Catherine C. Berry

Dextran and albumin derivatised iron oxide nanoparticles: influence on fibroblasts in vitro

Magnetic nanoparticles have been used for biomedical purposes for several years. In recent years, nanotechnology has developed to a stage that makes it possible to engineer particles to provide opportunities for the site-specific delivery of drugs. To this end a variety of iron oxide particles have been synthesised. The size and surface of the particles are crucial factors in the application of the particles. This study therefore involves the use of magnetic nanoparticles synthesised and derivatised with either dextran or albumin, compared to identical underivatised plain particles. This influence in vitro was assessed using human dermal fibroblasts and various techniques to observe cell-particles interaction, including light and fluorescence microscopy, scanning and transmission electron microscopy. The results indicate that the derivatised particles induce alterations in cell behaviour and morphology distinct from the plain particles, suggesting that cell response can be directed via specifically engineered particle surfaces.

Progress in functionalization of magnetic nanoparticles for applications in biomedicine

Magnetic nanoparticles (mNPs) ranging from the nanometre and micrometre scale have been widely applied in recent years in the area of biomedicine. They contain unique magnetic properties and due to their size can function at a cellular level, making them attractive candidates for cell labelling, imaging, tracking and as carriers. A recent surge of interest in nanotechnology has boosted the breadth and depth of the nanoparticle research field. This review aims to supplement a previously published review in 2003 and address more recent advances in the uses and bioapplications of mNPs and future interesting perspectives.

Possible exploitation of magnetic nanoparticle–cell interaction for biomedical applications

Magnetic nanoparticles have been advocated for use in magnetic resonance (MR) image enhancement and as bio-carriers in biological systems for many years. However it is only in recent years that the fields of nanotechnology, materials science and cell biology have combined to enable us to fully comprehend the potential uses of such nanoparticles in biomedical applications. This short review aims to detail some of the more recent advances using magnetic nanoparticles in biological research, highlighting possible biomedical applications and relating how the advancement of such research relies on parallel interdisciplinary research in materials chemistry.

Receptor-mediated targeting of magnetic nanoparticles using insulin as a surface ligand to prevent endocytosis

Superparamagnetic iron oxide nanoparticles have been used for many years as magnetic resonance imaging contrast agents or in drug delivery applications. Tissue and cell-specific drug targeting by these nanoparticles can be achieved by employing nanoparticle coatings or carrier-drug conjugates that contain a ligand recognized by a receptor on the target cell. In this study, superparamagnetic iron oxide nanoparticles with specific shape and size have been prepared and coupled to insulin for their targeting to cell expressed surface receptors and thereby preventing the endocytosis. The influence of these nanoparticles on human fibroblasts is studied using various techniques to observe cell-nanoparticle interaction that includes light, scanning, and transmission electron microscopy studies. The derivatization of the nanoparticle surface with insulin-induced alterations in cell behavior that were distinct from the underivatized nanoparticles suggests that cell response can be directed via specifically engineered particle surfaces. The results from cell culture studies showed that the uncoated particles were internalized by the fibroblasts due to endocytosis, which resulted in disruption of the cell membrane. In contradiction, insulin-coated nanoparticles attached to the cell membrane, most likely to the cell-expressed surface receptors, and were not endocytosed. The presence of insulin on the surface of the nanoparticles caused an apparent increase in cell proliferation and viability. One major problem with uncoated nanoparticles has been the endocytosis of particles leading to irreversible entry. These results provide a route to prevent this problem. The derivatized nanoparticles show high affinity for cell membrane and opens up new opportunities for magnetic cell separation and recovery that may be of crucial interest for the development of cellular therapies.

Notice of Violation of IEEE Publication Principles Nuclear Localization of HIV-1 Tat Functionalized Gold Nanoparticles

The impermeable nature of the cell plasma membrane limits the therapeutic uses of many macromolecules and there is therefore a growing effort to circumvent this problem by designing strategies for targeted intracellular delivery. During the last decade several cell penetrating peptides, such as the HIV-1 tat peptide, have been shown to traverse the cell membrane, where integral protein transduction domains (PTDs) are responsible for their cellular uptake, and to reach the nucleus while retaining biological activity. It has since been discovered that PTDs can enable the cellular delivery of conjugated biomolecules and even nanoparticles, but nuclear delivery has remained problematic. This present study focuses on the development of water soluble, biocompatible gold nanoparticles of differing size functionalized with the HIV-1 tat PTD with the aim of producing nuclear targeting agents. The particles were subsequently tested in vitro with a human fibroblast cell line, with results demonstrating successful nanoparticle transfer across the plasma membrane, with 5 nm particles achieving nuclear entry while larger 30 nm particles are retained in the cytoplasm, suggesting entry is blocked via nuclear pores dimensions.

Intracellular delivery of nanoparticles via the HIV-1 tat peptide.

Functionalized nanoparticles are heralded as part of the future with regards to targeted cell and nuclear delivery. However, direct intracellular and intranuclear delivery has, until recently, been difficult to achieve owing to the impermeable nature of the plasma and nuclear membranes. During the past 15 years, a range of peptides, termed cell-penetrating peptides (CPPs), which have the ability to translocate into living cells, have been discovered. Thus, in more recent years, the combination of CPPs with nanoparticles, enabling CPP-mediated cell delivery, has opened up many avenues of research. This review discusses the use of various CPPs, focusing on tat peptide, to functionalize nanoparticles and the possible move from the laboratory to the clinic.

The effect of static magnetic fields and tat peptides on cellular and nuclear uptake of magnetic nanoparticles.

Magnetic nanoparticles are widely used in bioapplications such as imaging (MRI), targeted delivery (drugs/genes) and cell transfection (magnetofection). Historically, the impermeable nature of both the plasma and nuclear membranes hinder potential. Researchers combat this by developing techniques to enhance cellular and nuclear uptake. Two current popular methods are using external magnetic fields to remotely control particle direction or functionalising the nanoparticles with a cell penetrating peptide (e.g. tat); both of which facilitate cell entry. This paper compares the success of both methods in terms of nanoparticle uptake, analysing the type of magnetic forces the particles experience, and determines gross cell response in terms of morphology and structure and changes at the gene level via microarray analysis. Results indicated that both methods enhanced uptake via a caveolin dependent manner, with tat peptide being the more efficient and achieving nuclear uptake. On comparison to control cells, many groups of gene changes were observed in response to the particles. Importantly, the magnetic field also caused many change in gene expression, regardless of the nanoparticles, and appeared to cause F-actin alignment in the cells. Results suggest that static fields should be modelled and analysed prior to application in culture as cells clearly respond appropriately. Furthermore, the use of cell penetrating peptides may prove more beneficial in terms of enhancing uptake and maintaining cell homeostasis than a magnetic field.

Influence of external uniaxial cyclic strain on oriented fibroblast-seeded collagen gels.

This study investigates the influence of cyclic tensile strain, applied to fully contracted fibroblast-seeded collagen constructs. The constructs were preloaded to either 2 or 10 mN. The preloaded constructs were subsequently subjected to a further 10% cyclic strain (0-10%) at 1 Hz, using a triangular waveform, or were cultured in the preloaded state. In all cases cellular viability was maintained during the conditioning period. Cell proliferation was enhanced by the application of cyclic strain within constructs preloaded to both 2 and 10 mN. Collagen synthesis was enhanced by cyclic strain within constructs preloaded at 2 mN only. The profile of matrix metalloproteinase (MMP) expression, determined by zymography, was broadly similar in constructs preloaded at 2 mN with or without the application of cyclic strain. By contrast, constructs preloaded at 10 mN and subjected to cyclic strain expressed enhanced levels of staining for latent MMP-1, latent MMP-9, and both latent and active MMP-2, when compared with the other conditioning regimens. The structural stiffness of constructs preloaded at 2 mN and subjected to cyclic strain was enhanced compared with control specimens, reflecting the increase in collagen synthesis. By contrast, the initial failure loads for cyclically strained constructs preloaded at 10 mN were reduced, potentially because of enhanced catabolic activity.

Working together: the combined application of a magnetic field and penetratin for the delivery of magnetic nanoparticles to cells in 3D

Nanoparticles (NPs) are currently being developed as vehicles for in vivo drug delivery. Two of the biggest barriers facing this therapy are the site-specific targeting and consequent cellular uptake of drug-loaded NPs(1). In vitro studies in 2D cell cultures have shown that an external magnetic field (MF) and functionalization with cell-penetrating peptides (CPPs) have the capacity to overcome these barriers. This study aimed to investigate if the potential of these techniques, which has been reported in 2D, can be successfully applied to cells growing in a 3D environment. As such, this study provides a more realistic assessment of how these techniques might perform in future clinical settings. The effect of a MF and/or penetratin attachment on the uptake of 100 and 200 nm fluorescent iron oxide magnetic NPs (mNPs) into a fibroblast-seeded 3D collagen gel was quantified by inductively coupled plasma mass spectrometry. The most suitable mNP species was further investigated by fluorescence microscopy, histology, confocal microscopy, and TEM. Results show that gel mNP uptake occurred on average twice as fast in the presence of a MF and up to three times faster with penetratin attachment. In addition, a MF increased the distance of mNP travel through the gel, while penetratin increased mNP cell localization. This work is one of the first to demonstrate that MFs and CPPs can be effectively translated for use in 3D systems and, if applied together, will make excellent partners to achieve therapeutic drug delivery in vivo.

Simple conjugated polymer nanoparticles as biological labels

The use of nanoparticles in biology, especially in cellular imaging, is extremely promising and offers numerous advantages over existing organic dye systems. There are, however, constraints that need to be addressed before the use of such materials in mainstream clinical applications can be realized. One of the main concerns is the use of metal-containing particles that are potentially toxic or interfere with other diagnostic processes. Here, we present the use of simple conjugated polymer nanoparticles as alternative photostable cellular optical imaging agents.