Pazhani Durgadevi

Förster Resonance Energy Transfer (FRET) microscopy has evolved from a specialized biophysical assay into a versatile platform for investigating molecular interactions and dynamics at the nanometer scale. FRET exploits nonradiative energy transfer between donor and acceptor fluorophores to enable real-time detection of protein–protein interactions, conformational dynamics, and enzymatic activity—all of which lie at the heart of the molecular basis of disease. These capacities bring valuable insights into molecular mechanisms involved in disease pathogenesis. This review discusses the clinical diagnostic possibilities that FRET microscopy holds in oncology and infectious diseases concerning nucleic acid and antigen detection. We detail the main technological aspects of key advances, such as cutting-edge biosensors, ratiometric imaging, and fluorescence lifetime imaging microscopy (FLIM-FRET). The persistent clinical translation challenges posed by photobleaching, spectral overlap, sample heterogeneity, and instrumentation cost are critically discussed alongside promising future solutions such as near-infrared fluorophore pairs and multiplex FRET assays. In conclusion, FRET microscopy is a mature technique, but its clinical diagnostic application remains emerging and largely confined to research and preclinical settings. Still, its unique ability to report molecular-scale events directly in situ makes it an attractive addition to the diagnostic toolbox for early disease detection, particularly where conventional approaches lack sufficient sensitivity.

Background/objectives: Delayed wound healing, along with excessive scar formation, is the major clinical drawback due to the presence of stubborn bacteria, oxidative stress, prolonged inflammation, and irregular tissue regeneration. Utilizing nanomaterial-based wound dressings offers significant advancements and minimal cytotoxicity, but also presents issues such as poor biocompatibility, low solubility, and reduced permeability. These factors limit the effectiveness of nanomaterial-based wound dressings in promoting complete tissue regeneration. To overcome these limitations, plant-derived bioactives are integrated with nanomaterials within a hydrogel cage to enhance antibacterial activity, mitigate oxidative stress and inflammation, and promote tissue regeneration. Methods: A multifunctional alginate–gelatin hydrogel incorporating silver nanoparticles and plant extracts (AG-AgNP-PE) was developed to promote scar-free wound healing, alongside a plant extract-free silver nanoparticles-loaded hydrogel for comparative evaluation of the functional contribution of plant bioactives. The biological performance of the formulated hydrogels was systematically evaluated through antioxidant, antimicrobial, and antibiofilm assays, while in vitro cytocompatibility and proregenerative activity were assessed using MTT and Alamar Blue assays, live/dead cell imaging, and a scratch-wound assay, complemented by in vivo evaluation in zebrafish embryos. Results: Pro-angiogenic activity was further investigated using the CAM model, and therapeutic efficacy was validated in an in vivo rat burn wound model through microscopic wound assessment, histopathological examination, and biochemical assays. Conclusions: Among the hydrogels, AG-AgNP-PE exhibited superior performance across all key properties, highlighting the synergistic effect of the nanomaterial combined with plant extracts within hydrogel cages and positioning it as a promising multifunctional wound dressing for rapid tissue regeneration and scar-free wound healing, suitable for advanced wound management.

All forms of neural communications, from cognition to emotion, are regulated by neurotransmitters, which are otherwise the chemical language of the brain. Precise detection of these neurotransmitters is essential for the perception of neurophysiology and diagnosis of neurodegenerative diseases as well. Among the existing techniques for the detection of these molecules, fluorescence sensing is evolving as a powerful approach in terms of high sensitivity, rapid response, and real-time visualization of the chemical events occurring in the neural system. In recent years, nanomaterials have transformed this field by integrating tunable optical properties, excellent photostability, and modifiable surface chemistry into biocompatible nanostructures. We summarize the recent advances of these architectures to show how the material type and dimensionality, as well as the surface functionality, play roles in sensing through the mechanisms of Förster resonance energy transfer (FRET), photoinduced electron transfer (PET), inner filter effect (IFE), and aggregation-induced emission (AIE). The discussion has also been extended to the correlation of fluorescence modulation with the selectivity and sensitivity in the mechanism-to-function relationship. The potential utility of such innovative technologies, including artificial intelligence, spectral deconvolution analysis via big data algorithms, and chip-integrated sensing, was explored as a means to enable real-time neurochemical detection. This converging area of nanotechnology and neuroscience leaves a mark not just in analytical accuracy, but also parallels human brain rhythms.

Background and purpose: Cancer is one of the leading causes of death worldwide, failing to identify a complete cure. Liver cancer is the sixth most frequent cancer worldwide, and its cure is still not assured. Nanoparticles, especially the metal oxide nanoparticles, have been explored as anticancer agents in recent times. In an attempt to make the best use of waste, plantain peel, a byproduct of agriculture, was used to synthesize copper oxide nanoparticles. Experimental approach: The plantain peel extract was evaluated for its chemical compo­sition by GC-MS analysis, which revealed a predominant presence of tetratetracontane. The copper oxide nanoparticles were characterized by UV-visible spectrophotometry, dynamic light scattering, zeta poten­tial, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX). Bio-inertness was assessed using an MTT assay of fibroblasts, a haemolysis assay, and zebrafish embryo analysis. The anticancer activity against HepG2 cells was estimated. Key results: The absorption peak was found at 402 nm, the hydrodynamic diameter was 323 nm, the zeta potential was +10.74 mV, and a band gap of 1.3 eV. The SEM images showed a size range of 54 to 85 nm with a chrysanthemum-petal-like morphology. EDAX showed the presence of Cu and O, and the XRD and FTIR peaks corroborated with that of CuO. The result showed that up to a dose of 50 μg mL-1, the nanoparticles did not induce any toxicity. Finally, the anticancer activity, evaluated using the HepG2 cell line, showed a dose-dependent cytotoxic effect with an IC50 of 26.20 μg mL-1. Conclusion: The outcome of this study suggested that the synthesized copper oxide nanoparticles can be used at controlled doses to kill cancer cells. Further studies are needed using other cancer cell lines and in vivo cancer models.

Magnetoliposomes are hybrid nanostructures that integrate superparamagnetic ultrasmall carbon-coated ferrite nanodots (MNCDs) within liposomes (Lipo) composed of egg yolk-derived phospholipids and stabilized with an environmentally benign potato peel extract (PPE), enabling enhanced magnetic resonance imaging (MRI) and optical imaging. The hydrothermally synthesized MNCDs were entrapped in liposomes prepared by thin-film hydration, and physicochemical properties were established at each stage of engineering. These magnetoresponsive vesicles (MNCDs+Lipo@PPE) serve as a triple-mode medical imaging contrast for T1 & T2-weighted MRI, while simultaneously enabling optical tracking of liposome degradation under an external magnetic field. They exhibited long-term enhanced fluorescence intensity and colloidal stability over 30 days, with hydrodynamic diameters ranging from 190 to 331 nm and an improved surface charge following PPE coating. In vitro cytotoxicity assays (MTT and Live/Dead staining) demonstrated over 87% cell viability for MNCDs+Lipo@PPE up to 2.7 mM concentration in A549 cells, indicating considerable toxicity. This multimodality engineering facilitates precise image-guided anticancer doxorubicin delivery and magnetic-responsive controlled release. The theoretical model shows that the release profile follows the Korsmeyer-Peppas profile. The externally applied magnetic field enhances the release by 1.4-fold. To demonstrate the anticancer efficiency in vitro with minimum off-target cytotoxicity, MTT and live/dead cell assay were performed against A549 cells. The reported study is a validated demonstration of magnetic-responsive nanocarrier systems for anticancer therapy and multimodal MRI and optical imaging-based diagnosis.

Background and purpose: Multifunctional nanoparticles (NPs) are gaining significant interest in biomedical research because of their versatility and potential across various applications, especially in cancer imaging and therapy. These composite systems consist of assorted materials, such as metallic elements, metal oxides, polymers, and carbon-based nanostructures, that are combined to form a single platform featuring improved and synergistic properties. Experimental approach: This study aims to design and synthesize a novel class of silver-coated carbon dot-capped manganese ferrite NPs that were functionalized with lipids (L-Ag@MnFe@C) to improve their cytocompatibility and enable cancer therapy with multimodal imaging functionalities. Carbon-capped manganese ferrite NPs (MnFe@C) were synthesized by a one-pot hydrothermal method, followed by the fabrication of nano-silver coated over the surface (Ag@MnFe@C) using a modified Tollens method, and lipid functionalization was done by the rotary evaporation method for the development of low-cost and biodegradable theranostic agents. Key results: The physicochemical characterization reveals that the engineered L-Ag@MnFe@C exhibits a higher stability, with a zeta potential of -50.6 mV, a hydrodynamic diameter of 279.4 nm and a quantum yield of 69.4 %. The engineered NPs exhibit contrast capabilities in longitudinal magnetic resonance imaging, transverse magnetic resonance imaging, fluorescence imaging, and computed tomography imaging. Furthermore, L-Ag@MnFe@C demonstrated excellent anticancer activity on the lung cancer cell line (A549). Conclusion: Based on these studies, it can be concluded that the engineered L-Ag@MnFe@C exhibits multimodal imaging abilities and demonstrates anticancer properties, thereby confirming it as a potential theranostic agent.

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of hope in the fight against MDR microorganisms. Among the natural photosensitizers, hypocrellins (A and B) have shown remarkable potential with their dual-mode photodynamic action, generating ROS via both Type I (electron transfer) and Type II (singlet oxygen) pathways. This unique action disrupts bacterial biofilms and inactivates MDR pathogens. The amphiphilic nature of hypocrellins further enhances their promise, enabling deep biofilm penetration and ensuring potent antibacterial effects even in hypoxic environments, surpassing the capabilities of synthetic photosensitizers. This study critically examines the antimicrobial properties of hypocrellin-based PDT, emphasizing its mechanisms, advantages over traditional antibiotics, and effectiveness against MDR pathogens. Comparative analysis with other photosensitizers, the role of nanotechnology-enhanced delivery systems, and future clinical applications are explored. Its combination with nanotechnology enhances therapeutic outcomes, providing a viable alternative to conventional antibiotics. Further clinical research is essential to optimize its application and integration into antimicrobial treatment protocols.

Background and purpose: Despite significant advancements in cancer therapies, chemotherapeutics continue to be the mainstay for treating cancer patients, with 5-fluorouracil (5-FU) being commonly used for various cancers. However, its limited ability to penetrate cell membranes and its short half-life, caused by rapid metabolism, necessitate frequent administration of high doses to maintain effective therapeutic levels. This study aimed to synthesize oxidized sodium alginate (OSA) derivatives to create OSA nanoparticles loaded with 5-FU (OSANP@ 5-FU), promoting diketo tautomers, and evaluate their photophysical properties, release profile, and anticancer activity with minimal toxicity. Experimental approach: The investigation encompassed physicochemical characterization, encapsulation efficiency, 5-FU release kinetics at pH 2.2 and 7.4, cell viability assessment via MTT assay in V79 cells, and in vitro anticancer efficacy in the A375 cell line. Key results: Steady-state absorption and emission confirmed the presence of advantageous diketone tautomers of 5-FU, indicating radiative transitions from the second singlet excited state to the ground state (S2S0) and the drug's encapsulation within the polymeric nanostructure. Dynamic light scattering revealed that OSA nanoparticles, initially 177.8 nm, grew to 226.6 nm after encapsulating 5-FU, retaining high zeta potential for stability. With a 68% encapsulation efficiency, in vitro studies showed 46 to 54 % of 5-FU released across different pH levels within 510 minutes. Conclusion: In acidic conditions, there is a greater release of 5-FU than neutral pH levels, indicating a pH-responsive release profile beneficial for cancer treatment, with the release mechanism of OSANPs following Fickian diffusion as identified by a Korsmeyer-Peppas mathematical model and the formu¬lation showing improved therapeutic efficacy.

Background: Superparamagnetic properties and excitation independence have been incorporated into carbon-decorated manganese ferrite nanodots (MnFe@C) to introduce an economical and safer multimodal agent for use in both T1-T2 MRI and fluorescence-based imaging to replace the conventional highly toxic heavy metal contrast agents. Methods: The surface conjugation of 8-anilino-1-naphthalenesulfonate (ANS) to MnFe@C nanodots (ANS-MnFe@C) enhances both longitudinal and transverse MRI relaxation, improves fluorescence for optical imaging, and increases protein detection sensitivity, showing higher multimodal efficacy in terms of molar relaxivity, radiant efficiencies, and fluorescence sensitivity compared to MnFe@C. Results: The band gap energy was determined using Tauc’s equation to be 3.32 eV, while a 72% quantum yield demonstrated that ANS-MnFe@C was highly fluorescent, with the linear range and association constant calculated using the Stern–Volmer relation. The synthesized ANS-MnFe@C demonstrated excellent selectivity and sensitivity for bovine serum albumin (BSA), with a nanomolar detection limit of 367.09 nM and a broad linear range from 0.015 to 0.225 mM. Conclusions: In conclusion, ANS-MnFe@C holds ease of fabrication, good biocompatibility, as assessed in A375 cells, and an effective pH-sensitive doxorubicin release profile to establish anticancer activity in lung cancer cell line (A549), highlighting its potential as an affordable therapeutic agent for multimodal imaging, drug delivery, and protein sensing.