Search Results (328)

The modification of tantalum oxide (Ta₂O₅) nanoparticles (NPs) with biocompatible polymers is crucial for their biomedical use. Such modification can prolong NP circulation in the bloodstream by minimizing salt-induced aggregation and reducing nonspecific protein adsorption onto their surface. Understanding the features of polymer–NP interactions is a key issue in the fabrication of nanostructures with required characteristics. The present work aims to provide a comprehensive comparative study of bovine serum albumin (BSA) adsorption on bare and polydopamine (PDA)-coated Ta₂O₅ NPs. The synthesized NPs were characterized via transmission electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential measurements. Fluorescence and circular dichroism spectroscopy were also employed for the first-time investigation of the interactions of Ta₂O₅ NPs and Ta₂O₅@PDA NPs with BSA. The results obtained show that PDA coating significantly enhances the protein-binding affinity. Time-resolved measurements revealed signatures of Förster resonance energy transfer, confirming complex formation between NPs and BSA. Moreover, colloidal stability tests in phosphate-buffered saline indicated that the presence of adsorbed BSA improves the dispersion stability of bare and PDA-coated Ta₂O₅ NPs. These findings advance the understanding of protein–NP interactions and highlight the potential of PDA coatings for designing stable and functional nanostructures for biomedical applications. Full article

Nanosurface energy transfer (NSET) has emerged as a pivotal mechanism in nanobiophotonics, facilitating the development of highly sensitive biosensors with extended dynamic ranges. Unlike conventional Förster resonance energy transfer, NSET exhibits an inverse fourth-power dependence on distance, enabling quantitative measurements over distances up to 40 nm. This review comprehensively explores the fundamental principles governing NSET, with particular emphasis on non-radiative coupling between fluorescent donors and metallic nanostructures such as gold nanoparticles. Additionally, the applications of these probes are surveyed across various bioanalytical domains, including nucleic acid assays, immunoassays, real-time intracellular monitoring, and various biomolecule detection. Additionally, the evolving integration of NSET, plasmonics, and nanophotonic architectures is discussed, focusing on emerging trends and the trajectory for developing next-generation, multiplexed, and point-of-care diagnostic platforms. Current challenges and prospective pathways for translating these advanced sensing systems into clinical and field-deployable solutions are also considered. Full article

Fibroblast activation protein (FAP), a transmembrane serine protease expressed primarily in pathological conditions, plays a pivotal role in tumor progression. Despite extensive studies on FAP in solid tumors, its role in hematologic cancers, particularly lymphoid malignancies, remains underexplored. This study aimed to investigate the level and activity of soluble FAP (sFAP) in pre-therapeutic serum samples from 120 lymphoma patients. We measured sFAP serum levels using time-resolved immunofluorometric assay and sFAP activity with Förster resonance energy transfer assay. In addition, immunohistochemistry was used to analyze intratumoral FAP expression in tissue biopsies from a subset of B-cell lymphoma patients (n = 34). Notably, the results revealed significantly reduced circulating sFAP levels (p = 0.002) and activity (p < 0.001) in aggressive disease subtypes compared with indolent subtypes and healthy individuals. At the time of diagnosis, low sFAP activity correlated with inferior overall survival (both p < 0.001) in patients with the aggressive entities, suggesting altered FAP functionality in these tumors. Interestingly, measuring intratumoral FAP levels revealed an inverse pattern, with diffuse large B-cell lymphoma showing higher tissue FAP localization compared with follicular lymphoma (p < 0.001). These findings provide new insights into the biological and clinical significance of FAP in lymphoid malignancies, particularly highlighting the importance of sFAP activity as a potential prognostic marker in aggressive lymphoid malignancies. Full article

Yeast +1 nucleosomes positioned at transcription start sites must be reorganized to allow transcription initiation. Nucleosome reorganization involves multiple factors including histone chaperone FACT (FAcilitates Chromatin Transcription), histone acetylation, and histone variant H2A.Z; however, the mechanism of this process is not fully understood. Here we investigated nucleosome unfolding in the presence of these factors by combining biochemical assays with single-particle Förster resonance energy transfer (spFRET) microscopy. The presence of the H3:K56Ac mimic (H3:K56Q) alone or together with H2A.Z (but not H2A.Z alone) facilitates the Nhp6-dependent unfolding of nucleosomes by FACT. In contrast to canonical nucleosomes, the unfolding of nucleosomes with the studied variant histones promotes the eviction of core histones from nucleosomal DNA. Furthermore, H2A.Z alone or in synergy with H3:K56Q facilitates transcription through a nucleosome as efficiently as FACT facilitates transcription through canonical nucleosomes. The data suggest that FACT, together with H3:K56 acetylation and H2A.Z, unfold promoter nucleosomes and participate in the eviction of histones to increase the accessibility of the transcription start site, thereby stimulating transcription initiation and possibly early elongation. Full article

Achieving long-lived room-temperature phosphorescence (RTP) with high quantum efficiency is of significant interest for applications in anti-counterfeiting, flexible optoelectronic displays, and multi-level information encryption. Here, we presented a hydrogen-bond engineering strategy to enhance RTP performance by progressively increasing the number of hydrogen-bonding sites within a polyvinyl alcohol (PVA) matrix. A series of carbazole-based chromophores (Cz, ICz and 2ICz) were embedded into the PVA network, and their photophysical properties were systematically characterized using steady-state photoluminescence spectra, time-decay spectra, Fourier-transform infrared (FTIR), and Raman and X-ray photoelectron spectroscopy (XPS). Spectroscopic analysis revealed that the increased number of N-H groups significantly strengthened hydrogen-bonding interactions, effectively suppressing non-radiative decay pathways and stabilizing triplet excitons. As a result, the phosphorescence lifetime was prolonged up to 1.68 s with a quantum yield of 38.63%. Furthermore, leveraging the spectral overlap integral between the phosphorescent emission and dye absorption, efficient Förster resonance energy transfer (FRET) was realized, enabling tunable multi-color afterglow emissions. This study establishes a design strategy validated by spectroscopy for high-performance RTP materials and highlights their promising potential in advanced optical encryption and flexible photonic applications. Full article

The efficacy of X-ray-induced photodynamic therapy (X-PDT) for deep tumors is often hindered by conventional scintillators, typically rare-earth nanoparticles plagued by long-term toxicity and suboptimal scintillation yields. Here, we introduce a copper iodide (Cu-I) cluster, Cu₂I₂(PPh₃)₂(pz), composed of earth-abundant elements, as an efficient and biocompatible energy transducer for X-PDT. A theranostic nanoplatform, CuI@PcNP, was engineered by co-encapsulating the Cu-I cluster and a phthalocyanine photosensitizer (Pc4OH) within a 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-polyethylene glycol-2000 (DSPE-PEG2K) matrix, which confers excellent physiological stability. This nano-architecture ensures nanoscale proximity between the cluster (donor) and photosensitizer (acceptor), facilitating efficient (58%) Förster resonance energy transfer (FRET) while overcoming aggregation-induced quenching. Upon X-ray irradiation, the platform effectively converted X-rays to visible light, activating Pc4OH to generate potent reactive oxygen species (ROS) and inducing significant dose-dependent cytotoxicity in human hepatocellular carcinoma (HepG2) cells. In a murine hepatoma model, enabling image-guided X-PDT that resulted in a 77.4% tumor inhibition rate with negligible systemic toxicity. Collectively, this work pioneers the integration of phthalocyanine with Cu-I clusters, providing a stable and versatile nanoplatform for image-guided X-PDT. Full article

This study presents a novel ratiometric fluorescent sensor based on Förster resonance energy transfer (FRET) between glutathione (GSH)-coated CdTe quantum dots (CdTe/GSH QDs) and bovine serum albumin (BSA)-coated Au nanoclusters (AuNCs/BSA) for dopamine (DA) detection. The nanoparticles were characterized using transmission electron microscopy (TEM), zeta potential measurements, Fourier transform infrared (FTIR) spectroscopy, UV-Vis absorption and fluorescence spectroscopy. Key FRET parameters, including energy transfer efficiency (E), donor–acceptor distance (r), Förster distance (R₀), and the overlap integral (J), were determined. The interactions between the CdTe/GSH-AuNCs/BSA conjugate and DA were investigated, revealing a dual mechanism of QDs fluorescence quenching that involves both energy and electron transfer. The average lifetime values and spectral profiles of CdTe/GSH QDs, both in the absence and presence of DA, suggest a dynamic fluorescence quenching process. The variation in the ratiometric signal with increasing DA concentration demonstrated a linear response within the range of 0–250 µM, with a correlation coefficient of 0.9963 and a detection limit of 6.9 nM. This proposed nanosensor exhibited selectivity against potential interfering substances, including urea, glucose, BSA, GSH, citric acid, and metal ions such as Na⁺ and Ca²⁺. The conjugate also demonstrates excellent cytocompatibility and enhances cell proliferation in HeLa epithelial cells, making it suitable for biological applications. It was successfully employed for DA detection in urine samples, achieving recoveries ranging from 99.1% to 104.2%. The sensor is highly sensitive, selective, rapid, and cost-effective, representing a promising alternative for DA detection across various sample types. Full article

Most biomarkers exhibit abnormal expression in more than one disease, making conventional single-biomarker detection strategies prone to false-negative results. Detecting multiple biomarkers associated with a single disease can therefore substantially improve diagnostic accuracy. Accordingly, recent research has focused on precise multiplex detection, leading to the development of sensors employing various readout methods, including electrochemical, fluorescence, Raman, and colorimetric approaches. This review focuses on optical sensing applications, such as fluorescence, Raman spectroscopy, and colorimetry, which offer rapid and straightforward detection and are well suited for point-of-care testing (POCT). These optical sensors exploit nanoscale phenomena derived from the intrinsic properties of nanomaterials, including metal-enhanced fluorescence (MEF), Förster resonance energy transfer (FRET), and surface-enhanced Raman scattering (SERS), which can be tailored through modifications in material type and structure. We summarize the types and properties of commonly used nanomaterials, including plasmonic and carbon-based nanoparticles, and provide a comprehensive overview of recent advances in multiplex biomarker detection. Furthermore, we address the potential of these nanosensors for clinical translation and POCT applications, highlighting their relevance for next-generation disease diagnostic platforms. Full article

Mutation T226R in the Kv1.1 α-subunit of voltage-gated potassium Kv1 channels is associated with episodic ataxia type 1, severe neuromyotonia, and epilepsy. In vitro, this mutation was reported to considerably distort the functioning of homotetrameric channels Kv1.1; however, in the brain, Kv1.1 α-subunits form heterochannels predominantly associating with Kv1.2 α-subunits. Using the patch-clamp technique, fluorescent and Förster resonance energy transfer confocal microscopy, we revealed that heterochannels Kv(1.1(T226R)-1.2)₂ formed by concatemers Kv1.1(T226R)-Kv1.2 in Neuro-2a cells have significantly slower activation and deactivation rates, and their activation occurs at a much less negative membrane potential compared to channels Kv(1.1-1.2)₂ formed by concatemers Kv1.1-Kv1.2. This mutation does not noticeably affect the formation of complexes between α-subunits Kv1.1 and Kv1.2, but it does induce a delayed and possibly decreased presentation of heterochannels Kv(1.1(T226R)-1.2)₂ on the plasma membrane. At the same time, the T226R mutation has a much stronger negative effect on the membrane presentation of homotetrameric Kv1.1 channels. Since heterochannels Kv1.1-Kv1.2 but not homotetrameric channels Kv1.1 are present in the brain, the heterochannels bearing mutation T226R are most likely underlying the pathogenesis of the disease by decreasing the responsiveness of cells to mild membrane depolarization and, thus, increasing the excitability of neurons. Full article

Adenosine triphosphate (ATP) is readily released into the extracellular space as an autocrine and paracrine purinergic signaling molecule. We originally reported a genetically encoded, fluorescent protein-based Förster Resonance Energy Transfer (FRET) biosensor that can detect micromolar levels of extracellular ATP. Through mutagenesis of the ATP binding site and optimization of cell-surface display, here we report the development of a second-generation biosensor called ECATS2 with greater than three-fold higher affinity for extracellular ATP. We found that the tether length between the FRET biosensor and the cell surface anchor is critical to optimization of its performance. Furthermore, we demonstrate that the improved sensor can detect extracellular ATP release upon hypoosmotic stress in cultured astrocytes. This new sensor contributes an improved tool for the ratiometric detection of extracellular ATP dynamics and purinergic signaling. Full article

We fabricated dye-sensitized solar cells (DSSCs) co-sensitized with the organic dye YD2 and a spiropyran derivative (SPNO₂), a photochromic molecule capable of reversible isomerization under light irradiation. Upon UV exposure, SPNO₂ converts from its closed spiropyran (SP) form to the open photomerocyanine (PMC) form, which absorbs visible light and changes the optical properties of the photoelectrode. Spectroscopic analysis showed an 18% decrease in transmittance at 540 nm after UV irradiation and a 10% increase following visible light exposure. These changes were accompanied by a 0.5% increase in power conversion efficiency (η) after 5 min of UV irradiation, and a 0.83% decrease after 10 min of visible light. Although direct electron injection from PMC into TiO₂ appears inefficient, the enhanced performance is attributed to Förster resonance energy transfer (FRET) from PMC to YD2. This photoresponsive behavior highlights a co-sensitization strategy that combines dynamic optical control and efficient energy transfer. Our findings demonstrate a promising approach to designing smart DSSCs with externally tunable photovoltaic properties using photochromic sensitizers. Full article

Icariin (ICA) is widely recognized for its health benefits. In this work, we examined the intermolecular interactions between ICA and proteinase K (PK) via multi-spectroscopic techniques and molecular simulations. The experimental findings revealed that ICA quenched the fluorescence emission of PK by forming a noncovalent complex. Both hydrogen bonding and van der Waals interactions are essential for the complex’s formation. Then Förster resonance energy transfer (FRET), competitive experiments, and synchronous fluorescence spectroscopy were adopted to verify the formation of the complex. Molecular docking studies demonstrated that ICA could spontaneously bind to PK by hydrogen bonding and hydrophobic interactions, which is consistent with the spectroscopic results. The PK-ICA complex’s dynamic stability was evaluated using a 50 ns molecular dynamics (MD) simulation. The simulation results revealed no significant structural deformation or positional changes throughout the entire simulation period. The complex appears to be rather stable, as seen by the average root-mean-square deviation (RMSD) fluctuations for the host protein in the PK-ICA complex of 1.08 Å and 3.09 Å. These outcomes of molecular simulations suggest that ICA interacts spontaneously and tightly with PK, consistent with the spectroscopic findings. The approach employed in this research presents a pragmatic and advantageous method for examining protein–ligand interactions, as evidenced by the concordance between empirical and theoretical findings. Full article

Förster resonance energy transfer (FRET)-based biosensors are versatile tools for obtaining insights into various biological processes. Their working principles are based on nonradiative energy transfer from donor to acceptor fluorophores. This energy transfer is responsible for a change in fluorescence intensity, which provides a basis for the detection of biomolecules. Advantageous features of FRET biosensors include their high sensitivity and specificity. Recently, there have been notable developments to extend the usage of FRET biosensors for diverse applications. In this review, we briefly summarize the state-of-the-art developments of FRET biosensors for cellular imaging, drug discovery, pathogen detection, and cancer diagnosis. Continued research on biosensor design, donor acceptor pair optimization, and integration of innovative materials can further extend the applications of FRET biosensors across health care settings. Full article

A fluorescent sandwich assay was devised to quantify CK-MB. In a typical immunoassay, antibodies bind to the target, and the detected signal is quantified according to the target’s concentration. We innovated a unique fluorescence assay known as the “enzyme-linked aptamer assay” (ELAA) by substituting antibodies with a pair of high-affinity aptamers labelled with biotin, namely apt. A1 and apt. A2. Avidin-labelled ALP binds to biotin-labelled aptamers, hydrolyzing its substrate, 2-phosphoascorbic acid trisodium salt, resulting in the formation of ascorbic acid. The catalytic hydrolysate functions as a reducing agent, causing the deterioration of MoS₂ nanosheets. This results in the transformation of MoS₂ nanosheets into nanoribbons, leading to the release of quenched AGQDs. The reestablishment of fluorescence is triggered by Förster Resonance Energy Transfer (FRET) between the MoS₂ nanoribbons and AGQDs, enhancing the sensitivity of disease biomarker detection. The working range for detection falls between 2.5 nM and 160 nM, and the limit of detection (LOD) for CK-MB is verified at 0.20 nM. Full article

Droplet microfluidics has emerged as a transformative technology that can substantially increase the throughput of antibody “hit” discovery. This review provides a comprehensive overview of the recent advances in this dynamic field, focusing primarily on the technological and methodological innovations that have enhanced the antibody discovery process. This investigation starts with the fundamental principles of droplet microfluidics, emphasizing its unique capabilities for precisely controlling and manipulating picoliter-volume droplets. This discussion extends to various assay types employed in droplet microfluidics, including binding assays, functional assays, Förster Resonance Energy Transfer (FRET) assays, internalization assays, and neutralization assays, each offering distinct advantages for antibody screening and characterization. A critical examination of methods to improve droplet encapsulation is presented, besides addressing challenges such as reducing the leakage of small molecules from droplets and explaining what a “hit” droplet looks like. Furthermore, we assess design considerations essential for implementing high-throughput fluorescence-activated droplet sorting (FADS) workstations and emphasize the need for automation. This review also delves into the evolving commercial landscape, identifying key market players and emerging industry trends. This review paper aims to catalyze further research and innovation, ultimately advancing the field towards more efficient and robust solutions for antibody identification and development. Full article