A selective BODIPY-based fluorescent sensor for the detection of Cu2+ ions in biological and environmental samples

Abstract: In this study, we present the design, synthesis, and characterization of a ’turn-on’ fluorescent probe, BOD-HDZ, for the selective detection of Cu2+ ions in semi-aqueous solutions, environmental samples (water and soil), and MCF-7 cancer cells. BOD-HDZ was synthesized by functionalizing meso-formyl-BODIPY (BOD-ALD) with a 2-hydrazinopyridine, resulting in fluorescence quenching via a photoinduced electron transfer (PET) mechanism. The 1:1 coordination between Cu2+ and the probe was confirmed through Job’s plot analysis and 1H NMR spectroscopy, leading to a 210-fold fluorescence enhancement at 515 nm. BOD-HDZ demonstrated exceptional sensing properties, including a rapid response time (<1 min), a broad operational pH range (2–12), and high sensitivity with a detection limit of 141 nM.

Electrospun Nanofiber Platforms for Photodynamic Therapy: Role and Efficacy in Cancer, Antimicrobial, and Wound Healing Applications

Abstract: Electrospinning offers a versatile platform for developing nanofibrous scaffolds capable of enhancing the therapeutic potential of photodynamic therapy (PDT). Photosensitizer (PS) loaded fibers exhibit a high surface area-to-volume ratio, promoting efficient drug delivery, prolonged retention at the target site, and controlled release profiles. Inducing reactive oxygen species (ROS) generation through light activation offers a targeted therapeutic approach, selectively generating cytotoxic effects in cancerous or pathogenic cells while minimizing damage to healthy tissue. This selective cytotoxicity arises because the ROS are produced only in illuminated areas where PS releases and accumulates, limiting their harmful effects to desired regions. Additionally, PS-loaded fibers are highly effective in wound healing applications, promoting cell proliferation and tissue regeneration while providing a barrier against microbial infections. This review highlights recent advances in the design and biomedical application of PS-loaded nanofibers, emphasizing their influence on cell viability and effectiveness in microbial inhibition, thereby setting the stage for future innovations in cancer therapy, wound healing, and infection control.

A Long Fluorescence Lifetime Probe for Labeling of Gram-Negative Bacteria

Abstract: Bacterial resistance, primarily stemming from misdiagnosis, misuse, and overuse of antibacterial medications in humans and animals, is a pressing issue. To address this, we focused on developing a fluorescent probe for the detection of bacteria, with a unique feature─an exceptionally long fluorescence lifetime, to overcome autofluorescence limitations in biological samples. The polymyxin-based probe (ADOTA-PMX) selectively targets Gram-negative bacteria and used the red-emitting fluorophore azadioxatriangulenium (with a reported fluorescence lifetime of 19.5 ns). Evaluation of ADOTA-PMX’s bacterial labeling efficacy revealed strong specificity for Gram-negative bacteria, and full spectral fluorescence lifetime imaging microscopy demonstrated the potential of ADOTA-PMX for bacterial imaging applications. The probe exhibited a lifetime of 4.5 ns when bound to bacteria, possibly indicating interactions with the bacterial outer membrane. Furthermore, the fluorescence lifetime measurements of ADOTA-PMX labeled bacteria could be performed using a benchtop fluorimeter without the need of sophisticated microscopes. This study represents the first targeted probe for fluorescence lifetime imaging, offering sensitivity for detecting Gram-negative bacteria and enabling multiplexing via fluorescence lifetime imaging.

Computational Model-Assisted Development of a Nonenzymatic Fluorescent Glucose-Sensing Assay

Abstract: Deep-red fluorescence was implemented in this fully injectable, nonenzymatic glucose biosensor design to allow for better light penetration through the skin, particularly for darker skin tones. In this work, a novel method was developed to synthesize Cy5.5 labeled mannose conjugates (Cy5.5-mannobiose, Cy5.5-mannotriose, and Cy5.5-mannotetraose) to act as the fluorescent competing ligand in a competitive binding assay with the protein Concanavalin A acting as the recognition molecule. Using fluorescence anisotropy (FA) data, a computational model was developed to determine optimal concentration ratios of the assay components to allow for sensitive glucose measurements within the physiological range. The model was experimentally validated by measuring the glucose response via FA of the three Cy5.5-labeled mannose conjugates synthesized with Cy5.5-mannotetraose demonstrating the most sensitive response to glucose across the physiological range. The developed method may be broadly applied to a vast range of commercially available fluorescent dyes and opens up opportunities for glucose measurements using nonenzymatic assays.

Transdermal Sensing of Enzyme Biomarker Enabled by Chemo‐Responsive Probe‐Modified Epidermal Microneedle Patch in Human Skin Tissue

Abstract: Wearable bioelectronics represents a significant breakthrough in healthcare settings, particularly in (bio)sensing which offers an alternative way to track individual health for diagnostics and therapy. However, there has been no notable improvement in the field of cancer, particularly for skin cancer. Here, a wearable bioelectronic patch is established for transdermal sensing of the melanoma biomarker, tyrosinase (Tyr), using a microneedle array integrated with a surface-bound chemo-responsive smart probe to enable target-specific electrochemical detection of Tyr directly from human skin tissue. The results presented herein demonstrate the feasibility of a transdermal microneedle sensor for direct quantification of enzyme biomarkers in an ex vivo skin model. Initial performance analysis of the transdermal microneedle sensor proves that the designed methodology can be an alternative for fast and reliable diagnosis of melanoma and the evaluation of skin moles. The innovative approach presented here may revolutionize the landscape of skin monitoring by offering a nondisruptive means for continuous surveillance and timely intervention of skin anomalies, such as inflammatory skin diseases or allergies and can be extended to the screening of multiple responses of complementary biomarkers with simple modification in device design.

A novel 2-aminophenalenone-based fluorescent probe designed for monitoring H2O2 for in vitro and in vivo bioimaging

Abstract: A significant compound in living organisms, hydrogen peroxide (H2O2) plays a dual role as a signalling molecule in cellular communication and as a pivotal biomarker in assessing disease and oxidative stress. Thus, the detection of abnormal changes in H2O2 levels is essential to understanding its function and involvement in biological systems. The growing demand to meet the specific needs for applications, particularly in biological systems, has sharpened focus on highly sensitive, highly selective molecular sensors and, in turn, heightened interest in these diagnostic tools with innovative designs. In our study, 2-aminophenalenone (2-AP) was used for the first time as a fluorophore in a fluorescent probe. The 2-APB molecule obtained from the reaction of 2-AP with 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) benzyl chloroformate exhibited a highly selective and sensitive (i.e. 62 nM) detection profile for H2O2 compared with the other reactive oxygen species, anions, and metal cations. Moreover, offering naked-eye detection in aqueous solutions, 2-APB demonstrated excellent sensing performance, detection and real-time monitoring in relation to exogenous H2O2 in cells and endogenous H2O2 in zebrafish embryos.

Lighting up Mycobacteria with membrane-targeting peptides

Abstract: We report a series of fluorescent probes based on mycobacteria membrane-associated disruption peptide, containing either L- or D-amino acids which were originally designed to kill Mycobacterium tuberculosis via membrane disruption. These peptides were decorated with “always on” and environmentally sensitive fluorophores and showed the rapid and efficient labelling of Mycobacterium smegmatis, with labelling of Mycobacterium tuberculosis demonstrated by two of the probes.

Colorimetric detection of hydrogen peroxide using nanozymes

Abstract: Nanozymes, which have established themselves as powerful alternatives to enzymes in the literature, are widely recognized today in various fields such as environmental applications, biomedical sciences, bioimaging, and point-of-care systems. Their widespread recognition in contemporary research and technological advancements was extensively discussed in the literature. Traditionally, natural enzymes have been utilized for catalytic conversions, leading to the visual or electrochemical detection of compounds through decomposition-like processes. However, this phenomenon often results in unstable detection. In contrast, nanozymes, engineered using nanomaterials, offer enhanced stability and selectivity inherent enzymatic activities and cost-effective fabrication processes. This chapter sheds light on the growing significance and broad impact of nanozymes in the specific aspect of colorimetric detection of hydrogen peroxide, having significant importance in regulating of serial biological processes as well as specific diseases’ progression.

A Phenalenone-based Fluorescent Probe for the Detection of Fe3+ ions

Abstract: A phenalenone based “turn on” probe was developed for selective and sensitive detection of Fe3+ ions in aqueous solutions. The thiophene-2-carboxaldehyde (receptor unit) was integrated into the 6-amino-1-phenalenone (6-AP) (signal reporter unit) through the C = N bond formation. The probe, 6-APT, operated through subsequent hydrolysis of the C = N bond induced by the coordination of Fe3+ ions to the heteroatoms to form highly fluorescent 6-AP. The probe displayed remarkable characteristics such as rapid response time (< 1 min), high analyte selectivity, and low limit of detection (1.3 µM). The sensing approach offered an accurate method for the detection of Fe3+ ions in real water samples (tap water and drinking water). In addition to the fluorometric response, the presence of Fe3+ ions can be monitored under daylight by the change in the color of the solution. Importantly, this study is the first example of a phenalenone-based sensor developed for metal ion sensing in literature.

A reaction-based scenario for fluorescence probing of Au (iii) ions in human cells and plants

Abstract: A BODIPY-based fluorophore decorated with a gold specific reactive handle (e.g., 2-alkynylallyl alcohol) displayed a ratiometric fluorescence change in response to Au3+ ions with extraordinary selectivity over other competing metal species, including Hg2+, Cu2+, Zn2+ and Pd2+. By way of a gold-catalyzed intramolecular cyclisation–isomerisation reaction sequence, a BODIPY construct with an extended π-conjugation transformed into a new structure with a relatively short π-system. This unique chemical transformation was accompanied by, and resulted in, a dramatic shift in the emission and absorption wavelength, which could be monitored as distinct changes in the color of the solution's emission. Apart from its outstanding analytical performance in solution, including a quick response time (<10 s), unique specificity, a high-fold ratiometric change (62-fold), and a remarkably low detection limit (358 nM), the probe also proved useful in monitoring Au3+ ions in human cells and plants (e.g., Nicotiana benthamiana).

A BODIPY based probe for the reversible "turn on" detection of Au(III) ions

Abstract: A new “turn on” fluorescent probe for the rapid and selective detection of Au3+ ions over other metal ions was developed. T he probe design was constructed on a BODIPY-2-aminopyridine skeleton showing a weak fluorescence emission signal which increased substantially after the coordination of Au3+ ions. The probe displayed remarkable sensing performances such as a low limit of detection (17 nM), a short response time (<1 min), and ability in a wide range of pH’s (6–11). The designed probe was found to have 2:1 coordination stoichiometry according to Job’s plot analysis and most importantly to interact reversibly with Au3+ ions.

Rapid detection of major Gram-positive pathogens in ocular specimens using a novel fluorescent vancomycin-based probe

Abstract: Bacterial infections of the eye are significant causes of morbidity that can lead to permanent visual loss without rapid and adequate treatment, with Gram-positive bacteria causing the majority of ocular infections. Here we report a novel probe, based on the reductive amination of vancomycin with a 4-nitrobenzoxadiazole (NBD)-based aldehyde, that rapidly and specifically detects Gram positive infections from ocular samples

Light-controlled, living radical polymerisation mediated by fluorophore-conjugated RAFT agents

Abstract: Photoinduced electron transfer-reversible addition−fragmentation chain-transfer (PET-RAFT) polymerisation allows the controlled synthesis of polymers and provides an alternative to transition metal-based photoinitiators. Here, fluorophore-conjugated RAFT agents, containing either 5-carboxyfluorescein or a “boron-dipyrromethene” (BODIPY) moiety attached to a thiocarbonylthio group, were synthesised.

Molecular detection of Gram-positive bacteria in the human lung through an optical fiber–based endoscope

Abstract: The relentless rise in antimicrobial resistance is a major societal challenge and requires, as part of its solution, a better understanding of bacterial colonization and infection. To facilitate this, we developed a highly efficient no-wash red optical molecular imaging agent that enables the rapid, selective, and specific visualization of Gram-positive bacteria through a bespoke optical fiber–based delivery/imaging endoscopic device.

BODIPY–vinyl dibromides as triplet sensitisers for photodynamic therapy and triplet–triplet annihilation upconversion

Abstract: We devised a new generation of halogen-based triplet sensitisers comprising geminal dibromides at the vinyl backbone of a BODIPY fluorophore. Incorporating geminal dibromides into the π-conjugation of BODIPY enhanced intersystem crossing due to the heavy atom effect, which in turn improved the extent of excited triplet states.

Dyeing fungi: amphotericin B based fluorescent probes for multiplexed imaging

Abstract: The clinically used antifungal polyene amphotericin B was conjugated, via the mycosamine and the aglycon moieties, to fluorophores. The Cy5 conjugated probe showed selective labelling of fungi in the presence of bacteria, allowing multiplexed imaging and identification of microbial species in a co-culture of fungi and Gram-positive and Gram-negative bacteria.

Wash‐free, peptide‐based fluorogenic probes for microbial imaging

Abstract: Peptides with pan‐antimicrobial affinity were synthesized and decorated with environmentally sensitive fluorophores nitrobenzoxadiazole (green) and merocyanine (red). The labeling efficacies against a range of clinically relevant fungal and Gram‐negative and positive bacterial species (Candida albicans, Escherichia coli, and Staphylococcus aureus) were explored.

Bioorthogonal swarming: In situ generation of dendrimer

Abstract: With the aid of bioorthogonal chemistry, we demonstrate the fabrication of synthetic dendrimers in situ around living cells. Using tetrazine dienophile and aminooxyl/hydrazide aldehyde chemistries, the density of functional groups on the dendrimers exponentially amplified intensities of fluorescent markers in antibody-targeted live cell imaging. This novel “swarming” approach highlights the power of bioorthogonal chemistry and provides a route to non-natural chemical structures on cells, paving the way for the generation of various artificial cellular nanostructures and scaffolds.

A new fluorescent ‘turn on’probe for rapid detection of biothiols

Abstract: We designed and synthesised a novel molecular probe exhibiting high selectivity and sensitivity towards reactive sulphur species (RSS) over other amino acids and biologically relevant species, as well as scrutinised its spectroscopic behaviours under physiological conditions and in living milieu.We used an electrophilic cyanate group as a masking agent to block the excited state intramolecular proton transfer process of 2-(2-cyanato-3-methoxyphenyl)benzo[d]thiazole (HMBT-OCN), which readily hydrolyses to the highly fluorescent structure, 2-(2ʹ-Hydroxy-3ʹ-methoxyphenyl)benzothiazole (HMBT-OH), in the presence of reactive sulphur species

Design of photosensitizing agents for targeted antimicrobial photodynamic therapy

Abstract: Photodynamic inactivation of microorganisms has gained substantial attention due to its unique mode of action, in which pathogens are unable to generate resistance, and due to the fact that it can be applied in a minimally invasive manner. In photodynamic therapy (PDT), a non-toxic photosensitizer (PS) is activated by a specific wavelength of light and generates highly cytotoxic reactive oxygen species (ROS) such as superoxide (O2−, type-I mechanism) or singlet oxygen (1O2*, type-II mechanism).

Time-resolved spectroscopy of fluorescence quenching in optical fibre-based pH sensors

Abstract: Numerous optodes, with fluorophores as the chemical sensing element and optical fibres for light delivery and collection, have been fabricated for minimally invasive endoscopic measurements of key physiological parameters such as pH. These flexible miniaturised optodes have typically attempted to maximize signal-to-noise through the application of high concentrations of fluorophores. We show that high-density attachment of carboxyfluorescein onto silica microspheres, the sensing elements, results in fluorescence energy transfer, manifesting as reduced fluorescence intensity and lifetime in addition to spectral changes.

Multifunctional, histidine-tagged polymers: antibody conjugation and signal amplification

Abstract: A polymer scaffold, with multiple reactive centres, was synthesised by RAFT polymerisation and conjugated to the antibody herceptin. A hexahistidine RAFT agent enabled the rapid and simple purification of polymer–protein conjugates, while the tetrazine conjugation strategy allows myriad cargos to be attached and amplified.