods were used to assess the bactericidal of bioactive polymers obtained by modification of food wrapping film using various carbon-based nanomaterials. The results indicate differences in the sizes of individual grains and conglomerates of carbon nanomaterials within the same carbon allotropes depending on surface modification. The bactericidal properties depend on the allotropic form of carbon and the type of surface modification. Depending on the grain size of carbon-based materials, surface modification, the content of the diamond and graphite phases, surface of carbon-based nanomaterials film formation shows more or less intense bactericidal properties and differentiated adhesion of bacterial biofilms to food films modified with carbon nanostructures.

Advancements in Cancer Stem Cell Isolation and Characterization

Occurrence of stem cells (CSCs) in cancer is well established in last two decades. These rare cells share several properties including presence of common surface markers, stem cell markers, chemo- and radio- resistance and are highly metastatic in nature; thus, considered as valuable prognostic and therapeutic targets in cancer. However, the studies related to CSCs pave number of issues due to rare cell population and difficulties in their isolation ascribed to common stem cell marker. Various techniques including flow cytometry, laser micro-dissection, fluorescent nanodiamonds and microfluidics are used for the isolation of these rare cells. In this review, we have included the advance strategies adopted for the isolation of CSCs using above mentioned techniques. Furthermore, CSCs are primarily found in the core of the solid tumors and their microenvironment plays an important role in maintenance, self-renewal, division and tumor development. Therefore, in vivo tracking and model development become obligatory for functional studies of CSCs. Fluorescence and bioluminescence tagging has been widely used for transplantation assay and lineage tracking experiments to improve our understanding towards CSCs behaviour in their niche. Techniques such as Magnetic resonance imaging (MRI) and Positron emission tomography (PET) have proved useful for tracking of endogenous CSCs which could be helpful in their identification in clinical settings.

Nanoparticle-based Cell Trackers for Biomedical Applications

The continuous or real-time tracking of biological processes using biocompatible contrast agents over a certain period of time is vital for precise diagnosis and treatment, such as monitoring tissue regeneration after stem cell transplantation, understanding the genesis, development, invasion and metastasis of cancer and so on. The rationally designed nanoparticles, including aggregation-induced emission (AIE) dots, inorganic quantum dots (QDs), nanodiamonds, superparamagnetic iron oxide nanoparticles (SPIONs), and semiconducting polymer nanoparticles (SPNs), have been explored to meet this urgent need. In this review, the development and application of these nanoparticle-based cell trackers for a variety of imaging technologies, including fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, magnetic particle imaging, positron emission tomography and single photon emission computing tomography are discussed in detail. Moreover, the further therapeutic treatments using multi-functional trackers endowed with photodynamic and photothermal modalities are also introduced to provide a comprehensive perspective in this promising research field.

miR-4666-3p and miR-329 Synergistically Suppress the Stemness of Colorectal Cancer Cells via Targeting TGF-β/Smad Pathway

Quiescent caner stem cells are identified as a subpopulation of colon cancer cells in dormant state and possess strong stem-cell like characteristics. Previously, we have identified this subpopulation in colorectal cancer (quiescent colon cancer stem cells, QCCSCs), and find QCCSCs are sensitive to the apoptotic effect of IFN-γ, which is attributed to their high IFN-γR expression levels. Microarray and bioinformatic analysis indicate miR-4666-3p is low expressed in QCCSCs and target IFN-γR1/2, which is proved by luciferase assay and western-blot. Furthermore, we find miR-4666-3p could also target TGF-βR1 to block the activation of TGF-β1/Smad pathway, therefore function as a tumor suppressor gene to inhibit the stemness of colon cancer cells. Besides, compared with QCCSCs, we find the TGF-β1 expression also decreased with the weakening of stemness properties. In terms of mechanism, our result reveal TGF-β1 is the target gene of miR-329, which is also high expressed in non-QCCSCs. Thereafter, we perform gain- and loss- function experiments to confirm the synergistic effect between miR-4666-3p and miR-329 in blocking the activation of TGF-β/Smad pathway. Finally, we evaluate the expression of both miR-4666-3p and miR-329 in 73 tumor specimens and paired normal tissue, and find both two miRNAs are related to unfavorable prognosis and advanced tumor stage in colorectal cancer. Our study revealed a novel epigenetic regulation mechanism in colon cancer stem cells, which could be exploited as a novel therapeutic strategy for cancer treatment.

Fluorescent Nanodiamonds Enable Long-Term Detection of Human Adipose-Derived Stem/Stromal Cells in an In Vivo Chondrogenesis Model Using Decellularized Extracellular Matrices and Fibrin Glue Polymer

Clinically available materials, including allogeneic irradiated costal cartilage and fibrin glue polymer, were used as scaffolds for in vivo chondrogenic differentiation of human adipose-derived stem/stromal cells (hASCs) in the attempt to develop a more efficient treatment over current methods. Current studies include the use of growth-factor stimulation, tissue engineering, and biocompatible materials; however, most methods involve complicated processes and pose clinical limitations. In this report, the xenografts in the experimental group composed of a diced decellularized cartilage extracellular matrix (ECM), hASCs, and fibrin glue polymer were implanted into the subcutaneous layer of nude mice, and the results were compared with two groups of controls; one control group received implantation of decellularized cartilage ECM and fibrin glue polymer, and the other control group received implantation of hASCs mixed with fibrin glue polymer. To evaluate whether hASCs had in vivo chondrogenesis in the xenografts, hASCs were labeled with fluorescent nanodiamonds (FNDs), a biocompatible and photostable nanomaterial, to allow for long-term detection and histological analysis. Increased cellularity, glycosaminoglycan, and collagen deposition were found by the histological examination in the experimental group compared with control groups. With the background-free detection technique and time-gated fluorescence imaging, the numbers and locations of the FND-labeled hASCs could be detected by confocal microscopy. The chondrocyte-specific markers, such as aggrecan and type II collagen, were colocalized with cells containing signals of FNDs which indicated in vivo chondrogenesis of hASCs. Taken together, functional in vivo chondrogenesis of the hASCs could be achieved by clinically available decellularized cartilage ECM and fibrin glue polymer in the nude mice model without in vitro chondrogenic induction. The fluorescent signals of FNDs in hASCs can be detected in histological analysis, such as hematoxylin and eosin staining (H&E staining) without the interference of the autofluorescence. Our study may warrant future clinical applications of the combination of decellular cartilage ECM, fibrin glue polymer, and hASCs for cartilage repair.

Reciprocal feedback regulation of ST3GAL1 and GFRA1 signaling in breast cancer cells

GFRA1 and RET are overexpressed in estrogen receptor (ER)-positive breast cancers. Binding of GDNF to GFRA1 triggers RET signaling leading to ER phosphorylation and estrogen-independent transcriptional activation of ER-dependent genes. Both GFRA1 and RET are membrane proteins which are N-glycosylated but no O-linked sialylation site on GFRA1 or RET has been reported. We found GFRA1 to be a substrate of ST3GAL1-mediated O-linked sialylation, which is crucial to GDNF-induced signaling in ER-positive breast cancer cells. Silencing ST3GAL1 in breast cancer cells reduced GDNF-induced phosphorylation of RET, AKT and ERα, as well as GDNF-mediated cell proliferation. Moreover, GDNF induced transcription of ST3GAL1, revealing a positive feedback loop regulating ST3GAL1 and GDNF/GFRA1/RET signaling in breast cancers. Finally, we demonstrated ST3GAL1 knockdown augments anti-cancer efficacy of inhibitors of RET and/or ER. Moreover, high expression of ST3GAL1 was associated with poor clinical outcome in patients with late stage breast cancer and high expression of both ST3GAL1 and GFRA1 adversely impacted outcome in those with high grade tumors.

Fluorescent Nanodiamond Applications for Cellular Process Sensing and Cell Tracking

Diamond nanocrystals smaller than 100 nm (nanodiamonds) are now recognized to be highly biocompatible. They can be made fluorescent with perfect photostability by creating nitrogen-vacancy (NV) color centers in the diamond lattice. The resulting fluorescent nanodiamonds (FND) have been used since the late 2000s as fluorescent probes for short- or long-term analysis. FND can be used both at the subcellular scale and the single cell scale. Their limited sub-diffraction size allows them to track intracellular processes with high spatio-temporal resolution and high contrast from the surrounding environment. FND can also track the fate of therapeutic compounds or whole cells in the organs of an organism. This review presents examples of FND applications (1) for intra and intercellular molecular processes sensing, also introducing the different potential biosensing applications based on the optically detectable electron spin resonance of NV^- centers; and (2) for tracking, firstly, FND themselves to determine their biodistribution, and secondly, using FND as cell tracking probes for diagnosis or follow-up purposes in oncology and regenerative medicine.

Nanodiamonds as multi-purpose labels for microscopy

Nanodiamonds containing fluorescent nitrogen-vacancy centers are increasingly attracting interest for use as a probe in biological microscopy. This interest stems from (i) strong resistance to photobleaching allowing prolonged fluorescence observation times; (ii) the possibility to excite fluorescence using a focused electron beam (cathodoluminescence; CL) for high-resolution localization; and (iii) the potential use for nanoscale sensing. For all these schemes, the development of versatile molecular labeling using relatively small diamonds is essential. Here, we show the direct targeting of a biological molecule with nanodiamonds as small as 70 nm using a streptavidin conjugation and standard antibody labelling approach. We also show internalization of 40 nm sized nanodiamonds. The fluorescence from the nanodiamonds survives osmium-fixation and plastic embedding making them suited for correlative light and electron microscopy. We show that CL can be observed from epon-embedded nanodiamonds, while surface-exposed nanoparticles also stand out in secondary electron (SE) signal due to the exceptionally high diamond SE yield. Finally, we demonstrate the magnetic read-out using fluorescence from diamonds prior to embedding. Thus, our results firmly establish nanodiamonds containing nitrogen-vacancy centers as unique, versatile probes for combining and correlating different types of microscopy, from fluorescence imaging and magnetometry to ultrastructural investigation using electron microscopy.

Diamond nanostructures for drug delivery, bioimaging, and biosensing

This review summarizes the superior properties of diamond nanoparticles and vertically aligned diamond nanoneedles and their applications in biosensing, bioimaging and drug delivery.

Fluorescent Nanodiamond: A Versatile Tool for Long-Term Cell Tracking, Super-Resolution Imaging, and Nanoscale Temperature Sensing

Fluorescent nanodiamond (FND) has recently played a central role in fueling new discoveries in interdisciplinary fields spanning biology, chemistry, physics, and materials sciences. The nanoparticle is unique in that it contains a high density ensemble of negatively charged nitrogen-vacancy (NV(-)) centers as built-in fluorophores. The center possesses a number of outstanding optical and magnetic properties. First, NV(-) has an absorption maximum at ∼550 nm, and when exposed to green-orange light, it emits bright fluorescence at ∼700 nm with a lifetime of longer than 10 ns. These spectroscopic properties are little affected by surface modification but are distinctly different from those of cell autofluorescence and thus enable background-free imaging of FNDs in tissue sections. Such characteristics together with its excellent biocompatibility render FND ideal for long-term cell tracking applications, particularly in stem cell research. Next, as an artificial atom in the solid state, the NV(-) center is perfectly photostable, without photobleaching and blinking. Therefore, the NV-containing FND is suitable as a contrast agent for super-resolution imaging by stimulated emission depletion (STED). An improvement of the spatial resolution by 20-fold is readily achievable by using a high-power STED laser to deplete the NV(-) fluorescence. Such improvement is crucial in revealing the detailed structures of biological complexes and assemblies, including cellular organelles and subcellular compartments. Further enhancement of the resolution for live cell imaging is possible by manipulating the charge states of the NV centers. As the "brightest" member of the nanocarbon family, FND holds great promise and potential for bioimaging with unprecedented resolution and precision. Lastly, the NV(-) center in diamond is an atom-like quantum system with a total electron spin of 1. The ground states of the spins show a crystal field splitting of 2.87 GHz, separating the ms = 0 and ±1 sublevels. Interestingly, the transitions between the spin sublevels can be optically detected and manipulated by microwave radiation, a technique known as optically detected magnetic resonance (ODMR). In addition, the electron spins have an exceptionally long coherence time, making FND useful for ultrasensitive detection of temperature at the nanoscale. Pump-probe-type nanothermometry with a temporal resolution of better than 10 μs has been achieved with a three-point sampling method. Gold/diamond nanohybrids have also been developed for highly localized hyperthermia applications. This Account provides a summary of the recent advances in FND-enabled technologies with a special focus on long-term cell tracking, super-resolution imaging, and nanoscale temperature sensing. These emerging and multifaceted technologies are in synchronicity with modern imaging modalities.