Fluorescent-Based Neurotransmitter Sensors: Present and Future Perspectives.

Neurotransmitters (NTs) are endogenous low-molecular-weight chemical compounds that transmit synaptic signals in the central nervous system. These NTs play a crucial role in facilitating signal communication, motor control, and processes related to memory and learning. Abnormalities in the levels of NTs lead to chronic mental health disorders and heart diseases. Therefore, detecting imbalances in the levels of NTs is important for diagnosing early stages of diseases associated with NTs. Sensing technologies detect NTs rapidly, specifically, and selectively, overcoming the limitations of conventional diagnostic methods. In this review, we focus on the fluorescence-based biosensors that use nanomaterials such as metal clusters, carbon dots, and quantum dots. Additionally, we review biomaterial-based, including aptamer- and enzyme-based, and genetically encoded biosensors. Furthermore, we elaborate on the fluorescence mechanisms, including fluorescence resonance energy transfer, photon-induced electron transfer, intramolecular charge transfer, and excited-state intramolecular proton transfer, in the context of their applications for the detection of NTs. We also discuss the significance of NTs in human physiological functions, address the current challenges in designing fluorescence-based biosensors for the detection of NTs, and explore their future development.

Polyphenolic Carbon Quantum Dots with Intrinsic Reactive Oxygen Species Amplification for Two-Photon Bioimaging and In Vivo Tumor Therapy.

Recent studies indicate that mitochondrial dysfunctions and DNA damage have a critical influence on cell survival, which is considered one of the therapeutic targets for cancer therapy. In this study, we demonstrated a comparative study of the effect of polyphenolic carbon quantum dots (CQDs) on in vitro and in vivo antitumor efficacy. Dual emissive (green and yellow) shape specific polyphenolic CQDs (G-CQDs and Y-CQDs) were synthesized from easily available nontoxic precursors (phloroglucinol), and the antitumor property of the as-synthesized probe was investigated as compared to round-shaped blue emissive CQDs (B-CQDs) derived from well-reported precursor citric acid and urea. The B-CQDs had a nuclei-targeting property, and G-CQDs and Y-CQDs had mitochondria-targeting properties. We have found that the polyphenol containing CQDs (at a dose of 100 µg mL-1) specifically attack mitochondria by excess accumulation, altering the metabolism, inhibiting branching pattern, imbalanced Bax/Bcl-2 homeostasis, and ultimately generating oxidative stress levels, leading to oxidative stress-induced cell death in cancer cells in vitro. We show that G-CQDs are the main cause of oxidative stress in cancer cells because of their ability to produce sufficient •OH- and 1O2 radicals, evidenced by electron paramagnetic resonance spectroscopy and a terephthalic acid test. Moreover, the near-infrared absorption properties of the CQDs were exhibited in two-photon (TP) emission, which was utilized for TP cellular imaging of cancer cells without photobleaching. The in vivo antitumor test further discloses that intratumoral injection of G-CQDs can significantly augment the treatment efficacy of subcutaneous tumors without any adverse effects on BalB/c nude mice. We believe that shape-specific polyphenolic CQD-based nanotheranostic agents have a potential role in tumor therapy, thus proving an insight on treatment of malignant cancers.

Optimal post height and diameter in preformed zirconia crown restoration on 3D-printed primary incisors.

In this in vitro study, fracture resistance was evaluated according to the post-diameter and -length in zirconia crown restorations on three-dimensional printed primary incisors undergone pulpectomy. One hundred-and-sixty primary incisor abutments were used which were artificially fabricated through 3D-printing. Each group was divided into two subgroups based on the zirconia post-diameter (1.5 mm and 2.0 mm) employed for post setting after pulpectomy. Furthermore, each group was divided into four subgroups based on the zirconia post-height (3.0, 4.0, 5.0 and 6.0 mm). Zirconia post setting was made by applying flowable resin after filling the pulp cavity with calcium hydroxide up to 3.0 mm below cemento-enamel junction (CEJ). Finally, a preformed zirconia crown of size #1 was cemented to the abutment through resin cement. A compressive load was applied to the middle palatal surface of incisors restored with zirconia crowns by using a universal testing machine at 145° angle which is the normal interincisal angle of children. The root fracture specimens were excluded and the samples fractured within crown and core parts were included in the final fracture resistance analysis. The group with 1.5-mm post-diameter and 5.0-mm post-height had the highest fracture resistance strength (130.63 ± 55.75 N) under masticatory pressure condition. Fracture resistance was statistically greater in 5.0-mm than in 4.0-mm and 3.0-mm post-height groups for 1.5-mm post-diameter subgroup. Moreover, 5.0-mm post-height subgroup had a statistically greater fracture resistance than that of 3.0-mm post-height subgroup for 2.0-mm post-diameter group. The 2.0-mm post-diameter subgroup had a statistically greater fracture resistance than that of 1.5-mm post-diameter subgroup for 3.0-mm and 4.0-mm post-heights. If zirconia post incorporation is required for deciduous incisor restoration, a post-length equal to facial CEJ level is recommended for gaining additional retention against masticatory pressure.

Synthesis and post-synthesis strategies for polychromatic carbon dots toward unique and tunable multicolor photoluminescence and associated emission mechanism.

Carbon dots (CDs) with unique and tunable multicolor photoluminescence (PL) emission has attracted tremendous attention in the past few years due to their potential multifaceted application, specially in the biomedical and optoelectronic fields. There has been extensive deliberation and efforts to engineer the synthesis or post synthesis approach to obtain multicolor-emissive CDs and tune their optical properties toward longer wavelength. This review mainly focuses on the advancement of strategies for synthesis and post-synthesis techniques of CDs toward tunable multicolor emission. Based on the above discussion to achieve desired goals, several synthesis strategies (selection of proper benzenoid precursor, acid/base treatment of biomass, optimization of reaction conditions, optimization of the reagents, solvent engineering, acid strength regulation, reaction temperature regulation, chemical doping) and various post synthesis strategies (column chromatographic separation or purification, solvatochromism, pH variation, surface functionalization, concentration variation) have been reviewed. Although numerous research articles have been published on the synthesis of multicolor CDs for multifaceted application, there is still a lack of a concise review article focusing on systematic synthesis/post synthesis strategies with PL mechanism elucidation. Thus, we focused on providing a comprehensive overview of the state-of-the-art advances on the strategies for the preparation of polychromatic CDs with tunable emission and elucidating their emission mechanism.

Non-linear relationship between body mass index and self-rated health in older Korean adults: body image and sex considerations.

OBJECTIVES: The purpose of this study was to investigate the association between body mass index (BMI) and self-rated health (SRH) in older adults aged over 65 years while examining the influence of self-perceived body image (SBI) and sex. METHODS: Raw data were obtained from the Korea Community Health Survey, which included BMI measurements of Koreans aged over 65 years (n=59,628). Non-linear relationships between BMI and SRH were analyzed separately for each sex using restricted cubic splines while controlling for SBI and other confounding variables. RESULTS: Men showed a reverse J-shaped association, while women showed a J-shaped association between BMI and poor SRH. However, including SBI in the model changed this association for men to an inverted U-shape showing a negative direction, with the highest risk of poor SRH observed in the underweight to overweight range. For women, a nearly linear positive relationship was observed. Regardless of BMI, those who perceived their weight as not "exactly the right weight" had a higher risk of poor SRH than those who perceived their weight as "exactly the right weight" in both men and women. Older men who thought they were much too fat or too thin had similar highest risks of poor SRH, whereas older women who thought they were too thin had the highest risk of poor SRH. CONCLUSIONS: The findings of this study emphasize the importance of considering sex and body image perceptions when assessing the relationship between BMI and SRH in older adults, especially in men.

Framing of Poly(arylene-ethynylene) around Carbon Nanotubes and Iodine Doping for the Electrochemical Detection of Dopamine.

Dopamine (DA), an organic biomolecule that acts as both a hormone and a neurotransmitter, is essential in regulating emotions and metabolism in living organisms. The accurate determination of DA is important because it indicates early signs of serious neurological disorders. Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) have received considerable attention in recent years as promising porous materials with an unrivaled degree of tunability for electrochemical biosensing applications. This study adopted a solvothermal strategy for the synthesis of a conjugated microporous poly(arylene ethynylene)-4 (CMP-4) network using the Sonagashira-Hagihara cross-coupling reaction. To increase the crystallinity and electrical conductivity of the material, CMP-4 was enveloped around carbon nanotubes (CNTs), followed by iodine doping. When used as an electrochemical probe, the as-synthesized material (I2-CMP-CNT-4) exhibited excellent selectivity and sensitivity to dopamine in the phosphate-buffered solution. The detection limits of the electrochemical sensor were 1 and 1.7 µM based on cyclic voltammetry (CV) and differential pulse voltammetry (DPV).

Enlarged left atrium may be associated with laterality of anterior circulation cardioembolic stroke.

BACKGROUND: Propensity for lesion lateralization in atrial fibrillation-related cardiac embolic stroke (AF-stroke) remains controversial. In this study, we compared the hemispheric differences among patients with AF-stroke and identified factors associated with lesion laterality. METHODS: We retrospectively reviewed patients with acute AF-stroke admitted from January, 2017 to March, 2022. Patients were grouped based on whether lesions were right or left hemispheric in the anterior circulation territory, based on diffusion-weighted imaging. Factors associated with right-side propensity were analyzed. RESULTS: Among 385 patients, the mean age was 74±11 years and 52.5 % were male. Right and left hemispheric lesions were observed in 189 (49.1 %) and 196 (50.9%) patients, respectively. In the multivariate analysis, enlarged left atrium (LA) (adjusted odds ratio [aOR]=1.03, 95% confidential interval [CI], 1.007-1.061; p=0.013) and single confluent lesion pattern (aOR= 1.55, 95% CI, 1.012-2.381; p=0.044) were associated with right hemispheric lesions. CONCLUSIONS: Enlarged LA and single confluent lesion pattern were strongly related to right-sided propensity in patients with AF-stroke.

Early Response to Endovascular Thrombectomy after Stroke: Early, Late, and Very Late Time Windows.

BACKGROUND AND PURPOSE: Endovascular thrombectomy (EVT) has benefits in selected patients 6-24 h after stroke onset. However, the response to EVT >24 h after stroke onset is still unclear. We compared the early response to EVT in patients with different time windows. METHODS: Patients who underwent EVT in an emergency setting were enrolled and categorized according to when EVT was performed: within 6 (early), 6-24 (late), and >24 h (very late) after stroke onset. Early neurological improvement (ENI) and deterioration (END) were defined as improvement and worsening, respectively, of National Institutes of Health Stroke Scale (NIHSS) score by ≥4 points after EVT. The three groups' clinical characteristics and response to EVT were compared. We also investigated factors associated with ENI and END. RESULTS: During study period, 274 patients underwent EVT (109 early, 104 late, and 61 very late). Patients who underwent EVT very late were younger (p = 0.007), had smaller ischemic cores, and had lower initial NIHSS scores (8 ± 5) than those who underwent EVT early (14 ± 6) and late (13 ± 7; p < 0.001). Stroke mechanisms also differed according to the time window (p < 0.001): cardioembolism was more common after early EVT, whereas large-artery atherosclerosis was more prevalent among patients who underwent EVT very late. ENI was significantly more common after early (60.6%) and late EVT (51.0%) than after very late EVT (29.5%; p = 0.001); however, rates of END did not differ (11.0%, 13.5%, and 4.9%, respectively). ENI was independently associated with male, higher NIHSS score, and early and late EVT. END was associated with failure of recanalization. CONCLUSIONS: ENI was more observed and associated with early and late EVT. Highly selected patients receiving very late EVT may not benefit from ENI but may still have a chance to prevent END. The occurrence of END was associated not with time window but with failure of recanalization.

Relationship between Alcohol Consumption and Testosterone Deficiency according to Facial Flushes among Middle-Aged and Older Korean Men.

BACKGROUND: This study examined the relationship between alcohol consumption and total testosterone deficiency based on facial flushing among Korean men. METHODS: A total of 314 men were included in this study and divided into non-drinkers (n=78) and drinkers (n=236). Drinkers were also divided into flushers (n=96) and non-flushers (n=140). Flushers and non-flushers were separated into two groups based on the amount of alcohol consumed: moderate drinkers (≤8 standard drinks per week) and heavy drinkers (>8 standard drinks per week). Total testosterone <3.5 ng/mL was defined as testosterone deficiency. RESULTS: The risk of testosterone deficiency was significantly higher in heavy drinkers who flushed than in nondrinkers (odds ratio, 4.37; 95% confidence interval, 1.20-15.88; P=0.025). However, no significant difference was observed in the risk of testosterone deficiency in non-flushers, regardless of the amount of alcohol consumed. CONCLUSION: This study suggests that the risk of testosterone deficiency increases in heavy drinkers (>8 drinks per week) who flush compared to that in non-drinkers.

Perylene-Derived Hydrophilic Carbon Dots with Polychromatic Emissions as Superior Bioimaging and NIR-Responsive Photothermal Bactericidal Agent.

Little progress has been achieved on the synthesis of hydrophilic carbon dots (CDs), derived from polycyclic aromatic hydrocarbons, as an excellent photothermal agent. In this study, a strategy was developed to synthesize highly photoluminescent greenish-yellow emissive CDs based on nitration followed by hydrothermal carbonization of the polycyclic aromatic hydrocarbon precursor, perylene. The perylene-derived CDs (PY-CDs) exhibited an excellent NIR-light (808 nm) harvesting property toward high photothermal conversion efficiency (PCE = ∼56.7%) and thus demonstrated remarkable NIR-light responsive photothermal bactericidal performance. Furthermore, these fluorescent PY-CD nanoprobes displayed excitation-dependent polychromatic emissions in the range of 538-600 nm, with the maximum emission at 538 nm. This enables intense multicolor biological imaging of cellular substances with long-term photostability, nontoxicity, and effective subcellular distribution. The bactericidal action of PY-CDs is likely due to the elevated reactive oxygen species amplification in cooperation with the hyperthermia effect. This study offers a potential substitute for multicolor imaging-guided metal-free carbon-based photothermal therapy.

Storytelling festival participation and tourists' revisit intention.

Storytelling is getting increasing attention as one of the effective strategies for revitalizing the local festivals and even regional economies. Yet, the mechanisms through how storytelling helps the success of local festivals are still relatively less known. Using the data from 322 individuals who participated in local festivals using storytelling, our results showed that local festival storytelling is positively related to tourists' revisit intention. Furthermore, the positive relationship between local festival storytelling and tourists' revisit intention was serially mediated by authenticity and positive emotion. Theoretical and practical implications are discussed.

Vinyl-functionalized polyphenolic-carbon dot-based fluorometric turn-off-on biosensor for the dual detection of mercury and cysteine and their in vivo sensing in zebrafish larvae.

The fluorometric turn-off-on biosensor was developed for the ultra-sensitive detection of mercury (Hg2+) and cysteine (Cys) utilizing the highly fluorescent carbon dots (CDs). Herein, the sophisticated low-temperature reflux-mediated reaction was adopted using precursors namely citric acid (CA) and polyphenolic kaempferol (KMP) by using dimethylformamide (DMF) as a solvent. The resulting CDs (i.e., CKCDs) were in the highly negative charged groups (-OH) presented with a bright-orange fluorescence. These CKCDs were functionalized with 4-vinylaniline (4-VA) by employing EDC/NHS coupling reaction, which switched its photoluminescence (PL) towards the strong-blue colored emission and termed as V-CKCDs. The functionalized V-CKCDs can be capable enough to detect mercury via the strong electrostatic interactions between positively charged Hg2+ cations and negatively charged anions (-OH groups). Hence, an adequate fluorescence quenching was observed in V-CKCDs with the lowest concentrations of Hg2+ around 0.5 µM. Significantly, after adding the complex of V-CKCDs-Hg2+ to the Cys, the fluorescence enhancement was observed. This might be attributed from the strong interactions between Hg2+ in the fluorescence sensing system and thiol (-SH) moieties from the Cys. The developed V-CKCDs are highly sensitive for detecting Hg2+ and Cys, which showed detection limits of 10.6 and 42. 48 nM, respectively. Also, the in vivo studies were investigated in zebrafish larvae using V-CKCDs for the detection of Hg2+ and Cys. The V-CKCDs were investigated in the real water samples and human serum to detect Hg2+ and Cys, respectively.

Polyphenol derived bioactive carbon quantum dot-incorporated multifunctional hydrogels as an oxidative stress attenuator for antiaging and in vivo wound-healing applications.

Upregulation of certain enzymes, such as collagenase, tyrosinase, and elastase, is triggered by several extrinsic environmental factors, such as temperature, UV radiation, humidity, and stress, and leads to elasticity loss and skin pigmentation. Herein, dual-emissive polyaromatic carbon quantum dots (CQDs) with abundant phenolic moieties, that is green and yellow CQDs (G-CQDs and Y-CQDs, respectively), were prepared using a three-fold symmetric molecule, 1,3,5-trihydroxybenzene. The significant inhibition efficacy of the fabricated CQDs against collagenase, elastase, and tyrosinase, which play important roles in skin aging, revealed their excellent antiaging potential. Y-CQDs with large polyphenolic-polyaromatic domains and abundant -OH groups exhibited high enzyme inhibitory efficacy against skin aging, and their collagenase, elastase, and tyrosinase inhibitory efficacies were ∼75 ± 4.2%, ∼52 ± 3.1%, and ∼35.3 ± 4.2%, respectively, at a concentration of 100 µg mL-1. The most critical factor that delays wound healing is oxidative stress, which is caused by the overproduction of free radicals around inflamed tissue. CQDs were effective in suppressing UV-induced reactive oxygen species at the cellular level and improved the cell viability. Subsequently, CQD-incorporated dual-emissive biocompatible gelatin-methacryloyl hydrogels were constructed as wound dressing materials to promote wound healing via inducing the proliferation of fibroblasts, enhancing cell migration and alleviating inflammation and to provide antiaging benefits. Our results demonstrated that the fabricated CQDs with remarkable optical features, low cytotoxicity, and excellent antioxidant and antiaging properties can be used as bio-imaging probes, antiaging agents, and wound dressing materials for oxidative stress-related diseases in the nanomedicine and cosmetics industries.

Mathematical modeling of dark fermentation of macroalgae for hydrogen and volatile fatty acids production.

A mathematical model of H2 and volatile fatty acids (VFAs) production via dark fermentation of particulate macroalgal substrates is presented. Carbohydrates, proteins, and lipids in the particulate substrate are convert to H2, CO2, and VFAs via disintegration/solubilization, hydrolysis, and acidogenesis. Hydrolysis is modeled using a combined surface-limiting model combined with a first-order reaction model to describe both microbial hydrolysis and physical solubilization. Experimental and published data obtained using Saccharina japonica as the substrate are used to calibrate and validate the model. The model prediction featured a good accuracy, with high R2 of 0.912 - 0.976 for all end products. The physical solubilisation accounts for 28.4% of the total hydrolysis. By the model simulation, a H2 production of 103.2 mL/g-VS and VFA production of 0.41 g/g-VS are found at optimum conditions of 20 g-TS/L (13.2 g-VS/L) of substrate concentration and 7.0 of initial pH.

Two-photon excitable membrane targeting polyphenolic carbon dots for long-term imaging and pH-responsive chemotherapeutic drug delivery for synergistic tumor therapy.

Long-term dynamic tracking of cells with theranostic properties remains challenging due to the difficulty in preparing and delivering drugs by probes. Herein, we developed highly fluorescent one- and two-photon (OP and TP) excitable polyphenolic carbon quantum dots (CQDs) for excellent membrane-targeting and drug delivery properties for synergistic tumor therapy. The green-emissive CQDs (g-CQDs) were synthesized from a three-fold symmetric polyphenolic molecule, phloroglucinol (C3h; symmetry elements: E, C3, C32, σh, S3, and S3-1), in a sulfuric acid medium. Doxorubicin (Dox) was loaded onto the g-CQDs via electrostatic interaction, resulting in a loading efficiency and content of 54.62% and 323.25 µg mL-1, respectively. The g-CQDs@Dox complex exhibited a higher rate of cell killing efficiency at both pH 5.0 and 6.5, with higher reactive oxygen species (ROS) generation due to the greater Dox accumulation in the tumor cells. In addition, TP cell imaging displayed excellent membrane-targeting properties with less photobleaching ability in tumor cells. The in vivo studies confirmed that the g-CQDs@Dox complex has higher affinity towards tumor cells, better inhibitory effects, and an absence of systemic toxicity. Therefore, our developed nanocarrier exhibited better cell imaging, drug delivery, and tumor-targeting properties, and could be used as a "smart" probe for synergistic tumor therapy.

Preparation of uniform gold nanoparticles of different quantity deposited on zinc oxide nanorods for photoelectrochemical water splitting.

For the photocatalytic test, gold nanoparticles (AuNPs) were prepared using trisodium citrate dehydrate (TCD), following which they were combined on the surface of zinc oxide (ZnO) to prepare ZnO decorated with uniform AuNPs (ZnO/AuNP) photocatalysts. The photocatalytic performance with the ZnO/AuNP was estimated through the rhodamine B (RB) dye degradation under solar irradiation. ZnO/AuNP-30 showed the greatest photocatalytic performance, achieving dye degradation efficiency up to 78.65%. Photoelectrochemical (PEC) measurements were performed using the ZnO/AuNP photoanodes. With AuNP doping amounts of 10, 20, and 30 mL on the ZnO surface, photocurrent densities of 47.46, 63.74, and 68.64 mA cm-2, respectively, were achieved at an applied voltage of 1.5 V. These values indicated that the doping of AuNPs on the ZnO surface is advantageous for enhancing its PEC water-splitting activity. The highest solar-to-hydrogen (STH) efficiency is 22% with the ZnO/AuNP-30 photoanode at an applied voltage of 0.88 V. The interfacial charge-transfer resistances at the interface were 40 and 2.2 kΩ cm2 for the ZnO and ZnO/AuNP-30 photoanodes, respectively.

Customers' Experiences of Compassion and Brand Attitude: Evidence From Low-Cost Carriers.

The purpose of this study is to examine the effect of compassion experienced by low-cost carriers customers on their brand attitudes. Specifically, this study aims to unbox the mechanisms through how the customers' experiences of compassion influence the formation of positive brand attitudes. Using the data from 423 low-cost carriers customers in South Korea, this study found that the more low-cost carriers' customers experience compassion, the more positive their brand attitudes are toward the low-cost carriers. Notably, this study demonstrated that the positive relationship between compassion and brand attitudes is serially mediated by positive emotion and positive brand image. The results from this study contribute to the literature on the airline industry by examining the roles of compassion, which is relatively new to the field, and also provide practical insights for a low-cost carrier to come up with competitive strategies to achieve a competitive advantage over its competitors in the industry.

Validation of the Simplified Palliative Prognostic Index to Predict Survival for Advanced Cancer Patients in Home Hospice Setting.

BACKGROUND: The simplified Palliative Prognostic Index (sPPI) substitutes a single item from the Communication Capacity Scale (CCS) for the delirium item of the original PPI. This study aimed to examine the validity of the sPPI for patients with advanced cancer in a home-based hospice care setting. METHODS: This study included 75 patients with advanced cancer who received home-based hospice care. We used medical records maintained by professional hospice nurses who had visited the patients in their homes. Based on their sPPI score, patients were divided into three groups-A (<4), B (≥4 and <6), and C (≥6)-to compare survival. Further, we investigated the sPPI's accuracy using the area under the receiver operating characteristic curve (AUC) and sensitivity and specificity for 3- and 6-week survival. We used three sPPIs including different substitutions for the delirium item (two methods using the CCS and one using the Korean Nursing Delirium Screening Scale). RESULTS: The median survival was 60-61 days for group A, 27-30 days for group B, and 12-16 days for group C. The difference in survival was significant (P<0.05). The AUC was 0.814-0.867 for 3-week survival and 0.736-0.779 for 6-week survival. For 3- and 6-week survival, prognostic prediction showed sensitivities of 76.2%-90.9% and 76.3%-86.8%, and specificities of 64.2%-88.7% and 51.4%-70.3%, respectively. CONCLUSION: The sPPI, which is measured by professional hospice nurses, has acceptable validity to predict survival for patients with advanced cancer in a home hospice setting in South Korea.

Fiber-optic biosensor based on the laccase immobilization on silica-functionalized fluorescent carbon dots for the detection of dopamine and multi-color imaging applications in neuroblastoma cells.

An efficient and cost-effective biosensor is of the great demand for the detection of the biologically significant neurotransmitter dopamine. In this context, enzymatic biosensors show excellent sensitivity and selectivity. In this study, we developed a laccase immobilized fiber-optic biosensor based on the fluorescence principle for the detection of dopamine. To design this biosensor, we used microwave irradiation to synthesize carbon dots (CDs) using curcumin and dimethylformamide, and the resulting CDs were called CDD-CDs. These were functionalized with a silicon precursor, 3-(aminopropyl)-triethoxysilane, and were referred to as APT-CDs. Furthermore, laccase was covalently immobilized to the APT-CDs to construct a novel bioprobe. The CDD-CDs, APT-CDs, and bioprobe showed orange (λem = 586 nm) green (λem = 533 nm), and blue-colored emissions (λem = 476 nm) at 430, 380, and 360 nm excitation wavelengths, respectively. The CDD-CDs and bioprobe showed quantum yields of 14.8% and 10.2%, respectively. The CDD-CDs displayed solvatochromism in various solvents. Bioprobe showed a significant fluorescence quenching for dopamine in the linear range of 0-30 µM with a detection limit of 41.2 nM. Bioprobe was immobilized on the tapered optical fiber using ethyl cellulose by a simple dip-coating method and investigated for multi-color imaging applications. The resulting tapered optical fiber achieved a satisfactory detection limit of 46.4 nM in the dopamine concentration range of 0-10 µM. The bioprobe demonstrated high biocompatibility, long-lasting photostability, and thermal stability, and had sufficient cytotoxicity in human neuroblastoma cells (SH-SY5Y) with excellent multi-color imaging potential. The practicality of the bioprobe was investigated in human serum and cerebrospinal fluid.

Lanthanum mediated rutin yellow-fluorescent carbon dots as multifaceted sensing probes for the detection of calcium ions in melanoma and plant cells.

Calcium (Ca2 +) as a signaling ion and intracellular second messenger plays a crucial role in living organisms for various cellular functions. In the present work, we have designed a novel yellow-fluorescent carbon dots (LERCDs) using lanthanum, ethylenediaminetetraacetic acid (EDTA), and rutin as precursors for the sensing of Ca2 + ions. In this sense, a combination of hydrothermal and reflux methods was adopted. The as-designed LERCDs display bright yellow color emission in the aqueous solutions with a high quantum yield (23.8%). The LERCDs showed excitation-independent emission property along with magnificent photostability and time stability. The LERCDs show potential fluorescence quenching response towards the Ca2+ ions in the concentration range of 0-25 µM with a detection limit of 2.19 µM. The LERCDs have studied for extracellular sensing of Ca2 + ions in both melanoma cell lines (A375) and onion epidermal cells by employing fluorescence microscopy. The LERCDs facilitate low cytotoxicity and superior biocompatibility features in A375 cells. The practicality of LERCDs was studied in biological samples like the human serum.