Niroj Kumar Sahu

Combining durable colloidal stability with strong magnetic heating in a single aqueous ferrofluid (FF) is a long-standing obstacle in biomedical hyperthermia, because the coating that disperses the nanoparticles typically weakens their magnetic response. Aqueous magnetite FFs must therefore satisfy three requirements that are mediated by one nanoparticle surface and are consequently difficult to reconcile such as durable colloidal stability, retention of the magnetic response and efficient field-driven heating. Here, magnetite (Fe ₃ O ₄ ) nanoparticles were synthesized by alkaline co-precipitation and capped in situ with N,N-Dimethyl dodecyl amine N-Oxide (DDAO), an inexpensive zwitterionic amine-oxide surfactant. X-ray diffraction and HRTEM confirm a phase-pure, monocrystalline core of approximately 10.43 nm (particle size). FTIR and XPS verify the presence of DDAO and support coordination anchored through its N + − O − head-group oxygen to surface iron. The functionalized particles show markedly improved hydrophilicity and colloidal stabilization, with the water contact angle decreasing from 30.2° for the uncoated reference to 16.6° for DDAO–Fe ₃ O ₄ and the zeta potential becoming strongly negative at approximately −56.5 mV. The DDAO FF remains visually stable in water for one year, whereas the uncoated reference rapidly sediments. Although the non-magnetic organic shell and surface-spin perturbation moderately reduce the saturation magnetization from 63.62 to 53.81 emu g ⁻¹ , superparamagnetic behaviour is retained. DDAO–Fe ₃ O ₄ exhibits a higher SAR than the uncoated reference at every concentration, reaching 222.5 W g ⁻¹ at 0.5 mg ml ⁻¹ , about 40% above the reference at 443 Oe and 313 kHz. With closely matched magnetic cores, the heating enhancement is attributed primarily to improved dispersion, reduced aggregation-driven dipolar coupling and retention of active Néel and Brownian relaxation channels. MTT assays showed IC ₅₀ = 68.52 µ g ml ⁻¹ in HeLa cells, while L929 cells retained 79% viability at 100 µ g ml ⁻¹ , indicating comparatively lower normal-cell cytotoxicity. This work demonstrates that a single amine-oxide surfactant can integrate surface hydrophilicity, year-long aqueous stability and enhanced magnetic heating from one interfacial coordination in one practical FF formulation.

Developing stable water-based ferrofluids with efficient magnetic heating remains a key challenge for biomedical hyperthermia. In this work, we functionalize Fe ₃ O ₄ nanoparticles with surfactants of different chemical nature namely ethylenediaminetetraacetic acid (EDTA), ethanolamine and betaine and examine the role of surface chemistry on colloidal stability and heating performance in aqueous media. High-resolution transmission electron microscopy study on these samples reveals particle sizes of ∼10–12 nm, indicating monocrystalline nanoparticles with a surface coating. We confirm the successful functionalization with different functional groups such as carboxylate, amine and zwitterionic groups by Fourier transform infrared spectroscopy, thermogravimetric analysis and x-ray photoelectron spectroscopy analysis. Zeta-potential values ranging from −18.56 to −45.2 mV indicate negatively charged nanoparticle surfaces, mainly arising from Fe–O ⁻ groups and surfactant-derived functionalities that promote electrostatic stabilization in water. Vibrating sample magnetometer measurements confirm superparamagnetic behaviour with saturation magnetization of 55–63 emu g ⁻¹ indicating that the magnetic core structure is preserved. Among the studied systems, EDTA-functionalized Fe ₃ O ₄ exhibits exceptional long-term stability, retaining its ferrofluid state without sedimentation for over one year. This stable dispersion correlates with superior magnetic heating performance, achieving the highest specific absorption rate (∼245 W g ⁻¹ at 0.5 mg ml ⁻¹ ). These results demonstrate that surface functionalization plays a critical role in stabilizing aqueous ferrofluids, enhance hyperthermia efficiency and provide a practical basis for designing biocompatible magnetic nanofluids.

Triple-negative breast cancer (TNBC) remains a therapeutic challenge owing to the lack of molecular targets and high recurrence rates. Here, we report a multifunctional magneto-photothermal nanoplatform (FPG), engineered from a magnetic Fe₃O₄ core, a near infrared (NIR)-active polyaniline shell, and fluorescent graphene quantum dots for image-guided combined hyperthermia. FPG demonstrated superior colloidal stability, retained superparamagnetism, and exhibited strong NIR absorption. Upon exposure to an alternating magnetic field (AMF) and 808 nm laser irradiation, FPG consistently raised suspension temperatures within the therapeutic hyperthermia range under in vitro conditions. The nanoplatform induced concentration-dependent cytotoxicity in MDA-MB-231 cells, with significantly enhanced tumor suppression observed under combined AMF and NIR exposure compared to single modality. In vivo, image-guided combined-mode therapy resulted in significant tumor regression with minimal systemic toxicity, as evidenced by histopathology and serum biochemistry. To demonstrate translational feasibility, an integrated AMF-NIR prototype system was developed, enabling synchronized magnetic and optical heating with thermal feedback control. This work highlights how rational interface engineering of multifunctional biomaterials can be leveraged for image-guided hyperthermia and translational cancer therapy.

We report a rapid and sustainable electrochemical method for producing graphene quantum dots (GQDs) from defect-rich graphene sheets using vitamin C as a redox-buffered exfoliant and sodium hydroxide to control the ionic environment. The resulting GQDs (3–10 nm) exhibit excitation-dependent green fluorescence, high aqueous dispersibility (ζ = −28.3 mV), and moderate oxidation with abundant oxygen functionalities. In vitro studies reveal selective cytotoxicity against triple-negative breast cancer (TNBC) cells via intracellular ROS generation, while sparing normal fibroblasts. In vivo fluorescence imaging in 4T1 tumor-bearing BALB/c mice confirms preferential tumor accumulation, renal clearance, and systemic biocompatibility, supported by blood biochemistry and histopathology. Compared with conventional GQD synthesis, this strategy offers faster reaction time, reduced chemical hazards, and improved therapeutic relevance. Overall, our approach introduces a clinically translatable, green nanoplatform for image-guided and ROS-amplified nanotheranostics in TNBC.

This work presents, for the first time, a Physics Informed Neural Network (PINN) model for magnetic hyperthermia, a promising non-invasive cancer therapy known for its high efficacy and minimal side effects. Effective cancer cell destruction requires heating to 42-45 °C. The heat generated by magnetic nanoparticles (MNP) under an alternating magnetic field depends strongly on their physicochemical properties. Hence, the optimization of MNP for effective heat generation remains a key challenge and constitutes the fundamental motivation of this study. In this work, we study and compare various approaches employing regression models, Artificial Neural Network (ANN), and PINN to address the challenges associated with magnetic fluid hyperthermia (MFH) prediction and analysis. The model incorporates input parameters, including particle size, saturation magnetization, magnetic field intensity, frequency, specific heat of fluid, nanoparticle concentration, and time, to predict temperature evolution as the output. The dataset is compiled from our published research work, comprising 3,690 data points, ensuring sufficient variability and robustness for model training and evaluation. Our PINN model shows an excellent R² value of around 0.98 against the test data.

We analyzed the thermal, structural, and dynamic properties of maghemite using classical molecular dynamics, focusing on bulk and nanoparticle systems. We explored their behavior when heated to high temperatures (above the melting point) and during cooling, as well as under thermal cycles ending at intermediate temperatures. Our findings show that in the bulk system, both the tetrahedral and octahedral iron sub-lattices undergo a phase transition prior to melting. Cooling the system from above this transition, or from above the melting point, leads to the formation of different metastable maghemite structures. In contrast, this sub-lattice transition is absent in nanoparticles, where melting occurs through an interface-mediated process. At temperatures just above the transition, nanoparticles adopt an ellipsoidal shape, which is retained during cooling. In addition, the specific heat of both bulk and nanoparticle systems at temperatures above the Debye temperature is evaluated and compared with the available experimental data. Overall, our results highlight the complex thermal behavior of maghemite across a range of temperatures, which remains insufficiently explored experimentally. Further experimental investigations could also provide valuable feedback for model refinements.

Graphene quantum dots (GQDs) are a newly developed class of material, known as zero-dimensional nanomaterials, with characteristics derived from both carbon dots (CDs) and graphene. GQDs exhibit several ideal properties, including the potential to absorb incident energy, high water solubility, tunable photoluminescence, good stability, high drug-loading capacity, and notable biocompatibility, which make them powerful tools for various applications in the field of biomedicine. Additionally, GQDs can be incorporated with additional materials to develop nanocomposites with exceptional qualities and enriched functionalities. Inspired by the intriguing scientific discoveries and substantial contributions of GQDs to the field of biomedicine, we present a broad overview of recent advancements in GQDs-based nanocomposites for biomedical applications. The review first outlines the latest synthesis and classification of GQDs nanocomposite and enables their use in advanced composite materials for biomedicine. Furthermore, the systematic study of the biomedical applications for GQDs-based nanocomposites of drug delivery, biosensing, photothermal, photodynamic and combination therapies are emphasized. Finally, possibilities, challenges, and paths are highlighted to encourage additional research, which will lead to new therapeutics and global healthcare improvements.