Small Warriors of Nature: Novel Red Emissive Chlorophyllin Carbon Dots Harnessing Fenton-Fueled Ferroptosis for In Vitro and In Vivo Cancer Treatment.

The appeal of carbon dots (CDs) has grown recently, due to their established biocompatibility, adjustable photoluminescence properties, and excellent water solubility. For the first time in the literature, copper chlorophyllin-based carbon dots (Chl-D CDs) are successfully synthesized. Chl-D CDs exhibit unique spectroscopic traits and are found to induce a Fenton-like reaction, augmenting photodynamic therapy (PDT) efficacies via ferroptotic and apoptotic pathways. To bolster the therapeutic impact of Chl-D CDs, a widely used cancer drug, temozolomide, is linked to their surface, yielding a synergistic effect with PDT and chemotherapy. Chl-D CDs' biocompatibility in immune cells and in vivo models showed great clinical potential.Proteomic analysis was conducted to understand Chl-D CDs' underlying cancer treatment mechanism. The study underscores the role of reactive oxygen species formation and pointed toward various oxidative stress modulators like aldolase A (ALDOA), aldolase C (ALDOC), aldehyde dehydrogenase 1B1 (ALDH1B1), transaldolase 1 (TALDO1), and transketolase (TKT), offering a deeper understanding of the Chl-D CDs' anticancer activity. Notably, the Chl-D CDs' capacity to trigger a Fenton-like reaction leads to enhanced PDT efficiencies through ferroptotic and apoptotic pathways. Hence, it is firmly believed that the inherent attributes of Chl-CDs can lead to a secure and efficient combined cancer therapy.

Carbon Dots in Treatment of Pediatric Brain Tumors: Past, Present, and Future Directions.

Pediatric brain tumors remain a significant source of morbidity and mortality. Though developments have been made in treating these malignancies, the blood-brain barrier, intra- and inter-tumoral heterogeneity, and therapeutic toxicity pose challenges to improving outcomes. Varying types of nanoparticles, including metallic, organic, and micellar molecules of varying structures and compositions, have been investigated as a potential therapy to circumvent some of these inherent challenges. Carbon dots (CDs) have recently gained popularity as a novel nanoparticle with theranostic properties. This carbon-based modality is highly modifiable, allowing for conjugation to drugs, as well as tumor-specific ligands in an effort to more effectively target cancerous cells and reduce peripheral toxicity. CDs are being studied pre-clinically. The ClinicalTrials.gov site was queried using the search terms: brain tumor and nanoparticle, liposome, micelle, dendrimer, quantum dot, or carbon dot. At the time of this review, 36 studies were found, 6 of which included pediatric patients. Two of the six studies investigated nanoparticle drug formulations, whereas the other four studies were on varying liposomal nanoparticle formulations for the treatment of pediatric brain tumors. Here, we reviewed the context of CDs within the broader realm of nanoparticles, their development, promising pre-clinical potential, and proposed future translational utility.

Investigation into Red Emission and Its Applications: Solvatochromic N-Doped Red Emissive Carbon Dots with Solvent Polarity Sensing and Solid-State Fluorescent Nanocomposite Thin Films.

In this work, a NIR emitting dye, p-toluenesulfonate (IR-813) was explored as a model precursor to develop red emissive carbon dots (813-CD) with solvatochromic behavior with a red-shift observed with increasing solvent polarity. The 813-CDs produced had emission peaks at 610 and 698 nm, respectively, in water with blue shifts of emission as solvent polarity decreased. Subsequently, 813-CD was synthesized with increasing nitrogen content with polyethyleneimine (PEI) to elucidate the change in band gap energy. With increased nitrogen content, the CDs produced emissions as far as 776 nm. Additionally, a CD nanocomposite polyvinylpyrrolidone (PVP) film was synthesized to assess the phenomenon of solid-state fluorescence. Furthermore, the CDs were found to have electrochemical properties to be used as an additive doping agent for PVP film coatings.

Development of Red-Emissive Carbon Dots for Bioimaging through a Building Block Approach: Fundamental and Applied Studies.

In recent years, many researchers have struggled to obtain carbon dots (CDs) that possess strong photoluminescence in the red region of light. Success in this area has been limited, although the past few years have brought several promising reports on this topic. The most successful efforts in this area still seem to struggle from a lack of dispersibility/reduced emission in water. This work endeavors to understand the formation process of CDs that do not possess strong performance in an aqueous environment and to improve their capabilities in bioimaging. o-Phenylenediamine (o-PDA) is used along with various precursors in several different solvents (varying acidic and oxidative strengths) to understand the formation process behind the structure leading to red emission that is sensitive to water. These results showed that the combination of acid properties and oxidation is essential for this process, and the important reactions are oligomerization of o-PDA and the crosslinking of these oligomers to form aromatic structural segments of CDs. These CDs are shown to be capable of quantitatively detecting water in organic solvents. Additionally, we have shown that conjugation with transferrin remarkably enhances the biocompatibility of these CDs. Transferrin-conjugated CDs with better biocompatibility were applied to bioimaging studies of neuroblastoma cell lines with N-myc and non-N-myc gene amplification, for the first time. Furthermore, CDs showed versatile bioimaging capability toward a highly aggressive neuroblastoma subgroup of tumors. The importance of creating red-emissive CDs has been well established, and this work is an important step toward understanding their formation and realizing their use in biological systems.

Structure-Activity Relationship of Carbon Nitride Dots in Inhibiting Tau Aggregation.

Due to the numerous failed clinical trials of anti-amyloid drugs, microtubule associated protein tau (MAPT) now stands out as one of the most promising targets for AD therapy. In this study, we report for the first time the structure-dependent MAPT aggregation inhibition of carbon nitride dots (CNDs). CNDs have exhibited great promise as a potential treatment of Alzheimer's disease (AD) by inhibiting the aggregation of MAPT. In order to elucidate its structure-activity relationship, CNDs were separated via column chromatography and five fractions with different structures were obtained that were characterized by multiple spectroscopy methods. The increase of surface hydrophilic functional groups is consistent with the increase of polarity from fraction 1 to 5. Particle sizes (1-2 nm) and zeta potentials (~-20 mV) are similar among five fractions. With the increase of polarity from fraction 1 to 5, their MAPT aggregation inhibition capacity was weakened. This suggests hydrophobic interactions between CNDs and MAPT, validated via molecular dynamics simulations. With a zebrafish blood-brain barrier (BBB) model, CNDs were observed to cross the BBB through passive diffusion. CNDs were also found to inhibit the generation of multiple reactive oxygen species, which is an important contributor to AD pathogenesis.

Synthesis Mechanisms, Structural Models, and Photothermal Therapy Applications of Top-Down Carbon Dots from Carbon Powder, Graphite, Graphene, and Carbon Nanotubes.

In this study, top-down syntheses of carbon dots (CDs) from four different carbon precursors, namely, carbon nano powders, graphite, graphene, and carbon nanotubes, were carried out. Systematic study demonstrated that the optical properties and surface functionalities of the CDs were quite similar and mainly influenced by the synthesis method, while the sizes, morphologies, chemical compositions, and core structures of the CDs were heavily influenced by the carbon precursors. On the basis of these studies, the formation processes and structural models of these four top-down CDs were proposed. The cell cytotoxicity and photothermal conversion efficiency of these CDs were also carefully evaluated, demonstrating their potential applications in photothermal therapy.

Drug Loading of Anthracycline Antibiotics on Carbon Dots Using Circular Dichroism Spectrometry.

Drug delivery systems using nanoparticles are currently in the panorama of nanomedicine studies. In oncology, chemotherapeutic regimens using anthracycline antibiotics rely on the dosage of treatments to minimize the severity of side effects on the patient. Therefore, even in targeted delivery systems it is of great importance to quantify the level of drug administrated for dosage and quality control of the treatment. Herein, as a feasible pathway to shed light on improving nano drug quantification procedures, we proposed a simple analytical protocol to quantify the anthracyclines loaded on our nonchiral carbon nitride dots (CNDs) with circular dichroism spectrometry (CD). The calibration curves from the linear relation between ellipticity and concentration of the anthracycline drugs followed by measurements on the CNDs conjugates were used in achieving the quantification technique which showed different drug loading for each anthracycline used such as daunorubicin, doxorubicin, and epirubicin.

Surface Chemistry Studies on the Formation of Mixed Stearic Acid/Phenylalanine Dehydrogenase Langmuir and Langmuir-Blodgett Films.

This work investigates the physicochemical properties of mixed stearic acid (HSt)/phenylalanine dehydrogenase enzyme (PheDH) Langmuir films and their immobilization onto solid supports as Langmuir-Blodgett (LB) films. PheDH from the aqueous subphase enters the surfactant matrix up to an exclusion surface pressure of 25.3 mN/m, leading to the formation of stable and highly condensed mixed Langmuir monolayers. Hydrophobic interactions between the enzyme and HSt nonpolar groups tuned the secondary structure of PheDH, evidenced by the presence of ß-sheet structures as demonstrated by infrared and circular dichroism spectra. The floating monolayers were successfully transferred to solid quartz supports, yielding Y-type LB films, and then characterized employing fluorescence, circular dichroism, and microscopic techniques, which indicated that PheDH was co-immobilized with HSt proportionally to the number of transferred layers. The enzyme fluidized the HSt monolayers, reducing their maximum dipoles when condensed to their maximum, and disorganized the alkyl chains of the fatty acid, as detected with infrared spectroscopy. The stability of the mixed floating monolayers enabled their transfer to solid supports as LB films, which is important for producing optical and electrochemical sensors for phenylalanine whose molecular architecture can be controlled with precision.

Carbon Nitride Dots: A Selective Bioimaging Nanomaterial.

In contrast to the recent immense attention in carbon nitride quantum dots (CNQDs) as a heteroatom-doped carbon quantum dot (CQD), their biomedical applications have not been thoroughly investigated. Targeted cancer therapy is a prominently researched area in the biomedical field. Here, the ability of CNQDs as a selective bioimaging nanomaterial was investigated to assist targeted cancer therapy. CNQDs were first synthesized using four different precursor sets involving urea derivatives, and the characteristics were compared to select the best candidate material for bioapplications. Characterization techniques such as UV-vis, luminescence, X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, and transmission electron microscopy were used. These CNQDs were analyzed in in vitro studies of bioimaging and labeling using pediatric glioma cells (SJGBM2) for possible selective biolabeling and nanodistribution inside the cell membrane. The in vitro cellular studies were conducted under long-wavelength emission without the interference of blue autofluorescence. Thus, excitation-dependent emission of CNQDs was proved to be advantageous. Importantly, CNQDs selectively entered SJGBM2 tumor cells, while it did not disperse into normal human embryonic kidney cells (HEK293). The distribution studies in the cell cytoplasm indicated that CNQDs dispersed into lysosomes within approximately 6 h after the incubation. The CNQDs exhibited great potential as a possible nanomaterial in selective bioimaging and drug delivery for targeted cancer therapy.

Carbon Dots: Diverse Preparation, Application, and Perspective in Surface Chemistry.

Carbon dots (CDs) are a novel class of nanoparticles with excellent properties. The development of CDs involves versatile synthesis, characterization, and various applications. However, the importance of surface chemistry of CDs, especially in applications, is often underestimated. In fact, the study of the surface chemistry of CDs is of great significance in the explanation of the unique properties of CDs as well as the pursuit of potential applications. In this feature article, we do not only introduce the development of CDs in our group but also highlight their applications where surface chemistry plays a critical role.

Interfacial Behavior of Fumonisin B1 Toxin and Its Degradation on the Membrane.

Fumonisin B1 (FB1), the most abundant component of the fumonisin family, is highly responsible for fungal infections. In this paper, our main aim is to study the surface chemistry and spectroscopic properties of the FB1 molecule and observe the impact of green LED light on the FB1 Langmuir monolayer. From the surface chemistry and spectroscopic studies, we found that the FB1 molecule forms a self-assembled Langmuir monolayer which is sufficient to mimic its interaction with the corneal tissues. The irradiation of green LED light on the FB1 Langmuir monolayer showed the degradation of the FB1 when compared to that in the absence of light. This observation reveals that FB1 molecules lose their tendency to stay as a Langmuir monolayer. The degradation observed on the interface was compared with the bulk phase of FB1. The bulk phase observation also indicated the degradation tendency which reinforced the observed interfacial property of FB1.

Close-Packed Langmuir Monolayers of Saccharide-Based Carbon Dots at the Air-Subphase Interface.

Carbon dots (CDs) are zero-dimensional carbon-based spherical nanoparticles with diameters less than 10 nm. Here, we report for the first time CDs forming stable Langmuir monolayers at the air-subphase interface. Langmuir monolayers are of great interest both fundamentally to study the interactions at the interfaces and for many applications such as the development of sensors. However, CDs usually do not form Langmuir monolayers because of their highly hydrophilic nature. In this study, amphiphilic CDs were prepared through hydrothermal carbonization using saccharides as the precursors. The surface chemistry behavior and optical properties of CDs at the air-subphase interface were studied. CDs derived from saccharides consistently formed stable Langmuir monolayers which show all essential phases, namely, gas, liquid-expanded, liquid-condensed, and solid phases. The compression-decompression cycle method showed minimum hysteresis (4.3%), confirming the retaining capacity of the CDs as a monolayer. Limiting CD areas from surface pressure-area isotherm at the air-subphase interface were used to calculate the average diameter of the CDs at the air-subphase interface. UV/vis absorption spectra of CDs dispersed in water and in Langmuir monolayers had the same bands in the UV region. The intensity of the UV/vis absorption increases with increasing surface pressure at the air-subphase interface. Interestingly, photoluminescence (PL) of the Langmuir monolayer of CDs was excitation-independent, whereas the same CDs had excitation-dependent PL when dispersed in water.

Conjugation of Carbon Dots with ß-Galactosidase Enzyme: Surface Chemistry and Use in Biosensing.

Nanoparticles have been conjugated to biological systems for numerous applications such as self-assembly, sensing, imaging, and therapy. Development of more reliable and robust biosensors that exhibit high response rate, increased detection limit, and enhanced useful lifetime is in high demand. We have developed a sensing platform by the conjugation of ß-galactosidase, a crucial enzyme, with lab-synthesized gel-like carbon dots (CDs) which have high luminescence, photostability, and easy surface functionalization. We found that the conjugated enzyme exhibited higher stability towards temperature and pH changes in comparison to the native enzyme. This enriched property of the enzyme was distinctly used to develop a stable, reliable, robust biosensor. The detection limit of the biosensor was found to be 2.9 × 10-4 M, whereas its sensitivity was 0.81 µA·mmol-1·cm-2. Further, we used the Langmuir monolayer technique to understand the surface properties of the conjugated enzyme. It was found that the conjugate was highly stable at the air/subphase interface which additionally reinforces the suitability of the use of the conjugated enzyme for the biosensing applications.

Ultrasensitive Plasmonic Biosensors for Real-Time Parallel Detection of Alpha-L-Fucosidase and Cardiac-Troponin-I in Whole Human Blood.

Cancers and many other diseases, such as hepatocellular carcinoma (HCC) and cardiovascular diseases (CVD), have threatened human lives for centuries. Therefore, a novel technique for such disease prediction is in an urgent demand for timely treatment. Biomarkers, alpha-L-fucosidase (AFU) for HCC and cardiac troponin I (cTnI) for CVD, have proven to be essential in the role of disease detection. Herein, we report on an ultrasensitive plasmonic biosensor that converts plasmonic absorption to electrical current in order to detect AFU and cTnI using whole human blood in a real-time and parallel fashion. The detection limit was calculated to be 0.016 U/L for AFU and 0.015 ng/mL for cTnI, respectively. Combined with the versatility of the strategies for different biomarkers, these results demonstrate that the developed biosensor exhibits a promising application for the prediction of cancers and many other diseases.

Quantification of Nucleic Acid Concentration in the Nanoparticle or Polymer Conjugates Using Circular Dichroism Spectroscopy.

The interface of nucleic acids and nanomaterials is among the most promising fields in recent years. Considerable efforts have been devoted to the development of novel systems based on the two components for various promising applications such as sensing, bioimaging, drug delivery, and theranostics. However, the determination of nucleic acid concentration in these systems remains as a challenge due to the interference of nanoparticles. To this end, we developed a simple, yet reliable, method to quantify the nucleic acid concentration in their nanoparticle or polymer conjugates based on circular dichroism (CD) spectroscopy. In this paper, three nucleic acids, namely, DNA sodium salt from calf thymus (NaDNA), DNA from herring sperm (hsDNA), and ribonucleic acid from torula yeast (tyRNA), were noncovalently conjugated to three nanoparticles. The concentrations of the three nucleic acids in their nanoparticle conjugates were successfully determined on the basis of CD spectra calibration curves.

Photoluminescent Carbon Dots: A Mixture of Heterogeneous Fractions.

Photoluminescent carbon dots (CDs) fractions have been isolated from a gel-like material (GM), which was synthesized using a convenient one-step solvothermal route. In terms of purification, size exclusion chromatography (SEC) and dialysis were compared with acetone wash, which revealed the advantage of acetone wash. The pre-purified GM with acetone wash (A-GM) was further isolated by the reversed-phase preparative thin layer chromatography (TLC) with acetonitrile-water mixture (7 : 3; va /vw ) as the developing solvent. As a result, there were four photoluminescent bands on the TLC plate, which indicated the presence of four photoluminescent fractions. Detailed characterization measurements such as UV/Vis absorption, fluorescence emission, attenuated total reflection Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential, dynamic light scattering, atomic force microscopy, and TEM measurements were performed on all fractions to analyze their heterogeneous optical, structural, electrical, and morphological properties. Considering the comprehensive analysis, all isolated fractions were CDs. In addition, excitation wavelength-independent CDs were obtained with a mean size of 2.5 nm and high quantum yield (55 %). Furthermore, the study demonstrates that the excitation wavelength-dependent photoluminescence of GM could result from the mixture of different surface states of each CD fraction rather than multiple surface states of uniform CDs nanoparticles.

Surface Chemistry and Spectroscopic Study of a Cholera Toxin B Langmuir Monolayer.

In this article, we explored the surface chemistry properties of a cholera toxin B (CTB) monolayer at the air-subphase interface and investigated the change in interfacial properties through in situ spectroscopy. The study showed that the impact of the blue shift was negligible, suggesting that the CTB molecules were minimally affected by the subphase molecules. The stability of the CTB monolayer was studied by maintaining the constant surface pressure for a long time and also by using the compression-decompression cycle experiments. The high stability of the Langmuir monolayer of CTB clearly showed that the driving force of CTB going to the amphiphilic membrane was its amphiphilic nature. In addition, no major change was detected in the various in situ spectroscopy results (such as UV-vis, fluorescence, and IR ER) of the CTB Langmuir monolayer with the increase in surface pressure. This indicates that no aggregation occurs in the Langmuir monolayer of CTB.

Cancer Targeting and Drug Delivery Using Carbon-Based Quantum Dots and Nanotubes.

Currently cancer treatment is in large part non-specific with respect to treatment. Medication is often harsh on patients, whereby they suffer several undesired side effects as a result. Carbon-based nanoparticles have attracted attention in recent years due to their ability to act as a platform for the attachment of several drugs and/or ligands. Relatively simple models are often used in cancer research, wherein carbon nanoparticles are conjugated to a ligand that is specific to an overexpressed receptor for imaging and drug delivery in cancer treatment. These carbon nanoparticles confer unique properties to the imaging or delivery vehicle due to their nontoxic nature and their high fluorescence qualities. Chief among the ongoing research within carbon-based nanoparticles emerge carbon dots (C-dots) and carbon nanotubes (CNTs). In this review, the aforementioned carbon nanoparticles will be discussed in their use within doxorubicin and gemcitabine based drug delivery vehicles, as well as the ligand-mediated receptor specific targeted therapy. Further directions of research in current field are also discussed.

Alpha-l-Fucosidase Immunoassay for Early Detection of Hepatocellular Carcinoma.

Detection of alpha-l-fucosidase has been shown to have relevance in diagnosing hepatocellular carcinoma. Few assays have been developed to measure this enzyme, with most relying on colorimetric techniques involving the enzyme's kinetics. While these assays are facile and quick, the sensitivity is not always sufficient for early tumor detection. To improve upon previous assays for alpha-l-fucosidase, a fluorescence based immunoassay was produced implementing an alpha-l-fucosidase specific antibody (FUCA2). The immobilization of the alpha-l-fucosidase-specific antibody onto a quartz slide was investigated with several bioconjugation approaches and an immunoassay for detection of alpha-l-fucosidase was produced. The immunoassay was utilized to produce calibration curves for quantifying alpha-l-fucosidase concentrations in both PBS and human blood serum. A detection limit of 10 nM was found using human blood serum, which is well below the diagnostic cutoff point of 80 nM.

Biosensors based on ß-galactosidase enzyme: Recent advances and perspectives.

Many industries are striving for the development of more reliable and robust ß-galactosidase biosensors that exhibit high response rate, increased detection limit and enriched useful lifetime. In a newfangled technological atmosphere, a trivial advantage or disadvantage of the developed biosensor may escort to the survival and extinction of the industry. Several alternative strategies to immobilize ß-galactosidase enzyme for their utilization in biosensors have been developed in recent years in the quest of maximum utility by controlling the defects seen in the previous biosensors. The overwhelming call for on-line measurement of different sample constituents has directed science and industry to search for best practical solutions and biosensors are witnessed as the best prospect. The main objective of this paper is to serve as a narrow footbridge by comparing the literary works on the ß-galactosidase biosensors, critically analyze their use in the construction of best biosensor by showing the pros and cons of the predicted methods for the practical use of biosensors.