Nanoparticle Fraught Liposomes: A Platform for Increased Antibiotic Selectivity in Multidrug Resistant Bacteria

Increasing antibiotic concentrations within bacterial cells while reducing them in mammalian ones would ultimately result in an enhancement of antibacterial actions, overcoming multidrug resistance, all while minimizing toxicity. Nanoparticles (NPs) have been used in numerous occasions to overcome antibiotic resistance, poor drug solubility, and stability. However, the concomitant increase in antibiotic concentration in mammalian cells and the resultant toxicity are usually overlooked. Without compromising bacterial cell fusion, large liposomes (Lip) have been reported to show reduced uptake in mammalian cells. Therefore, in this work, small NP fraught liposomes (NP-Lip) were formulated with the aim of increasing NP uptake and antibiotic delivery in bacterial cells but not in mammalian ones. Small polylactic-co-glycolic acid NPs were therefore loaded with erythromycin (Er), an antibiotic with low membrane permeability that is susceptible to drug efflux, and 3c, a 5-cyanothiazolyl urea derivative with low solubility and stability. In vitro experiments demonstrated that the incorporation of small NPs into large Lip resulted in a reduction in NP uptake by HEK293 cells while increasing it in Gram-negative bacteria (Escherichia coli DH5α, E. coli K12, and Pseudomonas aeruginosa), consequently resulting in an enhancement of antibiotic selectivity by fourfold toward E. coli (both strains) and eightfold toward P. aeruginosa. Ocular administration of NP-Lip in a P. aeruginosa keratitis mouse model demonstrated the ability of Er/3c-loaded NP-Lip to result in a complete recovery. More importantly, in comparison to NPs, the ocular administration of NP-Lip showed a reduction in TNF-alpha and IL-6 levels, implying reduced interaction with mammalian cells in vivo. This work therefore clearly demonstrated how tailoring the nano-bio interaction could result in selective drug delivery and a reduction in toxicity.

Alendronate-Anionic Clay Nanohybrid for Enhanced Osteogenic Proliferation and Differentiation

BACKGROUND

Alendronate (AL), a drug for inhibiting osteoclast-mediated bone-resorption, was intercalated into an inorganic drug delivery nanovehicle, layered double hydroxide (LDH), to form a new nanohybrid, AL-LDH, with 1:1 heterostructure along the crystallographic C-axis. Based on the intercalation reaction strategy, the present AL-LDH drug delivery system (DDS) was realized with an enhanced drug efficacy of AL, which was confirmed by the improved proliferation and osteogenic differentiation of osteoblast-like cells (MG63).

METHODS

The AL-LDH nanohybrid was synthesized by conventional ion-exchange reaction and characterized by powder X-ray diffraction (PXRD), high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared (FT-IR) spectroscopy. Additionally, in vitro efficacy tests, such as cell proliferation and alkaline phosphatase (ALP) activity, were analyzed.

RESULTS

The AL was successfully intercalated into LDH via ion-exchange reaction, and thus prepared AL-LDH DDS was X-ray single phasic and chemically well defined. The accumulated AL content in MG63 cells treated with the AL-LDH DDS nanoparticles was determined to be 10.6-fold higher than that within those treated with the intact AL after incubation for 1 hour, suggesting that intercellular permeation of AL was facilitated thanks to the hybridization with drug delivery vehicle, LDH. Furthermore, both in vitro proliferation level and ALP activity of MG63 treated with the present hybrid drug, AL-LDH, were found to be much more enhanced than those treated with the intact AL. This is surely due to the fact that LDH could deliver AL drug very efficiently, although LDH itself does not show any effect on proliferation and osteogenic differentiation of MG63 cells.

CONCLUSION

The present AL-LDH could be considered as a promising DDS for improving efficacy of AL.

Reversible and irreversible aggregation of magnetic liposomes

Understanding stabilization and aggregation in magnetic nanoparticle systems is crucial to optimizing the functionality of these systems in real physiological applications. Here we address this problem for a specific, yet representative, system. We present an experimental and analytical study on the aggregation of superparamagnetic liposomes in suspension in the presence of a controllable external magnetic field. We study the aggregation kinetics and report an intermediate time power law evolution and a long time stationary value for the average aggregate diffusion coefficient, both depending on the magnetic field intensity. We then show that the long time aggregate structure is fractal with a fractal dimension that decreases upon increasing the magnetic field intensity. By scaling arguments we also establish an analytical relation between the aggregate fractal dimension and the power law exponent controlling the aggregation kinetics. This relation is indeed independent on the magnetic field intensity. Despite the superparamagnetic character of our particles, we further prove the existence of a population of surviving aggregates able to maintain their integrity after switching off the external magnetic field. Finally, we suggest a schematic interaction scenario to rationalize the observed coexistence between reversible and irreversible aggregation.

Synthesis and evaluation of alendronate-modified gelatin biopolymer as a novel osteotropic nanocarrier for gene therapy

AIM

To synthesize an osteotropic alendronate functionalized gelatin (ALN-gelatin) biopolymer for nanoparticle preparation and targeted delivery of DNA to osteoblasts for gene therapy applications.

MATERIALS & METHODS

Alendronate coupling to gelatin was confirmed using Fourier transform IR, (31)PNMR, x-ray diffraction (XRD) and differential scanning calorimetry. ALN-gelatin biopolymers prepared at various alendronate/gelatin ratios were utilized to prepare nanoparticles and were optimized in combination with DNA and gemini surfactant for transfecting both HEK-293 and MG-63 cell lines.

RESULTS

Gelatin functionalization was confirmed using the above methods. Uniform nanoparticles were obtained from a nanoprecipitation technique. ALN-gelatin/gemini/DNA complexes exhibited higher transfection efficiency in MG-63 osteosarcoma cell line compared with the positive control.

CONCLUSION

ALN-gelatin is a promising biopolymer for bone targeting of either small molecules or gene therapy applications.

Inhibition of Osteoclast Differentiation and Bone Resorption by Bisphosphonate-conjugated Gold Nanoparticles

In recent years, gold nanoparticles (GNPs) have been reported to affect the regeneration of bone tissue. The goal of this study was to improve bone tissue regeneration by using targeted GNPs. We fabricated a functionalized GNPs conjugated with alendronate (ALD), of the bisphosphonate group. Subsequently, the ALD, GNPs, and ALD conjugated GNPs (GNPs-ALD) were analyzed by ultraviolet-visible absorbance (UV-vis) spectrophotometer, Attenuated total reflectance Fourier transform infrared spectrometer (ATR-FTIR), and thermo gravimetric analysis (TGA). The prepared GNPs-ALD were used to investigate their inhibitory effects on the receptor activator of nuclear factor- κb ligand (RANKL)-induced osteoclastogenesis in bone marrow-derived macrophages (BMMs). Additionally, the GNPs-ALD were applied to ovariectomy (OVX)-induced osteoporotic mice and the experiments were evaluated. ALD was found to be successfully conjugated to the GNPs surface, and it displayed significant adhesion onto the bone surface. The in-vitro study indicated that the GNPs, ALD and GNPs-ALD suppressed osteoclast formation in a dose-dependent manner. Furthermore, in the OVX mouse model, the mice treated GNPs-ALD had higher bone density as compared to other OVX mice groups. The results from these tests indicated that GNPs-ALD can be useful agents for preventing and treating osteoporosis.

Nanoparticles functionalized with supramolecular host-guest systems for nanomedicine and healthcare

Synthetic macrocyclic host compounds can interact with suitable guest molecules via noncovalent interactions to form functional supramolecular systems. With the synergistic integration of the response of molecules and the unique properties at the nanoscale, nanoparticles functionalized with the host-guest supramolecular systems have shown great potentials for a broad range of applications in the fields of nanoscience and nanotechnology. In this review article, we focus on the applications of the nanoparticles functionalized with supramolecular host-guest systems in nanomedicine and healthcare, including therapeutic delivery, imaging, sensing and removal of harmful substances. A large number of examples are included to elucidate the working mechanisms, advantages, limitations and future developments of the nanoparticle-supramolecule systems in these applications.

Self-assembly and cytotoxicity study of PEG-modified ursolic acid liposomes

While ursolic acid (UA), one of the most broadly known triterpene compounds, has proved to be effective in cancer therapy, the applications of UA is limited due to its poor aqueous solubility and low bioavailability. The aim of our study was to prolong circulation time and enhance uptake of liposomes in tumor tissues through the modification of UA liposomes via water-soluble polyethylene glycol (PEG). In addition, this research also focuses on physicochemical properties of the liposome formulations, including encapsulation efficiency, particle morphology, size, stability, release rate in vitro and cytotoxicity test. The obtained liposomes were spherical particles with mean particle diameters around 100-200 nm. And the Fourier transform infrared spectroscopy (FTIR) indicated that PEG had been anchored successfully to the liposomes. Based on our experimental data achieved, PEG-modified UA liposomes possessed higher stability than conventional liposomes, and the release rate of UA from PEG-modified liposomes was slower when compared with those of UA solution and conventional liposomes. Meanwhile, the liposomal UA showed relatively low cytotoxic effect than UA conventional liposomes within 24h, which was consistent with their release rates.

Design, Properties, and In Vivo Behavior of Super-paramagnetic Persistent Luminescence Nanohybrids

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium-doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.

Magnetic nano-organocatalysts: impact of surface functionalization on catalytic activity

Nano-organocatalysts were synthesized using controlled click chemistry and studied in aldolization and Michael addition reactions. It was shown that small modifications of the nanosurface can have a drastic effect on the catalysis.

Easily controlled grafting of oligonucleotides on γFe2O3 nanoparticles: physicochemical characterization of DNA organization and biological activity studies

We report a one-step process to functionalize superparamagnetic iron oxide nanoparticle (SPIO-NP) surfaces with a controlled number of oligonucleotides. For this study, we use a specific oligonucleotide targeting the signal transducer and activator of transcription 3 (STAT3), a key regulator of cell survival and proliferation. This oligonucleotide is self-complementary and can adopt a hairpin structure. It is labeled with the fluorescein amidite group at the 3'-end. The polyanionic DNA is electrostatically attracted onto the positively charged surface of the bare SPIO-NPs. During synthesis, the molar ratio between the oligonucleotides and nanoparticles was varied from 17.5 to 175. For particles with a mean diameter of 10 nm, a nanoparticle surface saturation is observed corresponding to 70 DNA strands per particle. The increase of DNA density per nanoparticle is correlated to a transition from the hairpin structure adsorbed horizontally on the nanoparticle surface to a vertically ordered surface packing assembly. An in vitro study on human colon carcinoma cell line SW480 shows that the kinetics of internalization and biological activity of the NPs seem to be dependent on the oligonucleotide density. Cell death and the kinetics of internalization are favored by a low density of oligonucleotides.

Low-dose chemotherapy of hepatocellular carcinoma through triggered-release from bilayer-decorated magnetoliposomes

Low-dose (LD) chemotherapy is a promising treatment strategy that may be improved by controlled delivery. Polyethylene glycol-stabilized bilayer-decorated magnetoliposomes (dMLs) have been designed as a stimuli-responsive LD chemotherapy drug delivery system and tested in vitro using Huh-7 hepatocellular carcinoma cell line. The dMLs contained hydrophobic superparamagnetic iron oxide nanoparticles within the lipid bilayer and doxorubicin hydrochloride (DOX, 2 μM) within the aqueous core. Structural analysis by cryogenic transmission electron microscopy and dynamic light scattering showed that the assemblies were approximately 120 nm in diameter. Furthermore, the samples consisted of a mixture of dMLs and bare liposomes (no nanoparticles), which provided dual burst and spontaneous DOX release profiles, respectively. Cell viability results show that the cytotoxicity of DOX-loaded dMLs was similar to that of bare dMLs (∼10%), which indicates that spontaneous DOX leakage had little cytotoxic effect. However, when subjected to a physiologically acceptable radiofrequency (RF) electromagnetic field, cell viability was reduced up to 40% after 8h and significant cell death (>90%) was observed after 24h. The therapeutic mechanism was intracellular RF-triggered DOX release from the dMLs and not intracellular hyperthermia due to nanoparticle heating via magnetic losses.

A versatile stable platform for multifunctional applications: synthesis of a nitroDOPA–PEO–alkyne scaffold for iron oxide nanoparticles

A simple but powerful design of contemporary magnetic nanoparticle composites for biomedical applications.

Iron oxide nanoparticles with sizes, shapes and compositions resulting in different magnetization signatures as potential labels for multiparametric detection

Magnetic iron oxide nanoparticles differing in their size, shape (spherical, hexagonal, rods, cubes) and composition have been synthesized and modified using caffeic acid for transfer to aqueous media and stabilization of the particle suspensions at physiological pH. A super quantum interference device and the recently patented magnetic sensor MIAplex®, which registered a signal proportional to the second derivative of the magnetization curve, were used to study the magnetization behavior of the nanoparticles. The differences in the magnetic signatures of the nanoparticles (spheres and rods) make them promising candidates for the simultaneous detection of different types of biological molecules.

Smart photothermal-triggered bilayer phase transition in AuNPs-liposomes to release drug

Novel thermosensitive liposomes with embedded Au nanoparticles (AuNPs) in the liposome bilayer were prepared by a combination method of film build and supercritical CO(2) incubation. These AuNPs-liposomes possess AuNPs that are embedded in the bilayer and a drug that is encapsulated in the central aqueous compartment. The AuNPs in the liposomes can strongly absorb light energy and efficiently convert the absorbed energy to heat. The localized heat induces a phase transition in the liposome bilayer and releases the drug. The drug release from the AuNPs-liposomes can be controlled by the irradiation time and AuNPs concentration in the AuNPs-liposomes at room temperature, where the AuNPs function as a nanoswitch for triggering drug release both spatially and temporally. The results suggest that drug release from the AuNPs-liposomes is due to a photothermic effect that induces phase transition of the liposomes rather than destruction of the liposome bilayer.

Magnetophoresis at the nanoscale: tracking the magnetic targeting efficiency of nanovectors

Aim: Most of the research efforts in magnetic targeting have been focused on the development of magnetic nanovectors, while the investigation of methods for tracking their magnetic targeting efficiency remains inappropriately addressed. We propose herein a miniaturized approach for appraising magnetophoretic mobility at the nanoscale. Materials & methods: A simple and easy-to-use chamber including a microtip as a magnetic attractor was developed to perform magnetophoretic measurement at the size scale of nano-objects, and under bright field or fluorescence microscopy. Different sets of magnetic nanocontainers were produced and their magnetophoretic mobility was investigated. Real-time observations of the Brownian motion of the nanocontainers were also carried out for simultaneous size determination. Results: Attraction of the nanocontainers at the microtip is demonstrated as a qualitative method that immediately distinguishes magnetically responsive nano-objects. The combination of the analysis of Brownian motion, together with the magnetophoretic mobility, inferred both the size, the magnetophoretic velocity and the magnetic content of the nanocontainers. Additionally, nanomagnetophoresis experiments under fluorescence microscopy provided information on the constitutive core/shell integrity of the nanocontainers and the co-internalization of a fluorescent cargo. Conclusion: This nanomagnetophoresis method represents a promising tool to estimate the feasibility of magnetic targeting in laboratory routine.

Original submitted 28 November 2011; Revised submitted 28 February 2012; Published online 18 June 2012

Size-dependent nonlinear weak-field magnetic behavior of maghemite nanoparticles

The magnetic behavior at room temperature of maghemite nanoparticles of variable sizes (from 7 to 20 nm) is compared using a conventional super quantum interference device (SQUID) and a recently patented technology, called MIAplex. The SQUID usually measures the magnetic response versus an applied magnetic field in a quasi-static mode until high field values (from -4000 to 4000 kA m(-1)) to determine the field-dependence and saturation magnetization of the sample. The MIAplex is a handheld portable device that measures a signal corresponding to the second derivative of the magnetization around zero field (between -15 and 15 kA m(-1)). In this paper, the magnetic response of the size series is correlated, both in diluted and powder form, between the SQUID and MIAplex. The SQUID curves are measured at room temperature in two magnetic field ranges from -4000 to 4000 kA m(-1) (-5T to 5T) and from -15 to 15 kA m(-1). Nonlinear behavior at weak fields is highlighted and the magnetic curves for diluted solutions evolve from quasi-paramagnetic to superparamagnetic behavior when the size of the nanoparticles increases. For the 7-nm sample, the fit of the magnetization with the Langevin model weighted with log-normal distribution corresponds closely to the magnetic size. This confirms the accuracy of the model of non-interacting superparamagnetic particles with a magnetically frustrated surface layer of about 0.5 nm thickness. For the other samples (10-nm to 21-nm), the experimental weak-field magnetization curves are modeled by more than one population of magnetically responding species. This behavior is consistent with a chemically uniform but magnetically distinct structure composed of a core and a magnetically active nanoparticle canted shell. Accordingly the weak-field signature corresponds to the total assembly of the nanoparticles. The impact of size polydispersity is also discussed.

Electrostatic assembly of a DNA superparamagnetic nano-tool for simultaneous intracellular delivery and in situ monitoring

A superparamagnetic γFe(2)O(3) nanocarrier was developed, characterized by spectroscopic methods and evaluated for the delivery of a decoy oligonucleotide (dODN) in human colon carcinoma SW 480 cells. This nanoparticle-dODN bioconjugate (γFe(2)O(3)@dODN) was designed to target the signal transducer and activator of transcription 3, STAT3, a key regulator of cell survival and proliferation. We exploited a simple precipitation-redispersion mechanism for the direct and one-step complexation of a labeled decoy oligonucleotide with iron oxide nanoparticles (NPs). The cell internalization of the decoy γFe(2)O(3)@dODN nanoparticles is demonstrated and suggests the potential for DNA delivery in biological applications. Despite the increasing use of NPs in biology and medicine, convenient methods to quantify them within cells are still lacking. In this work, taking advantage of the nonlinear magnetic behavior of our superparamagnetic NPs, we have developed a new method to quantify in situ their internalization by cells.

FROM THE CLINICAL EDITOR

In this study, the authors demonstrate methods to quantify superparamagnetic nanocarriers within cells, taking advantage of the nonlinear magnetic behavior of the studied NPs.