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In this paper, rotation properties of suspended particles under an external rotating electric field (EREF) are investigated. Based on the re-distribution of surface-induced charges on moving particles, the torque exerting on particles by EREF is derived analytically. Furthermore, for the sol suspended in Newtonian fluid, the angular velocity of the rotating particle is formulated by the EREF and the dielectric constants of the particle and matrix. The result shows that the angular velocity of particles depends on the angular velocity of EREF, and is proportional to the square of EREF strength. The maximum angular velocity of rotating particles is reached if the angular velocity of EREF is equal to the reciprocal of the relaxation time of the induced charge.

Current chemotherapy treatments are limited by poor drug solubility, rapid drug clearance and systemic side effects. Additionally, drug penetration into solid tumors is limited by physical diffusion barriers [e.g., extracellular matrix (ECM)]. Nanoparticle (NP) blood circulation half-life, biodistribution and ability to cross extracellular and cellular barriers will be dictated by NP composition, size, shape and surface functionality. Here, we investigated the effect of surface charge of poly(lactide)-poly(ethylene glycol) NPs on mediating cellular interaction. Polymeric NPs of equal sizes were used that had two different surface functionalities: negatively charged carboxyl (COOH) and neutral charged methoxy (OCH₃). Cellular uptake studies showed significantly higher uptake in human brain cancer cells compared to noncancerous human brain cells, and negatively charged COOH NPs were uptaken more than neutral OCH₃ NPs in 2D culture. NPs were also able to load and control the release of paclitaxel (PTX) over 19 days. Toxicity studies in U-87 glioblastoma cells showed that PTX-loaded NPs were effective drug delivery vehicles. Effect of surface charge on NP interaction with the ECM was investigated using collagen in a 3D cellular uptake model, as collagen content varies with the type of cancer and the stage of the disease compared to normal tissues. Results demonstrated that NPs can effectively diffuse across an ECM barrier and into cells, but NP mobility is dictated by surface charge. In vivo biodistribution of OCH₃ NPs in intracranial tumor xenografts showed that NPs more easily accumulated in tumors with less collagen. These results indicate that a robust understanding of NP interaction with various tumor environments can lead to more effective patient-tailored therapies.

Different from the traditional cancer cell targeting through protein biomarkers, strong negative surface charges of cancer cells over normal cells derived from the dramatic excretion of lactate acid by cancer cells due to their glycolysis have been testified as an effective cancer cell binding strategy. In our previous work, polyethylenimine (PEI)-functionalized iron oxide nanoparticles (NPs) with strong positive surface charge and good photothermal property have been applied to kill cancer cells in vitro. Considering the obvious cytotoxicity of the first generation of positively charged nanotherapeutics, second generation of magnetic nanotherapeutics with tunable surface charges was designed and prepared by shield of positively charged surface areas by negatively charged gold nanoparticles (AU NPs). In addition to reducing the cytotoxicity of original NPs, the photothermal property of magnetic NP core was simultaneously enhanced. Herein, the correlation of the capping degree of the positive surface charge by AU NPs and the photothermal inhibition of cancer cells was investigated.

Isolation of circulating tumor cells (CTCs) from cancer patients is of high value for disease monitoring and metastasis diagnosis. Although many new detection methods have emerged in recent years, the detection of CTCs is a current challenge due to lack of specific and sensitive markers. In our previous work, cancer cell surfaces, from over 20 cancer cell lines, have been shown to be negatively-charged regardless of their phenotype by using electrically-charged nanoparticles as a probe. The strong electrostatic interaction between the negative cancer cells and positively charged nanoparticles can well remain in a physiological liquid environment in the presence of serum proteins, enabling effective binding between them. As a result, the cancer cells can be magnetically separated by employing an external magnet. In this technical report, we present preliminary results on the investigation of CTC isolation from both mimetic and clinical blood samples. We show high CTC detection sensitivity by the positively-charged magnetic nanoparticles (PMNs) even at the original concentration of 10 cells per mL mimetic blood sample. The CTCs in the peripheral blood of colorectal cancer patients were isolated and identified by cellular morphology and immunofluorescence staining.

Heterogeneous materials are inherently dielectric, and charge distribution and transport in such materials involves complex local fields and polarizations that are remarkably sensitive to morphology and the interaction of conduction and permittivity. Trial and error design of such material systems is time consuming and expensive, and often ineffectual. However, heterogeneous materials are essential for energy conversion and storage, and they have become the foundation for major advances in the performance of devices such as batteries, fuel cells, separation membranes, and solar cells. The present paper presents some relationships in support of rational design based on an extensive experimental validation of the concepts and analysis that form a foundation for that design. Salient results include the prediction and confirmation of volume fraction effects (including nondilute mixtures), and the prediction and direct measurement of surface charge effects at internal interfaces as a function of constituent morphology and orientation.

The creations and manipulations of vortexes in ferroelectric materials with external stimuli are expected to be used in the design and fabrication of sensing materials and multifunctional electronic devices. In this work, we investigated the surface charge-induced multi-vortex evolution using the phase-field simulations in BiFeO₃. A combination of domain morphology, polarization distribution and winding number calculation was considered. The results show that vortex and anti-vortex exist simultaneously in pairs, and the total value of winding numbers is always 0. In addition, the minimum distance $\mathrm{\Delta }l$ between the surface charge regions is 9nm when the vortex domains are independent of each other. This work provides a reference for the manipulation of ferroelectric vortex induced by surface charges, which lays a theoretical foundation for the design and fabrication of high-density vortex memories.

Poling effects of hydroxyapatite (HAp) ceramics were studied on histological reaction. The sintered HAp ceramics were cut and sliced for rectangular plates (5 × 8 × 0.5mm). These specimens were electrically poled (surface charged) in a DC field of 1000 V/cm for 1 h. The poled HAp ceramics were implanted in bones of beagle dogs. The bones with the poled HAp samples were extracted after 3 and 7 days implantation. The histlogical reactions were estimated with the decalcified sections stained by hematoxylin eosin (H-E) and toluidine blue as well as the non decalcified sections by H-E, toluidine blue and Villanueva bone stain. New bone formations were observed on the negatively poled surface (N-surface). No contacted new bone formations but blood cell liners were observed on the positively poled surface (P-surface). Non poled HAp phases (0-surface) showed the intermediate reaction between the P- and N-faces. It was suggested that poled HAp vectored the cells and lured on the N-surface, whereas the P-surface had inhibitory effects on cell adhesion.