Imaging and Chemotherapeutic Comparisons of Iron Oxide Nanoparticles Chemically and Physically Coated with Poly(ethylene glycol)-b-Poly(ε-caprolactone)-g-Poly(acrylic acid)

We designed a new copolymer, poly(ethylene glycol)-block-poly(ε-caprolactone)-graft-poly(acrylic acid) (PAA-PEC), which could be chemically and physically coated onto iron oxide (Fe3O4) nanoparticles for theranostic applications. The chemically PAA-PEC-coated Fe3O4 nanoparticles (PAA-PEC-IO) were prepared using the carboxylic groups of PAA-PEC to bind the Fe3O4 nanoparticles during a co-precipitation reaction. Because of the amphiphilic properties of PAA-PEC, the compound self-assembled into a core-shell structure. The hydrophobic oleic acid-coated Fe3O4 nanoparticles could then be physically encapsulated inside the hydrophobic core of PAA-PEC (PAA-PEC-OA-IO) using an emulsion technique. A similar amount of iron content was controlled in both the PAA-PEC-IO and PAA-PEC-OA-IO (-23%). The particle diameters, morphologies, superparamagnetism, drug loading efficiency, and transversal relaxivity (r2) were studied and compared between the two magnetic nanoparticles. All results displayed the chemically-synthesized PAA-PEC-IO nanoparticles had higher potential than did the physically-synthesized PAA-PEC-OA-IO as an MRI contrast agent and a drug delivery carrier. Rodamine123-linked PAA-PEC-IO (PAA-PEC-IO-Rh123) was used as a molecular probe. Flow cytometric diagrams indicated that cellular internalization of PAA-PEC-IO occurred primarily through clathrin-mediated endocytosis.

Chondroitin sulfate-polyethylenimine copolymer-coated superparamagnetic iron oxide nanoparticles as an efficient magneto-gene carrier for microRNA-encoding plasmid DNA delivery

MicroRNA-128 (miR-128) is an attractive therapeutic molecule with powerful glioblastoma regulation properties. However, miR-128 lacks biological stability and leads to poor delivery efficacy in clinical applications. In our previous study, we demonstrated two effective transgene carriers, including polyethylenimine (PEI)-decorated superparamagnetic iron oxide nanoparticles (SPIONs) as well as chemically-conjugated chondroitin sulfate-PEI copolymers (CPs). In this contribution, we report optimized conditions for coating CPs onto the surfaces of SPIONs, forming CPIOs, for magneto-gene delivery systems. The optimized weight ratio of the CPs and SPIONs is 2 : 1, which resulted in the formation of a stable particle as a good transgene carrier. The hydrodynamic diameter of the CPIOs is ∼136 nm. The gel electrophoresis results demonstrate that the weight ratio of CPIO/DNA required to completely encapsulate pDNA is ≥3. The in vitro tests of CPIO/DNA were done in 293 T, CRL5802, and U87-MG cells in the presence and absence of an external magnetic field. The magnetofection efficiency of CPIO/DNA was measured in the three cell lines with or without fetal bovine serum (FBS). CPIO/DNA exhibited remarkably improved gene expression in the presence of the magnetic field and 10% FBS as compared with a gold non-viral standard, PEI/DNA, and a commercial magnetofection reagent, PolyMag/DNA. In addition, CPIO/DNA showed less cytotoxicity than PEI/DNA and PolyMag/DNA against the three cell lines. The transfection efficiency of the magnetoplex improved significantly with an assisted magnetic field. In miR-128 delivery, a microRNA plate array and fluorescence in situ hybridization were used to demonstrate that CPIO/pMIRNA-128 indeed expresses more miR-128 with the assisted magnetic field than without. In a biodistribution test, CPIO/Cy5-DNA showed higher accumulation at the tumor site where an external magnet is placed nearby.

Angiopep-pluronic F127-conjugated superparamagnetic iron oxide nanoparticles as nanotheranostic agents for BBB targeting

Pluronic® F127-modified water-dispersible poly(acrylic acid)-bound iron oxide (PF127-PAAIO) nanoparticles have been prepared as diagnostic agents. A blood-brain-barrier penetrating peptide, angiopep-2 (ANG), was further conjugated onto the surface of the PF127-PAAIO (ANG-PF127-PAAIO) for brain targeting. The ANG-PF127-PAAIO shows negligible cell cytotoxicity, better cellular uptake, and higher T₂-weighted image enhancement than the PF127-PAAIO in U87 cells. Using an ex vivo blood-brain barrier (BBB) model, we showed that the ANG-PF127-PAAIO shows better permeability to bypass the BBB. This is because the ANG-PF127-PAAIO has a dual-targeting ability, recognition of the low-density lipoprotein receptor-related protein and clathrin-mediated receptor on the U87 surface. Thus, the ANG-PF127-PAAIO is a potential nanotheranostic agent for brain dysfunction.

A specific tumor-targeting magnetofluorescent nanoprobe for dual-modality molecular imaging

Poly(acrylic acid) was decorated onto Fe(3)O(4) resulting in a highly water-soluble superparamagnetic iron oxide. The Poly(acrylic acid) iron oxide (PAAIO) complexes possess specific magnetic properties in the presence of an external magnetic field and are attractive contrast agents for magnetic resonance imaging (MRI). The free carboxylic groups of PAAIO exposed on the surface allow for covalent attachment of a fluorescent dye, Rhodamine 123 (Rh123) to form PAAIO-Rh123, which permits applications in fluorescence imaging. PAAIO-Rh123 is therefore a dual-modality molecular probe. In order to endow specific properties to compounds that target cancer cells and to prevent recognition by the reticuloendothelial system (RES), folic acid-linked poly(ethylene glycol) (FA-PEG) was further conjugated onto PAAIO-Rh123. The amounts of Rh123 and FA-PEG on the modified iron oxides were quantitatively determined by elemental analysis. The iron content was determined by inductively coupled plasma-optical emission spectrometer (ICP-OES). The particle diameters were characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). Superparamagnetism was confirmed by the superconducting quantum interference device (SQUID) magnetometer. The cellular internalization efficacy of the modified iron oxides was realized in folate-overexpressed FR(+) and folate-deficient FR(-) KB cells by flow cytometry and confocal laser scanning microscopy (CLSM). The quantitative amount of iron internalized into different harvested KB cells was measured by ICP-OES. The T(2)-weighted MR images were tested in FR(+) KB cells.

A model to study the disc degeneration process

Initiation and propagation of different types of events that lead to disc degeneration and the effect of the degenerating process on the disc mechanical performance is difficult to study by experimental methods. This study aimed to develop and use a finite element model of a motion segment without posterior elements to study the disc degeneration process. The model was used to study the development of anular tears, nuclear clefts, and endplate fractures and subsequent propagation of these degenerative processes due to compressive and bending loads. The analyses showed that the failure always started at the end plates indicating that they are the weak link in the body-disc-body unit. The analyses also showed that anular injuries are unlikely to be produced by pure compressive loads. The model predicted that it would require a larger extension moment as compared to flexion moment to initiate and propagate failure in a motion segment, which leads to the conclusion that the motion segment is stiffer in extension. The model also suggested that the presence of discrete peripheral tears in the anulus fibrosus may have a role in the formation of concentric anular tears and in accelerating the degenerating process of the disc.