A dual-ratio fluorescent probe with a single excitation triple-signal to synchronously detect PTK7 and miRNA-21 for breast cancer early diagnosis.

The measurement of tumor biomarker levels is of great significance for early diagnosis of breast cancer. The combination diagnosis of multiple tumor biomarkers will significantly improve the accuracy of early diagnosis. Here, we successfully developed a dual-ratio fluorescent sensing platform for the detection of breast cancer biomarkers (PTK7, miRNA-21) using single excitation triple-signal detection. Introducing three types of fluorescence nanomaterials with narrow emission peaks and long Stokes shift as signal markers, the three peaks (430 nm, 530 nm and 640 nm) of which do not interfere with each other in fluorescence spectra under a single excitation (360 nm). The sensing platform linked aptamer (apt) modified green fluorescence quantum dots (gQDs-apt1) and aptamer modified red fluorescence quantum dots (rQDs-apt2) to Fe3O4-cDNA1 and Fe3O4-cDNA2, respectively, via base complementary pairing with aptamer molecules. When PTK7/miRNA-21 is present in the system, gQDs-apt1/rQDs-apt2 bound to the Fe3O4 MNPs surface will be released to recover fluorescence. Upon DNase I digestion of free apt1 and apt2, the target molecules will be released to bind to gQDs-apt1/rQDs-apt2 for signal amplification. After magnetic separation, PTK7 and miRNA-21 can be quantified using the fluorescence intensity ratio of gQDs with bCDs and rQDs with bCDs at a single excitation of 360 nm wavelength. This method has high sensitivity, good selectivity, and can quantify both PTK7 and miRNA-21 simultaneously with an LOD of 0.426 ng mL-1 and 0.072 nM, respectively. Additionally, the sensing platform was used for serum detection of health man and breast cancer patients with satisfactory results.

Tumor-Associated Macrophages Regulating a Polymer Nanoplatform for Synergistic Treatment of Breast Tumors.

Tumor-associated macrophages (TAMs) play a critical role in tumor progression and metastasis. Modulation of TAM polarization is one of the most effective strategies to change the immunosuppressive tumor microenvironment (TME). In this study, organic polymer nanoparticles (CPHT) were prepared using hyaluronic acid (HA)-conjugated disulfide-bonded polyethylene imide (PEIS) as a carrier through a self-assembly strategy. These nanoparticles were modified by transferrin (Tf) and loaded with chlorin e6 (Ce6). The results showed that CPHT had good dispersion with a particle size of about 30 nm. CPHT gradually disintegrated under the exposure with a high concentration of glutathione (GSH) in tumor cells, proving the possibility for the controlled release of Ce6 and photodynamic therapy. An in vitro test showed that the uptake of CPHT in tumor cells was mediated by both HA and Tf, indicating the active tumor-targeting capacity of CPHT. CPHT significantly downregulated the ratio of CD206/CD86 and triggered the upregulation of immune factors such as TNF-α and iNOS, suggesting the repolarization of TAMs. We also found that CPHT effectively induced ferroptosis in tumor cells through lipid peroxide accumulation, GSH depletion, and downregulation of lipid peroxidase (GPX4) expression. Animal experiments confirmed that CPHT not only effectively inhibited the growth of tumors in situ but also significantly decelerated the growth of the distal tumor. Elevated levels of CD86 and IFN-γ and decreased expression of CD206 were observed at the tumor sites post CPHT treatment. These results confirmed the value of CPHT as a multifunctional nanoplatform that can tune the TME and provide new hope for tumor treatment.

A fluorescent probe for protein tyrosine kinase 7 detection in serum and cell imaging.

Tyrosine protein kinase 7 (PTK7) is overexpressed in breast cancer, which is considered as a cancer marker for breast cancer diagnosis. Therefore, a simple fluorescent probe for PTK7 detection and cell imaging was developed. In the developed probe, Fe3O4 magnetic nanoparticles were used as the fluorescent separator, and the fluorescence of carbon dots were used as the detection signal. The probe was worked by control the configurations of the aptamer of PTK7, the aptamer would be open chains by recognition of PTK7, which bond with carbon dots and show fluorescent signal. Based on the remarkably high affinity and selectivity of aptamer for PTK7, the excellent fluorescence property of carbon dots and the outstanding magnetism of Fe3O4 magnetic nanoparticles, the developed probe showed satisfied results for PTK7 detection in serum and MCF-7 cell imaging. The probe detected PTK7 in the range of 0.2-200 ng mL-1 with a detection limit of 0.0347 ng mL-1, and successfully imaged the cancer cell expressed PTK7. The results indicate that the nano-fluorescent probe has great potential for clinical applications.

Dual-emissive ratiometric fluorescent nanosensor based on multi-nanomaterials for Ag+ determination in lake water.

In this study, a sensitive ratiometric fluorescent nanosensor was constructed using a facile one-pot method by encapsulating carbon dots (CDs) and cadmium telluride quantum dots (CdTe QDs) into the pore cavities of a metal-organic framework (ZIF-8). In this nanosensor (CD/CdTe QD@ZIF-8), the fluorescence attributed to CdTe QDs was quenched by silver ions (Ag+), and the fluorescence intensity of CDs did not change. The introduction of ZIF-8 into the system can not only adsorb Ag+ but also easily separate CDs and CdTe QDs from the matrix. The developed CD/CdTe QD@ZIF-8 composite used as a ratiometric fluorescent probe exhibited high sensitivity and selectivity towards Ag+. The working linear range was 0.1-20 µM with a limit of detection (LOD) of 1.49 nM. Finally, the proposed nanosensor was applied to determine Ag+ in lake water with satisfactory results.

pH-Responsive Oxygen and Hydrogen Peroxide Self-Supplying Nanosystem for Photodynamic and Chemodynamic Therapy of Wound Infection.

The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has been continuously explored in the antibacterial aspect and has achieved more effective antibacterial effect than a single therapy. We design a pH-responsive O2 and H2O2 self-supplying zeolitic imidazolate framework-67 (ZIF-67) nanosystem for PDT/CDT of wound infection. Under the acidic inflammatory conditions, ZIF-67 can degrade to produce Co2+ and release CaO2 and graphene quantum dots (GQDs). The exposed CaO2 reacted with water to generate H2O2 and O2. The self-supplied O2 alleviates hypoxia at the site of inflammation and enhances external light-initiated GQD-mediated PDT, while H2O2 was catalyzed by endogenous Co2+ to produce hydroxyl radicals for Co2+-triggered CDT. In vitro and in vivo experiments confirm that CaO2/GQDs@ZIF-67 has a combined PDT/CDT effect. The antibacterial mechanism indicates that bacteria post-treated with CaO2/GQDs@ZIF-67 may be sterilized by reactive oxygen species-mediated oxidative stress and the leakage of bacterial contents. The experiments also find that CaO2/GQDs@ZIF-67 may activate the immune response and enhance the therapeutic effect by activating the cyclic GMP-AMP synthase-stimulator of interferon genes signaling pathway.

Sequential drug delivery by injectable macroporous hydrogels for combined photodynamic-chemotherapy.

With hollow mesoporous silica (hMSN) and injectable macroporous hydrogel (Gel) used as the internal and external drug-loading material respectively, a sequential drug delivery system DOX-CA4P@Gel was constructed, in which combretastatin A4 phosphate (CA4P) and doxorubicin (DOX) were both loaded. The anti-angiogenic drug, CA4P was initially released due to the degradation of Gel, followed by the anti-cell proliferative drug, DOX, released from hMSN in tumor microenvironment. Results showed that CA4P was mainly released at the early stage. At 48 h, CA4P release reached 71.08%, while DOX was only 24.39%. At 144 h, CA4P was 78.20%, while DOX release significantly increased to 61.60%, showing an obvious sequential release behavior. Photodynamic properties of porphyrin endow hydrogel (ϕΔ(Gel) = 0.91) with enhanced tumor therapy effect. In vitro and in vivo experiments showed that dual drugs treated groups have better tumor inhibition than solo drug under near infrared laser irradiation, indicating the effectivity of combined photodynamic-chemotherapy.

A novel sodium-fluorescent crystal.

In this work, a novel sodium-fluorescent crystal (Na-FS) was synthesized from 4-dimethylaminobenzoic acid and sodium hydroxide by one-pot hydrothermal method. The structure and conformation of Na-FS were confirmed by single-crystal X-ray diffraction and scanning electron microscope, and the optical properties were studied by fluorescence spectrometer. The results showed that: Na-FS was a triclinic crystal, space group was P-1, cell parameters a, b and c were 10.5113(3), 15.9198(5) and 15.9560(5) Å, respectively, and the number of independent atoms Z in a structure cell was two. Additionally, Na-FS has a blue fluorescence emission (around 360 nm under excited at the range of 230-300 nm) with great photostability and photobleaching resistance, and the quantum yield of Na-FS is 30.58%.

High-stabilized polydopamine modified low eutectic fatty acids based on near-infrared response for breast cancer therapy.

Low eutectic of lauric acid and stearic acid is one of drug loading candidates for its phase transformation at a certain temperature. Herein we demonstrated a combined photothermal-chemotherapy for breast cancer with near-infrared (NIR) triggered phase transition materials (PCM), which was conjugated with polydopamine (PDA) as the photosensitive agent. The PCM nanoparticles had diameters of ~75 nm based on scanning electron microscope (SEM) and dynamic laser scattering (DLS) measurement. Systematic in vitro and in vivo studies have been performed to investigate the stability, biosafety, photothermal performance, and drug delivery and release of PCM conjugates. Temperature measurement confirmed the prepared PDA modified material still showed strong photothermal effect after five cycles, which was higher than that of IR780 conjugated ones. In vivo photothermal imaging showed that the temperature of the tumor site reached 50.8 °C after 3 h of intravenous injection of PCM conjugates. More effective therapy of near-infrared (NIR)-assisted PDA-M@PCM in 4T1 bearing mice was witnessed when compared with that of non-NIR-assisted ones. Enhanced therapy in 4T1 tumor was demonstrated in DOX-loaded PDA-M@PCM by fluorescence imaging. This NIR-triggered PCM based nanoplatform can serve as useful tool for light-assisted combined tumor therapy.

Multi-carbon dots and aptamer based signal amplification ratiometric fluorescence probe for protein tyrosine kinase 7 detection.

BACKGROUND: Protein tyrosine kinase 7 (PTK 7) is a membrane receptor, which can be found in various kinds of cancers. In view of this, detection of PTK 7 in the peripheral circulation would be an effective way for the early diagnosis of cancer. RESULTS: In this work, a multi-carbon dots and aptamer-based signal amplification ratiometric fluorescence probe was developed. The fluorescence of the aptamer-modified y-CDs and b-CDs were respectively chosen as the detection signal and interior label. The fluorescence of y-CDs was quenched by Fe3O4 and cDNA (complement to aptamer) compound without PTK 7, but recovered by the addition of PTK 7. Then, the free aptamer was cut by DNase I, which amplified the detection signal. The ratiometric fluorescence sensor for PTK 7 was established with the LOD of 0.016 ng mL-1. CONCLUSIONS: Summary, a multi-carbon dots and aptamer-based signal amplification ratiometric fluorescence probe was developed for the detection of protein tyrosine kinase 7. The developed probe was applied to PTK 7 detection in MCF-7 cells and human serum with satisfying results, thus indicating that this probe has huge potential in clinical practice.

Segmented scan modes and polarity-based LC-MS for pharmacokinetic interaction study between Fufang Danshen Dripping Pill and Clopidogrel Bisulfate Tablet.

Fufang Danshen Dripping Pill (FDDP) and Clopidogrel Bisulfate Tablet (CBT) are usually combined for treatment of coronary artery diseases in clinical. To investigate the pharmacokinetic interaction between FDDP and CBT after oral administration of FDDP, CBT and their combination in rats, a novel LC-MS method with segmented scan modes (multiple reaction monitoring and selected ion monitoring) and polarity (positive and negative ionization) was developed. Clopidogrel and the main active ingredients of FDDP, with different chemical and ionization properties, were simultaneously quantified in plasma in a single run. The method was validated in terms of specificity, linearity, precision, accuracy, recovery, matrix effect and stability. As a result, co-administration of FDDP and CBT significantly altered the pharmacokinetic parameters of danshensu, ginsenoside Rb1, dihydrotanshinone I, tanshinone I and tanshinone IIA of FDDP, as well as clopidogrel. Mechanism studies suggested that induction of liver cytochrome P450 isozymes CYP2C11 and CYP3A1 by co-administration, as well as inhibition of carboxyl esterase 1, was partly responsible for FDDP-CBT pharmacokinetic interactions. The developed LC-MS method could be used to simultaneously quantify different types of in vivo analytes in a single run, and the results could be used for clinical medication guidance of FDDP and CBT.

Aptamer-based fluorescent platform for ultrasensitive adenosine detection utilizing Fe3O4 magnetic nanoparticles and silver nanoparticles.

The authors describe an aptamer-based fluorescent assay for adenosine (Ade). It is based on the interaction between silver nanoparticles (AgNPs) and CdTe quantum dots (QDs). The beacon comprises a pair of aptamers, one conjugated to Fe3O4 magnetic nanoparticles, the other to AgNPs. In the presence of Ade, structural folding and sandwich association of the two attachments takes place. After magnetic separation, the associated sandwich structures are exposed to the QDs. The AgNPs in sandwich structures act as the signaling label of Ade by quenching the fluorescence of QDs (at excitation/emission wavelengths of 370/565 nm) via inner filter effect, electron transfer and trapping processes. As a result, the fluorescence of QDs drops with increasing Ade concentration. The assay has a linear response in the 0.1 nM to 30 nM Ade concentration range and a 60 pM limit of detection. The assay only takes 40 min which is the shortest among the aptamer-based methods ever reported. The method was successfully applied to the detection of Ade in spiked biological samples and satisfactory recoveries were obtained. Graphical abstract Schematic of a highly efficient and convenient adenosine (Ade) fluorometric assay. It is based on the interaction between Ag nanoparticles (NPs) and CdTe quantum dots (QDs). Ade aptamers (ABA1 and ABA2) are used as recognition unit and Fe3O4 magnetic nanoparticles act as magnetic separator. The assay exhibits superior sensitivity and speediness.

"On-off-on" fluorescent system for detection of Zn2+ in biological samples using quantum dots-carbon dots ratiometric nanosensor.

In this work, a novel strategy for Zn2+ detection was established by using an "on-off-on" ratiometric fluorescent nanosensor with the help of ethylene diaminetetraacetic acid (EDTA), a common metal chelating agent. The simple and practical ratiometric fluorescent nanosensor was synthesized by covalently binding CdTe quantum dots (QDs) and carbon dots (CDs), possessing two emission peaks at 525 nm and 450 nm under a single wavelength excitation of 360 nm, respectively. The CdTe QDs served as the response signal label, and the CDs, having no response to the analytes, acted as the reference signal. The fluorescence emission of the nanosensor was turned off to create a low-level "off" state when EDTA was added, and turned on dramatically with the addition of the target Zn2+. Under the optimal conditions, the change of the fluorescence intensity ratio of the nanosensor at 525 nm and 450 nm (ΔF525/F450) had good linearity against the concentrations of Zn2+ within a dynamic linear range of 0.50-40 µM. The limit of detection was as low as 0.33 µM (3σ/K), which was low enough for the detection of Zn2+ in human body. The proposed method was successfully applied to the detection of Zn2+ in human urine and plasma with RSDs less than 10%. The results show that the as-prepared QDs-CDs ratiometric nanosensor has potential application of clinical detection of Zn2+ in the human body.

Carbon dots based immunosorbent assay for the determination of GFAP in human serum.

Glial fibrillary acidic protein (GFAP) is expressed in the central nervous system and the level of GFAP normally rises with brain injury and astroglial tumors. So, serum GFAP is used as a marker for diagnosing various types of brain damage and astroglial tumors. In this study, a new sensor based on carbon dots (CDs) linked with antibodies to specifically detect GFAP in human serum was developed. Anti-GFAP (Ab1) linked with protein A/G agarose resin (PA/G) as a capture antibody (PA/G-Ab1) and anti-GFAP (Ab2) labeled with CDs as a detection antibody (CDs-Ab2) were prepared firstly. Then the CD-linked antibody immunosorbent assay (CLAISA) method was constructed based on the sandwich conjunction reaction among PA/G-Ab1, GFAP, and CDs-Ab2. CLAISA, using the fluorescence of PA/G-Ab1-GFAP-Ab2-CDs as the direct signal, enabled the proposed immunosensor to detect GFAP sensitively with a linear range of 0.10-8.00 ng ml-1 and a detection limit of 25 pg ml-1. This method was applied to the determination of GFAP in human serum by the standard addition method, and the results showed high accuracy and precision. Considering the easy synthetic process and excellent performance of CLAISA, this method has great potential to be used to monitor GFAP in the clinic.

Determination of semicarbazide in fish by molecularly imprinted stir bar sorptive extraction coupled with high performance liquid chromatography.

A novel molecularly imprinted stir bar (MI-SB) for sorptive extraction of semicarbazide (SEM) was prepared in present paper. The coating of the stir bar was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, dynamic adsorption and static adsorption tests. The saturated adsorption of MI-SB was about 4 times over that of non-imprinted stir bar (NI-SB). The selectivity of MI-SB for SEM was much better than NI-SB. A method to determine SEM was established by coupling MI-SB sorptive extraction with HPLC-UV. The liner range was 1-100ng/mL for SEM with a correlation coefficient of 0.9985. The limit of detection was about 0.59ng/mL, which was below the minimum required performance limit of SEM in meat products regulated by European Union. The method was applied to the determination of SEM in fish samples with satisfactory results.

Determination of Verapamil HCl in Pharmaceutical Preparations by a Fluorescent Nano Probe Based on CdTe/CdS/ZnS Quantum Dots.

An analytical technique based on fluorescence quenching of CdTe/CdS/ZnS quantum dots (QDs) was developed to quantify verapamil in commercially available preparations. Various reaction parameters were optimized and the method developed was validated. One way analysis of variance (ANOVA) and post hoc tests at a 5% significance level were performed to justify the significance of the variation in observations. The linear range of the verapamil concentration was 0.25-5 µg/mL while the limit of detection was 20 µg/mL. Recovery and relative standard deviations were not more than ±10% of the actual amount and <5.9%, respectively. Foreign materials, common metal ions and pharmaceutical excipients of dosage forms caused little interference. To verify the application of the analytical method, the quantity of verapamil in commercially available dosage forms was measured. Verapamil content in the tablets and injections was not more than ±10% of the stated amount and it conformed to the specifications of both the British and the United States pharmacopoeias. In the case of statistical analysis, p-value was <0.05 in almost all levels of all parameters except for the optimized level of system. It can be concluded from the results that the designed method is simple, reliable, cost effective, selective, rapid and sensitive enough to be used for quantitative measurement of the verapamil HCl in dosage forms for quality control purposes.

Highly sensitive and selective aptasensor for detection of adenosine based on fluorescence resonance energy transfer from carbon dots to nano-graphite.

In this article, a novel aptasensor was fabricated by modifying carbon dots (CDs) with adenosine aptamer (CDs-aptamer) for sensitive, selective and quantitative detection of adenosine (AD). When nano-graphite (NG) as an energy acceptor was added into the CDs-aptamer (energy donor) solution, the fluorescence of CDs-aptamer was quenched due to fluorescence resonance energy transfer (FRET). When AD was present in the solution of CDs-aptamer/NG, the process of FRET was inhibited because of the specific combination between AD and AD aptamer. As a result, the fluorescence of CDs-aptamer was restored due to the dissociation of CDs-aptamer from NG and its change was proportional to the AD concentration. Under the optimized conditions, a linear range was found to be 2-50nM for the detection of AD with a detection limit of 0.63nM. Furthermore, the application of the proposed approach was demonstrated in real sample with satisfying results and it showed promise in diagnostic purpose.

A Ratiometric Fluorescence Universal Platform Based on N, Cu Codoped Carbon Dots to Detect Metabolites Participating in H2O2-Generation Reactions.

In this work, a new kind of N, Cu codoped carbon dots (N/Cu-CDs) was prepared via a facile one-pot hydrothermal method by using citric acid monohydrate, copper acetate monohydrate and diethylenetriamine. The prepared N/Cu-CDs with a high quantum yield (50.1%) showed excitation-independent emission at 460 nm. The structure and fluorescence properties of N/Cu-CDs were characterized by high-resolution transmission electron microscopy, fluorescence spectrofluorometer, FT-IR spectrometer, UV-visible spectrophotometer and X-ray photoelectron spectroscopy. N/Cu-CDs were applied to establishing a ratiometric fluorescence probe toward H2O2 based on the inner filter effect (IFE) between N/Cu-CDs and DAP (2,3-diaminophenazine, the oxidative product of o-phenylenediamine (OPD)), and provided a ratiometric fluorescence universal platform for detection of the metabolites participating in H2O2-generation reactions (cholesterol and xanthine). The proposed method was demonstrated to be ultrasensitive and highly selective for cholesterol and xanthine assay with detection limits of 0.03 and 0.10 µM, respectively. The fluorescence probe built was applied to the determination of cholesterol and xanthine in human serum with satisfactory results.

Simultaneous quantification of antofloxacin and its major metabolite in human urine by HPLC-MS/MS, and its application to a pharmacokinetic study.

This study presents a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the simultaneous determination of antofloxacinin and its main metabolite - N-demethylated metabolite (N-DM) - in human urine. Ornidazole was used as the internal standard. This was a clinical urine recovery study, in which 10 healthy Chinese volunteers were intravenously administered a single 200 mg dose of antofloxacin hydrochloride. Compounds were extracted by albumen precipitation, after which samples were isocratically eluted using a Poroshell 120 SB-C18 column, and were analysed using HPLC-MS/MS under electronic spray ionization positive ion mode. The method was successfully applied in a urine pharmacokinetic study of antofloxacinin, with a detection range of 0.02/0.01 to 200/100 µg/mL (for antofioxacin/N-DM).The average percentages of antofioxacin/N-DM measured in urinary excretion frp, 10 volunteers were 54.9 ± 5.7/8.2 ± 2.5% in 120 h duration.

Pharmacokinetics of ginkgolides A, B and K after single and multiple intravenous infusions and their interactions with midazolam in healthy Chinese male subjects.

PURPOSE: Ginkgo terpene lactones meglumine injection (GMI) is a novel preparation of traditional Chinese medicine that contains ginkgolides A, B and K (GA, GB, GK, respectively) as its primary components. In this study we evaluated the safety, tolerability and pharmacokinetics of these three ginkgolides after single and multiple intravenous infusions of GMI. We also investigated the effect of GMI on cytochrome P450 3A4 (CYP3A4) in healthy Chinese volunteers. METHODS: In this open-label, placebo-controlled study 15 subjects were randomly assigned to receive GMI or matched placebo (4:1 ratio). All subjects first received midazolam (MDZ) on day 1, followed by a 6-day washout. On Day 8, the subjects were started on once-daily dosing of either GMI or placebo for 14 days. Lastly, on Day 22 the subjects were given second dose of MDZ + GMI or MDZ + placebo. Plasma concentrations of ginkgolides, MDZ and its metabolite 1-hydroxy midazolam were quantified. RESULTS: The steady-state conditions of GA, GB and GK were achieved after 6 days of daily dosing. Following a single dose of GMI (Day 8) the area under the concentration-timecurve from zero to 24 h after administration (AUC0-24h) of GA, GB and GK (arithmetic ± standard deviation) was 4.10 ± 1.06, 4.61 ± 1.31 and 0.127 ± 0.102 h µg/mL, respectively; the corresponding values following multiple doses of GMI (Day 19) were 3.94 ± 1.16, 5.00 ± 1.55 and 0.118 ± 0.096 h µg/mL, respectively. The mean accumulation ratios were 0.95, 1.08 and 0.89 for GA, GB and GK, respectively. Additionally, the geometric mean [peak concentration (Cmax) and AUC0-24h] ratios of MDZ and 1-hydroxy midazolam were all within the specified acceptance ranges in the MDZ + placebo treatment and MDZ + GMI treatment. CONCLUSIONS: Our results show that GMI was well tolerated during the entire study. There was no systemic accumulation and no significant effects on the pharmacokinetics of MDZ in healthy Chinese male subjects after repeated dosing of GMI.

Aptamer based fluorometric ß-lactoglobulin assay based on the use of magnetic nanoparticles and carbon dots.

The authors describe a fluorometric aptamer based assay for detecting ß-lactoglobulin by using carbon dots (C-dots) as a signal indicator. The aptamer was immoblized on magnetite (Fe3O4) nanoparticles (MNPs), and the C-dots served as a label for the complementary oligonucleotide (cDNA). The assay is based on the hybridization that takes place between aptamer and cDNA. In the presence of ß-lactoglobulin (ß-LG), the aptamer preferentially binds to ß-LG, and this leads to a partial release of the C-dots-cDNA into the solution. After magnetic separation, the supernatant of the solution contains the released C-dots-cDNA which are quantified by fluorometry, best under excitation/emission wavelengths of 354/447 nm. Under the optimal conditions, the fluorescence intensity is proportional to the logarithm of the ß-LG concentration in the 0.25 to 50 ng mL-1 range, with a 37 pg mL-1 detection limit. The method was successfully applied to the determination of ß-LG in hypoallergenic formulations, and the results demonstrated that this assay is a promising tool in food quality control. Conceivably, it also provides the opportunity for detection of other analytes. Graphical abstract Schematic of a novel aptamer based fluorometric ß-lactoglobulin assay based on the use of magnetite (Fe3O4) nanoparticles (MNPs) and carbon dots (C-dots). C-dots were used as a signal indicator and Fe3O4 MNPs acted as a magnetic separator. This assay exhibits high sensitivity and selectivity with a detection limit as low as 37 pg mL-1.