Elsevier

International Immunopharmacology

Volume 7, Issue 13, 15 December 2007, Pages 1813-1818
International Immunopharmacology

Preliminary report
The effects of nano-silver on the proliferation and cytokine expression by peripheral blood mononuclear cells

https://doi.org/10.1016/j.intimp.2007.08.025Get rights and content

Abstract

Silver could prove to be a valuable alternative raw material for antibiotics and disinfectants as it is relatively free of adverse effects. Nano-silver is now been put to practical use in commonly used items, such as, clothes, electric home appliances, and electronic industry, but has not been widely applied in the medical or pharmacological fields. This study was designed to investigate the effects of nano-silver on the production of cytokines by and on the proliferation of peripheral blood mononuclear cells (PBMCs). In addition, we investigated the potential cytotoxic effects of nano-silver on PBMCs.

PBMCs from healthy human volunteers were stimulated with 5 μg/ml phytohaemagglutinin (PHA) in the presence of varying concentrations of nano-silver. PBMC proliferations were measured using an aqueous cell proliferation assay kit and supernatants were analyzed using enzyme-linked immunosorbent assays. Interleukin-5 (IL-5), interferon-γ (INF-γ), and tumor necrosis factor-α (TNF-α) protein levels were measured to determine the activation state of PBMCs.

At levels of over 15 ppm, nano-silver was found to have a significant cytotoxic effect on PBMCs, and PHA-induced cytokine productions were significantly inhibited by nano-silver (IL-5: at 10 ppm, INF-γ and TNF-α at 3 ppm).

Although nano-silver had a cytotoxic effect at high concentration, nano-silver modulated cytokine production in a concentration-dependent manner. These experimental data suggest that nano-silver could be used to treat immunologic and inflammatory diseases.

Introduction

Allergic and infectious inflammations require cytokine production by lymphocytes and other inflammatory cells. The productions of these chemical mediators are key events in the initiation and regulation of an immune response, and reducing or blocking these productions and the deleterious effects of cytokines are important aspects of modifying inflammatory processes. Recently attention has been focused on selective cytokine inhibitory agents, such as, corticosteroids, and anti-cytokine antibodies [1], [2].

Generally nanotechnology (NT) is defined as the design, characterization and application of structures, devices and systems by controlling shape and size at nanometer scale [3], and NT has already found practical applications in health and daily life.

Silver has long been known to be a strong antimicrobial and disinfectant. It exhibits broad-spectrum antimicrobial activity in vitro by binding to microbial DNA, that preventing bacterial replication and to the sulfhydryl groups of the metabolic enzymes in the bacterial electron transport chain, causing their inactivation [4]. Moreover, infections associated with medical prostheses result in major morbidity and can be life threatening, and many investigators have tried to coat the surfaces of prosthetic devices with an antimicrobial substances [5], [6], [7]. Although several kinds of silver-coated medical prostheses have been developed, their abilities to prevent infection have not been collectively addressed. NT developed nano-silver particle which has antimicrobial and disinfectant characteristics, but it has not been well studied in vitro. Nanoparticles have eccentric properties depending on the size. As the size is smaller, catalytic activity is stronger. However the critical size and their quantitative analysis of catalystic activity as its size are not well understood. In this study, size of nanoparticles was smaller than 5 nm. This preliminary study was undertaken to investigate the potential clinical usefulness of nano-silver in the context of its anti-inflammatory effects.

Section snippets

Isolation and culture of peripheral blood mononuclear cells (PBMCs)

Heparinized venous blood was collected from healthy volunteers after obtaining informed consent which was approved by the Institutional Review Boarder at the Daegu Catholic University Hospital. PBMCs were isolated by density gradient centrifugation on Histopaque (Sigma, St. Louis, MO). Cells from the interphase were harvested, washed and resuspended at 2 × 106 cells/ml in RPMI-1640 medium (Gibco, Rockville, MD) supplemented with 10% calf-serum, 2 mmol/l glutamine and 50 μM 2-mercaptoethanol. The

Cytotoxic effect of nano-silver

The results are shown in Fig. 1, which illustrates the effect of varying concentrations of nano-silver on PBMC survival. Cell proliferation was found to be significantly decreased at nano-silver concentrations exceeding 15 ppm. More than 70% of absorbance was decreased after treatment with nano-silver at 15 ppm by MTT assay and more than 30% was decreased with CellTracker Green CMFDA, after 72 h incubation.

Anti-inflammatory and anti-proliferative effect of nano-silver

When PBMCs were cultured for 72 h with PHA, cells proliferation index increased 3.5 times

Discussion

Silver is one of the most effective antibiotic substances known and has been used to treat human ailments for over 100 years due to its natural antibacterial and nontoxic properties [8]. Thus, silver offers a valuable alternative that is relatively free of adverse effects of antibiotics and disinfectants with low toxicity profile and excellent tissue tolerance. The free silver ion has two distinctive antimicrobial mechanisms. The first involves denaturation, the disulfide bonds of bacterial

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