Janus magnetic cellular spheroids for vascular tissue engineering

Cell aggregates, or spheroids, have been used as building blocks to fabricate scaffold-free tissues that can closely mimic the native three-dimensional in vivo environment for broad applications including regenerative medicine and high throughput testing of drugs. The incorporation of magnetic nanoparticles (MNPs) into spheroids permits the manipulation of spheroids into desired shapes, patterns, and tissues using magnetic forces. Current strategies incorporating MNPs often involve cellular uptake, and should therefore be avoided because it induces adverse effects on cell activity, viability, and phenotype. Here, we report a Janus structure of magnetic cellular spheroids (JMCS) with spatial control of MNPs to form two distinct domains: cells and extracellular MNPs. This separation of cells and MNPs within magnetic cellular spheroids was successfully incorporated into cellular spheroids with various cellular and extracellular compositions and contents. The amount of cells that internalized MNPs was quantified and showed that JMCSs resulted in significantly lower internalization (35%) compared to uptake spheroids (83%, p < 0.05). Furthermore, the addition of MNPs to cellular spheroids using the Janus method has no adverse effects on cellular viability up to seven weeks, with spheroids maintaining at least 82% viability over 7 weeks when compared to control spheroids without MNPs. By safely incorporating MNPs into cellular spheroids, results demonstrated that JMCSs were capable of magnetic manipulation, and that magnetic forces used during magnetic force assembly mediate fusion into controlled patterns and complex tissues. Finally, JMCSs were assembled and fused into a vascular tissue construct 5 mm in diameter using magnetic force assembly.     

Sensitive in vivo cell detection using size-optimized superparamagnetic nanoparticles

Magnetic nanoparticle (MNP) enabled cell visualization with magnetic resonance imaging (MRI) is currently an intensively studied area of research. In the present study, we have synthesized polyethylene glycolated (PEG) MNPs and validated their suitability as MR cell labeling agents in in vitro and in vivo experiments. The labeling of therapeutic potent mesenchymal stem cells (MSCs) with small core and large core MNPs was evaluated. Both MNPs were, in combination with a transfection agent, stably internalized into the MSCs and didn't show an effect on cell metabolism. The labeled cells showed high contrast in MRI phantom studies. For quantification purposes, the MRI contrast generating properties of cells labeled with small core MNPs were compared with large core MNPs and with the commercial contrast agent Endorem. MSCs labeled with the large core MNPs showed the highest contrast generating properties in in vitro phantom studies and in in vivo intracranial stereotactic injection experiments, confirming the size–relaxivity relationship in biological systems. Finally, the distribution of MSCs pre-labeled with large core PEGylated MNPs was visualized non-invasively with MRI in a glioma model.     

Anti-oxidative effects and harmlessness of asymmetric Au@Fe3O4 Janus particles on human blood cells

The physical properties of asymmetric Janus particles are highly promising for future biomedical applications. However, only a few data is available on their biological impact on human cells. We investigated the biological impact of different Au@Fe₃O₄ Janus particle formulations in vitro to analyse specific uptake modalities and their potential cytotoxic effects on human cells of the blood regarding intravenous injection. We demonstrate that Au@Fe₃O₄ Janus particles exhibit a similar or even better biocompatibility compared to the well-studied spherical iron oxide nanoparticles. The impact of Janus particles on cells depends mainly on three factors. (1) Surface functionalization: NH₂-functionalization of the Au or iron oxide domain induces a pronounced reduction of cell viability in contrast to non-functionalized variants which is caused by the damage of intracellular membranes. (2) The nature of the metal oxide component, greatly affects cell viability, as shown by a comparison with Au@MnO Janus particles. (3) The overall surface charge and the size of nanoparticles have a higher impact on internalization and cellular metabolism than the Janus character per se. Interestingly, Janus particle associated DNA damage is independent of the effects on the cellular ATP level. However, not only the structure and functionalization of the Janus particle surface determines the particle's adhesion and intracellular fate, but also the constitution of the cell surface as shown by different modification experiments. The multifactorial in vitro approach presented in this study demonstrated the high capability of the Janus particles. Especially Au@Fe₃O₄ Janus particles bear great potential for applications in vivo.     

Short-chain PEG molecules strongly bound to magnetic nanoparticle for MRI long circulating agents

This study developed an approach for the synthesis of magnetic nanoparticles coated with three different polyethylene glycol (PEG)-derived molecules. The influence of the coating on different properties of the nanoparticles was studied. Magnetite nanoparticles (7 and 12 nm in diameter) were obtained via thermal decomposition of a coordination complex as an iron precursor to ensure nanoparticle homogeneity in size and shape. Particles were first coated with meso-2,3-dimercaptosuccinic acid by a ligand exchange process to remove oleic acid, followed by modification with three distinct short-chain PEG polymers, which were covalently bound to the nanoparticle surface via 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride activation of the carboxylic acids. In all cases, colloidal suspensions had hydrodynamic sizes <100 nm and low surface charge, demonstrating the effect of PEG coating on the aggregation properties and steric stabilization of the magnetic nanoparticles. The internalization and biocompatibility of these materials in the HeLa human cervical carcinoma cell line were tested. Cells preincubated with PEG-coated iron nanoparticles were visualized outside the cells, and their biocompatibility at high Fe concentrations was demonstrated using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Finally, relaxivity parameters (r₁ and r₂) were used to evaluate the efficiency of suspensions as magnetic resonance imaging contrast agents; the r₂ value was similar to that for Resovist and up to four times higher than that for Sinerem, probably due to the larger nanoparticle size. The time of residence in blood of the nanoparticles measured from the relaxivity values, and the Fe content in blood was doubled for rats and rabbits due to the PEG on the nanoparticle surface. The results suggest that this PEGylation strategy for large magnetic nanoparticles (>10 nm) holds promise for biomedical applications.     

Engineered protein nanoparticles for in vivo tumor detection

Two different protein nanoparticles that are totally different in shape and surface structure, i.e. Escherichia coli DNA-binding protein (eDPS) (spherical, 10 nm) and Thermoplasma acidophilum proteasome (tPTS) (cylindrical, 12 × 15 nm) were engineered for in vivo optical tumor detection: arginine–glycine–aspartic acid (RGD) peptide (CDCRGDCFC) was genetically inserted to the surface of each protein nanoparticle, and also near-infrared fluorescence dye was chemically linked to the surface lysine residues. The specific affinity of RGD for integrin (α_vβ₃) facilitated the uptake of RGD-presenting protein nanoparticles by integrin-expressing tumor cells, and also the protein nanoparticles neither adversely affected cell viability nor induced cell damage. After intravenously injected to tumor-bearing mice, all the protein nanoparticles successfully reached tumor with negligible renal clearance, and then the surface RGD peptides caused more prolonged retention of protein nanoparticles in tumor and accordingly higher fluorescence intensity of tumor image. In particular, the fluorescence of tumor image was more intensive with tPTS than eDPS, which is due presumably to longer in vivo half-life and circulation of tPTS that originates from thermophilic and acidophilic bacterium. Although eDPS and tPTS were used as proof-of-concept in this study, it seems that other protein nanoparticles with different size, shape, and surface structure can be applied to effective in vivo tumor detection.     

In vivo multimodal magnetic particle imaging (MPI) with tailored magneto/optical contrast agents

Magnetic Particle Imaging (MPI) is a novel non-invasive biomedical imaging modality that uses safe magnetite nanoparticles as tracers. Controlled synthesis of iron oxide nanoparticles (NPs) with tuned size-dependent magnetic relaxation properties is critical for the development of MPI. Additional functionalization of these NPs for other imaging modalities (e.g. MRI and fluorescent imaging) would accelerate screening of the MPI tracers based on their in vitro and in vivo performance in pre-clinical trials. Here, we conjugated two different types of poly-ethylene-glycols (NH₂-PEG-NH₂ and NH₂-PEG-FMOC) to monodisperse carboxylated 19.7 nm NPs by amide bonding. Further, we labeled these NPs with Cy5.5 near infra-red fluorescent (NIRF) molecules. Bi-functional PEG (NH₂-PEG-NH₂) resulted in larger hydrodynamic size (∼98 nm vs. ∼43 nm) of the tracers, due to inter-particle crosslinking. Formation of such clusters impacted the multimodal imaging performance and pharmacokinetics of these tracers. We found that MPI signal intensity of the tracers in blood depends on their plasmatic clearance pharmacokinetics. Whole body mice MPI/MRI/NIRF, used to study the biodistribution of the injected NPs, showed primary distribution in liver and spleen. Biodistribution of tracers and their clearance pathway was further confirmed by MPI and NIRF signals from the excised organs where the Cy5.5 labeling enabled detailed anatomical mapping of the tracers.in tissue sections. These multimodal MPI tracers, combining the strengths of each imaging modality (e.g. resolution, tracer sensitivity and clinical use feasibility) pave the way for various in vitro and in vivo MPI applications.     

Solvent-free atom transfer radical polymerization for the preparation of poly(poly(ethyleneglycol) monomethacrylate)-grafted Fe3O4 nanoparticles: synthesis, characterization and cellular uptake

Poly(poly(ethyleneglycol) monomethacrylate) (P(PEGMA))-grafted magnetic nanoparticles (MNPs) were successfully prepared via a solvent-free atom transfer radical polymerization (ATRP) method. The macroinitiators were immobilized on the surface of 6.4±0.8 nm Fe₃O₄ nanoparticles via effective ligand exchange of oleic acid with 3-chloropropionic acid (CPA), which rendered the nanoparticles soluble in the PEGMA monomer. The so-obtained P(PEGMA)-grafted MNPs have a uniform hydrodynamic particle size of 36.0±1.2 nm. The successful grafting of P(PEGMA) on the MNP surface was ascertained from FTIR and XPS analyses. The uptake of the MNPs by macrophage cells is reduced by two-orders of magnitude to <2 pg Fe/cell after surface grafting with P(PEGMA). Furthermore, the morphology and viability of the macrophage cells cultured in a medium containing 0.2 mg/mL of P(PEGMA)-grafted MNPs were found similar to those of cells cultured without nanoparticles, indicating an absence of significant cytotoxicity effects. T₂-weighted magnetic resonance imaging (MRI) of P(PEGMA)-grafted MNPs showed that the magnetic resonance signal is enhanced significantly with increasing nanoparticle concentration in water. The R₁ and R₂ values per millimole Fe, and R₂/R₁ value of the P(PEGMA)-grafted MNPs were calculated to be 8.8 mm⁻¹ s⁻¹, 140 mm⁻¹ s⁻¹, and 16, respectively. These results indicate that the P(PEGMA)-grafted MNPs have great potential for application in MRI of specific biotargets.     

Manipulating the surface coating of ultra-small Gd2O3 nanoparticles for improved T1-weighted MR imaging

In this report, monodispersed ultra-small Gd₂O₃ nanoparticles capped with hydrophobic oleic acid (OA) were synthesized with average particle size of 2.9 nm. Two methods were introduced to modify the surface coating to hydrophilic for bio-applications. With a hydrophilic coating, the polyvinyl pyrrolidone (PVP) coated Gd₂O₃ nanoparticles (Gd₂O₃-PVP) showed a reduced longitudinal T₁ relaxation time compared with OA and cetyltrimethylammonium bromide (CTAB) co-coated Gd₂O₃ (Gd₂O₃-OA-CTAB) in the relaxation study. The Gd₂O₃-PVP was thus chosen for its further application study in MRI with an improved longitudinal relaxivity r₁ of 12.1 mm⁻¹ s⁻¹ at 7 T, which is around 3 times as that of commercial contrast agent Magnevist^®. In vitro cell viability in HK-2 cell indicated negligible cytotoxicity of Gd₂O₃-PVP within preclinical dosage. In vivo MR imaging study of Gd₂O₃-PVP nanoparticles demonstrated considerable signal enhancement in the liver and kidney with a long blood circulation time. Notably, the OA capping agent was replaced by PVP through ligand exchange on the Gd₂O₃ nanoparticle surface. The hydrophilic PVP grants the Gd₂O₃ nanoparticles with a polar surface for bio-application, and the obtained Gd₂O₃-PVP could be used as an in vivo indicator of reticuloendothelial activity.     

Abrasion and fatigue resistance of PDMS containing multiblock polyurethanes after accelerated water exposure at elevated temperature

Segmented polyurethane multiblock polymers containing polydimethylsiloxane and polyether soft segments form tough and easily processed thermoplastic elastomers (PDMS-urethanes). Two commercially available examples, PurSil 35 (denoted as P35) and Elast-Eon E2A (denoted as E2A), were evaluated for abrasion and fatigue resistance after immersion in 85 °C buffered water for up to 80 weeks. We previously reported that water exposure in these experiments resulted in a molar mass reduction, where the kinetics of the hydrolysis reaction is supported by a straight forward Arrhenius analysis over a range of accelerated temperatures (37–85 °C). We also showed that the ultimate tensile properties of P35 and E2A were significantly compromised when the molar mass was reduced. Here, we show that the reduction in molar mass also correlated with a reduction in both the abrasion and fatigue resistance. The instantaneous wear rate of both P35 and E2A, when exposed to the reciprocating motion of an ethylene tetrafluoroethylene (ETFE) jacketed cable, increased with the inverse of the number averaged molar mass (1/M_n). Both materials showed a change in the wear surface when the number-averaged molar mass was reduced to ≈16 kg/mole, where a smooth wear surface transitioned to a ‘spalling-like’ pattern, leaving the wear surface with ≈0.3 mm cracks that propagated beyond the contact surface. The fatigue crack growth rate for P35 and E2A also increased in proportion to 1/M_n, after the molar mass was reduced below a critical value of ≈30 kg/mole. Interestingly, this critical molar mass coincided with that at which the single cycle stress–strain response changed from strain hardening to strain softening. The changes in both abrasion and fatigue resistance, key predictors for long term reliability of cardiac leads, after exposure of this class of PDMS-urethanes to water suggests that these materials are susceptible to mechanical compromise in vivo.     

Morphological zeta-potential variation of nanoporous anodic alumina layers and cell adherence

Nanoscale surface modification of biomedical implant materials offers enhanced biological activity concerning protein adsorption and cell adherence. Nanoporous anodic alumina oxide (AAO) layers were prepared by electrochemical oxidation of thin Al-seed layers in 0.22 M C₂H₂O₄, applying anodization voltages of 20–60 V. The AAO layers are characterized by a mean pore diameter varying from 15 to 40 nm, a mean pore distance of 40–130 nm, a total porosity of ∼10% and a thickness of 560 ± 40 nm. Zeta potential and isoelectric point (iep) were derived from streaming potential measurements and correlated to the topology variation of the nanoporous AAO layers. With decreasing pore diameter a shift of iep from ∼7.9 (pore diameter 40 nm) to ∼6.7 (pore diameter 15 nm) was observed. Plain alumina layers, however, possess an iep of ∼9. Compared to the plain alumina surface an enhanced adherence and activity of hFOB cells was observed on the nanoporous AAO after 24 h culture with a maximum at a pore size of 40 nm. The topology-induced change of the electrochemical surface state may have a strong impact on protein adsorption as well as on cell adhesion, which offers a high potential for the development of bioactive AAO coatings on various biomaterial substrates.     

Controlling protein–particle adsorption by surface tailoring colloidal alumina particles with sulfonate groups

In this study, we demonstrate the control of protein adsorption by tailoring the sulfonate group density on the surface of colloidal alumina particles. The colloidal alumina (d₅₀ = 179 ± 8 nm) is first accurately functionalized with sulfonate groups (SO₃H) in densities ranging from 0 to 4.7 SO₃H nm^?2. The zeta potential, hydrophilic/hydrophobic properties, particle size, morphology, surface area and elemental composition of the functionalized particles are assessed. The adsorption of three model proteins, bovine serum albumin (BSA), lysozyme (LSZ) and trypsin (TRY), is then investigated at pH 6.9 ± 0.3 and an ionic strength of 3 mM. Solution depletion and zeta potential experiments show that BSA, LSZ and TRY adsorption is strongly affected by the SO₃H surface density rather than by the net zeta potential of the particles. A direct correlation between the SO₃H surface density, the intrinsic protein amino acid composition and protein adsorption is observed. Thus a continuous adjustment of the protein adsorption amount can be achieved between almost no coverage and a theoretical monolayer by varying the density of SO₃H groups on the particle surface. These findings enable a deeper understanding of protein–particle interactions and, moreover, support the design and engineering of materials for specific biotechnology, environmental technology or nanomedicine applications.     

The transport of non-surfactant based paclitaxel loaded magnetic nanoparticles across the blood brain barrier in a rat model

There is much interest in utilizing the intrinsic properties of magnetic nanoparticles (MNPs) for the theranostic approaches in medicine. With an aim to develop a potential therapeutics for glioma treatment, efficacy of aqueous dispersible paclitaxel loaded MNPs (Pac-MNPs) were studied in glioblastoma cell line (U-87). The identified potential receptor, glycoprotein non-metastatic melanoma protein B (GPNMB) overexpressed by glioblastoma cells, was actively targeted using GPNMB conjugated Pac-MNPs in U-87 cells. As blood brain barrier (BBB) is the primary impediment in the treatment of glioblastoma, therefore, an attempt was taken to evaluate the biodistribution and brain uptake of Pac-MNPs in rats. The bioavailability of Pac-MNPs illustrated a prolonged blood circulation in vivo, which demonstrated the presence of significant amounts of drug in rat brain tissues as compared to native paclitaxel. Further, the transmission electron microscopy (TEM) study revealed significant accumulation of the Pac-MNPs in the brain tissues. Being an effective contrast enhancement agent for magnetic resonance imaging (MRI) at tissue levels, the MNPs devoid of any surfactant demonstrated enhanced contrast effect in liver and brain imaging. Hence, the significant prevalence of drugs in the rat brain tissues, in vitro targeting potentiality as well as the augmented contrast effect elicit the non-invasive assessment and theranostic applications of MNPs for brain tumor therapy.     

Protein adsorption and cell adhesion on cationic,neutral, and anionic 2-methacryloyloxyethyl phosphorylcholine copolymer surfaces

Protein adsorption and cell adhesion on cationic, neutral, and anionic water-soluble 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer surfaces were compared. These model MPC copolymers coated SiO₂ surfaces exhibited comparable surface ζ-potentials of 26.1 mV, near 0 mV, and ?24.2 mV, respectively. X-ray photoelectron spectroscopy analyses indicated the similarities and the differences in the surface composition between the sample surfaces. Atomic force microscopy analyses revealed that the type of the charged moiety did not affect the surface roughness. Static contact angle measurements and dynamic contact angle analyses not only indicated that the surfaces were very hydrophilic in general, but also provided information on the surface mobility and the dominant role of MPC at the surface in aqueous conditions. Comparing with the SiO₂ substrates on which protein seriously adsorbed and cell heavily adhered, three MPC copolymers coated surfaces, despite their different charge properties, exhibited significantly low adsorbed amounts of different proteins having various electrical natures and totally no cell adhesion. This suggested that the incorporation of charged moieties in the MPC copolymers did not significantly inspire both the protein adsorption and cell adhesion. The MPC moieties were predominant at the surface when in contact with aqueous conditions and thereby dominated the bio-adsorptions, while the possible effect from electrostatic interactions would be too small and too limited to influence the overall situation. Therefore, these MPC copolymer surfaces can satisfy those biological applications requiring not only electrical but also non-biofouling properties.     

Multilevel surface engineering of nanostructured TiO2 on carbon-fiber-reinforced polyetheretherketone

As an implantable material, carbon-fiber-reinforced polyetheretherketone (CFRPEEK) possesses an adjustable elastic modulus similar to that of cortical bone and is a prime candidate to replace metallic surgical implants. However, the bioinertness and poor osteogenic properties of CFRPEEK limit its clinical application as orthopedic implants. In this work, titanium ions are introduced energetically into CFRPEEK by plasma immersion ion implantation (PIII). Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) reveal the formation of nanopores with the side wall and bottom embedded with ∼20 nm TiO₂ nanoparticles on the CFRPEEK surface. Nanoindentation measurements confirm the stability and improved elastic resistance of the structured surfaces. In vitro cell adhesion, viability assay, and real-time PCR analyses disclose enhanced adhesion, proliferation, and osteo-differentiation of rat bone mesenchymal stem cells (bMSCs). The multilevel structures on CFRPEEK also exhibit partial antibacterial activity to Staphylococcus aureus and Escherichia coli. Our results indicate that a surface with multifunctional biological properties can be produced by multilevel surface engineering and application of CFRPEEK to orthopedic and dental implants can be broadened and expedited based on this scheme.     

Quantitative control of active targeting of nanocarriers to tumor cells through optimization of folate ligand density

The active targeting delivery system has been widely studied in cancer therapy by utilizing folate (FA) ligands to generate specific interaction between nanocarriers and folate receptors (FRs) on tumor cell. However, there is little work that has been published to investigate the influence of the definite density of the FA ligands on the active targeting of nanocarriers. In this study, we have combined magnetic-guided iron oxide nanoparticles with FA ligands, adjusted the FA ligand density and then studied the resulting effects on the active targeting ability of this dual-targeting drug delivery system to tumor cells. We have also optimized the FA ligand density of the drug delivery system for their active targeting to FR-overexpressing tumor cells in vitro. Prussian blue staining, semi-thin section of cells observed with transmission electron microscopy (TEM) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) have shown that the optimal FA density is from 2.3 × 10¹⁸ to 2.5 × 10¹⁸ per gram nanoparticles ((g·NPs)⁻¹). We have further tried to qualitatively and quantitatively control the active targeting and delivering of drugs to tumors on 4T1-bearing BALB/c mice. As expected, the in vivo experimental results have also demonstrated that the FA density of the magnetic nanoparticles (MNPs) could be optimized for a more easily binding to tumor cells via the multivalent linkages and more readily internalization through the FR-mediated endocytosis. Our study can provide a strategy to quantitatively control the active targeting of nanocarriers to tumor cells for cancer therapy.     

Curcumin-conjugated magnetic nanoparticles for detecting amyloid plaques in Alzheimer's disease mice using magnetic resonance imaging (MRI)

Diagnosis of Alzheimer's disease (AD) can be performed with the assistance of amyloid imaging. The current method relies on positron emission tomography (PET), which is expensive and exposes people to radiation, undesirable features for a population screening method. Magnetic resonance imaging (MRI) is cheaper and is not radioactive. Our approach uses magnetic nanoparticles (MNPs) made of superparamagnetic iron oxide (SPIO) conjugated with curcumin, a natural compound that specifically binds to amyloid plaques. Coating of curcumin-conjugated MNPs with polyethylene glycol-polylactic acid block copolymer and polyvinylpyrrolidone by antisolvent precipitation in a multi-inlet vortex mixer produces stable and biocompatible curcumin magnetic nanoparticles (Cur-MNPs) with mean diameter <100 nm. These nanoparticles were visualized by transmission electron microscopy and atomic force microscopy, and their structure and chemistry were further characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and Fourier transform infrared spectroscopy. Cur-MNPs exhibited no cytotoxicity in either Madin–Darby canine kidney (MDCK) or differentiated human neuroblastoma cells (SH-SY5Y). The P_app of Cur-MNPs was 1.03 × 10⁻⁶ cm/s in an in vitro blood–brain barrier (BBB) model. Amyloid plaques could be visualized in ex vivo T2*-weighted magnetic resonance imaging (MRI) of Tg2576 mouse brains after injection of Cur–MNPs, and no plaques could be found in non-transgenic mice. Immunohistochemical examination of the mouse brains revealed that Cur-MNPs were co-localized with amyloid plaques. Thus, Cur–MNPs have the potential for non-invasive diagnosis of AD using MRI.     

Water-dispersible magnetic carbon nanotubes as T2-weighted MRI contrast agents

An efficient MRI T₂-weighted contrast agent incorporating a potential liver targeting functionality was synthesized via the combination of superparamagnetic iron oxide (SPIO) nanoparticles with multiwalled carbon nanotubes (MWCNTs). Poly(diallyldimethylammonium chloride) (PDDA) was coated on the surface of acid treated MWCNTs via electrostatic interactions and SPIO nanoparticles modified with a potential targeting agent, lactose–glycine adduct (Lac–Gly), were subsequently immobilized on the surface of the PDDA–MWCNTs. A narrow magnetic hysteresis loop indicated that the product displayed superparamagnetism at room temperature which was further confirmed by ZFC (zero field cooling)/FC (field cooling) curves measured by SQUID. The multifunctional MWCNT-based magnetic nanocomposites showed low cytotoxicity in vitro to HEK293 and Huh7 cell lines. Enhanced T₂ relaxivities were observed for the hybrid material (186 mm⁻¹ s⁻¹) in comparison with the pure magnetic nanoparticles (92 mm⁻¹ s⁻¹) due to the capacity of the MWCNTs to “carry” more nanoparticles as clusters. More importantly, after administration of the composite material to an in vivo liver cancer model in mice, a significant increase in tumor to liver contrast ratio (277%) was observed in T₂ weighted magnetic resonance images.     

Production and characterization of the cores of the "R" strain of mosquito iridescent virus.

Cores of “R” strain of mosquito iridescent virus (RMIV) were produced in vitro by reacting intact virus with chymotrypsin. Isolation of the cores from undegraded virus and outer capsid protein was accomplished by density gradient and differential centrifugations. Negatively stained core particles had a diameter of 176.1 ± 6.0 nm when examined in the electron microscope. The density of the particles as measured in cesium chloride gradients was 1.33, and the s_20,w was 3126 as measured in the analytical centrifuge. The molecular weight of the cores was calculated to be 1.84 × 10⁹ daltons. Protein, DNA, and lipid analysis of the cores accounted for all but 48.0% of the protein of intact virus particles. SDS-polyacrylamide gel electrophoresis of the cores compared with that of intact virus showed that only a 55,000 molecular-weight protein was absent in the former. The cores did not infect larvae or an Aedes aegypti cell line, and serological comparisons of intact virus and cores showed the two did not share common surface antigens.     

Avidin as a model for charge driven transport into cartilage and drug delivery for treating early stage post-traumatic osteoarthritis

Local drug delivery into cartilage remains a challenge due to its dense extracellular matrix of negatively charged proteoglycans enmeshed within a collagen fibril network. The high negative fixed charge density of cartilage offers the unique opportunity to utilize electrostatic interactions to augment transport, binding and retention of drug carriers. With the goal of developing particle-based drug delivery mechanisms for treating post-traumatic osteoarthritis, our objectives were, first, to determine the size range of a variety of solutes that could penetrate and diffuse through normal cartilage and enzymatically treated cartilage to mimic early stages of OA, and second, to investigate the effects of electrostatic interactions on particle partitioning, uptake and binding within cartilage using the highly positively charged protein, Avidin, as a model. Results showed that solutes having a hydrodynamic diameter ≤10 nm can penetrate into the full thickness of cartilage explants while larger sized solutes were trapped in the tissue's superficial zone. Avidin had a 400-fold higher uptake than its neutral same-sized counterpart, NeutrAvidin, and >90% of the absorbed Avidin remained within cartilage explants for at least 15 days. We report reversible, weak binding (K_D ∼ 150 μm) of Avidin to intratissue sites in cartilage. The large effective binding site density (N_T ∼ 2920 μm) within cartilage matrix facilitates Avidin's retention, making its structure suitable for particle based drug delivery into cartilage.     

Sub-100 nm hollow Au–Ag alloy urchin-shaped nanostructure with ultrahigh density of nanotips for photothermal cancer therapy

The ‘sea urchin’-like nanostructures with particular small size (<100 nm) and abundant multi-tips have not yet been employed for the cancer photothermal therapy (PTT). Here we report sub-100 nm hollow Au–Ag alloy nanourchins (HAAA-NUs) with ultrahigh density of nanotips synthesized via a facile seed-mediated growth. The HAAA-NUs exhibit a remarkably integrated high-quality photothermal feature including well-defined but tunable surface plasmon resonance peak, strong absorption (2.2 × 10¹⁰ M⁻¹ cm⁻¹) as well as high photothermal conversion efficiency (80.4%) in the near-infrared region. Importantly, the HAAA-NUs demonstrate improved photothermal stability verified via continuous exposition and cyclic irradiation of laser beam. The cell assay, in vitro cell ablation and in vivo breast cancer treatment verify that the HAAA-NUs are superior photothermal agent for photothermal tumor ablation therapy owing to low toxicity and high cell destruction capability.