Carbon dots as versatile nanomaterials in sensing and imaging: Efficiency and beyond

Enhancing organoid technology with carbon-based nanomaterial biosensors: Advancements, challenges, and future directions

Various carbon-based nanomaterials (CBNs) have been utilized to develop nano- and microscale biosensors that enable real-time and continuous monitoring of biochemical and biophysical changes in living biological systems. The integration of CBN-based biosensors into organoids has recently provided valuable insights into organoid development, disease modeling, and drug responses, enhancing their functionality and expanding their applications in diverse biomedical fields. These biosensors have been particularly transformative in studying neurological disorders, cardiovascular diseases, cancer progression, and liver toxicity, where precise, non-invasive monitoring is crucial for understanding pathophysiological mechanisms and assessing therapeutic efficacy. This review introduces intra- and extracellular biosensors incorporating CBNs such as graphene, carbon nanotubes (CNTs), graphene oxide (GO), reduced graphene oxide (rGO), carbon dots (CDs), and fullerenes. Additionally, it discusses strategies for improving the biocompatibility of CBN-based biosensors and minimizing their potential toxicity to ensure long-term organoid viability. Key challenges such as biosensor integration, data accuracy, and functional compatibility with specific organoid models are also addressed. Furthermore, this review highlights how CBN-based biosensors enhance the precision and relevance of organoid models in biomedical research, particularly in organ-specific applications such as brain-on-a-chip systems for neurodegenerative disease studies, liver-on-a-chip platforms for hepatotoxicity screening, and cardiac organoids for assessing cardiotoxicity in drug development. Finally, it explores how biosensing technologies could revolutionize personalized medicine by enabling high throughput drug screening, patient-specific disease modeling, and integrated sensing platforms for early diagnostics. By capturing current advancements and future directions, this review underscores the transformative potential of carbon-based nanotechnology in organoid research and its broader impact on medical science.

Perylene tetracarboxylic acid-folate conjugated carbon quantum dots for targeted photodynamic therapy of prostate cancer

This study reports the facile one-pot hydrothermal synthesis of water-soluble perylenetetracarboxylic dianhydride (PTCDA) conjugated carbon quantum dots (Per CDs) and their folate conjugate (PerFACDs), addressing the insolubility of PTCDA, a promising photosensitizer. Both CDs were thoroughly characterized using HRTEM, FTIR, Raman, and XPS techniques. Their singlet oxygen quantum yield (ΦΔ), zeta potential, absorption and photoluminescence spectra were also studied. Their anti-human prostate cancer activity was tested using PC-3 cells as a model. The mode of cell death was investigated using flow cytometry, and their heamolytic activity and effect on the viability of normal peripheral blood mononuclear cells and were evaluated to assess the safety. The produced CDs were uniform spheres with diameters below 8 nm. At physiological pH, PerCDs exhibited a surface charge of -9 mV, while PerFACDs had -12 mV and a ΦΔ of 0.22. The biocompatibility and cytotoxicity of the produced CDs were evaluated in vitro normal human fibroblast (HFF-1) cells, and peripheral blood cells. Both PerCDs and PerFACD showed negligible toxicity toward normal cells. To assess selective cytotoxicity, the selectivity index (SI) was calculated under dark conditions, yielding values of 1.47 for PerCDs and 2.4 for PerFACD, indicating significantly enhanced selectivity of PerFACD toward PC3 cells. Upon illumination using monochromatic 520 nm light-emitting diode (1.5 mW/cm2), a total eradication of PC-3 cells was achieved within 60 min of irradiation using Per FA CD that was significantly more potent than Per CDs. Per FA CDs-PDT induced an apoptotic cell death mode at shorter irradiation times and a necrotic one at longer durations. These findings suggest that our synthesized third generation photosensitizer Per CDs and Per FA CD hold promise as safe and effective candidates for targeted PDT of prostate cancer.

Synthesis, Characterization, Magnetic Properties, and Applications of Carbon Dots as Diamagnetic Chemical Exchange Saturation Transfer Magnetic Resonance Imaging Contrast Agents: A Review

Carbon dots (CDs) are metal-free carbon-based nanoparticles. They possess excellent photoluminescent properties, various physical properties, good chemical stability, high water solubility, high biocompatibility, and tunable surface functionalities, suitable for biomedical applications. Their properties are subject to synthetic conditions such as pH, reaction time, temperature, precursor, and solvent. Until now, a large number of articles on the synthesis and biomedical applications of CDs using their photoluminescent properties have been reported. However, their research on magnetic properties and especially, diamagnetic chemical exchange saturation transfer (diaCEST) in magnetic resonance imaging (MRI) is very poor. The diaCEST MRI contrast agents are based on exchangeable protons of materials with bulk water protons and thus, different from conventional MRI contrast agents, which are based on enhancements of proton spin relaxations of bulk water and tissue. In this review, various syntheses, characterizations, magnetic properties, and potential applications of CDs as diaCEST MRI contrast agents are reviewed. Finally, future perspectives of CDs as the next-generation diaCEST MRI contrast agents are discussed.

Exploring Green Practices: a Review of Carbon Dot-Based Sustainable Sensing Approaches

The increasing demand for sustainable and eco-friendly technologies has driven significant interest in carbon dots (CDs) due to their unique optical properties, low toxicity, and versatile applications in sensing. The aim of this review is to provide a comprehensive analysis of the current advancements in CD-based sensing approaches, with a focus on their environmental sustainability based on greenness evaluation tools. We begin by discussing the principles and methodologies of greenness evaluation, including various assessment tools and metrics used to measure the environmental impact of CD synthesis and applications. Key applications of CD-based sensors in detecting pollutants, biomolecules, and other analytes are examined, emphasizing their potential in environmental monitoring, biological, and food analysis. The review concludes with a discussion on future research directions aimed at overcoming these challenges and enhancing the sustainability of CD-based sensing technologies. Through this detailed exploration, we aim to provide valuable insights into the greenness of CDs, fostering their development as a cornerstone of sustainable sensing technologies. The evaluation tools applied for future probes confirmed their superior environmental friendliness.

Facile Synthesis of N-Doped CDs from Ridge Gourd Seeds for the Sensitive Detection of Fe3+ Ions

This study reports the synthesis of nitrogen-doped carbon dots (N-CDs) from ridge gourd seeds via a hydrothermal process. The optical and physicochemical properties of the synthesized N-CDs were characterized using various techniques, including UV-Visible, fluorescence (FL), FT-IR, X-ray diffractometer (XRD), TEM, and XPS. The resulting N-CDs had an average size of 4.72 ± 0.2 nm, high monodispersity, and a quantum yield of 11.8%, which is related to efficient light emission. These N-CDs were highly dispersible in water and exhibited excitation-independent FL at varying excitation wavelengths. They showed excellent stability under diverse conditions, such as variations in pH, high ionic strengths, and prolonged light exposure, which enhances their use in potential applications. As FL probes, the N-CDs demonstrated the selective and sensitive detection of Fe3+ ions, with a significant FL quenching response. A strong linear correlation (R2 = 0.9899) was observed for Fe3+ concentrations in the range of 0-20 µM, with a detection limit of 67.3 nM. Notably, the FL quenching could be reversed by adding EDTA, which is a chelating agent for Fe3+, indicating the potential for reversible sensing applications. The biocompatibility of the N-CDs was assessed via an MTT assay on HCT 116 cells, which revealed low cytotoxicity (94.3 ± 1.8% viability at 75 µg/mL). These findings suggest that N-CDs are safe for in biological applications and hold great promise for use in biosensing, bioimaging, and environmental monitoring.

Amino acid assisted synthesis of CDs: a novel paradigm in plant tissue culture media for enhanced cellular effects and biotechnological advancements

We report a green approach to prepare carbon dots (CDs) with fresh tomatoes as carbon sources and amino acids as dopants (ACDs) by a microwave assisted method. The synthesised CDs were analysed by UV-visible absorption spectroscopy, photoluminescence spectroscopy, high resolution transmission electron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photo electron spectroscopy. An MTT assay was used to evaluate the cytotoxicity of CDs toward L929 cells and found that CDs exhibit low cytotoxicity. The effects of ACDs on seed germination were evaluated by treating pea seeds with various concentrations of CDs. The results demonstrated a significant increase in germination and seedling vigour compared to untreated controls. Subsequently, the application of ACDs was extended to plant tissue culture. Explants treated with ACDs exhibited enhanced growth and development, indicating improved morphogenesis and proliferation rates. This study highlights the potential of ACDs as an efficient, non-toxic growth promoter in both seed germination and plant tissue culture, paving the way for their application in sustainable agriculture and plant biotechnology.

Single-Walled Carbon Nanotubes as Optical Transducers for Nanobiosensors In Vivo

Semiconducting single-walled carbon nanotubes (SWCNTs) may serve as signal transducers for nanobiosensors. Recent studies have developed innovative methods of engineering molecularly specific sensors, while others have devised methods of deploying such sensors within live animals and plants. These advances may potentiate the use of implantable, noninvasive biosensors for continuous drug, disease, and contaminant monitoring based on the optical properties of single-walled carbon nanotubes (SWCNTs). Such tools have substantial potential to improve disease diagnostics, prognosis, drug safety, therapeutic response, and patient compliance. Outside of clinical applications, such sensors also have substantial potential in environmental monitoring or as research tools in the lab. However, substantial work remains to be done to realize these goals through further advances in materials science and engineering. Here, we review the current landscape of quantitative SWCNT-based optical biosensors that have been deployed in living plants and animals. Specifically, we focused this review on methods that have been developed to deploy SWCNT-based sensors in vivo as well as analytes that have been detected by SWCNTs in vivo. Finally, we evaluated potential future directions to take advantage of the promise outlined here toward field-deployable or implantable use in patients.

Emerging Fluorescent Nanoparticles for Non-Invasive Bioimaging

Fluorescence-based techniques have great potential in the field of bioimaging and could bring tremendous progress in microbiology and biomedicine. The most essential element in these techniques is fluorescent nanomaterials. The use of fluorescent nanoparticles as contrast agents for bioimaging is a large topic to cover. The purpose of this mini-review is to give the reader an overview of biocompatible and biodegradable fluorescent nanoparticles that are emerging nanomaterials for use in fluorescent bioimaging. In addition to the biocompatibility of these nanomaterials, biodegradability is considered a necessity for short-term sustainable bioimaging. Firstly, the main requirements for bioimaging are raised, and a few existing fluorescent nanoprobes are discussed. Secondly, a few inert biocompatible fluorescent nanomaterials for long-term bioimaging that have been, to some extent, demonstrated as fluorescent probes are reviewed. Finally, a few biocompatible and biodegradable nanomaterials for short-term bioimaging that are evolving for bioimaging applications are discussed. Together, these advancements signal a transformative leap toward sustainability and functionality in biomedical imaging.

Carbon dots for pathogen detection and imaging: recent breakthroughs and future trends

As a class of carbon-based nanomaterials, carbon dots (CDs) have gained a lot of interest for a variety of applications. They offer distinctive optical, chemical, and structural characteristics along with favourable attributes such as low cost, availability of abundant functional groups, remarkable chemical inertness, high stability, exceptional biocompatibility, and ecofriendliness. This review discusses synthesis methods, structural characteristics, and surface modifications of CDs, specific for pathogen detection. Furthermore, it delves into the mechanisms that govern the interaction between pathogens and CDs. In addition, the study explores the use of CDs in a number of detection modalities, such as optical, electrochemical, and electrochemiluminescence, emphasising real-time pathogen monitoring. Moreover, both the challenges and opportunities related to the application of CDs-based detection and imaging methods are highlighted in field and clinical contexts.

Biophysical translational posterity of green carbon quantum dots: the unparalleled versatility

Carbon dots (CQDs), zero-dimensional carbon nanostructures, have attracted considerable interest among researchers due to their versatile applications. CQDs exhibit exceptional photoluminescent properties and high quantum yield, making them ideal candidates for bioimaging, drug delivery and environmental sensing. Their biocompatibility and tunable surface chemistry enable targeted therapeutic delivery and real-time imaging with minimal toxicity. Additionally, CQDs are emerging as promising materials in optoelectronics, offering sustainable alternatives in light-emitting diodes and solar cells. This review underscores the unparalleled adaptability of green CQDs in bridging the gap between laboratory research and practical applications, paving the way for innovative solutions in healthcare and environmental monitoring. Through comprehensive analysis, it advances the understanding of CQDs, positioning them at the forefront of next-generation nanomaterials with significant translational impact.