Kun Fang

Quasi-spherical silver nanoparticles: aqueous synthesis and size control by the seed-mediated Lee-Meisel method.

Silver nanoparticles (AgNPs) are attracting tremendous attention in biomedicine, and their related performances are shape and size-dependent. For biomedical applications, water-soluble AgNPs are necessary. However, aqueous syntheses of AgNPs with controlled shape and size are relatively difficult as the balance between nucleation and growth is hard to regulate. This paper describes a robust method for controllable synthesis of quasi-spherical AgNPs based on the combination of the seed-mediated growth and the Lee-Meisel method by thermal reduction of AgNO(3) with citrate. In the presented method, citrate-stabilized AgNPs with tunable sizes up to 80 nm were achieved through one-step or stepwise growth process using qualified spherical 4 nm AgNPs as starter seeds. Specially, the two main difficulties (formation of nanorods and secondary nucleation during the growth stage) in the previous studies have been effectively overcome by tailoring the experimental parameters such as the reaction temperature and the seed amount, without extra additives, pH adjustment, and laser treatment. The crucial factors that affect the uniformity of the resulting AgNPs are discussed.

Bubble Microreactors Triggered by an Alternating Magnetic Field as Diagnostic and Therapeutic Delivery Devices

Advances in the medical treatment of a wide variety of pathophysiological conditions require the development of better therapeutic agents, as well as a combination of the required therapeutic agentswith diagnostic-integrated devices. With the development of microand nanotechnologies, the better intelligentmedical systems and devices have profoundly impacted medical theranostic techniques. Based on multifunctional device platforms, the interests of these studies mainly focusonmultimodal imagingand simultaneous therapy, which provide patients with imaging (ultrasound, computed tomography, magnetic resonance imaging (MRI), etc.) and effective therapeutic agents responding directly at the disease sites. In recent years, microand nanoscale intelligent systems have become a desirable method to maximize the efficacy of therapeutic treatments in numerous ways, because they can release their contents in a ‘‘smart or intelligent’’ way by responding to external triggers or biomarkers. Thesedelivery vehicles include polymeric micelles, gels, liposomes, small colloidal particles, and nanoengineered polymeric or polyelec-

Silver nanoparticle-embedded microbubble as a dual-mode ultrasound and optical imaging probe.

Microbubbles (MBs) coupled with nanoparticles represent a new class of multifunctional probe for multiscale biomedical imaging and drug delivery. In this study, we describe the development of multifunctional, microscale microbubble probes that are composed of a nitrogen gas core and a biocompatible polymer shell harboring silver nanoparticles (AgNPs). Ultrasound imaging studies show that the presence of AgNPs in the MB significantly improves the contrast of ultrasound images. The AgNPs within individual MB can be also imaged by using dark-field microscopy (DFM), which suggests that AgNPs in the polymer shell adopt multiple structural forms. AgNPs are released from the polymer shell following a brief exposure to an ultrasonic field and are subsequently taken up by living cells. AgNPs within labeled cells are imaged by DFM, while surface-enhanced Raman scattering is used to identify specific cytoplasmic biomolecules that bind to the surface of the AgNP. Collectively, these studies demonstrate the application of multifunctional MBs for micrometer scale contrast-enhanced ultrasound imaging, as vehicles for the ultrasound-based delivery of optical probes and drugs to cells, and for imaging of chemical sensing of individual nanopartiles within cells and tissue.

Magnetic field activated drug release system based on magnetic PLGA microspheres for chemo-thermal therapy

Controlled drug delivery systems have been extensively investigated for cancer therapy in order to obtain better specific targeting and therapeutic efficiency. Herein, we developed doxorubicin-loaded magnetic PLGA microspheres (DOX-MMS), in which DOX was encapsulated in the core and high contents (28.3 wt%) of γ-Fe2O3 nanoparticles (IOs) were electrostatically assembled on the surface of microsphere to ensure the high sensitivity to response of an external alternating current magnetic field (ACMF). The IOs in PLGA shell can both induce the heat effect and trigger shell permeability enhancement to release drugs when DOX-MMs was activated by ACMF. Results show that the cumulative drug release from DOX-MMs exposed to ACMF for 30 min (21.6%) was significantly higher (approximately 7 times higher) than that not exposed to ACMF (2.8%). The combination of hyperthermia and enhanced DOX release from DOX-MMS is beneficial for in vitro 4T1 breast cancer cell apoptosis as well as effective inhibition of tumor growth in 4T1 tumor xenografts. Therefore, the DOX-MMS can be optimized as powerful delivery system for efficient magnetic responsive drug release and chemo-thermal therapy.

PLLA microcapsules combined with silver nanoparticles and chlorhexidine acetate showing improved antibacterial effect

In this study, composite antibacterial microcapsules combining of two antibacterial agents: chlorhexidine acetate and silver nanoparticle were prepared. The chlorhexidine acetate was encapsulated inside of the microcapsules and nano-sized silver particles were modified on the surface of microcapsules by electrostatic adsorption methods. Results show that this method decreases the silver usage dramatically, and promises a sustained antibacterial effect >30days. These microcapsules can also be modified on the surface of polymer films easily, which demonstrated the potential in functionalizing the implanted materials with antibacterial property.

The effect of ratios of egg white to yolk on the shape of droplets

• The adjacent droplets tended to form into a longitudinal structure to decrease surface tension and stabilize itself.

The effects of macroporosity and stiffness of poly[(methyl vinyl ether)-alt-(maleic acid)] cross-linked egg white simulations of an aged extracellular matrix on the proliferation of ovarian cancer cells

Ageing and remodelling of the extracellular matrix (ECM) leads to enzyme activation, resulting in a fibrotic microenvironment and fluctuating ECM stiffness. In this study, prepared egg white (EW) cross-linked with poly[(methyl vinyl ether)-alt-(maleic acid)] (P(MVE-alt-MA)) with macroporous structures were used to simulate an aged extracellular matrix that affected the malignant behaviour of cancer cells at different stages. Increased macroporosity and stiffness properties clearly enhanced the proliferation of cancer cells. In other words, different levels of EW cross-linking had different effects on cell malignancy, thereby determining the ability and speed of cell migration in scaffolds. The study showed that porosity and stiffness changes in the matrix were possible mechanisms for cancer cell invasion and metastasis besides blood vessels and lymphatic invasion in human body. P(MVE-alt-MA)-cross-linked EW contained a major component of ECM and provided a useful model to evaluate the proliferation and metastasis of cancer cells in vitro. This has important significance when it comes to exploring the effects of the material microenvironment on tumour prevention and treatment.