D-penicillamine (D-PEN) is used to treat Wilson's disease, rheumatoid arthritis, and cystinuria but requires careful monitoring due to its narrow therapeutic window and risks of nephrotoxicity, hematological disorders, and autoimmune reactions. To enable reliable detection, bimetallic FeCu co-doped carbon dots (FeCu@CDs) were developed as multifunctional nanozymes for dual-mode sensing of D-PEN. These nanozymes integrate peroxidase-like catalytic activity, intrinsic fluorescence, and selective thiol-binding affinity, allowing simultaneous colorimetric and ratiometric fluorescence detection. Fe and Cu doping enhanced the peroxidase-like activity and fluorescence emission of the CDs by promoting H₂O₂ activation into HO• and ¹O₂ and improving charge mobility. D-PEN inhibited this catalytic activity by binding metal centers and altered the inner filter effect (IFE) between FeCu@CDs and 2, 3-diaminophenazine (DAP), enabling selective signal modulation. The assay achieved detection limits of 0.13 μM (colorimetric) and 0.03 μM (fluorescence), with recoveries ranging from 95.6 % to 105.1 % in real samples, highlighting its importance in clinical monitoring and bioanalytical applications.

Capmatinib (CMB) monitoring in biological fluids is critical for evaluating its pharmacokinetics, optimizing
dosing, and minimizing toxicity. Accurate measurement is essential for ensuring therapeutic efficacy,
enabling personalized treatment, and preventing adverse effects. Given the variability in patient
metabolism and excretion, regular monitoring helps maintain CMB levels within the therapeutic range,
improving treatment outcomes and minimizing the risk of drug resistance. This work presents an
economical and energy-efficient strategy for preparing highly luminescent nitrogen-doped carbon dots
(NCDs), employing 2,5-dihydroxy-1,4-benzoquinone alongside triethylenetetramine. The synthesized
NCDs demonstrated excellent photostability and a high fluorescence quantum yield of 38.72%. Upon the
addition of CMB, concentration-dependent fluorescence quenching was observed at 515 nm, which was
attributed to the inner filter effect (IFE), with LOD of 3.6 nM. The NCDs exhibited high selectivity in
detecting CMB, with minimal cross-reactivity from simultaneously present compounds. Recovery studies
in real biological samples yielded rates between 97.4% and 105.3%, and RSDs were consistently below
4.11%. These results demonstrate the method's precision, reproducibility, and potential for reliable CMB
detection in complex biological matrices.

Monitoring nintedanib (NTB) using reliable analytical methods is essential for ensuring safe dosing, minimizing toxicity, assessing drug–drug interactions, and supporting quality control in personalized cancer therapy. In this work, we present a cost-effective and energy-efficient hydrothermal strategy for synthesizing nitrogen-doped carbon dots (CDs) from disposable plastic syringes. The process, carried out at 200 °C following a calcination pretreatment, not only provides a sustainable route for valorizing biomedical waste but also addresses pressing environmental challenges. The as-prepared CDs exhibited intense green fluorescence, outstanding photostability, and a high quantum yield of 46.42%, reflecting their superior optical performance. Upon exposure to NTB, a concentration-dependent quenching response at 470 nm was observed, primarily mediated by the inner filter effect (IFE). This mechanism enabled highly sensitive NTB detection, with an ultralow detection limit of 2.5 nM (S/N = 3). The probe demonstrated remarkable selectivity, showing negligible interference from common coexisting ions, biomolecules, and anticancer drugs. Analytical accuracy was validated by recovery studies in spiked serum and urine samples, which ranged from 97.6% to 103.2%, while RSD values below 3.48% confirmed excellent precision and reproducibility. These findings establish the proposed CD-based probe as a robust, reproducible, and clinically relevant tool for NTB quantification. By demonstrating the conversion of discarded medical plastics into high-value nanomaterials, this work presents a strategy that aligns with the goals of green nanotechnology and delivers a practical platform for bioanalytical sensing, therapeutic drug monitoring, and pharmacokinetic studies. The dual focus on waste repurposing and clinical utility underscores the potential the potential of syringe plastic-derived CDs for translation into next-generation biomedical diagnostics.

Erdafitinib (ERDF), despite its known adverse effects, remains a key chemotherapeutic agent for metastatic urothelial carcinoma, requiring reliable monitoring in biological matrices to ensure safe and effective treatment. In this study, we developed a cost-effective, energy-efficient method for synthesizing highly fluorescent nitrogen-doped carbon dots (NCDs) using simple precursors. The resulting NCDs displayed excellent photostability and a high fluorescence quantum yield of 41.87%. ERDF induced a concentration-dependent quenching of the NCDs' fluorescence at 520 nm, attributed to the inner filter effect, with a low detection limit of 0.013 μM (S/N = 3). The NCDs demonstrated high selectivity toward ERDF with minimal interference from coexisting substances. Recovery rates in spiked human serum and urine ranged from 97.8% to 104.4%, validating the method's practical applicability. The relative standard deviations (RSDs) remained below 3.72%, confirming the precision and reproducibility of the NCD-based sensing platform.

Purine bases such as adenine and guanine are fundamental components of nucleic acids and are involved in critical metabolic processes. Abnormal elevations in their concentrations have been associated with various pathological conditions, including cancer. In this study, a highly sensitive voltammetric sensor was developed by modifying a glassy carbon electrode (GCE) with nickel ferrite nanoparticles (NiFe₂O₄ NPs) anchored onto halloysite nanotubes (HNTs), forming a NiFe₂O₄ NPs@HNTs composite. The synergistic integration of redox-active NiFe₂O₄ NPs and high-surface-area, biocompatible HNTs significantly enhanced the electrochemical response by increasing the active surface area, improving electron transfer kinetics, and facilitating strong analyte adsorption. This composite enabled well-defined, irreversible oxidation peaks for both adenine and guanine, with a wide linear detection range from 0.05 to 200 μM. The calculated limits of detection (LODs) were 2.2 nM for adenine and 1.4 nM for guanine, indicating excellent sensitivity. When tested in pre-treated human saliva and serum samples, the sensor achieved recovery rates ranging from 95.7% to 105.2%, with relative standard deviations below 4.21%, confirming its accuracy and reliability in complex biological matrices. These findings highlight the sensor’s strong potential for future clinical applications in purine base monitoring and biomarker-based disease diagnostics.