Safety Evaluation of a Prototypical Diazirine-Based Covalent Crosslinker and Molecular Adhesive

bis-Diazirine reagents are increasingly being used as polymer crosslinkers, adhesives, and photopatterning agents in the materials sciences literature, but little effort has been made thus far to document their chemical safety profile. Here, we describe the results of a detailed toxicity assessment of a representative bis-diazirine. Safety was evaluated by a series of in vitro assays, which found the product to be non-mutagenic in bacterial tester strains TA98 and TA100, non-corrosive and non-irritating to skin, and requiring no classification for eye irritation or serious damage. While in vitro tests do not capture the integrated whole animal system, and thus cannot completely rule out the possibility of adverse responses, the results of this study suggest a desirable safety profile for bis-diazirine reagents and provide a solid foundation upon which to add in vivo assessment of safety risk and dose-response studies.

The antimicrobial activity, hydrophobicity and toxicity of tri(n-alkyl)sulfoniums and tris(n-alkylphenyl) sulfoniums, and their relationships

The antimicrobial activity, hydrophobicity and toxicity of tri(n-alkyl)sulfoniums (TASs) and tris{4-(n-alkylphenyl)}sulfoniums (TAPSs), and their relationships were investigated. The antimicrobial activity against the tested strains tended to increase with the increase in the sulfonium ClogP between 7 and approximately 12 and beyond that decreased with the increase in the ClogP in both sulfoniums. The antimicrobial activities of the most TAPSs were higher than those of the TASs at similar ClogP values. The mutagenicity of the TASs and the TAPSs was judged to be negative. The acute oral toxicity decreased with the increase in the ClogP in the both sulfoniums. The skin irritation/corrosion increased with the increase in the ClogP between approximately 7 and 12, and beyond that decreased or similar with the increase in the ClogP in both sulfoniums. It is noted that the acute toxicity and the skin irritation/corrosion of the TAPSs were clearly higher than those of the TASs at a similar ClogP. In comparing the sulfoniums to representative quaternary ammonium compounds (QACs), the antimicrobial activities of the some sulfoniums were higher than those of QACs and the toxicity was lower. Therefore, some sulfoniums could be utilized in many fields instead of the presently and widely-used QACs.

Validity and ethics of the human 4-h patch test as an alternative method to assess acute skin irritation potential

For more than 50 years, the Draize rabbit skin irritation test has reigned supreme as the regulatory method of choice for the identification of skin irritant chemicals. To date no in vitro alternative test has been validated as an adequate replacement. However, one potential option, to test the endpoint of concern (skin irritation) in the species of concern (man) has been overlooked. The advent of predictive in vitro tools for the identification of substances corrosive to the skin has opened up the practical possibility of carrying out safe and ethical studies on small panels of humans. The human 4-h patch test has been developed to meet the needs of identifying chemical skin irritation potential, providing data which is inherently superior to that given by a surrogate model, such as the rabbit. This paper reviews in detail the present state of the human 4-h patch test, highlighting its advantages and noting its utility as the 'gold standard' on which to build future in vitro models.

In vitro and human testing strategies for skin irritation

Prior to the manufacture, transport, and marketing of chemicals or products, it is critical to assess their potential for skin toxicity (corrosion or irritation), thereby protecting the worker and consumer from adverse skin effects due to intended or accidental skin exposure. Traditionally, animal testing procedures have provided the data needed to assess the more severe forms of skin toxicity, and current regulations may require animal test data before permission can be obtained to manufacture, transport, or market chemicals or the products that contain them. In recent years, the use of animals to assess skin safety has been opposed by some as inhumane and unnecessary. The conflicting needs of the industrial toxicologist to (1) protect human safety, (2) comply with regulations, and (3) reduce animal testing have led to major efforts to develop alternative, yet predictive, test methods. A variety of in vitro skin corrosion test methods have been developed and several have successfully passed initial international validation. These have included skin or epidermal equivalent assays that have been shown to distinguish corrosive from noncorrosive chemicals. These skin/epidermal equivalent assays have also been modified and used to assess skin irritation potential relative to existing human exposure test data. The data show a good correlation between in vitro assay data and different types of human skin irritation data for both chemicals and consumer products. The effort to eliminate animal tests has also led to the development of a novel human patch test for assessment of acute skin irritation potential. A case study shows the benefits of in vitro and human skin irritation tests compared to the animal tests they seek to replace, and strategies now exist to adequately assess human skin irritation potential without the need to rely on animal test methods.