title: Repeated dose dermal toxicity study of nano zinc oxide with Sprague-Dawley rats.
abstract: BACKGROUND
  In light of the increased use of zinc oxide nanoparticles in cosumer products such as sunscreens, there is a need for screening the potential dermal toxicity of these nanoparticles.
  
  
  OBJECTIVE
  The aim of this study is to identify the risk associated with the nano zinc oxide at realistic exposure levels through dermal route. This study is to understand the toxic potential of nano zinc oxide through repeated dermal exposure for a period of 28 days.
  
  
  METHODS
  Six- to 8-week-old Sprague-Dawley rats were applied with three different doses (75, 180, and 360 mg/kg body weight) of nano zinc oxide (20 nm) at 5 days/week basis for a period of 28 days. The dose levels were calculated taking into consideration the percentage of nanomaterial in the sunscreen, number of application times, and average weight of the consumer in order to assess the realistic risk related to it. Control group animals were applied with distilled water alone. The collagen content was estimated in skin and tail of all the treated and control animals.
  
  
  RESULTS
  The content was significantly decreased in all the nano zinc oxide-treated groups with an inverse dose relationship.
  
  
  CONCLUSIONS
  The percentage collagen loss was high in skin when compared with tail. This may be due to the site of application where in the nano zinc oxide may be passed through skin due to their small size and may induce oxidative stress. Hence, we suggest that regulators and industry need to address the toxicity of nanomaterials with a realistic exposure assessment rather following conventional dose measurements following existing protocols.
authors.affiliation: International Institute of Biotechnology and Toxicology, Padappai, Tamil Nadu, India. santhoshmbt@gmail.com
authors.forename: P
authors.initials: P
authors.lastname: Surekha
authors.forename: A Sairam
authors.initials: AS
authors.lastname: Kishore
authors.forename: A
authors.initials: A
authors.lastname: Srinivas
authors.forename: G
authors.initials: G
authors.lastname: Selvam
authors.forename: A
authors.initials: A
authors.lastname: Goparaju
authors.forename: P Neelakanta
authors.initials: PN
authors.lastname: Reddy
authors.forename: P Balakrishna
authors.initials: PB
authors.lastname: Murthy
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D003094:Collagen / Q000378:metabolism; D005260:Female; D008297:Male; D053758:Nanoparticles / Q000008:administration & dosage / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000187:drug effects / Q000378:metabolism; D012869:Skin Absorption; D059551:Toxicity Tests, Subacute; D015034:Zinc Oxide / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D003094:Collagen; D015034:Zinc Oxide