Core-shell Systems Research Articles

Core-shell nanoparticles based on zirconia covered with silver as an advantageous perspective for obtaining antimicrobial nanocomposites with good mechanical properties and less cytotoxicity

Antimicrobial nanoparticles perform a vast and promising strand of applications, among which, the silver ones stand out due to their broad antimicrobial spectrum. However, their toxicological potential in addition with their not always satisfying mechanical properties limit their wider application. In this sense, the use of core-shell systems can generate materials with improved properties. Thus, the goal of the present work was to obtain zirconia-silver core-shell nanoparticles and, after that, evaluate their properties in systems based on poly(lactide) PLA. Systems containing silver nanoparticles (AgNP), zirconium oxide (ZrNP), a physical mixture of both particles and core-shell nanoparticles (Core-shell NP) were evaluated. The Core-shell NP were characterized by dynamic light scattering (DLS), Energy Dispersive X-Ray (EDX), transmission electronic microscopy (TEM), and antimicrobial activity. The nanocomposite films were evaluated by Fourier transform infrared analysis (FTIR), thermogravimetric analysis (TGA), nano-hardness, tensile strength test, cytotoxicity, and antimicrobial activity. The results obtained from the DLS and EDX analyses confirmed the obtaining of systems covered with silver. Through the TEM analysis, the formation of the core-shell structure with a diameter of about 100 nm was observed. The films containing core-shell NP presented antimicrobial activity with a profile correspondent to the one observed for AgNP. As for cytotoxicity, these particles proved to be less cytotoxic and achieved higher values of hardness (10%), modulus (40%), and toughness (28%) than those observed for AgNP, and these properties were lower than those observed for ZrNP. The core-shell NP also exhibited even greater antimicrobial activities, less cytotoxicity, and largest elastic modulus (17%) than the physical mixture of the particles.

The Influence of Size, Shape, and Twin Boundaries on Heat‐Induced Alloying in Individual Au@Ag Core–Shell Nanoparticles

Environmental conditions during real-world application of bimetallic core-shell nanoparticles (NPs) often include the use of elevated temperatures, which are known to cause elemental redistribution, in turn significantly altering the properties of these nanomaterials. Therefore, a thorough understanding of such processes is of great importance. The recently developed combination of fast electron tomography with in situ heating holders is a powerful approach to investigate heat-induced processes at the single NP level, with high spatial resolution in 3D. In combination with 3D finite-difference diffusion simulations, this method can be used to disclose the influence of various NP parameters on the diffusion dynamics in Au@Ag core-shell systems. A detailed study of the influence of heating on atomic diffusion and alloying for Au@Ag NPs with varying core morphology and crystallographic details is carried out. Whereas the core shape and aspect ratio of the NPs play a minor role, twin boundaries are found to have a strong influence on the elemental diffusion.

Preparation of clarithromycin floating core-shell systems (CSS) using multi-nozzle semi-solid extrusion-based 3D printing

Matrix erosion is unavoidable during the release of poorly soluble drugs from gastric floating delivery system (GFDDS), which shortens the floating time and diminishes drug release. We fabricated a core-shell system (CSS) consisting of a low-density drug-loaded shell and a floating core using multi-nozzle semi-solid extrusion (SSE) 3D printing technology. The clarithromycin (CAM) loading capacity of the shell was 81.7%. The floating core paste provided structural support during printing and formed a hollow structure in CAM CSS, which increased the buoyancy in the early stage of drug release. In addition, the floating core had numerous micro-airbags that swelled when the solution penetrated the core, and generated CO2. The micro-airbag structure and CO2 generation further increased the buoyancy of CSS. The CAM CSS achieved 74.5% (w/w) drug loading, 8 h sustained release, and immediate and prolonged floating (>10 h). This structure of CSS and floating core provide a novel perspective for constructing a stable gastric floating drug delivery system.

Construction of Explicit Symplectic Integrators in General Relativity. IV. Kerr Black Holes

Abstract In previous papers, explicit symplectic integrators were designed for nonrotating black holes, such as a Schwarzschild black hole. However, they fail to work in the Kerr spacetime because not all variables can be separable, or not all splitting parts have analytical solutions as explicit functions of proper time. To cope with this difficulty, we introduce a time transformation function to the Hamiltonian of Kerr geometry so as to obtain a time-transformed Hamiltonian consisting of five splitting parts, whose analytical solutions are explicit functions of the new coordinate time. The chosen time transformation function can cause time steps to be adaptive, but it is mainly used to implement the desired splitting of the time-transformed Hamiltonian. In this manner, new explicit symplectic algorithms are easily available. Unlike Runge–Kutta integrators, the newly proposed algorithms exhibit good long-term behavior in the conservation of Hamiltonian quantities when appropriate fixed coordinate time steps are considered. They are better than same-order implicit and explicit mixed symplectic algorithms and extended phase-space explicit symplectic-like methods in computational efficiency. The proposed idea on the construction of explicit symplectic integrators is suitable for not only the Kerr metric but also many other relativistic problems, such as a Kerr black hole immersed in a magnetic field, a Kerr–Newman black hole with an external magnetic field, axially symmetric core–shell systems, and five-dimensional black ring metrics.

Impedance engineered microwave absorption properties of Fe-Ni/C core-shell enabled rubber composites for X-band stealth applications

• A simple, consistent, and economical wet-chemical process for synthesizing large scale Fe-Ni nanocomposites. • A BCC to FCC structural transition with varying Ni concentration in metallic core. • Fe-Ni/C alloy and rubber composites as efficient X-band microwave absorber materials. We report a simple, consistent, and economical wet-chemical method for synthesizing a series of Fe-Ni nanocomposites by varying Fe and Ni fractions. Further, graphite wrapped Fe-Ni alloy nanoparticles in core-shell geometries are prepared by calcination of nanocomposites at 900°C under N 2 gas. XRD studies reveal body-centered and face-centered (bcc/fcc) cubic Fe-Ni alloy core particles and hexagonal graphitic shell formation. More interestingly, a structural transition from bcc to fcc phase is also investigated with varying Ni concentration. The microstructural studies demonstrate ~10 nm graphitic shells together with a nearly spherical ~40 nm diameter Fe-Ni metallic core. These magnetic alloys showed the variation in magnetization and coercive fields with alloy compositions. The Fe-Ni core-shell material with the maximum magnetization is used for fabricating rubber-based composites by varying filler loading in the range 60–80 wt%. The utility of Fe-Ni/C alloy and rubber composite is categorized in terms of electromagnetic impedance matching for the entire X-band (8.2–12.4 GHz) frequency range based on the filler concentration and absorber thickness for microwave absorption applications. These core-shell alloy systems may show potential for stealth of strategic targets because of their very low density (~1.1 g/cc) and lesser thickness than conventional absorbers.

Lipoparticles for Synergistic Chemo-Photodynamic Therapy to Ovarian Carcinoma Cells: In vitro and in vivo Assessments.

PurposeLipoparticles are the core-shell type lipid-polymer hybrid systems comprising polymeric nanoparticle core enveloped by single or multiple pegylated lipid layers (shell), thereby melding the biomimetic properties of long-circulating vesicles as well as the mechanical advantages of the nanoparticles. The present study was aimed at the development of such an integrated system, combining the photodynamic and chemotherapeutic approaches for the treatment of multidrug-resistant cancers.MethodsFor this rationale, two different sized Pirarubicin (THP) loaded poly lactic-co-glycolic acid (PLGA) nanoparticles were prepared by emulsion solvent evaporation technique, whereas liposomes containing Temoporfin (mTHPC) were prepared by lipid film hydration method. Physicochemical and morphological characterizations were done using dynamic light scattering, laser doppler anemometry, atomic force microscopy, and transmission electron microscopy. The quantitative assessment of cell damage was determined using MTT and reactive oxygen species (ROS) assay. The biocompatibility of the nanoformulations was evaluated with serum stability testing, haemocompatibility as well as acute in vivo toxicity using female albino (BALB/c) mice.Results and ConclusionThe mean hydrodynamic diameter of the formulations was found between 108.80 ± 2.10 to 405.70 ± 10.00 nm with the zeta (ζ) potential ranging from −12.70 ± 1.20 to 5.90 ± 1.10 mV. Based on the physicochemical evaluations, the selected THP nanoparticles were coated with mTHPC liposomes to produce lipid-coated nanoparticles (LCNPs). A significant (p< 0.001) cytotoxicity synergism was evident in LCNPs when irradiated at 652 nm, using an LED device. No incidence of genotoxicity was observed as seen with the comet assay. The LCNPs decreased the generalized in vivo toxicity as compared to the free drugs and was evident from the serum biochemical profile, visceral body index, liver function tests as well as renal function tests. The histopathological examinations of the vital organs revealed no significant evidence of toxicity suggesting the safety and efficacy of our lipid-polymer hybrid system.

Curcumin Loaded and Co-loaded Nanosystems: A Review from a Biological Activity Enhancement Perspective.

Curcumin is a natural phenolic compound exhibiting multiple bioactivities that have been evaluated in vitro, in vivo as well as through clinical studies in humans. Some of them include antimicrobial, antioxidant, anti-inflammatory, and central nervous system protective effects. Further, curcumin is generally recognized as a safe substance because of its low toxicity. However, its molecular structure is susceptible to changes in pH, oxidation, photodegradation, low aqueous solubility, and biotransformation compromising its bioavailability; these drawbacks are successfully addressed through nanotechnology. The present review systematizes findings on the enhancement of curcumin's beneficial effects when it is loaded and co-loaded into different types of nanosystems covering liposomes, polymeric and solid-lipid nanoparticles, nanostructured lipid carrier, lipid-polymeric hybrids, self- -assembled and protein-based core-shell systems in relation to its antimicrobial, antioxidant, anti-inflammatory and central nervous system protective bioactivities. Curcumin is a versatile molecule capable of exerting antimicrobial, antioxidant, anti- inflammatory, and central nervous system protective effects in an enhanced manner using the possibilities offered by the nanotechnology-based approach. Its enhanced bioactivities are associated with increments in solubility, stability, bioavailability, as well as in improved intracellular uptake and cell internalization. These advantages, in addition to curcumin's low toxicity, indicate the potential of curcumin to be loaded and co-loaded into nanosystems capable of providing a controlled release and targeted administration.

Люминесцентные свойства коллоидных квантовых точек Ag-=SUB=-2-=/SUB=-S для фотокаталитических приложений

The structural and optical properties of colloidal Ag2S quantum dots in various environments are investigated. With the help of transmission electron microscopy, X-ray diffraction and X-ray energy dispersion analysis, the formation of colloidal Ag2S quantum dots with an average size of 2-3 nm with a monoclinic crystal lattice, and Ag2S/SiO2 core-shell systems based on them, has been established. The change in the luminescence quantum yield of quantum dots with the change of the surface environment state is shown. The decoration of TiO2 nanoparticles of 10-15 nm in size with Ag2S quantum dots was performed and the influence of the structure of the interfaces of quantum dots and their environment (2-mercaptopropionic acid, water, ethylene glycol, SiO2 dielectric shell with a thickness of 0.6 nm and 2.0 nm) on the formation of TiO2-Ag2S heterosystems was analyzed. For Ag2S quantum dots passivated with 2-mercaptopropionic acid, signs of charge phototransfer after adsorption on TiO2 nanoparticles surface have been established. Signs of reactive oxygen species appearance due to charge phototransfer in heterosystem are enstablished, based on methylene blue photobleaching under excitation of heterosystem outside of TiO2 fundamental absorption region,

Enhanced nonlinear absorption and efficient power limiting action of Au/Ag@ graphite core-shell nanostructure synthesized by laser ablation

Here we report a drastic enhancement of nonlinear absorption behaviour and exceptional optical limiting action of two core-shell systems (Au@graphite and Ag@graphite) prepared by adopting a fairly easy way in which we did not use any graphitic substrate. We carried out pulsed laser ablation of Au and Ag targets in toluene, monosubstituted benzene from which graphite layers of nanometer thickness has emerged as a result of photochemical reactions. The prepared samples were characterized and analyzed by UV/Vis spectroscopy, Raman spectroscopy, and TEM. Theoretical simulations of the core-shell nanostructures were done by the finite-difference time-domain method underlined the quenching of SPR in the case of both Au and Ag NPs by the graphitic layers evolved from toluene. Au and/or Ag@graphite core-shell structure exhibited a huge improvement in the nonlinear absorption behaviour and the optical limiting efficiency of these systems is found to be better than that of many benchmark optical limiters. The enhancement in nonlinear absorption property and the limiting actions of these systems were attributed to the enhanced excited-state absorption as well as free-carrier absorption arose as a result of the modification in the electronic structure of graphite on core-shell formation. Moreover, the metallic NPs also enhances nonlinear absorption through free-carrier absorption free-carrier absorption. So we believe these results are quite useful for guiding the characterization, monitoring the synthesis of similar nanostructures and for, the development of nanohybrids with desired properties for nonlinear optical, optoelectronic and photocatalytic applications.

Resolving the Dilemma of Nanoparticles’ Structure-Property Relationships at the Atomic Level: Case Study of Pt-Based PEM Fuel Cell Oxygen Reduction Electrocatalysts

Achieving highly active and stable oxygen reduction reaction (ORR) performance at low platinum-group-metal (PGM) loadings remains one of the grand challenges in the proton-exchange membrane fuel cells (PEMFCs) community. Currently, state-of-the-art electrocatalysts are high-surface-area-carbon-supported nanoalloys of platinum (Pt) with different transition metals M (M = Cu, Ni, Fe, Co, etc.). Nevertheless, despite years of focused research, the established structure-property relationships are not able to explain and predict the electrochemical performance and behaviour of the real nanoparticulate systems. Unlike the perfect core-shell systems, usually used to model the observed behaviour of the electrocatalysts by the community, nanoparticles in real nanocatalysts exhibit much greater local atomic-scale structural complexity. Structure-property relationships addressing averaged material properties, such as the actual ORR activity and metal degradation (e.g. dissolution) behaviour, are at risk of oversimplifying the underlying phenomena when they rely on top-down characterization techniques and attribute averaged affects to idealized nanoparticle structures. In this work, we reveal the complexity of commercially available Pt/C and Pt-M/C electrocatalysts and discuss the relevance of understanding their stability behaviour in fuel cell systems. We expose the limitations of the established top-down characterization methodologies for studying degradation and provide a conceptual approach that offers a new dimension and transcends the limits of conventional structure-stability studies. We outline a bottom-up approach where atomically resolved properties, structural changes and strain analysis are recorded as well as analysed in great detail on an individual nanoparticle. While fundamental, this approach addresses the complexity of practical electrocatalysts and enables studying their stability when exposed to realistic electrochemical conditions (i.e. high current density). This methodology, in our opinion, offers the new level of understanding structure-stability relationships of practically viable nanoparticulate systems.

Oxygen sensing performance of biodegradable electrospun nanofibers: Influence of fiber composition and core-shell geometry

The ability to continuously monitor tissue oxygenation in vivo is highly desired for a variety of biomedical applications. Implantable optical oxygen sensors can be constructed through incorporation of an oxygen-sensitive chromophore within a biocompatible polymer host. In this work, a Pd (II) benzoporphyrin that absorbs (630 nm) and phosphoresces (810 nm) within the optical tissue window was incorporated into various biodegradable polymer matrices via electrospinning. A unique in situ fluorimeter setup was constructed and used to rigorously characterize the sensor performance in the physiologically relevant dissolved oxygen range (∼0−90 μM) in 37 °C phosphate buffered saline. Single-component polycaprolactone (PCL) fibers exhibited high sensitivity (KSV: 1.25 × 105 M−1) and monoexponential decay curves, indicating a homogenous chromophore environment. The ability to move from a single-component composition (PCL) to blended (PCL:gelatin) and core-shell systems (PCL:gelatin-PCL) without compromising the desirable properties of the single-component sensor was demonstrated. These variations may offer the potential to tune degradation time of the resulting sensor while maintaining high sensitivity and monoexponential decays. In contrast, blended 50:50 PCL:poly(d,l-lactide-co-glycolide) (PLGA) exhibited significantly reduced sensitivity (KSV: 6.66 × 104 M−1) and biexponential decays. Despite the observation of biexponential lifetime decays for PCL:PLGA, all electrospun sensors exhibited linear Stern-Volmer behavior over the physiologically relevant dissolved oxygen range. This work rigorously evaluated biodegradable candidates for in vivo oxygen sensing under physiologically relevant conditions in which the character of the individual phosphorescence decay curves offered insight into the nature of the chromophore environment.

Oblique wrinkling patterns on liquid crystal polymer core–shell cylinders under thermal load

Smart soft materials, which can flexibly respond to external multi-physics stimuli, have attracted considerable attention over the past few years. Here, we present tunable wrinkling patterns in cylindrical core–shell systems under thermal load via the orientation of director in nematic liquid crystal polymer (LCP). To quantitatively analyze mechanical behavior and morphological evolution of LCP core–shell cylinders, we develop a core–shell model that accounts for director-induced anisotropic spontaneous strains. By tuning the alignment of liquid crystal director, we explore the effects of anisotropy of spontaneous strains on instability pattern formation and evolution. When the director is along the circumferential direction, wrinkling pattern can be axisymmetric or diamond-like, determined by a single dimensionless parameter Cs which characterizes the stiffness ratio and curvature of the system. When the director is parallel to the axial direction, leading to circumferential expansion upon heating, the core–shell cylinder usually buckles into churro-like mode. For general spatial director alignment, the ultimate wrinkling patterns depending on the anisotropy state of spontaneous strains, can be diamond-like, parallel bead-chain or oblique stripe mode. We draw director-affected phase diagrams to provide an overall view of pattern selection affected by liquid crystal director orientation, which could be used to quantitatively guide the effective design of wrinkling morphology-related smart surfaces.

A comparative investigation of normal and inverted exchange bias effect for magnetic fluid hyperthermia applications

Exchange bias (EB) of magnetic nanoparticles (MNPs) in the nanoscale regime has been extensively studied by researchers, which have opened up a novel approach in tuning the magnetic anisotropy properties of magnetic nanoparticles (MNPs) in prospective application of biomedical research such as magnetic hyperthermia. In this work, we report a comparative study on the effect of magnetic EB of normal and inverted core@shell (CS) nanostructures and its influence on the heating efficiency by synthesizing Antiferromagnetic (AFM) NiO (N) and Ferrimagnetic (FiM) Fe3O4 (F). The formation of CS structures for both systems is clearly authenticated by XRD and HRTEM analyses. The magnetic properties were extensively studied by Vibrating Sample Magnetometer (VSM). We reported that the inverted CS NiO@Fe3O4 (NF) MNPs have shown a greater EB owing to higher uncompensated spins at the interface of the AFM, in comparison to the normal CS Fe3O4@NiO (FN) MNPs. Both the CS systems have shown higher SAR values in comparison to the single-phased F owing to the EB coupling at the interface. However, the higher surface anisotropy of F shell with more EB field for NF enhanced the SAR value as compared to FN system. The EB coupling is hindered at higher concentrations of NF MNPs because of the enhanced dipolar interactions (agglomeration of nanoparticles). Both the CS systems reach to the hyperthermia temperature within 10 min. The cyto-compatibility analysis resulted in the excellent cell viability (> 75%) for 3 days in the presence of the synthesized NPs upto 1 mg/ml. These observations endorsed the suitability of CS nanoassemblies for magnetic fluid hyperthermia applications.

Novel combination of non-invasive morphological and solid-state characterisation of drug-loaded core-shell electrospun fibres

In recent years, core-shell nanofibrous drug delivery systems have received increasing attention due to their ability to incorporate two or more active pharmaceutical ingredients (APIs) individually into the desired layer (either core or sheath) and thereby finely tune the release profiles of even incompatible drugs in one system. This study aims to perform formulation and solid-state characterisation of levofloxacin-loaded polylactic acid (PLA) - naproxen-sodium-loaded polyvinyl pyrrolidone (PVP) bicomponent core-shell fibrous sheets and examine the electro spinnability of the precursor combinations. The selected drugs have potential therapeutic relevance in similar systems intended for wound healing; however, in this study, they are used as model drugs to understand the physicochemical properties of a drug loaded system. In order to determine the best core- and shell-solution combination, a full factorial experimental design is used. A combination of various morphological (scanning electron microscopy and transmission electron microscopy) and microstructural characterisation techniques (X-ray photoelectron spectroscopy and Raman spectroscopy) was applied to non-invasively obtain information about the structure of the fibres and the embedded drugs. The results indicate that core-shell fibres of different compositions could be successfully prepared with various structural homogeneities. The best core-shell structure was obtained using a combination of 15% (w/w) shell concentration and 8% (w/w) PLA solution concentration. In addition to the conventional core-shell structural verification methods, the Raman spectroscopy method was implemented to reveal not only the core-shell structure of the PLA/PVP nanofibers but also the form of the embedded drugs. The Raman mapping of the fibres confirm the above results, and it is shown that an amorphous solid dispersion is formed as a result of the coaxial electrospinning process.

Alginate/maltodextrin and alginate/shellac gum core-shell capsules for the encapsulation of peppermint essential oil

Encapsulation of essential oils represents a good strategy to protect and to transform them in free-flowing particles. Core-shell systems containing peppermint essential oil have been obtained by inverse ionotropic gelation. An O/W emulsion composed of essential oil (O) and aqueous CaCl2 solution enriched with hydroxyethylcellulose (W) was dripped in an alginate solution added of a secondary excipient (maltodextrin or shellac gum) at two concentrations. The qualitative/quantitative modifications of capsule shell composition had a limited impact on the essential oil content (it was more than 50% w/w), while they affected other dried capsule properties like dimensions, shell thickness, hardness and swelling behavior. Neither the type nor the amount of secondary excipient influenced wet capsule particle size (about 4 mm). After drying, particle size decreased (it was about 2 mm) and while shellac gum amount did not affect dried capsule dimensions, an increase in maltodextrin amount corresponded to an increase in their diameters. Capsule hardness diminished by increasing the amount of secondary excipient in the formulations. In addition, the amount of maltodextrin included in the formulations affected the swelling behavior of the dried capsules in water and this leads considering maltodextrin a useful excipient to modulate swelling according to the needs of the different applications.

Development of Core-Shell Nanoparticle Drug Delivery Systems Based on Biomimetic Mineralization.

Among various drug-delivery systems, core-shell nanoparticles have many advantages. Inspired by nature, biomimetic synthesis has emerged as a new strategy for making core-shell nanoparticles in recent years. Biomimetic mineralization is the process by which living organisms produce minerals based on biomolecule templating that leads to the formation of hierarchically structured organic-inorganic materials. In this minireview, we mainly focus on the synthesis of core-shell nanoparticle drug-delivery systems by biomimetic mineralization. We review various biomimetic mineralization methods for fabricating core-shell nanoparticles including silica-based, calcium-based and other nanoparticles, and their applications in drug delivery. We also summarize strategies for drug loading in the biomolecule-mineralized core-shell NPs. Current challenges and future directions are also discussed.

Atomic-scale insights into structural and thermodynamic stability of spherical Al@Ni and Ni@Al core–shell nanoparticles

Atomic-scale comprehension of structure and thermodynamic stability of metallic core–shell nanoparticles is important for viewpoints of both their synthesis and applications. Thermodynamic and structural properties of Al@Ni and Ni@Al core–shell nanoparticles are investigated at various temperatures by using molecular dynamics (MD) simulations within the interactions defined by the many-body embedded atom model (EAM). The sizes of Al@Ni core–shell nanoparticles and their pure counterparts are chosen as two different values of about 5 nm and 10 nm in this study. MD method is used to calculate the total energy, one-body particle density, radial distribution function, and heat capacity to estimate the melting temperatures of the core–shell systems considered in the present study. Our estimated melting temperatures of core–shell nanoparticles are also verified by doing common neighbor analysis (CNA). MD study shows that a distinct two-stage melting takes place during the heating of the Al@Ni core–shell nanoparticles, although their melting mechanism has started from surface into interior. It is reported that the width of the melting temperature of the core–shell nanoparticles is dependent not only on the bulk melting points of their pure metals but also on the ratio of the shell thickness and the core size of the nanoparticles.

Magnetically induced heating by iron oxide nanoparticles dispersed in liquids of different viscosities

The AC magnetically induced heating characteristics of uncoated and silica-coated magnetic iron oxide nanoparticles dispersed in liquids of different viscosities were investigated. The aim was to synthesize and prepare uncoated and silica-coated nanoparticles of maghemite, and evaluate their ability to hyperthermically dissipate heat under an applied AC magnetic field when they are dispersed in liquids of different viscosities. A conceptual approach on the relative contributions of the Néel and the Brownian relaxation mechanisms to the hyperthermic heating of these suspensions is proposed. The microstructure, the physical and chemical properties of the uncoated and silica-coated nanoparticles were assessed by transmission electron microscopy; powder X-ray diffraction; 57Fe Mössbauer spectroscopy; Fourier transform infrared spectroscopy; zeta potential measurements; and conventional chemical analysis. Results of the Rietveld refinement of the XRD patterns and analysis of the collected Mössbauer data are well consistent with maghemite as being the only iron oxide phase. The mean diameters of the uncoated nanoparticles increased from ~6 to 7 nm, to 35 and 78 nm, for added silica coating amounts varying from 1 to 6-fold, respectively. Zeta potential measurements confirmed the efficiency of the nanoparticles sol-gel coating method. When dispersed in low viscosity media (water, triethanolamine, ethylene glycol), uncoated nanoparticles efficiently release heat via both Néel and Brown relaxation mechanisms under an applied oscillating magnetic field, achieving a temperature raise of approximately 21 °C. The silica layers tend to inhibit the Brownian motion of coated particles, making heat dissipation to be preferentially governed by the Néel relaxation of the magnetization vector. This leads to modest rises in temperature of 9 °C when they are dispersed in water or in the PVC (polyvinyl chloride). SAR tests indicate that the maghemite-silica core-shell systems might be useful for advanced technologies in medical practices based on local hyperthermia, particularly in oncology.

Lipid-Coated Nanosized Drug Delivery Systems for an Effective Cancer Therapy

Currently, despite many active compounds have been introduced to the treatment, cancer remains one of the most vital causes of mortality and reduced quality of life. Conventional cancer treatments may have undesirable consequences due to the continuous differentiating, dynamic and heterogeneous nature of cancer. Recent advances in the field of cancer treatment have promoted the development of several novel nanoformulations. Among them, the lipid coated nanosized drug delivery systems have gained an increasing attention by the researchers in this field owing to the attractive properties such as high stability and biocompatibility, prolonged circulation time, high drug loading capacity and superior in vivo efficacy. They possess the advantages of both the liposomes and polymeric nanoparticles which makes them a chosen one in the field of drug delivery and targeting. Core-shell type lipid-coated nanoparticle systems, which provide the most prominent advantages of both liposomes such as biocompatibility and polymeric/inorganic nanoparticles such as mechanic properties, offer a new approach to cancer treatment. This review discusses design and production procedures used to prepare lipid-coated nanoparticle drug delivery systems, their advantages and multifunctional role in cancer therapy and diagnosis, as well as the applications they have been used in.

Thermo-Magnetic Properties of Fe₃O₄@Poly(N-Isopropylacrylamide) Core-Shell Nanoparticles and Their Cytotoxic Effects on HeLa and MDA-MB-231 Cell Lines.

In this study, we performed a systematic evaluation of the synthesis parameters of a multiresponsive core-shell nanoplatform (Fe₃O₄ nanoparticles coated by poly(N-isopropylacrylamide). These nanocomposites allow the possibility of controlling specific properties, such as particle size and morphology. The polymer coating was performed by in-situ free-radical polymerization of N-isopropylacrylamide on Fe₃O₄ nanoparticles to obtain a nanocomposite with a core-shell structure. We monitored the size and morphology of the nanocomposite by scanning transmission electron microscopy. Electrophoretic mobility determined the evolution of ζ-potentials during coating. We assessed the functionalization of the Fe₃O₄ nanoparticles by Fourier-transform infrared spectroscopy and ultraviolet-visible spectroscopy. The core-shell systems exhibited a collapsed structure when heated above the lower critical solution temperature, which was determined by dynamic light scattering. Squid based vibrating sample magnetometer tests were performed to verify superparamagnetic behavior at room temperature. The platform was approved as biocompatible for the HeLa and MDA-MB-231 cell lines by MTT assays, and it shows the desired properties for potential use in localized and controlled drug delivery.