I laughed, but since I briefly ran a small business the comment struck a chord with me. After much thought, I think small business owners and academics have two key problems in common: Since outside of a teaching schedule no one is really telling you what to do with every minute of your time, it can be hard to choose what to do next — especially if all the tasks seem equally important. Problem One leads to being over-committed, probably constantly.
The two main issues considered in this review are the evidence for the ability of these NPs to penetrate the skin to reach viable cells and the potential toxicity exerted by them.
This review is a further update to include relevant literature that has been published between May and August The majority of in vitro studies using both animal and human skin and in vivo studies have shown that both ZnO and TiO2 NPs either do not penetrate or minimally penetrate the stratum corneum and underlying layers of skin.
This suggests that systemic absorption, hence toxicity, is highly unlikely. In conclusion, on current evidence, neither TiO2 nor ZnO NPs are likely to cause harm when used as ingredients in sunscreens and when sunscreens are used as directed. Introduction Nanoparticle characteristics Dermal exposure Cytotoxicity and genotoxicity Conclusion Bibliography 1.
Introduction Inorganic UV filters zinc oxide ZnO and titanium dioxide TiO2 have been used as ingredients in sunscreens for over three decades. However, one apparent disadvantage of ZnO and TiO2 is that in their macroparticulate bulk form in sunscreens, they are visible on the skin as an opaque layer resulting in reluctance of consumers to use the products.
This undesirable visual effect has been addressed by decreasing the particle size of these metal oxides to nanoparticle NP form see Section 2.
When used in this NP form, these oxides cannot be seen on the skin but retain or even augment their UV-sunscreening properties. These NPs are particularly useful in sunscreens because of their intrinsic ability to filter ultraviolet UV A as well as UVB wave length spectra, thus providing broader protection than any other sunscreening agent.
A review on these issues was first published by the TGA inwhich was updated in and again in This scientific review report is limited to the review of safety concerns surrounding ZnO and TiO2 NPs present in sunscreens.
The two main issues considered in this review are the evidence for ability of these NPs to penetrate the skin to reach viable cells and the potential toxicity exerted by them. Nanoparticle characteristics For the purpose of this report, the definition of TiO2 and ZnO NPs includes materials within the nanosize range of 1 to nm.
Nanosized TiO2 and ZnO exist in three separate states: Primary particles cluster together to form aggregates and are the smallest units present in a final sunscreen formulation Butler et al.
The larger agglomerates form when aggregates bind loosely during the manufacturing process Schilling et al. These are not efficient UV absorbers so they need to be broken down into the more efficient aggregates, which are chemically bound.
This review includes assessments of NP preparations that contain aggregates and agglomerates. The latter have been included because of their yet unclear potential to disaggregate and disagglomerate when applied on the skin in a sunscreen formulation.
A preliminary study by Bennett et al. Thus, any potential hazard linked with nanosized particles is likely to be reduced if these particles aggregate and form structures above the nanoscale, which then do not dissociate into smaller NPs, thus reducing their ability to penetrate the skin.
The anatase form is substantially more photocatalytic and adheres more strongly to skin than the rutile form Turci et al. The form and size of the NPs used in the studies summarised in this review are specified if these parameters were described in the study.
Furthermore, in a review of photoprotection, Lautenschlager et al. A number of studies published since these safety reviews have assessed the potential of ZnO NPs or TiO2 NPs to cause skin irritation reversible skin damagecorrosion irreversible necrotic damage extending into the dermis or sensitisation in the absence of UV or non-UV light.
In a mouse model of atopic dermatitis employed to determine whether ZnO NPs could exacerbate the inflammatory pathology associated with allergic skin conditions, ZnO NPs were applied to the skin of mice sensitised to ovalbumin Ilves et al.
ZnO NPs were detected in the epidermal and dermal layers of the skin of both sensitised and non-sensitised mice in regions where skin had been tape-stripped a procedure employed to mimic skin damage.
The number of immune cells T lymphocytes, neutrophils, eosinophils and mast cells infiltrating the skin in antigen-sensitised mice was attenuated in the presence of ZnO NPs.
These data demonstrate that ZnO NPs can potentially penetrate the dermis, exert an anti-inflammatory effect on allergic skin but enhance IgE generation.
Despite the potential for an allergic response, the authors conclude that the benefits of using sunscreens to combat the development of skin malignancies outweigh the possible risks of exacerbating allergic symptoms Ilves et al.
In other studies, ZnO NPs failed to cause irritation or sensitisation.
ZnO NPs also failed to induce skin sensitization in guinea pigs during or up to 48 h after the elicitation phase after an induction phase that involved weekly application of NPs for 3 weeks Kim et al. As outlined below, the findings of the great majority of these studies indicated an apparent inability of TiO2 and ZnO NPs to reach viable cells in the dermis.Review the guidelines in the Literature Review Matrix, included in the Learning Resources.
Formulate a research question around your issue as indicated in Part I. Then complete Part II of the Matrix, identifying the resources you will use, search terms and criteria, and Boolean search strings. This topic has study abstracts on Curcumin indicating that it may have therapeutic value in the treatment of Oxidative Stress, Inflammation, and DNA damage.
You can find some example matrices and matrix templates on the Writing Center's website. Matrices help students to organize their information and are helpful tools for . Guidelines and Measures provides users a place to find information about AHRQ's legacy guidelines and measures clearinghouses, National Guideline Clearinghouse (NGC) and National Quality Measures Clearinghouse (NQMC).
Organizational Tools As you read and evaluate your literature there are several different ways to organize your research. Courtesy of Dr. Gary Burkholder in the School of Psychology, these sample matrices are one option to help organize your articles.
Writing A Literature Review and Using a Synthesis Matrix you have to know that when writing a literature review, the goal of the researcher is to determine the current state of knowledge about a particular topic by asking, “What do we know or not know about this issue?” In conducting this type of research, it is imperative to examine.