Nanomedicine – an overview | ScienceDirect Topics

§ May 21st, 2019 § Filed under Nano Medicine Comments Off on Nanomedicine – an overview | ScienceDirect Topics

12.1 Why Nanomaterials?

Nanomedicine is a hot field. Up to 2004, only 72 scientific articles on nanomedicine had been published according to Medline, but during 20052015 that number soared to 10.502 (data retrieved July 30, 2015 from http://www.pubmed.gov). It can be argued, however, that nanoparticles (NPs) have an old history in medicine. Nanosilver used against bacterial infections is a well-known example, but nanosized agents have also been applied for many years to modulate immune responses. Colloidal gold used to treat rheumatoid arthritis1 and alum used as adjuvant for various vaccines2 have contained nanomaterials long before that term became familiar, or before the presence of nanosized components has been considered to be relevant. It is thus not quite true that there is no experience on effects of artificial nanomaterials on the human body. Many practical uses of NPs go back a long time, but medical applications are of special relevance, since here the agents are applied to health-compromised persons, they are applied intentionally, often locally, and usually in doses that would never be reached, for example, during unintentional work place exposure.

The use of NPs for modulating immunity seems to be an obvious perspective. Engineered NPs are nonself and they overlap in size with viruses (mostly 10200nm size range3), so they fall well within the target size range to which immunity is capable to respond, and since at least some types of NPs are toxic, they can be expected to result in danger signals as well (Fig. 12.1).

Figure 12.1. Nanoscale sizes compared to other relevant objects. Nanomaterials are in the size range of biological molecules and entities. The biological and the physical world interact on the same scale, which is the basis for many nanospecific effects that can be exploited for medical purposes.

In addition, some nanomaterials exhibit repetitive patterns originating from the process of synthesis, so even recognition by pattern recognition receptors may be envisioned. The present overview will highlight features of nanomedical agents without restricting itself to the ISO standard, which defines nanoparticles as objects that have in all three dimensions sizes between 1100nm (ISO/TS 27687:2008 Nanotechnologies Terminology and definitions for nano objects nanoparticle, nanofibre and nanoplate). Objects with sizes up to several hundred nm have been described and used as nanomedical agents, so in the present review, all materials that have been described as such will be considered as nanomedical agents. Strictly defined, nanopharmaceuticals should not only be in the nanosize range, but should also exploit the particular properties of the nanoscale for the therapeutic effect, so the nanoscale should add functionalities that cannot be obtained by using either the compound chemicals or bulk materials.4

Considering investigational and approved nanomedical products, the most prominent area of current use is in the treatment of cancers, where drug targeting is a major issue, but several approved drugs are also aiming at immunity.57 A general overview of interactions between nanomaterials and the immune system has been provided by several recent books.810 Here we will focus on medical applications that aim at modifying immune responses in a preventive or a therapeutic setting. In the context of nanosafety research, some types of NPs have been shown to stimulate the immune system, while others were reported to repress immunity. Confusingly, both claims have been made sometimes for very similar materials, reflecting the by now well recognized problem that many nanotoxicology studies have not provided enough data to rule out problems like contamination with endotoxin or with synthesis chemicals, insufficiently well described materials, particle aging effects, assay interference by particles, or batch-to-batch variation between nominally identical particle preparations.11 Quality issues in nanosafety testing have recently been extensively described by H. Krug.12

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Nanomedicine - an overview | ScienceDirect Topics

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